Electricity: motive power systems – Plural diverse motor controls – Running-speed control
Reexamination Certificate
1999-05-10
2002-04-30
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Plural diverse motor controls
Running-speed control
C318S434000, C318S471000
Reexamination Certificate
active
06380704
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fan speed controller, more particularly, to a fan speed controller that uses an external fan voltage to control the speed of a fan in such a manner that the speed of the fan is linearly related to the external fan voltage.
2. Description of Related Art
Heat-dissipation management for PCs (personal computers) and related products has become a popular topic as the size of the PC and other electronic appliances gets smaller and the electronic elements get more powerful so that the heat generated by the electronic elements in the PC has to be removed efficiently. U.S. Pat. No. 5,526,289 granted to Dinh et al. disclosed a temperature dependent fan control circuit for a PC that controls the rotation of a fan such that the speed of the fan is adjusted based on the temperature within the PC housing. This conventional fan control circuit uses a thermistor to sense the ambient temperature in the PC housing whereby the speed of the fan is controlled in a linear relationship to the ambient temperature. That is, when the ambient temperature is high, the speed of the fan is also high. On the contrary, when the ambient temperature is low, the speed of the fan is also low. Therefore, the fan is maintained at the lowest possible speed for effective heat dissipation so that the power consumption is reduced and the noise generated by the fan rotation is decreased. However, with such a conventional fan control circuit, the speed of the fan is only a function of the ambient temperature in the PC housing. Sometimes, the ambient temperature does not actually reflect the abnormal operational conditions of the PC such that the fan is locked or the fan is improperly controlled. Therefore, there is a need for the above fan control circuit to be improved.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide a fan linear speed controller that controls the speed of a fan relative to an external fan voltage and further provides a fault signal to indicate the abnormal operational conditions of the fan.
To achieve this objective, the fan linear speed controller in accordance with the present invention includes a temperature sensor unit, a linear speed control unit and a fault detection unit. The temperature sensor unit has a thermistor for detecting the ambient temperature of the fan to generate a thermally sensitive voltage. The linear speed control unit receives an external fan control voltage and the thermally sensitive voltage to generate an output voltage to drive the fan, wherein the output voltage is proportional to the fan control voltage when the thermally sensitive voltage is lower than a preset threshold voltage and the fan control voltage is higher than a preset reference voltage. The fault detection unit receives the thermally sensitive voltage and a rotation speed signal generated by the fan to selectively produce a fault signal indicating that the rotation of the fan is abnormal or the ambient temperature of the fan is too high.
Other objectives, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4124001 (1978-11-01), Samuel et al.
patent: 4552205 (1985-11-01), Saunders
patent: 5790430 (1998-08-01), Steiert
patent: 6040668 (2000-03-01), Huynh et al.
patent: 6188189 (2001-02-01), Blake
Nillson et al, “Electric Circuits”, Fifth Edition, Addison-Wesley Publishing Company, 1996. Pp. 179-180.
Pelton, Esq. William E.
Ro Bentsu
Silicon Touch Technology Inc.
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