Patent ID: 8441811

Claim:
An AC-DC converter, comprising: a rectifier for rectifying an input AC voltage; a first filter circuit connected to the rectifier, capable of generating an intermediate DC voltage; a quasi-resonance circuit connected to the first filter circuit; a main switch circuit connected to the quasi-resonance circuit; a switching control circuit connected to a first current-conducting terminal of the main switch circuit and a control terminal of the main switch circuit for outputting a switching control signal to turn on or off the main switch circuit; and an OFF time clamping circuit connected to the first current-conducting terminal of the main switch circuit and the control terminal of the main switch circuit for outputting a triggering signal when the main switch circuit is switched from ON state or OFF state, thereby controlling the main switch circuit to turn on or off; wherein the OFF time clamping circuit further includes a first switch circuit having a first current-conducting terminal for receiving a supply DC voltage, a control terminal connected to the control terminal of the main switch circuit for receiving the switching control signal, and a second current-conducting terminal connected to an output end of the OFF time clamping circuit for transferring energy of supply DC voltage to the output end of the OFF time clamping circuit for boosting a level of the triggering signal to be higher than a specific voltage when the first switch circuit is turned on.