An AC/DC power converter which charges a secondary battery from an AC power supply and also converts power from the secondary battery to the AC voltage is provided. A capacitor C is connected to DC terminals of the four reverse-conductive type semiconductor switches in a single-phase bridge structure, and a secondary battery is connected via a DC inductance to the semiconductor switches. The semiconductor switches are connected via an AC inductance L with an AC power supply and opposing pairs of the semiconductor switches are alternately turned ON/OFF in synchronization with the phase of the supply voltage. When an AC power supply with a frequency which is lower than the resonance frequency of the LC is connected, the switching will be carried out in a zero-voltage-zero-current condition and AC/DC reversible power conversion is possible just through the control of the gate phase of the switches.