Dimmable constant voltage driver for being connected in parallel with further drivers and corresponding system

Abstract

A dimmable constant voltage driver (10, 20) for being connected in parallel with at least one further dimmable constant voltage driver (10, 20) to jointly or redundantly supply an LED-based load (30) is provided. Said driver (10, 20) comprises a modulation unit (11, 21) for modulating a corresponding DC output voltage of the dimmable constant voltage driver (10, 20), especially to dim the LED-based load (30), based on a modulation control signal, and a control unit (12, 22) for issuing said modulation control signal for the modulation unit (11, 21). In this context, the control unit (12, 22) is configured to provide said modulation control signal for the at least one further dimmable constant voltage driver (10, 20) and / or to receive said modulation control signal from the at least one further dimmable constant voltage driver (10, 20).

Description

[0001] The invention relates to a dimmable constant voltage driver for being connected in parallel with at least one further dimmable constant voltage driver to jointly or redundantly supply an LED-based load and a system comprising at least two such dimmable constant voltage drivers connected in parallel to jointly or redundantly supply an LED-based load.

[0002] For the purpose of increasing corresponding output power or for the purpose of providing redundancy, respectively, constant voltage drivers can be connected in parallel, when an LED-based load is to be supplied by the constant voltage drivers connected in parallel.

[0003] Disadvantageously, such constant voltage drivers connected in parallel do not allow for dimming said LED-based load.

[0004] Accordingly, there is the object to provide a dimmable constant voltage driver for being connected in parallel with at least one further dimmable constant voltage driver to jointly or redundantly supply an LED-based load and a system comprising at least two such dimmable constant voltage drivers connected in parallel to jointly or redundantly supply an LED-based load, thereby allowing for dimming the LED-based load in a particularly efficient and reliable manner.

[0005] This object is solved by the features of the first independent claim for a dimmable constant voltage driver for being connected in parallel with at least one further dimmable constant voltage driver to jointly or redundantly supply an LED-based load and the features of the second independent claim for a system comprising at least two such dimmable constant voltage drivers connected in parallel to jointly or redundantly supply an LED-based load. The dependent claims contain further developments.

[0006] According to a first aspect of the invention, a dimmable constant voltage driver for being connected in parallel with at least one further dimmable constant voltage driver to jointly or redundantly supply an LED-based load is provided. Said dimmable constant voltage driver comprises a modulation unit for modulating a corresponding DC output voltage of the dimmable constant voltage driver, especially to dim the LED-based load, based on a modulation control signal, and a control unit for issuing said modulation control signal for the modulation unit. In this context, the control unit is configured to provide said modulation control signal for the at least one further dimmable constant voltage driver and / or to receive said modulation control signal from the at least one further dimmable constant voltage driver.

[0007] Advantageously, the corresponding drivers connected in parallel, especially the modulation units thereof, can be synchronized, thereby allowing for dimming the LED-based load in a particularly efficient and reliable manner.

[0008] According to an implementation form of the first aspect of the invention, the dimmable constant voltage driver further comprises a detection unit for detecting a current peak at the corresponding output of the dimmable constant voltage driver, and for providing the correspondingly detected current peak for the control unit. In this context, the control unit is configured to adjust the modulation control signal based on the detected current peak.

[0009] Advantageously, for instance, accuracy of the above-mentioned synchronization can be improved.

[0010] According to an implementation form of the first aspect of the invention, especially in the context of adjusting the modulation control signal based on the detected current peak, the control unit is configured to determine a corresponding current peak duration of the detected current peak, and to adjust the modulation control signal such that a respective timing of corresponding modulation cycles is adjusted based on the current peak duration.

[0011] Advantageously, for example, complexity can be reduced, thereby increasing efficiency.

[0012] According to an implementation form of the first aspect of the invention, the control unit is configured to insert a time offset between issuing the modulation control signal for the modulation unit and providing the modulation control signal for the at least one further dimmable constant voltage driver.

