BACKGROUND OF THE INVENTION
1. Technical Field
[0001] The present invention relates generally to driving LEDs, and more particularly to
a method of driving LED chips of same power but different rated voltages and currents.
2. Description of Related Art
[0002] Typically, a LED (light-emitting diode) device includes a LED chip and a driving
apparatus, wherein the driving apparatus provides power to the LED chip. There are
various types of LED chips in the current market, and LED chips of different specifications
may respectively have different rated voltage and rated current, even for those of
the same power. For example, a LED chip of 28W is probably to have the following combinations
of rated voltage and rated current: 80V/350mA, 56V/500mA, 40V/700mA, etc. Conventionally,
a driving apparatus merely fits one specific specification, and therefore could drive
only LED chips of the same specification. Thus, since there are all kinds of LED chips
of different specifications, the inventory pressure of driving apparatuses is high
for manufacturers. And given that manufacturers have to produce driving apparatuses
to drive LED chips of as many specifications as possible, the quantities of each type
of driving apparatus is limited, and therefore the price and the manufacturing cost
is unlikely to be lowered. If a driving apparatus able to drive LED chips of same
power but different rated voltages and different rated currents can be provided, the
inventory pressure and the manufacturing cost of driving apparatuses will be effectively
reduced.
BRIEF SUMMARY OF THE INVENTION
[0003] In view of the above, the primary objective of the present invention is to provide
a method of driving LED chips of same power but different rated voltages and currents,
which is able to maintain the power provided to the LED chips within a predetermined
range.
[0004] The method of driving LED chips of same power but different rated voltages and currents
provided in the present invention includes the following steps: set a predetermined
power; provide a LED chip which has a rated power accordant to the predetermined power;
obtain a working current of the LED chip while the LED chip is operated at the predetermined
power; provide a driving current to the LED chip, and maintain the driving current
the same as the working current.
[0005] Whereby, LED chips of the same power but different rated currents and voltages can
be driven with the method provided in the present invention, and the power provided
to the LED chips can be maintained within the predetermined range. The method effectively
improves the inconveniences due to the conventional way that one kind of driving apparatus
only drives LED chips of the same specification.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0006] The present invention will be best understood by referring to the following detailed
description of some illustrative embodiments in conjunction with the accompanying
drawings, in which
FIG. 1 is a block diagram of a first preferred embodiment of the present invention;
FIG. 2 is a flow chart of the first preferred embodiment of the present invention;
FIG. 3 is a block diagram of a second preferred embodiment of the present invention;
and
FIG. 4 is a block diagram of a third preferred embodiment of the present invention,
showing an alternative way to set the predetermined power.
DETAILED DESCRIPTION OF THE INVENTION
[0007] As shown in FIG. 1, a driving apparatus 1 for driving LED chips of the first preferred
embodiment of the present invention includes an input port 1a, an output port 1b,
a driving unit 10, a voltage measuring unit 20, a current measuring unit 30, a processing
unit 40, and a control unit 50.
[0008] The input port 1a is electrically connected to a power source, and the output port
1b is provided to electrically connect to a LED chip 80. The driving unit 10 is electrically
connected to the input port 1a and the output port 1b. After the LED chip 80 is electrically
connected to the output port 1b, the driving unit 10 receives power from the power
source 70, and outputs a driving voltage and a driving current to the LED chip 80.
The driving unit 10 controllably regulates the driving voltage and the driving current.
In practice, the design of the driving unit 10 could be based on PWM, half-bridge,
buck, or boost circuits.
[0009] The voltage measuring unit 20 is electrically connected to the driving unit 10 and
the output port 1b to detect the driving voltage provided to the LED chip 80 by the
driving unit 10. The current measuring unit 30 is also electrically connected to the
driving unit 10 and the output port 1b to detect the driving current provided to the
LED chip 80 by the driving unit 10.
[0010] The processing unit 40 is electrically connected to the voltage measuring unit 20
and the current measuring unit 30. Also, the processing unit 40 is electrically connected
to the driving unit 10 through the control unit 50. The processing unit 40 transmits
a current controlling signal to the driving unit 10 through the control unit 50 according
to the detection result of the voltage measuring unit 20 and the current measuring
unit 30, and the driving unit 10 is controlled to regulate the driving current accordingly.
[0011] Whereby, a method of driving LED chips can be applied with the aforementioned driving
apparatus 1, wherein the method includes the following steps shown in FIG. 2:
- A. Set a predetermined power in the processing unit 40, wherein the driving apparatus
1 provides a power of the predetermined power.
- B. Connect a LED chip 80 which has a rated power accordant to the predetermined power.
In the first preferred embodiment, the rated power of the LED chip 80 equals the predetermined
power. For example, though the LED chips of specifications of 80V/350mA, 56V/500mA,
and 40V/700mA have different rated voltages and rated currents, they have the same
rated power, which is 28W, and therefore any one of the listed LED chips can be selected
to be the LED chip 80 connected to the driving unit 10. In practice, the rated power
of the selected LED chip 80 is compatible to be in a range between 90% and 110% of
the predetermined power. In other words, for the predetermined power of 28W, the rated
power of the selected LED chip 80 can be in a range between 25.2W and 30.8W.
