[0001] The invention relates to providing power to a DALI bus.
[0002] In the past, a separation of a DALI bus power supply and DALI device communication
through the DALI bus was usually present. Abrupt power spikes on the DALI bus resulted
in significant hardware demand on the DALI power supply but had no consequences with
regard to the lighting by the individual DALI devices.
[0003] In a new implementation though, DALI devices with integrated power supply are suggested.
[0004] A DALI power supply delivers a limited output current (e.g. 60mA) that can be used
to supply multiple devices on the DALI bus, where each device draws a maximum current
of 2mA during idle times, in the following also referred to as idle current. A sum
of all idle currents of all devices connected to the DALI bus is referred to as DALI
bus idle current.
[0005] During communication, the DALI bus is short circuited by the communicating DALI device,
which means that the maximum output current (e.g. 60mA), provided by the power supply
flows.
[0006] If there are e.g. 30 further DALI devices connected to the bus, so the power supply
is continuously delivering 60mA during idle times, short circuiting the DALI bus by
the communicating DALI device is not a problem because the load difference between
idle times and communication times is very low (60mA during idle times and also during
communication times).
[0007] If there is on the other hand e.g. only one further DALI device connected to the
bus, the DALI power supply delivers only 2mA during idle times. During communication
times, when the bus is short circuited by the further DALI device, currents of up
to 60mA flow - this means quite heavy dynamic load changes.
[0008] These heavy load changes do not only affect the DALI power supply of the DALI device
but can also be visible as a voltage drop on the 400V bus voltage that is generated
by a power factor correction (PFC) block. This 400V bus voltage is the input voltage
for both - a DALI power supply as well as a LED current source (e.g. half bridge LLC
or buck topology).
[0009] The voltage drop on the bus voltage can be visible in the light output as a light
flicker if the PFC controller and/or the controller of the current source are not
fast enough to compensate the drop. Adjusting these controller settings very quickly
would be desired to avoid potential light flicker - but this introduces other potential
problems and makes the system more complicated as different controller settings are
required depending on the output current and/or working point.
[0011] Accordingly, the object of the invention is to provide a DALI device and a method
for operating a DALI or comparable device, which prevent undesired influence on the
overall power supply, independent of a number of devices connected to the DALI bus.
[0012] "DALI" according to the present invention preferably relates to all buses and devices
in which the bus is designed to have a non-zero DC voltage level in the quiescent
state. Preferably the bus thus can serve also as a power supply, wherein the maximum
power/current is limited.
[0013] The object is solved by the features of claim 1 for the device and claim 12 for the
method. The dependent claims contain further developments.
[0014] An inventive DALI device comprises a DALI power supply. The DALI device is adapted
to be connected to a DALI bus, which is connected to a plurality of further DALI devices.
The DALI power supply is adapted to provide a DALI bus idle current to the DALI bus
during DALI bus idle times, and provide a communication current dependent upon a communication
current input signal to the DALI bus, during DALI communication times. By making the
level of the (DC) communication current adjustable, dynamic load effects are effectively
prevented.
[0015] Preferably, the DALI power supply comprises a current controller, which is adapted
to set the communication current dependent upon the communication current input signal,
a power source, adapted to provide a supply current, and a current limiter, adapted
to limit the supply current to the communication current set by the current controller.
This allows for a very simple implementation.
[0016] Preferably, the DALI bus idle current is a sum of idle currents of all further DALI
devices connected to the DALI bus.
[0017] Moreover, preferably the DALI power supply is adapted to set a communication current
to 1 to 3 times the DALI bus idle current comes preferably to 1,1 to 2 times the DALI
bus idle current, most preferably to 1,2 to 1,5 times the DALI bus idle current. The
lower limitation assures a functioning communication, while the upper limitation limits
the dynamic load shifts.
[0018] Preferably, the DALI power supply comprises a communication current signal input,
adapted to receive a user input of the communication current input signal. This allows
for a very simple setting of the communication current.
[0019] Preferably, the communication current signal input is a switch or a series of switches
or a potentiometer. This further simplifies the construction.
[0020] Alternatively, the DALI power supply comprises a DALI bus sensor, adapted to determine
a voltage indicative of the DALI bus idle current during idle times and indicative
of the communication current during communication times. This idle current then is
the communication current input signal. This allows for a very accurate determining
of the communication current.
[0021] Preferably, the DALI power supply is adapted to, at the beginning of each communication
time, supply a first communication current value to the DALI bus, monitor the DALI
bus voltage, and successively increase the communication current value until the DALI
bus voltage is stable. This adaptive approach allows for an especially accurate setting
of the communication current. Moreover, the iterative nature of this approach limits
dynamic load shifts.
