Patent Publication Number: US-6661181-B2

Title: Backlight assembly and liquid crystal display device having the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display (hereinafter referred to as “LCD”) device, and more particularly to a backlight assembly and an LCD device having the same for improving a wiring connection of electrode lines of lamps that provide the light source for the backlight of the LCD device to minimize the size of the LCD device and to reduce the manufacturing cost. 
     2. Description of the Related Art 
     In recent years, information processing appliances have been rapidly developed to have a variety of forms and functions and faster information processing speed. The information processed in such an information processing apparatus has an electrical signal format. A display device serving as an interface is required for a user to confirm the information processed in the information processing apparatus by the naked eyes. 
     Currently, an LCD device having functions of manifesting full-color and attaining high resolution while attaining lightweight and small size compared with the conventional CRT-type display device. As the result, the LCD device has been widely available as a computer monitor that is a representative information processing apparatus, a household wall-hanging television and so on. 
     The LCD device applies electric fields to a liquid crystal layer to convert its molecular arrangement. Then, the LCD device converts the changes of the optical properties such as birefringence, optical linearity, dichroism and optical scattering characteristic of liquid crystal cells according to the molecular arrangement, and uses the modulation of the light by the liquid crystal cells. 
     The LCD device is largely sorted into a TN (Twisted Nematic) type and a STN (Super-Twisted Nematic) type. The liquid crystal display device is, according to the driving method, sorted into an active matrix display type, which uses a switching device and a TN liquid crystal, and a passive matrix type, which uses an STN liquid crystal. 
     A distinguishable difference of two types is that the active matrix display type is applied to a TFT-LCD that drives the LCD by using a TFT and the passive matrix display type does not use a complicated circuit associated with a transistor. 
     Also, according to a method of using a light source, it is classified into a transmissive LCD device using a backlight and a reflective LCD using an external light source. 
     Despite the increased weight and volume, the transmissive LCD device using the backlight as the light source is widely used, because it can independently display images without using an external light source. 
     FIG. 1 is an exploded perspective view schematically showing a conventional LCD device. FIGS. 2,  3  and  4  are circuit diagrams more specifically showing lamps of the backlight assembly shown in FIG.  1  and configurations of an inverter module for driving the lamps. 
     Referring to FIG. 1, an LCD device  900  is formed by an LCD module  700  for displaying an image by being supplied with an image signal, and a face panel case  810  and a rear panel case  820  for retaining LCD module  700 . Here, LCD module  700  has a display unit  710  including an LCD panel  712  for displaying the image. 
     Display unit  710  includes LCD panel  712 , a data-side printed circuit board (PCB)  714 , a gate-side PCB  719 , a data-side tape carrier package  716  and a gate-side tape carrier package  718 . 
     LCD panel  712  has a thin film transistor (TFT) substrate  712   a , a color filter substrate  712   b  and a liquid crystal (not shown). 
     TFT substrate  712   a  is a transparent glass substrate formed with thin film transistors on a matrix. Source terminals of the TFTs are connected with data lines, and gate terminals are connected with gate lines. Also, drain terminals are formed with pixel electrodes consisting of a transparent conductive material such as Indium-Tin-Oxide (ITO). 
     Once electrical signals are supplied to the data lines and gate lines, the source terminals and gate terminals of respective TFTs receive the electrical signals. In accordance with the input of the electrical signals, the TFTs are turned-on or turned-off to supply the electrical signals required for forming the pixels to the drain terminals. 
     A color filter substrate  712   b  is provided facing TFT substrate  712   a . Color filter substrate  712   b  is formed via a thin film processing of RGB pixels that display predetermined colors when light goes through. Color filter substrate  712   b  is coated with a common electrode formed of ITO over the front surface thereof. 
     When the power is supplied to the gate terminals and source terminals of the transistors on the aforementioned TFT substrate  712   a , an electric field is formed between the pixel electrode and common electrode of color filter substrate  712   b . This electric field changes the alignment angle of the liquid crystal injected between TFT substrate  712   a  and color filter substrate  714   b . The light transmissivity changes in accordance with the alignment angle. This allows to have a desired pixel status. 
     In order to control the alignment angle of the liquid crystal of LCD panel  712  and the period of aligning the liquid crystal, a driving signal and a timing signal are supplied to the gate line and data line of the TFT. As shown in the drawing, tape carrier package  716  that is one of a soft circuit board that determines the period of applying the data driving signal is attached to the source side of LCD panel  712 . Also, gate-side tape carrier package  718  that is one of the soft circuit board that determines the period of applying the gate driving signal is attached to the gate side thereof. 
