Abstract: A thermal control variable speed DC brushless fan, especially a DC brushless fan which may change speed in accordance with the temperature sensed, includes a fan speed control circuit and a DC brushless fan. The fan speed control circuit is composed of drive ICs, operation amplifiers, transistors, diodes, capacitors resistors, and a thermal sensor. Under normal conditions, the change in the fan's rotation speed relation to the temperature is almost linear, but when the thermal sensor is open or shorted the speed control circuit of the fan causes the fan to operate at full speed to maintain a cooling effect.