Motor driving circuit, motor device, and electric vehicle

A motor driving circuit, comprising:

• a supply line connected to a direct-current power source;
• an inverter of which an input side is connected to the supply line and of which an output side is connected to a motor, the inverter converting direct-current electric power fed from the supply line into alternating-current electric power and feeding the alternating-current electric power to the motor;
• a power switch inserted in the supply line for switching the supply line between a conducting state and a cut-off state;
• a voltage detector for detecting a voltage between the direct-current power source and the power switch;
• and
• an insulation resistance detector for
• first performing a first detection operation to detect, based on a result of detection by the voltage detector with the power switch in the cut-off state, an insulation resistance on a preceding-stage side of the power switch and
• subsequently performing a second detection operation to detect, based on a result of detection by the voltage detector with the power switch in the conducting state, an insulation resistance on a succeeding-stage side of the power switch.