[0022] In a further alternative, the DALI device comprises a DALI communication interface,
adapted to receive the communication current input signal through the DALI bus. This
remote control allows for very flexible operation of the DALI device.
[0023] Advantageously, idle times are times in which all of the further DALI devices connected
to the DALI bus do not communicate through the DALI bus but draw idle current. The
communication times are times in which one of the further DALI devices connected to
the DALI bus short circuits the DALI bus in order to send a communication through
the DALI bus.
[0024] An inventive DALI system comprises a previously described DALI device, a DALI bus,
and a plurality of further DALI devices. The previously described DALI device and
the plurality of further devices are then connected to the DALI bus. This allows for
and especially effective operations.
[0025] An inventive method for operating a DALI device, comprising a DALI power supply,
the DALI device being connected to a DALI bus, connected to a plurality of further
DALI devices, comprises:
- providing a DALI bus idle current to the DALI bus, during DALI bus idle times, by
the DALI power supply, and
- providing a communication current the level of which is dependent upon a communication
current input signal to the DALI bus, during DALI communication times, by the DALI
power supply.
[0026] By making the level of the communication current adjustable, dynamic load effects
are effectively prevented.
[0027] An exemplary embodiment of the invention is now further explained with respect to
the drawings, in which
- Fig. 1
- shows a first exemplary embodiment of the inventive DALI system and a first embodiment
of the inventive DALI device in a block diagram;
- Fig. 2
- shows a detailed construction of a second embodiment of the inventive DALI device;
- Fig. 3
- shows exemplary signals, in a regular DALI device;
- Fig. 4
- shows exemplary signals in a third embodiment of the inventive DALI device;
- Fig. 5
- shows further exemplary signals in a forth embodiment of the inventive DALI device;
- Fig. 6
- shows further exemplary signals in a fifth embodiment of the inventive DALI device,
and
- Fig. 7
- shows an embodiment of the inventive method in a flow diagram.
[0028] First, we demonstrate the construction and function of different embodiments of the
inventive DALI device and the inventive DALI system along Fig. 1 - Fig. 6. Finally,
we describe the function of an embodiment of the inventive method with regard to Fig.
7. Similar entities and reference numbers in different figures have been partially
omitted.
[0029] The idea of this invention is that the heavy load changes that occur during DALI
communication get reduced by a dynamic current limitation. In an exemplary implementation,
the DALI power supply output current is limited by a current sink to a fixed value.
[0030] In case of e.g. only one DALI device being connected to the DALI bus, the DALI power
supply does not need to deliver the full e.g. 60mA. In this case the limitation could
be set to e.g. 5mA (at least >2mA). This would mean that the dynamic load change for
the power supply is reduced (jump only from 2mA to 5mA instead of 2mA to 60mA), and
therefore the drop in the bus voltage and a potential light flicker is reduced / eliminated.
[0031] The dynamic limit could be set either by measuring the DALI power supply output current
in idle state (e.g. 10mA if 5 devices are connected) and then setting the current
limitation to e.g. 150% of this value, or the limit could be set manually by the user
via DALI or another interface (NFC).
[0032] Fig. 1 shows the context of this invention in a principle block diagram. A DALI system
1 comprises a DALI device 2 connected to a DALI bus 3. Moreover, the system 1 comprises
further DALI devices 4, 5 and 6. The number of further DALI devices 4-6 is not limited,
except for the general limitation of connected DALI devices in one DALI string.
[0033] The DALI device 2 comprises a DALI power supply 11. Optionally, it comprises a DALI
communication interface 12 and additional function blocks connected to further operations,
such as illuminating a string of LEDs. It should be noted that the DALI device 2 is
only described in detail with regard to function blocks relevant to the present invention,
but function blocks not relevant to the present invention are not shown or described
in detail. This is not indicative, of these function blocks not being present.
[0034] The DALI device 2 is provided with a mains connection and is connected to the DALI
bus 3. Furthermore, it may be connected to a string of LEDs by a connection LED+/LED-.
[0035] The DALI power supply 11 of the DALI device 2 provides the DALI bus voltage of the
DALI bus 3. Moreover, it can communicate with other devices on the DALI bus 3 on the
DALI bus communication interface 12. With regard to the detailed function, it is referred
to the later elaborations regarding Fig. 2.
[0036] In Fig. 2, a more detailed block diagram of the DALI device 2 is shown. The DALI
device 2 comprises a DALI power supply 11, which again comprises a power source 20,
connected to a current limiter 21, which is moreover connected to a current controller
22. The current controller 22 is moreover optionally connected to a communication
current input 24, a DALI bus sensor 23 and the DALI communication interface 12. The
current limiter 21 is moreover connected to the DALI bus 3, in case of the presence
of the optional DALI bus sensor 23, through the DALI bus sensor 23.
