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

• US 6,304,462 B1
• Filed: 10/26/2000
• Issued: 10/16/2001
• 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, Jessica
• Application Number:
  US09/698,926
• Time in Patent Office: 355 Days
• Field of Search: 363/15, 363/16, 363/20, 363/21.01, 363/21.02, 363/21.04, 363/21.09, 363/21.1, 363/21.12, 363/21.17, 363/21.18, 363/56.01, 363/56.11, 363/97
• 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 power supply controller, comprising:

a power switch having a drain terminal, a source terminal and a gate, the drain terminal coupled to a primary winding of a power supply and the source terminal coupled to ground;

a control circuit coupled to a control terminal, the drain terminal and the gate 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;

multi-function circuitry coupled between a multi-function terminal and the control circuit, the switching waveform generated in response to the drain terminal, 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 2 wherein the multi-function circuitry further comprises on/off circuitry coupled to receive the negative current sense signal and coupled to the control circuit, 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 2 wherein the multi-function circuitry further comprises external current limit adjuster circuitry coupled to receive the negative current sense signal and coupled to the control circuit, the external current limit adjuster circuitry control the control circuit to adjust a current limit of the power switch in response to a current received at the multi-function terminal.

5. The power supply controller of claim 2 wherein the multi-function circuitry further comprises under-voltage comparator circuitry coupled to receive the positive current sense signal and coupled to the control circuit, the under-voltage comparator circuitry to control the control circuit to start and to stop the switching waveform in response to a current received at the multi-function terminal.

6. The power supply controller of claim 2 wherein the multi-function circuitry further comprises over-voltage comparator circuitry coupled to receive the positive current sense signal and coupled to the control circuit, the over-voltage comparator circuitry to control the control circuit to start and to stop the switching waveform in response to a current received at the multi-function terminal.

7. The power supply controller of claim 2 wherein the multi-function circuitry further comprises maximum duty cycle adjuster circuitry coupled to receive the positive current sense signal and coupled to the control circuit, the maximum duty cycle adjuster circuitry to adjust the maximum duty cycle of the switching waveform in response to a current received at 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 first constant voltage if there is a negative current flowing through the multi-function terminal.

9. 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.

10. 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 drain terminal of the power supply controller coupled to the primary winding, a voltage at the drain terminal indicating a current flowing through the power switch;

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 current flowing through a multi-function terminal of the power supply controller.

11. The method of claim 10 wherein adjusting the switching waveform in response to the current flowing through the multi-function terminal comprises generating a negative current sense signal if the current flowing through the multi-function terminal flows out of the power supply controller from the multi-function terminal.

12. The method of claim 11 further comprising coupling the multi-function terminal to ground through a resistance.

13. The method of claim 11 further comprising switchably coupling the multi-function terminal to ground.

14. The method of claim 10 wherein adjusting the switching waveform in response to the current flowing through the multi-function terminal comprises generating a positive current sense signal if the current flowing through the multi-function terminal flows into the power supply controller through the multi-function terminal.

15. The method of claim 14 further comprising starting and stopping the switching waveform in response to the positive current sense signal.

16. The method of claim 14 further comprising reducing a maximum duty cycle of the switching waveform in response to the positive current sense signal.

17. The method of claim 14 further comprising coupling the multi-function terminal to an input voltage of the power supply through a resistance.

18. The method of claim 14 further comprising switchably coupling the multi-function terminal to a first potential.

19. The method of claim 11 further comprising starting and stopping the switching waveform in response to the negative current sense signal.

20. The method of claim 11 further comprising controlling the switching waveform to limit the current flowing through the power switch in response to the negative current sense signal.

21. The power supply controller, comprising:

a power switch coupled between a drain terminal and a source terminal, the drain terminal to be coupled to a primary winding of a power supply;

a control circuit coupled to the power switch, the drain terminal and a control terminal, the control terminal to be coupled to an output of the power supply;

a negative current sensor coupled to a multi-function terminal;

a positive current sensor coupled to the multi-function terminal;

a on/off circuit coupled between the negative current sensor and the control circuit;

an external current limit adjuster coupled between the negative current sensor and the control circuit;

an under-voltage comparator coupled between the positive current sensor and the control circuit;

an over-voltage comparator coupled between the positive current sensor and the control circuit; and

a maximum duty cycle adjuster coupled between the positive current sensor and the control circuit.

22. The power supply controller of claim 21 further comprising enable/disable logic coupled to an output of the under-voltage comparator, to an output of the over-voltage comparator, to an output of the on/off circuit and to an input of the control circuit.

23. The power supply controller of claim 22 wherein the enable/disable logic comprises:

a first NOR gate having a first input coupled to the under-voltage comparator and having an inverted second input coupled to the on/off circuit; and

a second NOR gate having a first input coupled to the over-voltage comparator and having a second input coupled to an output of the first NOR gate.

