FIELD OF THE INVENTION
[0001] The present invention generally relates to a horticultural lighting system, and more
particularly to an adaptive horticultural lighting system for use indoors.
BACKGROUND
[0002] Light emitting diodes (LEDs) have been utilized since about the 1960s. However, for
the first few decades of use, the relatively low light output and narrow range of
colored illumination limited the LED utilization role to specialized applications
(e.g., indicator lamps). As light output improved, LED utilization within other lighting
systems, such as within LED "EXIT" signs and LED traffic signals, began to increase.
Over the last several years, the white light output capacity of LEDs has more than
tripled, thereby allowing the LED to become the lighting solution of choice for a
wide range of lighting solutions.
[0003] LEDs exhibit significantly optimized characteristics, such as source efficacy, optical
control and extremely long operating life, which make them excellent choices for general
lighting applications. LED efficiencies, for example, may provide light output magnitudes
up to 200 lumens per watt of power. Energy savings may, therefore, be realized when
utilizing LED-based lighting systems as compared to the energy usage of, for example,
incandescent, halogen, compact fluorescent and high-intensity discharge (HID) lighting
systems. As per an example, an LED-based lighting fixture may utilize a small percentage
(e.g., 15-20%) of the power utilized by a halogen-based lighting system, but may still
produce an equivalent magnitude of light.
[0004] While HID lighting systems have been the predominant choice for conventional horticultural
lighting applications, LED technologies are gaining attraction due to their high luminous
efficacy and their ability to produce narrow-band spectral distributions. Current
LED-based horticultural lighting systems, however, fail to produce adequate light
uniformity for indoor horticulture facility applications where natural light is not
present nor do they produce adaptable spectral tuning. In addition, conventional LED-based
horticultural lighting systems produce light rays exhibiting decreased intensity with
increasing emission angle relative to the optical axis. Accordingly, none of the control
systems used to effect adequate light distribution characteristics, spectral tuning
and power efficiency are in existence either.
[0005] Efforts continue, therefore, to develop an LED lighting system and associated controls
that exceed the performance parameters of conventional horticultural lighting systems.
SUMMARY
[0006] To overcome limitations in the prior art, and to overcome other limitations that
will become apparent upon reading and understanding the present specification, various
embodiments of the present invention disclose methods and apparatus for the control
and production of LED-based lighting for indoor horticultural systems. Such systems
may produce specific light intensities using a time division multiple access current
sharing technique or may produce the same light intensities using direct current drive
to increase efficacy.
[0007] In accordance with one embodiment of the invention, a light fixture comprises a plurality
of LED channels coupled to a current node and configured to receive a current signal
from the current node and a processor coupled to each of the plurality of LED channels
and configured to allow each of the plurality of LED channels to receive the current
signal at mutually exclusive time slots within a time period during a first mode of
operation and configured to allow each of the plurality of LED channels to concurrently
receive the current signal during a second mode of operation.
[0008] In accordance with an alternate embodiment of the invention, a light fixture comprises
a plurality of LED channels coupled to a current node and configured to receive a
current signal from the current node and a processor coupled to each of the plurality
of LED channels and configured to allow a first mode of operation wherein each of
the plurality of LED channels receives the current signal at mutually exclusive time
slots within a time period and further configured to allow a second mode of operation
wherein a first number of the plurality of LED channels receives the current signal
at mutually exclusive time slots within a time period and a second number of the plurality
of LED channels concurrently receives the current signal during their respective mutually
exclusive time slots within the time period.
[0009] In accordance with an alternate embodiment of the invention, a light fixture comprises
a plurality of LED channels coupled to a current node and configured to receive a
current signal from the current node and a processor coupled to each of the plurality
of LED channels and configured to control a magnitude of the current signal and further
configured to allow each of the plurality of LED channels to receive the current signal
at mutually exclusive time slots within a time period during a first mode of operation
and further configured to allow each of the plurality of LED channels to concurrently
receive the current signal during a second mode of operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Various aspects and advantages of the invention will become apparent upon review
of the following detailed description and upon reference to the drawings in which:
FIG. 1 illustrates an LED-based horticultural light in accordance with one embodiment
of the present invention;
FIGs. 2A and 2B illustrate a lens array in accordance with one embodiment of the present
invention;
FIG. 3 illustrates a cross-section of an LED/lens pair in accordance with one embodiment
of the present invention;
FIGs. 4A and 4B illustrate an intensity distribution and shaded illuminance plot in
accordance with one embodiment of the present invention;
FIGs. 5A and 5B illustrate a conventional intensity distribution and shaded illuminance
plot resulting from a bare LED without a lens or an LED with a standard Lambertian
optic;
FIG. 6 illustrates a cross-section of an LED/lens pair in accordance with an alternate
embodiment of the present invention;
FIGs. 7A and 7B illustrate an intensity distribution and shaded illuminance plot in
accordance with an alternate embodiment of the present invention;
FIG. 8 illustrates a horticulture system in accordance with one embodiment of the
present invention;
FIG. 9 illustrates an LED-based horticultural light in accordance with an alternate
embodiment of the present invention;
FIG. 10 illustrates a block diagram of a power supply that may be used with the LED-based
horticultural light of FIG. 9;
FIG. 11 illustrates a lighting system in accordance with one embodiment of the present
invention;
FIG. 12 illustrates flow diagrams in accordance with several embodiments of the present
invention;
FIG. 13 illustrates a lighting system in accordance with an alternate embodiment of
the present invention;
FIG. 14 illustrates flow diagrams in accordance with several alternate embodiments
of the present invention;
FIGs. 15A, 15B, 15C, 15D and 15E illustrate timing diagrams in accordance with several
embodiments of the present invention;
FIG. 16 illustrates an indoor horticultural system in accordance with one embodiment
of the present invention;
FIG. 17 illustrates a schematic diagram that extracts power from a portion of an LED
string to implement an auxiliary function in accordance with one embodiment of the
present invention;
FIG. 18 illustrates an LED-based horticultural light in accordance with an alternate
embodiment of the present invention;
FIG. 19A illustrates internal portions of the LED-based horticultural light of FIG.
18;
FIGs. 19B-19C illustrate top and bottom orthographic views of the optical pucks of
the LED-based horticultural light of FIG. 18;
FIG. 20 illustrates light distributions from horticultural lighting fixtures that
do not include optical lenses in accordance with an alternate embodiment of the present
invention;
FIG. 21 illustrates cooling features of the LED-based horticultural lighting fixtures
in accordance with various embodiments of the present invention; and
FIG. 22 illustrates cooling features of the LED-based horticultural lighting fixtures
in accordance with various embodiments of the present invention.
DETAILED DESCRIPTION
[0011] Generally, the various embodiments of the present invention are applied to a light
emitting diode (LED) based lighting system that may contain an array of LEDs and an
array of associated lenses. The LED array may be mechanically and electrically mounted
to a PCB having control and bias circuitry that allows specific sets (e.g., channels
or strings) of LEDs to be illuminated on command. Any set of one or more LEDs may
be grouped into one or more channels, such that specific rows, columns or other arrangements
of LEDs in the LED array may be illuminated independently depending upon the specific
channel within which the LED or LEDs are grouped. A channel of LEDs may include non-linear
arrangements, such as square, circular, rectangular, zig-zag or star-shaped arrangements
to name only a few. An associated lens array may be mounted in proximity to the LED
array in such a way that the lens array may perform more than one function. For example,
the lens array may mechanically impose a uniform pressure onto the PCB against the
associated heat sink to optimize heat transfer from the PCB to the heat sink. Further,
the lens array may contain individual lenses with mechanical standoffs so as to maintain
an optimal separation distance between the LED and associated lens so that light rays
generated by each individual LED may be optically varied before projection onto a
target.
[0012] The mechanical standoffs may, for example, exhibit a shape (e.g., circular) having
a dimension (e.g., circumference) that is slightly larger than a dimension (e.g.,
a circumference) of the LED's footprint as mounted on its associated PCB. Accordingly,
as the lens array is pressed against the PCB, each mechanical standoff of each lens
of the lens array may impose a substantially uniform pressure along a circular perimeter
surrounding the LED to further enhance heat transfer from the LED to the heat sink.
[0013] Each lens of the lens array may, for example, be placed in such proximity to its
corresponding LED so as to collect substantially all of the light generated by its
associated LED and virtually none of the light generated by neighboring LEDs. Each
lens may optically vary (e.g., refract) the light distributed by its associated LED
into an optically varied light distribution, such that the light distributed by the
lens may exhibit a modified intensity distribution as compared to the intensity distribution
of light generated by a bare LED. In alternate embodiments, multiple LEDs may be associated
with a single lens such that the intensity of light generated by each of the multiple
LEDs may be modified by the single lens.
[0014] The Full Width Half Maximum (FWHM) beam angle may be defined as the beam angle where
the light distribution exhibits an intensity equal to half the peak intensity. A conventional
LED may exhibit an FWHM beam angle of about 120 degrees, where the peak intensity
of light distribution may exist at a zero-degree offset from the optical axis of the
LED (e.g., centerbeam). Each lens of the lens array may, however, modify the intensity
distribution, such that the FWHM beam angle may either be less than, or substantially
the same as, the FWHM beam angle produced by a bare LED, but the intensity distribution
may be modified by the lens such that the peak intensity may not exist at centerbeam,
but rather may be offset from centerbeam.
[0015] In one example, the intensity distribution of a bare LED may exhibit a relatively
wide FWHM beam angle (e.g., a 120-degree FWHM beam angle) having a peak intensity
at centerbeam. A lens of the lens array may, for example, be used to substantially
refract the FWHM beam angle of the bare LED between about 100 degrees and 140 degrees
(e.g., between approximately 115 degrees and 128 degrees), but may alter the intensity
distribution such that the peak intensity may not exist at centerbeam, but instead
may exist at an offset between about 40 and 60 degrees (e.g., between approximately
50 and 55 degrees) half angle from centerbeam.
[0016] As per another example, a lens of the lens array may be used to substantially reduce
the FWHM beam angle of the bare LED from about 120 degrees to between about 50 degrees
and 90 degrees (e.g., between approximately 65 degrees and 75 degrees) and may further
alter the intensity distribution such that the peak intensity may not exist at centerbeam,
but instead may exist at an offset between about 15 and 35 degrees (e.g., between
approximately 20 and 28 degrees) half angle from centerbeam.
[0017] Generally, each lens of the lens array may distribute light into a ray set that exhibits
varying intensity depending upon the angle that each light ray of the projected ray
set exhibits relative to a reference axis. For example, a reference axis of the LED
may be defined as the axis that is orthogonal to the surface of the PCB to which the
LED is mounted and each light ray emitted by the LED may be refracted by the lens
to exhibit an intensity that is proportional to the angle that the refracted light
ray forms with respect to the reference axis. In one embodiment, refracted light rays
at lower angles relative to the reference axis may exhibit lower intensities while
refracted light rays at higher angles relative to the reference axis may exhibit relatively
larger intensities.
[0018] Refracted light rays incident upon a target surface may similarly be defined with
respect to the reference axis. For example, light rays refracted by the lens that
exhibit a zero-degree offset from the reference axis may be described as exhibiting
a zero-degree incidence angle. Similarly, light rays refracted by the lens that exhibit
non-zero-degree offsets from the reference axis may be described as exhibiting incidence
angles greater than zero as measured relative to the reference axis.
[0019] A lens may be configured to refract light rays emitted by the LED to exhibit intensities
that are proportional to their respective incidence angles. For example, refracted
light rays with lower incidence angles may exhibit lower intensities as compared to
refracted light rays with higher incidence angles. The lens may be further configured
to substantially prohibit refraction of light rays exhibiting incidence angles greater
than a reference angle.
[0020] The lens, therefore, may produce lower intensity light rays having lower incidence
angles as compared to the intensity of light rays having relatively higher incidence
angles. Such a lens may be particularly useful when the beam is to be projected onto
a flat surface target with a substantially uniform illuminance across the entire illuminated
surface regardless of the angle of incidence, or when the beam is to be projected
onto a flat surface target with an increasing illuminance across the entire illuminated
surface as the angle of incidence increases. Such a lens may be further useful when
the beam is to be projected not only onto a flat surface below the light, but also
onto objects that are adjacent to the flat surface at higher incidence angles with
respect to the light.
[0021] Stated differently, since target illuminance is proportional to the intensity of
the projected light ray and inversely proportional to the square of the distance between
the target and the lens that is producing the projected light ray, a lens that produces
light rays having intensities that are proportional to the angle of incidence up to
a threshold angle may be used to produce substantially even or uniform illuminance
on a flat plane across the full beam width. That is to say in other words, that as
the angle of incidence of light rays projected by the lens increase, so does their
intensity. Furthermore, by increasing the intensity of the light rays in proportion
to the square of the distance between the lens and the target, a substantially even
target illuminance may be projected across the entire illuminated flat surface regardless
of the angle of incidence of light rays onto the target, or an illuminance may be
projected onto a flat surface that increases with the angle of incidence. Adjacent
targets may also be illuminated by light rays that do not illuminate the flat surface
due to their higher angles of incidence, but due to the higher intensity of such light
rays, may illuminate such adjacent targets with substantially equal illuminance, or
with substantially increasing illuminance, as compared to those light rays that are
incident on the flat surface.
[0022] It should be noted that the advantages obtained by using the horticultural lights
in accordance with the present invention do not exist with conventional horticultural
lights, which may include LED-based horticultural lights as well. For example, conventional
horticultural lights typically use a very small, yet high power light source with
a secondary reflector in order to obtain a particular distribution of light onto a
typical grow bed. Such a light source, however, produces non-reflected light rays
directly from the light source having increased intensity at centerbeam, which in
turn requires increased vertical distance between the horticultural light and the
canopy of plants below the horticultural light.
[0023] Alternately, smaller LED-based horticultural lights may be used, but are used in
very large numbers so as to obtain a projection area substantially equal to that of
the larger conventional horticultural lights. While reduced vertical distance between
the smaller LED-based horticultural lights and the plant canopy may be achieved, cross-lighting
becomes virtually non-existent and the amount of light projecting throughout the depth
of the plant canopy is significantly reduced.
[0024] Accordingly, even when a particular coverage area is achieved, the illuminance projected
onto the grow bed lacks uniformity and, therefore, includes "hot spots" and "dim spots"
and generally provides uneven projected illuminance due to the inverse square law
as discussed in more detail below. As discussed above, for example, conventional horticultural
lights generally project maximum intensity at zero to low angles of incidence, which
requires relatively large vertical distances to be established between the conventional
horticultural light and the underlying plant. As a result, vertical distances between
the conventional horticultural light and the corresponding plant must be maximized
to, for example, prevent plant burn.
[0025] Horticultural lights in accordance with the present invention, on the other hand,
utilize a dense array of lenses that optically vary the intensity of the light distributed
by an associated array of LEDs to project a uniform illuminance across a large surface
area of a flat plane, or to project an increasing illuminance as the angle of incidence
increases from centerbeam, despite the effects of the inverse square law (e.g., regardless
of the increased distances that the light travels to the target due to the increased
angles of incidence). Accordingly, not only may the light projection area from each
horticultural light fixture in accordance with the present invention be increased
as compared to conventional horticultural lights, but the illuminance within the illuminated
area may be made substantially uniform, or substantially increasing as incidence angles
increase from centerbeam outward, as well. In addition, the illuminance projected
onto secondary targets that are adjacent to the primary target may also be made to
be substantially uniform, or substantially increasing as incidence angles increase
from centerbeam outward, due to the increased intensity of light rays projected by
the horticultural light fixture at angles that are incident upon the secondary targets.
[0026] In other embodiments, horticultural lights in accordance with the present invention
may utilize other techniques, with or without optics, to vary light intensity. Variability
of the light output (e.g., spectral variability) may be controlled, for example, using
any number of wired protocols including 0-10V, I2C, digital multiplex (DMX), ethernet
or digital addressable lighting interface (DALI) to name only a few. In addition,
spectral variability may be achieved via wireless protocols, such as via ZigBee, Wi-Fi,
Bluetooth or a thread-based mesh network, along with other wireless protocols. Furthermore,
by combining broad-spectrum white LEDs with a combination of other LEDs may allow
the horticultural light to produce photosynthetically active radiation (PAR).
[0027] For example, two or more sets of broad-spectrum LEDs may be utilized along with one
or more sets of fixed-color LEDs (e.g., one set of blue LEDs and one set of red LEDs)
in order to implement broad-spectrum illumination that may better simulate sun light.
In addition, the two or more sets of broad-spectrum LEDs may exhibit different correlated
color temperatures (CCT), such that once varying intensities of the light generated
by both sets of broad-spectrum LEDs is mixed, a tunable CCT composite spectrum may
result that may better simulate the various phases of the sun, may better simulate
sunlight at the various latitudes that the sun may assume and may better simulate
sun light across each of the four seasons.
[0028] In addition, the intensities of multiple horticultural lighting fixtures may be controlled
within an indoor grow facility to better simulate the position of the sun throughout
the daylight hours. For example, by increasing the intensity of easterly-positioned
horticultural lighting fixtures in the morning hours may better simulate the rising
sun, by increasing the intensity of centrally-positioned horticultural lighting fixtures
during the mid-day hours may better simulate the mid-morning/mid-afternoon sun and
by increasing the intensity of westerly-positioned horticultural lighting fixtures
in the late afternoon/evening hours may better simulate the setting sun.
