Abstract:
A light emitting package is disclosed that can generate a white light while controlling Red, Green and Blue light emitting diodes (“LEDs”) simultaneously. In the light emitting package, a plurality of LEDs are connected in series to one another. The plurality of LEDs are responsive to one driving voltage. Currents flowing through the plurality of LEDs are controlled by a current adjuster. Consequently, the plurality of LEDs are driven by the currents different from one another in amount.

Description:
This application claims the benefit of Korean Patent Application Nos. 10-2005-0095880 and 10-2006-0036995, each filed on Oct. 12, 2005 and Apr. 25, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND 
     DESCRIPTION OF THE RELATED ART 
     A liquid crystal display (“LCD”) device displays an image by controlling the light transmittance of a liquid crystal. Such an LCD includes a backlight unit for providing surface light to a liquid crystal panel that can control the light transmittance for each pixel region. To provide uniform surface light to the liquid crystal panel, the backlight unit includes a light source for emitting light and a plurality of light path control sheets for distributing the emitted light uniformly. 
     A cold cathode fluorescent lamp (“CCFL”) is widely used as the light source for the backlight unit. The CCFL enables electrons to be emitted from the electrode by high voltage supplied between two electrodes facing each other. The emitted electrons excite mercury injected into the lamp to produce ultraviolet light. The ultraviolet light stimulates phosphors coated on the inside of the lamp and visible light is emitted from the phosphors. A related art backlight unit using the CCFL is illustrated in  FIG. 1 . 
     Referring to  FIG. 1 , the related art backlight unit includes a plurality of CCFLs  1  for emitting light, a cover bottom member  3  for fixing and supporting the CCFLs  1 , and optical sheets  5   a ,  5   b  and  5   c  disposed between the CCFLs  1  and a liquid crystal panel (not shown). The optical sheets  5   a ,  5   b  and  5   c  prevent light from being projected on the surface of the liquid crystal panel in a form of the CCFLs  1  and provide uniform brightness entirely. To increase a light scattering effect, the prism sheets  5   b  and  5   b  and the diffusion sheet  5   a  are disposed between the CCFLs  1  and the liquid crystal panel. A reflection plate  7  on the inner surface of the cover bottom member  3  reflects the light from the CCFLs  1  toward the liquid crystal panel, thereby improving the light utilization. Electrode interconnections  9   a  and  9   b  are provided at both electrodes (not shown) of each CCFL  1 , respectively. An external voltage for driving the lamp is supplied through the electrode interconnections  9   a  and  9   b.    
     Such a backlight unit serves as a light source for an image display. Specifically, the light from the CCFLs passes through the optical sheets  5   a ,  5   b  and  5   c  to produce a white light with high brightness. The liquid crystal panel disposed on the backlight unit adjusts the light transmittance by changing the arrangement of liquid crystal molecules injected thereinto. At the same time, a desired full-color image is displayed by mixing three primary colors (red (R), green (G), and blue (B)) using color filters (not shown). In other words, a desired image can be displayed by passing the light (white light) emitted from the backlight unit through the R, G and B color filters. 
     The backlight unit implements uniform brightness and high luminance by using the CCFLs  1 , the optical sheets  5   a ,  5   b  and  5   c , and the reflection plate  7  together. However, it may not be suitable for large-sized LCDs. Also, a high voltage must be supplied to an anode of the CCFL  1  so as to emit electrons, and the light efficiency is reduced by increased heat. Further, it is problematic that mercury is toxic and seriously harmful to the environment. 
     A backlight unit using a light emitting diode (LED) instead of the CCFL has certain advantages. As illustrated in  FIG. 2 , the related art backlight unit includes a light source  11  with a plurality of R, G and B LEDs, a cover bottom member  13  for fixing and supporting the light source  11 , and optical sheets  15   a ,  15   b  and  15   c  disposed between the light source  11  and a liquid crystal panel (not shown). The optical sheets  15   a ,  15   b  and  15   c  prevent light from being projected on the surface of the liquid crystal panel in the form of the light source  11  and provide uniform brightness entirely. To increase a light scattering effect, the prism sheets  15   b  and  15   b  and the diffusion sheet  15   a  are disposed between the light source  11  and the liquid crystal panel. A reflection plate  17  is disposed in the inner surface of the cover bottom member  13  to reflect the light from the light source  11  to the liquid crystal panel, thereby improving the light utilization. The light source  11  includes a plurality of light emitting packages  14  arranged in a line as illustrated in  FIG. 3 . Each of the light emitting packages  14  includes one R LED  12   a , two G LEDs  12   b , and one B LED  2   c.    
