Patent Publication Number: US-2007116553-A1

Title: Fan system and temperature-sensing protecting device thereof

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 094141110 filed in Taiwan, Republic of China on Nov. 23, 2005, the entire contents of which are hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      The present invention relates to a fan system and a temperature-sensing protecting device thereof and, in particular, to a fan module with a temperature-sensing element and a temperature-sensing protecting device thereof.  
      2. Related Art  
      In general, most electronic systems have a fan system to ensure that the electronic systems can be kept at the normal working temperature such that the electronic system can operate normally. The fan system has predetermined operating specifications, such as the operating temperature and the likes.  
      As shown in  FIG. 1 , a conventional fan system  1  mainly includes a fan module  11  and a starting module  12 . The starting module  12  is used for enabling the fan module  11  so as to dissipating heat. However, when the operating temperature of the fan system  1  is too high or too low, the damage of the fan system  1  may occur. To solve this problem, the prior art usually adopts an analog starting control chip  13  to sense the operating temperature of the fan system  1 . If the sensed operating temperature is too high or too low, the fan system  1  will be automatically disabled for the protection purpose.  
      However, the analog starting control chip  13  has a high price, so that the overall manufacturing cost of the fan system  1  is too high. Besides, the analog starting control chip  13  cannot provide the function of soft-start.  
      Therefore, it is an important subject of the invention to provide a fan system and a temperature-sensing protecting device thereof to solve the above mentioned problem.  
     SUMMARY OF THE INVENTION  
      In view of the foregoing, the invention is to provide a fan system, which disables the fan system when the operating temperature detected by a temperature-sensing element is too high or too low, and a temperature-sensing protecting device thereof.  
      To achieve the above, a fan system of the invention includes a fan module, a starting module, a temperature-sensing element and a controlling module. In the invention, the starting module is electrically connected with the fan module for starting it. The temperature-sensing element generates a sensing signal in accordance with an ambient temperature. The controlling module receives the sensing signal for controlling the starting module. When the ambient temperature is higher than a first temperature or is lower than a second temperature, the controlling module controls the starting module to disable the fan module.  
      To achieve the above, the invention also discloses a temperature-sensing protecting device, which cooperates with a fan module. The temperature-sensing protecting device includes a starting module, a temperature-sensing element and a controlling module. The starting module is electrically connected with the fan module for starting it. The temperature-sensing element generates a sensing signal in accordance with an ambient temperature. The controlling module receives the sensing signal for controlling the starting module. When the ambient temperature is higher than a first temperature or is lower than a second temperature, the controlling module controls the starting module to disable the fan module.  
      As mentioned above, the fan system and temperature-sensing protecting device of the invention have a temperature-sensing element for sensing the operating temperature of a fan system. Then, when the operating temperature is too high or too low, the fan module is disabled for protecting it. Compared with the prior art, the fan system and temperature-sensing protecting device of the invention utilize the temperature-sensing element to detect the operating temperature for ensuring that the fan system can operate normally and replacing the analog starting control chip to reduce the overall manufacturing cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will become more fully understood from the detailed description given herein below illustration only, and thus is not limitative of the present invention, and wherein:  
       FIG. 1  is a schematic diagram of a conventional fan system;  
       FIG. 2  is a schematic diagram of a fan system according to a preferred embodiment of the invention; and  
       FIG. 3  is a circuit diagram of a fan system according to a preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 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 schematic illustration showing a fan system according to a preferred embodiment of the invention. The fan system  2  may be installed inside an electronic system (not shown) in order to dissipate heat.  
      The fan system  2  includes a fan module  21 , a starting module  22 , a controlling module  23  and a temperature-sensing element  24 . The fan module  21  has a fan. Of course, the fan module  21  may have a plurality of fans according to the heat dissipating requirement so as to enhance the heat dissipating effect.  
      In the fan system  2 , the starting module  22  is electrically connected with the fan module  21  so as to start it. The temperature-sensing element  24  produces a sensing signal V t  in accordance with an ambient temperature. The temperature-sensing element  24  may be a thermistor (thermal resistor). In this embodiment, the temperature-sensing element  24  is a negative temperature coefficient (NTC) thermistor. The ambient temperature may be the internal temperature of the electronic system, so that the temperature-sensing element  24  produces the sensing signal V t , e.g. a voltage value, in accordance with an ambient temperature. Based on the characteristic of the NTC thermistor, the resistance of the temperature-sensing element  24  decreases and the voltage of the sensing signal V t  decreases when the internal temperature of the electronic system increases. On the contrary, the resistance of the temperature-sensing element  24  increases and the voltage of the sensing signal V t  increases when the internal temperature of the electronic system decreases.  
