POWER CONVERSION SYSTEM AND POWER CONVERSION METHOD

• US 20150365002A1
• Filed: 06/12/2015
• Published: 12/17/2015
• Est. Priority Date: 06/13/2014
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: CAO, Yu, WANG, Kezhi
• Granted Patent: US 9,667,152 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02M 3/285 Single converters with a plurality of output stages connected in parallel parallel operation of a plurality of converters in dc distribution networks H02J1/10
• 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

A power conversion system includes at least two power converters and a current sharing bus, each power converter including a switching circuit, a power conversion circuit configured to receive an input voltage via the switching circuit and to provide a local output current, an output sense circuit configured to detect the local output current and to generate a local output current sense signal, a current sharing terminal coupled to the local output current sense signal via a resistor and coupled to the current sharing bus; and a PWM controller configured to adjust a duty cycle of the switching circuit based at least in part on the local output current sense signal provided by the output sense circuit and an average current signal on the current sharing bus.

Claims

1. A power conversion system comprising:

at least two power converters; and

a current sharing bus;

wherein

each of the at least two power converters includes;

a switching circuit;

a power conversion circuit configured to receive an input voltage via the switching circuit and to provide a local output current;

an output sense circuit configured to detect the local output current and to generate a local output current sense signal;

a current sharing terminal coupled to the local output current sense signal via a resistor and coupled to the current sharing bus; and

a PWM controller configured to adjust a duty cycle of the switching circuit based at least in part on the local output current sense signal provided by the output sense circuit and an average current signal on the current sharing bus.

2. The power conversion system of claim 1, wherein each of the at least two power converters includes an error amplifier configured to receive the local output current sense signal and the average current signal to generate a current sharing error signal, and the PWM controller is configured to adjust the duty cycle of the switching circuit according to the current sharing error signal.

3. The power conversion system of claim 1, wherein in each of the at least two power converters:

if the local output current sense signal is higher than the average current signal, the duty cycle of the switching circuit is decreased;

or

if the local output current sense signal is lower than the average current signal, the duty cycle of the switching circuit is increased.

4. The power conversion system of claim 1, wherein

the output sense circuit is configured to detect a local output voltage of the power conversion circuit and generate a local output voltage sense signal;

the PWM controller is configured to adjust the duty cycle of the switching circuit further based on the local output voltage sense signal.

5. The power conversion system of claim 1, wherein each of the at least two power converters includes an input voltage sense circuit configured to detect the input voltage and generate an input voltage sense signal, and the PWM controller is configured to adjust the duty cycle of the switching circuit further based on the input voltage sense signal provided by the input voltage sense circuit.

6. The power conversion system of claim 5, wherein if the input voltage sense signal indicates a change in the input voltage, the PWM controller adjusts the duty cycle of the switching circuit within a preset range such that a change rate of the output voltage is lower than a change rate of the input voltage.

7. The power conversion system of claim 5, wherein each of the at least two power converters includes:

a reference voltage module configured to generate a reference voltage based on the input voltage sense signal provided by the input voltage sense circuit such that the reference voltage is proportional to the input voltage; and

a first operational amplifier configured to generate a first comparison signal based on a difference between a local output voltage sense signal and the reference voltage, the local output voltage sense signal being generated by the output sense circuit detecting a local output voltage of the power conversion circuit, the first comparison signal being provided to the PWM controller as a feedback signal;

wherein

the PWM controller is configured to adjust the duty cycle of the switching circuit within a preset range according to the feedback signal such that the output voltage is maintained at a level proportional to the reference voltage.

8. The power conversion system of claim 7, each of the at least two power converters includes a second operational amplifier configured to generate a second comparison signal based on a difference between the local output current sense signal and the first comparison signal, the second comparison signal being provided to the PWM controller as the feedback signal.

9. The power conversion system of claim 6, wherein

if the input voltage changes, the output voltage varies along with the input voltage;

and

if the input voltage does not change, the PWM controller adjusts the duty cycle of the switching circuit within a preset range such that the output voltage remains unchanged.

10. The power conversion system of claim 1, wherein the power converter is an isolated power converter, and includes an isolator to transfer signals in an isolated manner between a primary side and a secondary side of the power converter.

11. A method for controlling a power conversion system including at least two power converters and a current sharing bus, the method comprising the steps of, in each power converter:

receiving an input voltage via a switching circuit and providing a local output current;

detecting the local output current and generating a local output current sense signal;

coupling the local output current sense signal to the current sharing bus via a resistor; and

adjusting a duty cycle of the switching circuit based at least in part on the local output current sense signal and an average current signal on the current sharing bus.

12. The method of claim 11, further comprising the step of, in each power converter, generating a current sharing error signal according to a difference between the local output current sense signal and the average current signal, and adjusting the duty cycle of the switching circuit according to the current sharing error signal.

