Patent ID: 7012390

Claim:
A method for controlling a variable speed fan, said method comprising: (a) providing a variable speed fan and a fan control circuit, wherein said fan control circuit includes: a processing circuit, a memory circuit, an output circuit that generates a control signal to said fan, and an input circuit that receives a speed signal from said fan; (b) communicating said control signal having an predetermined value to said fan; (c) receiving said speed signal from said fan that indicates an actual rotating speed of said fan, based upon said predetermined value of the control signal; (d) determining if said fan actual rotating speed is within a predetermined range of acceptable operating speeds, and if not, determining if said fan requires one of: (i) a fine adjustment to said rotating speed, and (ii) a coarse adjustment to said rotating speed; (e) adjusting a value of said control signal according to one of said fine adjustment and said coarse adjustment, and communicating said adjusted control signal to said fan; and (f) repetitively: performing said determining step (d) and said adjusting step (e), as needed, until said fan actual rotating speed is within said predetermined range of acceptable operating speeds.