Patent ID: 7570501

Claim:
A DC to DC converter interposed between a first voltage system and a second voltage system for transferring power between the first and second voltage system, wherein said first voltage system has a DC power supply and a power supply switch connected to each other in series, said DC to DC converter comprising: a smoothing capacitor coupled between a positive terminal and a negative terminal of the DC power supply of the first voltage system, and to the series connected DC power supply and the power supply switch in parallel; a magnetic circuit having a first primary winding, a second primary winding, a third primary winding, a fourth primary winding, a first secondary winding, and a second secondary winding, the first and second primary windings being magnetically coupled to the first secondary winding, the third and fourth primary windings being magnetically coupled to the second secondary winding, the first and third primary windings being coupled in series to form a first coil member, the second and fourth primary windings being coupled in series to form a second coil member, one end of the first coil member being coupled to the positive terminal of the DC power supply of the first voltage system, the first and second secondary windings being coupled to the second voltage system; a capacitor coupled between the negative terminal of the DC power supply of the first voltage system and one end of the second coil member; a switching element coupled between the negative terminal of the DC power supply of the first voltage system and a connecting point at which the other end of the first coil member and the other end of the second coil member are connected to each other; and a controller coupled to the power supply switch and configured to, when the power supply switch is off state, transfer power from the second voltage system to the first voltage system through the magnetic circuit to precharge voltage based on the transferred power to the smoothing capacitor and to turn on the power switch after the precharge is completed.