Patent Publication Number: US-2012043895-A1

Title: Led backlight module

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a LED backlight module, and more particularly to a LED backlight module capable of preventing the whole LED backlight module scrapped due to a few LED failure, and therefore, to raise the manufacture yield of the LED backlight module. 
     2. Description of Prior Art 
     Nowadays, a liquid crystal display (LCD) is mainly manufactured by producing a backlight module first constructed by a backlight source, a plastic frame and a diffusion plate, and then assembling the backlight module with a liquid crystal front panel and a front frame to construct a LCD module for manufacturing a final product. Generally, the backlight module which the backlight sources of the liquid crystal display utilizes Cold Cathode Fluorescent Lamps (CCFL) is now substantially replaced by a LED backlight module because the properties of the low power consumption and mercury free of the LED backlight module. Consequently, the CCFL backlight module will be history ultimately. The LED backlight module will certainly replace the CCFL backlight modules overall. 
     The assembly method of the LED backlight module is generally utilize a plurality of LEDs, and numbers of LEDs are electrically connected in series as a lighting string set. According to the size of the LCD, a plurality of lighting string sets is arranged averagely. Each of the lighting string sets is driven with the DC voltage generated by the converter to drive the LEDs for lighting and replacing the CCFL as being the backlight source of the backlight module of the LCD. 
     Please refer to  FIG. 1  and  FIG. 2 .  FIG. 1  shows a diagram of the arrangement of the LEDs and the circuit in a LED backlight module according to prior art.  FIG. 2  shows a diagram of that the illumination of the area  202  becomes darkened due to one LED failure in the LED backlight module  200  according to prior art. A side light type LED backlight module with three lighting string sets is illustrated. However, the number of the lighting string sets can be decided according to the size of the LCD. As shown in  FIG. 1  and  FIG. 2 , the LED backlight module comprises three lighting string sets. Each of LEDs is indicated by the resistance thereof. One lighting string set comprises LEDs  10 ,  20 ,  30  in series. One lighting string set comprises LEDs  40 ,  50 ,  60  in series. One lighting string set comprises LEDs  70 ,  80 ,  90  in series. All the LEDs  10 ,  20 ,  30 ,  40 ,  50 ,  60 ,  70 ,  80 ,  90  are driven for lighting with the voltage and current generated by the drive circuit  100 . 
     As shown in  FIG. 2 , the lighting string set comprising the LEDs  10 ,  20 ,  30  is used for lighting the display area corresponding to the area  202  of the LED backlight module  200 ; the lighting string set comprising the LEDs  40 ,  50 ,  60  is used for lighting the display area corresponding to the area  204  of the LED backlight module  200 ; the lighting string set comprising the LEDs  70 ,  80 ,  90  is used for lighting the display area corresponding to the area  206  of the LED backlight module  200 . Because the LEDs in the same lighting string set are electrically connected in series, therefore, the whole LEDs  10 ,  20 ,  30  of the lighting string set will turn out when the LED  20  fails and the LED backlight module  200  becomes darkened in the area  202  as shown in  FIG. 2 . Similarly, in a case that the LED  60  fails, the LEDs  40 ,  50 ,  60  will turn out and the LED backlight module  200  becomes darkened in the area  204 ; in a case that the LED  90  fails, the LEDs  70 ,  80 ,  90  will turn out and the LED backlight module  200  becomes darkened in the area  206 . Same problem also occurs in the direct type LED backlight module. Accordingly, failure of any LEDs will lead to an obvious brightness drop in a mass area of the display. An adverse effect is induced to the user obviously and the whole backlight module has to be scrapped and replaced. 
     Consequently, there is a need to provide a LED backlight module to solve the existing issues of prior art. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a LED backlight module for preventing the whole LED backlight module scrapped due to a few LED failure, and therefore, to raise the manufacture yield of the LED backlight module and effectively decrease the cost. 
     For realizing the aforesaid objective of the present invention, the present invention provides a LED backlight module used for a liquid crystal display apparatus, comprising a LED drive circuit, generating at least one driving voltage needed for the LED backlight module; a plurality of location areas, corresponding to a plurality of display areas of the liquid crystal display apparatus, and each of the plurality of location areas comprises a plurality of sub location areas corresponding to a portion of the display areas, respectively; a first lighting string set, comprising a plurality of first LEDs, located in the sub location areas of the location areas, respectively, and the plurality of first LEDs is electrically connected to the LED drive circuit in series and driven by the at least one driving voltage for lighting, wherein the sub location areas for respectively locating the plurality of first LEDs are not adjacent; a second lighting string set, comprising a plurality of second LEDs, located in the sub location areas of the location areas, respectively, and the plurality of second LEDs is electrically connected to the LED drive circuit in series and driven by the at least one driving voltage for lighting, wherein the sub location areas for respectively locating the plurality of second LEDs are not adjacent; and a third lighting string set, comprising a plurality of third LEDs, located in the sub location areas of the location areas, respectively, and the plurality of third LEDs is electrically connected to the LED drive circuit in series and driven by the at least one driving voltage for lighting, wherein the sub location areas for respectively locating the plurality of third LEDs are not adjacent. 