[0013] Advantageously, for instance, a time delay of the at least one further driver can be compensated in both directions, namely too early or too late, respectively, thereby increasing both efficiency and reliability.

[0014] According to an implementation form of the first aspect of the invention, the time offset is between 0.5 and 5 microseconds, preferably between 0.6 and 4 microseconds, more preferably between 0.7 and 3 microseconds, most preferably between 0.8 and 1.5 microseconds or between 0.95 and 1.05 microseconds.

[0015] Advantageously, for example, efficiency can further be increased.

[0016] According to an implementation form of the first aspect of the invention, the modulation unit comprises or is a pulse-width modulation, PWM, unit.

[0017] Advantageously, for instance, complexity can further be reduced.

[0018] According to an implementation form of the first aspect of the invention, the modulation unit comprises or is a PWM switch.

[0019] Advantageously, for example, the PWM switch can be a PWM field-effect transistor.

[0020] According to an implementation form of the first aspect of the invention, the detection unit comprises or is a resistor, especially a shunt resistor.

[0021] Advantageously, for instance, an output current can efficiently be detected or measured, respectively.

[0022] According to an implementation form of the first aspect of the invention, especially via the control unit, the dimmable constant voltage driver is configured to operate as a primary dimmable constant voltage driver, preferably wherein each of the at least one further dimmable constant voltage driver is configured to operate as a secondary dimmable constant voltage driver.

[0023] Advantageously, for example, a self-adaptation of the system or the drivers connected in parallel, respectively, can be achieved, thereby minimizing the corresponding modulation switching delay.

[0024] According to an implementation form of the first aspect of the invention, the control unit is configured to provide the modulation control signal for the at least one further dimmable constant voltage driver.

[0025] Advantageously, in the case that the dimmable constant voltage driver operates as a primary driver, it is sufficient that said primary driver provides the modulation control signal for further drivers without receiving it from another driver.

[0026] According to an implementation form of the first aspect of the invention, especially via the control unit, the dimmable constant voltage driver is configured to operate as a secondary dimmable constant voltage driver, preferably wherein one of the at least one further dimmable constant voltage driver is configured to operate as a primary dimmable constant voltage driver.

[0027] Advantageously, for instance, a self-adaptation of the system or the drivers connected in parallel, respectively, can be achieved, thereby minimizing the corresponding modulation switching delay.

[0028] According to an implementation form of the first aspect of the invention, the control unit is configured to receive the modulation control signal from the at least one further dimmable constant voltage driver.

[0029] Advantageously, in the case that the dimmable constant voltage driver operates as a secondary driver, it is sufficient that said secondary driver receives the modulation control signal from another driver without providing it for further drivers.

[0030] According to an implementation form of the first aspect of the invention, at least one, preferably each, of the at least one further dimmable constant voltage driver is a dimmable constant voltage driver according to any of the foregoing implementation forms.

[0031] Advantageously, for example, a self-adaptation of the system or the drivers connected in parallel, respectively, can be achieved in particularly efficient manner, thereby minimizing the corresponding modulation switching delay.

[0032] According to a second aspect of the invention, a system comprising at least two dimmable constant voltage drivers connected in parallel to jointly or redundantly supply an LED-based load is provided. In this context, at least one, preferably each, of the at least two dimmable constant voltage drivers is a dimmable constant voltage driver according to the first aspect of the invention or any of its implementation forms, respectively, especially wherein one of the at least two dimmable constant voltage drivers is configured to operate as a primary dimmable constant voltage driver and each of the correspondingly remaining ones of the at least two dimmable constant voltage drivers is configured to operate as a secondary dimmable constant voltage driver.

[0033] Advantageously, the corresponding drivers connected in parallel, especially the modulation units thereof, can be synchronized, thereby allowing for dimming the LED-based load in a particularly efficient and reliable manner.

[0034] According to an implementation form of the second aspect of the invention, the system further comprises the LED-based load jointly or redundantly supplied by the at least two dimmable constant voltage drivers connected in parallel.