[0029] Horticultural lighting fixtures utilized within a greenhouse may also be utilized
to augment the light produced within the greenhouse. As an example, a sensor may measure
various aspects of light generated within the greenhouse and may provide the measurements
to a controller. The controller may then compare the measurements with light recipes
contained within a light prescription database to determine whether any deficiencies
exist within the greenhouse light (e.g., deficiencies in color spectrum, color temperature,
photosynthetic photon flux, etc.). If so, the controller may activate one or more
channels of LEDs within the light fixture to augment the greenhouse light, thereby
filling in deficiencies detected in the greenhouse light (e.g., increasing intensity
of a particular spectrum of light, increasing photosynthetic photon flux, varying
color temperature, etc.). If the light generated within the greenhouse already conforms
to a particular light recipe, on the other hand, then the controller may deactivate
the light fixtures altogether to save energy.
[0030] In one embodiment, each set of the multiple sets of LEDs may be arranged as independent
channels of LEDs, where each channel of LEDs may be independently operated at a selected
intensity based upon a magnitude of current that may be conducted by each channel
of LEDs. The control circuitry that may be used to select the magnitude of current
that may be conducted by each channel of LEDs may be integrated within the power supply
that may also contain the bulk power conversion (e.g., alternating current (AC) to
direct current (DC) and/or DC to DC power conversion electronics) and regulation (e.g.,
constant current regulation or constant voltage regulation) electronics.
[0031] Turning to FIG. 1, horticultural light 100 is exemplified, which may include one
or more lens arrays (e.g., lens array 118 and 126). Each lens array may include one
or more rows of lenses (e.g., four rows of lenses) and one or more columns of lenses
(e.g., 12 columns of lenses). One or more LEDs (not shown) may be included behind
each lens (e.g., lens 102) so that in one example, the number of LEDs included within
horticultural light 100 may be equal to the number of lenses included in each lens
array (e.g., 48 LEDs per lens array for a total of 96 LEDs per horticultural light
100). As per another example, multiple LEDs (e.g., one red, one green, one blue and
one white LED from each RGBW channel of LEDs) may be included behind each lens and
may further be rotated with respect to one another so as to smooth the light distribution
projected by each multiple LED/single lens combination. In one embodiment, for example,
each of 4 LEDs combined under a single lens may be attached to the underlying PCB
at 0 degree, 45 degree, 90 degree and 135 degree offsets, respectively, whereby the
magnitude of angle offset may be inversely proportional to the number of LEDs combined
under a single lens (e.g., 180 degrees/4 equals a rotation offset of 45 degrees from
one LED to the next).
[0032] Bezel 134 may, for example, provide a substantially constant pressure around a perimeter
of horticultural light 100 to, for example, seal a substantially transparent media
to horticultural light 100 thereby maintaining horticultural light 100 in a water
proof/water resistant state. The transparent media may also press the lens array against
the PCB behind the lens array, such that substantially 100% of the light generated
by each LED may be directed through its respective lens and through the transparent
media to prohibit virtually any of the light from being redirected back into horticultural
light 100. While the dimensions (e.g., 4.5 inches wide x 22 inches long) of horticultural
light 100 may be significantly smaller than conventional LED horticultural lights
(e.g., 4 feet wide x 4 feet long), horticultural light 100 via its dense array of
LEDs and associated lenses may nevertheless project a substantially equivalent amount
of light onto a conventional grow bed, but may do so with substantially uniform illuminance,
or substantially increasing illuminance from centerbeam outward, across the entire
grow bed and adjacent grow beds unlike the substantially non-uniform illuminance,
or substantially decreasing illuminance from centerbeam outward, as projected by conventional
horticultural lights.
[0033] Horticultural light 100 may further include control circuitry (e.g., controllers
110, 112, 114 and 116) and associated circuitry (e.g., bias circuitry 124) such that
any one or more LEDs (not shown) may be independently transitioned into conductive
and non-conductive states on command. Alternately, LED control and bias circuitry
(e.g., controllers 110, 112, 114, 116 and associated bias control circuitry 124) may
not be co-located on the same PCB to which the associated LEDs are mounted, but may
instead be located remotely to the PCB (e.g., on a modular control and bias circuit
that may be interchangeably introduced into horticultural light 100 or into a bias
and control bus that connects two or more horticultural lights 100 together).
[0034] In one embodiment, the conductive state of any multiple of LEDs (e.g., the LEDs,
not shown, behind each row of lenses 126, 128, 130 and 132) may be independently controlled.
In other embodiments, the conductive state of any multiple of LEDs (e.g., the LEDs,
not shown, behind each column of each array of lenses 118 and 126) may be independently
controlled. Once an LED (not shown) is transitioned to its conductive state, the associated
lens (e.g., lens 102) may produce a light distribution that may exhibit a particular
intensity profile, which may produce a substantially uniform target illuminance, or
a substantially increasing target illuminance from centerbeam to the edge of the beam
pattern, across a flat surface as discussed in more detail below.
[0035] Multiple horticultural lights 100 may be employed for use as horticultural lighting
in a greenhouse, small indoor grow room, or in a commercial production facility as
part of an integrated horticultural system. Horticultural light 100 may, for example,
replicate natural light that may be absent in an indoor grow facility and may be controlled
(e.g., via bias controller 124 and controllers 110, 112, 114 and 116) to deliver virtually
any wavelength of light that may be produced by an LED, at virtually any intensity,
at virtually any duty cycle that may be useful in a horticultural facility. Furthermore,
virtually any mixture of LEDs may be utilized within horticultural light 100 to produce
a wide range of color temperature, spectrum and color rendering index (CRI).
[0036] As an example, each channel of LEDs (e.g., rows of LEDs, not shown, behind rows of
lenses 126, 128, 130 and 132, respectively) may each include a selection of LEDs that
may produce a range of color temperature and CRI attributes. For example, the rows
of LEDs (not shown) behind lens rows 126 and 128 may include LEDs exhibiting a color
temperature of approximately 3000°K and a CRI greater than 90. As another example,
the row of LEDs (not shown) behind lens row 130 may include LEDs exhibiting a color
temperature of approximately between 5700°K and 6500°K and may exhibit a CRI less
than 80. As per another example, the row of LEDs (not shown) behind lens row 132 may
include LEDs exhibiting a narrow-bandwidth red color spectrum (e.g., at or below 1800°K
or between 580nm and 750nm). It should be noted that virtually any combination of
wavelength, color temperature, spectrum and CRI may be used to match the particular
photosynthetic and photomorphogenic requirements of the crop of interest.
[0037] It should be further noted that the LEDs (not shown) may include a percentage (e.g.,
75%) of phosphor converted white LEDs and a percentage (e.g., 25%) of narrow band
red or blue spectrum LEDs, such as aluminum gallium indium phosphide (AlGalnP) LEDs.
Alternately, for example, phosphor converted red LEDs may also be used, which may
facilitate the use of indium gallium nitride (InGaN) LEDs exclusively, both for the
phosphor converted white LEDs and the phosphor converted red LEDs. Such an arrangement
of matched InGaN LEDs may, for example, provide a very broad spectrum white light
with an emphasis on the blue and red spectra while also providing uniform thermal
performance and degradation as well as the advantage of facilitating the implementation
of strings of multiple LEDs (e.g., the string of LEDs, not shown, behind lens rows
126, 128, 130 and 132) that may be arranged serially with a substantially constant
forward voltage.
[0038] As discussed in more detail below, bias controller 124 may include wired and/or wireless
access control systems, such as Bluetooth, Wi-Fi, thread-based mesh, digital multiplex
(DMX), I2C, ethernet or telecommunications-based control systems that may allow horticultural
light 100 to be controlled remotely, either within the same facility, or via a regional
or national control room. Accordingly, the lighting of one or more unmanned horticultural
facilities may be centrally controlled by a single control station. Such a control
station, for example, may also control other aspects of the horticultural facility.
Air filtration and circulation systems, for example, may require remote access control
for heat and exhaust mitigation. Various irrigation systems, such as drip irrigation,
hydroponic flood benches and trough benches along with a nutrient management system
may also be controlled by the control station. In general, the control station may
not only control the one or more horticultural lights 100 of the horticultural facility,
but also the nutrients, air circulation, irrigation, dehumidification, carbon dioxide
(CO
2) injection and other facilities that may be required to maintain the exact environment
needed by the various growing rooms, cloning rooms and flowering rooms of the horticultural
facility.
[0039] Turning to FIGs. 2A and 2B, a front view and a rear view, respectively, of a lens
array (e.g., lens array 118 of FIG. 1) are exemplified. Mechanical portions 202 and
204, for example, of the lens array may not include any optical attributes, but may
instead provide a framework within which optical portions (e.g., lenses 206) may be
configured into an array (e.g., multiple rows and columns of lenses 206). Mechanical
portions 202 and 204 may, for example, include mounting features (e.g., apertures
208) that may facilitate the insertion of mounting hardware (e.g., screws) that may
be used to mount the lens array to the underlying PCB and lighting fixture housing/heat
sink (not shown). By utilizing such mounting hardware, mechanical portion 204 may
be pressed against the underlying PCB and LEDs (not shown), which may in turn press
the underlying PCB against the housing/heat sink (not shown) of the horticultural
light (e.g., horticultural light 100) so as to promote effective conduction of heat
away from the LEDs.
[0040] Mechanical portion 204 may further include raised portions 210 that may be used to
create an optimal separation distance between the lens array and the underlying LED
array (not shown). Indented portions 212 may, for example, accommodate the insertion
of at least a portion of an LED package (e.g., the dome portion of an LED package).
The height of raised portions 210 may be selected to create an optimal separation
distance between the optical input portion of the lens (e.g., lens 206) and the associated
LED (not shown) that is inserted into the corresponding indented portion 212 of lens
206 as discussed in more detail below. Raised portions 210 may exhibit a particular
geometric shape (e.g., circular) so as to match a particular foot print of each LED
(not shown) of the LED array. As such, raised portions 210 may impose a substantially
uniform pressure surrounding, and in close proximity to, each associated LED (not
shown) so as to create a uniform conduction path so that heat may be conducted away
from the LED through the associated PCB and heat sink, thereby improving the performance
of the LED.
[0041] In one embodiment, the array of lenses 206 may be arranged as an array of rows and
columns of lenses, where each lens may exhibit a circular shape having a diameter
(e.g., 13 mm diameter) and a separation distance from each neighboring lens (e.g.,
a separation distance of 16 mm center to center). The composition of the array of
lenses 206 may be that of an optical grade polymer (e.g., acrylic) that may exhibit
an index of refraction of between about 1.48 and 1.5 (e.g., approximately 1.491) or
that of an optical grade polycarbonate that may exhibit an index of refraction of
between about 1.5 and 1.7 (e.g., approximately 1.58).
[0042] Turning to FIG. 3, a cross-sectional view is exemplified in which LED package 306,
having hemispherical dome portion 312, may protrude into indented portion 304 of lens
314. It should be noted that indented portion 304 may exemplify a cross-section of
a lens array (e.g., a cross-section of indented portion 212 of the lens array of FIG.
2) where indented portion 304 may include optical input 308 to lens 314 that may accept
the light distribution from LED package 306 into lens 314. Protrusion 302 may exemplify
a cross-section of a lens array (e.g., a cross-section of mechanical portion 210 of
the lens array of FIG. 2) where protrusion 302 includes surface area 316 that may
be in communication with a PCB (not shown) to select an optimal separation distance
(e.g., separation distance 318) between the LED deck (e.g., PCB 326 of LED package
306) and optical input 308 to lens 314. In one embodiment, separation distance 318
may be between about 0.3mm and about 0.4mm (e.g., approximately 0.35mm).
[0043] Portion 310 may exemplify a cross-section of a lens array (e.g., a cross-section
of lens 206 of FIG. 2) where portion 310 may be the optical output of lens 314 that
produces the optically varied (e.g., refracted) light distribution. Light distribution
from lens 314 may exhibit an optical axis (e.g., axis 320) that may be orthogonal
to the mounting surface of the PCB (not shown) to which LED package 306 is mounted.
In addition, the projected light distribution from lens 314 may be described in terms
of the intensity of each ray and its geometric orientation with respect to axis 320
as well as the projected illuminance onto a flat plane and projected illuminance onto
targets adjacent to the flat plane.
[0044] It should be noted that the lens array is configured such that a projected light
distribution from an individual lens (e.g., lens 314) of the lens array may not be
incident upon adjacent lenses (e.g., lenses 326 and 328) of the lens array. In one
embodiment, for example, lens 314 may refract the light distribution of LED 306 into
a half-beam angle between about 50 degrees and 90 degrees (e.g., between approximately
65 degrees and 75 degrees) having full-beam width 322 that is not incident on any
adjacent lenses (e.g., lenses 326 and 328).
[0045] Turning to FIG. 4A, a light distribution is exemplified that may be produced by an
LED/lens combination in accordance with one embodiment that may include an LED (e.g.,
LED package 306 of FIG. 3) and a lens (e.g., lens 314 of FIG. 3) to produce a light
distribution as exemplified in FIG. 4A. As illustrated, for example, the light distribution
from lens 314 may exhibit a center beam intensity (e.g., about 77 candela) at a zero-degree
offset from the optical axis (e.g., axis 320 of FIG. 3). The light distribution from
lens 314 may exhibit a peak intensity (e.g., 84 candela) offset from the center beam
by an angle of about 22.5 degrees to about 27.5 degrees.
[0046] It can be seen, therefore, that if the light distribution of FIG. 4A is projected
onto a target having a flat surface by a lens (e.g., lens 314 of FIG. 3), the distance
between the lens and the target changes depending upon the angle of incidence of the
light distribution onto the target. As an example, if the angle subtended by a light
ray is offset from the optical axis (e.g., axis 320 of FIG. 3) by zero degrees, then
the distance traveled by the light ray to the target is at its minimal value. As the
angle subtended by a light ray referenced to the optical axis increases, so does the
distance that the light ray must travel before being incident onto the target's surface.
[0047] According to the inverse square law, therefore, the target illuminance decreases
in proportion to the inverse square of the distance between the lens and the target,
thereby causing the target illuminance to decrease with increasing beam width. However,
since the intensity of the light distribution of FIG. 4A increases with increasing
beam angle up to a reference beam angle (e.g., between about 22.5 degrees to about
27.5 degrees), the target illuminance may nevertheless remain substantially uniform,
or may substantially increase with increasing beam angle, despite the effects of the
inverse square law as exemplified, for example, in the associated shaded illuminance
plot of FIG. 4B. In addition, for example, since the intensity of light distribution
is maximum at maximum beam angle, the effective distance of the illuminance onto targets
adjacent to the main target may be extended, such as may be the case when projecting
light through side portions of the canopies of adjacent plants.
[0048] As a comparison, FIG. 5A exemplifies an intensity distribution from a bare LED (e.g.,
an LED without an optically varied distribution found on conventional horticultural
lights) and FIG. 5B exemplifies the associated shaded illuminance plot. As can be
seen from FIG. 5A, the intensity peaks at centerbeam (e.g., zero-degree offset from
the LED's optical axis) and then decreases with increasing beam angle, which causes
the illuminance, as exemplified by the shaded illuminance plot of FIG. 5B, to be non-uniform
and decreasing in proportion to the inverse of the square of the increasing distance
between the LED and its illumination target. It can be seen, therefore, that without
the optical distribution of a lens in accordance with the various embodiments of the
present invention, uniform illuminance onto a flat target is not possible. Rather,
decreasing illuminance with increasing angles of incidence is produced.
[0049] Turning to FIG. 6, a cross-sectional view of an alternate LED/lens embodiment exhibiting
a wider beam angle is exemplified in which LED package 606, having hemispherical dome
portion 612, may protrude into indented portion 604 of lens 614. It should be noted
that indented portion 604 may exemplify a cross-section of a lens array (e.g., a cross-section
of indented portion 212 of the lens array of FIG. 2) where indented portion 604 includes
optical input 608 to lens 614 that accepts the light distribution from LED 606 into
lens 614. Protrusion 602 may exemplify a cross-section of a lens array (e.g., a cross-section
of mechanical portion 210 of the lens array of FIG. 2) where protrusion 602 includes
surface area 616 that may be in communication with a PCB (not shown) to select an
optimal separation distance (e.g., separation distance 618) between the LED deck (e.g.,
PCB 626 of LED package 606) and optical input 608 to lens 614. In one embodiment,
separation distance 618 may be between about 0.3mm and about 0.4mm (e.g., approximately
0.35mm).
[0050] Portion 610 may exemplify a cross-section of a lens array (e.g., a cross-section
of lens 206 of FIG. 2) where portion 610 may be the optical output of lens 614 that
produces the optically varied (e.g., refracted) light distribution. Light distribution
from lens 614 may exhibit an optical axis (e.g., axis 620) that may be orthogonal
to the mounting surface of the PCB (not shown) to which LED package 606 is mounted.
In addition, the projected light distribution from lens 614 may be described in terms
of the intensity of each ray and its geometric orientation with respect to axis 620
as well as the projected illuminance onto a flat plane and the projected illuminance
onto targets adjacent to the flat plane.
[0051] It should be noted that the lens array is configured such that a projected light
distribution from an individual lens (e.g., lens 614) of the lens array may not be
incident upon adjacent lenses (e.g., lenses 626 and 628) of the lens array. In one
embodiment, for example, lens 614 may refract the light distribution of LED 606 into
a beam angle between about 100 degrees and 140 degrees (e.g., between approximately
115 degrees and 128 degrees) having beam width 624 that is not incident on adjacent
lenses 626 and 628.
