POWER CONVERTER WITH COMPENSATION CIRCUIT FOR ADJUSTING OUTPUT CURRENT PROVIDED TO A CONSTANT LOAD

• US 20110316446A1
• Filed: 06/25/2010
• Published: 12/29/2011
• Est. Priority Date: 06/25/2010
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Kang, Douglas, Carpenter, John A., Savliwala, Taher M.
• Granted Patent: US 8,294,377 B2
• Time in Patent Office: Days
• US Class Current: 315/297
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/385 using flyback topology

Abstract

A power converter for constant loads includes an energy transfer element, a switch, a controller, and a compensation circuit. The energy transfer element is coupled to receive a rectified voltage having a non-blocked portion and a blocked portion, where an amount of the blocked portion corresponds to a phase angle. The controller is coupled to control switching of the switch to regulate an output current of the power converter in response to a plurality of signals. The plurality of signals includes a peak input voltage signal and a feedback signal, where the peak input voltage signal is representative of a peak input voltage of the power converter and the feedback signal is representative of the output voltage of the power converter. The compensation circuit is coupled to adjust at least one of the plurality of signals in response to the phase angle exceeding a phase angle threshold.

Claims

1. A power converter, comprising:

an energy transfer element coupled to receive a rectified voltage having a non-blocked portion and a blocked portion, wherein an amount of the blocked portion corresponds to a phase angle;

a switch coupled to the energy transfer element;

a controller coupled to control switching of the switch to regulate an output current of the power converter in response to a plurality of signals, wherein the plurality of signals includes a peak input voltage signal and a feedback signal, the peak input voltage signal representative of a peak input voltage of the power converter and the feedback signal representative of the output voltage of the power converter; and

a compensation circuit coupled to adjust at least one of the plurality of signals in response to the phase angle exceeding a phase angle threshold.

2. The power converter of claim 1, wherein the controller is configured to perform a power factor correction of the rectified voltage.

3. The power converter of claim 1, wherein the compensation circuit includes a phase angle voltage threshold representative of the phase angle threshold, wherein the compensation circuit is coupled to adjust the at least one of the plurality of signals in response to the feedback signal being less than the phase angle voltage threshold.

4. The power converter of claim 3, wherein the compensation circuit outputs a compensation current in response to the feedback signal when the feedback signal is less than the phase angle voltage threshold and wherein the compensation circuit is coupled to add the compensation current to the peak input voltage signal.

5. The power converter of claim 3, wherein the compensation circuit outputs a compensation current in response to the feedback signal being less than the phase angle voltage threshold and wherein the compensation current is coupled to subtract the compensation current from the feedback signal.

6. The power converter of claim 5, wherein the compensation circuit includes a transistor coupled to the resistor divider and wherein the compensation current flows through the transistor when the feedback signal is less than the phase angle voltage threshold.

7. The power converter of claim 3, wherein the compensation circuit includes a resistor divider coupled to receive the feedback signal and to set the phase angle voltage threshold.

8. The power converter of claim 3, wherein the phase angle threshold is 90 degrees.

9. The power converter of claim 1, further comprising an output sensor coupled to controller, wherein the output sensor includes an auxiliary winding of the energy transfer element to generate the feedback signal.

10. The power converter of claim 1, wherein the compensation circuit outputs a compensation current to adjust the at least one of the plurality of signals and wherein the compensation current is proportional to the feedback signal when the phase angle exceeds the phase angle threshold.

11. The power converter of claim 1, wherein the switch and the controller are included in an integrated control circuit.

12. The power converter of claim 1, wherein an output of the power converter is to coupled to a constant LED load.

13. An apparatus, comprising:

a constant load; and

a power converter coupled to provide an output current to the constant load, the power converter including;

an energy transfer element coupled to receive a rectified voltage having a non-blocked portion and a blocked portion, wherein an amount of the blocked portion corresponds to a phase angle;

a switch coupled to the energy transfer element;

a controller coupled to control switching of the switch to regulate the output current in response to a plurality of signals, wherein the plurality of signals includes a peak input voltage signal and a feedback signal, the peak input voltage signal representative of a peak input voltage of the power converter and the feedback signal representative of the output voltage of the power converter; and

a compensation circuit coupled to adjust at least one of the plurality of signals in response to the phase angle exceeding a phase angle threshold.

14. The power converter of claim 13, wherein the controller is configured to perform a power factor correction of the rectified voltage.

15. The power converter of claim 13, wherein the compensation circuit includes a phase angle voltage threshold representative of the phase angle threshold, wherein the compensation circuit is coupled to adjust the at least one of the plurality of signals in response to the feedback signal being less than the phase angle voltage threshold.

16. The apparatus of claim 15, wherein the compensation circuit outputs a compensation current in response to the feedback signal being less than the phase angle voltage threshold and wherein the compensation circuit is coupled to add the compensation current to the peak input voltage signal.

17. The apparatus of claim 15, wherein the compensation circuit outputs a compensation current in response to the feedback signal being less than the phase angle voltage threshold and wherein the compensation current is coupled to subtract the compensation current from the feedback signal.

18. The apparatus of claim 15 wherein the compensation circuit includes a resistor divider coupled to receive the feedback signal and to set the phase angle voltage threshold.

19. The apparatus of claim 18, wherein the compensation circuit includes a transistor coupled to the resistor divider and wherein the compensation current flows through the transistor when the feedback signal is less that the phase angle voltage threshold.

20. The apparatus of claim 13, wherein the power converter further includes an output sensor coupled to controller, wherein the output sensor includes an auxiliary winding of the energy transfer element to generate the feedback signal.

21. The apparatus of claim 13, wherein the compensation circuit outputs a compensation current to adjust the at least one of the plurality of signals and wherein the compensation current is proportional to the feedback signal when the phase angle exceeds the phase angle threshold.

22. The apparatus of claim 13, wherein the phase angle threshold is 90 degrees.

23. The apparatus of claim 13, wherein the switch and the controller are included in an integrated control circuit.

24. The apparatus of claim 13, wherein the constant load is an LED array.

25. A method, comprising:

generating a feedback signal representative of an output voltage of a power converter;

receiving a peak input voltage signal representative of a peak input voltage of the power converter;

controlling a switching of a switch included in the power converter to regulate an output current in response to a plurality of signals, wherein the plurality of signals includes the input voltage signal and the feedback signal; and

adjusting at least one of the plurality of signals in response to feedback signal being less than a phase angle voltage threshold to adjust the output current.

26. The method of claim 25, further comprising generating a compensation current in response to the feedback signal being less than the phase angle voltage threshold, wherein adjusting the at least one of the plurality of signals includes subtracting the compensation current from the feedback signal.

27. The method of claim 25, further comprising generating a compensation current in response to the feedback signal being less than the phase angle voltage threshold, wherein adjusting the at least one of the plurality of signals includes adding the compensation current to the input voltage signal.

28. The method of claim 25, wherein the phase angle voltage threshold is representative of a dimmer control input corresponding to a phase angle of 90 degrees.

29. The method of claim 25, further comprising providing the output current to the constant load, wherein the constant load is an LED array.