POWER SUPPLIES FOR LED LIGHT FIXTURES

• US 20110095704A1
• Filed: 10/26/2010
• Published: 04/28/2011
• Est. Priority Date: 10/26/2009
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Light-Based Technologies Incorporated
• Inventors: Moussakov, Milen, Foxall, Thomas George
• Granted Patent: US 8,987,995 B2
• Time in Patent Office: Days
• US Class Current: 315/294
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A lighting circuit comprises an AC input connectable to receive an AC input voltage, a switched LED array comprising a plurality of LEDs reconfigurable into a plurality of configurations and having an input for receiving a LED driving voltage, a switched capacitor array having an input for receiving a charging voltage and an output selectively connectable to the input of the switched LED array and comprising a plurality of capacitors and switches connected to selectively couple the capacitors across the input or output, a first switched rectifier connected between the AC input and the switched LED array, a second switched rectifier connected between the AC input and the switched capacitor array, and, a control system configured to monitor the AC input voltage and control the switched LED array, the switched capacitor array and the first and second switched rectifiers based on the AC input voltage and a desired light output.

Claims

1. A lighting circuit, comprising:

an AC input connectable to receive an AC input voltage

a switched LED array comprising a plurality of LEDs reconfigurable into a plurality of configurations, the switched LED array having an input for receiving a LED driving voltage;

a switched capacitor array having an input for receiving a charging voltage and an output selectively connectable to the input of the switched LED array, the switched capacitor array comprising a plurality of capacitors and a plurality of switches connected to selectively couple the capacitors across the input of the switched capacitor array or the output of the switched capacitor array;

a first switched rectifier connected between the AC input and the input of the switched LED array;

a second switched rectifier connected between the AC input and the input of the switched capacitor array; and

,

a control system configured to monitor the AC input voltage and control the switched LED array, the switched capacitor array, the first switched rectifier and the second switched rectifier based on the AC input voltage and a desired light output.

2. A circuit according to claim 1 wherein the control system is configured to connect the input of the switched LED array to the AC input through the first switched rectifier when the AC input voltage is at least a threshold voltage such that the switched LED array receives the AC input voltage as the LED driving voltage.

3. A circuit according to claim 2 wherein the control system is configured to connect the input of the switched LED array to the output of the switched capacitor array when the AC input voltage is less than the threshold voltage and sequentially connect capacitors of the switched capacitor array for discharging across the output of the switched capacitor array such that the switched LED array receives a capacitor discharge voltage as the LED driving voltage.

4. A circuit according to claim 2 wherein, when the AC input voltage is at least the threshold voltage, the control system is configured to reconfigure the switched LED array as the AC input voltage changes such that current through the LEDs is maintained within a desired range.

5. A circuit according to claim 4 wherein the control system is configured to open switches of the first switched rectifier to momentarily disconnect the switched LED array from the AC input voltage while the switched LED array is being reconfigured.

6. A circuit according to claim 4 wherein the control system is configured to control an overall brightness of light output by the switched LED array by adjusting voltages at which configuration transitions occur.

7. A circuit according to claim 6 wherein the control system is configured to adjust the configuration transitions to occur at higher voltages to increase the overall brightness.

8. A circuit according to claim 6 wherein the control system is configured to adjust the configuration transitions to occur at lower voltages to decrease the overall brightness.

9. A circuit according to claim 3 wherein the control system is configured operate the second switched rectifier and the switched capacitor array to charge each of the plurality of capacitors to at least the threshold voltage.

10. A circuit according to claim 1 wherein the plurality of capacitors of the switched capacitor array are arranged in a plurality of branches having different numbers of capacitors in each branch, and wherein the control system is configured to operate the second switched rectifier and the switches of the switched capacitor array to connect the capacitors of a selected branch in series to receive the AC input voltage to charge the capacitors of the selected branch, wherein the selected branch has a number of capacitors selected based on an input voltage level and the selected branch varies as the input voltage level changes.

11. A circuit according to claim 10 wherein the branches of the switched capacitor array are arranged in a charging order wherein the number of capacitors in the branches varies across the charging order to correspond to a sinusoidal input voltage.

12. A circuit according to claim 10 wherein the control system is configured to control a charging time for each selected branch such that all of the capacitors are charged to the same voltage level.

13. A circuit according to claim 12 wherein each selected branch is charged for a charging period, and wherein the control system is configured to vary the voltage to which the capacitors are charged by adjusting the charging period relative to the AC input voltage.

14. A circuit according to claim 13 wherein the control system is configured to increase the voltage to which the capacitors are charged by shifting the charging periods toward a peak voltage, and wherein the control system is configured to decrease the voltage to which the capacitors are charged by shifting the charging periods away from a peak voltage.

15. A method comprising:

providing a switched LED array comprising a plurality of LEDs reconfigurable into a plurality of configurations, the switched LED array having an input for receiving a LED driving voltage;

providing a switched capacitor array having an input for receiving a charging voltage and an output selectively connectable to the input of the switched LED array, the switched capacitor array comprising a plurality of capacitors and a plurality of switches connected to selectively couple the capacitors across the input of the switched capacitor array or the output of the switched capacitor array;

providing a first switched rectifier connected between an AC input and the input of the switched LED array;

providing a second switched rectifier connected between the AC input and the input of the switched capacitor array;

monitoring an AC input voltage at the AC input; and

,

controlling the switched LED array, the switched capacitor array, the first switched rectifier and the second switched rectifier based on the AC input voltage and a desired light output.

16. A method according to claim 15 comprising connecting the input of the switched LED array to the AC input through the first switched rectifier when the AC input voltage is at least a threshold voltage such that the switched LED array receives the AC input voltage as the LED driving voltage.

17. A method according to claim 16 comprising connecting the input of the switched LED array to the output of the switched capacitor array when the AC input voltage is less than the threshold voltage and sequentially connecting capacitors of the switched capacitor array for discharging across the output of the switched capacitor array such that the switched LED array receives a capacitor discharge voltage as the LED driving voltage.

18. A method according to claim 16 comprising, when the AC input voltage is at least the threshold voltage, reconfiguring the switched LED array as the AC input voltage changes such that current through the LEDs is maintained within a desired range.

19. A method according to claim 18 comprising opening switches of the first switched rectifier to momentarily disconnect the switched LED array from the AC input voltage while the switched LED array is being reconfigured.

20. A method according to claim 18 comprising controlling an overall brightness of light output by the switched LED array by adjusting voltages at which configuration transitions occur.

21. A method according to claim 20 comprising adjusting the configuration transitions to occur at higher voltages to increase the overall brightness.

22. A method according to claim 20 comprising adjusting the configuration transitions to occur at lower voltages to decrease the overall brightness.

23. A method according to claim 17 comprising operating the second switched rectifier and the switched capacitor array to charge each of the plurality of capacitors to at least the threshold voltage.

24. A method according to claim 15 wherein the plurality of capacitors of the switched capacitor array are arranged in a plurality of branches having different numbers of capacitors in each branch, comprising operating the second switched rectifier and the switches of the switched capacitor array to connect the capacitors of a selected branch in series to receive the AC input voltage to charge the capacitors of the selected branch, wherein the selected branch has a number of capacitors selected based on an input voltage level and the selected branch varies as the input voltage level changes.

25. A lighting circuit comprising:

a switched rectifier having an input connectable to receive an AC input voltage;

a switched LED array comprising a plurality of LEDs reconfigurable into a plurality of configurations, the switched LED array having an input connected to an output of the switched rectifier; and

,

a control system configured to monitor the AC input voltage and control the switched LED array and the switched rectifier based on the AC input voltage and a desired light output.