Patent ID: 6922038

Claim:
A speed control circuit for a dc brushless motor, wherein said speed control circuit is applied to a single phase dc brushless dc motor, comprising: a switch circuit including a plurality of diodes to output a high or low operating voltage to a driver circuit of the motor in response to high and low voltages input from a power supply; and a voltage-detection circuit controlling the switch circuit to switch between the high or low operating voltage in response to changes in the voltage of the power supply; wherein when the voltage-detection circuit senses a high voltage input from the power supply, the switch circuit is actuated to output the high operating voltage to the driver circuit and thus the motor is operated at a high speed; wherein when the voltage-detection circuit senses a low voltage input from the power supply, the switch circuit is actuated to output the low operating voltage to the driver circuit and thus the motor is operated at a low speed, the low operating voltage being adjusted by the switch circuit relative to the low voltage input from the power supply.