Utilization of an active-clamp circuit to achieve soft switching in flyback converters

Flyback derived topologies are attractive because of their relative simplicity when compared with other topologies used in low power applications. Incorporation of active-clamp circuitry into the flyback topology serves to recycle transformer leakage energy while minimizing switch voltage stress. The addition of the active-clamp circuit also provides a mechanism for achieving zero-voltage-switching (ZVS) of both the main and auxiliary-switches. ZVS also limits the turn-off di/dt of the output rectifier, reducing rectifier switching losses and switching noise due to diode reverse recovery