SPEED CONTROL CIRCUIT OF DC MOTOR

摘要

PURPOSE:To enhance the reliability of controlling a DC motor by discriminating the magnitude of a duty cycle of a PWM signal to convert the polarity of a current detection signal. CONSTITUTION:An energization instructing circuit A2 outputs an energization command signal in response to a deviation between a current command signal in response to a speed deviation and a current feedback signal from a circuit X, a comparator A3 compares the energization command signal with a triangular wave of the prescribed period and outputs a pulse width modulation signal (PWM signal). Drivers D1, D2 alternately turn ON transistors Q5, Q6, and Q7, Q8 during H, L period of the PWM signal. The circuit X discriminates whether the duty cycle of the PWM signal is larger or smaller than 50% to close a switch SW1 or SW2, and outputs the output signal of a current detecting resistor R15 through an amplifier A5 or an inversion amplifier A6.