the present invention discloses a forward converter with secondary side post - regulation and zero voltage switching , where the primary side power loop may adopt a single or a dual transistor structure , driven by a primary side driving circuit with a constant duty ratio so that the voltage waveform across the secondary side power winding has a constant pulse width ; the secondary side power loop uses a controllable switch , a magnetic amplifier or an n channel metal oxide semiconductor field transistor , to blank the leading edge of the voltage waveform across the secondary side power winding , regulate the output voltage , and achieve zero voltage switching of primary side switch transistors .