A PTTM (Pulse Transition Time Modulation) power converter includes an input terminal supplied by a PWM (Pulse Width Modulated) signal, a PWM to PTTM converter, a controlled capacitance proportional to the pulse transition time, a pulse amplifier driving a power transformer, a gate drive transformer, and synchronous rectification means. The output voltage can be kept constant by varying the pulse transition time to cancel the effect of fluctuation of the operating voltage or variation of the load.