Fan system and driving control device of motor

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 095138042 filed in Taiwan, Republic of China on Oct. 16, 2006, the entire contents of which are hereby incorporated by reference.

1. Field of Invention

The invention relates to a driving control device, and more particularly to a fan system and a driving control device of a motor.

2. Related Art

The heat dissipating problem of an electronic device is more and more important nowadays due to the increase of the data processing information and the processing speed of the electronic device. In addition, the integrated process had become advanced so that more electronic elements can be contained in the same electronic device. The major heat dissipating method is to provide a fan in or on the electronic device for inducing the air convection so as to achieve the heat dissipating effect.

Accordingly, the thermal controlled fan, which can sense the environment temperature by a sensing element and adjusts the rotation speed thereof in accordance with the temperature, is disclosed. The sensing element can be a thermal resistor, which is sensitive to the temperature variation and can change its resistance value according to different temperatures. In addition, the thermal resistors include a positive temperature coefficient (PTC) resistor and a negative temperature coefficient (NTC) resistor. The resistance of the PTC resistor increases and that of the NTC resistor decreases when the temperature increases. Now, the thermal resistor is widely applied as the sensing element in the electronic device for facilitating the control and compensation of other circuits in the electronic device.

FIG. 1A is a schematic block diagram of a conventional fan system 1 , and FIG. 1B is a schematic circuit diagram of the fan system 1 in FIG. 1A . Referring to FIGS. 1A and 1B , the fan system 1 includes a temperature sensing circuit 11 , a driving circuit 12 and a fan 13 . The temperature sensing circuit 11 senses an environment temperature for generating a sensing signal S 11 . The driving circuit 12 receives the sensing signal S 11 and transfers it into a driving signal S 12 so as to drive the fan 13 .

The temperature sensing circuit 11 has a resistor R and a thermal resistor RT, which are connected in series so as to divide the operating voltage V CC . The thermal resistor RT generates a resistance in accordance with the environment temperature. The variation of the resistance causes a node voltage value V 1 with variation between the thermal resistor RT and the resistor R so as to output the temperature sensing signal S 11 . The driving circuit 12 , which is a chip or a microprocessor, receives the temperature sensing signal S 11 and transfers it into the driving signal S 12 so as to drive the motor 131 of the fan 13 .

As mentioned above, the driving circuit 12 of the conventional fan system 1 must receive and transfer the temperature sensing signal S 11 into the driving signal S 12 with a high voltage level or a high current level so as to drive the fan 13 .

In order to adjust the driving signal S 12 in accordance with the temperature variation immediately, the chip of the present driving circuit 12 is usually integrated in a chip with multiple functions and the chip is expensive. In this way, the expensive chip also raises the cost of the whole electronic system. The expensive chip thus limits its application fields. Therefore, it is an important subject to provide a driving control device having low cost and suitable for more application fields.

In view of the foregoing, the present invention is to provide a fan system and a driving control device of a motor, which having low cost and are suitable for more application fields. The fan system and driving control device of the present invention also have two stages of rotation speeds in accordance with the environment variation.

To achieve above, the invention discloses a driving control device of a motor. The driving control device includes a temperature sensing circuit, a comparing circuit, a rotation speed control circuit and a driving circuit. The temperature sensing circuit senses an environment temperature to generate a sensing signal. The comparing circuit is electrically connected to the temperature sensing circuit and compares the sensing signal with a reference voltage signal to output a comparing signal. The rotation speed control circuit is electrically connected to the comparing circuit and has a first threshold value and a second threshold value. The rotation speed control circuit generates a rotation speed control signal after comparing the comparing signal with the first and the second threshold values. The driving circuit generates a driving signal to drive the motor in accordance with the rotation speed control signal.

To achieve above, the invention also discloses a fan system having a driving control device and a fan. The driving control device includes a temperature sensing circuit, a comparing circuit, a rotation speed control circuit and a driving circuit. The temperature sensing circuit senses an environment temperature to generate a sensing signal. The comparing circuit is electrically connected to the temperature sensing circuit and compares the sensing signal with a reference voltage signal to output a comparing signal. The rotation speed control circuit is electrically connected to the comparing circuit and has a first threshold value and a second threshold value. The rotation speed control circuit generates a rotation speed control signal after comparing the comparing signal with the first and the second threshold values. The driving circuit generates a driving signal to drive the motor in accordance with the rotation speed control signal. The fan has a motor electrically connected to the driving control device. The motor receives the driving signal so that the rotation speed of the motor can be controlled according to the driving signal.

