Electronic ballast with rail voltage switching

• US 7,091,671 B2
• Filed: 12/19/2002
• Issued: 08/15/2006
• Est. Priority Date: 12/21/2001
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Hollander, Jonathan, Orlov, Dimitry, Deurloo, Oscar J.
• Primary Examiner(s): Vo, Tuyet Thi
• Application Number:
  US10/499,159
• Publication Number:
  US 20050093479A1
• Time in Patent Office: 1,335 Days
• Field of Search: 315/247, 315/246, 315/224, 315/225, 315/209.R, 315/274, 315/276, 315/DIG.4, 315/307, 315/291
• US Class Current: 315/247
• CPC Class Codes: H05B 41/2885 Static converters especially adapted therefor; Control thereof H05B41/2882 takes precedence
• CPC Class Codes: H05B 41/2923 against abnormal power supply conditions
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

The present invention provides a high frequency electronic ballast with rail voltage switching which adjusts the DC rail voltage output (208) to account for different voltages of mains power (210), improving efficiency. The rail voltage switching comprises a mains power supply (200) providing mains power (210) and a mains voltage signal (212); a ballast microcontroller (206) responsive to the mains voltage signal (212) and generating a power factor correction (PFC) voltage signal (214); and a converter (204) operably connected to the mains power supply (200) and responsive to the PFC voltage signal (214) to generate a DC rail voltage output (208). For an embodiment using power factor control, the converter (204) comprises a coil (218), power factor correction (224), a switch (220), and a rectifier (222).

Claims

1. A rail voltage switching circuit for an electronic ballast comprising:

a mains power supply (200), the mains power supply (200) providing mains power (210) and a mains voltage signal (212);

a ballast microcontroller (206), the ballast microcontroller (214) being responsive to the mains voltage signal (212) and generating a power factor correction (PFC) voltage signal (214); and

a converter (204), the converter (204) being operably connected to the mains power supply (200) and being responsive to the PFC voltage signal (214) to generate a DC rail voltage output (208), the DC rail voltage output (208) being a first DC rail voltage output if the mains power (210) is within a first mains voltage range and a second DC rail voltage output if the mains power (210) is within a second mains voltage range.

2. The rail voltage switching circuit of claim 1 wherein the converter (204) is selected from the group consisting of buck converters, boost converters, buck-boost converters, flyback converters, single ended primary inductor converters (SEPIC), and Cuk converters.

3. The rail voltage switching circuit of claim 1 wherein the DC rail voltage output (208) is a first DC rail voltage output if the mains power (210) is below a mains power setpoint and a second DC rail voltage output if the mains power (210) is above the mains power setpoint.

4. The rail voltage switching circuit of claim 1 wherein:

the DC rail voltage output (208) changes from a first DC rail voltage output to the second DC rail voltage output as the mains power (210) increases past a first mains power setpoint;

the DC rail voltage output (208) changes from a second DC rail voltage output to a third DC rail voltage output as the mains power (210) increases past a second mains power setpoint;

the DC rail voltage output (208) changes from the third DC rail voltage output to the second DC rail voltage output as the mains power (210) decreases past the second mains power setpoint less a second offset; and

the DC rail voltage output (208) changes from the second DC rail voltage output to the first DC rail voltage output as the mains power (210) decreases past the first mains power setpoint less a first offset.

5. The rail voltage switching circuit of claim 1 wherein the ballast microcontroller (214) generates a first power factor correction (PFC) voltage signal if the mains voltage signal (212) is in a first voltage range and generates a second power factor correction (PFC) voltage signal if the mains voltage signal (212) is in a second voltage range.

6. The rail voltage switching circuit of claim 1 wherein:

the DC rail voltage output (208) changes from a first DC rail voltage output to a second DC rail voltage output as the mains power (210) increases past a mains power setpoint; and

the DC rail voltage output (208) changes from the second DC rail voltage output to the first DC rail voltage output as the mains power (210) decreases past the mains power setpoint less an offset.

7. The rail voltage switching circuit of claim 6 wherein the offset is about 20–

30 volts.

8. The rail voltage switching circuit of claim 1 wherein the DC rail voltage output (208) is a first DC rail voltage output if the mains power (210) is below a first mains power setpoint, the DC rail voltage output (208) is a second DC rail voltage output if the mains power (210) is between the first mains power setpoint and a second mains power setpoint, and a third DC rail voltage output if the mains power (210) is above the second mains power setpoint.

9. The rail voltage switching circuit of claim 8 wherein the first mains power setpoint is about 210–

215 volts, the second mains power setpoint is about 255 volts, the first DC rail voltage output is about 400 volts, the second DC rail voltage output is about 450 volts, and the third DC rail voltage output is about 465–

480 volts.

10. The rail voltage switching circuit of claim 1 wherein the converter (204) comprises:

a coil (218), the coil (218) having an input and an output, the input of the coil (218) receiving the mains power (210);

a power factor correction (224), the power factor correction (224) being responsive to the PFC voltage signal (214) and generating a PFC gate signal (230);

a switch (220), the switch (220) being operably connected to the output of the coil (218) and being responsive to the PFC gate signal (230) to generate modulated power (232); and

a rectifier (222), the rectifier (222) being responsive to the modulated power (232) to generate the DC rail voltage output (208).

11. The rail voltage switching circuit of claim 10 wherein the switch (220) provides a PFC current signal (234) and the power factor correction (224) is responsive to the PFC current signal (234).

12. The rail voltage switching circuit of claim 10 wherein the coil (218) provides a zero current input signal (236) and the power factor correction (224) is responsive to the zero current input signal (236).

