Method and apparatus providing a multi-function terminal for a power supply controller

• US 6,356,464 B1
• Filed: 10/26/2000
• Issued: 03/12/2002
• Est. Priority Date: 09/24/1999
• Status: Expired due to Term

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Balakrishnan, Balu, Lund, Leif O., Djenguerian, Alex B.
• Primary Examiner(s): HAN, YOUNGHUIE JESSICA
• Application Number:
  US09/698,816
• Time in Patent Office: 502 Days
• Field of Search: 363/20, 363/21.01, 363/50, 363/55, 363/56.01, 363/56.09, 363/97, 323/299, 323/300, 323/284, 361/18, 361/90, 361/92
• US Class Current: 363/21.01
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• 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 supply controller having a multi-function terminal. In one embodiment, a power supply controller for switched mode power supply includes a drain terminal, a source terminal, a control terminal and a multi-function terminal. The multi-function terminal may be configured in a plurality of ways providing any one or some of a plurality of functions including on/off control, external current limit adjustments, under-voltage detection, over-voltage detection and maximum duty cycle adjustment. The operation of the multi-function terminal varies depending on whether a positive or negative current flows through the multi-function terminal. A short-circuit to ground from the multi-function terminal enables the power supply controller. A short-circuit to a supply voltage from the multi-function terminal disables the power supply controller. The current limit of an internal power switch of the power supply controller may be adjusted by externally setting a negative current from the multi-function terminal. The multi-function terminal may also be coupled to the input DC line voltage of the power supply through a resistance to detect an under-voltage condition, an over-voltage condition and/or adjust the maximum duty cycle of power supply controller. Synchronization of the oscillator of the power supply controller may also be realized by switching the multi-function terminal to power or ground at the desired times.

Claims

1. A method for controlling a power supply, comprising:

receiving a first current representative of an input voltage to the power supply through a first terminal of a power supply controller;

activating an under-voltage signal if the first current falls below a first under-voltage threshold value;

deactivating the under-voltage signal if the first current rises above a second under-voltage threshold value;

activating the power supply in response to said deactivated under-voltage signal; and

deactivating the power supply in response to said activated under-voltage signal.

2. The method of claim 1 wherein the second under-voltage threshold value is greater than the first under-voltage threshold value.

3. The method of claim 1 further comprising generating a positive current sense signal in response to the first current.

4. The method of claim 1 wherein receiving the first current representative of the input voltage to the power supply comprises coupling a resistance between the first terminal and an input of a primary winding of the power supply.

5. The method of claim 1 wherein activating the power supply in response to the deactivated under-voltage signal comprises enabling a switching waveform in response to the deactivated under-voltage signal, the switching waveform to control a power switch coupled to a primary winding of the power supply.

6. The method of claim 5 wherein enabling the switching waveform includes starting a new complete cycle of the switching waveform.

7. The method of claim 1 wherein deactivating the power supply in response to the activated under-voltage signal comprises disabling a switching waveform in response to the activated under-voltage signal, the switching waveform to control a power switch coupled to a primary winding of the power supply.

8. The method of claim 7 wherein disabling the switching waveform includes allowing to complete an existing cycle of the switching waveform.