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

• US 6,538,908 B2
• Filed: 06/11/2002
• Issued: 03/25/2003
• 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): Patel, Rajnikant B.
• Application Number:
  US10/167,557
• Publication Number:
  US 20020172055A1
• Time in Patent Office: 287 Days
• Field of Search: 363/16, 363/20, 363/19, 363/21.02, 363/89, 363/95, 363/15, 323/282, 323/283, 323/284, 323/285, 323/351, 323/299
• US Class Current: 363/95
• 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 power supply controller, comprising:

a power switch having first, second and third terminals, the first terminal to be coupled to a transformer of a power supply and the second terminal to be coupled to an input of the power supply;

a control circuit coupled to a control terminal of the power supply controller and the third terminal of the power switch, the control terminal coupled to an output of the power supply, the control circuit to generate a switching waveform to control the power switch; and

multi-function circuitry coupled between a multi-function terminal of the power supply controller and the control circuit, the switching waveform generated in response to the control terminal and the multi-function terminal.

2. The power supply controller of claim 1, wherein the multi-function circuitry comprises:

a negative current sensor coupled to the multi-function terminal, the negative current sensor to generate a negative current sense signal in response to the multi-function terminal if a voltage at the multi-function terminal is less than a first voltage, the negative current sensor isolated from the multi-function terminal if the voltage at the multi-function terminal is greater than the first voltage;

a positive current sensor coupled to the multi-function terminal, the positive current sensor to generate a positive current sense signal in response to the multi-function terminal if the voltage at the multi-function terminal is greater than a second voltage, the positive current sensor isolated from the multi-function terminal if the voltage at the multi-function terminal is less than the second voltage, wherein the second voltage is greater than the first voltage, the switching waveform generated in response to the negative current sense signal and the positive current sense signal.

3. The power supply controller of claim 1 wherein the multi-function circuitry comprises on/off circuitry coupled to the control circuit and responsive to the multi-function terminal, the on/off circuitry to control the control circuit to start and to stop the switching waveform in response to the multi-function terminal.

4. The power supply controller of claim 1 wherein the multi-function circuitry comprises external current limit adjuster circuitry coupled to the control circuit and responsive to the multi-function terminal, the external current limit adjuster circuitry to control the control circuit to adjust a current limit of the power switch in response to the multi-function terminal.

5. The power supply controller of claim 1 wherein the multi-function circuitry comprises over-voltage comparator circuitry coupled to the control circuit and responsive to the multi-function terminal, the over-voltage comparator circuitry to control the control circuit to start and to stop the switching waveform in response to the multi-function terminal.

6. The power supply controller of claim 1 wherein the multi-function circuitry comprises maximum duty cycle adjuster circuitry coupled to the control circuit and responsive to the multi-function terminal, the maximum duty cycle adjuster circuitry to adjust the maximum duty cycle of the switching waveform in response to the multi-function terminal.

7. The power supply controller of claim 1, wherein a voltage at the multi-function terminal is substantially equal to a first constant voltage if there is a negative current flowing through the multi-function terminal.

8. The power supply controller of claim 1, wherein a voltage at the multi-function terminal is substantially equal to a second constant voltage if there is a positive current flowing through the multi-function terminal.

9. The power supply controller of claim 1 wherein the first, second and third terminals of the power switch are drain, source and gate terminals, respectively.

10. The power supply controller of claim 1 wherein the first terminal is to be coupled to a primary winding of the transformer.

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

generating a switching waveform to control a power switch of a power supply controller coupled to a primary winding of the power supply;

adjusting the switching waveform in response to a control terminal of the power supply controller coupled to an output of the power supply; and

adjusting the switching waveform in response to a signal at a multi-function terminal of the power supply controller.

12. The method of claim 11 wherein adjusting the switching waveform in response to the signal at the multi-function terminal comprises generating a negative current sense signal if a current flowing through the multi-function terminal flows out of the power supply controller from the multi-function terminal.

13. The method of claim 11 further comprising adjusting a current limit of the power switch in response to the signal at the multi-function terminal.

14. The method of claim 11 wherein adjusting the switching waveform in response to the signal at the multi-function terminal comprises enabling and disabling the switching waveform in response to the signal at the multi-function terminal.

