Method for controlling a switching regulator and related switching regulator

• US 8,179,699 B2
• Filed: 12/31/2008
• Issued: 05/15/2012
• Est. Priority Date: 12/31/2008
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Tumminaro, Salvatore, Giombanco, Salvatore, Pasqua, Alfio, Adragna, Claudio
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): PHAM, EMILY P
• Application Number:
  US12/347,889
• Publication Number:
  US 20100164443A1
• Time in Patent Office: 1,231 Days
• Field of Search: 363/20, 363/21.01, 363/21.04, 363/21.07, 363/21.09, 363/21.12, 363/21.15, 363/21.17
• US Class Current: 363/20
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence

Abstract

An embodiment of a power-supply controller comprises a switching-control circuit, an error amplifier, and a signal generator. The switching-control circuit is operable to control a switch coupled to a primary winding of a transformer, and the error amplifier has a first input node operable to receive a feedback signal, a second input node operable to receive a comparison signal, and an output node operable to provide a control signal to the switching-control circuit. The signal generator is operable to generate either the feedback signal or the comparison signal in response to a compensation signal that is isolated from a secondary winding of the transformer and that is proportional to a load current through a conductor disposed between the secondary winding and a load.

Claims

1. A power-supply controller, comprising:

a switching-control circuit operable to control a switch coupled to a primary winding of a transformer;

an error amplifier having a first input node operable to receive a first feedback signal from an auxiliary winding of the transformer, a second input node operable to receive a comparison signal, and an output node operable to provide a control signal to the switching-control circuit; and

a comparison-signal generator operable to generate the comparison signal in response to a first compensation signal that is isolated from a secondary winding of the transformer and that is proportional to a load current through a conductor disposed between the secondary winding and a load, the first compensation signal derived from a signal independent of the secondary winding.

2. The power-supply controller of claim 1 wherein the switching control circuit comprises a comparator having a first input node operable to receive the control signal from the error amplifier, a second input node operable to receive a second feedback signal that is proportional to a current through the primary winding, and an output node operable to be coupled to a control node of the switch.

3. The power-supply controller of claim 1 wherein the feedback, comparison, and control signals respectively comprise feedback, comparison, and control voltages.

4. The power-supply controller of claim 1 wherein the first compensation signal is operable to have a first level while a non-zero current flows through the secondary winding and to have a second level while a substantially zero current flows through the secondary winding.

10. The power-supply controller of claim 1 wherein the comparison-signal generator is operable to generate the comparison signal in response to a reference signal.

11. The power-supply controller of claim 1 wherein the comparison-signal generator is operable to generate the comparison signal in response to a reference voltage.

12. The power-supply controller of claim 1 wherein the comparison-signal generator is operable to generate the comparison signal in response to the control signal.

13. The power-supply controller of claim 1 wherein the comparison-signal generator is operable to generate the comparison signal in response to the control signal and a reference signal.

15. The power-supply controller of claim 1 wherein the load current substantially equals a current flowing through the secondary winding.

5. A power-supply controller, comprising:

a switching-control circuit operable to control a switch coupled to a primary winding of a transformer;

an error amplifier having a first input node operable to receive a first feedback signal from an auxiliary winding of the transformer, a second input node operable to receive a comparison signal, and an output node operable to provide a control signal to the switching-control circuit; and

a comparison-signal generator operable to generate the comparison signal in response to a first compensation signal that is isolated from a secondary winding of the transformer and that is proportional to a load current through a conductor disposed between the secondary winding and a load;

wherein the first compensation signal is proportional to a ratio of a time during which current flows through the secondary winding to a period during which the switching-control circuit activates and deactivates the switch.

6. A power-supply controller, comprising:

a switching-control circuit operable to control a switch coupled to a primary winding of a transformer;

an error amplifier having a first input node operable to receive a first feedback signal from an auxiliary winding of the transformer, a second input node operable to receive a comparison signal, and an output node operable to provide a control signal to the switching-control circuit;

a comparison-signal generator operable to generate the comparison signal in response to a first compensation signal that is isolated from a secondary winding of the transformer and that is proportional to a load current through a conductor disposed between the secondary winding and a load; and

a compensation circuit operable to generate the first compensation signal from a second compensation signal that is isolated from the secondary winding and that is proportional to the load current.

7. The power-supply controller of claim 6 wherein the compensation circuit is operable to generate the first compensation signal from the second compensation signal and from a reference signal.

8. The power-supply controller of claim 6 wherein the compensation circuit is operable to generate the first compensation signal from the second compensation signal and from a reference current.

