Method and apparatus for implementing a power converter input terminal voltage discharge circuit

• US 8,624,562 B2
• Filed: 01/06/2012
• Issued: 01/07/2014
• Est. Priority Date: 07/31/2009
• Status: Expired due to Fees

• Current Assignee: Power Integrations Incorporated
• Original Assignee: Power Integrations Incorporated
• Inventors: Balakrishnan, Balu, Kung, David, Orr, Raymond Kenneth, Matthews, David Michael Hugh
• Primary Examiner(s): WILLIAMS, ARUN C
• Application Number:
  US13/345,257
• Publication Number:
  US 20120105018A1
• Time in Patent Office: 732 Days
• Field of Search: 320/166
• 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 switch is coupled to a control circuit and to an input of a power converter. The control circuit is coupled to drive the switch in a first operating mode to transfer energy from the input to an output of the power converter when an electrical energy source is coupled to the input of the power converter. The control circuit is coupled to drive the switch in a second operating mode when the electrical energy source is uncoupled from the input. A capacitance is coupled between input terminals of the input of the power converter and is discharged to a threshold voltage in less than a maximum period of time from when the electrical energy source is uncoupled from the input terminals. The control circuit is coupled to drive the switch to have a high average impedance in the first operating mode.

Claims

1. 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 converter, 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 energy source is uncoupled from the input terminals of the power converter, wherein the control circuit is coupled to drive the switch to have a high average impedance in the first operating mode.

2. The circuit of claim 1 wherein first operating mode includes a standby condition where the switch is driven to an off state.

3. The circuit of claim 1 wherein the power converter is one of a boost converter, a flyback converter, a forward converter, an LLC converter.

4. The circuit of claim 1 wherein the threshold voltage is a Safety Extra Low Voltage (SELV) level.

5. 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.

6. The circuit of claim 1 wherein the output of the power converter is coupled to provide electrical energy.

7. The circuit of claim 1 wherein the output of the power converter is coupled to provide mechanical energy.

8. The circuit of claim 1 wherein the output of the power converter is coupled to provide optical energy.

9. The circuit of claim 1 wherein the switch is driven to perform a function of a power factor correction control circuit in the first operating mode.

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

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 converter 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 converter.