A DC-DC power converter including: input terminals for receiving an input voltage； a pulse wave generator for generating a pulse wave； a transformer having a primary winding and a secondary winding and a magnetizing inductance； a DC blocking capacitor； a rectifier； a filter capacitor； at least one resonant inductor connected in series with the transformer； a resonant capacitor connected to the rectifier； output terminals； and a control unit for controlling operation of the pulse wave generator such when the duty cycle of the pulse wave voltage varies, high efficiency is maintained.