[0052] Turning to FIG. 7A, a light distribution is exemplified that may be produced by an
LED/lens combination in accordance with an alternate embodiment that may include an
LED (e.g., LED package 606 of FIG. 6) and a lens (e.g., lens 614 of FIG. 6) to produce
a light distribution as exemplified in FIG. 7A. As illustrated, for example, the light
distribution from lens 614 may exhibit a center beam intensity (e.g., about 20 candela)
at a zero-degree offset from the optical axis (e.g., axis 620 of FIG. 6). The light
distribution from lens 614 may exhibit a peak intensity (e.g., 59 candela) offset
from the center beam by an angle of about 50 degrees to about 55 degrees (e.g., approximately
54 degrees).
[0053] It can be seen, therefore, that if the light distribution of FIG. 7A is projected
onto a target having a flat surface by a lens (e.g., lens 614 of FIG. 6), the distance
between the lens and the target changes depending upon the angle of incidence of the
light distribution onto the target. As an example, if the angle subtended by a light
ray is offset from the optical axis (e.g., axis 620 of FIG. 6) by zero degrees, then
the distance traveled by the light ray to the target is at its minimal value. As the
angle subtended by a light ray referenced to the optical axis increases, so does the
distance that the light ray must travel before being incident onto the target's surface.
[0054] According to the inverse square law, therefore, the target illuminance decreases
in proportion to the inverse square of the distance between the lens and the target,
thereby causing the target illuminance to decrease with increasing beam width. However,
since the intensity of the light distribution of FIG. 7A increases with increasing
beam angle up to a reference beam angle (e.g., about 54 degrees), the target illuminance
may nevertheless remain substantially uniform, or may substantially increase with
increasing beam angle, despite the effects of the inverse square law as exemplified,
for example, in the associated shaded illuminance plot of FIG. 7B. In addition, for
example, since the intensity of light distribution is maximum at maximum beam angle,
the effective distance of the illuminance onto targets adjacent to the main target
may be extended, such as may be the case when projecting light through side portions
of the canopies of adjacent plants.
[0055] In comparing the intensity distribution plots of FIGs. 4A and 7A, it can be seen
that lens 314 of FIG. 3 produces a greater peak intensity than the peak intensity
produced by lens 614 of FIG. 6. Furthermore, since the beam angle produced by lens
614 of FIG. 6 is wider than that produced by lens 314 of FIG. 3, the area illuminated
by lens 614 may be greater than the area illuminated by lens 314, but the illuminance
produced by lens 614 may be less than that produced by lens 314 given the same distance
to target. Accordingly, while the number of horticultural lights (e.g., horticultural
lights 100 of FIG. 1) utilizing lens 614 needed to illuminate a given target area
may be less than the number of horticultural lights utilizing lens 314 needed to illuminate
the same target area, horticultural lights utilizing lens 614 may be mounted closer
to the target area to achieve the same illuminance generated by horticultural lights
utilizing lens 314 that are mounted further away from the target area. Accordingly,
less vertical distance between the horticultural light and the associated grow bed
may be needed when utilizing lens 614, thereby allowing multiple levels of grow beds
to be established floor to ceiling within the indoor horticultural facility.
[0056] Turning to FIG. 8, horticultural system 800 is exemplified including horticulture
light 804, which may include a lens array (e.g., lens array 118 and 126 as exemplified
by horticulture light 100 of FIG. 1). In alternate embodiments, horticulture light
804 may not include a lens array, or may use a different lens array layout. In addition,
horticultural system 800 may include grow beds 808, 808A and 808B that may be used
to cultivate virtually any crop that may be grown within a horticulture facility (e.g.,
a greenhouse). Horticultural lighting system 800 may further include, for example,
quantum sensor 806, which may include a photosynthetically active radiation (PAR)
sensor having a uniform sensitivity to PAR light, a light meter to measure instantaneous
light intensity and/or a data logger to measure cumulative light intensity. Quantum
sensor 806 may, for example, provide spectrographic data, which may include correlated
color temperature (CCT), CRI, chromaticity and photosynthetic photon flux (PPF) associated
with horticulture light 804 and any ambient light that may be incident upon quantum
sensor 806 (e.g., ambient light 830 as may be provided within a greenhouse that may
be incident upon grow beds 808, 808A and 808B) among other spectrographic data.
[0057] In one embodiment, controller 802 may access a database (e.g., light prescription
database 814), which may include predetermined light prescriptions for controlling
the light output from horticulture light 804 and may then utilize interface 810 to
tune horticulture light 804 in accordance with the predetermined light prescriptions
(e.g., prescribed light intensity, CCT, PPF and color spectrum). Controller 802 and
interface 810 may, for example, be used by an operator to either manually tune horticulture
light 804 to manual settings or tune horticulture light 804 to predetermined light
prescriptions 814. Alternately, controller 802 may automatically update horticulture
light 804 based upon comparisons between quantum sensor measurements 812 and light
prescriptions 814 using closed-loop feedback control so as to maintain horticulture
light 804 within operational constraints as defined by light prescriptions 814. For
example, the temperature of horticulture light 804 may increase, thereby increasing
the temperature of the LEDs contained within horticulture light 804, which may in
turn decrease an intensity of light generated by horticulture light 804. As a result
of closed-loop feedback, the decreased intensity due to increased temperature may
be detected by quantum sensor 806 and reported to controller 802, whereby controller
802 may responsively increase the intensity of the light distributed by horticulture
light 804. Conversely, as discussed in more detail below, controller 802 may instead
invoke other measures (e.g., increased air flow), which may then lower the temperature
of horticulture light 804, thereby resulting in an increased intensity light distribution.
[0058] As per another example, quantum sensor 806 may detect ambient light (e.g., ambient
light 830 provided within a greenhouse) in addition to the light that may or may not
be generated by horticulture light 804. In such an instance, controller 802 may automatically
update horticulture light 804 (e.g., control the PPF and/or intensity of light generated
across the PAR spectrum) based upon comparisons between quantum sensor measurements
812 and light prescriptions 814 using closed-loop feedback control so as to maintain
horticulture light 804 within operational constraints as defined by light prescriptions
814.
[0059] In one embodiment, for example, light prescriptions 814 may define a particular PPF
that may be necessary to achieve an optimal electron transport rate (ETR) within a
plant (e.g., plants contained within grow beds 808, 808A and 808B), which may be dependent
upon the particular species of plant being grown within grow beds 808, 808A and 808B.
An optimal ETR, for example, may be achieved at lower levels of PPF for one plant
species, while higher levels of PPF may be required to achieve an optimal ETR for
another species of plant. The efficiency of the conversion of the energy of photons
into electron transport may, for example, be proportional to the exponential expression,
a(1-e
-bPPF), where the constants "a" and "b" may be plant species dependent and "PPF" may be
the photosynthetic proton flux measured in micro-moles per square meter per second
(e.g., as measured by quantum sensor 806). Such an exponential expression may be provided
within light prescriptions 814 and may be utilized by controller 802 to constrain
an aspect of horticulture light 804 (e.g., light intensity) so that the PPF received
by the plant may result in optimized ETR.
[0060] In one example, the PPF received by a plant located within a greenhouse may already
be sufficient, which may result in the deactivation of horticulture light 804 by controller
802. Conversely, the PPF received by a plant located within a greenhouse may not be
sufficient, which may result in the activation of one or more channels of LEDs contained
within horticulture light 804 to generate the PPF required. Accordingly, for example,
controller 802 may vary the intensity of light generated by the one or more channels
of LEDs contained within horticulture light 804 between 0% and 100% intensity in response
to measurements 812 taken by quantum sensor 806 to generate the PPF required for optimal
ETR as dictated by light prescriptions 814.
[0061] Additionally, plants may require the transfer of a threshold number of micro-moles
of electrons per meter per day to optimize growth. Accordingly, quantum sensor 806
may record a cumulative number of micro-moles of photons received (e.g., from horticulture
light 804 and the ambient light produced by the greenhouse within which the plant
is housed) on a hourly/daily basis and may forward the measurements to controller
802 for comparison to a variable contained within light prescriptions 814. Based on
the comparison, controller 802 may vary an aspect of light generated by horticulture
light 804 (e.g., intensity variation between 0% and 100%) so that the plant may receive
a proper number of micro-moles of photons per meter per day to achieve optimized ETR
for optimized growth.
[0062] In an alternate embodiment, for example, light prescriptions 814 may define a particular
color spectrum and intensity of light distributed within the color spectrum that may
be necessary for optimal growth of plants contained within grow beds 808, 808A and
808B. Controller 802 may compare measurements 812 with light prescriptions 814 to
determine whether measurements 812 conform to a particular color spectrum recipe (e.g.,
whether ambient light generated within the greenhouse without the use of horticulture
light 804 is sufficiently matched to the color spectrum recipe). If not, controller
802 may tune the spectrum generated by horticulture light 804 as discussed herein
to augment the spectral gaps contained within the ambient light generated within the
greenhouse. If, on the other hand, the ambient light already conforms to the color
spectrum recipe, then controller 802 may instead deactivate horticulture light 804
to, for example, save energy.
[0063] Controller 802 may provide command and control signals to horticulture light 804
via interface 810 (e.g., via a wired protocol such as 0-10V, 12C, DALI or DMX, or
via a wireless protocol, such as ZigBee, Wi-Fi, thread-based mesh network or Bluetooth).
Controller 802 may receive all measurement data from quantum sensor 806 and may provide
such results via human-machine interface (HMI) 816 to an operator of horticultural
system 800 so that the operator may ascertain the performance characteristics of horticulture
light 804. It should be noted that HMI 816 may either be located within the same facility
as controller 802, or may be located remotely within a regional or national control
room, so that multiple controllers 802 in multiple grow facilities may be centrally
managed remotely.
[0064] As discussed above in relation to FIG. 1, horticulture light 804 may implement multiple
arrays of LEDs, whereby each LED array may be arranged into channels (e.g., along
rows and/or columns) and each channel of LEDs may be controlled separately and independently.
In one embodiment, horticulture light 804 (e.g., as discussed above in relation to
horticulture light 100 of FIG. 1) may implement multiple channels (e.g., 4 channels)
whereby each row of LEDs (e.g., rows 126, 128, 130 and 132 of FIG. 1) may represent
a separately and independently controllable LED channel.
[0065] Horticulture light 804 may be utilized to produce broad-spectrum white light (e.g.,
between about 420 nm and about 750 nm) with variable CCT so that the light spectrum
may be tuned to better simulate various aspects of sun light. For example, multiple
phases of the sun, simulation of sun light in all four seasons (e.g., fall, winter,
spring, summer) and latitude of the sun may be better simulated using CCT control.
Furthermore, no matter what CCT value may be selected, the intensity of light produced
may be selectable as well, such that in one example, multiple CCT values may be obtained
while maintaining a constant intensity.
[0066] As discussed above, horticultural light 804 may include appropriate lens/LED combinations
to provide illuminance 818, where illuminance 818 may be substantially uniform or
may substantially increase as the angle of incidence increases with respect to optical
axis 824. In addition, through increased intensity at increased beam angles as compared
to optical axis 824, light rays 820 and 822 may illuminate adjacent grow beds 808A
and 808B, respectively, with increased illuminance from the sides of the respective
grow beds to better simulate light received from the sun. Stated differently, by increasing
the intensity at increasing angles of incidence as compared to optical axis 824, light
generated by horticulture light 804 may not only be effective as to grow bed 808,
but also to grow beds 808A and 808B even though grow beds 808A and 808B are further
away from horticulture light 804 as compared to grow bed 808.
[0067] In one embodiment, horticulture light 804 may include multiple channels (e.g., two
rows) of broad-spectrum white LEDs, whereby the intensity of each row of LEDs may
be controlled by a separate channel (e.g., 1 of N channels 810) of controller 802.
The first set of broad-spectrum white LEDs may, for example, exhibit a first CCT (e.g.,
a CCT equal to about 2700K) and the second set of broad-spectrum white LEDs may exhibit
a second CCT (e.g., a CCT equal to about 5700K). Through operation of controller 802,
the intensity of each set of broad-spectrum white LEDs may be controlled to create
an averaged mix of light exhibiting a CCT between about 2700K and 5700K as may be
required (e.g., as required by light prescription 814). Alternately, each channel
of broad-spectrum white LEDs may include mixed CCT values (e.g., both 2700K and 5700K).
[0068] In alternate embodiments, the number of channels of broad-spectrum white LEDs may,
for example, be increased (e.g., increased to 3 channels) each channel exhibiting
a different CCT value (e.g., 2700K, 4000K and 6000K). In such an instance, the averaged
CCT value of the 3-channel combination may be variable between about 2700K and 6000K,
but with an emphasis of mid-range energy due to the addition of the 3
rd channel (e.g., the 4000K channel) of broad-spectrum white LEDs. Alternately, each
channel of broad-spectrum white LEDs may include mixed CCT values (e.g., all three
of 2700K, 4000K and 5700K).
[0069] In yet other embodiments, horticulture light 804 may include one or more channels
of fixed color LEDs (e.g., one channel of red LEDs and/or one channel of blue LEDs)
in addition to one or more channels of broad-spectrum white LEDs. In such an instance,
even wider ranging mixed CCT values may be obtained, since the averaged CCT values
produced by the broad-spectrum white LEDs may be pushed to lower values (e.g., through
the use of the variable intensity red channel) and/or pushed to higher values (e.g.,
through the use of the variable intensity blue channel).
[0070] Even broader spectrums may be achieved, for example, when the one or more channels
of fixed color LEDs may themselves be implemented using multiple wavelengths. For
example, a channel of red LEDs may be implemented through use of a first proportion
of red LEDs (e.g., 50% of the red LEDs producing light with a 660 nm wavelength) and
a second proportion of red LEDs (e.g., 50% of the red LEDs producing light with a
625 nm wavelength). Additionally, a channel of blue LEDs may be implemented through
use of a first proportion of blue LEDs (e.g., 50% of the blue LEDs producing light
with a 440 nm wavelength) and a second proportion of blue LEDs (e.g., 50% of the blue
LEDs producing light with a 460 nm wavelength). Accordingly, even broader spectrum
red and blue channels may be combined with broad-spectrum white channels to create
the broadest spectrum light possible all while also providing variable CCT.
[0071] Turning to FIG. 9, an alternate embodiment of horticulture light 900 is exemplified,
in which substantially none of the bias and control circuitry that may be associated
with each channel of LEDs is co-located on the same PCB as each LED. Instead, the
bias and control circuitry for each channel of LEDs (e.g., 4 channels 810 of FIG.
8) may be integrated within the bulk power conversion (e.g., power supply 904) that
may be mounted to horticulture light 900. In addition, power supply 904 may convert
the AC voltage (e.g., 110 VAC at 60 Hz applied via power cord 902) to a wide ranging
DC potential between approximately 10 VDC and 300 VDC (e.g., approximately between
about 12 VDC and 48 VDC). Buck, boost and/or buck/boost converters (not shown) also
contained within power supply 904 may form at least a portion of the bias and control
circuitry that may be required to illuminate each channel of LEDs contained within
horticulture light 900 at specified intensities as may be selected via a wired or
wireless control interface (e.g., a wired DMX interface).
[0072] Horticulture light 900 may exhibit a longer length profile as compared, for example,
to horticulture light 100 of FIG. 1. For example, a longer profile may be obtained
by concatenating two horticulture lights 910 and 912 (e.g., two horticulture lights
100 of FIG. 1 end to end for twice the length). It should be noted that the circuitry
of controller areas (e.g., areas 908) that may otherwise exist within other horticulture
lights (e.g., horticulture light 100 of FIG. 1) may instead be contained within power
supply 904.
[0073] Turning to FIG. 10, a block diagram of power supply 904 of FIG. 9 is illustrated,
which may include AC/DC bulk conversion block 1002 to bulk convert an alternating
current (AC) input to a direct current (DC) voltage, power management block 1004 to
provide operational power for miscellaneous devices (e.g., CPU 1018 and DMX 1010)
and one or more DC-DC converters (e.g., buck, boost and/or buck/boost converters 1006-1008)
to, for example, provide sufficient power to vary the intensity of the one or more
arrays of LEDs contained within the horticulture light (e.g., horticulture light 900
of FIG. 9).
[0074] In one embodiment, for example, converters 1006-1008 may generate a voltage substantially
equal to the forward voltage of their respective LED arrays and may vary the drive
current according to a constant current topology to achieve a desired intensity of
each LED array (e.g., as may be determined by light prescription 814 or HMI 816 of
FIG. 8). The desired intensity of each LED array may, for example, be controlled via
DMX 1010 and/or I2C 1020, where each LED array may exist within the same DMX universe
and may be responsive to an 8-bit intensity control word received within its designated
DMX slot. DMX 1010 may facilitate remote device management (RDM) data handling, whereby
full duplex communications may be accommodated to, for example, define DMX slot numbers
and to correlate those DMX slot numbers to each of the respective LED arrays.
[0075] Firmware executed by CPU 1018 may reside, for example, within memory (e.g., flash
memory), which may be local to CPU 1018 or remotely located with respect to CPU 1018.
Firmware may, for example, be changed or updated (e.g., boot loaded) via universal
serial bus (USB) 1012 (e.g., USB port 906 of FIG. 9). Such firmware may control, for
example, power management to the LED arrays as provided by converters 1006-1008. In
one embodiment, for example, firmware executed by CPU 1018 may operate DC-DC converters
1006-1008 according to a fixed-frequency, constant current topology that may select
a minimum and a maximum current to be conducted by each LED array through analog control.
Furthermore, firmware executed by CPU 1018 may operate DC-DC converters 1006-1008
(e.g., via pulse width modulated (PWM) control signals) to select any number (e.g.,
255) of intensity levels that may be generated by each LED array at any current setting.