     Data-side PCB  714  and a gate-side PCB  719  for respectively supplying the driving signals to the gate line and data line after being externally received with an image signal out of LCD panel  712  are respectively connected to data tape carrier package  716  on the data line side of LCD panel  712  and gate tape carrier package  718  on the gate line side thereof. Data-side PCD  714  is formed of a source portion that receives the image signal generated from an external information processing apparatus (not shown) such as a computer to supply a data driving signal to LCD panel  712 . Also, gate-side PCB  719  is formed with a gate portion for supplying a gate driving signal to the gate line of LCD panel  712 . In other words, data-side PCB  714  and gate-side PCB  719  generate the gate driving signal and data signal for driving the LCD device and a plurality of timing signals for supplying the driving signals at the appropriate period, so that the gate driving signal is supplied to the gate line of LCD panel  712  via gate-side tape carrier package  718  and the data signal is supplied to the data line of LCD panel  712  via data tape carrier package  716 . 
     A backlight assembly  720  for supplying the consistent light to display unit  710  is provided under the display unit  710 . Backlight assembly  720  includes 1st and 2nd lamp units  723  and  725  equipped at both ends of LCD module  700  for generating the light. 1 st and 2 nd lamp units  723  and  725  are respectively formed by 1st and 2nd lamps  723   a  and  723   b  and 3 rd and 4 th lamps  725   a  and  725   b , which are respectively shielded by first and second lamp covers  722   a  and  722   b.    
     Light guide plate  724  is large enough to correspond to LCD panel  712  of display unit  710  to underlie LCD panel  712  for changing the path of light while guiding the light generated from 1st and 2nd lamp units  723  and  725  toward display unit  710 . In FIG. 1, light guide plate  724  is of an edge-type having a uniform thickness, which has lamp units at both ends of light guide plate  724  for enhancing the light efficiency. The number of first and second lamp units  723  and  725  may be properly set to be arranged by considering the overall balance of LCD device  900 . 
     A plurality of optical sheets  726  are provided to the upper side of light guide plate  724  to make the luminance of light outgoing from light guide plate  724  toward LCD panel  712  consistent. A reflecting plate  728  is installed at the lower side of light guide plate  724  to reflect the light leaking from light guide plate  724  toward light guide plate  724  so as to enhance the light efficiency. 
     Display unit  710  and backlight assembly  720  are fixedly supported by a mold frame  730  which is a receiving container. Mold frame  730  is shaped as a rectangular box with the upper plane opened. Additionally, a chassis  740  is provided for externally bending data-side PCB  714  and gate-side PCB  719  of display unit  710  to fix them to the lower plane of mold frame  730  while preventing the deviation of display unit  710 . Chassis  740  is opened for exposing LCD panel  710 , of which sidewall portion is inwardly bent in the perpendicular direction to cover the upper periphery of LCD panel  710 . 
     Meantime, even not shown in FIG. 1, LCD device  900  is equipped with a 1st inverter INV 1  as shown in FIG. 2 for driving 1st, 2nd, 3rd and 4th lamps  723   a ,  723   b ,  723   c  and  723   d.    
     Referring to FIG. 2, 1st inverter INV 1  has 1st and 2nd transformers T 1  and T 2 , and 1st and 2nd stabilizing circuits  723   e  and  725   e . An output terminal at the high voltage level of a secondary side of 1st transformer T 1  is connected to respective input sides of 1st and 2nd lamps  723   a  and  723   b , i.e., the first electrode. 1st and 2nd ballast capacitors C 1  and C 2  are interposed between the output terminal at the high voltage level of the secondary side of 1st transformer T 1  and the first electrodes of 1st and 2nd lamps  723   a  and  723   b . In association with output sides of 1st and 2nd lamps  723   a  and  723   b , i.e., second electrodes, 1st and 2nd return wires (hereinafter referred to as “RTN”)  723   c  and  723   d  respectively extend long to 1st stabilizing circuit  723   e  within 1st inverter INV 1 . 1st and 2nd RTNs  723   c  and  723   d  are connected to 1st stabilizing circuit  723   e  to supply a feedback current. Referring to FIG. 2, first electrodes of 3rd and 4th lamps  725   a  and  725   b  are connected to output terminals at the high voltage level of a secondary side of 2nd transformer T 2  by interposing 3rd and 4th ballast capacitors C 3  and C 4 . Second electrodes of 3rd and 4th lamps  725   a  and  725   b  are connected to 2nd stabilizing circuit  725   e  within 1st inverter INV 1  via 3rd and 4th RTNs  725   c  and  725   d  which extend toward 1st inverter INV 1 , thereby supplying the feedback current. 
     However, when a single transformer is utilized to drive the plurality of lamps and the electrodes of the lamps are connected in parallel with each other as described above, the current supplied from single transformer is separately supplied to respective lamps. Accordingly, the current applied to respective lamps has a current difference as indicated by the Table 1 below due to a variable load property of the lamp and a difference of a leakage current. Such a current difference becomes large as the lamp current supplied from the transformer becomes lower. Consequently, if the total current of the lamp is low, one side of the lamp is not driven to differ the durability of respective lamps. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 (units: mArms) 
               
