Electronic ballast with high power factor

• US 8,212,492 B2
• Filed: 06/12/2009
• Issued: 07/03/2012
• Est. Priority Date: 06/13/2008
• Status: Expired due to Fees

• Current Assignee: John C.W. Lam, Praveen K. Jain
• Original Assignee: Queen's University At Kingston
• Inventors: Lam, John, Jain, Praveen
• Primary Examiner(s): Vo, Tuyet Thi
• Application Number:
  US12/457,518
• Publication Number:
  US 20100039038A1
• Time in Patent Office: 1,117 Days
• Field of Search: 315/291, 315307-326, 315/247, 315/224, 315/225, 315/185.S
• US Class Current: 315/247
• CPC Class Codes: H05B 41/28 using static converters
• CPC Class Codes: H05B 41/2822 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations
• CPC Class Codes: H05B 41/3927 by pulse width modulation H05B41/3922 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 electronic ballast for a fluorescent lamp, including 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, including a duty ratio controller that controls a duty ratio of a switch of the ballast, and means for adjusting the duty ratio according to a nonlinear function, so that an arc is sustained across the lamp. 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 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;

wherein the electronic ballast circuit operates with only one switch.

2. The electronic ballast circuit of claim 1, wherein the PFC stage includes a single ended primary inductor converter (SEPIC).

3. The electronic ballast circuit of claim 1, wherein the inverter is a resonant inverter.

4. The electronic ballast circuit of claim 1, wherein the shared switch is the only switch.

5. The electronic ballast circuit of claim 1, further comprising an EMI filter.

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

7. The electronic ballast circuit of claim 1, wherein the inverter is a current fed inverter.

8. The electronic ballast circuit of claim 7, wherein the current fed inverter includes a C-L-L resonant circuit.

9. A fluorescent lamp comprising the electronic ballast circuit of claim 1.

10. The fluorescent lamp of claim 9, wherein the fluorescent lamp is a CFL.

11. The electronic ballast circuit of claim 1, including means for operating the shared switch at a selected duty ratio.

12. The electronic ballast circuit of claim 11, wherein the duty ratio is variable.

13. The electronic ballast circuit of claim 12, wherein the duty ratio is variable in accordance with a line voltage applied to the electronic ballast circuit.

14. A method for operating a fluorescent lamp, comprising:

converting an alternating current input voltage into a direct current output voltage;

connecting the direct current output voltage to a circuit including a combined power factor correction (PFC) stage and an inverter; and

connecting an output of the circuit to the fluorescent lamp;

wherein the PFC stage and the inverter share a switch;

wherein operating the fluorescent lamp uses only one switch.

15. The method of claim 14, including using a SEPIC for the PFC stage.

16. The method of claim 14, including using a resonant inverter for the inverter.

17. The method of claim 14, wherein the shared switch is the only switch.

18. The method of claim 14, including filtering the input voltage with an EMI filter.

19. The method of claim 14, wherein the fluorescent lamp is a CFL.

20. The method of claim 14, including using a current fed inverter for the inverter.

21. The method of claim 20, wherein the current fed inverter includes a C-L-L resonant circuit.

22. The method of claim 14, including operating the shared switch at a selected duty ratio.

23. The method of claim 22, including varying the duty ratio.

24. The method of claim 23, including varying the duty ratio in accordance with the input voltage.

25. The method of claim 22, including adjusting the duty ratio according to a nonlinear function, so that an arc is sustained across the lamp during changes in supply voltage.