     Generally, the R, G and B LEDs  12   a ,  12   b  and  12   c  of the light emitting package  14  are individually controlled because they have device characteristics different from one another. For example, different voltages may be supplied to the respective LEDs  12   a ,  12   b  and  12   c  so as to make the same current flow through the respective LEDs  12   a ,  12   b  and  12   c . Even if the same current flows due to the device characteristics of the respective LEDs  12   a ,  12   b  and  12   c , light having different brightness is generated. Therefore, in order to generate a white light having a necessary white balance, the currents flowing through the R, G and B LEDs  12   a ,  12   b  and  12   c  are adjusted so that the R, G and B LEDs  12   a ,  12   b  and  12   c  are individually controlled. 
     As illustrated in  FIG. 4 , the R, G and B LEDs  12   a ,  12   b  and  12   c  from a related art device are individually driven. The R LED  12   a  is supplied with a voltage (Vin-R) from an R LED voltage generator  20   a  and generates light whose intensity corresponds to the current flowing through the R LED  12   a . The G LED  12   b  is supplied with a voltage (Vin-G) from a G LED voltage generator  20   b  and generates light whose intensity corresponds to the current flowing through the G LED  12   b . The B LED  12   c  is supplied with a voltage (Vin-B) from a B LED voltage generator  20   c  and generates light whose intensity corresponds to the current flowing through the B LED  12   c . The light generated from the R, G and B LEDs  12   a ,  12   b  and  12   c  are incident onto the liquid crystal panel (not shown) to display a desired image. 
     In such a backlight unit, the R, G and B LEDs  12   a ,  12   b  and  12   c  must be individually driven so as to generate a white light with a required white balance. For this purpose, the R, G and B LED voltage generators  20   a ,  20   b  and  20   c  corresponding to the R, G and B LEDs  12   a ,  12   b  and  12   c  are individually provided. 
     Consequently, the driver circuit of the light emitting packages  14  becomes complex and the manufacturing cost increases. 
     SUMMARY 
     The present embodiments are directed to a light emitting package, a backlight unit and a liquid crystal display device implementing the light emitting package and backlight unit. 
     In one embodiment, a light emitting package includes a plurality of light emitting diodes (LEDs) connected in series and a current adjuster coupled with the plurality of LEDs. 
     In another embodiment, a backlight unit includes a plurality of circuit boards and a plurality of light emitting packages disposed at the respective circuit boards. The light emitting packages include a plurality of light emitting diodes connected in series and a current adjuster coupled with the plurality of LEDs. 
     In a further embodiment, a liquid crystal display device includes a backlight unit having a plurality of circuit boards. The device further includes a plurality of light emitting packages disposed at the respective circuit boards. The light emitting packages include a plurality of light emitting diodes connected in series and include a current adjuster coupled with the plurality of LEDs. The liquid crystal display device further includes a liquid crystal panel for displaying an image by adjusting a transmittance of a white light generated from the backlight unit. 
     In a further embodiment, a light emitting package includes a voltage generator for generating an input voltage. In addition, the light emitting package includes a plurality of light emitting diodes (“LEDs”) coupled with the voltage generator and a current adjuster coupled with the plurality of LEDs. The LEDs are arranged in series and receive the input voltage and the current adjuster controls currents flowing through the plurality of LEDs. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       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 application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  is an exploded perspective view of a related art black light unit with a CCFL; 
         FIG. 2  is an exploded perspective view of a related art backlight unit with R, G and B LEDs; 
         FIG. 3  is a view of the related art light source illustrated in  FIG. 2 ; 
         FIG. 4  is a circuit diagram of a driver for driving the related art LED emitting package illustrated in  FIG. 3 ; 
         FIG. 5  is a view of an LCD according to an embodiment; 
         FIG. 6  is a circuit diagram of a light emitting package with R, G and B LEDs; 
         FIG. 7  is a circuit diagram of a light emitting package according to an embodiment; 
         FIG. 8  is a detailed circuit diagram of the light emitting package according to the embodiment, for explaining an embodiment of the current adjuster shown in  FIG. 7 ; 
         FIG. 9  is a detailed circuit diagram of the light emitting package according to the embodiment, for explaining an another embodiment of the current adjuster shown in  FIG. 7 ; 
         FIG. 10  is a detailed circuit diagram of the light emitting package according to the embodiment, for explaining a further embodiment of the current adjuster shown in  FIG. 7 ; and 