[0035] Exemplary embodiments of the invention are now further explained with respect to the drawings by way of example only, and not for limitation. In the drawings: Fig. 1shows respective exemplary embodiments of two dimmable constant voltage drivers and a system comprising said drivers connected in parallel; Fig. 2shows several diagrams for illumination of functioning of the system according to Fig. 1; Fig. 3shows further diagrams for further illumination of functioning of the system according to Fig. 1; Fig. 4shows a flow chart for illumination of time delay compensation or switching delay compensation, respectively, in the context of the system according to Fig. 1; and Fig. 5shows a further flow chart for illumination of time delay compensation or switching delay compensation, respectively, in the context of the system according to Fig. 1.

[0036] Fig. 1 illustrates respective exemplary embodiments of two dimmable constant voltage drivers 10, 20 and a system 40 comprising said drivers connected in parallel to jointly or redundantly supply an LED-based load 30.

[0037] As it can be seen from said Fig. 1, each of said dimmable constant voltage drivers 10, 20 exemplarily comprises a respective modulation unit 11, 21 for modulating a corresponding DC output voltage of the respective dimmable constant voltage driver 10, 20, especially to dim the LED-based load 30, based on a modulation control signal.

[0038] In this exemplary case according to Fig. 1, said modulation unit 11 or 21, respectively, is implemented as a switch, especially a pulse-width modulation, PWM, switch. For instance, said switch or PWM switch, respectively, can be a field-effect transistor, FET, or a PWM FET, respectively.

[0039] As it can further be seen from Fig. 1, each of the dimmable constant voltage drivers 10, 20 exemplarily comprises a respective control unit 12, 22 for issuing said modulation control signal for the modulation unit 11, 21 or said PWM switch, respectively.

[0040] In this exemplary case according to Fig. 1, said control unit 12 or 22, respectively, is implemented as a microcontroller.

[0041] Furthermore, especially in this exemplary case according to Fig. 1, the control unit 12 or microcontroller, respectively, of the dimmable constant voltage driver 10 is configured to provide said modulation control signal for the dimmable constant voltage driver 20, especially for the control unit 22 or microcontroller, respectively, of the dimmable constant voltage driver 20 exemplarily via a wired and / or wireless connection 44.

[0042] Moreover, especially in this exemplary case according to Fig. 1, the control unit 22 or microcontroller, respectively, of the dimmable constant voltage driver 20 is configured to receive the modulation control signal from the dimmable constant voltage driver 10, especially from the control unit 12 or microcontroller, respectively, of the dimmable constant voltage driver 10 exemplarily via the wired and / or wireless connection 44.

[0043] Accordingly, especially in this exemplary case according to Fig. 1, the dimmable constant voltage driver 10 is configured to operate as a primary dimmable constant voltage driver, whereas the dimmable constant voltage driver 20 is configured to operate as a secondary dimmable constant voltage driver.

[0044] In this context, it is noted that the dimmable constant voltage driver 10 can be configured to operate as the primary dimmable constant voltage driver via or with the aid of the control unit 12 or the microcontroller, respectively. For instance, the control unit 12 or the microcontroller, respectively, can comprise an interface, through which the dimmable constant voltage driver 10 is configured correspondingly. Further exemplarily, the corresponding configuration can be predefined, preferably during manufacturing.

[0045] By analogy, the dimmable constant voltage driver 20 can be configured to operate as the secondary dimmable constant voltage driver via or with the aid of the control unit 22 or the microcontroller, respectively. For instance, the control unit 22 or the microcontroller, respectively, can comprise an interface, through which the dimmable constant voltage driver 20 is configured correspondingly. Further exemplarily, the corresponding configuration can be predefined, preferably during manufacturing.

[0046] Advantageously, the modulation units 11 and 21 or the PWM switches, respectively, can be synchronized, thereby allowing for dimming the LED-based load 30.

