Power converter and controlling method thereof and controller

A method of controlling a power converter, wherein the power converter comprises a switch circuit having a first switch and a second switch, a transformer having a primary side winding, a magnetic inductor, and a secondary side winding, a resonant circuit coupled between the primary side winding and the switch circuit, and an auxiliary circuit having an auxiliary winding, an auxiliary switch, and an auxiliary capacitor, wherein the auxiliary circuit and the primary side winding are disposed on a same side of the transformer, wherein the method comprises:

• switching on the second switch and charging the auxiliary capacitor up to a first interval by discharging the magnetic inductor;
• switching off the second switch and switching on the auxiliary switch to make the auxiliary capacitor charge the magnetic inductor to generate an exciting current during a second interval after the first interval;
• and
• switching off the auxiliary switch and switching on a parasitic diode of the first switch by the exciting current flowing through the first switch during a third interval after the second interval.

A controller configured to control a power converter, wherein the power converter comprises a switch circuit having a first switch and a second switch, a transformer having a primary side winding, a magnetic inductor, and a secondary side winding, a resonant circuit coupled between the primary side winding and the switch circuit, and an auxiliary circuit having an auxiliary winding, an auxiliary switch, and an auxiliary capacitor, wherein the auxiliary circuit and the primary side winding are disposed on a same side of the transformer,

• wherein the controller is configured to:
• switch on the second switch and charge the auxiliary capacitor up to a first interval by discharging the magnetic inductor;
• switch off the second switch and switch on the auxiliary switch to make the auxiliary capacitor charge the magnetic inductor to generate an exciting current during a second interval after the first interval;
• and
• switch off the auxiliary switch and switch on the first switch after switching on a parasitic diode of the first switch by the exciting current flowing through the first switch during a third interval after the second interval.