Flyback converter, control circuit and control method thereof

A control circuit for a flyback converter, the control circuit comprising:

• a) a detection circuit configured to generate a sampling voltage representing a drain-source voltage of a main switch in the flyback converter when the main switch is turned on, and to generate a detection signal in accordance with the sampling voltage;
• and
• b) an auxiliary switch control circuit configured to reduce a conduction time of an auxiliary switch in the flyback converter when the detection signal is active, and to increase the conduction time of the auxiliary switch when the detection signal is inactive, in order to achieve zero-voltage switching of the main switch.

A switching converter, comprising the control circuit of claim 1, and further comprising:

• a) a main power stage having the main switch, and being configured to control energy storage and transmission of a transformer;
• and
• b) a clamp circuit having the auxiliary switch, and being configured to provide a release path for releasing energy of leakage inductance of the transformer.