As mentioned above, the fan system and driving control device of the invention utilizes the comparing circuit to transfer the sensing signal generated by the temperature sensing circuit into the comparing signal, which is then inputted into the rotation speed control circuit so as to generate the rotation speed control signal. When the comparing signal achieves the first threshold value, the rotation speed control circuit outputs a rotation speed control signal indicating a first rotation speed. When the comparing signal achieves the second threshold value, then the rotation speed control circuit outputs another rotation speed control signal indicating a second rotation speed. Therefore, the rotation speed control of the temperature controlled fan can be carried out by the simple design of the comparing circuit and the rotation speed control circuit. Accordingly, the manufacturing cost can be decreased and the rotation speed control circuit can then be applied in more application fields with the fan system or the driving control device of the motor.

The invention will become more fully understood from the detailed description and accompanying drawings, which are given herein below for illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1A is a schematic block diagram of a conventional fan system;

FIG. 1B is a schematic circuit diagram of the conventional fan system in FIG. 1A ;

FIG. 2 is a schematic block diagram showing a fan system according to an embodiment of the invention;

FIG. 3A is a schematic circuit diagram showing the fan system according to the embodiment of the invention; and

FIG. 3B is a schematic diagram showing a variation status of the comparing signal and the rotation speed control signal in the rotation speed control circuit according to the embodiment of the invention.

The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.

FIG. 2 is a block diagram showing a fan system 2 according to an embodiment of the invention. Referring to FIG. 2 , the fan system 2 includes a driving control device 21 and a fan 22 . The driving control device 21 has a temperature sensing circuit 211 , a comparing circuit 212 , a rotation speed control circuit 213 and a driving circuit 214 . The fan 22 has a motor 221 , which is electrically connected to the driving control device 21 .

The temperature sensing circuit 211 senses an environment temperature variation to generate a sensing signal S 21 . The comparing circuit 212 receives the sensing signal S 21 and compares the sensing signal S 21 with a reference voltage signal S 22 to output a comparing signal S 23 .

The rotation speed control circuit 213 has a first threshold value V U and a second threshold value V L . The rotation speed control circuit 213 generates a rotation speed control signal S 24 after receiving the comparing signal S 23 and comparing the comparing signal S 23 with the first threshold value V U and the second threshold value V L .

The driving circuit 214 receives the rotation speed control signal S 24 outputted by the rotation speed control circuit 213 to generate a driving signal S 25 for controlling the motor 221 of the fan 22 .

Please referring to FIG. 3A , which is a circuit block diagram showing each circuit of the fan system 2 .

The temperature sensing circuit 211 has a first resistor R 1 and a sensing element RT 1 . The sensing element RT 1 is electrically connected to the first resistor and a ground. The first resistor R 1 and the sensing element RT 1 divide an operating voltage V CC to generate the sensing signal S 21 . The sensing element RT 1 generates different sensing signal S 21 in accordance with the variation of the environmental temperature. In the embodiment, the sensing element RT 1 is a thermal resistor, and the sensing signal S 21 is a voltage signal divided by the first resistor R 1 and the sensing element RT 1 .

In addition, the sensing element RT 1 can be a positive temperature coefficient (PTC) thermistor, a negative temperature coefficient (NTC) thermistor or a thermocoupler. Each of the PTC thermistor, NTC thermistor and thermocoupler can generate the sensing signal S 21 in accordance with the variation of the environmental temperature.

The comparing circuit 212 includes a comparator U 1 , which has a first input terminal in 1 , a second input terminal in 2 and a first output terminal. The first input terminal in 1 receives the sensing signal S 21 , the second input terminal in 2 receives a reference voltage signal S 22 , and the output terminal outputs the comparing signal S 23 after comparing the sensing signal S 21 with the reference voltage signal S 22 . In the embodiment, the comparator U 1 is an operational amplifier or any element or circuit with the comparing function. In addition, each of the reference voltage S 22 and the comparing signal S 23 is a voltage signal. Moreover, when the reference signal S 22 is greater than the sensing signal S 21 , the comparing signal S 23 will be a high level signal (high voltage signal); otherwise, when the reference signal S 22 is smaller than the sensing signal S 21 , the comparing signal S 23 will be a low level signal (low voltage signal).

Furthermore, the comparing circuit 212 further includes a voltage divided circuit 2121 , which includes a top resistor R top and a third resistor R 3 . One end of the top resistor R top is electrically connected to the operating voltage V CC , and the other end of the top resistor R top is electrically connected to one end of the third resistor R 3 and the second input terminal in 2 . The other end of the third resistor R 3 is electrically connected to the ground. The voltage divided circuit 2121 divides the operating voltage V CC so as to generate the reference voltage signal S 22 , which is inputted into the second input terminal in 2 of the comparator U 1 .

