Patent ID: 7327114
Filing Date: 2008-02-05
Classification: H05K

Abstract:
1. A computer fan control system for controlling the operating speed of a fan, said fan control system being able to operate in multiple modes, said fan control system including: a system controller which specifies a desired speed for said fan, said desired speed being subject to change over time, a fan controller, a first connection for carrying signals between said system controller and said fan controller, said system controller being adapted to transmit a Pulse Width Modulated (PWM) signal on said first connection, the frequency of said PWM signal indicating a mode of operation for said fan control system and the duty cycle of which indicates a desired fan speed, and a second connection between said system controller and said fan controller, said system controller and said fan controller being adapted to communicate bi-directionally over said second connection during a certain mode of operation of said fan control system and said fan controller being adapted to transmit a tachometer signal indicating fan speed over said second connection during a particular mode of operation of said fan control system.