[0037] The power source 20 is connected to a bus voltage V
Bus, which provides not only the input power for the DALI power supply 11, but also the
power for illuminating the connected LED strings.
[0038] The current controller 22 is adapted to receive a communication current input signal
25a, 25b, 25c to determine a communication current therefrom. The value of this communication
current is handed to the current limiter 21, which then limits a current provided
by the power source 20 and provides it to the DALI bus 3 in form of a DALI voltage
V
DALI.
[0039] The current controller 22 therein receives the communication current input signal
either in form of a measured voltage V
meas from the DALI bus sensor 23, which in the most simple form of construction can be
a shunt resistor. The measured voltage V
meas is then indicative of the communication current during communication through the
DALI bus and indicative for the idle current on the DALI bus during idle times. The
voltage V
meas therefore corresponds to the communication current input signal 25b in this case.
[0040] Depending on the topology that is used for the DALI power supply, the measurement/estimation
of the provided current can also be done on the primary side (e.g. if a flyback converter
or other isolated converter is used).
[0041] Another possibility would be to "find" the output current that is required by the
external DALI devices by monitoring the DALI output voltage and slowly increasing
the current limit. The DALI output voltage (VDALI, after the current limiter) is measured
with a voltage divider, then a current limit of e.g. 2mA is set in the beginning which
is slowly increased. When more current is required by the external DALI devices, the
DALI output voltage will increase when the current limit is increased. Once the whole
current that is required is allowed to flow, the DALI output voltage will be stable
- to have some margin the current limit then can further be increased slightly (e.g.
20-50% higher).
[0042] Therein, communication times are times in which one of the further DALI devices 4-6
short circuits the DALI bus 3 in order to perform a communication. Also, idle times
are times in which none of the DALI devices 2, 4-6 connected to the DALI bus short
circuits the DALI bus. During these times, each of the DALI devices 4-6 draws an idle
current of e.g. 2 mA. By measuring the idle current, it is possible to determine the
necessary communication current, limiting the dynamic load shifts significantly.
[0043] In an alternative even simpler construction, the current controller 22 is connected
to the communication current input 24. Through this input 24, the communication current
is directly input as communication current input signal 25a. For example, the input
can be a switch, e.g. a dip switch, by which a user can set the communication current.
In a most simple construction, the switch merely switches between a high and a low
communication current. Especially the high setting could be 20mA to 60mA, preferably
30mA to 60mA. Especially the low setting could be 3mA to 30mA, preferably 5mA to 10mA.
[0044] In a more complex construction manner, a series of switches, e.g. dip switches, can
be used to set a specific communication current value. Also the use of a potentiometer
for setting the communication current is possible. In any of those cases, the input
24 provides a communication current input signal 25a to the current controller 22.
[0045] In a further alternative construction, the current controller 22 receives the communication
current input signal 25c from the DALI communication interface 12, which receives
it as DALI signaling through the DALI bus 3. This allows for a remote control of the
value of the communication current.
[0046] Fig. 3 shows relevant waveforms when the dynamic limitation is not active. In this
case, the load changes on the current drawn from the DALI power supply 11 are very
high, as can be seen as current 30. In case of short circuit (communication) ∼62mA
flow to the output as can be seen as curve 31. During idle times ∼2mA flow. The dynamic
current limitation is not active - so the current 32 is zero. The DALI bus voltage
33 is shown in the lower diagram.
[0047] Fig. 4 shows relevant waveforms for Vlimiter = 7.5V, which corresponds to the communication
current input signal. It can be seen that a current 42 of ∼37mA flow and the output
current 41 varies only between ∼25mA and 2mA - this reduces the load change for current
40. The DALI bus voltage 43 is shown in the lower diagram.
[0048] Fig. 5 shows relevant waveforms for Vlimiter = 11.5V. It can be seen that a current
52 of ∼57mA flows and the output current 51 varies only between ∼6mA and 2mA - this
dramatically reduces the load change for current 50. The DALI bus voltage 53 is shown
in the lower diagram.
[0049] Fig. 6 shows a DC sweep of Vlimiter from 0V to 15V, with a short circuit at the output.
Vlimiter is shown on the x-axis, while the currents are shown on the y-axis. The current
60 corresponds to the currents 40, 50 of Fig. 4 and Fig. 5. The current 61 corresponds
to the currents 41 and 512 of Fig. 4 and Fig. 5. The current 62 corresponds to the
currents 42 and 52 of Fig. 4 and Fig. 5.
[0050] It can be seen how the dynamic current limitation works depending upon the level
of Vlimiter. Low values of Vlimiter lead to high allowed output currents, high values
of Vlimiter lead to low allowed output currents.