In one example, current magnitudes between 1% and 25% of the maximum current magnitude
may be PWM modulated so as to provide precision dimming at the lowest levels of dimming
(e.g., 255 levels of dimming may be implemented via PWM modulation to achieve approximately
0.1% dimming granularity between 1% and 25% of maximum current).
[0076] Firmware executed by CPU 1018 may, for example, receive telemetry data (e.g., thermal
data via temperature sensors 1016) relative to, for example, the operating temperature
of the horticulture light (e.g., horticulture light 900 of FIG. 9). In response, CPU
1018 may issue fan control signals (e.g., fan RPM control signals) to fan 1014 so
as to maintain horticulture light 900 within a specified temperature range. In addition,
CPU 1018 may limit the maximum current conducted by each LED array as discussed above
to maintain the operating temperature of horticulture light 900 below a maximum temperature
range. For example, if the maximum temperature range is exceeded by horticulture light
900, CPU 1018 may first increase the speed at which one or more fans 1014 may be operating,
thereby providing increased air flow to horticulture light 900 in an effort to lower
the operating temperature of horticulture light 900 below its maximum operating temperature.
If the operating temperature is not reduced below the maximum temperature range, then
CPU 1018 may decrease the magnitude of current conducted by each LED array in a linear
rollback fashion until the operating temperature is reduced below the maximum temperature
range. As discussed above in relation to FIG. 8, for example, CPU 1018 may be operating
in response to quantum sensor input data (e.g., quantum sensor input data that may
be received via I2C interface 1020), whereby intensity variations of light measured
by the quantum sensor may be compared to light prescriptions contained within a database
and through closed-loop feedback, CPU 1018 may counteract such intensity variations
any number of ways. For example, an amount of current generated by DC-DC converters
1006-1008 may be changed to effect an intensity variation in the LED arrays. Alternately,
for example, adjusting the speed by which fan 1014 is spinning may control the temperature
of the one or more LED arrays, which may then effectuate a change in intensity of
light generated by the LED arrays, since light intensity generated by the LED arrays
may be inversely proportional to the temperature of the LED arrays.
[0077] As discussed above, firmware received via USB 1012 may be used to control certain
parameters of operation of horticulture light 900 via a computer (not shown) that
may be communicating with USB 1012. For example, any number of DC-DC converters 1006-1008
may be activated depending upon the number of LED arrays or channels that may exist
within horticulture light 900. For example, if eight DC-DC converters exist within
power supply 904, but only four LED arrays or channels exist within a particular horticulture
light, then half of the DC-DC converters may be activated for operation via firmware
loaded via USB 1012 while the other half remain in a deactivated state. In operation,
each activated DC-DC converter may receive a unique DMX address, such that DMX control
words may be correctly addressed to the corresponding DC-DC converter to correctly
control the intensity of the associated LED array.
[0078] In addition, firmware loaded via USB 1012 may be used to select the temperature trigger
value, such that either fan RPM may be increased or LED array current drive may be
decreased (as discussed above) once the temperature trigger value (e.g., as detected
by temperature sensors 1016) is exceeded. Dim control may also be selected via firmware
loaded via USB 1012 to, for example, select the rate at which the LED array(s) may
be dimmed. For example, each DMX control word (e.g., 256 control words per DMX slot
total) may correspond to a particular LED array intensity as may be controlled by
a corresponding PWM signal as generated by CPU 1018. User controllable dimming as
defined by firmware loaded via USB 1012 may, for example, be used to select the rate
at which such intensity variation occurs.
[0079] Turning to FIG. 11, a schematic diagram of lighting system 1100 is illustrated, which
may include AC/DC converter 1102 (e.g., power supply 904 of FIG. 9), which may include
one or more constant current and/or constant voltage DC output stages (e.g., DC stages
1110, 1112 and/or 1140) and an auxiliary low voltage output (e.g., 5VDC not shown)
with which components (e.g., processor 1104, wireless node 1106 and wired node 1108
of lighting system 1100) may derive their operational power. Any one or more of DC
output stages 1110, 1112 and 1140 may provide power via any one or more switched-mode
conversion techniques (e.g., buck, boost, buck/boost or flyback). Conversely, linear
power conversion techniques may also be utilized that obviate the need for switched-mode
conversion and may provide low electromagnetic emissions and excellent transient response.
[0080] AC/DC converter 1102 may be configured to provide sufficient power to, for example,
vary the intensity of the one or more arrays of LEDs contained within one or more
horticulture lights (e.g., one or more horticulture lights as exemplified in FIG.
9). It should be noted that while only two LED arrays 1122 and 1124 are exemplified,
any number of LED arrays 1138 and associated bias control circuitry may be accommodated
by any number of DC stages within AC/DC converter 1102. Furthermore, each LED array
1122 and 1124 may include virtually any number (e.g., one or more) of LEDs 1144 and
1146, respectively.
[0081] As discussed in more detail below, the magnitude of DC voltage available from any
one DC stage 1110, 1112 or 1140 may be adjusted as needed (e.g., via control 1148
from processor 1104) to be substantially equal to the combined forward voltage of
any one associated LED string 1122, 1124 or 1138. In one embodiment, for example,
processor 1104 may empirically deduce the magnitude of forward voltage required to
forward bias each LED in each string LED string 1122, 1124 and/or 1138. Once the magnitude
of forward voltage needed to forward bias each LED in each LED string 1122, 1124 and/or
1138 is known, processor 1104 may then command one or more associated DC stages 1110,
1112 and/or 1140 (e.g., via control 1148) to the determined magnitude of forward voltage
so that each LED string may be operated as efficiently as possible. In alternate embodiments,
DC stages 1110, 1112 and/or 1140 may automatically determine the magnitude of forward
voltage needed to forward bias each LED in each LED string 1122, 1124 and/or 1138
and may communicate that voltage to processor 1104 (e.g., via control 1148).
[0082] In one embodiment, each LED array may be configured to operate in accordance with
one or more bias topologies. As per one example, LED array 1122 and 1124 may be configured
in parallel to operate using a single voltage rail (e.g., a single voltage rail generated
by one of DC stages 1110, 1112 or 1140) such that switches 1118 and/or 1120 may be
configured as shown (e.g., via control 1148 from processor 1104) to produce a forward
voltage across each LED array and a forward current through each LED array as may
be modulated by a power switch (e.g., field effect transistors (FETs) 1150 and/or
1152) via control signals 1154 and/or 1156, respectively, as may be appropriately
level shifted by level shifters 1180 and 1182, respectively, whereby the current conducted
by each LED array may be stabilized via ballast elements (e.g., resistors 1126 and
1128). Other power switching elements, such as insulated gate bipolar transistors
(IGBTs) or vertical MOSFETs, may be used instead of FETs 1150 and 1152 as well.
[0083] As per another example, each LED array may be configured in parallel to operate using
a single voltage rail (e.g., a single voltage rail generated by DC stage 1110 or DC
stage 1112) whereby switches 1118 and 1120 may be configured in the opposite configuration
as shown to produce a forward voltage across each LED array and a forward current
through each LED array as may be modulated by a power switch (e.g., FETs 1150 and
1152) via control signals 1154 and/or 1156, respectively, as may be appropriately
level shifted by level shifters 1180 and 1182, respectively, whereby the average current
conducted by each LED array may be stabilized via a current stabilization network
(e.g., inductor 1130/diode 1132 and inductor 1134/diode 1136, respectively).
[0084] Still other examples include configurations whereby each LED array (e.g., LED array
1122 and 1124) may be operated independently using a dedicated DC stage (e.g., DC
stage 1112 and DC stage 1110, respectively) in either of a constant voltage or constant
current configuration using either ballast or inductor-based current stabilization
techniques as may be selected by switches 1118 and 1120.
[0085] As discussed in more detail below, wired node 1108 may include any wired interface
(e.g., DMX, I2C, Ethernet, USB, DALI, 0-10V, etc.) that may be used to configure lighting
system 1100 (e.g., via processor 1104) for operation and/or allow processor 1104 to
communicate the status and operational capability of lighting system 1100 to wired
network 1158 (e.g., BACnet-enabled wired network 1158). Similarly, wireless node 1106
may include any wireless interface (e.g., Wi-Fi, thread-based mesh, Bluetooth, ZigBee,
etc.) that may similarly be used to configure lighting system 1100 (e.g., via processor
1104) for operation and/or allow processor 1104 to communicate the status and operational
capability of lighting system 1100 to wireless network 1160 (e.g., BACnet-enabled
wireless network 1160).
[0086] As discussed above, processor 1104 may be configured to deduce the number of LED
strings that may be under its control as well as the number of LEDs in each LED string.
Such deduction, for example, may occur each time lighting system 1100 is provisioned
with LEDs, either at initial deployment or after reconfiguration. Processor 1104 may
then configure the operation of AC/DC converter 1102 for optimal performance in response
to the number of LED strings found and/or the number of LEDs in each LED string subsequent
to such deduction. Accordingly, the number of LED strings and the number of LEDs in
each LED string contained within lighting system 1100 may not necessarily be fixed
at initial deployment or after each reconfiguration, but rather may be dynamic such
that processor 1104 may intelligently determine the lighting capability of lighting
system 1100 (e.g., the number of LED strings and the number of LEDs in each LED string
after initial deployment and/or after each reconfiguration) and may, therefore, intelligently
select the most efficient mode of operation of each DC stage (e.g., constant current,
constant voltage or a mixture of both), the most efficient magnitude of voltage and/or
current to be generated by each DC stage and may also intelligently select the most
efficient current stabilization mode for each LED string (e.g., ballast or inductor-based
current stabilization).
[0087] It should be noted that the mode of operation of DC stages 1110, 1112 and 1140 may
be programmable (e.g., via control 1148 of processor 1104) to either a constant-voltage
or a constant-current mode of operation. Conversely, the mode of operation of DC stages
1110, 1112 and 1140 may be fixed such that a mixture of both constant-voltage and
constant-current DC stages may exist within AC/DC converter 1102 and may be individually
selected for operation (e.g., via control 1148 of processor 1104) and individually
connected to respective LED strings 1122, 1124 and/or 1138 via a multiplexer (not
shown) within AC/DC converter 1102.
[0088] In alternate embodiments, each DC stage of AC/DC converter 1102 may be paired with
either a ballast-based current stabilization network or an inductor-based current
stabilization network, such that switches 1118 and 1120 may no longer be necessary.
In addition, the operational mode of each DC stage (e.g., constant-current or constant-voltage)
may be predetermined, such that upon configuration of lighting system 1100, LED strings
1122, 1124 and/or 1138 may be statically paired with a ballast-based current stabilization
network, an inductor-based current stabilization network, or both, and each pairing
may include constant-voltage and/or constant-current topologies.
[0089] Turning to FIG. 12, flow diagrams are exemplified whereby processor 1104 may first
discover the number of LED strings initially provisioned and/or reconfigured within
lighting system 1100. Next, processor 1104 may then configure the bias and stabilization
networks of lighting system 1100 that may be necessary for the most efficient mode
of operation of each detected LED string.
[0090] In step 1202, for example, processor 1104 may first select a continuity mode, whereby
AC/DC converter 1102 may be selected to perform a continuity test to determine the
number of LED strings that may exist within lighting system 1100. Initially, a first
DC stage of AC/DC converter 1102 (e.g., DC stage 1112) may be configured by processor
1104 via control 1148 to provide a maximum output voltage (e.g., 250 VDC) as in step
1204, which may then be applied to a first LED string (e.g., LED string 1122 in a
current-limited fashion). In one embodiment, for example, processor 1104 may select
switch 1118 to the position shown via control 1148 and FET 1150 may be momentarily
rendered conductive by processor 1104 via control 1154 (e.g., as in step 1206). In
response, a current may or may not be conducted by resistor 1126, as may be sensed
by current sensor 1162 of processor 1104, to determine whether or not LED string 1122
exists within lighting system 1100. A voltage developed across resistor 1126, for
example, may lead to the determination that a particular magnitude of current is being
conducted by LED string 1122, which may then lead processor 1104 to deduce that LED
string 1122 exists within lighting system 1100. Steps 1202-1206 may then be repeated
as above (e.g., with the same DC stage or a different DC stage within AC/DC converter
1102) to determine the number of LED strings that may or may not exist within lighting
system 1100, the result may then be logged as in step 1208.
[0091] For the one or more LED strings that may be detected through execution of steps 1202-1208
by processor 1104, a substantially minimum magnitude of forward voltage may then be
empirically determined such that each LED string may be operated at maximum efficiency
using the determined minimum magnitude of forward voltage. For example, processor
1104 may first select a continuity mode (as in step 1210), whereby AC/DC converter
1102 may be selected to perform a continuity test to determine the forward voltage
required to illuminate all of the LEDs that may exist within a previously detected
LED string. A first DC stage of AC/DC converter 1102 (e.g., DC stage 1112) that may
correspond to the first detected LED string may first be configured by processor 1104
via control 1148 to provide a maximum output voltage (e.g., 250 VDC) as in step 1212,
which may then be applied to the first detected LED string (e.g., LED string 1122
in a current-limited fashion) as discussed above, for example, in relation to step
1206.
[0092] In step 1214, the applied voltage may be modulated (e.g., decreased from 250 VDC)
by processor 1104 via control 1148 in coarse voltage steps (e.g., 10V steps) until
current stops flowing (e.g., as detected by current sense 1162 as the applied voltage
is decreased from 250 VDC). The coarse voltage obtained in step 1214 may then be logged
by processor 1104 as the minimum coarse voltage magnitude required to illuminate the
LED string.
[0093] In step 1216, the DC stage may be programmed to the minimum coarse voltage from step
1214 increased by one coarse voltage step and then modulated (e.g., decreased) by
processor 1104 via control 1148 in medium voltage steps (e.g., 1V steps) until current
stops flowing (e.g., as detected by current sense 1162). The medium voltage obtained
in step 1216 may then be logged by processor 1104 as the minimum medium voltage magnitude
required to illuminate the LED string.
[0094] In step 1218, the DC stage may be programmed to the sum of the minimum coarse voltage
from step 1214 and the minimum medium voltage from step 1216 increased by one medium
voltage step and then modulated (e.g., decreased) by processor 1104 via control 1148
in fine voltage steps (e.g., 0.1V steps) until current stops flowing (e.g., as detected
by current sense 1162). The voltage may then be increased in fine voltage steps (e.g.,
0.1 VDC steps) until the current begins to flow again. The fine voltage obtained in
step 1218 may then be logged by processor 1104 as the minimum fine voltage magnitude
required to illuminate the LED string.
[0095] Once steps 1214-1218 have been completed, the minimum forward voltage required to
most efficiently illuminate the LED string may have been determined within a minimum
voltage resolution (e.g., 0.1VDC). For example, if the LED string under test contains
72 LEDs where each LED exhibits a forward voltage of 3.1 volts and assuming that the
on-resistance of FET 1150 and the resistance of resistor 1126 adds an additional overhead
voltage (e.g., 0.5 VDC) to the magnitude of forward voltage required to illuminate
LED string 1122, then a minimum forward voltage of approximately 72*3.1 + 0.5 = 223.7
VDC (e.g., constituting a coarse voltage magnitude of 220 VDC, a medium voltage magnitude
of 3 VDC and a fine voltage magnitude of 0.7 VDC) would be required to illuminate
the LED string under test. In such an instance, the first DC stage of AC/DC converter
1102 (e.g., DC stage 1112) corresponding to the first detected LED string of lighting
system 1100 may be programmed by processor 1104 via control 1148 to provide approximately
223.7 VDC (perhaps rounding up to 225-230 volts for increased headroom), instead of
the maximum output voltage (e.g., 250 VDC), such that the first detected LED string
of lighting system 1100 may be operated at the most efficient voltage rail possible
(e.g., substantially equal to the sum of forward voltages (V
f) of all LEDs in the LED string plus the FET, current sense and miscellaneous voltage
overhead) and the current magnitude corresponding to such voltage may be measured
(e.g., via current sense 1162) and logged by processor 1104 (e.g., as in step 1220).
It should be noted that reduced resolution may be obtained when determining the minimum
forward voltage required to most efficiently illuminate the LED string by simply eliminating
step 1218 or steps 1218 and 1216.
[0096] In an alternate embodiment (e.g., as in step 1224), the applied voltage may be modulated
(e.g., increased from 0 VDC) by processor 1104 via control 1148 in coarse voltage
steps (e.g., 10V steps) until current begins to flow (e.g., as detected by current
sense 1162 as the applied voltage is increased from 0 VDC). The coarse voltage obtained
in step 1224 may then be decreased by one coarse voltage step and then logged by processor
1104 as the minimum coarse voltage magnitude required to illuminate the LED string.
[0097] In step 1226, the DC stage may be programmed to the minimum coarse voltage from step
1224 and then modulated (e.g., increased) by processor 1104 via control 1148 in medium
voltage steps (e.g., 1V steps) until current begins to flow (e.g., as detected by
current sense 1162). The medium voltage obtained in step 1226 may be decreased by
one medium voltage step and then logged by processor 1104 as the minimum medium voltage
magnitude required to illuminate the LED string.