         FIG. 11  is a circuit diagram of a light emitting package according to a further embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 5  is a view of a Liquid Crystal Disaply (“LCD”) according to the present invention. Referring to  FIG. 5 , the LCD according to one embodiment includes a liquid crystal panel  102  in which a plurality of gate lines GL 0 , GL 1  to GLn and a plurality of data lines DL 1 , DL 2  to DLm are arranged and on which an image is displayed, a gate driver  104  and a data driver  106  for driving the liquid crystal panel  102 , and a timing controller  108  for controlling the gate driver  104  and the data driver  106 , and a backlight unit  110  for generating light to be projected to the liquid crystal panel  102 . 
     In the liquid crystal panel  102 , the gate lines GL 0  to GLn and the data lines DL 1  to DLm are arranged, and thin film transistors (“TFTs”) acting as switching elements are disposed at the defined regions thereby. The TFTs have gate electrodes electrically connected to the gate lines GL 0  to GLn, source electrodes electrically connected to the data lines DL 1  to DLm, and drain electrodes electrically connected to pixel electrodes (not shown). 
     The TFTs are turned on when scan signals (specifically, gate high voltages (“VGH”)) are supplied to the gate lines GL 0  to GLn, and the TFTs are turned off when gate low voltages (“VGL”) are supplied. Also, when the TFTs are turned on, data voltages on the data lines pass through the source and drain electrodes of the TFTs and are supplied to the pixel electrodes. The data voltages are retained at the pixel electrodes until the gate high voltages (VGH) are supplied at a next frame. 
     The gate driver  104  sequentially supplies the scan signals (specifically, the gate high voltages (“VGH”)) to the gate lines GL 0  to GLn in response to gate control signals generated from the timing controller  108 . 
     The data driver  106  supplies the data voltages to the data lines DL 1  to DLm in response to data control signals generated from the timing controller  108 . Also, the data driver  106  converts R, G and B data signals from the timing controller  108  into analog data voltages. 
     The timing controller  108  generates the gate control signals for controlling the gate driver  104  and the data control signals for controlling the data driver  106  by using vertical/horizontal sync signals (“Vsync”/“Hsync”), a data enable signal DE, and a clock signal, which are supplied from an external system (none of which are shown). Also, the timing controller  108  arrays R, G and B data by one line and then supplies them to the data driver  106 . The R, G and B data is supplied from the system in units of frames. 
     The backlight unit  110  generates light to be irradiated onto the liquid crystal panel  102 . The generation of the light is controlled by the control signals generated from the timing controller  108 . The backlight unit  110  includes a plurality of optical sheets, a reflection plate, and a light source. Also, the light source of the backlight unit  110  includes a plurality of light emitting packages having R, G and B LEDs and an LED voltage generator for generating a driving voltage for driving the R, G and B LEDs. It is preferable that the R, G and B LEDs of the light emitting package emit the light commonly in response to a single driving voltage from the LED voltage generator. The light emitting package  112  connected to the LED voltage generator  120  can be expected as the light source having the light emitting package that can be driven in response to a single driving voltage. 
     Referring to  FIG. 6 , the light emitting package  112  includes R, G and B LEDs  112   a ,  112   b  and  112   c  connected in series. An input voltage Vin generated from the LED voltage generator  120  is supplied to a serial circuit of the serially-connected R, G and B LEDs  112   a ,  112   b  and  112   c . Due to the R LED  112   a , the input voltage Vin from the LED voltage generator  120  is primarily attenuated as much as the driving voltage V(R) of the R LED  112   a . The primarily attenuated voltage Vin-V(R) is supplied to the serial circuit of the G and B LEDs  112   b  and  112   c . Due to the G LED  112   b , the primarily attenuated voltage Vin-V(R) is secondary attenuated as much as the driving voltage V(G). The secondary attenuated voltage Vin-V(R)-V(G) is supplied to the B LED  112   c . Consequently, voltages with different levels are supplied to the R, G and B LEDs  112   a ,  112   b  and  112   c . On the contrary, the same amount of a current flows through the R, G and B LEDs  112   a ,  112   b  and  112   c  because they are connected in series. 
     The R, G and B LEDs  112   a ,  112   b  and  112   c  exhibit different device characteristics, considering the supplied voltages are different even if the same current is supplied to the R, G, and B LEDs  112   a ,  112   b  and  112   c . The characteristic difference of the R, G and B LEDs  112   a ,  112   b  and  112   c  can be seen from Table 1 below. Table 1 shows device characteristics of the R, G and B LEDs  112   a ,  112   b  and  112   c  using a current, a voltage and a power. 
     