[0051] It should be noted that Vlimiter corresponds to the previously mentioned communication
current input signal.
[0052] In Fig. 7, finally an embodiment of the inventive method is shown in a flow diagram.
In a first step 100, a DALI bus idle current is provided to the DALI bus, during DALI
bus idle times. In a second step 101, a communication current is provided to the DALI
bus, dependent upon a communication current input signal.
[0053] It should be noted that the inventive device and method very closely correspond to
each other. Therefore, the elaborations regarding the device are also applicable to
the method.
[0054] The invention is not limited to the examples, and especially not to a specific number
of DALI devices connected to the DALI bus. Also, the invention is not limited to specific
types of DALI devices. Although a DALI device providing LED strings with power is
mentioned, any other type of DALI device can also be employed. The characteristics
of the exemplary embodiments can be used in any advantageous combination.
[0055] The following method can be used to determine the required idle current level:
- at system startup set the current limiter to an initial low idle current value (e.g.
2mA)
- monitor the DALI bus voltage (VDALI in Fig.2)
- increase the current limiter value -> if more idle current is required, VDALI will
increase
- keep increasing the current limiter value until VDALI stays constant (afterwards further
increase the current limiter value to have some reserve)
- > this is now the final current limiter value that will ensure two aspects:
- a) enough current can flow at idle times (to supply the DALI devices)
- b) current at communication times is low enough that the difference between currents
in idle and communication times is low (no dramatic load changes for the PFC)
1. DALI device (2), comprising a DALI power supply (11), wherein the DALI device (2)
is adapted to be connected to a DALI bus (3), connected to a plurality of further
DALI devices,
wherein the DALI power supply (11) is adapted to
- provide a DALI bus idle current to the DALI bus (3), during DALI bus idle times,
and
- provide a communication current, the level of which is dependent upon a communication
current input signal to the DALI bus (3), during DALI communication times.
2. DALI device (2) according to claim 1,
wherein the DALI power supply (11) comprises
- a current controller, adapted to set the communication current dependent upon the
communication current input signal,
- a power source, adapted to provide a supply current, and
- a current limiter, adapted to limit the supply current to the communication current
set by the current controller.
3. DALI device (2) according to claim 1 or 2,
wherein the DALI bus idle current is a sum of idle currents of all further DALI devices
(4-6) connected to the DALI bus (3).
4. DALI device (2) according to any of claims 1 to 3, wherein the DALI power supply (11)
is adapted to set the communication current to 1 to 3 times the DALI bus idle current,
preferably to 1,1 to 2 times the DALI bus idle current, most preferably to 1,2 to
1,5 times the DALI bus idle current.
5. DALI device (2) according to any of claims 1 to 4, wherein the DALI power supply (11)
comprises a communication current signal input (24), adapted to receive a user input
of the communication current input signal (25a).
6. DALI device (2) according to claim 5,
wherein the communication current signal input (24) is a switch or a series of switches
or a potentiometer.
7. DALI device (2) according to any of claims 1 to 4, wherein the DALI power supply (11)
comprises a DALI bus sensor (23), adapted to determine a voltage (Vmeas) indicative of the DALI bus idle current during idle times and indicative of the
communication current during communication times, and
wherein the voltage (Vmeas) is the communication current input signal (25b).
8. DALI device (2) according to any of claims 1 to 4, wherein the DALI device (2) comprises
a DALI communication interface (12), adapted to receive the communication current
input signal (25c) through the DALI bus (3).
9. DALI device (2) according to any of claims 1 to 8, wherein idle times are times in
which all of the further DALI devices (4-6) connected to the DALI bus (3) do not communicate
through the DALI bus (3) and draw an idle current, and
wherein communication times are times in which one of the further DALI devices (4-6)
connected to the DALI bus (3) short circuits the DALI bus (3) in order to send a communication
through the DALI bus (3).
10. DALI system (1) comprising a DALI device (2) according to any of the claims 1 to 10,
a DALI bus (3), and a plurality of further DALI devices (4-6),
wherein the DALI device (2) according to any of the claims 1 to 10 and the plurality
of further DALI devices (4-6) are connected to the DALI bus (3).
11. Method for operating a DALI device (2), comprising a DALI power supply (11), the DALI
device (2) being connected to a DALI bus (3), connected to a plurality of further
DALI devices (4-6),
wherein the method comprises:
- providing (100) a DALI bus idle current to the DALI bus (3), during DALI bus idle
times, by the DALI power supply (11), and
- providing (101) a communication current dependent upon a communication current input
signal to the DALI bus (3), during DALI communication times, by the DALI power supply
(11).