SERVO-DRIVER

摘要

PROBLEM TO BE SOLVED: To avoid distortions in the voltage and current of a 3-phase AC power supply when a 3-phase AC power supply voltage exceeding the DC voltage of a filter capacitor is inputted. SOLUTION: The diodes D1-D6 of a 3-phase bridge rectifier circuit 3 rectify an input AC voltage and supply the rectified voltage to a filter capacitor 4. The transistors Q1-Q6 of the rectifier circuit 3 are controlled to be turned on/off by a transistor control circuit 13 and regenerate the DC voltage to the 3-phase AC power supply. A differential detection circuit 9 detects a differential voltage between a DC voltage Vd detected by a DC voltage detector and a previously specified voltage Vs. A differential detection circuit 10 detects a differential voltage between the peak value of the 3-phase AC power supply which is detected by an AC voltage detector 8 and the DC voltage Vd. A switch 12 selects the output of the differential detection circuit 10 if the comparison result of a comparison circuit is Vs<=Vp. The transistor control circuit 13 controls the ON's/OFF's of the transistors Q1-Q6 so as to have the DC voltage Vd follow the peak value Vp of the 3-phase AC power supply voltage in accordance with the differential voltage Vpd.