Motor speed control apparatus

摘要

A motor speed control apparatus includes a ladder resistor circuit, a reference signal generator, and a comparator. The ladder resistor circuit selectively receives a voltage signal having a predetermined amplitude at a plurality of nodes. The ladder resistor circuit arranged to change an output voltage value thereof in accordance with a voltage application position. The level of the reference signal generator is periodically changed. The comparator compares a voltage value of the reference signal with an output voltage value of the ladder resistor circuit and outputs a pulse output having a variable pulse width on the basis of a comparison result. A motor speed is controlled on the basis of the pulse output.