Patent ID: 6340874
Filing Date: 2002-01-22
Classification: H05K

Abstract:
Apparatus for reducing fan noise in a personal computer having at least one fan with a direct current motor which is disposed within and ventilates a zone, the noise generated by the fan being a monotone non-decreasing function of the rotational rate of the fan whereby minimizing the rotation rate of the motor for the current temperature in the ventilating zone minimizes the fan noise at that temperature, said apparatus comprising:a thermo-sensor positioned within the zone adjacent the fan and producing a first voltage which is a measurement of the actual temperature; a direct voltage power supply; a digital data storage file device which contains for said fan a table listing for each of a range of discrete temperature values an associated minimum voltage which when supplied to the fan motor will minimize the rotation rate accordingly; and a controller connected between the fan motor and the power supply to modify the output voltage from the supply and to supply the modified voltage to the motor, the controller receiving as a first input said first voltage to read the actual temperature voltage value in the zone, said controller receiving as a second input the voltage data from said device in order to compare the actual zone temperature voltage value with the range of temperature voltage values in the file to select the nearest superior discrete temperature voltage value, the minimum voltage associated with said superior discrete voltage value being supplied by the controller to the motor to minimize the fan noise accordingly.