[0047] For the sake of completeness, it is noted that such a synchronization may be jeopardized, especially by switching delays with respect to the corresponding modulation units or PWM switches, respectively, exemplarily by switching delays with respect to the modulation unit 21 or PWM switch, respectively, of the secondary dimmable constant voltage driver 20. For example, such switching delays can be caused by a rather high length of the connection 44 due to a spatial distribution of the dimmable constant voltage drivers 10 and 20, or by different switching behaviors of the corresponding modulation units or PWM switches, respectively, due to the usage of dimmable constant voltage drivers of different power classes.

[0048] As it can further be seen from Fig. 1, each of the dimmable constant voltage drivers 10, 20 exemplarily comprises a respective detection unit 13, 23 for detecting a current peak at the corresponding output of the dimmable constant voltage driver 10, 20, and for providing the correspondingly detected current peak for the respective control unit 12, 22 or microcontroller, respectively.

[0049] In this exemplary case according to Fig. 1, said detection unit 13 or 23, respectively, is implemented as a resistor, especially a shunt resistor.

[0050] In this context, the control unit 12 or 22, respectively, is configured to adjust the modulation control signal based on the detected current peak. In particular, in this exemplary case according to Fig. 1, the control unit 22 or microcontroller, respectively, of the secondary dimmable constant voltage driver 20 is configured to adjust the modulation control signal based on the detected current peak.

[0051] Advantageously, the above-mentioned switching delays can efficiently and reliably be compensated. Further advantageously, the secondary dimmable constant voltage driver 20 can be configured to exactly imitate the PWM behavior of the primary dimmable constant voltage driver 10. Accordingly, for instance, if the primary dimmable constant voltage driver 10 pulls PWM to logic 0 or switches off its PWS switch 11, respectively, the secondary dimmable constant voltage driver 20 also follows and switches off its PWM switch 21.

[0052] For the purpose of illuminating the functioning of such switching delay compensation or time delay compensation, respectively, Fig. 2 shows several diagrams, wherein curves relating to the primary dimmable constant voltage driver 10 are exemplarily equipped with reference sign 51 and curves relating to the secondary dimmable constant voltage driver 20 are exemplarily equipped with reference sign 52. For the sake of completeness, it is noted that said reference signs 51 and 52 are also used in the context of Fig. 3.

[0053] In particular, said Fig. 2 illustrates the behavior when the time delay is not compensated when the PWM switches are switched through. This results in a short time delay.

[0054] In this context, Fig. 2 shows an upper diagram illustrating the corresponding LED voltage with respect to the LED-based load 30 over time, a middle diagram illustrating the corresponding LED current with respect to or through the LED-based load 30 over time, and a bottom diagram illustrating a current sensed with the aid of the detection unit 23 or the shunt resistor, respectively, of the secondary dimmable constant voltage driver 20 over time.

[0055] As it can further be seen from said Fig. 2, due to the fact that the system 40 exemplarily comprises two dimmable constant voltage drivers 10, 20 with the same maximum output power, one dimmable constant voltage driver, namely the secondary dimmable constant voltage driver 20, must supply twice the output current for a short time to supply the LED-based load 30.

[0056] According to the bottom diagram of Fig. 2, said short time is exemplarily marked as a PWM FET turn on delay or a PWM switch turn on delay, respectively, of the secondary dimmable constant voltage driver 20. Said PWM FET turn on delay or a PWM switch turn on delay, respectively, is to be minimized as far as possible.

[0057] As indicated above, with the aid of the detection unit 23 or the shunt resistor, respectively, of the secondary dimmable constant voltage converter 20, a corresponding output current can be sensed or measured, respectively.

[0058] Such a current measurement allows for measuring the corresponding current peaks resulting from the time delay. Furthermore, the corresponding duration of the current increase or current peaks, respectively, can be evaluated by the control unit 22 or microcontroller, respectively, exemplarily with the aid of an analog-to-digital converter or a comparator. Moreover, the secondary dimmable constant voltage driver 20 can compensate for the time delay, exemplarily by reducing an off-time of the PWM switch 21.

