Patent Publication Number: US-2005118029-A1

Title: Apparatus and method for detecting fault of cooling fan

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a cooling fan and, more particularly, to an apparatus and method for detecting a fault of a cooling fan.  
      2. Description of the Conventional Art  
      A cooling fan is a device for releasing heat generated when electronic components such as semiconductor operate. In general, a heat sink such as an aluminum plate is attached to a heating device to externally release heat generated from the heating device to thereby obtain cooling effect, and in this case, if it is difficult to obtain sufficient cooling effect only with the heat sink, a cooling fan is additionally installed as an auxiliary unit to obtain desired cooling effect.  
      Although the cooling fan increases heat sinking of the heating device, if it is stopped due to introduction of dust or a foreign material, a failure or abnormal power, a thermal runaway phenomenon may occur to cause damage of a device owing to rise in a temperature. Thus, a device for sensing such a fault of the cooling fan and informing a user about it is required.  
      A schematic construction of a cooling fan having a function of detecting a fault in accordance with a conventional art will now be described with reference to  FIG. 1 .  
       FIG. 1  shows the construction of a cooling fan having a function of detecting a fault in accordance with a conventional art.  
      As shown in  FIG. 1 , the conventional cooling fan having a function of detecting a fault includes a positive and negative power input terminal  10  for supplying DC power to a cooling fan; a cooling fan  20  for sinking heat generated from semiconductor by power and outputting a fault detection signal; and a controller  30  for informing a user of the fault of the cooling fan  20  based on the outputted fault detection signal.  
      With such a function of detecting a fault constructed as described above, the cooling fan is advantageous in that the cooling fan itself determines the fault and outputs a fault detection signal based on the determining result, and thus, it is easy to mount the cooling fan and its construction circuit is simple.  
      However, since the cooling fan having the function of detecting a fault is different in its construction and levels and directions of output signals according to manufacturers, it cannot be applied to various products, and in addition, because it is high-priced, it cannot be well matched to a low-cost product.  
      Thus, in order to solve such a problem, a fault detection circuit for detecting whether a cooling fan is improperly operated is constructed separately to form a low-priced product, which will now be described with reference to  FIG. 2 .  
       FIG. 2  shows the construction of an apparatus for detecting a fault of a cooling fan in accordance with a conventional art.  
      As shown in  FIG. 2 , the apparatus for detecting a fault of a cooling fan includes: a positive (+) and negative (−) power input terminal  10  for supplying DC power to a cooling fan; a cooling fan  20  for sinking heat generated from a semiconductor by the supplied power; a trigger terminal  40  driven according to a voltage applied to the negative (−) power input terminal of the cooling fan  20 ; an electronic switch  50  switched by the trigger terminal  40 ; and a controller  30  for informing a user about the fault of the cooling fan  20  based on an output voltage according to switching.  
      An operation principle of the apparatus for detecting a fault of the cooling fan in accordance with the conventional art will now be described in detail.  
      First, when the cooling fan  20  operates normally, the conventional apparatus for detecting a fault of the cooling fan prevents the trigger terminal  40  from being driven according to the voltage applied to the negative (−) power input terminal  12  of the cooling fan  20 , so that the electronic switch  50  is turned off and a voltage value ‘0’ is outputted to the outer terminal (V OUT ). Accordingly, the controller  30  determines that the cooling fan  20  is properly operated according to the outputted voltage value ‘0’.  
      Meanwhile, when the cooling fan  20  stops, the conventional apparatus for detecting a fault of the cooling fan drives the trigger terminal  40  according to the voltage applied to the negative (−) power input terminal  12  of the cooling fan  20 , so that the electronic switch  30  is turned on and the same voltage value as V CC  is outputted to the output terminal (V OUT ). Accordingly, the controller  30  determines that the cooling fan  20  is not properly operated according to the outputted voltage value V CC  and informs the user accordingly.  
      As mentioned above, by controlling the trigger terminal and the electronic switch according to the voltage applied to the negative (−) power input terminal, the conventional apparatus for detecting a fault of a cooling fan is advantageous in that it can be implemented at a low cost and it can always have the same construction regardless of a manufacturer.  
      However, since the trigger terminal and the electronic switch are controlled according to the voltage applied to the negative (−) power input terminal of the cooling fan, an internal parameter of the trigger terminal should be changed according to manufacturers of the cooling fan.  
     SUMMARY OF THE INVENTION  
      Therefore, an object of the present invention is to provide an apparatus and method for detecting a fault of a cooling fan capable of determining whether a cooling fan is improperly operated based on a result of comparing a current value detected from a negative (−) input terminal of a cooling fan with a pre-set upper threshold value and a lower threshold value, whereby the cooling fan can be applied to all products manufactured by various manufacturers.  
      To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an apparatus for detecting a fault of a cooling fan including: an electronic switch connected to a negative (−) power input terminal of a cooling fan and turning on/off the cooling fan; a current detector connected to the electronic switch and detecting a current value of the cooling fan; an analog filter for filtering the detected current value; and a controller for converting the filtered current value into a digital current value and determining whether the cooling fan is improperly operated based on the converted digital current value and a pre-set upper threshold value and lower threshold value.  
      To achieve the above object, there is also provided a method for detecting a fault of a cooling fan including: detecting a current value of a cooling fan and converting it into a digital current value; comparing the converted digital current value with an upper threshold value; comparing the digital current value with a lower threshold value when the converted digital current value is smaller than the upper threshold value; and normally driving the cooling fan when the converted digital current value is greater than the lower threshold value.  
      The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.  
