Multiple phase switching regulators with stage shedding

• US 20020135338A1
• Filed: 02/08/2001
• Published: 09/26/2002
• Est. Priority Date: 02/08/2001
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Hobrecht, Stephen W., Flatness, Randy G.
• Granted Patent: US 6,674,274 B2
• Time in Patent Office: Days
• US Class Current: 323/272
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• 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

Multiple phase switching regulators with stage shedding are provided. Multiple phase switching regulators of the present invention have a plurality of single phase switching regulators coupled in parallel to an output capacitor. The plurality of single phase switching regulators supply current to a load at a regulated voltage. A comparator monitors the load current and causes one or more of the single phase switching regulators to be OFF at a low load current threshold. At least one of the single phase switching regulators that remains ON increases its output current so that the multiple phase switching regulator output current continues to match the load current. The present invention may include a second comparator that causes additional single phase switching regulators to be OFF at a second low load current threshold that is lower than the first low load current threshold.

Claims

1. A multiple phase switching regulator, comprising:

a plurality of single phase switching regulators coupled to an output; and

a first comparator coupled to a feedback loop circuit that prevents a first one of the single phase switching regulators from providing output current to a load coupled to the output after the load current drops below a threshold of the first comparator.

2. The multiple phase switching regulator of claim 1 wherein the feedback loop further comprises:

a first amplifier coupled to a resistor divider and at least one of the single phase switching regulators.

3. The multiple phase switching regulator of claim 1 wherein the plurality of single phase switching regulators are synchronous switching regulators.

4. The multiple phase switching regulator of claim 1 wherein the plurality of single phase switching regulators comprises three single phase switching regulators.

5. The multiple phase switching regulator of claim 4 wherein the first comparator prevents two of the single phase switching regulators from outputting current to the load when the load current drops below the threshold of the first comparator.

6. The multiple phase switching regulator of claim 1 wherein the plurality of single phase switching regulators comprises four single phase switching regulators.

7. The multiple phase switching regulator of claim 6 wherein the first comparator prevents three of the single phase switching regulators from outputting current to the load when the load current drops below the threshold of the first comparator.

8. The multiple phase switching regulator of claim 6 wherein the first comparator prevents two of the single phase switching regulators from outputting current to the load when the load current drops below the threshold of the first comparator.

9. The multiple phase switching regulator of claim 1 wherein at least a second one of the single phase switching regulators comprises:

a first gain control circuit coupled to the first comparator that causes the output current of the second single phase switching regulator to increase after the load current drops below the threshold of the first comparator.

10. The multiple phase switching regulator of claim 9 wherein the first gain control circuit comprises:

an amplifier coupled to the feedback loop circuit that increases a current threshold of the second single phase switching regulator.

11. The multiple phase switching regulator of claim 9 wherein the first gain control circuit further comprises:

a resistor; and

a transistor coupled to the resistor and the first comparator, wherein the transistor shorts the resistor when the load current drops below the threshold of the first comparator.

12. The multiple phase switching regulator of claim 9 further comprising:

a second comparator coupled to a feedback loop circuit that prevents the second single phase switching regulator from outputting current to the load when the load current drops below a threshold of the second comparator that is less than the threshold of the first comparator.

13. The multiple phase switching regulator of claim 12 wherein at least a third one of the single phase switching regulators comprises:

a second gain control circuit coupled to the second comparator that causes the output current of the third single phase switching regulator to increase after the load current falls below the threshold of the second comparator.

14. The multiple phase switching regulator of claim 13 wherein the second gain control circuit comprises further comprises:

a resistor; and

a transistor coupled to the resistor and the second comparator, wherein the transistor shorts the resistor when the load current drops below the threshold of the second comparator.

15. The multiple phase switching regulator of claim 9 wherein the first gain control circuit further comprises:

a resistor divider; and

a transistor coupled to the resistor divider and the first comparator, wherein the transistor shorts a resistor in the resistor divider when the load current is above the threshold of the first comparator.

16. The multiple phase switching regulator of claim 9 wherein the first gain control circuit further comprises:

first and second resistors coupled in parallel such that current flows through both resistors after the load current drops below the threshold of the first comparator.

17. The multiple phase switching regulator of claim 9 wherein the first gain control circuit comprises:

a resistor coupled to the feedback loop circuit;

a current mirror circuit coupled to the resistor and the second single phase switching regulator, wherein the current mirror adjusts the output current of the second single phase switching regulator.

19. The method of claim 18 wherein regulating the voltage at the output using the plurality of single phase switching regulators and the feedback loop circuit further comprises:

monitoring the output voltage using an amplifier that is coupled to at least one of the single phase switching regulators.

20. The method of claim 18 wherein the plurality of single phase switching regulators are synchronous switching regulators.

21. The method of claim 18 wherein the plurality of single phase switching regulators comprises three single phase switching regulators.

22. The method of claim 21 wherein preventing at least one of the single phase switching regulators from supplying current to the output at low load current in the first low power mode further comprises preventing two of the single phase switching regulators from outputting current to the load at low load current.

23. The method of claim 18 wherein the plurality of single phase switching regulators comprises four single phase switching regulators.

24. The method of claim 23 wherein preventing at least one of the single phase switching regulators from supplying current to the output at low load current in the first low power mode further comprises preventing three of the single phase switching regulators from outputting current to the load at low load current.