            
           
           
               
               
               
               
               
            
               
                 Total 
                   
                   
                   
                   
               
               
                 Lamp 
                 Current of 
                 Current of 
                 Current Difference 
                 Average 
               
               
                 Current 
                 Lamp 1 (723a) 
                 Lamp 2 (723b) 
                 of Lamps 
                 Current 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 12.7 
                 6.9 
                 5.8 
                 1.1 
                 6.35 
               
               
                 11.2 
                 6.6 
                 4.6 
                 2.0 
                 5.60 
               
               
                 9.7 
                 7.5 
                 2.2 
                 5.3 
                 4.85 
               
               
                 8.0 
                 7.0 
                 1.0 
                 6.0 
                 4.00 
               
               
                 5.8 
                 5.8 
                 0 
                 5.8 
                 2.90 
               
               
                 4.0 
                 4.0 
                 0 
                 4.0 
                 2.00 
               
               
                   
               
            
           
         
       
     
     In order to solve this problem, as shown in FIG. 3, a driving system for corresponding the lamp and transformer one by one has been suggested. 
     Referring to FIG. 3, a 2nd inverter INV 2  has 1st, 2nd, 3rd and 4th transformers T 1 , T 2 , T 3  and T 4  and 1st and 2nd stabilizing circuits  723   e  and  725   e . 1st, 2nd, 3rd and 4th transformers T 1 , T 2 , T 3  and T 4  are respectively driven by 1st, 2nd, 3rd and 4th controllers CT 1 , CT 2 , CT 3  and CT 4 . The first electrodes of 1st and 2nd lamps  723   a  and  723   b  are connected to the output terminals at the high voltage level of the secondary sides of 1st and 2nd transformers T 1  and T 2  by interposing 1st and 2nd ballast capacitors C 1  and C 2 . Also, the second electrodes of respective 1st and 2nd lamps  723   a  and  723   b  are serially connected to 1st stabilizing circuit  723   e  within 2nd inverter INV 2  by means of respective 1st and 2nd RTNs  723   c  and  723   d . In the same way, the first electrodes of 3rd and 4th lamps  725   a  and  725   b  are respectively connected to the output terminals at the high voltage level of the secondary sides of 3rd and 4th transformers T 3  and T 4  by interposing 3rd and 4th ballast capacitors C 3  and C 4 . In addition, the second electrodes of 3rd and 4th lamps  725   a  and  725   b  are serially connected to 2nd stabilizing circuit  725   e  within 2nd inverter INV 2  by means of 3rd and 4th RTNs  725   c  and  725   d , respectively. However, if the lamps are driven by one-to-one corresponding transformers as shown in FIG. 3, the frequency among respective transformers of the inverter is not easily synchronized. Therefore, the lamp generates light flickering, making it impossible to obtain a suitable light source as backlight of the LCD device. 
     In order to solve the above problem, as shown in FIG. 4, a method has been proposed in which the lamp corresponds to the transformer one by one and the transformers are coupled in pairs. 
     More specifically, referring to FIG. 4, a 3rd inverter INV 3  is formed by 1st, 2nd, 3rd and 4th transformers T 1 , T 2 , T 3  and T 4  and 1st and 2nd stabilizing circuits  723   e  and  725   e . Low voltage level terminals of the secondary sides of 1st and 2nd transformers T 1  and T 2  are directly connected to low voltage level terminals of the secondary sides of 3rd and 4th transformers T 3  and T 4 . 1st and 2nd transformers T 1  and T 2  are driven by 1st controller CT 1 , and 3rd and 4th transformers T 3  and T 4  are driven by 2nd controller CT 2 . 