9. The power-supply controller of claim 6 wherein the first and second compensation signals respectively comprise first and second compensation voltages.

14. A power-supply controller, comprising:

a switching-control circuit operable to control a switch coupled to a primary winding of a transformer;

an error amplifier having a first input node operable to receive a first feedback signal from an auxiliary winding of the transformer, a second input node operable to receive a comparison signal, and an output node operable to provide a control signal to the switching-control circuit; and

a comparison-signal generator operable to generate the comparison signal in response to a first compensation signal that is isolated from a secondary winding of the transformer and that is proportional to a load current through a conductor disposed between the secondary winding and a load;

wherein the comparison-signal generator is operable to generate the comparison signal equal to a difference between a reference voltage and a ratio of the control signal to the first compensation signal.

16. A power-supply controller, comprising:

a switching-control circuit operable to control a switch coupled to a primary winding of a transformer;

an error amplifier having a first input node operable to receive a first feedback signal, a second input node operable to receive a reference signal, and an output node operable to provide a control signal to the switching-control circuit; and

a feedback-signal generator operable to generate the first feedback signal in response to a first compensation signal that is isolated from a secondary winding of the transformer and that is proportional to a load current through a conductor disposed between the secondary winding and a load, the first compensation signal derived only from signals independent of the secondary winding;

wherein the switching circuit comprises a comparator having a first input node operable to receive the control signal from the error amplifier, a second input node operable to receive a second feedback signal that is proportional to a current through the primary winding, and an output node operable to be coupled to a control node of the switch.

17. The power-supply controller of claim 16 wherein the feedback, reference, and control signals respectively comprise feedback, reference, and control voltages.

18. The power-supply controller of claim 16 wherein the first compensation signal is operable to have a first level while a non-zero current flows through the secondary winding and to have a second level while a substantially zero current flows through the secondary winding.

19. The power-supply controller of claim 16 wherein the first compensation signal comprises a substantially DC compensation voltage.

25. The power-supply controller of claim 16 wherein the feedback-signal generator is operable to generate the first feedback signal in response to a signal from an auxiliary winding of the transformer.

26. The power-supply controller of claim 16 wherein the feedback-signal generator is operable to generate the first feedback signal in response to a voltage across an auxiliary winding of the transformer.

27. The power-supply controller of claim 16 wherein the feedback-signal generator is operable to generate the first feedback signal in response to the control signal.

28. The power-supply controller of claim 16 wherein the first feedback-signal generator is operable to generate the feedback signal in response to the control signal and a signal from an auxiliary winding of the transformer.

30. The power-supply controller of claim 16 wherein the load current substantially equals a current flowing through the secondary winding.

20. A power-supply controller, comprising:

a switching-control circuit operable to control a switch coupled to a primary winding of a transformer;

an error amplifier having a first input node operable to receive a first feedback signal, a second input node operable to receive a reference signal, and an output node operable to provide a control signal to the switching-control circuit; and

a feedback-signal generator operable to generate the first feedback signal in response to a first compensation signal that is isolated from a secondary winding of the transformer and that is proportional to a load current through a conductor disposed between the secondary winding and a load;

wherein the first compensation signal is proportional to a ratio of a time during which current flows through the secondary winding to a period during which the switching-control circuit activates and deactivates the switch.

21. A power-supply controller, comprising:

a switching-control circuit operable to control a switch coupled to a primary winding of a transformer;

an error amplifier having a first input node operable to receive a first feedback signal, a second input node operable to receive a reference signal, and an output node operable to provide a control signal to the switching-control circuit;

a feedback-signal generator operable to generate the first feedback signal in response to a first compensation signal that is isolated from a secondary winding of the transformer and that is proportional to a load current through a conductor disposed between the secondary winding and a load; and

a compensation circuit operable to generate the first compensation signal from a second compensation that is isolated from the secondary winding and that is proportional to the load current.

22. The power-supply controller of claim 21 wherein the compensation circuit is operable to generate the first compensation signal from the second compensation signal and from a reference signal.

23. The power-supply controller of claim 21 wherein the compensation circuit is operable to generate the first compensation signal from the second compensation signal and from a reference current.

24. The power-supply controller of claim 21 wherein the first and second compensation signals respectively comprise first and second compensation voltages.

29. A power-supply controller, comprising:

a switching-control circuit operable to control a switch coupled to a primary winding of a transformer;

an error amplifier having a first input node operable to receive a first feedback signal, a second input node operable to receive a reference signal, and an output node operable to provide a control signal to the switching-control circuit; and

a feedback-signal generator operable to generate the first feedback signal in response to a first compensation signal that is isolated from a secondary winding of the transformer and that is proportional to a load current through a conductor disposed between the secondary winding and a load;

wherein the feedback-signal generator is operable to generate the feedback signal inversely proportional to a ratio of the control signal to the first compensation signal.

