| 摘要 |
According to this invention, there is provided a drive circuit for a multi-phase brushless DC motor comprising a rotational position detector for detecting a rotational position of a rotor of the motor, a commutation control device for selecting a drive coil to be conducted from the plurality of drive coils, a drive output circuit for supplying a drive current to the drive coil selected by the commutation control devices, a DC servo control loop for detecting a motor speed on the basis of a counter electromotive voltage by rotating the motor and by supplying the drive current from the drive output circuit to the motor, and generating a comparison output in accordance with a difference between the motor speed detection output level and the reference voltage to output the comparison output to the drive output circuit through the commutation control device, and a control device for detecting whether the drive current of the drive output circuit is a predetermined value or more and for weakening a control force of the DC servo control loop when the drive current is the predetermined value or more.
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