     In the LED backlight module of the present invention, the plurality of location areas comprises a plurality of sub location areas respectively. The plurality of LEDs of each of the lighting string sets is located in sub location areas of the different location areas, respectively, wherein the sub location areas for respectively locating the plurality of LEDs of each of the lighting string sets are not adjacent. 
     The LED backlight module of the present invention can comprise a LED drive circuit, generating at least one driving voltage for driving the plurality of LEDs for lighting. Alternatively, the LED drive circuit can generate respective driving voltages for the lighting string sets to drive the lighting string sets for lighting respectively as being a backlight source of the LED backlight module. 
     The LED backlight module can be a direct light type LED backlight module. 
     The LED backlight module can be a side light type LED backlight module. 
     The LED can generate respective driving voltages for the first lighting string set, the second lighting string set and the third lighting string set, to drive the first lighting string set, the second lighting string set and the third lighting string set for lighting, respectively. 
     The LED backlight module provided by the present invention can comprise a LED drive circuit, generating at least one driving voltage for driving the plurality of LEDs for lighting. Alternatively, the LED drive circuit can generate respective driving voltages for the lighting string sets, to drive the lighting string sets for lighting respectively as being a backlight source of the LED backlight module. 
     The LED backlight module provided by the present invention can be a direct light type LED backlight module or a side light type LED backlight module. 
     According to the present invention, the whole LED backlight module can be prevented to be scrapped due to a few LED failure, and therefore, to raise the manufacture yield of the LED backlight module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a diagram of the arrangement of the LEDs and the circuit in a LED backlight module according to prior art; 
         FIG. 2  shows a diagram of that the illumination of the display area becomes darkened due to one LED failure in the LED backlight module according to prior art; 
         FIG. 3  shows a diagram of the arrangement of the LEDs and the circuit in a LED backlight module according to the present invention; 
         FIG. 4  shows a diagram of that the illumination of the display area becomes darkened due to one LED failure in the LED backlight module according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     For a better understanding the aforementioned content of the present invention, preferable embodiments are illustrated in accordance with the attached figures for further explanation: 
     Please refer to  FIG. 3  and  FIG. 4 .  FIG. 3  shows a diagram of the arrangement of the LEDs and the circuit in a LED backlight module according to the present invention.  FIG. 4  shows a diagram of that the illumination of the display area becomes darkened due to one LED failure in the LED backlight module according to the present invention. 
     In this embodiment of the present invention, a side light type LED backlight module with three lighting string sets is illustrated. However, the number of the lighting string sets can be decided according to the size of the LCD in a practical situation. The aforementioned situation is merely for the convenient explanation for the present invention but not the limitation thereto. Please refer to  FIG. 3  and  FIG. 4 . The LED backlight module  200  comprises a LED drive circuit  100 , a first location area  202 , a second location area  204 , a third location area  206  and a first lighting string set, a second lighting string set, a third lighting string set as being the backlight source of the LED backlight module  200 . 
     The LED drive circuit  100  is used for generating at least one driving voltage for the LEDs for lighting. The first location area  202  corresponds to the first display area of the liquid crystal display apparatus using the LED backlight module  200  of the present invention. The second location area  204  corresponds to the second display area of the liquid crystal display apparatus using the LED backlight module  200  of the present invention. The third location area  206  corresponds to the third display area of the liquid crystal display apparatus using the LED backlight module  200  of the present invention. 
     In  FIG. 3  and  FIG. 4 , each of LEDs is indicated by the standard resistance symbol in the circuit design diagram. As shown in figures, the black resistance symbol represents a normal LED. The unpainted resistance symbol represents a failed LED. The resistance symbols marked with X represents that the LEDs have become darkened. The first lighting string set comprises first LEDs  10 ,  40 ,  70  in series; the second lighting string set comprises second LEDs  20 ,  50 ,  80  in series; the third lighting string set comprises third LEDs  30 ,  60 ,  90  in series. As shown in  FIG. 4 , the first LED  10  of the first lighting string set is located in the sub location area  202 - 1  of the first location area  202 , so as to illuminate a portion of the first corresponding display area. The first LED  40  of the first lighting string set is located in the sub location area  204 - 1  of the second location area  204 , so as to illuminate a portion of the corresponding second display area. The first LED  70  of the first lighting string set is located in the sub location area  206 - 1  of the third location area  206 , so as to illuminate a portion of the corresponding third display area. The first LEDs  10 ,  40 ,  70  are electrically connected to the LED drive circuit  100  in series. The present invention utilizes the driving voltage generated by the LED drive circuit  100  to drive the first LEDs  10 ,  40 ,  70  for lighting, so as to illuminate a portion of the corresponding first display area, a portion of the corresponding second display area and a portion of the corresponding third display area, respectively. 
