Abstract: A fan driving circuit includes a temperature sensor, a super input and output (SIO) chip, an integrator, a feedback circuit, and a control circuit. The temperature sensor is configured for measuring a temperature of a computer component and outputting a temperature signal according to the measured temperature. The SIO chip is configured for converting the temperature signal into a digital pulse width modulation (PWM) signal. The integrator is configured for converting the PWM signal into an analog signal. The feedback circuit is configured for processing a driving voltage powering a fan to dissipate heat from the computer component and outputting a feedback signal for to compare with the analog signal. The control circuit is configured for comparing the feedback signal with the analog signal and outputting a new driving voltage to control the speed of the fan.