Patent ID: 7508185

Claim:
A simple zero current switch circuit to control a conduction switch of a power-factor corrector in a zero current condition during ON/OFF switching operations, the power-factor corrector including an energy storing inductor to receive a commutated electric power and store energy and perform discharging, an output diode and an output capacitor electrically bridging the energy storing inductor and a power output end, and a conduction switch and a controller electrically bridging the energy storing inductor and the output diode, the zero current switch circuit comprising: a first coil set bridging the energy storing inductor and the output diode, the first coil set being connected to the conduction switch through a second coil set which is wound reversely according to a selected coil ratio relative to the first coil set, the first coil set having a leaking inductance to generate a back electromotive force to make the conduction switch in a zero current switching condition during ON/OFF operations; and an energy conversion circuit which is coupled with the power-factor corrector, the first coil set and the second coil set to form a power circuit, the energy conversion circuit including a plurality of diodes, capacitors, and a resistor; while the output diode generating a reverse recovery condition, the energy conversion circuit stores reverse energy according to the coil ratio of the second coil set relative to the first coil set and reclaims the energy to the output capacitor, discharge of said reverse energy being determined by said coil ratio to increase a speed of output diode discharge, an amount of current of the discharge is determined by the coil ratio so that said inductor is maintained in a saturated condition, thereby reverse recovery time of the output diode is shortened.