| 摘要 |
PURPOSE:To prevent the overshoot of a motor from occurring at its rising time by advancing a phase control starting timing for a predetermined time when a phase difference becomes lower than a preset value at motor rising time. CONSTITUTION:A phase comparator 15 forms a phase comparison signal PC from a reference frequency signal FS output from a microcomputer 13 and a feedback signal FG. An adder 18 adds the signal PC and a speed control signal FV, and supplies it through a comparator 19 for pulse-width modulating it to a driver 20. One period of the signal FG is measured at motor rising time, and a period difference DELTAt between the measured period tK and the period T of the signal FS is obtained. When the difference DELTAt is smaller than a preset value, the transmitting timing of the signal PC is advanced.
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