Patent ID: 7615976

Claim:
A switching circuit for power converters, comprising: a voltage-clipping device, having an input terminal directly coupled to an input voltage, and a control terminal directly coupled to a gate terminal of the voltage-clipping device; a first transistor, having a drain terminal directly coupled to an output terminal of said voltage-clipping device, wherein a source terminal of said first transistor provides a supply voltage to a control circuit of the power converter; a second transistor, having a drain terminal directly coupled to a gate terminal of said first transistor and a control terminal of said voltage-clipping device; a gate terminal of said second transistor receives a control signal; and a resistive device, connected from said control terminal of said voltage-clipping device to an output terminal of said voltage-clipping device, wherein said resistive device provides a bias voltage to turn on said first transistor and said voltage-clipping device when said second transistor is turned off; said control signal turns on said second transistor for switching off said first transistor and providing a negative bias for said voltage-clipping device, wherein said voltage-clipping device clamps a maximum voltage for said first transistor.