[0059] Accordingly, especially in the context of adjusting the modulation control signal based on the detected current peak, it might be particularly advantageous if the corresponding control unit is configured to determine a corresponding current peak duration of the detected current peak, and to adjust the modulation control signal such that a respective timing of corresponding modulation cycles is adjusted based on the current peak duration.

[0060] With respect to the above-mentioned comparator which can be used in the context of determining the current peak duration, it is noted that Fig. 3 illustrates the above-mentioned time delay compensation for the case that such a comparator is used. In this context, curves relating to the corresponding comparator threshold are exemplarily equipped with the reference sign 53.

[0061] Said Fig. 3 shows an upper diagram illustrating the current sensed with the aid of the detection unit 23 or the shunt resistor, respectively, of the secondary dimmable constant voltage driver 20 over time as the bottom diagram of Fig. 2, a middle diagram illustrating the corresponding comparator output over time, and a bottom diagram illustrating the LED current with respect to or through the LED-based load over time.

[0062] As it can be seen from Fig. 3, synchronization of the modulation units 11 and 21 or PWM drivers or PWM switches, respectively, can exemplarily be realized by regulating the comparator output or the time delay or "delta t", respectively, as good as possible to zero.

[0063] Furthermore, it is noted that the primary dimmable constant voltage driver 10 can intentionally insert a time offset between the correspondingly output PWM signal and its own control of the PWM switch 11. Advantageously, the time delay of the secondary dimmable constant voltage driver 20 can be compensated in both directions, namely too early or too late, respectively.

[0064] Accordingly, it might be particularly advantageous if the corresponding control unit, exemplarily the control unit 12, is configured to insert a time offset between issuing the modulation control signal for the modulation unit, exemplarily the modulation unit 11 or the PWM switch of the primary dimmable constant voltage driver 10, respectively, and providing the modulation control signal for the at least one further dimmable constant voltage driver, exemplarily for the secondary dimmable constant voltage driver 20.

[0065] In this context, it might be particularly advantageous if the time offset is between 0.5 and 5 microseconds, preferably between 0.6 and 4 microseconds, more preferably between 0.7 and 3 microseconds, most preferably between 0.8 and 1.5 microseconds or between 0.95 and 1.05 microseconds.

[0066] For the sake of completeness, with respect to the dimmable constant voltage drivers 10, 20, it is noted that each of said dimmable constant voltage driver 10, 20 exemplarily comprises respective power electronics 14, 24 with respective output capacitors 15, 25, which are exemplarily configured to convert a respective input voltage, especially an AC input voltage or mains voltage, into a desired DC voltage.

[0067] Finally, the flow charts according to Fig. 4 and Fig. 5 illustrate the corresponding process.

[0068] In accordance with Fig. 4, especially according to step 61 thereof, as long as PWM is inactive, nothing is to be done or activity of PWM is to be monitored, respectively. Furthermore, as long as PWM is active, steps 62 and 63 are performed.

[0069] Said step 62 comprises measuring the corresponding output current, especially of the respective driver, and determine the corresponding time delay, preferably based on the correspondingly measured output current. Moreover, said step 63 comprises adjusting the corresponding PWM timing, preferably based on the correspondingly determined time delay.

[0070] In accordance with Fig. 5, said steps 62 and 63 are permanently performed, especially without checking for any PWM activity.

[0071] While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above described embodiments. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents.

[0072] Although the invention has been illustrated and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.

Claims

1. A dimmable constant voltage driver (10, 20) for being connected in parallel with at least one further dimmable constant voltage driver (10, 20) to jointly or redundantly supply an LED-based load (30), comprising: a modulation unit (11, 21) for modulating a corresponding DC output voltage of the dimmable constant voltage driver (10, 20), especially to dim the LED-based load (30), based on a modulation control signal, and a control unit (12, 22) for issuing said modulation control signal for the modulation unit (11, 21), wherein the control unit (12, 22) is configured to provide said modulation control signal for the at least one further dimmable constant voltage driver (10, 20) and / or to receive said modulation control signal from the at least one further dimmable constant voltage driver (10, 20).