     As shown in  FIG. 4 , the second LED  20  of the second lighting string set is located in the sub location area  202 - 2  of the first location area  202 , so as to illuminate a portion of the corresponding first display area. The second LED  50  of the second lighting string set is located in the sub location area  204 - 2  of the second location area  204 , so as to illuminate a portion of the corresponding second display area. The second LED  80  of the second lighting string set is located in the sub location area  206 - 2  of the third location area  206 , so as to illuminate a portion of the corresponding third display area. The first LEDs  20 ,  50 ,  80  are electrically connected to the LED drive circuit  100  in series. The present invention utilizes the driving voltage generated by the LED drive circuit  100  to drive the second LEDs  20 ,  50 ,  80  for lighting, so as to illuminate a portion of the corresponding first display area, a portion of the corresponding second display area and a portion of the corresponding third display area, respectively. 
     As shown in  FIG. 4 , the third LED  30  of the third lighting string set is located in the sub location area  202 - 3  of the first location area  202 , so as to illuminate a portion of the corresponding first display area. The third LED  60  of the second lighting string set is located in the sub location area  204 - 3  of the second location area  204 , so as to illuminate a portion of the corresponding second display area. The third LED  90  of the third lighting string set is located in the sub location area  206 - 3  of the third location area  206 , so as to illuminate a portion of the corresponding third display area. The third LEDs  30 ,  60 ,  90  are electrically connected to the LED drive circuit  100  in series. The present invention utilizes the driving voltage generated by the LED drive circuit  100  to drive the third LEDs  30 ,  60 ,  90  for lighting, so as to illuminate a portion of the corresponding first display area, a portion of the corresponding second display area and a portion of the corresponding third display area, respectively. 
     Meanwhile, as shown in  FIG. 4 , in a case that the LED  40  fails, the first LEDs  10 ,  70  also fail at the same time because the first LEDs  10 ,  40 ,  70  are electrically connected in series. Therefore, the sub location areas  202 - 1 ,  204 - 1 ,  206 - 1  become darkened and leads to that the illuminations of the portions of the corresponding first, second, third display areas become darkened. The LEDs  10 ,  40 ,  70  in series are dispersed and located in different sub location areas  202 - 1 ,  204 - 1 ,  206 - 1  in the present invention. Therefore, when one of the LEDs fails, this merely results in that the whole brightness of the LED backlight module  200  is reduced uniformly, so as to prevent the problem of the obvious brightness drop in a mass area of the display. The above-mentioned problem caused in prior art obviously gives an adverse effect to the user. Hereby, the situation of scrapping and replacing the whole backlight module can be prevented. 
     Furthermore, in the aforesaid embodiment of the present invention, a side light type LED backlight module with three lighting string sets is illustrated. Yet, the present invention also can be applied for a direct light type LED backlight module. Moreover, the LED driving circuit  100  can generate respective driving voltages for the first lighting string set, the second lighting string set and the third lighting string set. Hereby, the first LEDs  10 ,  40 ,  70  of the first lighting string set, the second LEDs  20 ,  50 ,  80  of the second lighting string set and the third LEDs  30 ,  60 ,  90  of the third lighting string set can be driven for lighting respectively. Besides, in  FIG. 4  of the present invention, an arrangement of the sub location areas in the location areas is in sequence for illustration to explain the concept of the present invention, but not the limited thereto. Only if the obvious brightness drop in a mass area of the display caused in prior art can be prevented, other arrangements also can be used for replacing the arrangement that each sub location area in the respective location areas corresponds one lighting string set in the present invention. As long as the respective sub location areas for locating the plurality of the first LEDs, the plurality of the second LEDs, or the plurality of the third LEDs are not adjacent and the obvious brightness drop in a mass area of the display does not occur. 
     In a word, The LED backlight module provide by the present invention can minimize the effect of the few failed LEDs on the whole LED backlight module, and the adverse vision effect caused by the failed LEDs can be controlled to be reduced in an acceptable range for the user. Accordingly, the issue of scrapping and replacing the whole backlight module due to the few LED failure can be prevented. The manufacture yield of the LED backlight module can be raised and the cost can be effectively decreased. 
     As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrative rather than limiting of the present invention. It is intended that they cover various modifications and similar arrangements be 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 structure.