AC active clamp for isolated power factor corrector and method of operating the same

For use with a power factor corrector having a primary switching circuit coupled to a primary winding of an isolation transformer and a rectifier coupled to a secondary winding of said isolation transformer, said primary switching circuit having first and second power switches configured to receive unrectified AC power, a method of actively clamping energy of said power factor corrector, comprising:

• mitigating adverse effects of a reverse recovery phenomenon associated with said rectifier with an AC active clamp having:
• a switching circuit including first and second clamping switches series coupled in opposition, and
• a capacitor coupled to said switching circuit, said switching circuit and said capacitor coupled across at least a portion of said primary winding;
• and
• effecting, with said AC active clamp, substantially zero voltage switching of said first and second power switches of said primary switching circuit.

An isolated power factor corrector having an input and adapted to provide a DC output voltage at an output thereof, comprising:

• an isolation transformer having a primary winding and a secondary winding;
• a primary switching circuit, interposed between said input and said primary winding, including first and second power switches configured to receive unrectified AC power;
• a rectifier, interposed between said secondary winding and said output, configured to rectify a waveform from said isolation transformer to develop said DC output voltage;
• and
• an AC active clamp, coupled to said primary switching circuit, comprising:
• a switching circuit having first and second clamping switches series coupled in opposition;
• and
• a capacitor coupled to said switching circuit, said switching circuit and said capacitor coupled across at least a portion of said primary winding and configured to mitigate adverse effects of a reverse recovery phenomenon associated with said rectifier and to effect substantially zero voltage switching of said first and second power switches of said primary switching circuit.