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 Red LED 
                   
                 Green LED 
                   
                 Blue LED 
                   
               
             
          
           
               
                 I(mA) 
                 V(V) 
                 P(W) 
                 V(V) 
                 P(W) 
                 V(V) 
                 P(W) 
               
               
                   
               
             
          
           
               
                 50 
                 1.92 
                 0.096 
                 2.69 
                 0.135 
                 2.91 
                 0.146 
               
               
                 100 
                 1.99 
                 0.199 
                 2.8 
                 0.28 
                 3.0 
                 0.3 
               
               
                 150 
                 2.04 
                 0.306 
                 2.86 
                 0.429 
                 3.04 
                 0.456 
               
               
                 200 
                 2.08 
                 0.416 
                 2.89 
                 0.578 
                 3.06 
                 0.612 
               
               
                 250 
                 2.12 
                 0.53 
                 2.93 
                 0.733 
                 3.08 
                 0.770 
               
               
                 300 
                 2.15 
                 0.645 
                 2.95 
                 0.885 
                 3.10 
                 0.930 
               
               
                 350 
                 2.18 
                 0.763 
                 2.98 
                 1.043 
                 3.13 
                 1.10 
               
               
                   
               
             
          
         
       
     
     As can be seen from Table 1, assuming that the same current flows through the R, G and B LEDs  112   a ,  112   b  and  112   c , different voltages V are supplied to the R, G and B LEDs  112   a ,  112   b  and  112   c . For example, to make a current of 50 mA flow through the R, G and B LEDs  112   a ,  112   b  and  112   c,  1.92 V, 2.69 V, and 2.91 V must be supplied to the R, G and B LEDs  112   a ,  112   b  and  112   c , respectively. 
     Even if the same amount of the current is supplied to the R, G and B LEDs  112   a ,  112   b  and  112   c , the amount of the light emitted from the R, G and B LEDs  112   a ,  112   b  and  112   c  are different. In other words, even if the R, G and B LEDs  112   a ,  112   b  and  112   c  connected in series are driven by the same amount of the current, they have different brightness. Therefore, the R, G, and B LEDs  112   a ,  112   b  and  112   c  connected in series cannot emit a required white light. As a result, to emit the required white light, the R, G and B LEDs  112   a ,  112   b  and  112   c  must be driven individually as illustrated in  FIG. 4 . 
       FIG. 7  is a view illustrating the light source of the backlight unit containing the light emitting package according to an embodiment of the present invention. Referring to  FIG. 7 , the light source of the backlight unit includes a light emitting package  130  connected to the LED voltage generator  120 . The light emitting package  130  includes an LED serial circuit  200  responsive to the input voltage Vin from the LED voltage generator  120 . The LED serial circuit  200  includes R, G and B LEDs LDr, LDg and LDb connected in series between the output terminal of the LED voltage generator  120  and the ground terminal GND. The R, G and B LEDs LDr, LDg and LDb connected in series to the LED voltage generator  120  commonly respond to the input voltage Vin from the LED voltage generator  120 . Also, the R, G and B LEDs LDr, LDg and LDb emit the light corresponding to the amount of the current supplied thereto. 
     The light emitting package  130  includes a current adjuster  210  for adjusting an amount of the current flowing through the R, G and B LEDs LDr, LDg and LDb of the LED serial circuit  200  respectively. The current adjuster  210  may be manufactured in a single module integrated with the LED serial circuit  200 , or may be manufactured separately from the LED serial circuit  200 . The current adjuster  210  adjusts an amount of the respective current flowing through the R, G and B LEDs LDr, LDg and LDb to emit the R, G and B light of the white light. 
     Since the amount of the current flowing through the R, G and B LEDs LDr, LDg and LDb is differently adjusted by the current adjuster  210 , the R, G and B LEDs LDr, LDg and LDb can emit the R light, the G light, and the B light, thereby forming the required white light. Also, the R, G and B LEDs LDr, LDg and LDb connected in series emit the R light, the G light, and the B light commonly in response to the input voltage Vin. 