      The controlling module  23  receives and controls the starting module  22  in accordance with the sensing signal V t . When the ambient temperature is higher than a first temperature or lower than a second temperature, the controlling module  23  controls the starting module  22  to disable the fan module  21  for preventing the fan system  21  from being damaged caused by the improper operation under abnormal operating temperature. In this embodiment, the first temperature and the second temperature are determined in accordance with the operating specifications of the fan system  2 . The first temperature is the upper limit operating temperature of the fan system  2  such as 70° C., and the second temperature is the lower limit operating temperature of the fan system  2  such as −40° C.  
      With reference to  FIG. 3 , the controlling module  23  includes a first control unit  231  and a second control unit  232 . In this embodiment, the first control unit  231  comprises a first switch element Q 1  and a first comparator element U 1 . The second control unit  232  comprises a second switch element Q 2  and a second comparator element U 2 .  
      Each of the first switch element Q 1  and the second switch element Q 2  may be a transistor or any other electronic element with the switch function. In this embodiment, the first the first switch element Q 1  and the second switch element Q 2  are both NMOS transistors.  
      Regarding to the first control unit  231 , a drain D of the first switch element Q 1  is electrically connected with the starting module  22  for controlling the starting module  22 , and a source S of the first switch element Q 1  is grounded.  
      The first comparator element U 1  includes a first input terminal input 1  a second input terminal input 2 , and an output terminal output. In this embodiment, the first input terminal input 1  is a noninverting input terminal and the second input terminal input 2  is an inverting input terminal.  
      The first input terminal input 1  receives a first reference signal V ref1 , which is produced from a voltage-dividing circuit composed of at least two resistors. The specifications of the resistors can be chosen according to the requirement of user for adjusting the first reference signal V ref1 . In this case, the first reference signal V ref1  is used to determine the upper limit operating temperature of the fan system  2 . The second input terminal input 2  receives the sensing signal V t . The output terminal output is electrically connected with a gate G of the first switch element Q 1  for controlling the first switch element Q 1 . To make the invention more comprehensive, the following description assumes that the voltage gain value of the first comparator element U 1  is equal to 1. When the sensing signal V t  is lower than the first reference signal V ref1 , the output terminal output delivers a positive voltage to start the first switch element Q 1  so as to control the starting module  22  to disable the fan module  21 .  
      In addition, the second input terminal inputs and the output terminal output of the first comparator element U 1  are electrically connected with a resistor R 1 , so that the first comparator element U 1  may have a precise temperature transition characteristic. For example, the first control unit  231  is supposed to control the starting module  22  to disable the fan module  21  when the first temperature reaches 70° C. However, the starting module  22  practically disables the fan module  21  when the first temperature is 72° C. due to the characteristic of the electronic element, which causes an error originally. For preventing the above mentioned problem, the resistor R 1  is set between the second input terminal input 2  and the output terminal output of the first comparator element U 1  for compensating the feedback voltage value. Therefore, the first comparator element U 1  can precisely control the starting module  22  to disable the fan module  21  when the temperature reaches 70° C. Accordingly, the precise temperature transition characteristic can be achieved.  
      Regarding to the second control unit  232 , a drain D of the second switch element Q 2  is electrically connected with the starting module  22  for controlling it, and a source S of the second switch element Q 2  is grounded  
      The second comparator element U 2  includes a first input terminal input 1 , a second input terminal input 2 , and an output terminal output. In this embodiment, the first input terminal input 1  is a noninverting input terminal, and the second input terminal input 2  is an inverting input terminal.  
      The first input terminal input 1  receives the sensing signal V t  and the second input terminal input 2  receives a second reference signal V ref2  producing from the voltage-dividing circuit composed of at least two resists. The specifications of resistors can be chosen according to the requirement of user for adjusting the second reference signal V ref2 . In this case, the second reference signal V ref2  is used to determine the lower limit operating temperature of the fan system  2 . The output terminal output is electrically connected with a gate G of the second switch element Q 2  for controlling the second switch element Q 2 . To make the invention more comprehensive, the following description assumes that the voltage gain value of the second comparator element U 2  is equal to 1. When the sensing signal V t  is higher than the second reference signal V ref2 , the output terminal output delivers a positive voltage to start the second switch element Q 2  so as to control the starting module  22  to disable the fan module  21 . In addition, a resistor R 2  is set between input terminal input 1  and the output terminal output of the second comparator element U 2 , and the operation of the resistor R 2  is the same as that of the above-mentioned resistor R 1 . Therefore, the second comparator element U 2  may have precise temperature transition characteristic.  
