High-speed charge-mode controller for a multi-phase switched-mode power converter

• US 6,462,521 B1
• Filed: 07/17/2001
• Issued: 10/08/2002
• Est. Priority Date: 07/17/2001
• Status: Expired due to Fees

• Current Assignee: Semtech Corporation
• Original Assignee: Semtech Corporation
• Inventors: Yang, Eric X., Newlin, Trevor M.
• Primary Examiner(s): Patel, Rajnikant B.
• Application Number:
  US09/908,007
• Time in Patent Office: 448 Days
• Field of Search: 363/65, 363/25, 363/26, 363/71, 323/282, 323/284, 323/272, 323/266, 323/267, 323/312, 323/315, 323/222, 323/224, 323/288, 318/46, 318/53, 375/371, 375/376
• US Class Current: 323/272
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel

Abstract

A multiphase controller for a PWM power converter employs a single current sense device to measure input current, I, and an integrator at each phase to accurately measure power delivered during a pulse. The integrator monitors current delivered through a circuit which delivers a current signal scaled to I/N where N is the number of active phases. Thus where there are three overlapping phases, one-third of I is delivered to the integrator for each phase that is on or active. The integrator provides a Charge Ramp signal to an input of a Pulse Width Modulation (PWM) comparator associated with each phase. The other input of the PWM comparator is tied to an error control signal common to all of the phases. When the Charge Ramp signal and the error control signal match, the corresponding phase is turned off for the duration of the cycle.

Claims

1. An N-phase controller for a switched-mode power converter, N being an integer of 1 or greater, said controller comprising associated with a first phase:

a current mirror circuit providing N separate current signals proportional to a total current I used by the converter, said N signals respectively comprising a current proportional to I/n for n=1 to N;

a current level decoder coupled to a source of an ON/OFF control signal for each of said N phases, said current level decoder providing a signal indicating a number, K, of phases currently ON;

a current selector coupled to said current level decoder and to said current mirror circuit, said current selector having an output proportional to I/K; and

a charge ramp circuit coupled to said current selector and integrating a signal from said output of said current selector while said first phase is ON.

2. An apparatus in accordance with claim 1, wherein said charge ramp circuit comprises a capacitor.

4. An apparatus in accordance with claim 2, wherein said charge ramp circuit comprises a capacitor.

3. A multi-phase controller for a switched-mode power converter, said controller including circuitry associated with each phase comprising:

a current mirror circuit providing N (where N is the number of phases in the converter) separate current signals proportional to a total current I used by the converter, said N signals respectively comprising a current proportional to I/n for n=1 to N;

a current level decoder coupled to a source of an ON/OFF control signal for each of said N phases, said current level decoder providing a signal indicating a number, K, of phases currently ON;

a current selector coupled to said current level decoder and to said current mirror circuit, said current selector having an output proportional to I/K; and

a charge ramp circuit coupled to said current selector and integrating a signal from said output of said current selector while the phase in ON.

5. A method for controlling an N-phase switched-mode power converter, said method comprising:

monitoring a total current I used by the converter;

generating N separate current signals proportional to I, said N current signals respectively comprising a current proportional to I/n for n=1 to N;

detecting a number, K, of phases turned ON;

selecting one of said N current signals based on K;

integrating said selected signal to form a Charge Ramp signal;

comparing said integrated Charge Ramp signal with an error signal; and

turning off a phase when its corresponding Charge Ramp signal is not less than said error signal.

6. A method in accordance with claim 5, wherein said monitoring is accomplished with a resistor.

7. A method in accordance with claim 6, wherein said resistor has a resistance of less than or equal to 0.005 ohms.

8. A method in accordance with claim 5, wherein said generating is accomplished with a current mirror circuit.

9. A method in accordance with claim 5, wherein said integrating is accomplished with a capacitor.

10. A method in accordance with claim 5, wherein said comparing is accomplished with a comparator.

11. A method in accordance with claim 9, further comprising:

shorting said capacitor when said phase is turned off.

12. A method for controlling an N-phase switched-mode power converter, said method comprising:

monitoring a total current, I, used by all phases of the converter;

generating in controller circuitry associated with each phase of the converter N separate current signals proportional to I, said N signals respectively comprising a current proportional to I/n for n=1 to N;

detecting a number, K, of phases of the converter turned ON;

selecting in controller circuitry associated with each phase of the converter one of said N current signals based on K;

integrating in controller circuitry associated with each phase of the converter said selected signal to form a charge ramp signal;

comparing in controller circuitry associated with each phase of the converter said Charge Ramp signal with an error signal; and

turning off a phase when its corresponding Charge Ramp signal is not less than said error signal.

13. A method in accordance with claim 12, wherein said monitoring is accomplished with a resistor.

14. A method in accordance with claim 13, wherein said resistor has a resistance of less than or equal to 0.005 ohms.

15. A method in accordance with claim 12, wherein said generating is accomplished with a current mirror circuit.

16. A method in accordance with claim 12, wherein said integrating is accomplished with a capacitor.

17. A method in accordance with claim 12, wherein said comparing is accomplished with a comparator.

18. A method in accordance with claim 16, further comprising:

shorting said capacitor when said phase is turned off.

19. An apparatus for controlling an N-phase switched-mode power converter, said apparatus comprising:

means for monitoring a total current I used by the converter;

means for generating N separate current signals proportional to I, said N current signals respectively comprising a current proportional to I/n for n=1 to N;

means for detecting a number, K, of phases turned ON;

means for selecting one of said N current signals based on K;

means for integrating said selected signal to form a Charge Ramp signal;

means for comparing said integrated Charge Ramp signal with an error signal; and

means for turning off a phase when its corresponding Charge Ramp signal is not less than said error signal.

20. An apparatus in accordance with claim 19, wherein said means for monitoring includes a resistor.

21. An apparatus in accordance with claim 20, wherein said resistor has a resistance of less than or equal to 0.005 ohms.

22. An apparatus in accordance with claim 19, wherein said means for generating includes a current mirror.

23. An apparatus in accordance with claim 19, wherein said means for integrating includes a capacitor.

24. An apparatus in accordance with claim 19, wherein said means for comparing includes a comparator.

25. An apparatus in accordance with claim 23, further comprising means for shorting said capacitor when said phase is turned off.

26. An apparatus for controlling an N-phase switched-mode power converter, said method comprising:

means for monitoring a total current, I, used by all phases of the converter;

means for generating in controller circuitry associated with each phase of the converter N separate current signals proportional to I, said N signals respectively comprising a current proportional to I/n for n=1 to N;

means for detecting a number, K, of phases of the converter turned ON, means for selecting in controller circuitry associated with each phase of the converter one of said N current signals based on K;

means for integrating in controller circuitry associated with each phase of the converter said selected signal to form a charge ramp signal;

means for comparing in controller circuitry associated with each phase of the converter said Charge Ramp signal with an error signal; and

means for turning off a phase when its corresponding Charge Ramp signal is not less than said error signal.

27. An apparatus in accordance with claim 26, wherein said means for monitoring includes a resistor.

28. An apparatus in accordance with claim 27, wherein said resistor has a resistance of less than or equal to 0.005 ohms.

29. An apparatus in accordance with claim 26, wherein said means for generating includes a current mirror.

30. An apparatus in accordance with claim 26, wherein said means for integrating includes a capacitor.

31. An apparatus in accordance with claim 26, wherein said means for comparing includes a comparator.

32. An apparatus in accordance with claim 30, further comprising means for shorting said capacitor when said phase is turned off.