Abstract:
An electrostatic preventing device for light emitting diodes (LED), operative to backlight a liquid crystal display (LCD) device is disclosed. The device includes RGB assemblies installed on a flexible circuit board, and an electrostatic preventing circuit separately installed on the flexible circuit board. The device is adapted to protect RGB LED chips inside each RGB package for backlight, mounted in the RGB assemblies, from static electricity.

Description:
RELATED APPLICATION 
       [0001]    The present disclosure claims priority to Korean Application No. 10-2006-0031140, filed on Apr. 5, 2006, which is herein expressly incorporated by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to an electrostatic discharge preventing device for light emitting diodes (LED) for backlighting a liquid crystal display (LCD). In particular, the invention relates to an electrostatic discharge preventing device in which one electrostatic preventing circuit is provided at one printed circuit board on which LEDs are mounted. 
         [0004]    2. Description of the Related Art 
         [0005]    An LCD device may display an image by using an optical anisotropy characteristic of a liquid crystal. When light is irradiated onto liquid crystal having a polarized characteristic according to an applied voltage, the liquid crystal is aligned. The LCD device displays an image by controlling an amount of light passing through the liquid crystal according to an aligned state of the liquid crystal. 
         [0006]    The LCD device comprises a liquid crystal panel containing liquid crystal between two substrates, and a driving circuit provided at a peripheral portion of the liquid crystal panel for applying a signal to the liquid crystal panel and controlling the signal. Because the liquid crystal panel is not a spontaneous display device, an additional optical source such as a backlight is required. 
         [0007]    As a backlight for an LCD TV, a fluorescent lamp may be used. The fluorescent lamp may comprise a direct type and a light guide plate type. Also, a white LED may be used as a backlight for a small LCD device applied to a personal digital assistant (PDA), a portable phone, a notebook, or other mobile devices. 
         [0008]    When the LEDs are fabricated, static electricity is generated to be introduced into the LEDs and may damage them. Accordingly, an electrostatic preventing apparatus for protecting LEDs from static electricity is required. 
         [0009]      FIG. 1  shows an electrostatic preventing apparatus For LEDs for backlighting in accordance with the related art. As shown, one LED chip  11  is installed on LED package  10  to mute static electricity introduced into the LED chip  11  by a zener diode  12 , thereby protecting the LED chip from static electricity. 
         [0010]    Recently, an RGB LED chip for backlighting may be applied not only to a PDA, a portable phone, or a notebook, but also to a large display device such as an LCD TV. The RGB LED chip can reproduce more colors than the related art CCFL backlight, and can reproduce colors that are obtained with difficulty by a cathode ray tube (CRT), a plasma display panel (PDP), or a surface conduction electron emitter (SED) display. 
         [0011]      FIG. 2  shows an inner structure of an RGB package. As shown, RGB LED chips  21 ,  22 , and  23  are formed in one RGB package  20 . A general backlight for an LCD device supplies white light to a liquid crystal panel under a turned-ON state. However, in a Field Sequential Color (FSC) LCD device, the RGB LED chips  21 ,  22 , and  23  are sequentially driven with a period to supply white light to an liquid crystal panel. 
         [0012]    When an RGB package for an FSC LCD is fabricated, RGB LED chips have to be installed in a limited space and may cause a difficulty in obtaining a space for installing an electrostatic preventing circuit. Furthermore, when the RGB LED chips are mounted on a surface of a flexible printed circuit board (FPCB), static electricity is generated thus to damage the RGB LED chips and thereby to degrade yield. 
       SUMMARY 
       [0013]    Therefore, an object of the present invention is to provide an electrostatic preventing apparatus for light emitting diodes (LED) for backlighting, the apparatus capable of protecting RGB LED chips inside each RGB assembly from static electricity by additionally installing one electrostatic preventing circuit on at one printed circuit board. 
         [0014]    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 electrostatic preventing apparatus for light emitting diodes for backlighting, comprising: a plurality of RGB assemblies installed on a flexible printed circuit board (FPCB); and an electrostatic preventing circuit additionally installed on the FPCB for protecting RGB LED chips inside each RGB package for backlighting mounted in the RGB assembly from static electricity. 
         [0015]    Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views. 
           [0017]      FIG. 1  shows an electrostatic preventing device for light emitting diodes for backlighting in accordance with the related art. 
           [0018]      FIG. 2  is an inner structure of an RGB package. 
