To provide a motor controller which can avoid demagnetization of a permanent magnet, even if a rotor rotates in a reverse direction beforehand, when a permanent magnet DC brushless motor is started.
A control unit decides a rotation direction of a rotor according to a change of a position detection signal from a Hall sensor attached to a motor. When the motor is driven by manipulation from the outside, if a rotor is in a stationary state (S71) or a present rotation direction is same as the driving direction (S72), the control unit permits the motor drive and outputs ON control signals by which prescribed transistors are turned on (S73), and a drive current is supplied to a winding. If the present rotation direction is opposite to the driving direction, however, the motor drive is prohibited and all the transistors are cut off (S74). With such a constitution, the rotation direction and the drive direction will not be opposite to each other, so that demagnetization of a permanent magnet can be avoided.
HAN KEIBIN
HARA YASOHACHI
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