Method and apparatus for trimming current limit and frequency to maintain a constant maximum power

• US 6,747,443 B2
• Filed: 08/14/2002
• Issued: 06/08/2004
• Est. Priority Date: 08/31/2001
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Matthews, David Michael Hugh, Balakrishnan, Balu, Djenguerian, Alex B.
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US10/218,763
• Publication Number:
  US 20030043601A1
• Time in Patent Office: 664 Days
• Field of Search: 323/284, 323/282, 323/285, 323/901, 361/18
• US Class Current: 323/284
• CPC Class Codes: G05F 3/262 using field-effect transistors only
• CPC Class Codes: H02M 1/0093 wherein the output is created by adding a regulated voltage to or subtracting it from an unregulated input
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• 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
• CPC Class Codes: H02M 7/003 Constructional details, e.g. physical layout, assembly, wiring or busbar connections
• CPC Class Codes: H03K 17/0822 in field-effect transistor switches

Abstract

Methods and apparatuses to trim current limit (I_p) and frequency (f) to maintain a constant maximum power. In one aspect of the invention, a power supply regulator having a peak current limit detection threshold and an operating frequency is disclosed. The peak current limit threshold or the operating frequency are adjusted specifically to maintain the I_p^m·fⁿ product substantially constant from one power supply controller to another where m is substantially equal to 2 and n is substantially equal to 1. In another aspect of the invention, the power supply regulator has a control circuit having a control threshold current. The peak current limit threshold or the operating frequency are adjusted specifically to maintain the product of I_p^m·fⁿ divided by the control threshold current substantially constant from one power supply controller to another where m is substantially equal to 2 and n is substantially equal to 1.

Claims

1. A power supply regulator, comprising:

a power switch coupled between first and second terminals;

a control circuit coupled to switch the power switch;

a current limit circuit coupled to the power switch and the control circuit to control a current through the power switch during operation of the power supply regulator, the current limit circuit having a peak current limit threshold (I_p); and

an oscillator coupled to provide the control circuit an oscillating signal, the control circuit to switch the power switch in response to the oscillating signal, the oscillating signal having an operating frequency (f), wherein a maximum deliverable power value of a power supply to be regulated by the power supply regulator is trimmed during manufacture of the power supply to be a substantially constant value during operation of the power supply regulator, wherein the trimming of the maximum deliverable power value is separate from the control of the current through the power switch during operation of the power supply regulator.

2. The power supply regulator of claim 1 wherein at least one of the operating frequency (f) and the peak current limit threshold (I_p)are trimmed during manufacture in a way such that a product I_p^m·

fⁿ is substantially constant to keep the maximum deliverable power value substantially constant.

3. The power supply regulator of claim 2 wherein where m is substantially equal to 2 and n is substantially equal to 1.

4. The power supply regulator of claim 2 wherein the product of I_p^m·

fⁿ of the power supply regulator is substantially constant with a product of I_p^m·

fⁿ of of another power supply regulator.

5. The power supply regulator of claim 1, wherein the power supply regulator is part of a flyback converter power supply.

6. The power supply regulator of claim 1 wherein the power supply regulator is part of a buck converter power supply.

7. The power supply regulator of claim 1 wherein the operating frequency (f) is substantially constant during operation under all operating conditions of the power supply regulator.

8. The power supply regulator of claim 1 wherein the operating frequency (f) is substantially constant during operation under a fixed range of operating conditions of the power supply regulator.

9. A switched mode power supply, comprising:

an energy transfer element having an output coupled to an output of the switched mode power supply; and

a power supply regulator coupled to an input of the switched mode power supply and an input of the energy transfer element, the power supply regulator coupled to operate at an operating frequency (f) and coupled to detect a current flowing through the input of the energy transfer element substantially equal to a peak current limit threshold (I_p) wherein a maximum deliverable power value of the switched mode rower supply is trimmed during manufacture to be a substantially constant value during operation of the power supply regulator, wherein the trimming of the maximum deliverable power value is separate from control of the current flowing through the input of the energy transfer element during operation of the power supply regulator.

10. The switched mode power supply of claim 9 wherein at least one of the operating frequency (f) and the peak current limit threshold (I_p)are trimmed during manufacture in a way such that a product I_p^m·

fⁿ is substantially constant to keep the maximum deliverable power value substantially constant.