24. The power supply controller of claim 22 wherein the control circuit comprises:

a second resistor coupled to the control terminal;

a sixteenth transistor having a source coupled to the second resistor and a drain coupled to the maximum duty cycle adjuster;

a first comparator having a first input coupled to the source of the sixteenth transistor and the second resistor, the first comparator having a second input coupled to a third voltage;

a third resistor coupled to the drain of the sixteenth transistor;

a fourth resistor coupled to the drain of the sixteenth transistor and the third resistor;

a first capacitor coupled to the fourth resistor;

an oscillator having an enable/disable input and first, second and third switching waveform outputs, the enable/disable input of the oscillator coupled to the enable/disable logic;

a fifth resistor coupled to the drain terminal;

a sixth resistor coupled to the fifth resistor;

a second comparator having a first input coupled to the fifth and sixth resistors and a second input coupled to the external current limit adjuster;

a third comparator having a first input coupled to the third switching waveform output and having a second input coupled to the first capacitor and the fourth resistor;

a leading edge blanking delay circuit coupled to the power switch;

a first AND gate having a first input coupled to the leading edge blanking delay circuit and having a second input coupled to an output of the second comparator;

a first OR gate having a first input coupled to an output of the first AND gate and having a second input coupled to an output of the third comparator;

a first latch having a set input coupled to the second switching waveform output and having a reset input coupled to an output of the first OR gate; and

a second AND gate having a first input coupled to the first switching waveform output and having a second input coupled to an output of the first latch, the second AND gate having an output coupled to the power switch.

25. The power supply controller of claim 24 wherein the oscillator begins generating new complete cycles of first, second and third switching waveforms at the first, second and third switching waveform outputs, respectively, in response to an enable/disable signal received at the enable/disable input.

26. The power supply controller of claim 24 wherein the oscillator allows to complete existing cycles of first, second and third switching waveforms at the first, second and third switching waveform outputs, respectively, before stopping the first, second and third switching waveforms in response to an enable/disable signal received at the enable/disable input.

27. The power supply controller of claim 21 wherein the power switch comprises a power transistor coupled between the drain terminal and the source terminal, the power transistor having a gate coupled to the control circuit.

28. The power supply controller of claim 21 wherein the negative current sensor comprises:

a first current source coupled to the control terminal;

a first transistor having a source coupled to the first current source and a gate coupled to a drain of the first transistor;

a second transistor having a source coupled to the source of the first transistor and a gate coupled to the gate of the first transistor;

a third transistor having a drain coupled to the drain and the gate of the first transistor and to the gate of the second transistor, the third transistor having a source coupled to the multi-function terminal and a gate coupled to a first voltage; and

a fourth transistor having a drain and gate coupled to the drain of the second transistor.

29. The power supply controller of claim 28 wherein the on/off circuit comprises:

a second current source coupled to the control terminal; and

a fifth transistor having a gate coupled to the gate and drain of the fourth transistor and a drain coupled to the second current source.

30. The power supply controller of claim 28 wherein the external current limit adjuster comprises:

a third current source coupled to the control terminal;

a fourth current source coupled to the control terminal;

a sixth transistor having a gate coupled to the gate and drain of the fourth transistor and a drain coupled to the third current source;

a seventh transistor having a gate and drain coupled to the drain of the sixth transistor;

an eighth transistor having a gate coupled to the gate and drain of the seventh transistor, the eighth transistor having a drain coupled to the fourth current source; and

a first resistor coupled to the fourth current source and the drain of the eighth transistor.

31. The power supply controller of claim 21 wherein the positive current sensor comprises:

a ninth transistor having a source coupled to the multi-function terminal and a gate coupled to a second voltage;

a tenth transistor having a gate and drain coupled to a drain of the ninth transistor;

an eleventh transistor having a gate coupled to the gate and drain of the tenth transistor;

a twelfth transistor having a source coupled to the control terminal and a gate and drain coupled to a drain of the eleventh transistor; and

a fifth current source coupled to a source of the tenth transistor and coupled to a source of the eleventh transistor.

32. The power supply controller of claim 31 wherein the under-voltage comparator comprises:

a thirteenth transistor having a source coupled to the control terminal and having a gate coupled to the gate and drain of the twelfth transistor; and

a sixth current source coupled to a drain of the thirteenth transistor.

33. The power supply controller of claim 31 wherein the over-voltage comparator comprises:

the fourteenth transistor having a source coupled to the control terminal and having a gate coupled to the gate and drain of the twelfth transistor; and

a seventh current source coupled to a drain of the fourteenth transistor.

34. The power supply controller of claim 31 wherein the maximum duty cycle adjuster comprises:

a fifteenth transistor having a source coupled to the control terminal and having a gate coupled to the gate and drain of the twelfth transistor;

a first diode coupled to a drain of the fifteenth transistor; and

an eighth current source coupled to the drain of the fifteenth transistor.