Fan control method

A fan control method, adapted to a mother board having a processor electrically connected to a fan for cooling the mother board, comprising:

• determining whether a processor power load value is larger than a load threshold, and generating a load determination result accordingly;
• determining whether a processor temperature is not larger than a temperature threshold, and generating a temperature determination result accordingly;
• choosing one set of PID coefficients from a plurality of sets of PID coefficients according to the load determination result and the temperature determination result, wherein the set of PID coefficients at least includes a portion coefficient and a corresponding integration coefficient;
• obtaining a temperature difference value related to the processor, and generating a first pulse width modulation value according to the temperature difference value and the set of PID coefficients;
• and
• receiving an operation temperature of an electronic component on the mother board, calculating a second pulse width modulation value corresponding to the operation temperature, and comparing the first pulse width modulation value with the second pulse width modulation value for obtaining a maximum of the first pulse width modulation value and the second pulse width modulation value to generate a fan control signal for controlling the fan.