31. A power supply, comprising:

a transformer having primary, secondary, and auxiliary windings;

a switch serially coupled to the primary winding; and

a power-supply controller, comprising

a switching-control circuit operable to control the switch,

an error amplifier having a first input node operable to receive a first feedback signal from the auxiliary winding, a second input node operable to receive a comparison signal, and an output node operable to provide a control signal to the switching-control circuit, and

a comparison-signal generator operable to generate the comparison signal in response to a first compensation signal that is isolated from the secondary winding and derived from signals only associated with the primary winding and that is proportional to a load current through a conductor disposed between the secondary winding and a load.

32. The power supply of claim 31 wherein the switch comprises a transistor.

33. A power supply, comprising:

a transformer having primary, secondary, and auxiliary windings;

a switch serially coupled to the primary winding; and

a power-supply controller, comprising

a switching-control circuit operable to control the switch,

an error amplifier having a first input node operable to receive a first feedback signal, a second input node operable to receive a reference signal, and an output node operable to provide a control signal to the switching-control circuit, and

a feedback-signal generator operable to generate the first feedback signal in response to a first compensation signal that is isolated from a secondary winding and derived from signals only associated with the primary winding and that is proportional to a load current through a conductor disposed between the secondary winding and a load

wherein the switching circuit comprises a comparator having a first input node operable to receive the control signal from the error amplifier, a second input node operable to receive a second feedback signal that is proportional to a current through the primary winding, and an output node operable to be coupled to a control node of the switch.

34. The power supply of claim 33 wherein the switch comprises a transistor.

35. A system, comprising:

a load;

a conductor having a first node coupled to the load and having a second node; and

a power supply comprising

a transformer having a primary winding, a secondary winding coupled to the second node of the conductor, and an auxiliary winding,

a switch serially coupled to the primary winding, and

a power-supply controller, comprising

a switching-control circuit operable to control the switch,

an error amplifier having a first input node operable to receive a first feedback signal from the auxiliary winding, a second input node operable to receive a comparison signal, and an output node operable to provide a control signal to the switching-control circuit, and

a comparison-signal generator operable to generate the comparison signal in response to a first compensation signal that is isolated from the secondary winding of the transformer and derived from a signal through the primary winding that is proportional to a current through the conductor.

36. The system of claim 35 wherein the load and the power-supply controller are disposed on a same integrated-circuit die.

37. The system of claim 35 wherein the load, the power-supply controller, and the switch are disposed on a same integrated-circuit die.

38. The system of claim 35 wherein the load, the conductor, and the power supply are disposed on a same integrated-circuit die.

39. The system of claim 35 wherein the load comprises a controller.

40. The system of claim 35 wherein the load and the power-supply controller are disposed on separate integrated-circuit dies.

41. The system of claim 35 wherein the load and the conductor are disposed on a same integrated-circuit die.

42. The system of claim 35 wherein:

the load is disposed on a first integrated-circuit die;

the power-supply controller is disposed on a second integrated-circuit die; and

the conductor is disposed between the first and second dies.

43. A system, comprising:

a load;

a conductor having a first node coupled to the load and having a second node; and

a power supply, comprising

a transformer having primary, secondary, and auxiliary windings,

a switch serially coupled to the primary winding, and

a power-supply controller, comprising

a switching-control circuit operable to control the switch,

an error amplifier having a first input node operable to receive a first feedback signal from the auxiliary winding, a second input node operable to receive a reference signal, and an output node operable to provide a control signal to the switching-control circuit, and

a feedback-signal generator operable to generate the first feedback signal in response to a first compensation signal that is derived from the primary winding and isolated from a secondary winding and that is proportional to a load current through a conductor disposed between the secondary winding and a load.

44. The system of claim 43 wherein the load and the power-supply controller are disposed on a same integrated-circuit die.

45. The system of claim 43 wherein the load, the power-supply controller, and the switch are disposed on a same integrated-circuit die.

46. The system of claim 43 wherein the load, the conductor, and the power supply are disposed on a same integrated-circuit die.

47. The system of claim 43 wherein the load comprises a controller.

48. The system of claim 43 wherein the load and the power-supply controller are disposed on separate integrated-circuit dies.

49. The system of claim 43 wherein the load and the conductor are disposed on a same integrated-circuit die.

50. The system of claim 43 wherein:

the load is disposed on a first integrated-circuit die;

the power-supply controller is disposed on a second integrated-circuit die; and

the conductor is disposed between the first and second dies.

