Patent ID: 8629661

Claim:
A bidirectional DC-DC converter comprising: a first switching circuit configured to input electrical power from a first DC power supply, with which a first smoothing capacitor is connected in parallel, to an in-between terminal of DC terminals of the first switching circuit and to convert the electrical power to AC so as to supply the AC from an in-between terminal of AC terminals to a primary winding; a second switching circuit configured to input electrical power from a second DC power supply, with which a second smoothing capacitor is connected in parallel, to an in-between terminal of DC terminals of the second switching circuit and to convert the electrical power to AC so as to supply the AC from an in-between terminal of AC terminals to a secondary winding; a transformer which magnetically couples the primary winding to the secondary winding; and control means for controlling the first and second switching circuits so as to transfer electrical power between the first and second DC power supplies, wherein the first switching circuit includes: a first switching leg in which switching devices H 1 and H 2 are connected in series; and a second switching leg in which switching devices H 3 and H 4 are connected in series and which is connected in parallel with the first switching leg, wherein an in-between point of both ends of the first switching leg is the in-between terminal of the DC terminals while an interval between a point at which the switching devices H 1 and H 2 are connected in series and a point at which the switching devices H 3 and H 4 are connected in series is the in-between terminal of the AC terminals, wherein the second switching circuit is provided with a smoothing reactor to smooth electric, current flowed into the second DC power supply, said smoothing reactor being connected to between the secondary winding and the second smoothing capacitor, wherein the control means is provided with a mode A which keeps an ON state of the switching devices H 2 and H 3 upon supplying electrical power from the second DC power supply to the first DC power supply.