      In the drawings:  
       FIG. 1  shows the construction of a cooling fan having a function of detecting a fault in accordance with a conventional art;  
       FIG. 2  shows the construction of an apparatus for detecting a fault of a cooling fan in accordance with the conventional art;  
       FIG. 3  shows the construction of an apparatus for detecting a fault of a cooling fan in accordance with the present invention; and  
       FIG. 4  is a flow chart of a method for detecting a fault of a cooling fan in accordance with the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      An apparatus and method for detecting a fault of a cooling fan capable of determining whether a cooling fan is improperly operated based on a result of comparing a current value detected from a negative (−) input terminal of a cooling fan with a pre-set upper threshold value and a lower threshold value, whereby the cooling fan can be applied to all products manufactured by various manufacturers, in accordance with a preferred embodiment of the present invention will now be described with reference to the accompanying drawings.  
       FIG. 3  shows the construction of an apparatus for detecting a fault of a cooling fan in accordance with the present invention.  
      As shown in  FIG. 3 , the apparatus for detecting a fault of a cooling fan includes: a positive (+) and negative (−) power input terminal  10  for supplying power to a cooling fan; a cooling fan  20  for sinking heat generated from a semiconductor by the supplied power; a freewheeling diode  40  for annihilating field current of the cooling fan  20 ; an electronic switch  50  connected to the negative (−) power input terminal and switching on/off the cooling fan  20 ; a current detector  60  connected to the electronic switch  50  and detecting a current value applied to the cooling fan  20 ; an analog filter  70  for filtering the detected current value; and a controller  30  for converting the filtered current value into a digital current value and determining whether the cooling fan  20  is improperly operated on the basis of the converted digital current value and a pre-set upper threshold value and lower threshold value.  
      The controller  30  includes an A/D converter  31  for converting the filtered current value into a digital current value; and a memory  32  for storing the pre-set upper threshold value and lower threshold value.  
      The apparatus for detecting a fault of the cooling fan in accordance with the present invention will now be described in detail.  
      First, when the electronic switch  50  is turned on, the cooling fan  20  is driven upon receiving a DC current through the positive (+) power input terminal  11  and the negative (−) power input terminal  12 , and when the electronic switch  50  is turned off, the field current of the cooling fan  20  is annihilated by the freewheeling diode  50  connected between the positive (+) power input terminal  11  and the negative (−) power input terminal  12 .  
      The current detector  60  is connected to the negative (−) power input terminal  12 , detects a current value applied to the cooling fan  20  and outputs the detected current value to the analog filter  70 .  
      The analog filter  70  filters the received current value and then outputs a filtered current value.  
      The A/D converter  31  converts the filtered current value into a digital current value and outputs a converted current signal. Then, the controller  30  determines whether the cooling fan  20  is improperly operated based on the digital current value.  
      The process of determining whether the cooling fan is improperly operated in accordance with the present invention will now be described with reference to  FIG. 4 .  
       FIG. 4  is a flow chart of a method for detecting a fault of the cooling fan in accordance with the present invention.  
      As shown in  FIG. 4 , the method for detecting a fault of the cooling fan includes: detecting a current value applied to a cooling fan and converting it into a digital current value (step S 41 ); comparing the converted digital current value with an upper threshold value (step S 42 ); comparing the digital current value with a lower threshold value when the converted digital current value is smaller than the upper threshold value (step S 43 ); and normally driving the cooling fan when the converted digital current value is greater than the lower threshold value (step S 44 ). Herein, when the converted digital current value is greater than the upper threshold value or smaller than the lower threshold value, a user is informed about the fault of the cooling fan (step S 45 ).  
      The method for detecting a fault of the cooling fan will be described in detail as follows.  
      First, the A/D converter  31  converts the current value that has been filtered by the analog filter  70  into a digital current value and outputs the converted digital current value (step S 41 ). Then, the controller  30  determines whether the cooling fan  20  is improperly operated or not based on the digital current value and the upper and lower threshold values.  
      The upper and lower threshold values are previously set and stored in the memory  32 . The upper threshold value means a threshold value of a current detected when the cooling fan  20  is not properly operated, and the lower threshold value means a threshold value of a current detected when the cooling fan  20  is not connected.  
      The controller  30  compares the converted digital current value and the upper threshold value (step S 42 ). Namely, when the converted digital current value is smaller than the upper threshold value, the controller  30  compares the digital current value with the lower threshold value, and when the digital current value is greater than the upper threshold value, the controller determines that the cooling fan  20  is not properly operated and informs the user accordingly (step S 45 ).  
      Thereafter, the controller  30  compares the digital current value with the lower threshold value (step S 43 ). When the digital current value is greater than the lower threshold value, the controller  30  determines that the cooing fan  20  does not have a problem and normally drives the cooling fan  20 . Meanwhile, when the converted digital current value is smaller than the lower threshold value, the controller  30  determines that the cooling fan  20  is not connected and informs the user that the cooling fan  20  is not properly operated (step S 45 ).  
      As a result, the controller  30  recognizes the fault, stopping and connection failure of the cooling fan  20  when the converted digital current value is greater than the upper threshold value or smaller than the lower threshold value, and informs the user accordingly so that the user can take a suitable measure for a normal operation of the cooling fan  20 .  
      As so far described, the apparatus and method for detecting a fault of a cooling fan in accordance with the present invention has the following advantages.  
      That is, for example, a current value detected from a negative (−) power input terminal of a cooling fan is compared with pre-set upper and lower threshold value, based on which a fault of the cooling fan is determined. Thus, a change of a parameter indicating the fault of the cooling fan is flexible, the cooling fan can be applied to every product produced by various manufacturers.  
      As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims.