Method for operating a power converter, power converter circuit, controller and computer program

A power converter circuit, comprising:

• an asymmetrical half bridge flyback converter circuit comprising a half bridge with a high side switch and a low side switch and a transformer with a primary winding and a secondary winding, wherein the primary winding is connected to the half bridge and the secondary winding is connected to an output of the power converter circuit,
• a clamping circuit coupled via an auxiliary winding of the transformer to the primary winding, wherein the clamping circuit comprises a third switch and a second diode connected in series, and
• a controller configured to switch on and switch off the high and low side switches and the third switch and configured to operate the power converter circuit in a critical conduction mode or in a discontinuous conduction mode,
• wherein during a third time interval of the discontinuous conduction mode, the controller switches on the third switch, wherein the high and low side switches are switched off during the third time interval and wherein by switching on the third switch the clamping circuit prevents a free oscillation between a magnetizing inductance of the transformer and parasitic capacitances of the asymmetrical half bridge flyback converter circuit.

A controller for a power converter circuit, wherein the power converter circuit comprises:

• an asymmetrical half bridge flyback converter circuit comprising a half bridge with a high side switch and a low side switch and a transformer with a primary winding and a secondary winding, wherein the primary winding is connected to the half bridge and the secondary winding is connected to an output of the power converter circuit, and
• a clamping circuit coupled via an auxiliary winding of the transformer to the primary winding, wherein the clamping circuit comprises a third switch and a second diode connected in series,
• wherein the controller is configured to switch on and switch off the high and low side switches and the third switch,
• wherein the controller is configured to operate the power converter circuit in a critical conduction mode or in a discontinuous conduction mode, and
• wherein during a third time interval of the discontinuous conduction mode, the controller switches on the third switch, wherein the high and low side switches are switched off during the third time interval and wherein by switching on the third switch the clamping circuit prevents a free oscillation between a magnetizing inductance of the transformer and parasitic capacitances of the asymmetrical half bridge flyback converter circuit.