[0098] In step 1228, the DC stage may be programmed to the sum of the minimum coarse voltage
from step 1224 and the minimum medium voltage from step 1226 and then modulated (e.g.,
increased) by processor 1104 via control 1148 in fine voltage steps (e.g., 0.1V steps)
until current begins to flow (e.g., as detected by current sense 1162). The fine voltage
obtained in step 1228 may then be logged by processor 1104 as the minimum fine voltage
magnitude required to illuminate the LED string. Once steps 1224-1228 have been completed,
the minimum forward voltage required to most efficiently illuminate the LED string
may have been determined within a minimum voltage resolution (e.g., 0.1VDC) similarly
as discussed above in relation to steps 1214 to 1218 and the current magnitude corresponding
to such voltage may be measured (e.g., via current sense 1162) and logged by processor
1104 (e.g., as in step 1220). It should be noted that reduced resolution may be obtained
when determining the minimum forward voltage required to most efficiently illuminate
the LED string by simply eliminating step 1228 or steps 1228 and 1226.
[0099] In one embodiment, processor 1104 may determine which current stabilization mode
to utilize depending upon the results of steps 1210-1220 or steps 1210-1212, steps
1224-1228 and step 1220. For example in step 1230, processor 1104 may compare the
optimal forward voltage for each detected LED string. In step 1234, comparison of
the optimal forward voltage deduced for each detected LED string may lead to a determination
that each optimal forward voltage may be approximately equal and in such an instance,
a ballast-based stabilization technique may be selected as in step 1236, whereby each
LED string may be operated from the same DC stage of AC/DC converter 1102 and the
current in each LED string may be appropriately stabilized by its associated ballast
resistor and modulated (e.g., increased or decreased on average overtime) by analog
control and/or appropriate control of the duty cycle of each power switch associated
with each LED string (e.g., FET 1150/duty cycle control 1154 for LED string 1122 and
FET 1152/duty cycle control 1156 for LED string 1124).
[0100] If, on the other hand, the deduced optimal forward voltages for each detected LED
string are not substantially equal, inductor-based current stabilization may instead
be selected (e.g., as in step 1238), whereby each LED string may be operated from
independent DC stages of AC/DC converter 1102 (e.g., constant current DC stages each
set at the optimal forward voltage associated with each LED string) and the current
in each LED string may be appropriately stabilized by its associated inductor/diode
pair and modulated (e.g., increased or decreased on average over time) by analog control
and/or appropriate control of the duty cycle of each power switch associated with
each LED string (e.g., FET 1150/duty cycle control 1154 for LED string 1122 and FET
1152/duty cycle control 1156 for LED string 1124).
[0101] It should be noted that the inductor (e.g., inductor 1130 or inductor 1134) of an
inductor-based current stabilization network may add an additional forward voltage
component to the minimum voltage required to operate an LED string. However, since
the voltage magnitude of each DC stage of AC/DC converter 1102 may be optimally controlled
(e.g., minimized), the magnitude of inductance required by each inductor may be minimized
as well (thereby minimizing the physical size of the inductor), since the required
inductance magnitude is directly proportional to the voltage developed across the
inductor.
[0102] In one embodiment, a capacitor (e.g., capacitor 1168 and 1170) may be optionally
placed across LED strings 1122 and 1124, respectively, to a reference potential (e.g.,
ground) in either of a ballast-based or inductor-based current stabilization mode
of operation. In a ballast-based mode of operation, for example, the capacitor may
be selected for a specific output voltage ripple to maintain a substantially constant
output voltage under load transient conditions.
[0103] In an inductor-based current stabilization mode of operation, on the other hand,
capacitors (e.g., capacitors 1168 and 1170) may interact with inductors (e.g., inductors
1130 and 1134, respectively) to provide AC current filtering, thereby allowing the
capacitor to control the ripple current to acceptable levels as required by each LED
string while at the same time decreasing the required inductance magnitude, thereby
further minimizing the physical size and cost of the inductor. For example, by allowing
smaller inductance magnitudes to be selected, the resulting increase in peak-to-peak
current ripple may be conducted by each capacitor (e.g., capacitor 1168 and 1170),
thereby maintaining the magnitude of current ripple experienced by each LED string
(e.g., LED string 1122 and 1124, respectively) to within acceptable limits (e.g.,
10% of the DC forward current conducted by each LED string).
[0104] It should also be noted that other algorithms may be used to determine the current
stabilization technique other than those algorithms depicted in steps 1230-1238. For
example, inductor-based current stabilization may be selected by processor 1104 even
though the optimal forward voltage for each detected LED string may be approximately
equal and operated from the same or different DC stages of AC/DC converter 1102. Conversely,
ballast-based current stabilization may be selected by processor 1104 even though
the optimal forward voltage for each detected LED string may be substantially unequal
and operated from the same or different DC stages of AC/DC converter 1102.
[0105] Algorithms defining the operation of lighting system 1100 (e.g., algorithms described
by the execution steps of FIG. 12) may, for example, fully reside within processor
1104 (e.g., flash memory that is local to processor 1104). Alternately, such algorithms
may fully reside within a network (e.g., wired network 1158 and/or wireless network
1160) whereby execution instructions associated with such algorithms may be received
by processor 1104 via wired node 1108 and/or wireless node 1106. Conversely, algorithms
defining the operation of lighting system 1100 (e.g., algorithms described by the
execution steps of FIG. 12) may be distributed to partially reside within processor
1104 and partially reside within a network (e.g., wired network 1158 and/or wireless
network 1160) whereby a portion of execution instructions may be received by processor
1104 via wired node 1108 and/or wireless node 1106.
[0106] In operation, the status of lighting system 1100 may be continuously monitored and
such status may be relayed to wired network 1158 and/or wireless network 1160 via
wired node 1108 and/or wireless node 1106, respectively. As per one example, processor
1104 may continuously monitor the current conducted by each LED string (e.g., LED
strings 1122, 1124 and/or 1138 as may be measured by current sense 1162, 1164 and/or
1166, respectively) to determine whether each LED string is operating in accordance
with the logged current magnitudes for each LED string (e.g., as logged by step 1220
of FIG. 12). A detected fault (e.g., zero conducted current) in one LED string, for
example, may result in the deactivation of at least the faulted LED string and perhaps
the remaining LED strings by causing the associated voltage and current regulation
devices (e.g., FETs 1150 and/or 1152) to remain non-conductive (e.g., via control
signals 1154 and 1156, respectively). Such detected faults and subsequent actions
taken by processor 1104 may then be reported (e.g., via wired network 1158 and/or
wireless network 1160) to allow maintenance personnel to react to the reported fault
(e.g., decommissioning of the faulted lighting system and the subsequent commissioning
of a replacement lighting system).
[0107] In alternate embodiments, trends of each LED string may be tracked to predict, for
example, efficiency, maximum light output, peak wavelength and spectral wavelength
variations due to increased junction temperature. Increased junction temperatures,
for example, may be related to a forward voltage decrease of a particular LED string
due to a reduction in the bandgap energy of the active region of each LED in the LED
string as well as a decrease in the series resistance of each LED occurring at high
temperatures. Accordingly, for example, by tracking a reduced forward voltage of a
particular LED string over time, predictions may be made and reported by processor
1104 (e.g., via wired network 1158 and/or wireless network 1160) as to certain performance
parameters of each LED string so that maintenance personnel may respond accordingly.
[0108] Turning to FIG. 13, an alternate embodiment of lighting system 1300 is exemplified,
such that the current stabilization topologies may not be selectable and may instead
be provided as ballast-based current stabilization networks for each LED string utilized
within lighting system 1300 or not at all. For example, the forward voltage (V
f) of each LED string 1322, 1380 and 1324 may be closely matched such that ballast
elements 1326, 1382 and 1328, respectively, may not be necessary. In addition, a single
DC stage 1340 may be utilized within AC/DC converter 1302, which may provide a single-rail
voltage magnitude (e.g., via voltage signal 1390 at node 1310) in a constant-current
mode of operation to multiple LED strings connected in a parallel configuration (e.g.,
LED strings 1322, 1324 and 1380).
[0109] Similarly as discussed above in relation to FIG. 11, wired node 1308 may include
any wired interface (e.g., DMX, I2C, Ethernet, USB, DALI, 0-10V, etc.) that may be
used to configure lighting system 1300 (e.g., via processor 1304) for operation and/or
allow processor 1304 to communicate the status and operational capability of lighting
system 1300 to wired network 1358 (e.g., BACnet-enabled wired network 1358). Similarly,
wireless node 1306 may include any wireless interface (e.g., Wi-Fi, thread-based mesh,
Bluetooth, ZigBee, etc.) that may similarly be used to configure lighting system 1300
(e.g., via processor 1304) for operation and/or allow processor 1304 to communicate
the status and operational capability of lighting system 1300 to wireless network
1360 (e.g., BACnet-enabled wireless network 1360).
[0110] The number of series-connected LEDs (e.g., one or more) in each LED string (e.g.,
1322, 1324 and 1380) may be selected based upon the sum of forward voltage (V
f) of each series-connected LED, where the forward voltage of each LED string may be
selected to be substantially equal. In one embodiment, for example, an LED string
may be selected to contain about 45 to 50 (e.g., 46) LEDs each having a V
f between about 2.5V and 3.5V (e.g., 3V) for a cumulative forward voltage of 46*3 =
138V for the LED string. In an alternate embodiment, for example, an LED string may
be selected to contain about 60 to 75 (e.g., 69) LEDs each having a V
f between about 1.5V and 2.5V (e.g., 2V) for a cumulative forward voltage of 69*2 =
138V for the LED string.
[0111] In alternate embodiments, each LED string may have the same or a different number
of LEDs, but due to differences in V
f for each LED type in each LED string, each LED string may exhibit a forward voltage
that is substantially equal to the forward voltage of each of the other LED strings.
Furthermore, while only three LED strings are depicted, any number of LED strings
(e.g., 4) may be utilized. Still further, each of LED strings 1322, 1324 and 1380
may reside within a single lighting fixture or may reside within multiple lighting
fixtures.
[0112] Due to slight deviations in the V
f for each LED of each LED string (e.g., due to forward current deviations in each
LED string), the cumulative forward voltage for each LED string may not necessarily
conform to the calculations above, which may necessitate the existence of ballast
elements (e.g., resistor 1326, 1328 and 1382) such that the voltage magnitude at node
1310 may be allowed to remain substantially equal under all load conditions for each
LED string. Furthermore, each ballast element may facilitate current stabilization
as well as current sense measurements by processor 1304 as discussed in more detail
below.
[0113] Processor 1304 may be configured to deduce the number of LED strings that may be
under its control as well as the forward current requirements (e.g., minimum and maximum
forward current) in each LED string. Such deduction, for example, may occur each time
lighting system 1300 is provisioned with LEDs, either at initial deployment or after
reconfiguration.
[0114] Turning to FIG. 14, flow diagrams are exemplified whereby processor 1304 may first
discover the number of LED strings initially provisioned and/or reconfigured within
lighting system 1300. Next, processor 1304 may then configure the current provisioning
for each LED string of lighting system 1300.
[0115] In a first embodiment, processor 1304 may have control of both the voltage and current
magnitude output of DC stage 1340 via control 1348. In such an instance, processor
1304 may configure DC stage 1340 to its minimum voltage output (e.g., as in step 1402)
and its maximum current output (e.g., as in step 1404). Processor 1304 may then configure
lighting system 1300 for a continuity check (e.g., as in step 1406) whereby, for example,
processor 1304 may render one of LED strings 1322, 1380 and 1324 conductive by transitioning
one of power switches (e.g., FETs 1350, 1352 or 1386, respectively), into a conductive
state. In step 1408, the output voltage magnitude of DC stage 1340 may be increased
(e.g., as in steps 1224 through 1228 of FIG. 12) until current is conducted through
the LED string under test (e.g., as may be detected by current sense 1362, 1366 or
1364, respectively). Processor 1304 may then decrease the current conducted by the
LED string under test via control 1348 by programming the current output of DC stage
1340 to decreasingly lower magnitudes (e.g., in 1 mA steps decreasing from the maximum
current set in step 1404) until current ceases to flow (e.g., as in step 1410). In
step 1412, for example, processor 1304 may then log the minimum voltage and current
magnitudes as measured by steps 1408 and 1410 into a memory location (e.g., as located
on-board processor 1304 and/or as may be located in memory locations of wired network
1358 and/or wireless network 1360).
[0116] In an alternate embodiment, processor 1304 may program the current magnitude output
of DC stage 1340 via control 1348, but DC stage 1340 may internally adjust the output
voltage as required to produce the programmed current magnitude output of DC stage
1348. In such an instance, processor 1304 may configure DC stage 1340 to its maximum
current output (e.g., as in step 1414). Processor 1304 may then configure lighting
system 1300 for a continuity check (e.g., as in step 1416) whereby, for example, processor
1304 may render one of LED strings 1322, 1380 and 1324 conductive by transitioning
one of power switches (e.g., FETs 1350, 1352 or 1386, respectively), into a conductive
state. The output voltage magnitude of DC stage 1340 may then be internally increased
(e.g., increased by circuitry located internal to DC stage 1340) until current is
conducted through the LED string under test (e.g., as may be detected by current sense
1362, 1366 or 1364, respectively). Processor 1304 may then decrease the current conducted
by the LED string under test via control 1348 by programming the current output of
DC stage 1340 to decreasingly lower magnitudes (e.g., in 1 mA steps decreasing from
the maximum current set in step 1414) until current ceases to flow (e.g., as in step
1418). In step 1420, for example, processor 1304 may then log the minimum voltage
(e.g., as may be reported by DC stage 1340 to processor 1304 via control 1348) and
current magnitudes (e.g., minimum and maximum current magnitudes) as measured by step
1418 into a memory location (e.g., local to processor 1304 and/or as may be located
in memory locations of wired network 1358 and/or wireless network 1360).
[0117] Once the initial configuration of each LED string is complete and lighting system
1300 is operational, each subsystem of lighting system 1300 may be monitored (e.g.,
as in step 1422) to, for example, continuously determine the operational status of
lighting system 1300. For example, each LED string of lighting system confirmed to
be operational (e.g., as in steps 1402-1412 or steps 1414-1420) may be continuously
monitored (e.g., the forward current of each LED string may be continuously monitored)
for normal operation. If the measured forward current substantially equals the current
magnitudes as logged in steps 1412 or 1420 taking into account any digital current
modulation performed by power switches (e.g., FETs 1350, 1352 and/or 1386), such as
reduced forward current through less than 100% duty cycle modulation of the power
switches, then normal status of lighting system 1300 may be reported (e.g., as in
step 1426). If, on the other hand, the modulated forward current does not meet previously
verified current magnitudes, then abnormal status of lighting system 1300 may be reported
(e.g., as in step 1428) and reported to, for example, wired network 1358 and/or wireless
network 1360 to alert maintenance personnel of the abnormal status.
[0118] Other operational aspects of lighting system 1300 may be monitored as well. For example,
temperature sensors and fans (e.g., temperature sensors 1016 and fans 1014 as exemplified
in FIG. 10) may be utilized by lighting system 1300 to ensure that, for example, the
temperature of each LED string is operating within specification. If not, the abnormal
temperature and/or fan malfunction may be reported as in step 1428; otherwise, normal
fan and temperature status may be reported as in step 1426.
[0119] Processor 1304 may implement a hybrid dimming scheme, whereby both digital modulation
of LED string current (e.g., via PWM control of the power switches) and analog modulation
of LED string bias current may be used to provide deep dimming control of the LED
string intensity while minimizing audible and radiated noise. In step 1430, for example,
the minimum and maximum current magnitudes (e.g., as determined in steps 1414 and
1418) may be accessed by processor 1304 to determine the full range of DC bias current
magnitudes (e.g., as produced by DC stage 1340) that may be utilized to illuminate
a particular LED string (e.g., LED string 1322) across a range of intensity. As per
one example, the maximum current for an LED string (e.g., LED string 1322) may be
determined to be equal to an upper current limit (e.g., 1.25A as determined in step
1414 so that LED string 1322 may produce full intensity), whereas the minimum current
for the LED string may be determined to be equal to a percentage of the upper current
limit (e.g., 30% of 1.25A or 0.375A).
[0120] In step 1432, processor 1304 may determine the range over which analog control of
the current magnitude may be used to select a particular intensity of light emission
from a particular LED string. In one embodiment, for example, processor 1304 may determine
that for all current magnitudes conducted by an LED string (e.g., LED string 1322)
between a maximum current magnitude and a minimum threshold current magnitude (e.g.,
30% of the maximum current magnitude), analog control (e.g., the continuous bias current
magnitude provided by DC stage 1340 as commanded by control 1348) may be used. That
is to say for example, that for light intensities produced by LED string 1322 between
a maximum intensity and a lower threshold intensity (e.g., 30% of maximum intensity),
processor 1304 may command DC stage 1340 to the desired bias current magnitude via
control 1348 as required to produce the desired intensity range (e.g., 1.25A of continuous
DC bias current for maximum intensity and 0.375A of continuous DC bias current for
30% intensity). Variation between maximum intensity and the lower threshold intensity
may be accomplished through variation of the continuous DC bias current generated
by DC stage 1340 via control 1348 from processor 1304 in programmable steps (e.g.,
1 mA steps). In each instance, the averaged current conducted by LED string 1322 may
be equal to the continuous DC bias current generated by DC stage 1340 as delivered
to LED string 1322 via node 1310, as may be controlled by FET 1350 in accordance with
an appropriate DC control signal 1354 applied to the gate terminal of FET 1350.
[0121] In step 1434, processor 1304 may determine the range over which digital control of
the current magnitude may be used to select a particular intensity (e.g., below the
lower threshold intensity) of light emission from a particular LED string. In one
embodiment, for example, processor 1304 may determine that for all current magnitudes
conducted by an LED string (e.g., LED string 1322) between the lower threshold intensity
(e.g., 30% of maximum intensity) and a minimum intensity (e.g., 1% of maximum intensity),
digital control (e.g., PWM modulation of FET 1350 to produce a discontinuous current
signal where the current signal is reduced from a non-zero magnitude to a zero magnitude
according to the duty cycle of the PWM modulation over multiple periods) may be used.
