Master-slave critical conduction mode power converter

• US 20060077604A1
• Filed: 09/06/2005
• Published: 04/13/2006
• Est. Priority Date: 09/07/2004
• Status: Active Grant

• Current Assignee: MyPAQ Holdings Ltd. (Transpacific IP Group Limited)
• Original Assignee: Flextronics America LLC (Flextronics International Limited)
• Inventors: Jansen, Arian
• Granted Patent: US 7,205,752 B2
• Time in Patent Office: Days
• US Class Current: 361/90
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• 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 system and a method for to use multiple power sources for supplying power to a load. The system and method use a triggering system to automatically and substantially cancel a ripple component of the input current drawn by the system. A master power source and a slave power source supply power to the load. The triggering system results in the two power sources having switching frequencies that are substantially equal and switching cycles that are substantially 180° out of phase. Further, the method and the device contemplate the use of a local oscillator in the triggering system to ensure that the slave power source is triggered to the on position at a point in the switching cycle of the master power source that is approximately 180° out of phase with a leading edge of the master switching drive signal. The system and method are advantageously used to provide a power factor correction front-end for a switch-mode power supply. Power supplies with a diverse array of relationships between power supplied and switching frequency can be used.

Claims

1. A system for supplying power to a load, the system comprising:

a. a first and a second power source, each having a control system; and

,

b. means for detecting a switch-off event in the first power source and subsequently triggering a switch-on event in the second power source, the means comprising means for directly supplying the same signal to both the switch of the first power source and to the control system of the second power source;

wherein the first and second power source have similar noise characteristics.

2. The system of claim 1 wherein the first power source has a switching waveform comprising a frequency and a duty cycle further wherein the duty cycle is modulated by a first feedback system taking inputs comprising a signal proportional to the power supplied by the system, further wherein the frequency is modulated by a second feedback system taking inputs comprising a signal proportional to a current present in the first power source.

3. The system of claim 2 wherein the second feedback system comprises means for detecting the absence of the current in the first power source and subsequently signaling the control system of the first power source to trigger the switch-off event of the first power source.

4. The system of claim 3 wherein the subsequent signaling of the control system comprises means for delaying the signaling to take advantage of a known oscillatory behavior of the current in the first power source so that the current has a maximum absolute amplitude at the switch-off event of the first power source.

5. The system of claim 1 wherein the second power source has a switching waveform comprising a frequency and a duty cycle wherein the frequency is determined by the triggering of the switch-on event in the second power source, further wherein the duty cycle is modulated by a third feedback system taking inputs comprising a signal proportional to a current present in the second power source, a signal proportional to the power supplied by the system, and a desired switching event.

6. The system of claim 5 wherein the desired switching event is indirectly triggered by a switch-off event in the first power source.

7. The system of claim 6 wherein the third feedback system compares the desired switching event to a point in time at which the current in the first power source is substantially zero and creates a signal representative of the difference in time between those points and provides it to the control system, wherein the control system uses the signal representative of the time difference to intelligently modulate the duty cycle of the second power source.

8. A system for supplying power to a load, the system comprising:

a. a first and a second power source, each having a control system; and

,

b. means for detecting a switch-off event in the first power source and subsequently triggering a switch-on event in the second power source, the means comprising means for directly supplying the same signal to both the switch of the first power source and to the control system of the second power source, wherein the means for detecting comprises means for directly supplying the same signal to both the switch of the first power source and to a processing system responsible for then supplying a signal to the control system of the second power source;

wherein the first and second power source have similar noise characteristics.

9. The system of claim 8 wherein the processing system comprises means for producing a waveform with substantially the same frequency as the waveform of the first power source, also substantially 180°

out of phase with the first power source, and with a duty cycle that is substantially 50%, further wherein this waveform is the signal supplied to the control system of the second power source.

10. The system of claim 8 wherein the first power source has a switching waveform comprising a frequency and a duty cycle further wherein the duty cycle is modulated by a first feedback system taking inputs comprising a signal proportional to the power supplied by the system, further wherein the frequency is modulated by a second feedback system taking inputs comprising a signal proportional to a current present in the first power source.

11. The system of claim 10 wherein the second feedback system comprises means for detecting the absence of the current in the first power source and subsequently signaling the control system of the first power source to trigger the switch-off event of the first power source.

12. The system of claim 11 wherein the subsequent signaling of the control system comprises means for delaying the signaling to take advantage of a known oscillatory behavior of the current in the first power source so that the current has a maximum absolute amplitude at the switch-off event of the first power source.

13. The system of claim 8 wherein the second power source has a switching waveform comprising a frequency and a duty cycle wherein the frequency is determined by the triggering of the switch-on event in the second power source, further wherein the duty cycle is modulated by a third feedback system taking inputs comprising a signal proportional to a current present in the second power source, a signal proportional to the power supplied by the system, and a desired switching event.

14. The system of claim 13 wherein the desired switching event is indirectly triggered by a switch-off event in the first power source.

15. The system of claim 14 wherein the third feedback system compares the desired switching event to a point in time at which the current in the first power source is substantially zero and creates a signal representative of the difference in time between those points and provides it to the control system, wherein the control system uses the signal representative of the time difference to intelligently modulate the duty cycle of the second power source.

16. The system of claim 14 wherein the third feedback system further comprises means for preventing switching from occurring when an undesirable amount of current remains in the second power source.

