Patent ID: 8378614

Claim:
A fan control circuit, comprising: a first switch element, the first switch element comprising a first control terminal, a first terminal, and a second terminal; the first control terminal connected to a fan control terminal, the fan control terminal configured to output a pulse width modulation signal, and the first terminal connected to a first voltage source; a second switch element, the second switch element comprising a second control terminal, a third terminal, and a fourth terminal; the second control terminal of the second switch element connected to the first terminal of the first switch element, and the fourth terminal of the second switch element connected to a second voltage source via a negative temperature coefficient resistor; and a fan connector configured to connect to a fan, the fan connector comprising a first pin, a second pin and a third pin; the first pin connected to ground, the second pin connected to the third terminal of the second switch element, the second pin configured to input startup signal to the fan if the second pin is at high level, the third pin connected to a signal receiving terminal, and the third pin configured to receive a feedback signal from the fan indicating a rotating speeding of the fan; wherein the second pin is at high level if the pulse width modulation signal is a high level signal, and the second pin is at low level if the pulse width modulation signal is a low level signal.