     On the other hand, the first electrode of 1st lamp  723   a  is connected to the output terminal at the high voltage level of 1st transformer T 1  by interposing 1st ballast capacitor C 1 , and the first electrode of 2nd lamp  723   b  is connected to the output terminal at the high voltage level of 2nd transformer T 2  by interposing 2nd ballast capacitor C 2 . The second electrodes of 1st and 2nd lamps  723   a  and  723   b  are serially connected to 1st stabilizing circuit  723   e  within 3rd inverter INV 3  by means of 1st and 2nd RTNs  723   c  and  723   d , respectively. Similarly, the first electrode of 3rd lamp  725   a  is connected to the output terminal at the high voltage level of 3rd transformer T 3  by interposing 3rd ballast capacitor C 3 . Also, the first electrode of 4th lamp  725   b  is connected to the output terminal at the high voltage level of 4th transformer T 4  by interposing 4th ballast capacitor C 4 . The second electrodes of 3rd and 4th lamps  725   a  and  725   b  are serially connected to 2nd stabilizing circuit  725   e  within 3rd inverter INV 3  by means of 3rd and 4th RTNs  725   c  and  725   d , respectively However, although the above-described difficulty of synchronizing the frequency and problem of the flickering phenomenon are solved by coupling the transformers in pairs, the second electrodes of respective lamps are still connected to the stabilizing circuit on the electrical basis by means of the RTN that extends long toward the inverter side. Hence, any increase in the number of lamps not only produces a difficulty in the electrical wiring but also involves a problem of higher manufacturing costs of the backlight assembly. 
     FIGS. 5A and 5B show the configuration of the lamps and inverter module of the direct-type LCD device. 
     As shown in FIG. 5A, the LCD device is formed in a manner that lamp  727  that provides the light is arranged on the bottom plane of a mold frame  730  with a reflecting plate  728  interposed therebetween. Because lamp  727  supplies the light source at the rear side of a display unit  710 , no light guide plate  724  for guiding the side light source toward display unit  710  side is employed, unlike the edge-type LCD device as shown in FIG.  1 . 
     By reflecting the structural feature, direct-type LCD device  900 , as shown in FIG. 5B, is capable of employing a plurality of lamps  727   a ,  727   b ,  727   c ,  727   d ,  727   e ,  727   f ,  727   g  and  727   h . A 4th inverter INV 4  shown in FIG. 5B adopts the configuration of 2nd or 3rd inverter INV 2  or INV 3  shown in FIG. 3 or FIG. 4, in which the connection with the first electrodes of plurality of lamps  727   a ,  727   b ,  727   c ,  727   d ,  727   e ,  727   f ,  727   g  and  727   h  is identical to that of 2nd or 3rd inverter INV 2  or INV 3 . Similarly, the second electrodes of plurality of lamps  727   a ,  727   b ,  727   c ,  727   d ,  727   e ,  727   f ,  727   g and  727   h  are connected to a stabilizing circuit (not shown) within 4th inverter INV 4  by means of respective RTNs RTN 1 , RTN 2 , RTN 3 , RTN 4 , RTN 5 , RTN 6 , RTN 7  and RTN 8 . 
     Also in the direct-type LCD device shown in FIG. 5, the second electrodes of the plurality of lamps are connected to the stabilizing circuit of the inverter via separately-provided RTNs as the driving system shown in FIG. 3 or FIG.  4 . Consequently, the lamp unit becomes bulky as the number of RTNs increases. Further, the manufacturing cost of the backlight assembly increases as the number of RTNs increases. 
     SUMMARY OF THE INVENTION 
     In order to solve the above-mentioned problems of the prior art, an object of the present invention is to provide a backlight assembly capable of improving a connection of electrode lines of lamps that supply a light source for backlight of the LCD device to minimize the size of an LCD device and reduce the manufacturing cost. 
     Another object of the present invention is to provide an LCD device having a backlight assembly capable of improving a connection of electrode lines of lamps that supply a light source for backlight of the LCD device to minimize the LCD device size and reduce the manufacturing cost thereof. 
     To achieve the above object of the present invention, there is provided a backlight assembly including a light emitting unit formed of a plurality of lamps for generating light, and a light controlling unit for enhancing luminance of the light supplied from the light emitting unit. Here, each of the plurality of lamps respectively have two electrodes that include a first electrode directly connected to an electrode of at least one adjacent lamp and selectively have a second electrode supplied with externally provided driving signals. 
     A liquid crystal display device for achieving the above object of the present invention includes a backlight assembly having light emitting unit formed of a plurality of lamps for generating light, and light controlling unit for enhancing luminance of the light supplied from the light emitting unit. In addition, a display unit placed on an upper plane of the light controlling unit receives the light from the light emitting unit via the light controlling unit to display an image. Here, each of the plurality of lamps respectively have two electrodes, and the two electrodes include a first electrode directly connected to an electrode of at least one adjacent lamp and selectively have a second electrode supplied with externally-provided driving signals. 
