TWI765255B

Provided is a fan control circuit which is used for controlling at least one fan of a power supply unit. The fan control circuit includes a load sensing unit, a temperature sensing unit, a control unit connected with the load sensing unit, the temperature sensing unit and the fan, and a mode switching unit; the load sensing unit generates a load signal based on an output condition of the power supply unit; the temperature sensing unit senses the temperature in the power supply unit and generates a temperature signal; the control unit has a low-speed operating mode for controlling the fan based on the load signal, a silent mode for controlling the fan based on the temperature signal and a full-speed operating mode for controlling the fan to work at a rated rotating speed; and the mode switching unit makes the control unit adjust the rotating speed of the fan according to one of the three modes.