Patent Publication Number: US-2007110558-A1

Title: Fan system and temperature-sensing module

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 094139638 filed in Taiwan, Republic of China on Nov. 11, 2005, the entire contents of which are hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      The invention relates to a fan system and a temperature-sensing module and, in particular, to a fan system and a temperature-sensing module, which can start a plurality of fan modules according to the temperature difference.  
      2. Related Art  
      Generally speaking, a large electronic system is always equipped with a fan system to ensure that the electronic system can be kept at the normal working temperature such that the electronic system can operate normally.  
       FIG. 1  is a schematic illustration showing a conventional fan system  1 . The fan system  1  receives an input voltage V in  from exterior to serve as an operation voltage. The fan system  1  mainly has a plurality of fan modules  11   a  to  11   i c and a plurality of starting modules  12   a  to  12   c . After the starting modules  12   a  to  12   c  receive the input voltage V in , the fan modules  11   a  to  11   c  are started simultaneously to dissipate the heat. However, when the fan modules  11   a  to  11   c  are started simultaneously, an extremely large start-up current and inrush current are generated at the moment of starting. Thus, the electronic system or the fan system  1  may crash or have unpredictable malfunction, or even the electronic system or the fan system  1  may be damaged.  
      In view of the above-mentioned problems, the prior art adopts an analog starting control chip  13  for starting the fan modules  11   a  to  11   c  sequentially, or a software module to control the starting sequence of the fan modules  11   a  to  11   c . Thus, the prior art provides a protection mechanism for respectively starting the fan modules  11   a  to  11   c  at different time instants so as to avoid the malfunction caused when the fan modules  11   a  to  11   c  are simultaneously started. However, the analog starting control chip  13  has a high price, and the software module has a complicated architecture. Thus, the overall manufacturing cost of the conventional fan system  1  is too high. In addition, the analog starting control chip  13  only can delay the starting time of each of the fan modules  11   a  to  11   c  and cannot provide the function of soft-start.  
      Thus, it is an important subject of the invention to provide a fan system and a temperature-sensing module to overcome the above-mentioned problems.  
     SUMMARY OF THE INVENTION  
      In view of the foregoing, the invention is to provide a fan system and a temperature-sensing module for starting a plurality of fan modules at different time based on the temperature difference so as to avoid the malfunction caused when the fan modules are started simultaneously and to reduce the power consumption.  
      To achieve the above, a fan system of the invention is for receiving an input voltage from exterior. The fan system includes a first fan module, a second fan module, a first starting module, a second starting module, a temperature-sensing element and a first controlling module. The first starting module receives the input voltage and starts the first fan module. The second starting module, which is electrically connected to the second fan module, receives the input voltage. The temperature-sensing element produces a sensing signal in accordance with an ambient temperature. The first controlling module controls the second starting module in accordance with the sensing signal so as to start the second fan module.  
      To achieve the above, the invention also discloses a temperature-sensing module for receiving an input voltage from exterior and cooperating with a fan module. The temperature-sensing module includes a starting unit, a temperature-sensing element and a controlling unit. The starting unit is electrically connected with the fan module and receives the input voltage. The temperature-sensing element produces a sensing signal in accordance with an ambient temperature. The controlling unit controls the starting unit to start the fan module in accordance with the sensing signal.  
      As mentioned above, the fan system and the temperature-sensing module according to the invention include the temperature-sensing element for producing the sensing signal. Then, the controlling module can individually start the fan modules at different temperatures in accordance with the sensing signal so as to avoid the malfunction caused by the extremely large start-up current and inrush current, which are generated by instantaneously starting the fan modules. Compared with the prior art, the fan system and temperature-sensing module of the invention utilize the temperature-sensing element to sense the operating temperature and then correspondingly start sufficient fan modules. Therefore, the fan modules are started in a time-sharing manner to ensure that the fan system can operate normally, reduce the power consumption, and replace 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 illustration showing a conventional fan system;  
       FIG. 2  is a schematic illustration showing a fan system according to a preferred embodiment of the invention;  
       FIG. 3  is a circuit diagram showing a fan system according to the preferred embodiment of the invention; and  
       FIG. 4  is a schematic illustration showing a temperature-sensing module according to the 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  2  according to a preferred embodiment of the invention. As shown in  FIG. 2 , the fan system  2  receives an input voltage  91  from exterior to serve as an operation voltage. In the embodiment, the fan system  2  may be applied to an electronic system (not shown) in order to dissipate heat, and the input voltage  91  may be supplied from the electronic system.  
