The invention relates to a high-efficiency and low-cost forward-flyback DC-DC (
direct current-
direct current) converter topology. The forward-flyback DC-
DC converter topology comprises a
transformer, a main switch tube, a clamp circuit, a first rectification switch tube, a second rectification switch tube, an LC
resonance circuit and an output
capacitor, wherein a primary winding of the
transformer is connected in series with the main switch tube between a first input end and a second input end; the clamp circuit consisting of a
clamp capacitor and a clamp switch tube which are connected in series is connected in parallel with the primary winding or the main switch tube; a secondary winding of the
transformer comprises a forward winding and a flyback winding; one end making the current flow into the primary winding is a dotted end of the primary winding; the
secondary side of the transformer is connected in a manner that: the dotted end of the forward winding is connected to the first output terminal through the first rectification switch tube, and the dotted end of the flyback winding is connected to the second output terminal through the second rectification switch tube; the LC
resonance circuit is connected to the first output terminal and the second output terminal and the unlike ends of the forward winding and the flyback winding so as to switch on or switch off the first rectification switch tube and the second rectification switch tube at zero current; and the output
capacitor is connected between the first output terminal and the second output terminal.