Patent ID: 8836258

Claim:
A motor driving device for driving a motor, comprising: an inverter device; a current detector that detects electric current flowing through a coil of said motor; and a controller that controls said inverter device, wherein said inverter device is a three-phase inverter in which six a plurality of arms that can conduct and block current are connected to one another through a bridge connection, wherein three arms of said six arms are connected to a high-voltage side or a low-voltage side of DC voltage supplied to said inverter device, said three arms include: a plurality of switching elements having parasitic diodes and being connected in series with each other, and a reverse current diode connected in parallel with said plurality of switching elements, said switching elements are connected to each other so that polarity of a parasitic diode of one switching element is opposite to polarity of a parasitic diode of another switching element adjacent thereto, among said plurality of switching elements, a switching element having said parasitic diode with reversed polarity relative to the polarity of said reverse current diode has a short reverse recovery time of said parasitic diode as compared with that of other switching elements, the other three arms of said six arms include one second switching element and a second reverse current diode connected in parallel with said second switching element, and said controller drives, based on current detected by said current detector, said motor by PWM control of said inverter device with overlaid two-phase modulation, in which a switching element of an arm connected to said high-voltage side of a phase that does not perform a switching operation among three phases is kept at an on state or with underlaid two-phase modulation, in which a switching element of an arm connected to said low-voltage side of a phase that does not perform a switching operation among three phases is kept at an on state in a period of an inverter rotation angle having a same combination of a principal voltage vector that generates a voltage command vector.