Speed control circuit for a DC brushless motor

摘要

A motor speed control circuit includes a switch circuit and a voltage-detection circuit. The voltage-detection circuit is actuated depending upon high or low voltage of a power supply to thereby cause the switch circuit to output high or low operating voltage to a driver circuit of the motor in response to changes of the voltage of the power supply. The motor is adjusted and operated at desired speeds by a rated range of input voltages according to the high or low operating voltage.