     At this time, the driving signals are of first and second driving signals having a phase difference of 180° from each other, or N (where N is a constant larger than or the same as 2)—numbered driving signals respectively having a phase difference as many as a value obtained by dividing 360° by the number of the plurality of lamps. At this time, when the driving signals is N-numbered, the sum of respective phases of the N-numbered driving signals is zero. 
     Preferably, the light emitting unit has at least two lamps, the at least two lamps are serially connected to each other, and electrodes of the most preceding lamp and the finally succeeding lamp are supplied with the first and second driving signals, respectively. 
     More preferably, the backlight assembly further has a driving unit for converting the external power source of a DC component into an AC component, and generating the first and second driving signals having the phase different from each other. Also, the driving unit further has a stabilizing circuit for stabilizing current of the plurality of lamps. Thus, low voltage sides of respective secondary sides of the plurality of transformers are connected to the stabilizing circuit, so that the feedback current for stabilizing the current of the plurality of lamps is supplied to stabilizing circuit. 
     At this time, the light emitting unit is placed to contact one end or both ends of the light controlling unit. When the light emitting unit is placed to one end of the light controlling unit, the light controlling unit is a wedge-type light guide plate that becomes thinner as advancing from one end placed with the light emitting unit to the other opposing end. 
     Moreover, the light emitting unit may be placed to the lower plane of the light controlling unit. In this case, the light controlling unit is formed by a plurality of optical sheets for making the luminance of the light supplied from the light emitting unit to the display unit consistent. 
     According to the above-described backlight assembly and liquid crystal display device, the first electrodes of the lamps are respectively connected to the output terminals at the high voltage level of the secondary sides of the corresponding transformers among the transformers constituting the driving unit. Also, the second electrodes of the lamps are directly connected to one another on the electrical basis. The output terminals at the low voltage level of the secondary sides of the transformers are directly connected to the stabilizing circuit to supply the feedback current for stabilizing the current of the lamps to the stabilizing circuit. 
     Therefore, because the second electrodes of respective lamps are not required to extend to the stabilizing circuit of the inverter module so as to supply the feedback current to the stabilizing circuit, no RTN is utilized. For this reason, the wiring structure of the electrode lines of the lamps employed to the backlight assembly is simplified to to reduce the size of the backlight assembly while reducing the manufacturing cost of the backlight assembly and LCD device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and other advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings: 
     FIG. 1 is an exploded perspective view schematically showing a conventional liquid crystal display device. 
     FIG. 2 is a circuit diagram showing a configuration of lamps of the backlight assembly shown in FIG.  1  and an inverter module for driving the lamps in more detail. 
     FIG. 3 is a circuit diagram showing another example of the configuration of the lamps of the backlight assembly shown in FIG.  1  and inverter module. 
     FIG. 4 is a circuit diagram showing still another example of the configuration of the lamps of the backlight assembly shown in FIG.  1  and inverter module. 
     FIGS. 5A and 5B are views showing the configuration of the lamps and inverter module of a direct-type liquid crystal display device. 
     FIG. 6 is an exploded perspective view showing a liquid crystal display device according to a preferred embodiment of the present invention. 
     FIG. 7 is a sectional view showing the sectional structure of the light guide plate and lamp unit shown in FIG.  6 . 
     FIG. 8 is a circuit diagram showing a first embodiment of the configuration of the lamps of the backlight assembly shown in FIG.  6  and inverter module for driving the lamps. 
