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

• US 6,992,471 B2
• Filed: 03/02/2005
• Issued: 01/31/2006
• Est. Priority Date: 08/31/2001
• Status: Expired due to Fees

• 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:
  US11/071,380
• Publication Number:
  US 20050146900A1
• Time in Patent Office: 335 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 circuit, comprising:

control circuitry coupled to a power transistor;

an oscillator coupled to the control circuitry, the control circuitry to switch the power transistor in response to the oscillator;

current limit circuitry coupled to the power transistor and the control circuitry to limit a current through the power transistor; and

trim circuitry coupled to the oscillator and the current limit circuitry, the trim circuitry to be trimmed during manufacture of the circuit to determine a maximum deliverable power value of a power supply such that the maximum deliverable power of the power supply is substantially constant with a maximum deliverable power of another power supply.

2. The circuit of claim 1 wherein the trim circuitry comprises:

frequency trim circuitry coupled to the oscillator; and

peak current limit threshold trim circuitry coupled to the current limit circuitry.

3. The circuit of claim 2 wherein the an operating frequency f of the oscillator is determined in response to the frequency trim circuitry and a peak current limit threshold (I_p) is determined in response to the peak current limit threshold trim circuitry.

4. The circuit of claim 3 wherein the frequency trim circuitry and the peak current limit threshold trim circuitry are trimmed during manufacture of the power supply such that a product of a square of the peak current limit threshold I_p and the operating frequency f is substantially constant with a product of a square of a peak current limit threshold I_p and an operating frequency f of another power supply.

5. The circuit of claim 1, wherein the circuit is included in a flyback converter power supply.

6. The circuit of claim 1 wherein the circuit is included in a buck converter power supply.