METHOD AND APPARATUS FOR IMPLEMENTING A POWER CONVERTER INPUT TERMINAL VOLTAGE DISCHARGE CIRCUIT

• US 20110025278A1
• Filed: 07/31/2009
• Published: 02/03/2011
• Est. Priority Date: 07/31/2009
• Status: Active Grant

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Orr, Raymond Kenneth, Matthews, David Michael Hugh, Kung, David, Balakrishnan, Balu
• Granted Patent: US 8,115,457 B2
• Time in Patent Office: Days
• US Class Current: 320/166
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output
• CPC Class Codes: H02M 1/126 using passive filters
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 1/322 Means for rapidly discharging a capacitor of the converter for protecting electrical components or for preventing electrical shock
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters

Abstract

A circuit to discharge a capacitance between input terminals of a power system is disclosed. An example circuit includes a control circuit coupled to an input of a power system. The control circuit is coupled to detect whether an electrical energy source is coupled to an input of the power system. A switch is also included and is coupled to the control circuit and to the input of the power system. The control circuit is coupled to drive the switch in a first operating mode when the electrical energy source is coupled to the input of the power system. The control circuit is coupled to drive the switch in a second operating mode when the electrical energy source is uncoupled from the input of the power system. A capacitance coupled between input terminals of the input of the power system is discharged through the switch to a threshold voltage in less than a maximum period of time from when the electrical power source is uncoupled from the input terminals of the power system.

Claims

1. A circuit, comprising:

a control circuit coupled to an input of a power system, the control circuit coupled to detect whether an electrical energy source is coupled to an input of the power system; and

a switch coupled to the control circuit and coupled to the input of the power system, the control circuit coupled to drive the switch in a first operating mode when the electrical energy source is coupled to the input of the power system, the control circuit coupled to drive the switch in a second operating mode when the electrical energy source is uncoupled from the input of the power system, wherein a capacitance coupled between input terminals of the input of the power system is discharged through the switch to a threshold voltage in less than a maximum period of time from when the electrical power source is uncoupled from the input terminals of the power system.

2. The circuit of claim 1 wherein an output of the power system is coupled to provide electrical energy.

3. The circuit of claim 1 wherein the switch is coupled to provide a starting current for operation of the circuit during a start up phase of the circuit.

4. The circuit of claim 1 wherein an output of the power system is coupled to provide mechanical energy.

5. The circuit of claim 1 wherein an output of the power system is coupled to provide optical energy.

6. The circuit of claim 1 wherein the switch is driven to regulate a flow of energy from the input of the power system to an output of the power system in the first operating mode.

7. The circuit of claim 6 wherein the switch is driven into an off state to provide a standby condition.

8. The circuit of claim 6 wherein the switch is driven to perform a function of a power factor correction control circuit.

9. The circuit of claim 1 wherein the maximum period of time is unaffected by an amount of energy flow between input of the power system and an output of the power system prior to the electrical energy source being uncoupled from the input of the power system.

10. The circuit of claim 1 wherein the control circuit is coupled to drive the switch to have a high average impedance in the first operating mode.

11. The circuit of claim 1 wherein a current flow through the circuit is less than 30 μ

A in the first operating mode.

12. The circuit of claim 1 further comprising only two terminals coupled to external circuitry.

13. The circuit of claim 1 wherein the capacitance coupled between the input terminals of the input of the power system comprises one or more X capacitors.

14. The circuit of claim 1 wherein the control circuit and the switch are included in an integrated circuit.

15. The circuit of claim 1 wherein the switch is coupled across an output of a rectification circuit of the power system.

16. The circuit of claim 1 wherein the switch is a bidirectional switch.

17. The circuit of claim 1 wherein the switch comprises a first MOSFET coupled to a second MOSFET.

18. The circuit of claim 17 wherein the first and second MOSFETs are n-channel MOSFETs.

19. The circuit of claim 18 wherein a drain of the first MOSFET is coupled to one of the input terminals of the input of the power system, wherein a drain of the second MOSFET is coupled to an other one of the input terminals of the input of the power system.

20. The circuit of claim 19 wherein sources of the first and second MOSFETs are coupled to each other.

21. The circuit of claim 17 wherein one of the first and second MOSFETs are is turned on to discharge the capacitance to the threshold voltage in less than the maximum period of time when the electrical power source is uncoupled from the input terminals of the power system.

