SENSORLESS MOTOR DRIVING CIRCUIT

PROBLEM TO BE SOLVED: To provide a motor driving circuit which is suitable for low consumption of power in an equipment such as a headphone stereo which is provided with a sensorless motor. SOLUTION: In a sensorless motor driving circuit which rotates a rotor by switching currents in armature windings 6, 7, 8, induced voltages Eu, Ev, Ew which are generated in the armature windings 6, 7, 8 due to rotation of a sensorless motor are compared with a reference voltage 19 by comparators 16, 17, 18. By letting transistors 20, 21, 22 conduct according to the output signals Su, Sv, Sw of the comparators 16, 17, 18, current is prevented from being supplied to a current amplifier circuit 4 from a voltage/current converting circuit 3 during a period when the armature windings 6, 7, 8 do not conduct. By this method, unnecessary current in the armature windings 6, 7, 8 is eliminated and acoustic noise and spike noise are suppressed and low consumption of power is accomplished.