Computer fan speed control method

#The benefit under 35 U.S.C. .sctn.119(e) of the following U.S. provisional application(s) is hereby claimed:

#______________________________________ Application Title No. Filing Date ______________________________________ "Hardware and Software Architecture for 60/047,016 May 13, 1997 Inter-Connecting an Environmental Management System with a Remote Inter- face" "Self Management Protocol for a Fly-By- 60/046,416 May 13, 1997 Wire Service Processor" "Isolated Interrupt Structure for Input/ 60/047,003 May 13, 1997 Output Architecture" "Three Bus Server Architecture with a 60/046,490 May 13, 1997 Legacy PCI Bus and Mirrored I/O PCI Buses" "Computer System Hardware Infrastruc- 60/046,398 May 13, 1997 ture for Hot Plugging Single and Multi- Function PC Cards Without Embedded Bridges" "Computer System Hardware Infrastruc- 60/046,312 May 13, 1997 ture for Hot Plugging Multi-Function PCI Cards With Embedded Bridges" ______________________________________

#Appendix A, which forms a part of this disclosure, is a list of commonly owned copending U.S. patent applications. Each one of the applications listed in Appendix A is hereby incorporated herein in its entirety by reference thereto.

#FIG. 1 is a perspective view of one exemplary cooling fan mounted adjacent an electrical component of a personal computer;

#FIG. 2 is a block diagram illustrating one embodiment of a control circuit for a single speed DC fan;

#FIG. 3 is an electrical schematic illustrating the control circuit of FIG. 2 in greater detail;

#Reference will now be made to the drawings wherein like numerals refer to like parts throughout. FIG. 1 illustrates a typical cooling fan assembly 100 used in one embodiment of the invention. In particular, the cooling fan assembly 100 includes a fan 101 that has a fan blade 102 that is mounted about a shaft 104 so as to be positioned within a housing 106. The housing 106 is attached to a mount 108 that is mounted in the personal computer so that the fan blades 102 can cool an electrical component 110.

#In the embodiment shown in FIG. 1, the cooling fan assembly 100 is mounted on posts 112 that are attached to a printed circuit board 114 so that the cooling fan blades 102 blow cool air over an integrated circuit 110 that is mounted on the printed circuit board 114. In this manner, the operation of the fan assembly 100 reduces the ambient temperature surrounding the integrated circuit 110 and thereby dissipates the heat that is produced by the integrated circuit 110. It will be appreciated, however, that the fan 101 may be mounted in any of a number of well-known manners without departing from the spirit of the invention. For example, the fan may also be mounted in a sidewall of a chassis of the computer so as to allow the fan to draw cool air into the chassis from the outside environment or to expel hot air from the chassis to the cooler outside environment.

#A control circuit 120 (FIG. 2) is used to control the operation of the fan assembly 100 in a manner that will be described below. In one embodiment, the fan assembly 100 includes a DC fan 101 such as a Model FBA09A12M single speed fan manufactured by Panasonic. It will be appreciated from the following discussion that the control circuit 120 of this embodiment can be used in conjunction with DC fan assemblies such as single speed fans that are mounted in any of a number of well-known manners within the chassis of a personal computer or any other electronic device requiring forced air cooling.