Systems and methods of operation for power converters having series-parallel mode active clamps

A method of operating a power conversion circuit comprising a flyback converter including a transformer having a primary winding, an auxiliary primary winding, and a secondary winding, and a first switch configured to be switched to alternately store energy in the transformer and transfer energy from the transformer to an output load and an active resonant clamp coupled to the auxiliary primary winding, the active resonant clamp including a second switch, at least two capacitors, and a plurality of diodes configured to recycle leakage energy from the transformer, the method comprising:

• switching the first switch on, so as to store energy in a primary winding of the transformer;
• switching the first switch off, so as to charge the at least two capacitors in series via the auxiliary primary winding, thereby recovering leakage energy from the transformer;
• discharging the at least two capacitors in parallel to return the recovered leakage energy to the transformer.

A power conversion apparatus comprising:

• a flyback converter, the flyback converter including a transformer having a primary winding, an auxiliary primary winding, and a secondary winding, and a first switch configured to be switched to alternately store energy in the transformer and transfer energy from the transformer to an output load;
• and
• an active resonant clamp coupled to at least one of the primary winding and the auxiliary primary winding, the active resonant clamp including a second switch, at least two capacitors configured to charge in series and discharge in parallel, and a plurality of diodes, the active resonant clamp being configured to recover leakage energy from the transformer.