| 摘要 |
A brushless DC motor in which rotor magnetic poles were sine wave polarized is used. A rotational speed of the motor is detected by using one of Hall elements built in the DC motor. A control gain (A) to maintain the motor at a specified rotational speed is detected. Drive signals of three phases which were sine wave amplitude modulated on the basis of the detected rotational speed and the detected gain are supplied to the DC motor. A pulse amplitude control circuit which is used to activate the motor is used as a gain sensor. A gain which is used for the sine wave amplitude modulation is detected from a pulse amplitude modulation signal.
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