13. A method of rail voltage switching for an electronic ballast comprising:

providing mains power (210);

determining voltage of the mains power (210);

determining a power factor correction (PFC) voltage signal (214) based on the voltage of the mains power (210); and

converting the mains power (210) to a DC rail voltage output (208) in response to the PFC voltage signal (214), the DC rail voltage output (208) being a first DC rail voltage output if the mains power (210) is within a first mains voltage range and a second DC rail voltage output if the mains power (210) is within a second mains voltage range.

14. The method of claim 13 further comprising:

changing the DC rail voltage output (208) from a first DC rail voltage output to the second DC rail voltage output as the voltage of the mains power (210) increases past a mains power setpoint; and

changing the DC rail voltage output (208) from the second DC rail voltage output to the first DC rail voltage output as the voltage of the mains power (210) decreases past the mains power setpoint less an offset.

15. The method of claim 13 further comprising:

changing the DC rail voltage output (208) from a first DC rail voltage output to the second DC rail voltage output as the voltage of the mains power (210) increases past a first mains power setpoint;

changing the DC rail voltage output (208) from a second DC rail voltage output to a third DC rail voltage output as the voltage of the mains power (210) increases past a second mains power setpoint;

changing the DC rail voltage output (208) from the third DC rail voltage output to the second DC rail voltage output as the voltage of the mains power (210) decreases past the second mains power setpoint less a second offset; and

changing the DC rail voltage output (208) from the second DC rail voltage output to the first DC rail voltage output as the voltage of the mains power (210) decreases past the first mains power setpoint less a first offset.

16. The method of claim 13 wherein determining a power factor correction (PFC) voltage signal (214) based on the voltage of the mains power (210) comprises:

generating a first power factor correction (PFC) voltage signal if the voltage of the mains power (210) is in a first voltage range; and

generating a second power factor correction (PFC) voltage signal if the voltage of the mains power (210) is in a second voltage range.

17. The method of claim 13 wherein converting the mains power (210) to a DC rail voltage output (208) in response to the PFC voltage signal (214) further comprises:

providing a coil (218), the coil (218) having an input and an output, the input of the coil (218) receiving the mains power (210);

generating a PFC gate signal (230) in response to the PFC voltage signal (214);

switching the output of the coil (218) in response to the PFC gate signal (230) to generate modulated power (232); and

rectifying the modulated power (232) to generate the DC rail voltage output (208).

18. The method of claim 17 further comprising:

determining a PFC current signal (234) from the switching the output of the coil (218); and

adjusting the PFC gate signal (230) in response to the PFC current signal (234).

19. The method of claim 17 further comprising:

determining current of the coil (218); and

switching the PFC gate signal (230) when the current of the coil (218) is about zero.

20. A system for producing a rail voltage switching for an electronic ballast comprising:

means for providing mains power (210);

means for determining voltage of the mains power (210);

means for determining a power factor correction (PFC) voltage signal (214) based on the voltage of the mains power (210); and

means for converting the mains power (210) to a DC rail voltage output (208) in response to the PFC voltage signal (214), the DC rail voltage output (208) being a first DC rail voltage output if the mains power (210) is within a first mains voltage range and a second DC rail voltage output if the mains power (210) is within a second mains voltage range.

21. The system of claim 20 further comprising:

means for changing the DC rail voltage output (208) from a first DC rail voltage output to a second DC rail voltage output as the voltage of the mains power (210) increases past a mains power setpoint; and

means for changing the DC rail voltage output (208) from the second DC rail voltage output to the first DC rail voltage output as the voltage of the mains power (210) decreases past the mains power setpoint less an offset.

22. The system of claim 20 further comprising:

means for changing the DC rail voltage output (208) from a first DC rail voltage output to a second DC rail voltage output as the voltage of the mains power (210) increases past a first mains power setpoint;

means for changing the DC rail voltage output (208) from a second DC rail voltage output to a third DC rail voltage output as the voltage of the mains power (210) increases past a second mains power setpoint;

means for changing the DC rail voltage output (208) from the third DC rail voltage output to the second DC rail voltage output as the voltage of the mains power (210) decreases past the second mains power setpoint less a second offset; and

means for changing the DC rail voltage output (208) from the second DC rail voltage output to the first DC rail voltage output as the voltage of the mains power (210) decreases past the first mains power setpoint less a first offset.

23. The system of claim 20 wherein the means for determining a power factor correction (PFC) voltage signal (214) based on the voltage of the mains power (210) comprises:

means for generating a first power factor correction (PFC) voltage signal if the voltage of the mains power (210) is in a first voltage range; and

means for generating a second power factor correction (PFC) voltage signal if the voltage of the mains power (210) is in a second voltage range.

24. The system of claim 20 wherein the means for converting the mains power (210) to a DC rail voltage output (208) in response to the PFC voltage signal (214) further comprises:

a coil (218), the coil (218) having an input and an output, the input of the coil (218) receiving the mains power (210);

means for generating a PFC gate signal (230) in response to the PFC voltage signal (214);

means for switching the output of the coil (218) in response to the PFC gate signal (230) to generate modulated power (232); and

means for rectifying the modulated power (232) to generate the DC rail voltage output (208).

25. The system of claim 24 further comprising:

means for determining a PFC current signal (234) from the switching the output of the coil (218); and

means for adjusting the PFC gate signal (230) in response to the PFC current signal (234).

26. The system of claim 24 further comprising:

means for determining current of the coil (218); and

means for switching the PFC gate signal (230) when the current of the coil (218) is about zero.