Patent Publication Number: US-2007115599-A1

Title: Fan system and method for protecting the same

Description:
RELATED APPLICATION  
      The present application is based on, and claims priority from, Taiwan Application Serial Number 94141109, filed Nov. 23, 2005, the disclosure of which is hereby incorporated by reference herein in its entirety.  
     FIELD OF THE INVENTION  
      The present invention relates to a fan system and a method for protecting the fan system, and more particularly to the fan system and the protecting method thereof that can force the protecting devices to be burned out or fail when the fan system is short-circuited.  
     BACKGROUND OF THE INVENTION  
      Referring to  FIG. 1 ,  FIG. 1  illustrates a conventional fan system  1  which is mainly constituted by a driving circuit  10 , a capacitor C 1 , several protecting devices  20  and several fans  30 . The driving circuit  10  is electrically connected to a power supply  2 , and has a switch device  11  and a driving device  12 . One end of the capacitor C 1  is electrically connected to the driving circuit  10 , and the other end of the capacitor C 1  is grounded. The protecting devices  20  are electrically connected with the fans  30  in series, respectively, and one end of each protecting device  20  is electrically connected in chorus with the capacitor C 1 .  
      In the driving circuit  10 , the switch device  11  is electrically connected between the power supply  2  and the capacitor C 1 , and the driving device  12  is electrically connected between the power supply  2  and the switch device  11 . The driving device  12  is used for controlling the on/off of the switch device  11 . When the switch device  11  is turned on, the power generated from the power supply  2  can be transmitted to the capacitor C 1  for storing charges, and provides voltage and current inputted to the protecting device  20  and the fans  30  after storing the charges. If the protecting devices  20  (such as fuses) could be appropriately burned out as soon as any one of the fans  30  is short-circuited (for example, the isolation skin of the fan&#39;s internal wire is peeled off and the conductor part thereof touches a metal part inside the fan system.), then the short-circuit event could be isolated for protecting the driving circuit  10  at the front end and the fans  30  at the back end. However, as a matter of fact, since the protecting devices  20  are passive devices, a current-detecting device (not shown) installed in the driving device  12  will keep on receiving the detection of the short-circuit event if the short-circuit event fails to burn out the protecting devices  20 , and thus the driving circuit  10  will be shut down due to failing to release the short-circuit event, and meanwhile, the switch device  11  will be turned off to cause all of the fans  30  at the back end to stop working so that the fan system  1  will fail to take charge of the load of heat dissipation due to insufficient heat dissipation, and eventually the whole system will be down or the overheat damage will be resulted in.  
     SUMMARY OF THE INVENTION  
      In view of the above issue, an aspect of the present invention is to provide a fan system and a method for protecting the fan system having an active-type protecting function, wherein the protecting devices are forced to be burned out or fail when a short-circuit event occurs, thereby avoiding misjudgment and false response.  
      Hence, in accordance the aforementioned aspect, the present invention discloses a fan system electrically connected to a power supply, and receives a power generated from the power supply. The fan system mainly includes a driving circuit, a protecting circuit, at least one protecting device and at least one fan. The driving circuit is electrically connected to the fan, and receives the power to drive the fan The protecting device is electrically connected with the fan, and the protecting device is electrically connected with the driving circuit. The protecting circuit is electrically connected between the protecting device and the driving circuit. When one fan is short-circuited, the protecting circuit outputs a current value larger than the current-limited value of the protecting device corresponding to the fans, thereby making the protecting device fail for stopping the short-circuited fan from obtaining the power.  
      In accordance the aforementioned aspect, the present invention provides a method for protecting a fan system, wherein the fan system mainly includes a driving circuit, a protecting circuit, at least one protecting device and at least one fan The driving circuit is used for driving the fans, and the protecting circuit is electrically connected between the driving circuit and the fan. The protecting device is electrically connected with the fan, and the protecting device is electrically connected with the protecting circuit. The method includes steps of providing the above-mentioned fan system; and outputting a current value from the protecting circuit according to a current-limited value of the protecting devices when one fan is short-circuited. The current value is larger than the current-limited value of the protecting device corresponding to the fan. At the results, the protecting device fails wh en the fan is short-ircuited, thus stopping an operation of the short-circuited fan.  
