Motor drive apparatus

A motor drive apparatus for a motor of a plurality of phases, the motor drive apparatus comprising:

• a drive circuit, which includes a plurality of switching elements forming a high-side arm and a low-side arm of a bridge circuit and drives the motor by converting electric power of a DC power source;
• a power supply on/off circuit, which conducts and interrupts electric connection between the DC power source and the drive circuit;
• a drive control circuit, which controls the plurality of switching elements to turn on and off when the drive circuit drives the motor, and turns off the plurality of switching elements when the electric connection is interrupted by the power supply on/off circuit;
• a back EMF detection circuit, which detects whether a back EMF is generated with respect to each phase;
• and
• a protection control circuit, which turns on at least the switching element forming the low-side arm of a predetermined phase, when the back EMF detection circuit detects the back EMF in any one of the phases under a state of interruption of the electric connection by the power supply on/off circuit, the predetermined phase corresponding to the phase in which the back EMF is detected.