15. The method of claim 11 wherein adjusting the switching waveform in response to the signal at the multi-function terminal comprises generating a positive current sense signal if a current flowing through the multi-function terminal flows into the power supply controller through the multi-function terminal.

16. The method of claim 11 further wherein adjusting the switching waveform in response to the signal at the multi-function terminal comprises adjusting a maximum duty cycle of the switching waveform in response to the signal at the multi-function terminal.

17. The method of claim 11 further comprising identifying an under-voltage in the power supply in response to the signal at the multi-function terminal.

18. The method of claim 11 further comprising identifying an over-voltage in the power supply in response to the signal at the multi-function terminal.

19. A power supply controller, comprising:

a power switch coupled between a transformer of a power supply and an input terminal of the power supply;

a control circuit coupled to the power switch and a control terminal of the power supply controller, the control terminal coupled to an output of the power supply, the control circuit to generate a switching waveform to control the power switch; and

multi-function circuitry providing a plurality of functions coupled between a multi-function terminal of the power supply controller and the control circuit, the control circuit adapted to generate the switching waveform generated in response to the control terminal and the multi-function circuitry.

20. The power supply controller of claim 19 wherein the plurality of functions provided by the multi-function circuitry include at least two or more of current limit adjustment, under-voltage detection, over-voltage detection, maximum duty cycle adjustment and on/off control circuitry at the same time in the power supply controller.

21. The power supply controller of claim 20 wherein the current limit adjustment, under-voltage detection, over-voltage detection, maximum duty cycle adjustment and on/off control circuitry are adapted to be responsive to a signal at the multi-functional terminal.

22. The power supply controller of claim 20 wherein at least a portion of the plurality of functions provided by the multi-function circuitry are adapted to be implemented during startup operation of the power supply.

23. The power supply controller of claim 20 wherein at least a portion of the plurality of functions provided by the multi-function circuitry are adapted to be implemented during normal operation of the power supply.

24. The power supply controller of claim 20 wherein at least a portion of the plurality of functions provided by the multi-function circuitry are adapted to be implemented during fault conditions in of the power supply.

25. The power supply controller of claim 20 wherein at least a portion of the plurality of functions provided by the multi-function circuitry are adapted to be implemented during standby operation of the power supply.

26. A power supply controller circuit, comprising:

a multi-function circuit coupled to receive a signal at a multi-function terminal for adjusting a current limit of a power switch, the multi-function circuit to generate a current limit adjustment signal in response to the signal; and

a control circuit coupled to receive the current limit adjustment signal, the control circuit coupled to adjust the current limit of a current through the power switch in response to the current limit adjustment signal.

27. The power supply controller circuit of claim 26 wherein the control circuit is further coupled to an output of a power supply through a control terminal of the power supply controller circuit, the control circuit adapted to control a switching of the power switch in response to the output of the power supply.

28. The power supply controller circuit of claim 26 wherein the control circuit includes a control terminal adapted to provide a supply voltage for the power supply controller.

29. The power supply controller circuit of claim 28 wherein an optocoupler is coupled to an output of a power supply, wherein an output transistor of the optocoupler is coupled between the control terminal and the multi-function terminal such that the current limit of the current through the power switch is adjusted in a closed loop to regulate the output of the power supply.

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

sensing a signal at a multi-function terminal of a power supply controller;

controlling a current flowing through a primary winding of the power supply with a power switch coupled to the primary winding; and

adjusting a current limit of the current flowing through the primary winding in response to the signal at the multi-function terminal.

31. The method of claim 30 further comprising:

receiving a feedback signal from an output of the power supply at a control terminal; and

regulating the output of the power supply in response to the feedback signal and the current limit of the current flowing through the primary winding.

32. The method of claim 30 wherein adjusting the current limit of the current flowing through the primary winding comprises increasing the current limit of the current flowing through the primary winding in response to sensing an increase in the signal at the multi-function terminal of a power supply controller.

33. The method of claim 30 wherein adjusting the current limit of the current flowing through the primary winding comprises decreasing the current limit of the current flowing through the primary winding in response to sensing a decrease in the signal at the multi-function terminal of a power supply controller.

34. The method of claim 30 wherein controlling the current flowing through the primary winding of the power supply comprises:

switching the power switch in response to a switching waveform; and

adjusting the switching waveform in response to the signal at the multi-function terminal of a power supply controller.