Power supply switching circuit for a halogen lamp

• US 7,525,293 B1
• Filed: 03/09/2005
• Issued: 04/28/2009
• Est. Priority Date: 12/06/2004
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Chen, Liang, Notohamiprodjo, Hubertus
• Primary Examiner(s): Owens; Douglas W
• Assistant Examiner(s): Alemu; Ephrem
• Application Number:
  US11/076,726
• Time in Patent Office: 1,511 Days
• Field of Search: 315/291, 315/224, 315/209.R, 315/307, 315/244, 315/276, 315/219, 363/95, 363/97, 363/98, 363/74, 323/235
• US Class Current: 323/235
• CPC Class Codes: H02M 1/425 using a single converter stage both for correction of AC input power factor and generation of a high frequency AC output voltage
• CPC Class Codes: H05B 39/045 with high-frequency bridge converters H05B39/048 takes precedence
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A power supply and methods are provided. In one implementation, the power supply includes a switching circuit and a converter. The switching circuit includes a first transistor and a second transistor, and the converter includes a capacitor and an inductor. The switching circuit alternately switches an input voltage to the converter. The power supply further includes a controller operable to adjust a switching frequency of the first transistor and the second transistor to substantially match a resonant frequency of the capacitor and the inductor.

Claims

1. A power supply comprising:

a bridge rectifier operable to rectify an alternating current (AC) voltage and generate an input voltage;

a converter to convert an input voltage into an output voltage, the converter including a capacitor and an inductor;

a switching circuit operable to alternately switch the input voltage to the converter, the switching circuit comprising a first transistor and a second transistor;

a controller operable to adjust a switching frequency of the first transistor and the second transistor to substantially match a resonant frequency of the capacitor and the inductor;

a feedback circuit operable to generate a feedback dimming control signal to the controller for reducing the output voltage of the converter; and

a current limit circuit operable to send a first error signal to the controller in an event that the power supply exceeds a pre-determined current limit, the controller operable to shut down the converter responsive to the error signal.

2. The power supply of claim 1, wherein:

the converter is an isolated series resonant converter; and

the controller is operable to adjust the switching frequency of the at least one of the first or second transistors in the switching circuit to substantially match a resonant frequency of the isolated series resonant converter.

3. The power supply of claim 1, wherein the controller comprises:

a detector operable to detect a peak voltage associated with the feedback dimming control signal;

an operational amplifier operable to compare the detected peak voltage with a reference voltage and generate a second error signal; and

a frequency control circuit operable to adjust the switching frequency of the switching circuit using the second error signal.

4. The power supply of claim 1, wherein the controller is operable to reduce the output voltage of the converter by adjusting a switching frequency of the switching circuit.

5. A power supply comprising:

a converter operable to convert an input voltage into an output voltage, the converter including a capacitor and an inductor;

a switching circuit comprising a first transistor and a second transistor, the switching circuit operable to alternately switch the input voltage to the converter when a drain-to-source voltage and a drain-to-source current of each respective transistor is substantially equal to zero;

and

a controller operable to adjust a switching frequency of the first transistor and the second transistor to substantially match a resonant frequency of the capacitor and the inductor.

6. The power supply of claim 5, wherein the converter is an isolated series resonant converter.

7. The power supply of claim 5, further comprising a bridge rectifier operable to rectify an alternating current (AC) voltage and produce the input voltage.

8. The power supply of claim 7, wherein the bridge rectifier includes four diodes connected in a bridge configuration.

9. The power supply of claim 7, further comprising a feedback circuit to generate a feedback dimming control signal to the controller for controlling the output voltage of the converter.

10. The power supply of claim 9, further comprising a current limit circuit to limit current in the converter in an event that the power supply experiences a short circuit.

11. The power supply of claim 10, wherein the feedback circuit comprises a non-inverting amplifier to amplify a voltage associated with the current limit circuit and generate the feedback dimming control signal based on the amplifier voltage.

12. The power supply of claim 9, wherein the controller comprises:

a detector operable to detect a peak voltage associated with the feedback dimming control voltage signal;

an operational amplifier to compare the detected peak voltage with a reference voltage and generate an error signal; and

a frequency control circuit operable to adjust the switching frequency of the switching circuit using the error signal.