51. A method, comprising:

generating a regulated output voltage with a secondary winding of a transformer;

generating a comparison signal in response to a first compensation signal that is isolated from, and that is proportional to a current through, the secondary winding, the first comparison signal derived from current through the primary winding;

generating a control signal in response to the comparison signal and in response to a first feedback signal from an auxiliary winding of the transformer; and

switching a current through a primary winding of the transformer in response to the control signal;

wherein the comparison signal is equal to a difference between a reference voltage and a ratio of the control signal to the first compensation signal.

52. The method of claim 51, further comprising:

generating the first compensation signal having a first level while a non-zero current flows through the secondary winding; and

generating the first compensation signal having a second level otherwise.

56. The method of claim 51 wherein generating the comparison signal comprises generating the comparison signal in response to a reference signal.

57. The method of claim 51 wherein generating the comparison signal comprises generating the comparison signal in response to the control signal.

58. The method of claim 51 wherein generating the comparison signal comprises generating the comparison signal in response to the control signal and a reference signal.

59. The method of claim 51 wherein the first compensation signal is proportional to an average current through the secondary winding.

53. A method, comprising:

generating a regulated output voltage with a secondary winding of a transformer;

generating a comparison signal in response to a first compensation signal that is isolated from, and that is proportional to a current through, the secondary winding;

generating a control signal in response to the comparison signal and in response to a first feedback signal from an auxiliary winding of the transformer;

switching a current through a primary winding of the transformer in response to the control signal; and

generating the first compensation signal proportional to a ratio of a time during which current flows through the secondary winding to a period with which current is switched through the primary winding.

54. A method, comprising:

generating a regulated output voltage with a secondary winding of a transformer;

generating a comparison signal in response to a first compensation signal that is isolated from, and that is proportional to a current through, the secondary winding;

generating a control signal in response to the comparison signal and in response to a first feedback signal from an auxiliary winding of the transformer;

switching a current through a primary winding of the transformer in response to the control signal;

generating the first compensation signal from a second compensation signal that is isolated from the secondary winding and that is proportional to the current through the secondary winding.

55. The method of claim 54 wherein generating the first compensation signal comprises generating the first compensation signal from the second compensation signal and from a reference signal.

60. A method, comprising:

generating a regulated output voltage with a secondary winding of a transformer;

generating a feedback signal in response to a first compensation signal that is isolated from, and that is proportional to a current through the secondary winding, the first compensation signal derived from current through the primary winding and independent of current through the secondary winding;

generating a control signal in response to a reference signal and in response to the feedback signal; and

switching a current through a primary winding of the transformer in response to the control signal.

64. The method of claim 60 wherein generating the feedback signal comprises generating the feedback signal in response to a signal from an auxiliary winding of the transformer.

65. The method of claim 60 wherein generating the feedback signal comprises generating the feedback signal in response to the control signal.

66. The method of claim 60 wherein generating the feedback signal comprises generating the first feedback signal in response to the control signal and a signal from an auxiliary winding of the transformer.

61. A method, comprising:

generating a regulated output voltage with a secondary winding of a transformer;

generating a feedback signal in response to a first compensation signal that is isolated from, and that is proportional to a current through, the secondary winding;

generating a control signal in response to a reference signal and in response to the feedback signal;

switching a current through a primary winding of the transformer in response to the control signal; and

generating the first compensation signal proportional to a ratio of a time during which current flows through the secondary winding to a period with which current is switched through the primary winding.

62. A method, comprising:

generating a regulated output voltage with a secondary winding of a transformer;

generating a feedback signal in response to a first compensation signal that is isolated from, and that is proportional to a current through, the secondary winding;

generating a control signal in response to a reference signal and in response to the feedback signal;

switching a current through a primary winding of the transformer in response to the control signal; and

generating the first compensation signal from a second compensation signal that is isolated from the secondary winding and that is proportional to the current through the secondary winding.

63. The method of claim 62 wherein generating the first compensation signal comprises generating the first compensation signal from the second compensation signal and from a reference signal.

67. A method, comprising:

generating a regulated output voltage with a secondary winding of a transformer;

generating a feedback signal in response to a first compensation signal that is isolated from, and that is proportional to a current through, the secondary winding;

generating a control signal in response to a reference signal and in response to the feedback signal; and

switching a current through a primary winding of the transformer in response to the control signal;

wherein generating the feedback signal comprises generating the feedback signal inversely proportional to a ratio of the control signal to the first compensation signal.