      For clearly explaining the objects, features and advantages of the present invention, a preferred embodiment with accompanying figures is described in detail hereinafter.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, 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 present invention;  
       FIG. 3  is a schematic diagram showing an implementation of the protecting circuit in the fan system of  FIG. 2 ;  
       FIG. 4  is a circuit diagram showing one implementation of the driving circuit in the fan system of  FIG. 2 ; and  
       FIG. 5  is a circuit diagram showing the other implementation of the driving circuit in the fan system of  FIG. 2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to  FIG. 2 ,  FIG. 2  is a schematic diagram of a fan system  3  according to a preferred embodiment of the present invention. The fan system  3  includes a driving circuit  40 , a protecting circuit  50 , at least two protecting devices  60  and at least two fans  70 . One end of the protecting circuit  40  is electrically connected to a power supply  2 , and the protecting circuit  40  is constituted by a switch device  41  and a driving device  42 . The protecting circuit  50  is electrically connected between the other end of the driving circuit  40  and the protecting devices  60 . The protecting devices  60  are electrically connected to the fans  70  in series respectively, and one end of each of the protecting devices  60  is connected in chorus with the protecting circuit  50 . As the results, each of the protecting devices and its corresponding fan  70  form an independent branched path.  
      The switch device  41  of the driving circuit  40  is electrically connected between the power supply  2  and the protecting circuit  50 , and the driving device  42  is electrically connected between the power supply  2  and the switch device  41  for controlling the on/off of the switch device  41 . When the switch device  41  is turned on, the power generated from the power supply  2  can be inputted to the protecting circuit  50 . The protecting circuit  50  has the function of storing power, and whenever any one branched path is short-circuited, the protecting circuit  50  may deliver a current value greater than the current-limited value for each of the protecting devices  60  (i.e. the maximum current value that the protecting device can be sustained.). Under normal operation, the protecting circuit  50  is used for storing the charges of the power generated from the power supply  2 , and after the charge-storing is completed, the protecting circuit  50  outputs current and voltage to the protecting devices  60  and the fans  70  for operating the fans  70 .  
      Referring to  FIG. 3 , in the present embodiment, the protecting circuit  50  is composed of several capacitors C 2  connected in parallel, and thus the protecting circuit  50  having a maximum capacitance value is formed. Accordingly, whenever any one branched path is short-circuited, the current outputted from the protecting circuit  50  may substantially flow only to the short-circuited branched path since tne short-circuited branched path has the smallest impedance than other branched paths. Additionally, for the large capacitance value generates large current, the protecting device  60  disposed on the short-circuited branched path can be forced to be burned out or become fail, thereby stopping the operation of the fan  70 .  
      It is noted that the interruption of the short-circuited branched path does not affect the other branched paths, so that the output current from the protecting circuit  50  may be continuously distributed on the other branched paths for operating the other fans  70 , thereby maintaining the heat-dissipation effect of the fan system  3 . As the results, this not only prevents the driving circuit  40  from being shut down due to abnormal current, but also further effectively maintains the smoothness of the overall operation for the fan system  3 .  
      Moreover, by using the feature of promptly interrupting the short-circuited branched path, the present invention has a response speed faster than the detection response of a current-detecting device (not shown) installed in the driving device  42 , thereby ensuring the driving device  42  not to be shut down by any one short-circuited branched path, wherein the shut-down of the driving device  42  would make the fans  70  at the back end fail to provide heat-dissipation function.  
      Referring to  FIG. 4 , in the fan system  3  of the present invention, the driving circuit  40  can be constructed by a combined software/hardware solution. The switch device  41  is a transistor Q 1 , and in particularly to a NMOSFET (N-channel Metal-Oxide Semiconductor Field Effect Transistor). The driving device  42  mainly includes an integrated circuit (IC) chip for receiving the power generated from the power supply  2  so as to control the on/off of the switch device  41 .  
      Referring to  FIG. 5 , in the fan system  3  of the present invention, the driving circuit  40  may be implemented as soft-start circuit, wherein the switch device  41  is transistor Q 2 , and in particularly to a PMOSFET (P-channel Metal-Oxide Semiconductor Field Effect Transistor). The driving device  42  can include several resistors R 1 -R 5 , several diodes D 1 -D 4 , a transistor Q 3 , a capacitor C 3  The driving device  42  receives the power generated from the power supply  2  to turn on the transistor Q 3 , i.e. the activation of the transistor Q 3  is controlled accordingly.  
      To sum up, based on a fan system and a method for protecting the fan system according to the present invention, the fan system can force the protecting device to be burned out or fail via the protecting circuit when any one of the branched paths is short-circuited; and the method for protecting the fan system includes using the protecting circuit that can output a current value greater than the current-limited value of each of the protecting devices, so that the corresponding protecting device can be burned out or fail as soon as any one of the branched paths is short-circuited, thereby preventing the short-circuited branched path from affecting the normal operation of the other branched paths, thus further assuring the heat-dissipation efficacy of the fan system.  
      As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrated of the present invention rather than limiting of the present invention. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures.