MOTOR DRIVER AND DRIVE METHOD

PROBLEM TO BE SOLVED: To improve the operation efficiency of a motor. SOLUTION: In a brushless DC motor driver, which drives a brushless DC motor, by a controller 32 controlling the phase difference between the current and the voltage of the AC power supplied from an inverter 31, equipped with transistors 38u, 38v, 38w, 38x, 38y, and 38z to the brushless DC motor 29; the current of the above AC power is detected by detecting the curents flowing to shunt resistors 33, 34, and 51 connected to the transistors at the lower arms of an inverter; and in case that the degree of modulation at generation of a pulse width modulation signal outputted from the controller to the inverter is one or larger; and the controller computes the current in a section, where the current will not flow continuously to an optional shunt resistor, from the currents which flow to other shunt resistors.