–We have already proposed the new control method for the bidirectional isolated dc/dc converter. This method is that the output terminals of two single phase bridge inverter A and B are connected through an isolated transformer, and the pulse width of the inverter of higher d.c. voltage is narrowed to make equal the fundamental a.c. voltage of both inverters. For example, to make the a.c. output voltage of both inverters same, the pulse width of the INV-A is 180 degree and the pulse width of INV-B is narrowed to 60 degree. In this paper, the control method that the efficiency improvement of dc/dc converter by a current power-factor control is proposed. In this control system, the function of phase difference and the pulse width control are used. Since sine wave current will be brought near by a straight with a low d.c.voltage, the zero-electric-current switching can be realized.