     FIG. 9 is a circuit diagram showing the configuration of the lamps and inverter module according to the first embodiment shown in FIG. 8 in more detail. 
     FIG. 10 is a graph for illustrating the potential difference at both ends of the lamp according to the first embodiment shown in FIG.  8 . 
     FIG. 11 is a circuit diagram showing a second embodiment of the configuration of the lamps of the backlight assembly shown in FIG.  6  and inverter module for driving the lamps. 
     FIG. 12 is a view representing a phase difference of the driving signals supplied to respective lamps of the second embodiment shown in FIG.  11 . 
     FIG. 13 is a circuit diagram showing a third embodiment of the configuration of the lamps of the backlight assembly shown in FIG.  6  and inverter module for driving the lamps. 
     FIG. 14 is a view representing a phase difference of the driving signals supplied to respective lamps according to the third embodiment shown in FIG.  13 . 
     FIG. 15 is a sectional view showing another example of the sectional structure of the light guide plate and lamp unit shown in FIG.  6 . 
     FIG. 16 is a view for showing a fourth embodiment of the configuration of the lamp of the backlight assembly shown in FIG.  6  and inverter module for driving the lamps. 
     FIG. 17 is a view showing a fifth embodiment of the configuration of the lamps of the backlight assembly shown in FIG.  6  and inverter module for driving the lamps. 
     FIG. 18 is a circuit diagram showing the configuration of the lamps and inverter module according to the fifth embodiment shown in FIG.  17 . 
     FIG. 19 is a view showing a modified example of the configuration of the lamps and inverter module according to the fifth embodiment shown in FIG.  17 . 
     FIG. 20 is a view showing a sixth embodiment of the configuration of the lamps of the backlight assembly shown in FIG.  6  and inverter module for driving the lamps. 
     FIG. 21 is a circuit diagram showing the configuration of the lamps shown in FIG.  6  and inverter module according to the sixth embodiment in more detail. 
     FIG. 22 is a sectional view showing the sectional structure of the lamp unit of the direct-type liquid crystal display device according to a preferred embodiment of the present invention. 
     FIG. 23 is a view showing the configuration of the lamps shown in FIG.  22  and inverter module for driving the lamps. 
     FIG. 24 is a view representing a phase difference of driving signals supplied to respective lamps shown in FIG.  23 . 
     FIG. 25 is a view showing another example of the configuration of the lamps shown in FIG.  16  and inverter module for driving the lamps. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 6 is an exploded perspective view for schematically showing an LCD device according to a preferred embodiment of the present invention. 
     Referring to FIG. 6, an LCD device  100  includes an LCD module  200  for displaying an image by receiving an image signal, and a case  300  formed by a front case  310  and a rear case  32  for accommodating LCD module  200  therein. 
     LCD module  200  has a display unit  210  including an LCD panel  212  for displaying the image. 
     Display unit  210  includes LCD panel  212 , a data-side PCB  214 , a data-side tape carrier package  216 , a gate-side PCB  219  and a gate-side tape carrier package  218 . 
     LCD panel  212  is formed of a TFT substrate  212   a , a color filter substrate  212   b  and a liquid crystal (not shown). 
     TFT substrate  212   a  is a transparent glass substrate formed with TFTs in the matrix form. Source terminals of the TFTs are connected with data lines, and gate terminals are connected with gate lines. Additionally, drain terminals are formed with pixel electrodes consisting of the ITO that is a transparent conductive material. 
     Once an electrical signal is supplied to the data lines and gate lines, the source terminals and gate terminals of respective TFTs receive the electrical signal. In accordance to the electrical signal, the TFTs are turned-on or turned-off to provide the electrical signal for the pixels via the drain terminals. 
     Color filter substrate  212   b  is formed facing TFT substrate  212   a . Color filter substrate  212   b  has the RGB pixels that displays predetermined colors when the light passes through. The RGB pixels are formed by a thing film processing. The common electrode formed of ITO is coated over the whole surface of color filter substrate  212   b.    
