A dc-dc converter is disclosed comprising an active clamp topology, including an active clamp resonant transition system to provide substantially zero or reduced voltage for turn-on of the primary switch. The resonant transition system includes an inductor in series with the primary winding of the power transformer and a clamp diode that operate cooperatively to turn on the primary switch with reduced voltage. A second diode is included in series with a balancing resistor to discharge a snubber capacitor with improved efficiency. The addition of these circuit components provides low switching losses and low component stresses in the overall design.