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

• US 20030043601A1
• Filed: 08/14/2002
• Published: 03/06/2003
• 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.
• Granted Patent: US 6,747,443 B2
• Time in Patent Office: Days
• US Class Current: 363/21.12
• 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, 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 at least one of the peak current limit threshold (I_p) and the operating frequency (f) are adjusted to maintain a product of I_p^m·

fⁿ substantially constant.

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

3. The power supply regulator of claim 1 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.

4. The power supply regulator of claim 1 wherein said at least one of the peak current limit threshold (I_p) and the operating frequency (f) are adjusted during manufacture of the 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.

16. The switched mode power supply of claim 8 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.

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 detection threshold (I_p), wherein at least one of the peak current limit detection threshold (I_p) and the operating frequency (f) are adjusted to maintain a product of I_p^m·

fⁿ substantially constant.

10. The switched mode power supply of claim 9 wherein where m is substantially equal to 2 and n is substantially equal to 1.

11. The switched mode power supply of claim 9 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.

12. The switched mode power supply of claim 9 wherein said at least one of the peak current limit threshold (I_p) and the operating frequency (f) are adjusted during manufacture of the 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.

17. A method, comprising:

switching a power switch of a power supply regulator at an operating frequency (f);

measuring a current through the power switch and maintaining the current through the power switch below a peak current limit threshold (I_p); and

adjusting at least one of the peak current limit threshold (I_p) and the operating frequency (f) to maintain a product of I_p^m·

fⁿ substantially constant.

18. The method of claim 17 wherein where m is substantially equal to 2 and n is substantially equal to 1.

19. The method of claim 17 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.

20. The method of claim 17 wherein said adjusting at least one of the peak current limit threshold (I_p) and the operating frequency (f) occurs during manufacture of the 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;

a current limit circuit coupled to the power switch and the control circuit to control a current through the power switch, 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 at least one of the peak current limit threshold (I_p) and the operating frequency (f) are adjusted to maintain a product of I_p^m·

fⁿ divided by the control threshold current substantially constant.

26. The power supply regulator of claim 25 wherein where m is substantially equal to 2 and n is substantially equal to 1.

27. The power supply regulator of claim 25 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.

28. The power supply regulator of claim 25 wherein said at least one of the peak current limit threshold (I_p) and the operating frequency (f) are adjusted during manufacture of the 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.