     When the electric power is supplied to the gate terminal and source terminal of the TFT on TFT substrate  212   a  to turn on the TFT, an electrical field is formed between the pixel electrode and common electrode of the color filter substrate. This electrical field changes the alignment of the liquid crystal injected between TFT substrate  212   a  and color filter substrate  214   b . Then the changed alignment alters the light transmissivity, to obtain a desired pixel. 
     In order to control the alignment angle and period of the liquid crystal of LCD panel  212 , a driving signal and a timing signal are supplied to the gate line and data line of the TFT. 
     As shown in the drawing, the source side of LCD panel  212  is attached with data tape carrier package  216  which is one of a soft circuit board that determines the period of supplying the data driving signal, and the gate side thereof is attached with gate tape carrier package  218  for determining the period of supplying the gate driving signal. 
     Data-side PCB  214  and gate-side PCB  219  for receiving the image signal from outside of LCD panel  212  to respectively supply the driving signals to the gate line and data line are respectively connected to data tape carrier package  214  at the data line side of LCD panel  212  and gate tape carrier package  210  at the gate line side thereof. Data-side PCB  214  is formed with a source portion for receiving the image signal generated from an external information processing apparatus (not shown) such as a computer to supply the data driving signal to LCD panel  212 . Gate-side PCB  219  is formed with a gate portion for receiving the image signal generated from the external information processing apparatus to supply the gate driving signal to the gate line of LCD panel  212 . 
     In other words, data-side PCB  214  and gate-side PCB  219  generates the gate driving signal and data signal for driving the LCD device and the plurality of timing signals for supplying the driving signals at the appropriate time. They supply the gate driving signal to the gate line of LCD panel  212  via gate tape carrier package  218  and the data signal to the data line of LCD panel  212  via data tape carrier package  216 . 
     A backlight assembly  220  is provided under display unit  210  for providing consistent light to display unit  210 . Backlight assembly  220  includes 1st and 2nd lamp units  223  and  225  installed to one side of LCD module  200  for generating the light. 1st and 2nd lamp units  223  and  225  are formed by 1st &amp; 2nd lamps  223   a  &amp;  223   b  and 3rd &amp; 4th lamps  225   a  &amp;  225   b , which are respectively shielded by first and second lamp covers  222   a  and  222   b.    
     A light guide plate  224  has a size corresponding to LCD panel  212  of display unit  210  and underlies LCD panel  212  for changing the path of light generated from 1st and 2nd lamp units  223  and  225  while guiding the light toward display unit  210  side. In FIG. 6, light guide plate  224  is of an edge-type with constant thickness, and 1st and 2nd lamp units  223  and  225  are installed at both ends of light guide plate  224  to enhance the light efficiency. The number of lamps in 1st and 2nd lamp units  223  and  225  may be properly arranged by considering the overall balance of LCD device  100 . 
     A plurality of optical sheets  226  are provided over light guide plate  224  for making the luminance of the light emitted from light guide plate  224  and reflecting toward LCD panel  212  consistent. A reflecting plate  228  is provided below light guide plate  224  for reflecting the light leaking from light guide plate  224  to light guide plate  224  for enhancing the efficiency of the light. 
     Display unit  210  and backlight assembly  220  are fixedly supported by a mold frame  400  that is a retaining container. Mold frame  400  is a box-like rectangle with an upper plane opened. In addition to these, a chassis  330  is formed for externally bending data tape carrier package  216  and gate tape carrier package  218  of display unit  210  out of mold frame  400  while fixing data PCB  214  and gate PCB  219  to the bottom plane of mold frame  400  to prevent the deviation of display unit  210 . Chassis  330  is opened for exposing LCD panel  210  and the sidewall thereof is inwardly bent in the perpendicular direction to cover the upper periphery portion of LCD panel  210 . 
     FIG. 7 is a sectional view showing the sectional structure of the light guide plate and lamp unit shown in FIG.  6 . 