     Accordingly, unlike the related art in which a plurality of LED voltage generators have been used, the light emitting package uses only one LED voltage generator and simplifies additional circuits such as a controller for controlling the LED voltage generator. In addition, the light emitting package of the present invention can reduce the manufacturing cost of the LCD and the backlight unit. Further, the manufacturing process can be simplified and the volume of the light source of the backlight unit can be reduced. 
       FIG. 8  is a circuit diagram of the light emitting package according to an embodiment of the present invention, for explaining an example of the current adjuster  210  in  FIG. 7 . The current adjuster  210  of the light emitting package  130  includes first to third resistors R 1  to R 3  connected in parallel to the R, G and B LEDs LDr, LDg and LDb of the LED serial circuit  200 . Specifically, the first resistor R 1  is connected in parallel to the R LED LDr, the second resistor R 2  is connected in parallel to the G LED LDg, and the third resistor R 3  is connected in parallel to the B LED LDb. 
     Currents Ir, Ig and Ib flowing through the R, G and B LEDs LDr, LDg and LDb connected in parallel to the first to third resistors R 1  to R 3  may be different from one another because some of the currents Ir, Ig and Ib flowing through the R, G and B LEDs LDr, LDg and LDb are bypassed through the resistors R 1  to R 3 . Therefore, the first to third resistors R 1  to R 3  change the currents Ir, Ig and Ib flowing through the R, G and B LEDs LDr, LDg and LDb, so that the R, G and B LEDs LDr, LDg and LDb emit the R, G and B light for the white light. In other words, the different currents may be supplied to the R, G and B LEDs LDr, LDg and LDb through the first to third resistors R 1  to R 3 , such that the R, G and B LEDs LDr, LDg and LDb emit the same amount of light (that is, the same brightness). 
     To emit the R, G and B light such that the R, G and B LEDs LDr, LDg and LDb can emit the required white light, the first to third resistors R 1  to R 3  have different resistance. In this case, the different currents flow through the R, G and B LEDs LDr, LDg and LDb connected in parallel to the first to third resistors R 1  to R 3 . Specifically, the current Ir flowing through the R LED LDr is different from the current Ig and the current Ib flowing through the G LED LDg and the G LED LDb. As described above, the R, G and B LEDs LDr, LDg and LDb of the LED serial circuit  200  emit the light according to the amount of the current flowing through them (that is, the brightness). 
     Each resistance of the first to third resistors R 1  to R 3  are set to have a ratio based on the difference of the device characteristic so that the R, G and B LEDs LDr, LDg and LDb can emit the same brightness. For example, it is assumed that the brightness of the R LED LDr is 100, the brightness of the G LED LDg is 150, the brightness of the B LED LDb is 200, and the white light having their combined brightness is required. The ratio of the resistances of the first to third resistors R 1  to R 3  increase as it goes from the first resistor R 1  to the third resistor R 3 . 
     Also, the resistances of the first to third resistors R 1  to R 3  are set according to the ratio based on the balance of the R, G and B light. For example, it is assumed that the formation of the white light requires the R LED LDr with the brightness of 100, the G LED LDg with the brightness of 150, and the B LED LDb with the brightness of 200. 
     The ratio of the resistances of the first to third resistors R 1  to R 3  are set to decrease as it goes from the first resistor R 1  to the third resistor R 3 . 
     Like this, the resistances of the first to third resistors R 1  to R 3  are set to an appropriate ratio based on the difference of the characteristics of the R, G and B LEDs LDr, LDg and LDb and the white balance for forming the white light. The first to third resistors R 1  to R 3  whose ratio of the resistances satisfies the difference of the characteristics of the R, G and B LEDs LDr, LDg and LDb and the white balance are connected in parallel to the R, G and B LEDs LDr, LDg and LDb. Therefore, the R, G and B LEDs LDr, LDg and LDb can emit the R, G and B light, which can form the white light, by commonly responding to the input voltage Vin from the LED voltage generator  120 . 
     Accordingly, unlike the related art in which a plurality of LED voltage generators have been used, the light emitting package uses only one LED voltage generator and simplifies additional circuits such as a controller for controlling the LED voltage generator. In addition, the light emitting package of the present invention can reduce the manufacturing cost of the LCD and the backlight unit. Further, the manufacturing process can be simplified and the volume of the light source of the backlight unit can be reduced. 
