Electronic Ballast with High Power Factor

• US 20120146526A1
• Filed: 08/20/2010
• Published: 06/14/2012
• Est. Priority Date: 08/21/2009
• Status: Active Grant

• Current Assignee: John C.W. Lam, Praveen K. Jain
• Original Assignee: John C.W. Lam, Praveen K. Jain
• Inventors: Lam, John, Jain, Praveen
• Granted Patent: US 8,779,674 B2
• Time in Patent Office: Days
• US Class Current: 315/200.R
• CPC Class Codes: H05B 41/2824 using control circuits for the switching element H05B41/2822 takes precedence
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

This invention provides an integrated power supply for a controller of an electronic ballast for a fluorescent lamp. The integrated power supply couples output power from the electronic ballast and uses the coupled power to provide power to the controller. In one embodiment, the electronic ballast may include a rectifier for converting an alternating current input voltage into a direct current output voltage, and a circuit including a combined power factor correction (PFC) stage and an inverter, wherein the PFC stage and the inverter share a switch. Also provided is a controller for an electronic ballast. The controller may include a voltage mode or current mode duty ratio controller that controls a duty ratio of a switch of the ballast. The controller and the ballast allow dimming of the fluorescent lamp while maintaining a high power factor.

Claims

1. An electronic ballast circuit for a fluorescent lamp, comprising:

a power circuit that outputs power to the lamp; and

an integrated power supply for a controller circuit;

wherein the power circuit operates with only one switch;

wherein the integrated power supply receives at least a portion of the output power from the power circuit and delivers power to the controller circuit.

4. The electronic ballast circuit of claim 1, wherein the power circuit comprises:

a rectifier for converting an alternating current input voltage into a direct current output voltage; and

a circuit including a combined power factor correction (PFC) stage and an inverter.

5. The electronic ballast circuit of claim 4, wherein the PFC stage includes a single ended primary inductor converter (SEPIC).

6. The electronic ballast circuit of claim 4, wherein the integrated power supply provides start-up power to the controller and provides steady state power to the controller when the lamp is at full power and when the lamp is dimmed.

7. The electronic ballast circuit of claim 6, comprising a circuit for providing start-up power including a series resistor and capacitor connected across the rectifier.

8. The electronic ballast circuit of claim 6, comprising a circuit for providing steady state power including an auxiliary winding associated with an inductor of the inverter.

9. The electronic ballast circuit of claim 4, wherein the inverter is selected from a resonant inverter and a current fed inverter.

11. The electronic ballast circuit of claim 4, wherein the inverter is a current fed inverter includes including a C-L-L resonant circuit.

17. The electronic ballast circuit of claim 1, wherein the fluorescent lamp is a compact fluorescent lamp (CFL).

18. The electronic ballast circuit of claim 4, wherein the PFC stage and the inverter share the one switch.

2-3. -3. (canceled)

10. (canceled)

12-16. -16. (canceled)

19-27. -27. (canceled)

28. A method of providing power to a fluorescent lamp, comprising:

rectifying an alternating current input voltage to produce a direct current voltage;

providing the direct current voltage to a power circuit that operates using only one switch to produce output power for the lamp; and

using a portion of the output power to provide power to a controller for the power circuit.

29. The method of claim 28, comprising:

combining a power factor correction (PFC) stage and an inverter for the power circuit; and

sharing the one switch between the PFC stage and the inverter.

30. The method of claim 28, including providing start-up power to the controller and providing steady state power to the controller when the lamp is at full power and when the lamp is dimmed.

31. The method of claim 29, including operating the shared switch at a selected duty ratio.

32. The method of claim 29, including operating the shared switch with a variable duty ratio.

33. The method of claim 28, further comprising:

using a dimmer to adjust the alternating current input voltage;

wherein adjusting the alternating current input voltage adjusts brightness of the fluorescent lamp.

38. The method of claim 33, wherein the dimmer is a leading edge dimmer.

39. The method of claim 33, wherein the dimmer is a trailing edge dimmer.

40. The method of claim 28, wherein the fluorescent lamp is a compact fluorescent lamp (CFL).

34-37. -37. (canceled)