Auxiliary turn-on mechanisms for reducing conduction loss in body-diode of low side MOSFET of coupled-inductor DC-DC converter

• US 7,786,711 B2
• Filed: 10/27/2008
• Issued: 08/31/2010
• Est. Priority Date: 05/23/2006
• Status: Expired due to Fees

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Wei, Jia, Xing, Kun
• Primary Examiner(s): Riley; Shawn
• Application Number:
  US12/259,220
• Publication Number:
  US 20090046485A1
• Time in Patent Office: 673 Days
• Field of Search: 323/224, 323/272, 323/284
• US Class Current: 323/224
• CPC Class Codes: H02M 1/0064 Magnetic structures combining different functions, e.g. storage, filtering or transformation
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel

Abstract

Conduction loss in the body-diode of a low side MOSFET of a power switching stage of one phase of a coupled-inductor, multi-phase DC-DC converter circuit, associated with current flow in the output inductor of that one phase that is induced by current flow in a mutually coupled output inductor of another phase, during normal switching of that other stage, is effectively prevented by applying auxiliary MOSFET turn-on signals, that coincide with the duration of the induced current, to that low side MOSFET, so that the induced current will flow through the turned-on low side MOSFET itself, thereby by-passing its body-diode.

Claims

1. A power supply controller, comprising:

a first circuit operable to cause a first current to flow through a first phase of a power supply in a first direction; and

a second circuit operable to cause the second phase of the power supply to operate in a reduced power dissipation mode while only a second current magnetically induced by the first current flows through the second phase in the first direction.

2. The power supply controller of claim 1 wherein the first circuit is further operable to cause the first current to flow by closing a supply side switch of the first phase.

3. The power supply controller of claim 1 wherein the first circuit is further operable to cause the first current to flow by closing a supply side transistor of the first phase.

4. The power supply controller of claim 1 wherein the first circuit is further operable to cause the first current to flow by closing a first supply side switch of the first phase and opening a first reference side switch of the first phase.

5. The power supply controller of claim 1 wherein the second circuit is further operable to cause the second phase to operate in the reduced power dissipation mode by closing a reference side switch of the second phase.

6. The power supply controller of claim 1 wherein the second circuit is further operable to cause the second phase to operate in the reduced power dissipation mode by closing a reference side transistor of the second phase.

7. The power supply controller of claim 1 wherein the second circuit is further operable to cause the second phase to exit the reduced power dissipation mode in response to the second current having a magnitude that is below a threshold.

8. The power supply controller of claim 1 wherein the second circuit is further operable to cause the second phase to exit the reduced power dissipation mode in response to a total current flowing through the second phase in a second direction opposite to the first direction.

9. The power supply controller of claim 1 wherein the second circuit is further operable to cause the second phase to exit the reduced power dissipation mode by opening a reference side switch of the second phase in response to a total current substantially equaling zero flowing through the second phase.

10. The power supply controller of claim 1 wherein the second circuit is further operable to cause the second phase to exit the reduced power dissipation mode by opening a reference side switch of the second phase in response to a total current flowing through the second phase in a direction opposite to the first direction.

11. The power supply controller of claim 1 wherein the second circuit is further operable to cause the second phase to exit the reduced power dissipation mode by opening a reference side switch of the second phase.

61. The power supply controller of claim 1 wherein the second circuit is further operable to cause the second phase to exit the reduced power dissipation mode in response to a total current flowing through the second phase in the first direction and having a magnitude that is below a threshold.

62. The power supply controller of claim 1 wherein the second circuit is further operable to cause the second phase to exit the reduced power dissipation mode by opening a reference side switch of the second phase in response to the second current substantially equaling zero.

12. A power supply controller, comprising:

a first circuit operable to open and close a first drive switch of a first power supply phase;

a second circuit operable to open and close a second circulation switch of a second power supply phase that is magnetically coupled to the first power supply phase; and

a third circuit operable to cause the second circuit to close the second circulation switch while the first drive switch is closed, while a second current flows through the second power supply phase, the second current being magnetically induced by a first current flowing through the first power supply phase, and while no other forward current flows through the second phase.

13. The power supply controller of claim 12 wherein:

the second circulation switch of the second circuit is operable to open and close a second drive switch of the second power supply phase; and

the third circuit is operable to cause the second circuit to close the second circulation switch while the second drive switch is open.