2. The dimmable constant voltage driver (10, 20) according to claim 1, further comprising: a detection unit (13, 23) for detecting a current peak at the corresponding output of the dimmable constant voltage driver (10, 20), and for providing the correspondingly detected current peak for the control unit (12, 22), wherein the control unit (12, 22) is configured to adjust the modulation control signal based on the detected current peak.

3. The dimmable constant voltage driver (10, 20) according to claim 2, wherein, especially in the context of adjusting the modulation control signal based on the detected current peak, the control unit (12, 22) is configured to determine a corresponding current peak duration of the detected current peak, and to adjust the modulation control signal such that a respective timing of corresponding modulation cycles is adjusted based on the current peak duration.

4. The dimmable constant voltage driver (10, 20) according to any of the claims 1 to 3, wherein the control unit (12, 22) is configured to insert a time offset between issuing the modulation control signal for the modulation unit (11, 21) and providing the modulation control signal for the at least one further dimmable constant voltage driver (10, 20).

5. The dimmable constant voltage driver (10, 20) according to claim 4, wherein the time offset is between 0.5 and 5 microseconds, preferably between 0.6 and 4 microseconds, more preferably between 0.7 and 3 microseconds, most preferably between 0.8 and 1.5 microseconds or between 0.95 and 1.05 microseconds.

6. The dimmable constant voltage driver (10, 20) according to any of the claims 1 to 5, wherein the modulation unit (11, 21) comprises or is a pulse-width modulation, PWM, unit.

7. The dimmable constant voltage driver (10, 20) according to any of the claims 1 to 6, wherein the modulation unit (11, 21) comprises or is a PWM switch.

8. The dimmable constant voltage driver (10, 20) according to any of the claims 2 to 7, wherein the detection unit (13, 23) comprises or is a resistor, especially a shunt resistor.

9. The dimmable constant voltage driver (10, 20) according to any of the claims 1 to 8, wherein, especially via the control unit (12, 22), the dimmable constant voltage driver (10, 20) is configured to operate as a primary dimmable constant voltage driver, preferably wherein each of the at least one further dimmable constant voltage driver is configured to operate as a secondary dimmable constant voltage driver.

10. The dimmable constant voltage driver (10, 20) according to claim 9, wherein the control unit (12, 22) is configured to provide the modulation control signal for the at least one further dimmable constant voltage driver (10, 20).

11. The dimmable constant voltage driver (10, 20) according to any of the claims 1 to 8, wherein, especially via the control unit (12, 22), the dimmable constant voltage driver (10, 20) is configured to operate as a secondary dimmable constant voltage driver, preferably wherein one of the at least one further dimmable constant voltage driver (10, 20) is configured to operate as a primary dimmable constant voltage driver.

12. The dimmable constant voltage driver (10, 20) according to claim 11, wherein the control unit (12, 22) is configured to receive the modulation control signal from the at least one further dimmable constant voltage driver (10, 20).

13. The dimmable constant voltage driver (10, 20) according to any of the claims 1 to 12, wherein at least one, preferably each, of the at least one further dimmable constant voltage driver (10, 20) is a dimmable constant voltage driver (10, 20) according to any of the claims 1 to 12.

14. A system (40) comprising at least two dimmable constant voltage drivers (10, 20) connected in parallel to jointly or redundantly supply an LED-based load (30), wherein at least one, preferably each, of the at least two dimmable constant voltage drivers (10, 20) is a dimmable constant voltage driver (10, 20) according to any of the claims 1 to 13, especially wherein one of the at least two dimmable constant voltage drivers (10, 20) is configured to operate as a primary dimmable constant voltage driver and each of the correspondingly remaining ones of the at least two dimmable constant voltage drivers (10, 20) is configured to operate as a secondary dimmable constant voltage driver.

15. The system (40) according to claim 14, further comprising the LED-based load (30) jointly or redundantly supplied by the at least two dimmable constant voltage drivers (10, 20) connected in parallel.

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