Patent ID: 7841837

Claim:
A cooling-fan control circuit, used to determine the rotation speed of at least one cooling fan, said control circuit comprising: at least two separate input power sources that provide power to drive said cooling fan, said input power sources including a low-voltage input power source and at least one high-voltage input power source which supply electric current to said cooling fan through separate power-providing lines, said low-voltage input power source being electrically coupled to said cooling fan continuously; a separation element installed between said low-voltage input power source and said cooling fan; and a switch installed on at least one power-providing line between at least one said high-voltage input power source and said cooling fan, acquiring a rotation-speed parameter to determine the on/off setting of said switch and thereby determine whether said cooling fan is driven by the low-voltage input power source or one of the high-voltage input power sources according to said rotation-speed parameter.