FAN CONTROL CIRCUIT

摘要

A fan control circuit includes a hardware controller, a rectifier circuit, first to third electronic switches, and a fan. When the hardware controller outputs a pulse width modulation (PWM) signal to the rectifier circuit and the fan, the rectifier circuit transforms the PWM signal into a direct current (DC) voltage and outputs the DC voltage to the first electronic switch. The first electronic switch is turned on, and the second and third electronic switches are turned off. A rotation speed of the fan is controlled by the PWM signal received from the hardware controller. When the hardware controller does not output the PWM signal, the first electronic switch is turned off, the second and third electronic switches are turned on, a DC power supply supplies power to the fan through the third electronic switch, and the fan rotates at full speed.

主权项

1. A fan control circuit comprising:
a first resistor and a second resistor; a fan comprising a control pin; a hardware controller connected to the control pin of the fan; a rectifier circuit connected to the hardware controller; a first electronic switch comprising a first terminal connected to the rectifier circuit, a second terminal connected to a direct current (DC) power supply through the first resistor, and a third terminal grounded; a second electronic switch comprising a first terminal connected to the second terminal of the first electronic switch, a second terminal connected to the DC power supply through the second resistor, and a third terminal grounded; and a third electronic switch comprising a first terminal connected to the second terminal of the second electronic switch, a second terminal connected to the control pin of the fan, and a third terminal connected to the DC power supply; wherein when the hardware controller outputs a pulse width modulation (PWM) signal to the rectifier circuit and the control pin of the fan, the rectifier circuit transforms the PWM signal into a DC voltage and outputs the DC voltage to the first electronic switch, the first electronic switch is turned on, the second and third electronic switches are turned off, a rotation speed of the fan is controlled by the PWM signal received from the hardware controller; and wherein when the hardware controller does not output the PWM signal, the rectifier circuit does not output the DC voltage, the first electronic switch is turned off, the second and third electronic switches are turned on, the DC power supply supplies power to the control pin of the fan through the third electronic switch, and the fan rotates at full speed.