Low-voltage power supply circuit for illumination, illumination device, and low-voltage power supply output method for illumination

• US 20070152604A1
• Filed: 09/15/2006
• Published: 07/05/2007
• Est. Priority Date: 09/16/2005
• Status: Active Grant

• Current Assignee: Hotalux, Ltd.
• Original Assignee: NEC Lighting Limited (NEC Corporation)
• Inventors: Tatsumi, Naoki
• Granted Patent: US 7,781,982 B2
• Time in Patent Office: Days
• US Class Current: 315/247
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output

Abstract

In a low-voltage power supply circuit for illumination that rectifies an ac power supply by means of a rectifier circuit, that controls this rectified output by means of a power-factor control circuit, and that supplies a low-voltage power supply for illumination, the power-factor control circuit is composed of a step-down circuit and is further provided with a current-limiting capability.

Claims

1-12. -12. (canceled)

13. A low-voltage power supply circuit for illumination for supplying a low-voltage power supply for illumination, said low-voltage power supply circuit for illumination comprising:

a rectifier circuit for rectifying an ac power supply; and

a power-factor control circuit for controlling rectified output from said rectifier circuit, said power-factor control circuit being composed of a step-down circuit, and moreover, being provided with a current-limiting capability.

14. A low-voltage power supply circuit for illumination according to claim 13, further comprising:

a switch element that is both driven by the output of said rectifier circuit and the detected output of a power supply current and switched by the control output from said power-factor control circuit;

a step-down transformer that is controlled by the output of said switch element;

a simplified output circuit for both rectifying the output of said transformer and filtering the high-frequency component by means of a passive element; and

a current detection circuit for obtaining the detected output of said power supply current from the output current of said simplified output circuit.

15. A low-voltage power supply circuit for illumination according to claim 14, wherein:

one of the input terminals of said transformer is connected to the output of said switch element, and the other input terminal is connected to the output of said rectifier circuit.

16. A low-voltage power supply circuit for illumination according to claim 14, wherein said power-factor control circuit:

compares the detected output of a load current with a prescribed reference value and amplifies the error;

multiplies this amplified output with the output of said rectifier circuit;

compares this multiplied output with a prescribed high-frequency signal; and

drives a switch element by means of this comparison output.

17. A low-voltage power supply circuit for illumination according to claim 15, wherein said power-factor control circuit:

compares the detected output of a load current with a prescribed reference value and amplifies the error;

multiplies this amplified output with the output of said rectifier circuit;

compares this multiplied output with a prescribed high-frequency signal; and

drives a switch element by means of this comparison output.

18. A low-voltage power supply circuit for illumination according to claim 16, wherein said prescribed high-frequency signal is composed of a sawtooth-wave signal of 20-200 kHz.

19. A low-voltage power supply circuit for illumination according to claim 17, wherein said prescribed high-frequency signal is composed of a sawtooth-wave signal of 20-200 kHz.

20. An illumination device that uses the low-voltage power supply circuit for illumination according to claim 13 that is connected to a light source for illumination.

21. An illumination device according to claim 20, wherein said light source for illumination is a delighted light source such as an organic EL or an LED.

22. A low-voltage power supply output method for illumination, wherein:

a rectifier circuit rectifies an ac power supply;

a power-factor control circuit that is composed of a step-down circuit, and moreover, that is provided with a current-limiting capability controls the rectified output from said rectifier circuit; and

a low-voltage power supply for illumination is supplied as output.

23. A low-voltage power supply output method for illumination according to claim 22, wherein:

said power-factor control circuit is driven by means of the output of said rectifier circuit and the detected output of the power supply current;

a switch element is switched and driven by means of the control output from said power-factor control circuit;

a step-down transformer is controlled by means of the output of said switch element;

the output of said transformer is rectified, and further, the high-frequency component is filtered by a passive element to supply said power supply current as output; and

the detected output of said power supply current is obtained from said power supply current.

24. A low-voltage power supply output method for illumination according to claim 22, wherein said power-factor control circuit:

compares the detected output of a load current with a prescribed reference value and amplifies the error;

multiplies this amplified output with the output of said rectifier circuit;

compares this multiplied output with a prescribed high-frequency signal; and

drives said switch element by means of this comparison output.

25. An illumination method for illuminating by driving a light source for illumination by the power supply output for illumination that is obtained by the low-voltage power supply output method for illumination according to claim 22.

26. An illumination method for illuminating by driving a light source for illumination by the power supply output for illumination that is obtained by the low-voltage power supply output method for illumination according to claim 23.

27. An illumination method for illuminating by driving a light source for illumination by the power supply output for illumination that is obtained by the low-voltage power supply output method for illumination according to claim 24.

28. An illumination method according to claim 25, wherein a dc-lighted light source such as an organic EL or LED is used for said light source for illumination.

29. An illumination method according to claim 26, wherein a delighted light source such as an organic EL or LED is used for said light source for illumination.

30. An illumination method according to claim 27, wherein a dc-lighted light source such as an organic EL or LED is used for said light source for illumination.