US Patent 12009753 Half-bridge flyback power converter and control method thereof

A half-bridge flyback power converter: a first transistor, a second transistor and a third transistor which form a half-bridge circuit. The first transistor is turned on for generating a negative circulated current for achieving zero voltage switching of the second transistor. The second transistor is turned on for magnetizing a transformer. The third transistor is turned on during a demagnetized time period to generate an output voltage. The physical size of the first transistor is smaller than physical size of the third transistor.