Fan detection chip, a method and a system using the same

A fan detection method, applicable to a fan detection chip for detecting a type of a fan, and the fan detection chip comprising a first pin, a second pin, a third pin, a power supply module, a PWM signal generating module, a current sensing module and a control module, and the fan detection method comprising:

• generating, by the PWM signal generating module, a first PWM signal and transmitting the first PWM signal to a PWM signal terminal of the fan;
• sensing, by the current sensing module, a first current flowing from the power supply module to a power terminal of the fan;
• generating, by the PWM signal generating module, a second PWM signal which has a duty cycle different from a duty cycle of the PWM signal, and transmitting the second PWM signal to the PWM signal terminal;
• sensing, by the current sensing module, a second current flowing from the power supply module to a power terminal of the fan;
• and
• comparing, by the control module, the first current with the second current, and determining the fan to be a PWM fan when the first current is different from the second current, and determining the fan to be a DC fan when the first current is the same as the second current.

A fan detection system, comprising:

• a fan comprising a power terminal and a speed signal terminal, and optionally comprising a PWM signal terminal;
• a power supply module electrically coupled to a supply input terminal, and configured to provide a driving voltage to the fan;
• a PWM signal generating module electrically coupled to the PWM signal terminal, and configured to provide a first PWM signal and a second PWM signal which respectively have different duty cycles;
• a current sensing module disposed between the power supply module and the supply input terminal, and configured to sense a first current flowing from the power supply module when the PWM signal generating module provides the first PWM signal, and sense a second current flowing from the power supply module when the PWM signal generating module provides the second PWM signal;
• and
• a control module electrically coupled to the power supply module, the PWM signal generating module and the current sensing module, and configured to receive and compare the first current and the second current, wherein the control module determines the fan to be a PWM fan when the first current is different from the second current, and the control module determines the fan to be a DC fan when the first current is the same as the second current.