- C. Measure the LED chip 80 to obtain a working current thereof while the LED chip
80 is operated. In the first preferred embodiment, the LED chip 80 is electrically
connected to the driving unit 10 first, and then the processing unit 40 transmits
the current controlling signal to the driving unit 10 through the control unit 50,
wherein the driving unit 10 is controlled to gradually increases the driving current
provided to the LED chip 80 from an initial current which is lower than the working
current. Meanwhile, the processing unit 40 obtains a product of the driving voltage
and the driving current through the detection of the voltage measuring unit 20 and
the current measuring unit 30, wherein the product is the driving power provided to
the LED chip 80. It is obvious to see that the driving voltage is increased along
with the increasing driving current provided by the driving unit 10. As a result,
the driving power provided to the LED chip 80 is continuously increased as well. Once
the driving power reaches the predetermined power, the driving current stops being
increased, and the driving current at this time point equals the working current required
for achieving the predetermined power.
- D. Transmit the current controlling signal from the processing unit 40 to the driving
unit 10 through the control unit 50, wherein the driving current is controlled to
maintain the driving current the same as the working current, and therefore to provide
the driving power of the predetermined power to the LED chip 80. In this way, the
LED chip 80 is operated at a constant power, which means that the product of the driving
voltage and the driving current is maintained the same as the predetermined power
set in step A.
- E. Maintain the driving power provided to the LED chip 80 within a predetermined range,
wherein the predetermined power is in the predetermined range. In the first preferred
embodiment, the processing unit 40 continuously obtains the driving power, which is
the product of the driving voltage and the driving current, through the detection
results of the voltage measuring unit 20 and the current measuring unit 30. The processing
unit 40 controls the driving unit 10 through the control unit 50 to increase or decrease
the driving current provided to the LED chip 80, in order to maintain the driving
power not to exceed the predetermined range, which is a range between 97% and 103%,
of the predetermined power. Whereby, the driving power provided to the LED chip 80
can be stabilized.
[0012] With the aforementioned method, the driving apparatus 1 is able to measure the connected
LED chip 80 to obtain the working current required for the LED chip 80 to be operated
at the driving power the same as the predetermined power. For any other LED chip of
different rated voltage and different rated current, as long as its rated power is
accordant to the predetermined power, it is compatible to the driving apparatus 1.
[0013] In an embodiment, the method of driving LED chips further includes to maintain the
driving voltage provided to the LED chip 80 no higher than an upper voltage limitation
by transmitting a voltage restriction signal to the driving unit 10 from the processing
unit 40 when the voltage measuring unit 20 detects that the driving voltage exceeds
the upper voltage limitation. Similarly, the method of driving LED chips further includes
to maintain the driving current provided to the LED chip 80 no higher than an upper
current limitation by transmitting a current restriction signal to the driving unit
10 from the processing unit 40 when the current measuring unit 30 detects that the
driving current exceeds the upper current limitation. Whereby, the LED chip 80 or
the driving unit 10 can be protected from being damaged by abnormal driving voltage
or driving current outputted from the driving unit 10.
[0014] In the second preferred embodiment, a plurality of power values are saved in the
processing unit 40 in advance before step A, and the driving apparatus 1 further includes
an input unit 60 electrically connected to the processing unit 40, as shown in FIG.
3. In step A, the predetermined power is set by selecting one of the power values
through the input unit 60. Whereby, the driving apparatus 1 can be further compatible
with LED chips of different rated power. In practice, the design of the input unit
60 can be based on several switches, and a user can set the predetermined power by
simply switching the switches.
[0015] In the third preferred embodiment, the predetermined power can be set in a different
way other than using the input unit 60 as in the second preferred embodiment.
[0016] In more details, the method of the third preferred embodiment stores a reference
voltage in the processing unit 40 in advance before step A.
[0017] A power supplying device 82 shown in FIG. 4 is provided, wherein the processing unit
40 has an output terminal 822, from which an output voltage is outputted.
[0018] The output terminal 822 of the power supplying device 82 is electrically connected
to the output port 1b of the driving apparatus 1.
[0019] The output voltage of the power supplying device 82 is detected by the voltage measuring
unit 20.
[0020] Whereby, when the detected output voltage is higher than or equal to the reference
voltage, the processing unit 40 sets the predetermined power.as a value of the output
voltage.
[0021] In addition, once the predetermined power is set, the output terminal 822 of the
power supplying device 82 is electrically disconnected from the output port 1b of
the driving apparatus 1, and therefore the power supplying device 82 is electrically
disconnected from the driving apparatus 1.