In particular, any number (e.g., 256) of PWM duty cycle variations may be used to
modulate the minimum bias current generated by DC stage 1340 and provided to LED string
1322 via node 1310 between an average bias current (e.g., averaged over multiple periods
of maximum duty cycle discontinuities in the current signal) required to produce the
lower threshold intensity and an average bias current (e.g., averaged over multiple
periods of minimum duty cycle discontinuities in the current signal) required to produce
the minimum intensity.
[0122] In step 1436, dimming may be adjusted through a combination of both analog and digital
controls. As per one example, analog control of light intensities produced by an LED
string (e.g., LED string 1322) between a maximum intensity and a lower threshold intensity
(e.g., 30% of maximum intensity) may be accomplished via appropriate control of DC
stage 1340 via control 1348 to generate continuous DC bias current magnitudes required
to produce intensities between the maximum intensity (e.g., 1.25A bias current magnitude)
and the lower threshold intensity (e.g., 0.375A bias current magnitude) in programmable
and continuous current steps (e.g., 1 mA steps) for an intensity control granularity
substantially equal to, for example, (0.001/(1.25-0.375))* 100 ≅ 0.1%. As per the
same example, digital control of light intensities produced by an LED string (e.g.,
LED string 1322) between the lower threshold intensity (e.g., 30% of maximum intensity)
and a minimum intensity (e.g., 1% of maximum intensity) may be accomplished via appropriate
modulation of the lower threshold bias current generated by DC stage 1340 via PWM
control 1354 to produce discontinuities in the bias current to program light intensities
below the lower threshold intensity. In one embodiment, for example, 256 DMX control
values via wired node 1308 may be used to vary the intensity between the lower threshold
intensity (e.g., 30% of maximum intensity using maximum duty cycle discontinuities
in the bias current) and the minimum intensity (e.g., 1% of maximum intensity using
minimum duty cycle discontinuities in the bias current) with a control granularity
substantially equal to (30%-1%)/256 ≅ 0.1%.
[0123] Through implementation of PWM control only over the lower portion of the current
control range (e.g., the lower 30% of the current control range), fidelity may be
improved within that range by, for example, reducing conducted emissions, reducing
radiated emissions and reducing audible noise pollution. Furthermore, color mixing
control across all LED strings (e.g., LED strings 1322, 1380 and 1324) may be enhanced
through the application of digital dimming control beyond the limitations conventionally
imposed by analog dimming, which for example, may deteriorate when analog dimming
is attempted below a threshold dimming percentage (e.g., 10% of maximum intensity).
Furthermore, by limiting the digital dimming control to lower levels of intensity
(e.g., 1% to 30% of maximum intensity), the frequency of discontinuities in the PWM
control waveform may be increased to frequencies above about 20 kHz (e.g., between
about 20 kHz and 1 MHz) that may be less prone to generate detectable flicker and
shimmer thereby further enhancing dimming fidelity.
[0124] In one embodiment, processor 1304 may determine that DC stage 1340 may not provide
a magnitude of current that may be required by each of LED strings 1322, 1324 and
1380 operating at 100% intensity or lower. In such an instance, processor 1304 may
implement a current sharing algorithm whereby each of the LED strings 1322, 1380 and
1324 may be operated at a percentage intensity that may be accommodated by DC stage
1340. For example, DC stage 1340 may only be capable of providing an upper limit of
current magnitude (e.g., 1.2A) and in such and instance, processor 1304 may apportion
a percentage of the upper limit current magnitude to each of LED strings 1322, 1380
and 1324 as may be necessary using analog control, digital control or a combination
of analog and digital control as discussed above.
[0125] It should be noted that any one LED string may be apportioned 100% of the available
current from DC stage 1340 using the current sharing algorithm. Conversely, any number
of LED strings may share any portion of the available current from DC stage 1340.
As per one example, each LED string may equally share in the available current, whereby
the magnitude of current apportioned to any one LED string may be calculated as the
maximum current available divided by the number of activated LED strings (e.g., three
activated LED strings may each receive 0.4A of the available 1.2A from DC stage 1340)
by any of an analog, digital or combination of analog/digital current control algorithm
as discussed above.
[0126] In an alternate embodiment, for example, processor 1304 may determine that DC stage
1340 may provide a magnitude of current that may meet or exceed the requirement of
any one or more LED strings 1322, 1324 and 1380 operating at 100% intensity or lower.
In such an instance, processor 1304 may implement a current provisioning algorithm
whereby any one or more of the LED strings 1322, 1380 and 1324 may be operated at
a commanded percentage intensity using a combination of analog and/or digital current
control as discussed above.
[0127] As per one example, DC stage 1340 may be commanded to a current magnitude of 1.2A,
but each of LED strings 1322, 1380 and 1324 may only require 0.4A on average via appropriate
PWM control of their associated power switches (e.g., FETs 1350, 1352 and 1386, respectively)
to operate at their respective commanded intensity. In such an instance, 1.2A may
be conducted instantaneously by any one LED string 1322, 1380 and 1324 at a time (e.g.,
only one of LED strings 1322, 1380 and 1324 may be conductive at any given time),
but through time division multiple access (TDMA) control, each LED string may be operating
at 33% duty cycle to receive only the required 0.4A on average to operate at its commanded
intensity. It should be noted that through analog and/or digital current control and
proper time division multiple access to such controlled current, any one LED string
may operate at any intensity (e.g., 0-100%) at any given time (e.g., any one LED string
may be conductive to the mutual exclusion of all of the other LED string conductivity
states) to operate on average at the commanded intensity.
[0128] Examples of such TDMA control are illustrated in FIGs. 15A, 15B, 15C, 15D and 15E.
In FIG. 15A, for example, in any given TDMA period 1502, any LED string (e.g., any
of LED strings 1322, 1380 and/or 1324 of FIG. 13) may be allocated a time slot (e.g.,
time slots 1504, 1506 and 1508, respectively) within which any one LED string may
receive any magnitude percentage (e.g., 0-100%) of any of an analog and/or a digitally
controlled current signal (e.g., current signals 1392, 1394 and 1396 of FIG. 13, respectively).
[0129] In time slot 1504, for example, processor 1304 may command LED string 1322 to conduct
a percentage (e.g., 100%) of the maximum available current by causing a maximum magnitude
of bias current from a corresponding DC stage (e.g., DC stage 1340 via control 1348)
to be conducted by LED string 1322. Capacitor 1368 may, for example, be utilized to
extend the on-time of LED string 1322 by allowing the current conducted at the end
of time slot 1504 to decay into the beginning of time slot 1506 in accordance with
the RC time constant created by capacitor 1368 in combination with the resistance
of each LED in LED string 1322. In such an instance, for example, the light emitted
by LED string 1322 at the end of time slot 1504 may be blended with the light emitted
by LED string 1380 at the beginning of time slot 1506 so as to implement true mixing
of the light emitted by LED string 1322 with the light emitted by LED string 1380
across the end of time slot 1504 and into the beginning of time slot 1506.
[0130] In time slots 1506 and 1508, LED strings 1380 and 1324, respectively, may similarly
be programmed to receive analog and/or digitally controlled current signals so that
a percentage (e.g., 100%) of the maximum available current from DC stage 1340 may
be received by each of LED strings 1380 and 1324 in their respective time slots. Capacitors
1372 and 1370 may, for example, be similarly utilized to extend the on-time of LED
strings 1380 and 1324, respectively, by allowing the current conducted at the end
of time slot 1506 to decay into the beginning of time slot 1508 and by allowing the
current conducted at the end of time slot 1508 to decay into the beginning of time
slot 1504 in accordance with the RC time constants created by capacitors 1372 and
1370, respectively, in combination with the resistance of each LED in LED strings
1380 and 1324, respectively. In such an instance, for example, the light emitted by
LED string 1380 at the end of time slot 1506 may be blended with the light emitted
by LED string 1324 at the beginning of time slot 1508 and the light emitted by LED
string 1324 at the end of time slot 1508 may be blended with the light emitted by
LED string 1322 at the beginning of time slot 1504.
[0131] In alternate embodiments, capacitors 1368, 1372 and 1370 may not exist at all and
optional slew rate control 1393, 1395 and 1397 may instead be implemented either as
hardware networks or executed in software by processor 1304. Slew rate control 1393,
1395 and 1397 may, for example, be implemented via hardware and may include resistor/capacitor
networks combined with other elements (e.g., diodes) to increase or decrease the slew
rate of control signals 1354, 1342 and 1356, respectively, thereby controlling the
rate at which power switches 1350, 1352 and 1386, respectively, become conductive
and/or non-conductive. Slew rate control 1393, 1395 and 1397 may, for example, be
implemented via software, whereby processor 1304 may execute embedded firmware or
commands issued by wired network 1358 or wireless network 1360 to increase or decrease
the slew rate of control signals 1354, 1342 and 1356, respectively, thereby controlling
the rate at which power switches 1350, 1352 and 1386, respectively, become conductive
and/or non-conductive.
[0132] It should be noted that since each of LED strings 1322, 1380 and 1324 may receive
a maximum bias current magnitude in each of respective time slots 1504, 1506 and 1508
and since each of time slots 1504, 1506 and 1508 are of equal time duration, the average
amount of current conducted by each of LED strings 1322, 1380 and 1324 over multiple
time periods 1502 is substantially equal to about 1/3 the maximum current available
from DC stage 1340.
[0133] Stated differently, the average magnitude of current conducted by any one of LED
strings 1322, 1380 or 1324 over multiple periods 1502 may be calculated by multiplying
the current available from DC stage 1340 (e.g., as selected by control 1348) by the
ratio of time slot 1504, 1506 or 1508, respectively, to period 1502, which as stated
above may be equal to 1/3 since each time slot exhibits an equal time duration.
[0134] It should be further noted that current conducted by LED strings 1322, 1380 and 1324
in each of time slots 1504, 1506 and 1508, respectively, may be modulated (e.g., pulse
width modulated) to further reduce the average amount of current conducted over time.
As discussed above, for example, any one of 256 duty cycle selections may be made
by processor 1304 such that the amount of current conducted by each LED string 1322,
1380 and 1324 in each time slot 1504, 1506 and 1508, respectively, may be further
reduced on average by the duty cycle selection of control signals 1354, 1342 and 1356,
respectively.
[0135] FIG. 15A exemplifies a TDMA current sharing mode whereby each of LED strings 1322,
1380 and 1324 may share a magnitude of current (e.g., 0-100% of the current available
from DC stage 1340 as selected by processor 1304 via control 1348) during each of
mutually exclusive time slots 1504-1508. If the time duration of time slots 1504-1508
are substantially equal during time period 1502, then as discussed above for example,
the average current magnitude conducted by each of LED strings 1322, 1380 and 1324
over multiple time periods 1502 may be substantially equal to 1/3 the magnitude of
current provided by DC stage 1340 on average. Stated differently, each of LED strings
1322, 1380 and 1324 may conduct all of the current provided by DC stage 1340 during
respective mutually exclusive time slots 1504-1508, but since each time slot constitutes
an amount of time substantially equal to 1/3 of time period 1502, then on average,
each of LED strings 1322, 1380 and 1324 may conduct a magnitude of current over multiple
time periods 1502 that may be substantially equal to 1/3 the magnitude of current
provided by DC stage 1340.
[0136] TDMA current sharing mode, however, may rely upon each LED string associated with
each TDMA time slot to conduct the entire magnitude of current provided by DC stage
1340. Accordingly, each LED of each LED string may be operating at a reduced efficacy
(e.g., as measured in lumens per watt), since LED efficacy may be inversely proportional
to the magnitude of current conducted by each LED. In order to increase the efficacy
of each LED of each LED string while conducting the same amount of current on average,
for example, processor 1304 may transition from a TDMA current sharing mode to a direct
drive mode, whereby each LED string (e.g., LED strings 1322, 1380 and 1324) may continuously
conduct a reduced magnitude of current during the entire period 1502 that may be substantially
equal to the averaged amount of current conducted by each LED string while operating
in a TDMA current sharing mode.
[0137] As discussed above, for example, FIG. 15A exemplifies a TDMA current sharing mode
whereby each LED string 1322, 1380 and 1324 may conduct all of the current provided
by DC stage 1340, but since each TDMA time slot is substantially equal to 1/3 of time
period 1502, the current magnitude conducted on average over multiple time periods
1502 may be substantially equal to 1/3 the current provided by DC stage 1340. In this
instance and in order to increase LED efficacy, for example, processor 1304 may transition
to a direct drive mode of operation, whereby each LED string (e.g., LED string 1322,
1380 and 1324) may be made concurrently conductive (e.g., by applying appropriate
control signals 1354, 1342 and 1356, respectively) such that current may be conducted
by each LED string (e.g., LED string 1322, 1380 and 1324) at the same time for each
time period 1502. As a result, the magnitude of current conducted by each LED string
(e.g., LED string 1322, 1380 and 1324) may be reduced by the number of LED strings
connected to node 1310 (e.g., 3) thereby increasing efficacy while maintaining the
intensity substantially equal to the intensity obtained while operating in TDMA current
sharing mode.
[0138] In one embodiment, processor 1304 may be configured (e.g., via firmware executing
within processor 1304 or via wired network 1358 or wireless network 1360) to transition
between TDMA current sharing mode and direct drive mode when the TDMA time slots (e.g.,
time slots 1504, 1506 and 1508) are substantially equal to each other or within a
percentage range of between zero percent and twenty percent (e.g., between about zero
percent and five percent) of each other. As per one example, if time slots 1504 and
1506 constitute 35% of period 1502 and time slot 1508 constitutes 30% of period 1502,
processor 1304 may determine that time slots 1504, 1506 and 1508 are substantially
equal within a threshold percentage range of each other so as to justify a transition
from TDMA current sharing mode to direct drive mode in order to effectuate substantially
the same intensity produced by each LED string but with significantly increased efficacy.
In such an instance, for example, each of LED strings 1322, 1380 and 1324 may be made
concurrently conductive (e.g., via appropriate control signals 1354, 1342 and 1356,
respectively) during each time period 1502. As a result, each of LED strings 1322,
1380 and 1324 may be concurrently conducting substantially less current (e.g., LED
strings 1322, 1380 and 1324 may each present substantially the same current load to
node 1310 each conducting 1/3 the available current from DC stage 1340) as compared
to a TDMA current sharing mode thereby increasing efficacy while maintaining substantially
the same intensity.
[0139] In alternate embodiments, as discussed in relation to FIG. 15D, a direct drive mode
may be applied to less than all of the LED strings while the remaining LED strings
may be operating in a TDMA current sharing mode. As per one example, LED strings 1322,
1380 and 1324 may be operating in a TDMA current sharing mode whereby time slots 1534
and 1536 may be substantially equal (e.g., both time slots equal to 40% of period
1532) whereas time slot 1538 may be of a substantially less time duration (e.g., equal
to 20% of period 1532). In such an instance, processor 1304 may command both LED strings
1322 and 1380 to be concurrently conductive during time slots 1534 and 1536 to effectuate
a direct drive mode via appropriate control signals 1354 and 1342, respectively, such
that both LED strings 1322 and 1380 may be operating at substantially the same intensity
as compared to operation in a TDMA current sharing mode, except with half the magnitude
of conducted current (e.g., LED strings 1322 and 1380 may each present substantially
the same current load to node 1310 each conducting half the available current from
DC stage 1340) and, therefore, substantially increasing efficacy for each LED of LED
strings 1322 and 1380. LED string 1324, on the other hand, may continue to operate
in a TDMA current sharing mode, whereby the full amount of current provided by DC
stage 1340 may be exclusively conducted by LED string 1324 during time slot 1538.
[0140] In other embodiments as exemplified in FIG. 15E, power control signal 1348 may be
utilized by processor 1304 to further enhance efficacy by first decreasing a current
magnitude output of DC stage 1340 and then transferring operation to a direct drive
mode to produce an equivalent intensity as compared to an average intensity that may
be achieved using TDMA current sharing mode. As per an example, LED strings 1322,
1380 and 1324 may be operating in a TDMA current sharing mode at an intensity selected
by processor 1304 as a percentage (e.g., 10%) of maximum intensity. In such an instance,
processor 1304 may select 100% current output from DC stage 1340 via control signal
1348 and subsequently select each of LED strings 1322, 1380 and 1324 to be conductive
during time slots 1544, 1546 and 1548, where each respective time slot may be substantially
equal to 10% of time period 1542 in order to achieve 10% intensity on average from
each of LED strings 1322, 1380 and 1324. Alternately and in order to significantly
increase efficacy, for example, processor 1304 may instead select 30% current output
from DC stage 1340 via control signal 1348 and subsequently select each LED string
1322, 1380 and 1324 to be concurrently conductive throughout time period 1542 thereby
allowing each respective LED string to conduct a substantially decreased current magnitude
(e.g., LED strings 1322, 1380 and 1324 may each conduct 1/3 of the 30% current output
from DC stage 1340 to equal 1/10 the current magnitude as compared to the current
magnitude conducted in TDMA current sharing mode) except with substantially increased
efficacy and substantially the same intensity on average.
[0141] Turning to FIG. 15B, in any given TDMA period 1510, any one or more LED strings (e.g.,
any of LED strings 1322, 1380 and/or 1324 of FIG. 13) may be denied a time slot (e.g.,
time slot 1514 does not provide for an active current conduction state within which
LED string 1380 may receive current). As per an example, only two time slots (e.g.,
time slots 1512 and 1516) may be allocated within which any two LED strings (e.g.,
LED strings 1322 and 1324, respectively) may receive any of an analog and/or a digitally
controlled current signal.
