A soft-switched, full-bridge pulse-width-modulated converter and its variations
provide zero-voltage-switching conditions for the turn-on of the bridge switches
over a wide range of input voltage and output load. The FB PWM converters of this
invention achieve ZVS with a substantially reduced duty cycle loss and circulating
current. The ZVS of the primary switches is achieved by employing an auxiliary
circuit having an inductor and transformer to store energy for ZVS turn-on of the
bridge switches.