| 摘要 |
PURPOSE:To optimize the ON-OFF ratio of a PWM drive waveform at all times, and to turn a motor smoothly by selecting the optimum driving voltage of the motor from among a plurality of voltage supply means according to the speed of the motor. CONSTITUTION:A phase comparator 5 compares a feedback signal FG from an encodor 11 and a reference frequency signal FS, and outputs a phase comparison signal PC. An adding circuit 8 adds a speed control signal FV output from a microcomputer 3 to the phase comparison signal PC. A comparator 9 converts an output from the adder 8 into a PWM signal by a threshold level determined by an electronic volume 16, and transmits the PWM signal to a driver 10. On the other hand, a select signal generating circuit 23 selects any of power supplies 28-31 driving the motor 11 according to magnification information selected by a ten key 1. |