       FIG. 9  is a circuit diagram of the light emitting package according to another embodiment of the present invention, for explaining another example of the current adjuster  210  in  FIG. 7 . A current adjuster  210  of the light emitting package  130  includes first to third resistors R 1  to R 3  connected in parallel to the LED serial circuit  200  in a loop shape where an overlapping length is gradually shortened. The first resistor R 1  is connected in parallel to the serial circuit of the R. G and B LEDs LDr, LDg and LDb, the second resistor R 2  is connected in parallel to the serial circuit of the R, G and B LEDs LDg and LDb, and the third resistor R 3  is connected in parallel to the B LED LDb alone. In other words, the B LED LDb forms a triple parallel circuit together with the first to third resistors R 1  to R 3 , the G LED LDg is a dual parallel circuit together with the first and second resistors R 1  and R 2 , and the R LED LDr forms a parallel circuit together with the first resistor R 1 . 
     The current adjuster  210  having the first to third resistors R 1  to R 3  connected in parallel to the LED serial circuit  200  so as to form the loops whose overlapping length is shortened can adjust step-by-step the amount of the current to be supplied to the R, G and B LEDs LDr, LDg and LDb according to the difference of the device characteristics and the white balance. In this case, the R, G and B LEDs LDr, LDg and LDb are connected to form a multiple parallel circuit together with the first to third resistors R 1  to R 3 . 
     Assuming that the device characteristic of the R LED LDr is poorer than them of the G and B LEDs LDg and LDb and the G LED LDg is poorer than the B LED LDb in the device characteristic, the connection patterns of the first to third resistors R 1  to R 3  and the LED serial circuit  200  in  FIG. 9  may have the current adjuster  210  in  FIG. 9 . The arrangement of the R, G and B LEDs LDr, LDg and LDb may be changed according to their each characteristic. Therefore, it will be apparent to those skilled in the art that the positions of the R, G and B LEDs LDr, LDg and LDb may be changed. 
     Among the resistors of the current adjuster  210 , the first resistor R 1  is adjusted to appropriately set the amount of the current Ir flowing through the R LED LDr. Also, the resistance of the first resistor R 1  may be adjusted to appropriately set the amount of the current flowing through the LED serial circuit  200 . The resistance of the second resistor R 2  is adjusted to appropriately set the amount of the current Ig flowing through the G LED LDg within a range less than the amount of the current Ir flowing through the R LED LDr. The resistance of the third resistor R 3  may be adjusted to appropriately set the amount of the current Ib flowing through the G LED LDb within a range less than the amount of the current Ig flowing through the G LED LDg. 
     Using the first to third resistors R 1  to R 3 , the currents Ir, Ig and Ib flowing through the R, G and B LEDs LDr, LDg and LDb may be gradually decreased so as to satisfy the difference of the device characteristics and the required white balance. Accordingly, the R, G and B LEDs LDr, LDg and LDb can emit the R, G and B light, which form the white light, by commonly responding to the input voltage Vin from the LED voltage generator  120 . 
     As a result, the light emitting package of the present invention can easily adjust the white balance based on the R, G and B light by the gradual current adjustment. Accordingly, unlike the related art in which a plurality of LED voltage generators have been used, the light emitting package uses only one LED voltage generator and simplifies additional circuits such as a controller for controlling the LED voltage generator. In addition, the light emitting package of the present invention can reduce the manufacturing cost of the LCD and the backlight unit. Further, the manufacturing process can be simplified and the volume of the light source of the backlight unit can be reduced. 
       FIG. 10  is a circuit diagram of the light emitting package according to an embodiment of the present invention, for explaining another example of the current adjuster  210  in  FIG. 7 . The current adjuster  210  of the light emitting package  130  includes a serial circuit of R, G and B LEDs LDr, LDg and LDb contained in an LED serial circuit  200 , and first, second and third resistors R 1 , R 2  and R 3  connected in parallel to the R, G and B LEDs LDr, LDg and LDb, respectively. That is, the R LED LDr forms a dual serial circuit together with the first and second resistors R 1  and R 2 . Likewise, the B LED LDb forms a dual serial circuit together with the first and third resistors R 1  and R 3 . On the other hand, the G LED LDg forms a serial circuit together with the first resistor R 1  alone. 
