Fan control device

Abstract

A fan control device is used for controlling at least one fan. The fan control device comprises a signal modulation unit and a shield unit. The signal modulation unit is used for providing a modulation signal and a duty status signal. The shield unit is coupled to the signal modulation unit and the at least one fan for receiving a standby voltage, the duty status signal, and the modulation signal, as well as for shielding the modulation signal or transmitting the modulation signal to the at least one fan according to the standby voltage and the duty status signal.

What is claimed is: 
     
         1 . A fan control device for controlling at least one fan, the fan control device comprising:
 a signal modulation unit for providing a modulation signal and a duty status signal; and   a shield unit coupled to the signal modulation unit and the at least one fan for receiving a standby voltage, the duty status signal, and the modulation signal, as well as for shielding the modulation signal or transmitting the modulation signal to the at least one fan according to the standby voltage and the duty status signal.   
     
     
         2 . The fan control device according to  claim 1 , wherein before the signal modulation unit finishes an initialization stage, the signal modulation unit provides the duty status signal at a high logic level and the modulation signal at the high logic level, and the shield unit shields the modulation signal of the high logic level according to the duty status signal of the high logic level. 
     
     
         3 . The fan control device according to  claim 1 , wherein when the signal modulation unit finishes an initialization stage, the signal modulation unit provides the duty status signal at a low logic level and the modulation signal in a pulse form, and the shield unit transmits the modulation signal in the pulse form to the at least one fan according to the duty status signal at the low logic level. 
     
     
         4 . The fan control device according to  claim 1 , wherein the signal modulation unit provides the duty status signal via a general purpose input/output pin. 
     
     
         5 . The fan control device according to  claim 1 , wherein the shield unit comprises:
 a transistor including a first end, a second end, and a third end, the first end of the transistor receives the standby voltage and the duty status signal, the second end of the transistor receives the modulation signal, and the third end of the transistor is coupled to a ground end.   
     
     
         6 . The fan control device according to  claim 1 , further comprising a power supply coupled to the shield unit for providing the standby voltage, and the power supply is further coupled to the signal modulation unit and the at least one fan for providing an operating voltage required for the signal modulation unit and the at least one fan.