Patent ID: 7425812

Claim:
A method for controlling the rotational speed (RPM) of at least one fan, the method comprising: specifying a plurality of RPM range values; specifying a plurality of ramp rates, wherein each one of the plurality of ramp rates corresponds to a different respective one of the plurality of RPM range values; determining a difference between a present RPM of the at least one fan and a desired RPM of the at least one fan, by comparing the desired RPM and the present RPM; selecting a present ramp rate from the plurality of ramp rates, wherein the present ramp rate corresponds to a largest one of the plurality of RPM range values that is less than the size of the difference between the desired RPM and the present RPM; adjusting the present RPM according to the difference between the desired RPM and the present RPM and at the present ramp rate, to reach the desired RPM; and adjusting a present value of at least one of the plurality of RPM range values in response to said determining.