Patent ID: 8884588

Claim:
A battery warming circuit installed in a vehicle which is provided with an inverter circuit that converts direct current electrical power supplied from a secondary battery to 3-phase alternating current electrical power by switching a plurality of switching elements on and off, and a 3-phase alternating current motor that is driven by the inverter circuit, the battery warming circuit comprising: when one phase coil of three phase coils provided in the 3-phase alternating current motor is defined as a specific coil, one of the plurality of switching elements that is connected between one end of the specific coil and a positive electrode of the secondary battery is defined as a first switching element, and one of the plurality of switching elements that is connected between the other end of the specific coil and a negative electrode of the secondary battery is defined as a second switching element, a switch control unit which has a first terminal connected to a control terminal of the first switching element and a second terminal connected to a control terminal of the second switching element, and controls turning the first and second switching elements on and off by respectively outputting control signals to the control terminals of the first and second switching elements through the first and second terminals; an accumulation unit which has a third terminal connected to the other end of the specific coil, and accumulates back electromotive force generated in the specific coil by turning the second switching element on and off, with the first switching element being turned on; and a charging control unit which is provided between the positive electrode of the secondary battery and the accumulation unit, and supplies electrical power accumulated in the accumulation unit to the secondary battery.