     The resistance of the first resistor R 1  is adjusted so as to control the amount of a current flowing through the G LED LDg. If the current Ig flowing through the G LED LDg is well-adjusted to form the required white light in a condition not having the G LED LDg, the first resistor R 1  may not be included to the present embodiment. The resistance of the second resistor R 2  is adjusted such that the amount of a current Ir flowing through the R LED LDr is less than the amount of the current Ig flowing through the G LED LDg. Likewise, the resistance of the third resistor R 3  is adjusted such that the amount of a current Ib flowing through the B LED LDb is less than the amount of the current Ig flowing through the G LED LDg. 
     In this manner, each amount of the currents Ir and Ib flowing through the R and B LEDs LDr and LDb is adjusted based on the amount of the current Ig flowing through the G LED LDg because the green light greatly affects the brightness. In this regard, the resistance of the first resistor R 1  may be adjusted to appropriately set the amount of the current Ig flowing through the G LED LDg and enhance the brightness, considering the difference of the device characteristics and the required white balance. After the amount of the current Ig flowing through the G LED LDg, the resistances of the second and third resistors R 2  and R 3  are adjusted such that the amount of the currents Ir and Ib flowing through the R and B LEDs LDr and LDb are less than the amount of the current Ig flowing through the G LED LDg. Accordingly, the R, G and B LEDs LDr, LDg and LDb can emit the R, G and B light, which form the required white light, by commonly responding to the input voltage Vin from the LED voltage generator  120 . 
     As a result, the light emitting package of the present invention can emit the required white light. Accordingly, like the related art in which a plurality of LED voltage generators have been used, the light emitting package uses only one LED voltage generator and simplifies additional circuits such as a controller for controlling the LED voltage generator. In addition, the light emitting package of the present invention can reduce the manufacturing cost of the LCD and the backlight unit. Further, the manufacturing process can be simplified and the volume of the light source of the backlight unit can be reduced. 
       FIG. 11  illustrates a light emitting package  130  according to another embodiment of the present invention. Referring to  FIG. 11 , the light emitting package  130  is substantially identical to the light emitting package of  FIG. 7 , except that an LED  220  lens is disposed over an LED serial circuit  200 . In  FIG. 11 , since the same reference numerals and signs will be used to refer to the same or like parts as in  FIG. 7 , their detailed description will be omitted for conciseness. 
     The LED serial circuit  200  includes R, G and B LEDs LDr, LDg and LDb that commonly respond to the input voltage Vin from the LED voltage generator  120 . It will be apparent to those skilled in the art that a current adjuster  210  for adjusting the amount of currents flowing through the R, G and B LEDs LDr, LDg and LDb can be implemented in the same manner as in  FIGS. 8 to 10 . 
     The LED lens  220  provides the white light effect by condensing and mixing the R, G and B light emitted from the R, G and B LEDs LDr, LDg and LDb of the LED serial circuit  200 . Also, the LED lens  220  can protect the current adjuster  210  as well as the LED serial circuit  200  having the R, G and B LEDs LDr, LDg and LDb from the external impact. Further, the LED lens  220  can prevent the R, G and B LEDs LDr, LDg and LDb from being contaminated from the foreign particles. 
     The LED lens  220  may be integrally formed with the LED serial circuit  200  and the current adjuster  210 . Unlike this structure, the LED lens  220  may be integrally formed with the LED serial circuit  200  except the current adjuster  210 . 
     As described above, by making the different currents flow through the R, G and B LEDs, the R, G and B LEDs of the light emitting package can emit the R, G and B light, which form the white light, by commonly responding to the single voltage Vin. Accordingly, unlike the related art in which a plurality of LED voltage generators have been used, the light emitting package uses only one LED voltage generator and simplifies additional circuits such as a controller for controlling the LED voltage generator. In addition, the light emitting package of the present invention can reduce the manufacturing cost of the LCD and the backlight unit. Further, the manufacturing process can be simplified and the volume of the light source of the backlight unit can be reduced. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.