To make it possible to easily perform trapezoidal-wave energization control sensorless drive even if the number of revolutions of a motor fluctuates, by controlling the operation of the motor using a trapezoidal-wave control current generated baied on trapezoidal-wave voltage, and thereby continuously generating trapezoidal-wave control currents.

A commutation mode transition circuit 13 determines a commutation mode according to a motor induced voltage detected through a motor induced voltage detecting circuit 11. A trapezoidal wave forming circuit 16 operates according to the commutation mode, and thereby forms a trapezoidal- wave voltage. A trapezoidal-wave control current is formed based on these trapezoidal-wave voltages. These trapezoidal-wave control currents are amplified through an output amplifier circuit 17, and a motor is fed with a motor current. Since trapezoidal-wave control currents are formed through such operation, trapezoidal-wave control currents can be formed with ease and reliability regardless of a number of revolutions, and a trapezoidal-wave control current corresponding to a number of revolutions of a motor can be formed even if the number of revolutions fluctuates.