A zero-current-switching PWM flyback converter with a simple auxiliary switch

A simple and effective approach of turning an isolated hard-switched conver ter design into a soft-switched one is presented, By adding an auxiliary wi nding, switch, and small capacitor to the conventional pulsewidth modulatio n (PWM)-isolated flyback converter, all switches and diodes are softly turn ed on and off. No extra active or passive voltage clamp circuit is needed t o suppress voltage stress on the switching devices that mere usually found in classical converters. A zero-current-switching (ZCS) PWM flyback convert er topology with multiple outputs is analyzed and examined. The proposal in herently utilizes the leakage inductance of the "flyback" transformer to ac hieve ZCS of all switching devices. A complete steady-state de analysis and the operating principle are described. The performance of an 80-W experime ntal converter prototype with dual-voltage outputs is included.