Apparatus and method for fan auto-detection

A circuit for detecting a type of fan and controlling the fan, the fan providing during operation a tachometer signal indicating a speed of the fan, the circuit comprising:

• an integrated circuit provided on a substrate, the integrated circuit including:
• a direct current (DC) generator for coupling to the fan and configured to provide a first voltage to the fan;
• a resistor for providing, while the DC generator provides the first voltage, a sensed voltage relating to the type of the fan, wherein the resistor is connected to a reference voltage and for coupling to a pulse-width modulation (PWM) control terminal of the fan;
• an input judgment component coupled to the resistor to receive the sensed voltage, the input judgment component being configured to determine whether the fan is a 4-wire PWM fan with an internal pull-up resistor based on the sensed voltage and to provide a judgment signal indicating the determination;
• a PWM generator coupled to the input judgment component to receive the judgment signal, the PWM generator being configured to provide to the fan a PWM control signal to control the fan if the judgment signal indicates that the fan is the 4-wire PWM fan with an internal pull-up resistor;
• and
• a tachometer coupled to the DC generator and the PWM generator, the tachometer being configured to receive the tachometer signal to detect a change in the speed of the fan.