The present invention relates generally to control systems, and more particularly to providing nonlinear control of a fan for temperature controlled systems.
Intelligent system temperature control is an important consideration for many electronic systems, including systems such as personal computers. Such systems can be designed to vary the speed of a fan to regulate the temperature of the system. The speed of the fan is controlled by measuring a temperature of the system, selecting a desired fan speed in accordance with the measured temperature, and signaling the fan driver with a signal that conveys the target fan speed. Changes in the fan speed result in audible changes in the sound generated by the fan.
The present invention is directed towards a nonlinear fan control system for limiting the rate of change in fan speed control signals. The control system includes a controller that produces a nonlinear (or piecewise linear approximation of a nonlinear function) fan speed control signal. The nonlinear fan speed control signal can reduce unnecessarily large changes in the fan speed and provide a greater degree of control at higher temperatures. Linear changes in the speed of a fan often result in audible noises that are undesirably distracting. Controlling the fan by using nonlinear exponential step sizes advantageously reduces the apparent fan noise by linearly varying the amount of fan noise in approximately equal percentages between each programmed fan speed. The step sizes are nonlinear with respect to temperature change and are linear with respect to fan noise.
A more complete appreciation of the present invention and its improvements can be obtained by reference to the accompanying drawings, which are briefly summarized below, to the following detailed description of illustrated embodiments of the invention, and to the appended claims.