PURPOSE: To always stably control by detecting a FG pulse interval and the rotating direction of a motor, and forcibly generating a reverse torque.

CONSTITUTION: A reverse torque brake circuit generates a reverse torque by a servo IC 11, etc., and decelerates a motor. The IC 11 compares at speed and phase a FG signal input through a low pass filter formed of a resistor R10 and a capacitor C10, an inverter 15 with a hysteresis and a capacitor C11 with a reference signal of a crystal vibrator X1, and feeds it back to a servo signal input line 3P. A power ON reset signal is output by a resistor R12 and a capacitor C13. The output signals of Hall elements 6, 7 are input to a D latch circuit 18 through amplifiers 12, 13, etc., and the outputs of RS flip-flops 19∼20, the output of the latch circuit and a signal of logic product 21 of a motor ON/OFF signal are input to a rotating direction input line 2P.