Master-slave critical conduction mode power converter

• US 7,205,752 B2
• Filed: 09/06/2005
• Issued: 04/17/2007
• 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
• Primary Examiner(s): Riley; Shawn
• Application Number:
  US11/220,876
• Publication Number:
  US 20060077604A1
• Time in Patent Office: 588 Days
• Field of Search: 323/272, 323/271, 323/224
• US Class Current: 323/272
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02M 1/4225 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;

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 a first signal to both a switch of the first power source and to the control system of the second power source; and

c. a feedback mechanism configured to monitor a switching state of the second power source and to continuously adjust a duty cycle of the second power source according to the switching state, wherein the feedback mechanism is further configured to trigger a switch-off event in the second power source when a residual power supply current within the second power source is substantially equal to zero,

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 determined by a second feedback system taking inputs comprising a signal proportional to a power supply 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 power supply 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 power supply current in the first power source so that a voltage across a switching element of the first power source is minimized.

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 a 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 power supply 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 the switch-off event in the first power source.

7. The system of claim 6, wherein the third feedback system is configured to determine a difference between the desired switching event and the power supply current in the second power source, wherein the control system uses a signal representative of the difference to continuously adjust 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, wherein the means for detecting comprises means for directly supplying a first signal to both a switch of the first power source and to an oscillator circuit coupled between the first power source and the second power source responsible for then supplying a control signal to the control system of the second power source, wherein the oscillator circuit includes a voltage controlled oscillator configured to receive the first signal from the first power source and to generate the control signal such that a frequency of the control signal is equal to a frequency of the first signal;

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

9. The system of claim 8, wherein the control signal has a waveform with substantially the same frequency as a 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%.

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 determined by a second feedback system taking inputs comprising a signal proportional to a power supply 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 power supply 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 power supply current in the first power source so that a voltage across a switching element of the first power source is minimized.

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 a 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 power supply 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 the switch-off event in the first power source.

15. The system of claim 14, wherein the third feedback system is configured to determine a difference between the desired switching event and a power supply current in the second power source, wherein the control system uses a signal representative of the difference to continuously adjust 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 the power supply current in the second power supply is greater than zero.

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

a. first and second power sources, 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;

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

c. means for modulating the duty cycle of the second power source according to present characteristics of the second power source; and

d. an oscillating circuit including a voltage controlled oscillator configured to receive the first signal and to generate a control signal with a second frequency for triggering the switch-on event in the second power source, wherein the first frequency is equal to the second frequency.

18. The system of claim 17, wherein the means for detecting comprises means for directly supplying the first signal to both a switch of the first power source and to the oscillating circuit.

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 determined by a second feedback system taking inputs comprising a signal proportional to a power supply 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 power supply 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 power supply current in the first power source so that a voltage across a switching element of the first power source is minimized.

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 a 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 power supply 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 the switch-off event in the first power source.

24. The system of claim 23 wherein, the third feedback system is configured to determine a difference between the desired switching event and a power supply current in the second power source, wherein the control system uses a signal representative of the difference to continuously modulate the duty cycle of the second power source.

25. The system of claim 24, wherein the control system has a waveform with substantially the same frequency as a 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%.

26. The system of claim 24, wherein the third feedback system further comprises means for preventing switching from occurring when the power supply current in the second power source is greater than zero.

27. 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 the first power source has a first switching cycle and the second power source has a second switching cycle;

b. configuring the first power source to be self-resonant such that the first power source determines a switching frequency of the first switching cycle;

c. configuring the second power source to switch-on when the first power source switches off, whereby the second 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 a duty cycle of the second power source so that a switch-off event of the second power source occurs when a power supply current within the second power source is substantially equal to zero.

28. 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 a 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.