17. A system for providing power factor correction to a power supply, the system comprising:

a. first and second power sources for supplying input power to the power supply, wherein each power source has a similar relationship between the power supplied by the power source and the switching frequency of the power source, further wherein each power source has similar characteristic noise in the output of the power source, further wherein the second source has a characteristic switching duty cycle;

b. means for detecting a switch-off event in the first power source and subsequently triggering a switch-on event in the second power source; and

c. means for modulating the duty cycle of the second power source to control the times at which switch-off events in the second power source occur.

18. The system of claim 17 wherein the means for detecting comprises means for directly supplying the same signal to both the switch of the first power source and to the control system of the second power source.

19. The system of claim 18 wherein the first power source has a switching waveform comprising a frequency and a duty cycle further wherein the duty cycle is modulated by a first feedback system taking inputs comprising a signal proportional to the power supplied by the system, further wherein the frequency is modulated by a second feedback system taking inputs comprising a signal proportional to a current present in the first power source.

20. The system of claim 19 wherein the second feedback system comprises means for detecting the absence of the current in the first power source and subsequently signaling the control system of the first power source to trigger the switch-off event of the first power source.

21. The system of claim 20 wherein the subsequent signaling of the control system comprises means for delaying the signaling to take advantage of a known oscillatory behavior of the current in the first power source so that the current has a maximum absolute amplitude at the switch-off event of the first power source.

22. The system of claim 18 wherein the second power source has a switching waveform comprising a frequency and a duty cycle wherein the frequency is determined by the triggering of the switch-on event in the second power source, further the means for modulating the duty cycle of the second power source is a third feedback system taking inputs comprising a signal proportional to a current present in the second power source, a signal proportional to the power supplied by the system, and a desired switching event.

23. The system of claim 22 wherein the desired switching event is indirectly triggered by a switch-off event in the first power source.

24. The system of claim 23wherein the third feedback system compares the desired switching event to a point in time at which the current in the first power source is substantially zero and creates a signal representative of the difference in time between those points and provides it to the control system, wherein the control system uses the signal representative of the time difference to intelligently modulate the duty cycle of the second power source.

25. The system of claim 17 wherein the means for detecting comprises means for directly supplying the same signal to both the switch of the first power source and to a processing system responsible for then supplying a signal to the control system of the second power source.

26. The system of claim 25 wherein the processing system comprises means for producing a waveform with substantially the same frequency as the waveform of the first power source, also substantially 180°

out of phase with the first power source, and with a duty cycle that is substantially 50%, further wherein this waveform is the signal supplied to the control system of the second power source.

27. The system of claim 25 wherein the first power source has a switching waveform comprising a frequency and a duty cycle further wherein the duty cycle is modulated by a first feedback system taking inputs comprising a signal proportional to the power supplied by the system, further wherein the frequency is modulated by a second feedback system taking inputs comprising a signal proportional to a current present in the first power source.

28. The system of claim 27 wherein the second feedback system comprises means for detecting the absence of the current in the first power source and subsequently signaling the control system of the first power source to trigger the switch-off event of the first power source.

29. The system of claim 28 wherein the subsequent signaling of the control system comprises means for delaying the signaling to take advantage of a known oscillatory behavior of the current in the first power source so that the current has a maximum absolute amplitude at the switch-off event of the first power source.

30. The system of claim 25 wherein the second power source has a switching waveform comprising a frequency and a duty cycle wherein the frequency is determined by the triggering of the switch-on event in the second power source, further wherein the duty cycle is modulated by a third feedback system taking inputs comprising a signal proportional to a current present in the second power source, a signal proportional to the power supplied by the system, and a desired switching event.

31. The system of claim 30 wherein the desired switching event is indirectly triggered by a switch-off event in the first power source.

32. The system of claim 31 wherein the third feedback system compares the desired switching event to a point in time at which the current in the first power source is substantially zero and creates a signal representative of the difference in time between those points and provides it to the control system, wherein the control system uses the signal representative of the time difference to intelligently modulate the duty cycle of the second power source.

33. The system of claim 31 wherein the third feedback system further comprises means for preventing switching from occurring when an undesirable amount of current remains in the second power source.

34. A method for providing power factor correction to a power supply, the method comprising:

a. coupling a first and a second power source so that both power sources receive power from the same source and output power to the same load;

wherein both power sources have a switching cycle;

b. configuring the first power source in a self-resonant way such that it determines a switching frequency for its own switching cycle;

c. configuring the second power source to switch-on when the first power source switches off, whereby the switching cycle of the second power source has a switching frequency approximately equal to the switching frequency of the first power source; and

,

d. modulating the duty cycle of the second power source so that the switch-off event of the second power source occurs at an optimal time relative to a current that exists in the second power source.

35. A method for providing power factor correction to a power supply, the method comprising:

a. coupling a first and a second power source so that both power sources receive power from the same source and output power to the same load;

wherein both power sources have a switching cycle;

b. configuring the first power source in a self-resonant way such that it determines a switching frequency for its own switching cycle;

c. configuring a local oscillator to produce a waveform with a duty cycle of approximately 50% at a frequency equal to the switching frequency of the first power source and further in phase alignment with the switching frequency of the first power source;

d. configuring the second power source to operate at a switching frequency approximately 180°

out of phase with the waveform produced by the local oscillator, whereby the switching cycle of the second power source has a switching frequency approximately equal to the switching frequency of the first power source and approximately 180°

out of phase with the switching frequency of the first power source; and

,

e. modulating the duty cycle of the second power source so that the switch-off event of the second power source occurs at an optimal time relative to a current that exists in the second power source.