[0022] For example, the reference voltage stored in the processing unit 40 is 30V, while
the predetermined power is 40W. If the user intends to set the predetermined power
as 32W, he/she regulates the output voltage of the power supplying device 82 as 32V,
and then electrically connects the power supplying device 82 to the output port 1b
of the driving apparatus 1. At this time point, the voltage measuring unit 20 detects
that the output voltage is 32V, and since the value is higher than the reference voltage
(30V), the processing unit 40 sets the predetermined power as 32W. In other words,
in the third preferred embodiment, the predetermined power is set by regulating the
output voltage of the power supplying device 82.
[0023] After that, the output terminal 822 of the power supplying device 82 is disconnected
from the output port 1b of the driving apparatus 1, and the aforementioned step B
to step D can be taken as the previous embodiments. As described above, the working
current required to maintain the LED chip 80 being operated at the predetermined power
can be obtained in this way. For any other LED chip of different rated voltage and
different rated current, as long as its rated power is accordant to the predetermined
power value, it is compatible to the driving apparatus 1.
[0024] It is noted that as long as the output voltage of the power supplying device 82 falls
in the detection capability of the voltage measuring unit 20, no matter what value
the predetermined power is required to be, the output voltage can be used to set the
predetermined power. Therefore, the driving apparatus 1 is compatible to LED chips
of different rated powers, and the driving voltage and the driving current required
to be provided to the LED chips can be precisely obtained.
[0025] In practice, the driving apparatus 1 can be electrically disconnected from the power
supplying device 82 after step A and before step C. In other words, such step can
be taken at any time point after the output voltage of the power supplying device
82 is detected, and before the LED chip 80 is electrically connected to the output
port 1b.
[0026] With the method of driving LED chips of same power but different rated voltages and
currents, the driving apparatus is compatible to drive all LED chips of the same rated
power, even though their rated voltages and rated currents are different from each
other, which effectively improves the inconvenience of the conventional way that one
driving apparatus can only drive LED chip of one certain specification.
[0027] It must be pointed out that the embodiments described above are only some preferred
embodiments of the present invention. All equivalent methods which employ the concepts
disclosed in this specification and the appended claims should fall within the scope
of the present invention.
1. A method of driving LED chips of same power but different rated voltages and currents,
comprising the steps of:
A. setting a predetermined power;
B. connecting a LED chip (80) which has a rated power accordant to the predetermined
power;
C. obtaining a working current of the LED chip (80) while the LED chip (80) is operated
at the predetermined power; and
D. providing a driving current to the LED chip (80), and maintaining the driving current
the same as the working current.
2. The method of claim 1, wherein the driving current is provided by a driving apparatus
(1); the predetermined power is set in the driving apparatus (1) in step A for the
driving apparatus (1) to drive the LED chip (80) accordingly.
3. The method of claim 2, wherein a plurality of power values are saved in the driving
apparatus (1), and the predetermined power is set by selecting one of the power values.
4. The method of claim 1, wherein the rated power of the LED chip (80) is in a range
between 90% and 110 % of the predetermined power.
5. The method of claim 1, wherein the working current of the LED chip (80) is obtained
by providing the LED chip (80) with the driving current, which is gradually increased
from an initial current lower than the working current, and measuring the LED chip
(80) to obtain a driving voltage thereof and therefore a product of the driving voltage
and the driving current; once the product reaches the predetermined power, the driving
current is maintained and stopped being increased, and the maintained driving current
equals the working current of the LED chip (80).
6. The method of claim 1, further comprising:
E. regulating the driving current to maintain a driving power provided to the LED
chip (80) within a predetermined range, wherein the predetermined power is in the
predetermined range, and the driving power is a product of the driving current and
a driving voltage provided to the LED chip (80).
7. The method of claim 6, wherein the predetermined range is in a range between 97% and
103% of the predetermined power.
8. The method of claim 1, further comprising maintaining a driving voltage provided to
the LED chip (80) no higher than an upper voltage limitation.
9. The method of claim 1, further comprising maintaining the driving current provided
to the LED chip (80) no higher than an upper current limitation.
10. The method of claim 2, wherein the driving apparatus (1) has an output port (1b) electrically
connected to the LED chip (80) and an output terminal (822) of a power supplying device
(82) respectively; the power supplying device (82) outputs an output voltage via the
output terminal (822); the driving apparatus (1) detects the output voltage of the
power supplying device (82) to set the predetermined power as a value of the output
voltage in step A; once the output voltage is detected, the output terminal (822)
of the power supplying device (82) is electrically disconnected from the output port
(1b) of the driving apparatus (1).
11. The method of claim 10, further comprising setting a reference voltage in the driving
apparatus (1) before step A; the predetermined power is set as the value of the output
voltage if the output voltage is higher than or equals the reference voltage.
12. The method of claim 10, wherein the output terminal (822) of the power supplying device
(82) is electrically disconnected from the output port (1b) of the driving apparatus
(1) before step A.
13. The method of claim 10, wherein the output terminal (822) of the power supplying device
(82) is electrically disconnected from the output port (1b) of the driving apparatus
(1) after step A and before step C.