Power control methods and apparatus for variable loads

• US 20060132061A1
• Filed: 09/12/2005
• Published: 06/22/2006
• Est. Priority Date: 09/10/2004
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Color Kinetics Incorporated (Signify N.V.)
• Inventors: Lys, Ihor A., McCormick, Kevin
• Granted Patent: US 7,542,257 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A switching power supply is modified to mitigate potentially adverse effects of near zero loads on power delivery. In one example, a processor-controlled dummy load is coupled to the power supply output in addition to an actual load. The dummy load is controlled so that at least some minimal load is presented to the power supply when the actual load is drawing low or near zero power. In another example, the feedback loop of the switching power supply is modified to mitigate the effects of a potential overvoltage condition in a bias supply from which the switch controller of the power supply draws power, which condition may occur at low or near zero load power. A lighting system may include a switching power supply thusly modified to provide power to a variable load that includes one or more LED-based lighting apparatus.

Claims

1. An apparatus, comprising:

a switching power supply configured to provide power factor correction and an output voltage to a load via control of a single switch,

wherein the apparatus is configured to mitigate a significant overvoltage condition in the output voltage as a result of a zero or near-zero power drawn by the load.

2. The apparatus of claim 1, further comprising a processor coupled to the load and configured to control an amount of load power drawn by the load from the output voltage.

3. The apparatus of claim 2, further comprising a dummy load coupled to the processor and the output voltage, wherein the processor is configured to selectively cause the dummy load to draw dummy load power from the output voltage, based on the amount of load power drawn by the load, so as to mitigate the significant overvoltage condition in the output voltage.

4. The apparatus of claim 3, wherein the processor is configured to selectively cause the dummy load to draw the dummy load power from the output voltage based on pulse width modulating the dummy load.

5. The apparatus of claim 3, wherein the processor is configured to cause the dummy load to draw the dummy load power when the load power is below a predetermined threshold power.

6. The apparatus of claim 5, wherein the predetermined threshold power is approximately 10% of a maximum load power drawn by the load.

7. The apparatus of claim 5, wherein the dummy load power approximately equals the predetermined threshold power.

8. The apparatus of claim 7, wherein the predetermined threshold power is approximately 10% of a maximum load power drawn by the load.

9. A method, comprising acts of:

A) providing power factor correction and an output voltage to a load via control of a single switch; and

B) mitigating a significant overvoltage condition in the output voltage as a result of a zero or near-zero power drawn by the load.

10. The method of claim 9, wherein the act B) comprises an act of:

B1) selectively causing a dummy load to draw dummy load power from the output voltage, based on an amount of load power drawn by the load.

11. The method of claim 10, wherein the act B1) comprises an act of:

selectively causing the dummy load to draw the dummy load power from the output voltage based on pulse width modulating the dummy load.

12. The method of claim 10, wherein the act B1) comprises an act of:

B2) causing the dummy load to draw the dummy load power when the load power is below a predetermined threshold power.

13. The method of claim 12, wherein the predetermined threshold power is approximately 10% of a maximum load power drawn by the load.

14. The method of claim 12, wherein the act B2) comprises an act of:

causing the dummy load to draw the dummy load power such that the dummy load power approximately equals the predetermined threshold power.

15. The method of claim 14, wherein the predetermined threshold power is approximately 10% of a maximum load power drawn by the load.

16. A lighting apparatus, comprising:

at least one LED-based light source; and

a switching power supply configured to provide power factor correction and a supply voltage to the at least one LED-based light source via control of a single switch,

wherein the apparatus is configured to mitigate a significant overvoltage condition in the supply voltage as a result of a zero or near-zero power drawn by the at least one LED-based light source.

17. The apparatus of claim 16, further comprising a processor coupled to the at least one LED-based light source and configured to control an amount of load power drawn by the at least one LED-based light source from the supply voltage.

18. The apparatus of claim 17, further comprising a dummy load coupled to the processor and the supply voltage, wherein the processor is configured to selectively cause the dummy load to draw dummy load power from the supply voltage, based on the amount of load power drawn by the at least one LED-based light source, so as to mitigate the significant overvoltage condition in the supply voltage.

19. The apparatus of claim 18, wherein the processor is configured to selectively cause the dummy load to draw the dummy load power from the supply voltage based on pulse width modulating the dummy load.

20. The apparatus of claim 18, wherein the processor is configured to cause the dummy load to draw the dummy load power when the load power is below a predetermined threshold power.

21. The apparatus of claim 20, wherein the predetermined threshold power is approximately 10% of a maximum load power drawn by the at least one LED-based light source.

22. The apparatus of claim 20, wherein the dummy load power approximately equals the predetermined threshold power.

23. The apparatus of claim 22, wherein the predetermined threshold power is approximately 10% of a maximum load power drawn by the at least one LED-based light source.