      The fan system  2  includes a plurality of fan modules  21   a  to  21   c , a plurality of starting modules  22   a  to  22   c , a plurality of controlling modules  23   a  and  23   b , and a temperature-sensing element  24 .  
      Each of the fan modules  21   a  to  21   c  has a fan. Of course, the user may dispose a plurality of fans in each of the fan modules  21   a  to  21   c  according to the heat dissipating requirement so as to enhance the heat dissipating effect.  
      The starting modules  22   a  to  22   c  receive the input voltage  91  and are electrically connected with the fan modules  21   a  to  21   c , respectively.  
      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 the internal temperature. Based on the characteristic of the NTC thermistor in this embodiment, 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 voltage of the sensing signal V t  increases when the internal temperature of the electronic system decreases.  
      The controlling modules  23   a  and  23   b  are electrically connected with the starting modules  22   b  and  22   c , respectively. In the embodiment, the starting module  22   a  receives the input voltage  91  so as to start the fan module  21   a , and the controlling modules  23   a  and  23   b  control the starting modules  22   b  and  22   c  according to the sensing voltage V t  so as to start the fan modules  21   b  and  21   c .  
      As shown in  FIG. 3 , each of the starting modules  22   a  to  22   c  includes a plurality of diodes D 1  and D 2 , a plurality of resistors R 1  and R 2 , two switch elements Q 1  and Q 2  and a capacitor C. 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 switch element Q 1  is a PMOS transistor, and the second switch element Q 2  is an NMOS transistor.  
      In addition, the diodes D 1  and D 2  are connected in parallel. Each of the diodes D 1  and D 2  has a first terminal for receiving the input voltage  91 . In this embodiment, each of the diodes D 1  and D 2  may be a Schottky diode for avoiding the reverse current. One terminal of the resistor R 1  is electrically connected with a second terminal of each of the diodes D 1  and D 2 .  
      A source S of the first switch element Q 1  is electrically connected with the second terminals of the diodes D 1  and D 2 , and a drain D of the first switch element Q 1  is electrically connected with corresponding one of the fan modules  21   a  to  21   c . A gate G of the first switch element Q 1  is electrically connected with a drain D of the second switch element Q 2 .  
      The drain D of the second switch element Q 2  is electrically connected with a second terminal of the resistor R 1 . A source S of the second switch element Q 2  is grounded. A first terminal of the capacitor C is electrically connected with the source S of the first switch element Q 1  and a first terminal of the resistor R 1 . A first terminal of the resistor R 2  is electrically connected with a second terminal of the capacitor C, and a second terminal of the resistor R 2  is grounded.  
      The controlling modules  23   a  and  23   b  include a comparator U 1  and a comparator U 2 , respectively. Each of the comparators U 1  and U 2  has a first input terminal input 1 , a second input terminal input 2  and an output terminal output. The second input terminal input 2  and the output terminal output are electrically connected with each other through a resistor R to provide the comparator U 1  or U 2  a precise temperature transition characteristic. The resistor R is set between the second input terminal input 2  and the output terminal output of the comparator U 1  for compensating the feedback voltage value. Therefore, the comparator U 1  can precisely control the starting module  22   b  to start the fan module  21   b . Accordingly, the precise temperature transition characteristic can be achieved. Similarly, in the controlling module  23   b , the resistor R is set between the second input terminal input 2  and the output terminal output of the comparator U 2  for compensating the feedback voltage value. Therefore, the comparator U 2  can precisely control the starting module  22   c  to start the fan module  21   c , so that the precise temperature transition characteristic can be achieved. 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.  
      Regarding to the controlling module  23   a , the first input terminal input 1  of the comparator U 1  receives a first reference signal V ref1 , and the second input terminal input 2  receives the sensing signal V t . The output terminal output is electrically connected with the gate G of the second switch element Q 2  of the starting module  22   b  for controlling the second switch element Q 2  of the starting module  22   b . In the embodiment, when the sensing signal V t  is lower than the first reference signal V ref1 , the output terminal output delivers a positive voltage signal to start the second switch element Q 2  of the starting module  22   b . Accordingly, the fan module  21   b  is started.  