      As mentioned above, when the sensing signal V t  is lower than the first reference signal V ref1 , or higher than the second reference signal V ref2 , both the output terminals output of the first comparator element U 1  and the second comparator element U 2  deliver a positive voltage signal in order to control the starting module  22  to disable the fan module  21 .  
      In this embodiment, the starting module  22  includes a third switch element Q 3 , a fourth switch element Q 4 , at least a capacitor C, at least a resistor R 3 , and a plurality of diodes D 1  and D 2 . Each of the third switch element Q 3  and the fourth switch element Q 4  is a transistor or any other electronic element with the switch function. In this embodiment, the third switch element Q 3  is a PMOS transistor, and the fourth switch element Q 4  is an NMOS transistor.  
      A source S of the third switch element Q 3  is electrically connected with the diodes D 1  and D 2 . A drain D of the third switch element Q 3  is electrically connected with the fan system  21  for starting the fan system  21 . A gate G of the third switch element Q 3  is electrically connected with a drain D of the fourth switch element Q 4 . A terminal of the capacitor C is electrically connected with the source S of the third switch element Q 3 . The resistor R 3  is electrically connected with another terminal of the capacitor C. In addition, each of the diodes D 1  and D 2  may be a Schottky diode for avoiding the reverse current. A gate G of the fourth switch element Q 4  is electrically connected with the drain D of the first switch element Q 1  and the drain D of the second switch element Q 2 .  
      The operation principle of the fan system  2  will be described in the following. When the internal temperature of the electronic system is between the first temperature and the second temperature (the temperature range of normal operation), the sensing signal V t  of the temperature-sensing element  24  is higher than the first reference signal V ref1  and lower than the second reference signal V ref2 . In this case, the first switch element Q 1  and the second switch element Q 2  will be turned off and the fourth switch element Q 4  will be turned on.  
      Then, the capacitor C starts to charge. When the voltage value of the capacitor C reaches the starting voltage of the third switch element Q 3 , the third switch element Q 3  is turned on to enable the fan module  21  for dissipating the heat. To be noted, the charge circuit of the capacitor C and the resistor R 3  enables the current flowing through the fan module  21  to increase at a slow rate such that the effect of soft starting can be achieved.  
      When the internal temperature of the electronic system is higher than the first temperature, the sensing signal V t  is lower than the first reference signal V ref1  to turn on the first switch element Q 1 . Accordingly, the fourth switch element Q 4  and the third switch element Q 3  are turned off to disable the fan module  21  in order to achieve the protection and efficiency.  
      Similarly, when the internal temperature of the electronic system is lower than the second temperature, the sensing signal V t  is higher than the second reference signal V ref2  to turn on the second switch element Q 2 . Accordingly, the fourth switch element Q 4  and the third switch element Q 3  will be turned off to disable the fan module  21  in order to achieve the protection and efficiency. As mentioned above, the temperature-sensing element  24  of the fan system  2  senses that whether the internal temperature is higher than the upper limit operating temperature or lower than the lower limit operating temperature. If so, the fan system  2  will compulsorily disable the fan module  21  for preventing it from damage.  
      The invention also discloses a temperature-sensing protecting device, which cooperates with a fan module. The temperature-sensing protecting device includes a starting module, a temperature-sensing element and a controlling module. In this embodiment, the starting module, temperature-sensing element and controlling module of the temperature-sensing protecting device have the same constructions and functions as those of the previously mentioned starting module  22 , temperature-sensing element  24  and controlling module  23 , so the detailed descriptions thereof will be omitted for concise purpose.  
      As mentioned above, the fan system and temperature-sensing protecting device of the invention have a temperature-sensing element for sensing the operating temperature of a fan system. Then, when the operating temperature is too high or too low, the fan module is disabled for protecting it. Compared with the prior art, the fan system and temperature-sensing protecting device of the invention utilize the temperature-sensing element to detect the operating temperature for ensuring that the fan system can operate normally and replacing the analog starting control chip to reduce the overall manufacturing cost.  
      Although the 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 invention.