14. The power supply controller of claim 12 wherein:

the second circuit is operable to open and close a second drive switch of the second power supply phase; and

the third circuit is operable to cause the second circuit to open the second circulation switch while the second drive switch is closed.

15. The power supply controller of claim 12 wherein the third circuit is operable to cause the second circuit to open the second circulation switch in response to a magnitude of current below a threshold flowing through the second power supply phase.

16. The power supply controller of claim 12 wherein the third circuit is operable to cause the second circuit to open the second circulation switch in response to a reverse current flowing through the second power supply phase.

17. The power supply controller of claim 12 wherein:

the first circuit is operable to open and close a first circulation switch of the first power supply phase;

the second circuit is operable to open and close a second drive switch of the second power supply phase; and

the third circuit is operable to cause the first circuit to close the first circulation switch while the second drive switch is closed.

18. The power supply controller of claim 17 wherein the third circuit is operable to cause the first circuit to close the first circulation switch while the first drive switch is open.

19. The power supply controller of claim 17 wherein the third circuit is operable to cause the first circuit to open the first circulation switch while the first drive switch is closed.

20. The power supply controller of claim 17 wherein the third circuit is operable to cause the first circuit to open the first circulation switch in response to a magnitude of current below a threshold flowing through the first power supply phase.

21. The power supply controller of claim 17 wherein the third circuit is operable to cause the first circuit to open the first circulation switch in response to a reverse current flowing through the first power supply phase.

22. A power supply, comprising:

an input node;

a reference node;

an output node operable to provide a regulated output signal;

a first phase coupled to the input, reference, and output nodes;

a second phase coupled to the input, reference, and output nodes and being magnetically coupled to the first phase; and

a power supply controller, comprising;

a first circuit operable to cause a first current to flow from the input node, through the first phase, to the output node, and

a second circuit operable to cause the second phase of the power supply to operate in a reduced power dissipation mode while a second current magnetically induced by the first current is the only forward current that flows from the reference node, through the second phase, to the output node.

23. The power supply of claim 22 wherein:

the first phase comprises

a first inductor having a first node and having a second node coupled to the output node,

a first drive switch coupled between the input node and the first node of the inductor, and

a first circulation switch coupled between the reference node and the first node of the inductor; and

the second phase comprises

a second inductor having a first node and having a second node coupled to the output node,

a second drive switch coupled between the input node and the first node of the second inductor, and

a second circulation switch coupled between the reference node and the first node of the second inductor.

24. The power supply of claim 22 wherein the regulated output signal comprises a regulated output voltage.

25. The power supply of claim 22, further comprising a capacitor coupled between the output node and the reference node.

26. The power supply of claim 22 wherein the reference node comprises a ground node.

27. A system, comprising:

a load; and

a power supply, comprising

an input node,

a reference node,

an output node operable to provide a regulated output signal to the load,

a first phase coupled to the input, reference, and output nodes,

a second phase coupled to the input, reference, and output nodes and being magnetically coupled to the first phase, and

a power supply controller, comprising

a first circuit operable to cause a first current to flow from the input node, through the first phase, to the output node, and

a second circuit operable to cause the second phase to operate in a reduced power dissipation mode while a second current magnetically induced by the first current flows from the reference node, through the second phase, to the output node and while no other load-powering current flows through the second phase.

28. The system of claim 27 wherein the load comprises an integrated circuit.

29. The system of claim 27 wherein at least a portion of the load and at least a portion of the power supply are disposed on a same integrated circuit die.

30. The system of claim 27 wherein at least a portion of the load and at least a portion of the power supply are disposed on respective integrated circuit dies.

31. A power supply, comprising:

an input node;

a reference node;

an output node operable to provide a regulated output signal;

a first phase having a first drive switch coupled between the input and output nodes;

a second phase having a second circulation switch coupled between the reference and output nodes and being magnetically coupled to the first phase; and

a power supply controller, comprising

a first circuit operable to open and close the first drive switch,

a second circuit operable to open and close the second circulation switch, and

a third circuit operable to cause the second circuit to close the second circulation switch while the first drive switch is closed, while a second current flows through the second power supply phase, the second current being magnetically induced by a first current flowing through the first power supply phase, and while no other forward current flows through the second phase.

