Abstract: A pulse generation unit generates a PWM signal whose duty ratio changes according to a target torque of a motor. A back electromotive detection circuit compares a back electromotive voltage generated at a coil of the motor with a middle point voltage of the coil, and outputs a back electromotive detection signal that becomes high level at a timing of the zero crossing point. A phase adjustment unit compares phases of the back electromotive detection signal and a reference signal that becomes a predetermined level at a predetermined timing, and adjusts the duty ratio of the PWM signal by feedback so that the phase error becomes a minimum. A frequency adjustment unit adjusts the frequency of the PWM signal such that the frequency of the PWM signal becomes integral multiples of the frequency of the back electromotive detection signal.