13. The power supply of claim 12, wherein the controller is operable to reduce the output voltage of the converter by adjusting a switching frequency of the first and second transistors.

14. The power supply of claim 12, wherein the controller is operable to turn off the first transistor and the second transistor if the detected peak voltage is greater than a pre-determined level.

15. A power supply comprising:

a converter operable to convert an input voltage into an output voltage;

a switching circuit comprising a first transistor and a second transistor, the switching circuit operable to alternately switch the input voltage to the converter when a drain-to-source voltage and a drain-to-source current of each respective transistor is substantially equal to zero;

and

a controller operable to adjust a switching frequency of the switching circuit to substantially match a resonant frequency of the converter.

16. The power supply of claim 15, wherein:

the converter is an isolated series resonant converter; and

the controller is operable to adjust the switching frequency of at least one transistor in the switching circuit to substantially match a resonant frequency of the isolated series resonant converter.

17. The power supply of claim 15, wherein the controller is operable to reduce the output voltage of the converter by adjusting a frequency of the switching circuit.

18. A method of operation for a power supply, the method comprising:

rectifying an alternating current (AC) voltage and generating an input voltage;

alternately switching the input voltage to a converter according to a switching frequency;

converting the input voltage into an output voltage;

adjusting the switching frequency to substantially match a resonant frequency of the converter;

generating a feedback dimming control signal for reducing the output voltage; and

sending a first error signal to a controller in an event that a pre-determined current limit for the power supply is exceeded, and shutting down the converter responsive to the error signal.

19. The method of claim 18, wherein adjusting the switching frequency to substantially match a resonant frequency of the converter includes adjusting the switching frequency to substantially realize zero-voltage switching and zero-current switching.

20. The method of claim 18, further comprising:

detecting a peak voltage associated with the feedback dimming control signal;

comparing the detected peak voltage with a reference voltage and generating a second error signal; and

adjusting the switching frequency using the second error signal.

21. The method of claim 18, wherein reducing the output voltage includes reducing the output voltage including adjusting the switching frequency.

22. A method of operation for a power supply, the method comprising:

alternately switching an input voltage to a converter using a first transistor and a second transistor when a drain-to-source voltage and a drain-to-source current of each respective transistor is substantially equal to zero, the converter including a capacitor and an inductor;

converting the input voltage into an output voltage using the converter; and

adjusting a switching frequency of the first transistor and the second transistor to substantially match a resonant frequency of the capacitor and the inductor.

23. The method of claim 22, wherein the converter is an isolated series resonant converter.

24. The method of claim 22, further comprising rectifying an alternating current (AC) voltage to produce the input voltage.

25. The method of claim 22, further comprising generating a feedback dimming control for controlling the output voltage of the converter.

26. The method of claim 25, further comprising limiting current in the converter using a current limit circuit in an event that the power supply experiences a short circuit.

27. The method of claim 26, further comprising amplifying a voltage associated with the current limit circuit and generating the feedback dimming control signal based on the amplified voltage.

28. The method of claim 25, further comprising:

detecting a peak voltage associated with the feedback dimming control voltage signal;

comparing the detected peak voltage with a reference voltage and generating an error signal; and

adjusting the switching frequency of the first transistor and the second transistor using the error signal.

29. The method of claim 28, further comprising reducing the output voltage of the converter including adjusting a switching frequency of the first transistor and the second transistor.

30. The method of claim 28, further comprising turning off the first transistor and the second transistor if the detected peak voltage is greater than a pre-determined level.

31. A method of operation for a power supply, the method comprising:

alternately switching an input voltage to a converter according to a switching frequency when a drain-to-source voltage and a drain-to-source current of a first transistor and a second transistor is substantially equal to zero;

converting the input voltage into an output voltage using the converter; and

adjusting the switching frequency to substantially match a resonant frequency of the converter.

32. The method of claim 31, wherein:

the converter is an isolated series resonant converter; and

adjusting the switching frequency includes adjusting the switching frequency to substantially match a resonant frequency of the isolated series resonant converter.

33. The power supply of claim 31, further comprising reducing an output voltage of the converter including adjusting the switching frequency.