13. The method of claim 11, further comprising the steps of, in each power converter:

decreasing the duty cycle of the switching circuit if the local output current sense signal is higher than the average current signal;

or

increasing the duty cycle of the switching circuit if the local output current sense signal is lower than the average current signal.

14. The method of claim 11, further comprising the steps of, in each power converter:

detecting a local output voltage and generating a local output voltage sense signal; and

adjusting the duty cycle of the switching circuit further based on the local output voltage sense signal.

15. The method of claim 11, further comprising the steps of, in each power converter, detecting an input voltage and generating an input voltage sense signal, and adjusting the duty cycle of the switching circuit further based on the input voltage sense signal.

16. The method of claim 15, further comprising, if the input voltage sense signal indicates a change in the input voltage, adjusting the duty cycle of the switching circuit within a preset range such that a change rate of the output voltage is lower than a change rate of the input voltage.

17. The method of claim 15, further comprising the steps of, in each power converter:

generating a reference voltage based on the input voltage sense signal such that the reference voltage is proportional to the input voltage;

generating a first comparison signal as a feedback signal based on a difference between a local output voltage sense signal and the reference voltage, the local output voltage sense signal being generated by detecting a local output voltage; and

adjusting the duty cycle of the switching circuit within a preset range according to the feedback signal such that the output voltage is maintained at a level proportional to the reference voltage.

18. The method of claim 17, further comprising the step of, in each power converter, generating a second comparison signal as the feedback signal based on a difference between the local output current sense signal and the first comparison signal.

19. The method of claim 16, wherein:

if the input voltage changes, the output voltage varies along with the input voltage; and

if the input voltage does not change, the duty cycle of the switching circuit is adjusted within a preset range such that the output voltage remains unchanged.

20. The method of claim 11, wherein the power converter is an isolated power converter, and includes an isolator to transfer signals in an isolated manner between a primary side and a secondary side of the power converter.

21. A power conversion system comprising:

at least two power converters; and

a current sharing bus;

wherein

each of the at least two power converters include;

means for receiving an input voltage via a switching circuit and providing a local output current;

means for detecting the local output current and generating a local output current sense signal;

means for coupling the local output current sense signal to the current sharing bus via a resistor; and

means for adjusting a duty cycle of the switching circuit based at least in part on the local output current sense signal and an average current signal on the current sharing bus.

22. The power conversion system of claim 21, wherein each of the at least two power converters includes:

means for generating a current sharing error signal according to a difference between the local output current sense signal and the average current signal; and

means for adjusting the duty cycle of the switching circuit according to the current sharing error signal.

23. The power conversion system of claim 21, wherein each of the at least two power converters includes:

means for decreasing the duty cycle of the switching circuit if the local output current sense signal is higher than the average current signal; and

means for increasing the duty cycle of the switching circuit if the local output current sense signal is lower than the average current signal.

24. The power conversion system of claim 21, wherein each of the at least two power converters includes:

means for detecting a local output voltage and generating a local output voltage sense signal; and

means for adjusting the duty cycle of the switching circuit further based on the local output voltage sense signal.

25. The power conversion system of claim 21, wherein each of the at least two power converters includes:

means for detecting an input voltage and generating an input voltage sense signal; and

means for adjusting the duty cycle of the switching circuit further based on the input voltage sense signal.

26. The power conversion system of claim 25, wherein each of the at least two power converters includes:

means for adjusting the duty cycle of the switching circuit within a preset range if the input voltage sense signal indicates a change in the input voltage such that a change rate of the output voltage is lower than a change rate of the input voltage.

27. The power conversion system of claim 25, wherein each of the at least two power converters includes:

means for generating a reference voltage based on the input voltage sense signal such that the reference voltage is proportional to the input voltage;

means for generating a first comparison signal as a feedback signal based on a difference between a local output voltage sense signal and the reference voltage, the local output voltage sense signal being generated by detecting a local output voltage; and

means for adjusting the duty cycle of the switching circuit within a preset range according to the feedback signal such that the output voltage is maintained at a level proportional to the reference voltage.

28. The power conversion system of claim 27, wherein each of the at least two power converters includes:

means for generating a second comparison signal as the feedback signal based on a difference between the local output current sense signal and the first comparison signal.

29. The power conversion system of claim 26, wherein if the input voltage changes, the output voltage varies along with the input voltage, and each of the at least two power converters includes:

means for adjusting the duty cycle of the switching circuit within a preset range if the input voltage does not change, such that the output voltage remains unchanged.

30. The power conversion system of claim 21, wherein the power converter is an isolated power converter, and includes an isolator to transfer signals in an isolated manner between a primary side and a secondary side of the power converter.