25. The method of claim 23 wherein preventing at least one of the single phase switching regulators from supplying current to the output at low load current in the first low power mode further comprises preventing two of the single phase switching regulators from outputting current to the load at low load current.

26. The method of claim 18 wherein current supplied to the output by at least one of the remaining single phase switching regulators in the first low power mode is increased after the load current drops below a threshold using a first gain control circuit.

27. The method of claim 26 wherein using the first gain control circuit further comprises:

monitoring an output signal of the feedback loop circuit and adjusting an inductor current threshold of at least one of the remaining single phase switching regulators using an amplifier.

28. The method of claim 26 wherein using the first gain control circuit further comprises:

shorting a resistor by turning ON a transistor coupled to the resistor when the load current drops below the load current threshold.

29. The method of claim 18 wherein preventing at least one of the single phase switching regulators from supplying current to the output at low load current in the first low power mode further comprises preventing at least one single phase switching regulator from supplying current to the output when the load current falls below a threshold of a first comparator that is coupled to the feedback loop circuit.

30. The method of claim 29 further comprising:

preventing a second single phase switching regulator from outputting current to the load when the load current drops below a threshold of a second comparator that is less than the threshold of the first comparator, in a second low power mode.

31. The method of claim 30 wherein a current supplied to the output by a third of the single phase switching regulators in the second low power mode is increased using a second gain control circuit after the load current drops below the threshold of the second comparator.

32. The method of claim 31 wherein a resistor is shorted by turning ON a transistor coupled to the resistor when the load current drops below the threshold of the second comparator.

33. The method of claim 29 wherein a resistor in a resistor divider is shorted only when the load current is above the threshold of the first comparator.

34. The method of claim 26 wherein a first resistor is coupled in parallel with a second resistor so that current flows through both resistors in the first low power mode.

35. The method of claim 18 wherein the plurality of single phase switching regulators comprises two single phase switching regulators.

37. The multiple phase switching regulator of claim 36 wherein:

the feedback loop circuit includes an amplifier coupled to at least one of the single phase switching regulators.

38. The multiple phase switching regulator of claim 36 wherein:

the means for causing the first of the single phase switching regulators to be OFF below the low load current threshold further comprises a first comparator coupled to the feedback loop circuit and the first single phase switching regulator.

39. The multiple phase switching regulator of claim 36 further comprising:

means for increasing an output current threshold of a second of the single phase switching regulators below the low load current threshold.

40. The multiple phase switching regulator of claim 39 wherein:

the means for increasing the output current threshold of the second single phase switching regulator below the low load current threshold further comprises means for shorting a resistor that determines the output current threshold.

41. The multiple phase switching regulator of claim 39 wherein:

the means for increasing the output current threshold of the second single phase switching regulator below the low load current threshold further comprises means for directing current through a resistor in a resistor divider after the load current falls below the low load current threshold.

42. The multiple phase switching regulator of claim 39 wherein:

the means for increasing the output current threshold of the second single phase switching regulator below the low load current threshold further comprises means for coupling a first resistor in parallel with a second resistor after the load current falls below the low load current threshold.

43. The multiple phase switching regulator of claim 39 wherein:

the means for increasing the output current threshold of the second single phase switching regulator in the first low power mode further comprises means for shorting a resistor coupled to a current mirror circuit after the load current falls below the low load current threshold.

44. The multiple phase switching regulator of claim 36 further comprising:

means for causing a second single phase switching regulators to be OFF at a second low load current threshold.

45. The multiple phase switching regulator of claim 44 further comprising:

means for increasing an output current threshold of a third of the single phase switching regulators below the second low load current threshold.

46. The multiple phase switching regulator of claim 36 wherein the plurality of single phase switching regulators are synchronous switching regulators.

47. The multiple phase switching regulator of claim 36 wherein the plurality of single phase switching regulators comprises three single phase switching regulators.

48. The multiple phase switching regulator of claim 36 wherein the plurality of single phase switching regulators comprises four single phase switching regulators.

50. The method of claim 49 wherein the single phase switching regulator disabled below the light load current threshold draws less quiescent current.

51. The method of claim 49 wherein the plurality of single phase switching regulators are synchronous switching regulators.

52. The method of claim 49 wherein the plurality of single phase switching regulators comprises three single phase switching regulators.

53. The method of claim 52 wherein disabling at least one of the single phase switching regulators below the light load current threshold further comprises disabling two of the single phase switching regulators at the light load current threshold.

54. The method of claim 49 wherein the plurality of single phase switching regulators comprises four single phase switching regulators.

55. The method of claim 54 wherein disabling at least one of the single phase switching regulators below the light load current threshold further comprises disabling three of the single phase switching regulators at the light load current threshold.

18. A method for supplying current from a multiple phase switching regulator to a load coupled to an output, the method comprising:

regulating the voltage at the output using a plurality of single phase switching regulators coupled to the output and a feedback loop circuit; and

preventing at least one of the single phase switching regulators from supplying current to the output at low load current in a first low power mode.

36. A multiple phase switching regulator, comprising:

means for regulating the voltage at an output using a plurality of single phase switching regulators and a feedback loop circuit; and

means for causing a first of the single phase switching regulators to be OFF below a low load current threshold.

49. A method for improving the efficiency of a multiple phase switching regulator at light load currents, the method comprising:

regulating an output voltage at an output capacitor using a plurality of single phase switching regulators; and

disabling at least one of the single phase switching regulators below a light load current threshold.