MOTOR SPEED CONTROL DEVICE FOR DC MOTOR

摘要

A motor speed control device for a small DC motor in which the speed of rotation of the motor is maintained stable during ambient temperature changes and changes in the load applied to the motor. A temperature compensation resistor is coupled in series with a voltage divider circuit and the combination thereof coupled across the motor. A motor control circuit is provided having first through fourth control terminals. The first control terminal is coupled to the junction between the temperature compensation resistor and the voltage divider circuit, the second control terminal to the voltage division point, the third control terminal to the junction between the voltage divider circuit and the motor, and the fourth control terminal is coupled to ground. The motor control circuit includes an error detecting circuit having inputs coupled to the first and second control terminals with a voltage reference source coupled in series with the first input terminal to the error detecting circuit. The output of the error detecting circuit drives both shunt transistors coupled between the first and fourth control terminals and a drive transistor means coupled between the first and fourth control terminals.