22. A circuit, comprising:

a control circuit coupled to an input of a power converter, the control circuit coupled to sense whether an electrical energy source is coupled across input terminals of the input of the power converter; and

a switch coupled to the control circuit and coupled to the input terminals of the input of the power converter, the control circuit coupled to drive the switch to have a high average impedance when the electrical energy source is coupled across the input terminals of the input of the power converter, the control circuit coupled to drive the switch to discharge a capacitance coupled between input terminals of the input of the power converter to below a threshold voltage in less than a maximum period of time from when the electrical power source is uncoupled from the input terminals of the input of the power converter.

23. The circuit of claim 22 wherein the capacitance coupled between the input terminals of the input of the power converter comprises one or more X capacitors.

24. The circuit of claim 22 wherein the control circuit and the switch are included in an integrated circuit.

25. The circuit of claim 22 wherein the switch is coupled across an output of a rectification circuit of the power converter.

26. The circuit of claim 22 wherein the switch comprises a current source.

27. The circuit of claim 22 wherein the electrical energy source is an ac voltage source.

28. A circuit, comprising:

a control circuit coupled to detect whether an electrical energy source is coupled to an input of a power converter; and

a switch coupled to the control circuit and coupled to the input of the power system, the control circuit coupled to drive the switch in a first operating mode to transfer energy from the input of the power converter to an output of the power converter when the electrical energy source is coupled to the input of the power converter, the control circuit coupled to drive the switch in a second operating mode when the electrical energy source is uncoupled from the input of the power converter, wherein a capacitance coupled between input terminals of the input of the power converter is discharged to a threshold voltage in less than a maximum period of time from when the electrical power source is uncoupled from the input terminals of the power converter.

29. The circuit of claim 28 wherein first operating mode includes a standby condition where the switch is driven to an off state.

30. The circuit of claim 28 wherein the power converter is one of a boost converter, a flyback converter, a forward converter, an LLC converter.

31. The circuit of claim 28 wherein the threshold voltage is a Safety Extra Low Voltage (SELV) level.

32. A circuit, comprising:

a control circuit coupled to an input of a power converter, the control circuit coupled to sense whether an ac voltage source is coupled across input terminals of the input of the power converter; and

a switch coupled to the control circuit and coupled to the input terminals of the input of the power converter, the control circuit coupled to drive the switch in a high average impedance when the ac voltage source is across the input terminals of the input of the power converter, the control circuit coupled to drive the switch to discharge a capacitance coupled between input terminals of the input of the power converter to below a threshold voltage in less than a maximum period of time from when the ac voltage source is uncoupled from the input terminals of the input of the power converter, wherein the control circuit and the switch are included in a integrated circuit.

33. The circuit of claim 32 wherein the integrated circuit is a single monolithic integrated circuit that includes the control circuit and the switch.

34. The circuit of claim 32 wherein the integrated circuit is a multi-die integrated circuit package that includes the control circuit and the switch.

35. The circuit of claim 32 wherein the switch comprises two MOSFETs, wherein one of the two MOSFETs is turned on to discharge the capacitance coupled between the input terminals of the input of the power converter to below the threshold voltage in less than the maximum period of time from when the ac voltage source is uncoupled from the input terminals of the input of the power converter.

36. The circuit of claim 32 wherein the switch is a bidirectional switch.

37. The circuit of claim 32 wherein the switch includes a current source.

38. The circuit of claim 32 wherein the control circuit includes a timer circuit that is coupled to be reset in response to the ac voltage source reversing in polarity when the ac voltage source is coupled across input terminals of the input of the power converter.

39. The circuit of claim 32 further comprising an internal supply rail that is coupled to be discharged to a level below a reset level in response to the ac voltage source reversing in polarity when the ac voltage source is coupled across input terminals of the input of the power converter.

40. The circuit of claim 32 wherein the integrated circuit includes only two external terminals.

41. The circuit of claim 32 wherein at least one of the two external terminals is coupled to one of the input terminals of the input of the power converter through a resistor.

42. The circuit of claim 32 wherein the integrated circuit includes four external terminals, wherein a first one of the four external terminals is a ground reference terminal, wherein a second one of the four external terminals is an internal supply rail terminal, and wherein the switch is coupled between the third and fourth external terminals.