| 摘要 |
PURPOSE:To obtain a Hall motor drive circuit which suppresses the generation of a torque ripple in the prescribed range by cancelling the offset voltage which exists during the outputting of a Hall element at the rotating time in the prescribed range from the rated speed. CONSTITUTION:A field effect transistor 16 is turned OFF by the range speed detection signal which is supplied to a terminal 28 when a Hall motor enters the rotating speed in the prescribed range from the rated speed, the non-inverting input of an operational amplifier 11 is grounded through a capacitor 15, the amplifier 11, resistors 12-14 and the capacitor 15 operate as an inverting amplifier having substantially 1 of gain to the AC input of frequency higher than the cut-off frequency by a resistor 14 and a condenser 15, and acts as a non- inverting amplifier having 1 of gain to the DC input. Accordingly, the offset component which is contained in the output of a differential amplifier 6 and the offset component which is amplified by noninversion by the amplifier 11 having the above characteristic are cancelled each other to prevent the production of torque ripple. The operation of the remaining phase is similar. |