           [0019]      FIG. 3  illustrates a flexible printed circuit board (FPCB) having an electrostatic preventing apparatus for LEDs for backlighting. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]      FIG. 3  illustrates a flexible printed circuit board (FPCB) having an electrostatic preventing device for LEDs for backlighting. 
         [0021]    As shown, an electrostatic preventing device for LEDs for backlighting comprises a plurality of RGB assemblies  31 ,  32 , and  33  mounted on a surface of an FPCB  30  and an electrostatic preventing circuit  34  separately formed from the RFB assemblies  31 ,  32 , and  33  on the FPCB  30 , for protecting RGB LED chips (not shown) inside each RGB packages  31 A to  31 D,  32 A to  32 D, and  33 A to  33 D for backlighting mounted at the RGB assemblies  31 ,  32 , and  33  from static electricity. 
         [0022]    The RGB assemblies  31 ,  32 , and  33  are provided with a plurality of RGB packages  31 A to  31 D,  32 A to  32 D, and  33 A to  33 D, respectively. The RGB LED chips are respectively mounted in the RGB packages  31 A to  31 D,  32 A to  32 D, and  33 A to  33 D. 
         [0023]    The electrostatic preventing circuit  34  is provided with a plurality of zener diodes  34 A to  34 C that protect the RGB LED chips respectively mounted at the RGB packages  31 A to  31 D,  32 A to  32 D, and  33 A to  33 D from static electricity. 
         [0024]    And, an anode of each zener diode  34 A to  34 C is connected to the RGB LED chip, and a cathode thereof is connected to a common terminal (COM). 
         [0025]    An operation of the electrostatic preventing apparatus for RGB LEDs for backlighting will be explained. 
         [0026]    The plurality of RGB assemblies  31 ,  32 , and  33  are mounted on a surface of the FPCB  30 . The plurality of RGB packages  31 A to  31 D,  32 A to  32 D, and  33 A to  33 D are respectively formed in each of the RGB assemblies  31 ,  32 , and  33 . 
         [0027]    At least one of the RGB assemblies  31 ,  32 , and  33  is used as a backlight for a terminal such as a personal digital assistant (PDA), a portable phone, a notebook, or other mobile device. 
         [0028]    As shown in  FIG. 2 , RGB LED chips  21 ,  22 , and  23  are respectively formed at the RGB packages  31 A to  31 D,  32 A to  32 D, and  33 A to  33 D. The RGB LED chips  21 ,  22 , and  23  respectively formed at the RGB packages  31 A to  31 D,  32 A to  32 D, and  33 A to  33 D are connected to a common terminal (COM) through zener diodes  34 A to  34 C of the electrostatic preventing circuit  34 . 
         [0029]    Static electricity introduced into one of the RGB LED chips  21 ,  22 , and  23  formed at the RGB packages  31 A to  31 D,  32 A to  32 D, and  33 A to  33 D is moderated by a corresponding zener diode of the zener diodes  34 A to  34 C of the electrostatic preventing circuit  34 . Accordingly, the corresponding LED chip is protected from static electricity. 
         [0030]    For instance, when static electricity is introduced into the red LED chip  21  of the RGB package  31 A of the RGB assembly  31 , the static electricity is moderated by the common terminal COM through the zener diode  34 C of the electrostatic preventing circuit  34 . Accordingly, the red LED chip  21  is protected from static electricity. 
         [0031]    When static electricity is introduced into the red LED chip  21  of the RGB assembly  31 , the green LED chip  22  of the RGB assembly  32 , and the blue LED chip  23  of the RGB assembly  33 , the static electricity is moderated by the common terminal COM through the zener diodes  34 C,  34 B, and  34 A of the electrostatic preventing circuit  34 . Accordingly, the red LED chip  21 , the green LED chip  22 , and the blue LED chip  23  are protected from static electricity. 
         [0032]    When a plurality of RGB assemblies are mounted in the printed circuit board, an electrostatic preventing circuit is installed in the printed circuit board thus to protect the RGB LED chips mounted in the RGB assemblies from static electricity. Accordingly, the RGB LED chips can be protected from static electricity without having each-electrostatic preventing circuit. 
         [0033]    Because each RGB package need not be provided with the electrostatic preventing circuit, spaces for installing the RGB LED chips inside the RGB packages may be obtained. 
         [0034]    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 equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.