| 摘要 |
PROBLEM TO BE SOLVED: To reduce the number of defective pulses to improve reliability by offsetting an induced electromotive voltage while comparing the induced electromotive voltage and coil neutral voltage and then cancelling the offset from a delay signal. SOLUTION: A delayed signal of the position signal is formed by a delay circuit 4, an induced electromotive voltage crosses with a neutral voltage in an offset circuit 8 and when a comparator 2 outputs a normal speed signal, offset is effectuated on the induced electromotive voltage to reduce such voltage up to the power supply voltage or to the ground voltage. Thereby, the switching for power feeding to the drive coils Lu , Lv , Lw and inversion of input comparison voltage depending on waveform disturbance generated in the induced electromotive voltage due to speed error correction, etc., can be eliminated and offset an be cancelled before the next speed detection signal is detected after allowing waveform disturbance depending on the delayed signal. Accordingly, the number of defective pulses can be eliminated and high reliability can also be assured. |
