Patent ID: 7839128

Claim:
A bidirectional power supply device comprising: a bidirectional DC-DC converter including: a first positive terminal, a first negative terminal, a second positive terminal, and a second negative terminal for supplying and receiving power; a capacitor connected in parallel between the first positive terminal and the first negative terminal; a first switch and a second switch connected in series and alternately and repeatedly turned ON/OFF; an inductance element having one end connected to a node of the first switch and the second switch; a switching signal generation circuit for generating an ON/OFF signal of the first switch and the second switch; and a control circuit for controlling the switching signal generation circuit, wherein the bidirectional DC-DC converter is connected such that the longer an ON time of the first switch becomes, the higher a voltage of the second positive terminal and the second negative terminal becomes; a third switch having one end connected to the first positive terminal or the first negative terminal, and being ON/OFF controlled by the control circuit; a first power supply connected in series to the third switch, the series circuit being connected between the first positive terminal and the first negative terminal; and a second power supply connected between the second positive terminal and the second negative terminal; wherein the control circuit turns OFF the third switch and operates the switching signal generation circuit so that the ON time of the first switch becomes a maximum when stopping supply of power from the first positive terminal and the first negative terminal to the second positive terminal and the second negative terminal; and the control circuit makes the switching signal generation circuit started so that the ON time of the first switch becomes a maximum with the third switch turned OFF when supplying power from the second positive terminal and the second negative terminal to the first positive terminal and the first negative terminal.