The rotation speed control circuit 213 generates the rotation speed control signal S 24 after receiving the comparing signal S 23 and comparing the comparing signal S 23 with the first threshold value V U and the second threshold value V L . The rotation speed control circuit 213 can be a Schmitt Trigger circuit, a comparator with a delay function or any circuit or element with a delay function. In the embodiment, the rotation speed control circuit 213 is a Schmitt Trigger circuit and the rotation speed control signal S 24 is a voltage signal. The Schmitt Trigger circuit has an operational amplifier U 2 , a fourth resistor R 4 and a fifth resistor R 5 . The operational amplifier U 2 has a third input terminal in 3 , a fourth terminal in 4 and a second output terminal. The third input terminal in 3 receives the comparing signal S 23 , and the fourth terminal in 4 is electrically connected to one end of the fourth resistor R 4 and one end of the fifth resistor R 5 . The second output terminal is electrically connected to the other end of the fourth resistor R 4 and outputs the rotation speed control signal S 24 . The other end of the fifth resistor R 5 is electrically connected to the ground.

Referring to FIG. 3B , in the Schmitt Trigger circuit, when the comparing signal S 23 (the voltage signal V in ) is gradually raised from a lower voltage value to a higher voltage value, which is still smaller than the first threshold value V U , the second output terminal of the operational amplifier U 2 outputs the rotation speed control signal S 24 with a positive saturation voltage signal +V sat . Alternatively, when the comparing signal S 23 (the voltage signal V in ) reaches a higher voltage value that is greater than the first threshold value V U , the second output terminal of the operational amplifier U 2 outputs the rotation speed control signal S 24 with a zero voltage signal 0V. Similarly, when the comparing signal S 23 (the voltage signal V in ) is gradually decreased from higher voltage value to a lower voltage value, which is still greater than the second threshold value V L , the second output terminal of the operational amplifier U 2 outputs the rotation speed control signal S 24 with the zero voltage signal 0V. Alternatively, when the comparing signal S 23 (the voltage signal V in ) reaches a lower voltage value that is smaller than the second threshold value V L , the second output terminal of the operational amplifier U 2 outputs the rotation speed control signal S 24 with the positive saturation voltage signal +V sat . The Schmitt Trigger circuit is a circuit, which can eliminate the interference of noise of the input voltage and transfer the input voltage according to two threshold voltages V U and V L to form the square wave so as to output the two stage rotation speed control signal S 24 . The Schmitt Trigger circuit also outputs a quadratic square wave transferred from an unstable inputting voltage signal.

Referring to FIG. 3A , the rotation speed control circuit 213 further has a second resistor R 2 , which is electrically connected to the second output terminal of the operational amplifier U 2 of the Schmitt Trigger circuit for adjusting the voltage values of the first threshold value V U and the second threshold value V L and outputting the rotation speed control signal S 24 .

The driving control circuit 214 includes a driving chip (not shown), which receives the rotation speed control signal S 24 outputted by the rotation speed control circuit 213 for generating the driving signal S 25 and controlling the rotation speed of the motor 221 of the fan 22 in accordance with the driving signal S 25 . In the embodiment, the driving signal S 25 is a voltage signal.

The driving chip of the driving circuit 214 can be a microprocessor or any circuit or element with the same function.

In addition, the driving circuit 214 further includes a hall element (not shown), which is electrically connected to the driving chip so as to receive the voltage signal of the driving signal S 25 . The hall element then transfers the voltage signal into a current signal for driving the motor 221 of the fan 22 .

Moreover, each of the sensing signal S 21 , the reference voltage signal S 22 , the comparing signal S 23 , the rotation speed control signal S 24 and the driving signal S 25 can be a transmitted signal, like a voltage signal or a current signal.

Furthermore, the first resistor, the top resistor, the third resistor, the fourth resistor, the fifth resistor and the second resistor with reference to the drawings are described as the equivalent resistances. Actually, each of the resistors can be implemented by one or more resistors.

In the embodiment, the driving control device of the motor is the above-mentioned driving control device 21 . The function, structure and configuration of the driving control device are described hereinabove, so the detailed descriptions are omitted.

In summary, the fan system and the driving control device of the motor utilizes the comparing circuit and the rotation speed control circuit to achieve the two stages of the rotation speed control of the fan. Therefore, the chip with the complex operation function in the driving circuit of the related art is unnecessary so that the manufacturing cost of the driving control device can be decreased.

Although the present invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the present invention.