      Regarding to the controlling module  23   b , the first input terminal input 1  of the comparator U 2  receives a second reference signal V ref2 , and the second input terminal input 2  receives the sensing signal V t . The output terminal output is electrically connected with the gate G of the second switch element Q 2  of the starting module  22   c  for controlling the second switch element Q 2  of the starting module  22   c . In the embodiment, when the sensing signal V t  is lower than the second reference signal V ref2 , the output terminal output delivers a positive voltage signal to start the second switch element Q 2  of the starting module  22   c . Accordingly, if the second reference signal V ref2  is lower than the first reference signal V ref1 , the fan module  22   b  is started when the internal temperature of the electronic system rises.  
      The operation principle of the fan system  2  will be described in the following. Once the fan system  2  is connected with the electronic system, it receives the input voltage  91 . In this case, the diodes D 1  and D 2  of the starting module  22   a  receive the input voltage  91  to start the switch element Q 2  and to charge the capacitor C. When the voltage of the capacitor C reaches the starting voltage of the switch element Q 1 , the switch element Q 1  is started to enable the fan module  21   a . To be noted, the capacitor C and the resistor R 2  form a charging circuitry that enables the current flowing through the fan module  21   a  to increase at a slow rate such that the effect of soft starting can be achieved.  
      Since the electronic system is just started, the internal temperature thereof is not raised too much. At this moment, the sensing signal V t  is not less than the first reference signal V ref1  and the second reference V ref2 , so the fan modules  21   b  and  21   c  are not started yet. After the electronic system has operated for a period of time, the internal temperature thereof begins to rise so that the voltage of the sensing signal V t  decreases. If the sensing signal V t  is less than the first reference signal V ref1 , the controlling module  23   a  will control the starting module  22   b  to start the fan module  21   b.    
      If the internal temperature of the electronic system keeps rising, which leads to the sensing voltage V t  less than the second reference signal V ref2 , the controlling module  23   b  will control the starting module  22   c  to start the fan module  21   c . As a result, the fan modules  21   a  to  21   c  can be started in accordance with the different temperatures so as to avoid the malfunction caused by the extremely large start-up current and inrush current. Thus, the heat dissipation requirement and the power consumption issue can be achieved.  
      In addition, the fan system  2  of the embodiment provides the backup heat-dissipating device in advance, so that the backup heat dissipating device, such as the fan module, can be enabled to increase the heat dissipation efficiency as the load of the electronic system increases, which generates more heat. In this manner, the electronic system can operate normally.  
      For example, assuming that the electronic system needs only one fan module  22   a  for normal operation, the preset two fan modules  22   b  and  22   c  can be used as the backup fan modules in the fan system  2  of the embodiment. Therefore, when the load of the electronic system increases, which leads to the higher internal temperature in the electronic system, the temperature-sensing element  24  will sense the temperature variation for starting the fan modules  22   b  and  22   c . In this manner, the heat-dissipating efficiency can be enhanced for maintaining the normal operation of the electronic system.  
      With reference to  FIG. 4 , the invention further discloses a temperature-sensing module  3 , which receives an input voltage  91  from exterior and cooperates with a fan module  31 . The temperature-sensing module  3  includes a starting unit  32 , a controlling unit  33 , and a temperature-sensing element  34 . In this embodiment, the fan module  31 , the starting unit  32 , the controlling unit  33 , and the temperature-sensing element  34  have the same constructions and functions as those of the above mentioned fan module  21   b , the starting unit  22   b , the controlling unit  23   a , and the temperature-sensing element  24 , so the detailed descriptions thereof will be omitted for concise purpose.  
      In summary, the fan system and the temperature-sensing module according to the invention include the temperature-sensing element for producing the sensing signal. Then, the controlling modules can individually start the fan modules at different temperatures in accordance with the sensing signal so as to avoid the malfunction caused by the extremely large start-up current and inrush current, which are generated by instantaneously starting the fan modules. Compared with the prior art, the fan system and temperature-sensing module of the invention utilize the temperature-sensing element to sense the operating temperature and then correspondingly start sufficient fan modules. Therefore, the fan modules are started in a time-sharing manner to ensure that the fan system can operate normally, reduce the power consumption, and replace the analog starting control chip to reduce the overall manufacturing cost. In addition, the fan system of the invention has the advantage of preparing the backup heat-dissipating devices in advance, which can enhance the flexibility in usage.  
      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.