Patent ID: 6499960
Filing Date: 2002-12-31
Classification: F04D,Y02B

Abstract:
A control circuit for controlling the rotational speed of a heat-dissipation fan for an electronic device, said fan having a permanent magnet and a coil, said control circuit comprising:a temperature sensing circuit for sensing the ambient temperature of the device and providing a temperature signal related thereto; a comparator circuit for receiving said temperature signal and for comparing said temperature signal with a predetermined threshold and providing a comparison signal related thereto; a circuit for detecting the phase of the fan magnet and for providing a phase signal related thereto; a drive circuit for receiving said phase signal and said comparison signal and for driving said coil to control the rotational speed of said fan, when the ambient temperature is above said threshold, to change substantially linearly with respect to the difference between the ambient temperature and the threshold and, when the ambient temperature is below said threshold, to stop the rotation of the fan.