11. The switched mode power supply of claim 10 wherein where m is substantially equal to 2 and n is substantially equal to 1.

12. The switched mode power supply of claim 10 wherein the product of I_p^m·

fⁿ of the switched mode power supply is substantially constant with a product of I_p^m·

fⁿ of another switched mode power supply.

13. The switched mode power supply of claim 9 wherein the switched mode power supply is a flyback converter.

14. The switched mode power supply of claim 9 wherein the switched mode power supply is a buck converter.

15. The switched mode power supply of claim 9 wherein the operating frequency (f) of the switched mode power supply is substantially constant during operation under all operating conditions of the switched mode power supply.

16. The switched mode power supply of claim 9 wherein the operating frequency (f) of the switched mode power supply is substantially constant during operation under a fixed range of operating conditions of the switched mode power supply.

17. A method, comprising:

trimming to a substantially constant value during manufacture of a power supply a maximum deliverable power value of the power supply to be regulated by a power supply regulator;

switching a power switch of the power supply regulator at an operating frequency (f) during operation of the power supply regulator; and

controlling a current through the power switch to keen the current through the power switch below a peak current limit threshold (I_p) during operation of the power supply regulator.

18. The method of claim 17 wherein trimming the maximum deliverable power value comprises trimming at least one of the operating frequency (f) and the peak current limit threshold (I_p) during manufacture in a way such that a product I_p^m·

fⁿ is substantially constant to keep the maximum deliverable power value substantially constant.

19. The method of claim 18 wherein where m is substantially equal to 2 and n is substantially equal to 1.

20. The method of claim 18 wherein the product of I_p^m·

fⁿ of the power supply regulator is substantially constant with a product of I_p^m·

fⁿ of another power supply regulator.

21. The method of claim 17 wherein the power supply regulator is included in a flyback converter power supply.

22. The method of claim 17 wherein the power supply regulator is included in a buck converter power supply.

23. The method of claim 17 wherein the operating frequency (f) is substantially constant during operation under all operating conditions of the power supply regulator.

24. The method of claim 17 wherein the operating frequency (f) is substantially constant during operation under a fixed range of operating conditions of the power supply regulator.

25. A power supply regulator, comprising:

a power switch coupled between first and second terminals;

a control circuit coupled to switch the power switch, the control circuit having a control threshold current, above which the control circuit is adapted to reduce a duty cycle at which the power switch is switched during operation of the power supply regulator;

a current limit circuit coupled to the power switch and the control circuit to control a current through the power switch during operation of the power supply regulator the current limit circuit having a peak current limit threshold (I_p); and

an oscillator coupled to provide the control circuit an oscillating signal, the control circuit to switch the power switch in response to the oscillating signal during operation of the power supply regulator, the oscillating signal having an operating frequency (f), wherein a maximum deliverable power value of a power supply to be regulated by the power supply regulator is trimmed during manufacture of the power supply to be a substantially constant value during operation of the power supply regulator, wherein the trimming of the maximum deliverable power value is separate from the control of the current through the power switch during operation of the power supply regulator.

26. The power supply regulator of claim 25 wherein at least one of the operating frequency (f) and the peak current limit threshold (I_p)are trimmed during manufacture in a way such that a product I_p^m·

fⁿ divided by the control threshold current is substantially constant to keep the maximum deliverable power value substantially constant.

27. The power supply regulator of claim 26 wherein where m is substantially equal to 2 and n is substantially equal to 1.

28. The power supply regulator of claim 26 wherein the product of I_p^m·

fⁿ divided by the control threshold current of the power supply regulator is substantially constant with a product of I_p^m·

fⁿ divided by a control threshold current of another power supply regulator.

29. The power supply regulator of claim 25, wherein the power supply regulator is part of a flyback converter power supply.

30. The power supply regulator of claim 25 wherein the power supply regulator is part of a buck converter power supply.

31. The power supply regulator of claim 25 wherein the operating frequency (f) is substantially constant during operation under all operating conditions of the power supply regulator.

32. The power supply regulator of claim 25 wherein the operating frequency (f) is substantially constant during operation under a fixed range of operating conditions of the power supply regulator.