Patent ID: 8198838

Claim:
A circuit for controlling a rotation speed of a computer fan, the circuit comprising: a control chip to output a control signal; a conversion circuit; a fan header to mount the computer fan, the fan header comprising a power pin and a control pin; a first switch comprising a first terminal connected to the control chip, a second terminal connected to the conversion circuit, and a third terminal connected to the control pin of the fan header; and a second switch comprising a first terminal connected to the power pin of the fan header, a second terminal connected to the conversion circuit, and a third terminal connected to a first power supply; wherein in response to the first terminal of the first switch being connected to the second terminal of the first switch, and the first terminal of the second switch being connected to the second terminal of the second switch, the conversion circuit receives the control signal from the control chip, converts the control signal to a voltage signal, and outputs the voltage signal to the power pin of the fan header; and wherein in response to the first terminal of the first switch being connected to the third terminal of the first switch, and the first terminal of the second switch being connected to the third terminal of the second switch, the control pin of the fan header receives the control signal from the control chip, the power pin receives power from the first power supply.