Protection circuit of flyback converter and control method

A protection circuit of a flyback converter, wherein the flyback converter comprises a transformer, a first switch transistor and a second switch transistor located at a primary edge of the transformer and connected between an input terminal of the flyback converter and a reference ground, and a first capacitor and a first inductor forming a resonance circuit when the second switch transistor is turned on, and the protection circuit comprises:

• an active discharge module, for providing a discharge path between a first current terminal and a second current terminal of the second switch transistor, and controlling turning-on and turning-off of the discharge path according to a discharge enabling signal, wherein the discharge path is connected to the second switch transistor in parallel,
• wherein in a normal work state of the flyback converter, the discharge path in the active discharge module is disconnected, and the resonance circuit works;
• before the flyback converter is restarted, the discharge path in the active discharge module is turned on for a predetermined time period to release charges stored in the resonance circuit, and reduces a resonance current after the flyback converter is restarted to a safe work current of the second switch transistor.