Abstract:
In an electric freezing refrigerator, when a light emitting diode of back light unit deteriorate due to an external impact or an internal defect or a port terminal of a microcomputer applying power to the light emitting diode is damaged, the back lighting of electric freezing refrigerator can be stably performed by turning another back light unit of the electric freezing refrigerator on.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to an LCD back light circuit of an electric refrigerator and, more particularly, to an LCD back light circuit of an electric refrigerator that is capable of stably performing a back lighting even if there is a trouble in a back light circuit caused due to an external impact or an internal defect of a light emitting diode.  
         BACKGROUND ART  
         [0002]    [0002]FIG. 1 is a drawing illustrating an LCD back light circuit of an electric refrigerator in accordance with a conventional art.  
           [0003]    As shown in FIG. 1, the LCD back light circuit includes a microcomputer  100  for controlling an ON/OFF operation of a circuit and a back light unit  110  connected between a port terminal of a microcomputer and a ground and turned on/off under the control of the microcomputer.  
           [0004]    The back light unit  110  includes a light emitting diode group  110 - 1  in which a plurality of light emitting diodes are serially connected in a forward direction, and a resistance R 1  serially connected to the light emitting diode group  110 - 1  and distributing a power source voltage.  
           [0005]    There are provided a plurality of light emitting diode groups which are connected in parallel between the port terminal and the ground.  
           [0006]    The operation of the LCD back light circuit of an electric refrigerator in accordance with the conventional art will now be described in detail.  
           [0007]    When power is applied to the back light unit  110  through the port terminal of the microcomputer  100 , a current of the power source is equally distributed to a plurality of nodes and turns on the light emitting diode groups  110 - 1 ,  110 - 2 , . . . ,  110 -M, and flows to the ground through the resistances R 1 , R 2 , . . . , RM. A voltage of the power source is distributed at a certain rate by the light emitting diode groups  110 - 1 ,  110 - 2 , . . . ,  110 -M and the resistances R 1 , R 2 , . . . , RM.  
           [0008]    However, the LCD back light circuit of an electric refrigerator in accordance with the conventional art has the following problem.  
           [0009]    That is, if the port terminal connected to the microcomputer  100  is short, the entire back light unit  110  is turned off.  
           [0010]    In addition, if one of light emitting diodes of the LCD back light circuit is defective, the normal light emitting diodes serially connected to the defective light emitting diode are simultaneously turned off, causing a problem that luminance of the LCD is not uniform.  
         DETAILED DESCRIPTION OF THE INVENTION  
         [0011]    Therefore, an object of the present invention is to provide a circuit in which a plurality of port terminals connected to a microcomputer are provided so that, even if one light emitting diode is defective or even if one port terminal connected to a microcomputer becomes short, the light emitting diodes connected to other port terminals can be maintained in an ON state, thereby performing a back light function.  
           [0012]    Another object of the present invention is to provide a circuit for performing a back light function in which even if one of serially connected light emitting diodes is defective, light emitting diodes connected to other port terminals are turned on, thereby performing a back light function.  
           [0013]    In order to achieve the above objects, there is provided an LCD back light circuit of an electric refrigerator including: a first back light unit operated according to a first control signal; a second back light unit operated according to a second control signal; a detector for generating a power-on signal if no light is detected from the first back light unit, and a microcomputer for generating the first control signal if the power-on signal is not inputted thereto, or generating a second control signal if the power-on signal is inputted thereto. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a drawing illustrating an LCD back light circuit of an electric refrigerator in accordance with a conventional art; and  
         [0015]    [0015]FIG. 2 is a drawing illustrating an LCD back light circuit of an electric refrigerator in accordance with a preferred embodiment of the present invention. 
     
    
     MODE FOR CARRYING OUT THE PREFERRED EMBODIMENTS  
       [0016]    An LCD back light circuit of an electric refrigerator and its driving method in accordance with the present invention will now be described in detail with reference to FIG. 2.  
         [0017]    [0017]FIG. 2 is a drawing illustrating an LCD back light circuit of an electric refrigerator in accordance with a preferred embodiment of the present invention.  
         [0018]    As shown in FIG. 2, the LCD back light circuit includes a microcomputer  200  having a plurality of ports and controlling an ON/OFF operation of the circuit, a first back light unit  210  connected to a first port terminal of the microcomputer and a ground and turned on/off according to a control signal of the microcomputer, a second back light unit  220  connected between a second port terminal of the microcomputer  200  and the ground and turned on/off according to a control signal of the microcomputer, and a detector  230  for detecting whether a light is emitted from the first back light.  
         [0019]    In the first back light unit  210 , a light emitting diode groups  210 - 1 ,  210 - 2 , . . . ,  210 -M, in which a plurality of light emitting diodes are serially connected, are constructed to be connected in parallel, and in the second back light unit  220 , light emitting diode groups  220 - 1 ,  220 - 2 , . . . ,  220 -M, in which a plurality of light emitting diodes are serially connected, are constructed to be connected in parallel.  
         [0020]    That is, the light emitting diode groups  220 - 1 ,  220 - 2 , . . . ,  220 -M of the second back light unit  220  are installed at odd numbers of the light emitting diode groups  210 - 1 ,  210 - 2 , . . . ,  210 -M of the first back light unit  210 .  
         [0021]    The operation of the LCD back light circuit of an electric refrigerator in accordance with a preferred embodiment of the present invention will now be described.  
         [0022]    When power is applied to the LCD back light circuit through the first port terminal of the microcomputer  200 , a current of the power source is equally distributed to the plurality of nodes to turn the first back light unit  210  and flow to the ground.  
         [0023]    However, if the first port becomes short, the first back light unit  210  connected to the first port terminal is turned off. In addition, if one of the first back light units  210  becomes short, a light emitting diode group connected to the light emitting diode which has become short is turned since current fails to flow thereto. Then, the LCD back lighting function can&#39;t work properly.  
         [0024]    In this respect, however, the detector  230  recognizes that the first back light unit  210  is not working properly and transmits a power-on signal, to the microcomputer  200 . Upon receiving the power-on signal, the microcomputer  200  cuts off the power supply current connected to the first port terminal and drive the second back light unit  220  connected to the second port terminal, thereby constantly maintaining the luminance of the LCD back lighting.  
       INDUSTRIAL APPLICABILITY  
       [0025]    As so far described, the LCD back light circuit of an electric refrigerator of the present invention has the following advantages.  
         [0026]    That is, if a light emitting diode is defective due to an external impact or an internal defect of the light emitting diode, or if the port terminal of the microcomputer which applies power to the light emitting diode, the light emitting diodes connected to other port terminal of the microcomputer, so that the LCD back light of the electric refrigerator can be stably driven.  
         [0027]    In addition, the present invention can be variably changed and implemented in a variety of product groups, not limiting to the electric refrigerator.