| 摘要 |
PURPOSE:To prevent the increase in the loss of a main switching element by maintaining at constant value the hysteresis width of a comparator by a PWM frequency holding loop irrespective of the frequency of a main circuit. CONSTITUTION:An AC motor 14 is driven by a drive current 102 which is outputted from a main circuit 12. The drive current 102 is detected by a current detector 16, and the detection signal is supplied as a feedback signal 104 to a control circuit. The feedback signal 104 and the PWM command signal 106 are supplied to a comparator 18, which generates a PWM control signal 100 by utilizing the hysteresis width. The signal 100 is applied through a gate amplifier 30 to the main circuit 12, and the output frequency is maintained constantly by the PWM frequency holding loop made of a monostable multivibrator 44 and an amplifier 46. |
