Drive circuit for a speed automatically adjusted fan

Details Drive circuit for a speed automatically adjusted fan Drive circuit for a speed automatically adjusted fan

2000-02-29

2001-10-02

Nappi, Robert E. (Department: 2837)

Electricity: motive power systems

Automatic and/or with time-delay means

Responsive to thermal conditions

C318S434000

Reexamination Certificate

active

06297608

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a drive circuit for a speed automatically adjusted fan, particularly to a drive circuit, with which the speed of the fan can be properly adjusted depending on the ambient temperature.
2. Description of Related Art
A prior art of drive circuit for a fan, as shown in
FIG. 1
, is illustrated. The output terminal of a Hall IC is connected to the base pole of a transistor (Q
1
′). The collector of the transistor (Q
1
′) is connected to a coil (V
1
′) of the DC fan and then to the base pole of another transistor (Q
2
′) through a resistor (R
2
′). The collector of the transistor (Q
2
′) is connected to another coil (V
2
′) of the fan. Both the emitters in the two transistors (Q
1
′, Q
2
′) are connected to the negative pole of the power supply. The two transistors (Q
1
′, Q
2
′) control the coils (V
1
′, V
2
′) of the fan, while the Hall IC sequentially controls the connection and the disconnection between the two transistors (Q
1
′, Q
2
′) to alternately magnetize of the coils (V
1
′, V
2
′) so as to rotate the fan. However, the circuit passing through the coils (V
1
′, V
2
′) is not possible to be changed so as to adjust the speed of the fan with respect to the ambient temperature once the coils and the power supply are fixedly arranged. It is a trend that the speed of the fan can be a variable with respect to the change of the ambient temperature. In addition to running under a maximum load condition for dissipating the heat, the fan is possible to generate noise either under a minimum load condition.
Therefore, based on regulations of the energy and the noise for the environmental protection, the problems involved in the conventional drive circuit for a fan have to be solved advantageously. In view of the drawbacks of the conventional drive circuit, the inventor has dedicated in research and design and has endeavored tests. Finally, a drive circuit for a speed automatically adjusted fan in accordance with the present invention is developed.
SUMMARY OF THE INVENTION
The drive circuit for a speed automatically adjusted fan according to the present invention resides in that the drive circuit is comprised of an actuating circuit, a temperature control circuit and a current control circuit. The actuating circuit has a Hall IC to control two transistors in a state of connecting and in a state of disconnecting sequentially to alternately magnetize two coils respectively so as to rotate the fan. A heat sensitive resistor in the temperature control circuit senses the temperature and changes its resistance with respect to a variation of the temperature such that the current passing through has the magnitude thereof be controlled. Thus, the current is fed back into the actuating circuit through the current control circuit and speed of the fan can be changed with respect to the magnitude of the current.
An objective of the present invention is to provide a drive circuit for a speed automatically adjusted fan with which the speed of the fan can be controlled automatically in accordance with the ambient temperature around the fan.


REFERENCES:
patent: 3560824 (1971-02-01), Burke
patent: 3801888 (1974-04-01), Faulkner
patent: 4722669 (1988-02-01), Kundert
patent: 4748388 (1988-05-01), Muller
patent: 4804902 (1989-02-01), Maier
patent: 4806832 (1989-02-01), Muller
patent: 5093891 (1992-03-01), Komiyama et al.
patent: 5197858 (1993-03-01), Cheng
patent: 5363024 (1994-11-01), Hiratsuka et al.
patent: 5457766 (1995-10-01), Ko
patent: 5563480 (1996-10-01), Okada
patent: 5831405 (1998-11-01), Massie

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