Motor drive unit and method of detecting malfunction of the motor drive unit

摘要

A DC motor (10) is connected to diagonal positions of a bridge circuit (31) having four sides including switching elements (SW1-SW4) and reflux diodes (Di1-Di4). At least one of two terminals is connected to a power line, and at least the other terminal is grounded. By performing pulse width modulation control of the switching elements, operation of the DC motor (10) is controlled. When the DC motor (10) is in operation, the sum of the terminal voltages of the DC motor (10) is equal to the power voltage. When the DC motor (10) is out of operation, the sum of the voltages is set to a predetermined voltage. If the sum of the voltages has deviated from the power voltage or the predetermined voltage by at least a predetermined value, the occurrence of a malfunction is judged.