Electricity: motive power systems – Automatic and/or with time-delay means – Responsive to thermal conditions
Reexamination Certificate
2002-09-30
2004-05-18
Duda, Rina (Department: 2837)
Electricity: motive power systems
Automatic and/or with time-delay means
Responsive to thermal conditions
C318S445000, C318S461000, C318S472000
Reexamination Certificate
active
06737824
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to control systems, and more particularly to controlling the acceleration of a fan for temperature controlled systems.
BACKGROUND OF THE INVENTION
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.
SUMMARY OF THE INVENTION
The present invention is directed towards a fan acceleration control system for limiting the rate of change in fan speed control signals. The control system includes an acceleration controller that low pass filters a target fan speed control signal. The low pass filtering signal minimizes abrupt changes in the fan speed. A sudden change in the speed of the fan often results in an audible noise that is undesirably distracting. Filtering the fan speed control signal advantageously slows the rate of the fan speed changes without having to change device drivers for controlling the fan.
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Aslan Mehmet
Henderson Richard Dean
Duda Rina
Hennings Mark R.
McCloud Renata
Merchant & Gould
National Semiconductor Corporation
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