[0142] In time slot 1512, for example, processor 1304 may command LED string 1322 to conduct
a percentage (e.g., 100%) of the maximum available current by causing a maximum magnitude
of bias current from a corresponding DC stage (e.g., DC stage 1340) to be conducted
by LED string 1322. In time slot 1516, LED string 1324 may similarly be programmed
to receive an analog and/or digitally controlled current signal so that a percentage
(e.g., 100%) of the maximum available current from DC stage 1340 may be received by
LED string 1324.
[0143] It should be noted that since each of LED strings 1322 and 1324 receive a maximum
bias current magnitude in each of respective time slots 1512 and 1516 and since time
slot 1512 is twice the duration of time slot 1516, the average amount of current conducted
by LED string 1322 over multiple time periods 1510 is substantially equal to about
2/3 the maximum current available from DC stage 1340 and the average amount of current
conducted by LED string 1324 over multiple time periods 1510 is substantially equal
to about 1/3 the maximum current available from DC stage 1340.
[0144] It should be further noted that current conducted by LED strings 1322 and 1324 in
each of time slots 1512 and 1516, respectively, may be modulated (e.g., pulse width
modulated) to further reduce the average amount of current conducted over time. As
discussed above, for example, any one of 256 duty cycle selections may be made by
processor 1304 such that the amount of current conducted by each LED string 1322 and
1324 in each time slot 1512 and 1516, respectively, may be further reduced on average
by the duty cycle selection of control signals 1354 and 1356, respectively.
[0145] Turning to FIG. 15C, in any given TDMA period 1520, any one or more LED strings (e.g.,
any of LED strings 1322, 1380 and/or 1324 of FIG. 13) may be denied a time slot (e.g.,
time slots 1524 and 1526 do not provide for an active current conduction state within
which LED string 1380 and 1324 may receive current). As per an example, only one time
slot (e.g., time slot 1522) may be allocated within which an LED string (e.g., LED
string 1322) may receive any of an analog and/or a digitally controlled current signal.
[0146] In time slot 1522, for example, processor 1304 may command LED string 1322 to conduct
a percentage (e.g., 100%) of the maximum available current by causing a maximum magnitude
of bias current from a corresponding DC stage (e.g., DC stage 1340) to be conducted
by LED string 1322. It should be noted that since LED string 1322 receives a maximum
bias current magnitude in time slot 1522 and since time slot 1522 is the same duration
as time period 1520, the average amount of current conducted by LED string 1322 over
multiple time periods 1520 is substantially equal to all of the maximum current available
from DC stage 1340.
[0147] It should be further noted that current conducted by LED string 1322 in time slot
1522 may be modulated (e.g., pulse width modulated) to further reduce the average
amount of current conducted overtime. As discussed above, for example, any one of
256 duty cycle selections may be made by processor 1304 such that the amount of current
conducted by LED string 1322 in time slot 1522 may be further reduced on average by
the duty cycle selection of control signal 1354.
[0148] As per an alternate example, DC stage 1340 may be commanded to a current magnitude
of 1.2A, but each of LED strings 1322, 1380 and 1324 may only require 0.4A on average
via appropriate PWM control of their associated power switches (e.g., FETs 1350, 1352
and 1386, respectively) to operate at their respective commanded intensity. In such
an instance, 1.2A may be conducted instantaneously by any one LED string 1322, 1380
and 1324 at a time (e.g., only one of LED strings 1322, 1380 and 1324 may be conductive
at any given time), but through time division multiple access (TDMA) control, each
LED string may be operating at 33% duty cycle to receive only the required 0.4A on
average to operate at its commanded intensity. It should be noted that through analog
and/or digital current control and proper time division multiple access to such controlled
current, any one LED string may operate at any intensity (e.g., 0-100%) at any given
time (e.g., any one LED string may be conductive to the mutual exclusion of all of
the other LED string conductivity states) to operate on average at the commanded intensity.
[0149] Turning to FIG. 16, indoor horticultural system 1600 is exemplified, which may include
a horticultural lighting system (e.g., horticultural lighting fixtures 1604-1612 as
exemplified by the lighting fixtures of FIGs. 1, 9, 10, 11 and/or 13) each implementing
any number of wired control topologies (e.g., DMX, I2C, Ethernet, USB, DALI, etc.)
and/or any number of wireless control topologies (e.g., Wi-Fi, thread-based mesh,
Bluetooth, ZigBee, etc.) that may be utilized to control, for example, intensity,
color temperature and/or color spectrum as well as any other attribute of light that
may be emitted by the horticultural lighting fixtures.
[0150] Indoor horticultural system 1600 may also contain any number of area sensors (e.g.,
sensors 1674-1677), which may be used to detect, for example, occupancy, room temperature,
humidity, etc. and may provide an associated status signal (e.g., thread-based mesh
network status signal) that may be indicative of the sensors' status (e.g., temperature
reading, humidity level, motion detection, etc.). Plant-based sensors may also be
paired with each plant of the grow bed (e.g., plant/sensor pairs 1630/1631 through
1646/1647) so that parameters (e.g., temperature, humidity, light intensity, color
temperature, spectral content, moisture, pH, canopy height, etc.) may be sensed for
each plant, or group of plants, and reported at regular time intervals via an associated
status signal (e.g., thread-based mesh network status signal). It should be noted
that each sensor of FIG. 16 may include a computing module (not shown), which may
be used to administer communications, conduct sensor measurements and sensor measurement/status
reporting and whose operational power may be derived from a solar cell (not shown)
and/or internal battery (not shown).
[0151] Indoor horticultural system 1600 may also include nutrient distribution 1654 that
may provide the nutrients and water that may be required by each plant of each grow
bed(s). Nutrient distribution may be implemented as a closed-loop system, whereby
nutrients and water may be extracted from their respective storage containers (not
shown) and mixed to proper proportions. Once properly mixed, the nutrient solution
may be pumped (e.g., at a monitored flow rate) into hydroponic flood benches and/or
trough benches (not shown) to be delivered for consumption by each plant of each grow
bed that may be contained within indoor horticultural system 1600. Any unused nutrient
solution retrieved from nutrient distribution 1654 may be collected, filtered and
prepared to be recirculated to the hydroponic flood benches and/or trough benches.
Nutrient distribution 1654 may also include sensors (not shown), which may be used
to test the collected nutrient flow for any deficiencies and subsequently reported
as additional status information which may then be used to adjust (e.g., automatically
via master controller 1688) the nutrient/water content for optimized growth of the
associated plants in the associated grow beds.
[0152] As shown, indoor horticultural system 1600 may include lighting systems that may
be included within any facility that may exhibit structural components such as walls
(not shown) and ceilings (e.g., ceiling 1696). Each of the lighting fixtures, sensors
and associated control elements of indoor horticultural system 1600, therefore, may
be deployed within such structural components of the facility as a fixed or permanent
asset.
[0153] For example, light controller 1692 may be deployed within ceiling 1696 as a fixed
asset within indoor horticultural system 1600. Light controller 1692 may, for example,
include a DMX master controller (not shown) that may receive wireless commands (e.g.,
from master controller 1688) and in response, may control the desired intensity of
each horticultural light fixture 1604-1612 (e.g., each LED array of each horticultural
light fixture 1604-1612) accordingly. In one embodiment, for example, each LED array
of each horticultural light fixture 1604-1612 may exist within the same DMX universe
and may be responsive to an 8-bit intensity control word received within its uniquely
designated DMX slot from light controller 1692.
[0154] Other fixed assets within indoor horticultural system 1600 may include, for example,
horticultural lighting fixtures 1604-1612 and their associated height control mechanisms
(e.g., winch mechanisms that may control the length of cable assemblies 1602). Cable
assemblies 1602, for example, may be controlled by a height controller (e.g., height
controller 1652) that may be used to raise and lower horticultural lighting fixtures
1604-1612 in accordance with the canopy height of the associated plants (e.g., as
may be reported by plant/sensor pairs 1630/1631 to 1646/1647 to master controller
1688). For example, as the plants grow taller, it may be necessary to raise the associated
horticultural lighting fixtures 1604-1612 in relation to the extended height of the
associated plant canopies.
[0155] In one embodiment, each of the horticultural lighting fixtures and associated sensors/controllers
of indoor horticultural system 1600 may be interconnected wirelessly (e.g., via a
thread-based mesh network). Accordingly, for example, indoor horticultural system
1600 may be implemented as a wireless personal area network (WPAN) utilizing a physical
radio layer (e.g., as defined by the IEEE 802.15.4 communication standard). As such,
the thread-based mesh network may utilize an encapsulation and header compression
mechanism (e.g., 6LoWPAN) so as to allow data packets (e.g., IPv6 data packets) to
be sent and received over the physical radio layer. Messaging between each device
within indoor horticultural system 1600 may be implemented using a messaging protocol
(e.g., user datagram protocol (UDP)), which may be preferred over an alternative protocol
such as the transmission control protocol (TCP).
[0156] In addition, each device may use an application layer protocol for delivery of the
UDP data packets to each device. Such application layer protocols may include the
Constrained Application Protocol (CoAP), Message Queue Telemetry Transport (MQTT)
or the Extensible Messaging and Presence Protocol (XMPP) within the thread-based mesh
network as contrasted with the Hypertext Transport Protocol (HTTP) as may be used,
for example, within Internet 1684. CoAP, for example, may be more conducive for use
by the thread-based mesh network, rather than HTTP, due to the smaller packet header
size required by CoAP, which may then yield smaller overall packet sizes required
by the components of indoor horticultural system 1600 interconnected by the thread-based
mesh network.
[0157] In operation, some components (e.g., horticultural lighting fixtures 1604-1612) interconnected
by the thread-based mesh network of FIG. 16 may be connected to an alternating current
(AC) source that may be used throughout the facility for use with other components
requiring AC power for operation, such as heating, ventilation and air conditioning
(HVAC) systems, air circulators, humidifiers/dehumidifiers and CO
2 dispensing systems 1694. Furthermore, operational power derived from the AC source
may be further controlled (e.g., via relays) so as to be compliant with, for example,
the Energy Star® standard for energy efficiency as promulgated jointly by the Environmental
Protection Agency (EPA) and the Department of Energy (DOE).
[0158] In one embodiment, device 1686 may be used to manually operate indoor horticultural
system 1600 wirelessly (e.g., through the use of a thread-based mesh network). For
example, device 1686 may send a control signal to light controller 1692 via the thread-based
mesh network to cause one or more horticultural lighting fixtures 1604-1612 to illuminate
in accordance with a particular light prescription (e.g., intensity, color temperature
and/or color spectrum) as may be contained within database 1690. Alternately, device
1686 may send a control signal to height controller 1652 via the thread-based mesh
network so as to cause the height between one or more horticultural lighting fixtures
1604-1612 to change with respect to a height of the one or more plant canopies contained
within indoor horticultural system 1600. In alternate embodiments, master controller
1688 may completely automate the operation of indoor horticultural system 1600 by
accessing grow recipes from database 1690, which may then be used to control the lighting
in a specific manner to produce a specific effect (e.g., modify the intensity, color
temperature and/or color spectrum of each of horticultural lights 1604-1612 to simulate
a rising sun, a midday sun and a setting sun in direction 1698 from east to west).
[0159] Indoor horticultural system 1600 may, for example, be sensitive to control signals
as may be provided by controlling entities (e.g., external BACnet network 1682) that
may exist external to the thread-based mesh network of FIG. 16. As per an example,
one or more entities within indoor horticultural system 1600 may be BACnet enabled,
which may allow communication with a BACnet enabled border router (e.g., master controller
1688). In such an instance, control signals bound for indoor horticultural system
1600 may be transmitted by external BACnet network 1682 via Internet 1684 and propagated
throughout indoor horticultural system 1600 via master controller 1688. Conversely,
status information related to indoor horticultural system 1600 may be gathered by
master controller 1688 and may then be disseminated to external BACnet network 1682
via Internet 1684. Accordingly, many grow facilities as exemplified by FIG. 16 may
exist and may be geographically dispersed and remotely controlled via external BACnet
network 1682.
[0160] Each of horticultural light fixtures 1606-1612 may, for example, generate relatively
wide beam patterns (e.g., beam patterns 1615-1621, respectively) that may be produced
by a particular LED/lens combination (e.g., the LED/lens combination as discussed
above in relation to FIG. 6), which may produce maximum intensity at the edges of
the beam pattern. Accordingly, for example, the resulting light distribution (e.g.,
the light distribution of FIG. 7A) may produce a uniform illuminance onto a plant
canopy directly below each of horticultural light fixtures 1606-1612 (e.g., uniform
illuminance distributions 1622-1628) while producing relatively equal intensities
on adjacent plants. In alternate embodiments, illuminance distributions 1622-1628
may increase as the angle of incidence increases with respect to the optical axis
of illuminance distributions 1622-1628.
[0161] As an example, horticultural light 1606 may produce a uniform illuminance, or an
increasing illuminance from centerbeam outward (e.g., illuminance 1622) onto a plane
that may be defined by the canopy of plant 1632 due to the increasing intensity of
light at increasing angles with respect to the optical axis of horticultural light
1606. Since the intensity of light generated by horticultural light 1606 is greatest
at the edges of light distribution 1615, plants 1630 and 1634 may receive a substantially
equal intensity of light as received by plant 1632 from horticultural light 1606 owing
to the effects of the inverse square law as discussed above. In such an instance,
each plant may not only receive a uniform illuminance, or an increasing illuminance
from centerbeam outward, onto its canopy by an associated horticultural light fixture,
but may also receive substantially equal intensities of light on the sides of the
plant by adjacent horticultural light fixtures, thereby more correctly simulating
sunlight, since light is being received by each plant from multiple angles. It should
be noted that horticultural light fixtures 1604-1612 may be arranged not only as a
linear-array, but as a two-dimensional array (e.g., arranged along rows and columns)
such that each plant may receive light from its associated horticultural light fixture
and adjacent horticultural light fixtures at all angles formed from a 360-degree light
distribution (e.g., each plant may receive a substantially uniform cone of light from
its associated and adjacent horticultural light fixtures).
[0162] Plants on the edge of each grow bed (e.g., plants 1630 and 1646) may receive light
from their associated horticultural lighting fixtures configured at angles that are
different than the angles of horticultural lighting fixtures 1606-1612. For example,
horticultural lighting fixtures 1604 and 1605 may be angled (e.g., via height controller
1652 and associated cable assemblies 1602) as shown to direct light onto their associated
plants (e.g., plants 1630 and 1646, respectively) as well as the adjacent plants (e.g.,
plants 1632 and 1644, respectively). In addition, each of horticultural light fixtures
1604-1605 may, for example, generate relatively narrow beam patterns (e.g., beam patterns
1613-1614, respectively) that may be produced by a particular LED/lens combination
(e.g., the LED/lens combination as discussed above in relation to FIG. 3), which may
similarly produce maximum intensity at the edges of the beam pattern as discussed
above in relation to FIGs. 4A and 4B so as to illuminate adjacent plants (e.g., 1632
and 1644, respectively) with substantially the same intensity as associated plants
1630 and 1632, respectively.
[0163] In alternate embodiments, each of horticultural light fixtures 1604-1612 may, for
example, generate relatively wide beam patterns (e.g., beam patterns 1613-1621, respectively)
that may be produced by bare LEDs (e.g., standard LED packages producing a Lambertian
beam pattern without an associated lens) where each bare LED may be mounted at varying
angles with respect to one another. In such an instance, for example, a first bare
LED may be mounted within a light fixture (e.g., light fixture 1606) such that the
optical axis of the first LED may align with a light distribution (e.g., light distribution
1622) that may be directed toward a target (e.g., plant 1632). Second and third bare
LEDs may alternately be mounted within a light fixture (e.g., light fixture 1606)
at opposing angles such that the optical axes of the first and second bare LEDs may
align with the edges of a light distribution (e.g., light distribution 1615). For
example, a second bare LED may be mounted within light fixture 1606 such that its
optical axis may be directed at its respective target (e.g., plant 1630) and a third
bare LED may be mounted within light fixture 1606 such that its optical axis may be
directed at its respective target (e.g., plant 1634). Accordingly, light fixture 1606
may, for example, not only provide direct lighting to plant 1632, but may also provide
cross-lighting for adjacent plants 1630 and 1634 without the use of lenses that may
optically vary the light distributed by light fixture 1606.
[0164] Turning to FIG. 17, a schematic diagram of a lighting system is exemplified, whereby
the forward voltage of one or more LEDs of an LED string (e.g., LED string 1732) of
a light fixture (e.g., master light fixture 1722) may be utilized as a relatively
low-current power supply for auxiliary purposes (e.g., to provide a 0-10V dimming
controller without the need for a dedicated 0-10V controller power supply). For example,
the forward voltage of several LEDs (e.g., two LEDs 1702) may combine in series to
form a cumulative forward voltage equal to the sum of the individual forward voltage
of each LED (e.g., 2*6 = 12 volts at node 1734) and may be used as an auxiliary supply
voltage. The impedance of a rheostat (e.g., potentiometer 1704) may be selected such
that very little current may be derived from the LED string at node 1734 while allowing
a variable voltage to be selected manually (e.g., by an operator in control of potentiometer
1704) and applied to the non-inverting input of operational amplifier 1710. In one
embodiment, switch 1708 may be implemented as a removable, hard-wired selector (e.g.,
PCB jumper) that may allow the wiper voltage of potentiometer 1704 to be applied to
operational amplifier 1710.
