FAN MOTOR WITH VARIABLE FREQUENCY/CONSTANT SPEED CONTROL

摘要

A fan motor with variable frequency/constant speed control comprises a frequency comparator, a differential integrating circuit, and a differential amplifier. The frequency comparator calculates a frequency difference between a frequency of an external pulse signal input and a frequency of a speed signal detected from the fan. The differential integrating circuit converts the frequency difference into a voltage signal which is inputted to a negative terminal of the differential amplifier. A predetermined voltage is connected to a positive terminal of the differential amplifier. A voltage value at the negative terminal of the differential amplifier is compared with a voltage value at the positive terminal of the differential amplifier to thereby change a voltage outputted to an input end of the fan.