| 摘要 |
PURPOSE:To prevent the production of a torque ripple of a 2-phase motor by supplying an exciting current to the stator coils of the motor from a pair of differential amplifiers, thereby mutually cancelling the offset component contained in the both exciting currents. CONSTITUTION:When a power source is applied to a drive circuit, an exciting current 102 is outputted from a differential amplifier 18 which receives a detection signal 100 of high level from a Hall element 12, diodes 44, 46 are conducted by the output, and a differential amplifier 24 inversely amplifies. Since the output voltage of the amplifier 30 is high at the starting time and the output voltage of the amplifier 32 is low, the exciting current 102 is supplied to a stator coil 10. When reaching the rated circuit, a condenser 40 operates as a bypass condenser, and the amplifier 24 again operates as an inverting amplifier. The gain of the amplifier 24 is set by resistors 34, 38 at the rated rotation time, and the phase difference of the output voltages of the amplifiers 30, 32 are at 180 deg.. Accordingly, the offset due to the differential voltage of the outputs of the amplifiers 30, 32 can be cancelled each other. |