[0165] In operation, operational amplifier 1710 may seek to maintain the voltage at its
inverting input substantially equal to the voltage at its non-inverting input through
operation of negative feedback applied to its inverting input as shown. As such, the
conductive state of transistor 1728 may be selected by operational amplifier 1710
(e.g., through selection of the voltage, V
b, applied to the base terminal of transistor 1728) such that the voltage at node 1726
(e.g., a 0-10V control voltage, V
CTRL) may be maintained to be proportional to the voltage selected by potentiometer 1704
(V
POT) according to voltage follower equation (1):

where R
1720 is the resistance magnitude of resistor 1720 and R
1712 is the resistance magnitude of resistor 1712. Writing V
CTRL in terms of the current (I
1728) conducted by transistor 1728:

where R
1714 is the resistance magnitude of resistor 1714 and V
EB is the emitter-base voltage of transistor 1728 and combining equation (1) with equation
(2):

it can be seen from equation (3) that the magnitude of current conducted by transistor
1728, I
1728, may be directly dependent upon the base voltage, V
b, of transistor 1728 as applied by operational amplifier 1710. Turning back to equation
(1), the voltage at node 1726 (V
CTRL) follows the voltage selected by potentiometer 1704 (V
POT) as modified by the gain constant (1+R
1720/R
1712) and the current conducted by current sink 1718 may be adjusted (e.g., increased)
by adjusting (e.g., decreasing) the base voltage, V
b, of transistor 1728 via operational amplifier 1710. As the voltage at node 1726,
V
CTRL, decreases below a threshold voltage magnitude, shunt transistor 1736 may be utilized
to shunt the voltage at node 1726, V
CTRL, to a reference voltage (e.g., the collector-emitter voltage of transistor 1736 referenced
to ground potential) so as to extend the voltage control range at node 1726 below
that which may be accommodated by transistor 1728.
[0166] Master light fixture 1722 (e.g., via 0-10V driver 1730) and slave light fixtures
1724 may be configured with 0-10V drivers that may source current into node 1726 and
may derive their intensity control signal, V
CTRL, from node 1726 as well. As the number of slave light fixtures 1724 increases, so
may the current magnitude conducted by current sink 1718. Through operation of equation
(3) as discussed above, it can be seen that an increase in current conducted by current
sink 1718 (e.g., as may be required through the addition of slave light fixtures 1724
and master light fixture 1722) may be accommodated by a corresponding decrease in
base voltage, V
b. Accordingly, the number of slave light fixtures and master light fixture that may
be accommodated by current sink 1718 may be directly proportional to the current conduction
capability of current sink 1718. In one embodiment, for example, the current conduction
capability of current sink 1718 may be selected to be approximately 50 mA, which may
then accommodate up to 99 slave light fixtures (and one master light fixture 1722),
such that up to 100, 0-10V drivers may each source 500 uA of current into node 1726.
[0167] In an alternate embodiment, switch 1708 (e.g., a PCB jumper) may be selected such
that a wireless control module (e.g., wireless control 1706) may instead control the
voltage at the non-inverting input of operational amplifier 1710, which may then control
the voltage at node 1726, V
CTRL, as discussed above. It can be seen, therefore, that the intensity of multiple lights
within an indoor horticultural system (e.g., horticultural lights 1604-1612 of indoor
horticultural system 1600 of FIG. 16) may be controlled by a light controller (e.g.,
light controller 1692 of FIG. 16) operated either through manual control (e.g., potentiometer
1704) or through wireless control (e.g., wireless control 1706) such that all horticultural
lights 1604-1612 may be operated at substantially equal intensities via a single control
input.
[0168] Turning to FIG. 18, an alternate embodiment of agricultural light fixture 1800 is
exemplified whereby arrays of LEDs may not be arranged in columns or rows, but may
instead be arranged in clusters of between about 2-10 LEDs per cluster (e.g., groups
of 3-4 LEDs in each cluster 1802 and 1812). Each cluster of agricultural light fixture
1800 may, for example, include any combination of color spectrum LEDs and/or color
temperature LEDs. Further, each individual LED in each cluster of agricultural light
fixture 1800 may exist within its own LED string, or conversely, may share an LED
string with one or more other LEDs in the same cluster.
[0169] As per one example, a cluster (e.g., cluster 1812) may be comprised of four LEDs
(e.g., LEDs 1804, 1806, 1808 and 1810), whereby LED 1804 may exist within a first
LED string (e.g., LED string 1322 of FIG. 13), LED 1806 may exist in a second LED
string (e.g., LED string 1380 of FIG. 13) and LEDs 1808-1810 may exist in a third
LED string (e.g., LED string 1324 of FIG. 13). The remaining clusters of agricultural
light fixture 1800 may be similarly configured, whereby for example, one such cluster
1802 may include LED 1814 that may exist within the same LED string as LED 1804, LED
1816 that may exist within the same LED string as LED 1806 and LEDs 1818-1820 that
may exist within the same LED string as LEDs 1808-1810.
[0170] LED 1804 may, for example, be implemented with an LED having a specific color spectrum
(e.g., blue) or a specific color temperature (e.g., 6500K), LED 1806 may, for example,
be implemented with an LED having a specific color temperature (e.g., 3000K white
LED) and LEDs 1808-1810 may, for example, be implemented with LEDs having a specific
color spectrum (e.g. red). As discussed above, the remaining clusters within agricultural
light fixture 1800 may be similarly configured, whereby for example, LED 1814 may,
for example, be implemented with an LED having the same specific color spectrum or
the same specific color temperature as LED 1804, LED 1816 may, for example, be implemented
with an LED having the same specific color temperature as LED 1806 and LEDs 1818-1820
may, for example, be implemented with LEDs having the same specific color spectrum
as LEDs 1808-1810.
[0171] In one embodiment, the number of LEDs that may exist within any given LED string
may be chosen such that the combined forward voltage of any one LED string is substantially
equal to the combined forward voltage of the remaining LED strings. As per one example,
LEDs 1804, 1814 and the remaining LEDs in similar positions within the remaining clusters
of agricultural light fixture 1800 (e.g., the upper left-hand corner of each cluster)
may exist within the same LED string (e.g., LED string 1322 of FIG. 13) where the
LED string may exhibit a combined forward voltage equal to the product of the number
of LEDs in the LED string (e.g., 45 clusters with one LED per cluster equals 45 LEDs)
and the forward voltage of each LED (e.g., 3 volts) for a combined forward voltage
approximately equal to 45*3 = 135 volts.
[0172] As per another example, LEDs 1808-1810 and the remaining LEDs in similar positions
within the remaining clusters of agricultural light fixture 1800 (e.g., the lower
row of each cluster) may exist within the same LED string (e.g., LED string 1324 of
FIG. 13) where the LED string may exhibit a combined forward voltage equal to the
product of the number of LEDs in the LED string. However, since the forward voltage
of each LED in LED string 1324 may be different (e.g., 2 volts) than the forward voltage
of LEDs in the other LED strings, an increased number (e.g., 67-68 LEDs) for a combined
forward voltage approximately equal to 67*2 = 134 volts or 68*2 = 136 volts may be
utilized. In addition, since a higher number of clusters (e.g., 45) exist than are
needed to accommodate two LEDs per cluster, some of the clusters may include only
a single, 2-volt LED. In such an instance, those clusters exhibiting only a single,
2-volt LED may be symmetrically arranged within the array of clusters of agricultural
light fixture 1800 (e.g., every other cluster may exhibit a single, 2-volt LED).
[0173] As discussed in more detail below, each cluster of agricultural light fixture 1800
may include an optical puck (e.g., optical puck 1950 as exemplified in the top orthographic
view of FIG. 19B and the bottom orthographic view of FIG. 19C) that may provide an
optical lens for each LED in each cluster having between about 2-10 LEDs per cluster
(e.g., 4 optical lenses 1952 per cluster as exemplified in FIG. 19B). Each optical
lens 1952 of optical puck 1950 may, for example, provide optical characteristics (e.g.,
optical characteristics as discussed above in relation to FIGs. 3-4 and/or 6-7), but
may be arranged differently (e.g., as compared to the lens arrays as discussed above
in relation to FIGs. 2A and 2B). Instead, the LED/lens pairs of agricultural light
fixture 1800 may be arranged in groups of about 2-10 LED/lens pairs (e.g., 4 LED/lens
pairs), each LED of which may be in electrical communication with one or more LEDs
of the remaining LED/lens pairs as discussed above.
[0174] As discussed in more detail below, cover 1822 may be disposed in relation to agricultural
light fixture 1800 such that each optical puck may protrude through apertures disposed
within cover 1822 (e.g., aperture 1824), such that no further optical treatment (e.g.,
sheet lens) may be applied to the light generated from each cluster beyond the optical
treatment provided by each lens of each optical puck. Accordingly, increased efficiency
(e.g., between about 6-12% increased efficiency) may be achieved by eliminating the
use of a sheet lens.
[0175] Turning to FIG. 19A, orthographic view 1900 of a portion of agricultural light fixture
1800 of FIG. 18 is illustrated, with the cover (e.g., cover 1822 of FIG. 18) removed
to expose the inner rib architecture. In particular, multiple ribs (e.g., ribs 1904
and 1916-1922) may extend approximately the length of agricultural light fixture 1800
and may support multiple PCBs (e.g., PCBs 1902 and 1908-1914) that may be disposed
upon ribs ribs 1904 and 1916-1922, respectively, and may also extend approximately
the length of agricultural light fixture 1800. As illustrated, each rib (e.g., rib
1904) may, for example, support a PCB (e.g., PCB 1902) that may include multiple optical
pucks (e.g., optical pucks 1906), each optical puck including multiple (e.g., 3-4)
lenses. Clusters of LEDs (not shown) may be disposed below each optical puck (e.g.,
LEDs may be disposed within indented portions 1954 of optical puck 1950 as exemplified
in FIG. 19C), such that each lens of each optical puck may be disposed in relation
to each corresponding LED of each cluster. As per one example, each LED and corresponding
lens of each LED/lens pair may be disposed in relation to one another as discussed
above (e.g., as exemplified in relation to LED 306/lens 314 of FIG. 3 and LED 606/lens
614 of FIG. 6).
[0176] PCB 1902 may include electrically conductive traces (not shown), such that each LED
of each cluster may be electrically connected to each corresponding LED of each remaining
cluster on PCB 1902. Furthermore, corresponding LEDs of the remaining clusters of
the remaining PCBs (e.g., PCBs 1908-1914) may be electrically interconnected to form
multiple LED strings (e.g., LED strings 1322, 1380 and 1324 as discussed above in
relation to FIG. 13), whereby each LED string may exhibit a combined forward voltage
that may be substantially equal as discussed above. Each LED string may then be illuminated
on command as discussed above (e.g., as in relation to FIG. 13 and 15).
[0177] Heat generated by illumination of the LEDs of the clusters of agricultural light
fixture 1800 mounted to each of PCBs 1902 and 1908-1914 may be conducted away from
PCBs 1902 and 1908-1914 by the corresponding ribs 1904 and 1916-1922, respectively.
Accordingly, panel 1924 may receive the heat conducted by each of ribs 1904 and 1916-1922
by virtue of the conductive path implemented by each rib to panel 1924. Additionally,
an electrically insulative, thermally conductive layer (e.g., a polyester film not
shown) may exist to conduct heat to panel 1822). The conducted heat may then be removed
from agricultural light fixture 1800 by convection through circulation of air past
panel 1924 and cover 1822. In addition, ribs 1904 and 1916-1922 may provide considerable
structural support within agricultural light fixture 1800, such that in operation
(e.g., agricultural light fixture 1800 is inverted as compared to the position shown),
panel 1924 may provide a storage surface, or shelf, upon which utility articles may
be stored while agricultural light fixture 1800 operates within its associated agricultural
facility.
[0178] Each optical puck may include a trough (e.g., trough 1926 of FIG. 19B), within which
a compressible device (e.g., an O-ring not shown) may be installed, such that once
the panel (e.g., panel 1822 of FIG. 18) encloses agricultural light fixture 1800,
panel 1822 may engage each O-ring of each optical puck to seal the interior of agricultural
light fixture 1800 from contaminants (e.g., water, rain, dust, oil, etc.). In addition,
gasket 1928 may be utilized to compress against panel 1822 to further protect agricultural
light fixture 1900 from external contaminants (e.g., in accordance with the International
Electrotechnical Commission Ingress Protection 66 (IP66) standard of protection).
[0179] Turning to FIG. 20, alternate embodiments of lighting fixtures are exemplified, in
which bare LEDs (e.g., LEDs without optically varying lenses) may be positioned to
project a substantially even target illuminance across a flat surface, or conversely,
to project an illuminance onto a flat surface that increases as the angle increases
between the lighting fixture and the flat surface. In particular, LEDs exhibiting
varying beam angles, but without optical lenses, may be utilized within agricultural
lighting fixtures 2002 and 2022, whereby LED arrays (e.g., LED arrays 2006, 2010,
2014) may exist within agricultural lighting fixture 2002 (e.g., on panels 2004, 2008
and 2012, respectively) and LED arrays (e.g., LED arrays 2026, 2030 and 2034) may
exist within within agricultural lighting fixture 2022 (e.g., on panels 2024, 2028
and 2032, respectively) to project illumination beam widths 2016, 2018, 2020 from
agricultural lighting fixture 2002 and to project illumination beam widths 2036, 2038
and 2040 from agricultural lighting fixture 2022.
[0180] As exemplified in FIG. 20, the illumination projected by LED arrays 2010 and 2030
may exhibit wider beam patterns (e.g., greater than 120 degree FWHM) as compared to
the narrower beam patterns (e.g., less than 90 degree FWHM) projected by LED arrays
2006, 2014, 2026 and 2034. Accordingly, the beam patterns projected by LED arrays
2006 and 2014 may overlap with the beam pattern projected by LED array 2010 at overlap
portions 2052 and 2054, respectively. Similarly, the beam patterns projected by LED
arrays 2026 and 2034 may overlap with the beam pattern projected by LED array 2030
at overlap portions 2056 and 2058, respectively.
[0181] In addition, the area of overlap portions 2052 and 2054 on surface 2050 may be increased
or decreased depending upon the angle at which LED arrays 2006 and 2014 are projecting
light with respect to LED array 2010. Similarly, the area of overlap portions 2056
and 2058 on surface 2050 may be increased or decreased depending upon the angle at
which LED arrays 2026 and 2034 are projecting light with respect to LED array 2030.
[0182] It can be seen, for example, that by decreasing angles 2042 and 2044, the area of
overlap portions 2052 and 2054 increases. Similarly, for example, by decreasing angles
2046 and 2048, the area of overlap portions 2056 and 2058 increases. Accordingly,
the amount of cross-lighting produced by the agricultural lighting fixtures of FIG.
20 may be increased or decreased, which may in turn increase or decrease the illuminance
projected onto surface 2050. As such, illuminance variations may be effected without
the use of optically varying lenses.
[0183] Turning to FIG. 21, cooling aspects of agricultural light fixture 2100 (e.g., light
fixture 100 of FIG. 1) are exemplified. Fan 2108 may, for example, draw external air
2102 into an interior of agricultural light fixture 2100 and may further cause the
drawn air to travel in direction 2104 within agricultural light fixture 2100. As the
drawn air travels within agricultural light fixture 2100, heat may be extracted from
within agricultural light fixture 2100 by convection and expelled via exhaust port
2110 as expelled air flow 2106. Accordingly, expelled air flow 2106 may be expelled
from within agricultural light fixture 2100 in a direction opposite to the optical
axis of agricultural light fixture 2100 (e.g., optical axis 2112).
[0184] It can be seen, therefore, that if agricultural light fixture 2100 were applied to
an indoor horticultural system (e.g., as lights 1604-1612 of indoor horticultural
system 1600 of FIG. 16), expelled air may be directed toward ceiling 1696 away from
plants 1630-1646. By directing the expelled air away from plants 1630-1646, any excess
heat that may affect leaf temperature and potentially the reduction of transpiration
of the leaves closest to agricultural light fixture 2100 may be mitigated.
[0185] Turning to FIG. 22, cooling aspects of agricultural light fixture 2200 (e.g., light
fixture 900 of FIG. 9) are exemplified. Fan 2212 may, for example, draw external air
2202 into an interior of agricultural light fixture 2200 and may further cause the
drawn air to travel in directions 2204 and 2206 within agricultural light fixture
2200. As the drawn air travels within agricultural light fixture 2200, heat may be
extracted from within agricultural light fixture 2200 by convection and expelled via
exhaust ports 2214 and 2216 as expelled air flows 2210 and 2208, respectively. Accordingly,
expelled air flows 2210 and 2208 may be expelled from within agricultural light fixture
2200 in a direction opposite to the optical axis of agricultural light fixture 2200
(e.g., optical axis 2218).
[0186] It can be seen, therefore, that if agricultural light fixture 2200 were applied to
an indoor horticultural system (e.g., as lights 1604-1612 of indoor horticultural
system 1600 of FIG. 16), expelled air may be directed toward ceiling 1696 away from
plants 1630-1646. By directing the expelled air away from plants 1630-1646, any excess
heat that may affect leaf temperature and potentially the reduction of transpiration
of the leaves closest to agricultural light fixture 2200 may be mitigated.
[0187] Other aspects and embodiments of the present invention will be apparent to those
skilled in the art from consideration of the specification and practice of the invention
disclosed herein. It is intended, therefore, that the specification and illustrated
embodiments be considered as examples only, with a true scope of the invention being
indicated by the following claims.