32. The power supply of claim 31 wherein:

the first phase comprises

a first inductor having a first node coupled to the first drive switch and having a second node coupled to the output node, and

a first circulation switch coupled between the reference node and the first node of the inductor; and

the second phase comprises

a second inductor having a first node coupled to the second circulation switch and having a second node coupled to the output node, and

a second drive switch coupled between the input node and the first node of the second inductor.

33. The power supply of claim 31 wherein the regulated output signal comprises a regulated output voltage.

34. The power supply of claim 31, further comprising a capacitor coupled between the output and reference nodes.

35. The power supply of claim 31 wherein the reference node comprises a ground node.

36. A system, comprising:

a load; and

a power supply, comprising,

an input node;

a reference node;

an output node operable to provide a regulated output signal to the load;

a first phase having a first drive switch coupled between the input and output nodes;

a second phase having a second circulation switch coupled between the reference and output nodes and being magnetically coupled to the first phase; and

a power supply controller, comprising

a first circuit operable to open and close the first drive switch,

a second circuit operable to open and close the second circulation switch, and

a third circuit operable to cause the second circuit to close the second circulation switch while the first drive switch is closed, while a second current flows through the second power supply phase, the second current being magnetically induced by a first current flowing through the first power supply phase, and while no other load-powering current flows through the second phase.

37. The system of claim 36 wherein the load comprises an integrated circuit.

38. The system of claim 36 wherein at least a portion of the load and at least a portion of the power supply are disposed on a same integrated circuit die.

39. The system of claim 36 wherein at least a portion of the load and at least a portion of the power supply are disposed on respective integrate circuit dies.

40. A method, comprising:

magnetically inducing a current of a first polarity in a first phase of a power supply while no other current of the first polarity is flowing in the first phase; and

closing a circulation switch of the first phase while the current is being induced.

41. The method of claim 40, further comprising closing the circulation switch only if a drive switch of the first phase is open.

42. The method of claim 40, further comprising magnetically inducing the current in the first phase by driving a current through a second phase of the power supply.

43. The method of claim 40, further comprising

opening the circulation switch in response to a total current through the first phase having a second polarity that is opposite to the first polarity.

44. The method of claim 40, further comprising opening the circulation switch in response to a total current through the first phase having a magnitude that is below a threshold.

45. The method of claim 40, further comprising opening the circulation switch in response to a total current through the first phase having a substantially zero magnitude.

46. A method, comprising:

allowing a current to flow in a direction through a first power supply phase that is magnetically coupled to a second power supply phase; and

operating the second'"'"'power supply phase in a reduced voltage drop mode while the current is flowing through the first phase and while no non-magnetically induced current is flowing through the second phase in the direction.

47. The method of claim 46, further comprising allowing the current to flow through the first phase by coupling the first phase to a supply voltage.

48. The method of claim 46, further comprising allowing the current to flow through the first phase by coupling together, with a closed switch, nodes of a filter inductor.

49. The method of claim 46, further comprising allowing the current to flow through the first phase by coupling together, with an active transistor, nodes of a filter inductor.

50. The method of claim 46, further comprising operating the second phase in the reduced voltage drop mode only while no current is being driven through the second phase.

51. The method of claim 46, further comprising operating the second phase in the reduced voltage drop mode by bypassing a diode of the second phase.

52. The method of claim 46, further comprising operating the second phase in the reduced voltage drop mode by bypassing a transistor body diode of the second phase.

53. The method of claim 46, further comprising ceasing operating the second phase in the reduced voltage drop mode in response to a cessation of the flow of current through the first phase.

54. The method of claim 46, further comprising ceasing operating the second phase in the reduced voltage drop mode by un-bypassing a diode of the second phase.

55. The method of claim 46, further comprising ceasing operating the second phase in the reduced voltage drop mode by un-bypassing a transistor body diode of the second phase.

56. The method of claim 46, further comprising ceasing operating the second phase in the reduced voltage drop mode in response to a cessation of a flow of current through the second phase.

57. The method of claim 46, further comprising ceasing operating the second phase in the reduced voltage drop mode in response to a reversal in the direction of the current flowing through the first phase.

58. The method of claim 46, further comprising ceasing operating the second phase in the reduced voltage drop mode in response to a reversal in the direction of the current flowing through the second phase.

59. The method of claim 46, further comprising operating the second phase in the reduced voltage drop mode by activating a transistor through which flows a current magnetically induced in the second phase.

60. The method of claim 46, further comprising operating the second phase in the reduced voltage drop mode by activating a switch through which flows a current magnetically induced in the second phase.