| 摘要 |
A motor driving apparatus disclosed herewith is designed in such a way that a drive current is supplied through a switching circuit to a DC motor, such as a three-phase brushless motor, from a DC power source and the rotational speed and phase of a signal has a frequency proportional to the rotational speed of the DC motor are detected by a rotational speed detector and a phase detector. Signals detected by the speed detector and phase detector are respectively supplied to a speed comparator and a phase comparator for comparison with the respective predetermined values. The comparison results are then added and the resultant signal is sent to a subtracter. The applied voltage of the DC motor which has undergone ON/OFF control in a switching circuit is detected by a voltage detector, and the detection signal is subtracted from the added signal in the subtracter, and the resultant signal is supplied as a control signal to a signal generator. This signal generator changes the ratio of the ON/OFF signal supplied to the switching circuit in accordance with the control signal from the subtracter, whereby the ON/OFF time of the switching circuit is controlled to thereby control the rotational speed and phase of the DC motor.
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