     Referring to FIG. 7, one end of light guide plate  224  is coupled with first lamp cover  222   a , and 1st and 2nd lamps  223   a  and  223   b  are arranged up and down in the interior of first lamp cover  222   a . Additionally, second lamp cover  222   b  is coupled to the other end opposing to one end of light guide plate  224 , and 3rd and 4th lamps  225   a  and  225   b  are arranged up and down in the interior of second lamp cover  222   b.    
     The up and down arrangement of two lamps such as 1st and 2nd lamps  232   a  and  232   b  shown in FIG. 7 may be identically applied to the wedge-type light guide plate which becomes thinner as advancing from one end toward the other end. The difference is that the lamp unit is installed only at one end of the light guide plate in the wedge-type light guide plate. The wedge-type light guide plate will be described later. 
     Meanwhile, although not shown in FIG. 6, aforementioned LCD device  100  is formed with a 5th inverter INV 5  that supplies an AC signal for driving 1st, 2nd, 3rd and 4th lamps  223   a ,  223   b ,  225   a  and  225   b  as shown in FIG.  8 . 
     FIG. 8 is a circuit diagram showing the configuration of the lamps of the backlight assembly shown in FIGS. 6 and 7 and the inverter module for driving the same. FIG. 9 is a circuit diagram showing the lamps and inverter module shown in FIG. 8 in more detail. FIG. 10 is a graph for explaining a potential difference at both ends of the lamp shown in FIG.  8 . 
     Referring to FIG. 8, 5th inverter INV 5  has 1st, 2nd, 3rd and 4th transformers T 1 , T 2 , T 3  and T 4  numbering the same as the number of lamps employed to the backlight assembly. Here, 1st and 2nd transformers T 1  and T 2  are driven by the driving signal from a 1st controller CT 1 , and 3rd and 4th transformers T 3  and T 4  are driven by the driving signal of a 2nd controller CT 2 . 
     The output terminal at the high voltage level of the secondary side of 1st transformer T 1  is connected to the input side, i.e., first electrode, of 1st lamp  223   a . A 1st ballast capacitor C 1  for stabilizing the current of 1st lamp  223   a  is interposed between the output terminal at the high voltage level of the secondary side of 1st transformer TI and first electrode of 1st lamp  223   a.    
     The output terminal at the high voltage level of the secondary side of 2nd transformer T 2  is connected to the input side, i.e., first electrode, of 2nd lamp  223   b . A 2nd ballast capacitor C 2  for stabilizing the current of 2nd lamp  223   b  is interposed between the output terminal at the high voltage level of the secondary side of 2nd transformer T 2  and first electrode of 2nd lamp  223   b.    
     On the other hand, the output sides, i.e., second electrode  223   c , of 1st and 2nd lamps  223   a  and  223   b  are directly connected to each other on the electrical basis. Also, respective output terminals T 1   a  and T 2   a  at the low voltage level of the secondary sides of 1st and 2nd transformers T 1  and T 2  are directly connected to a stabilizing circuit  227  formed by a capacitor and a resistor within 5th inverter INV 5 . That is, the feedback current for stabilizing the current of 1st and 2nd lamps  223   a  and  223   b  is supplied via the output terminals at the low voltage level of the secondary sides of 1st and 2nd transformers T 1  and T 2 . 
     In the same manner, the output terminal at the high voltage level of the secondary side of 3rd transformer T 3  is connected to the first electrode of 3rd lamp  225   a . A 3rd ballast capacitor C 1  for stabilizing the current of 3rd lamp  225   a  is interposed between the output terminal at the high voltage level of the secondary side of 3rd transformer T 3  and first electrode of 3rd lamp  225   a.    
     The output terminal at the high voltage level of the secondary side of 4th transformer T 4  is connected to the first electrode of 4th lamp  225   b . A 4th ballast capacitor C 4  for stabilizing the current of 4th lamp  225   b  is interposed between the output terminal at the high voltage level of the secondary side of 4th transformer T 4  and first electrode of 4th lamp  225   b.    
     Furthermore, second electrodes  225   c  of 3rd and 4th lamps  225   a  and  225   b  are directly connected to each other on the electrical basis. Respective output terminals T 3   a  and T 4   a  at the low voltage level of the secondary sides of 3rd and 4th transformers T 3  and T 4  are directly connected to stabilizing circuit  229  within 5th inverter INV 5  to supply the feedback current for stabilizing the current of 3rd and 4th lamps  225   a  and  225   b  to stabilizing circuit  229 . 
     Referring to FIG. 9, 1st controller CT 1  is provided at the preceding stage of 1st and 2nd transformers T 1  and T 2 . 1st controller CT 1  includes first and second bias resistors R 1  and R 2  of which one ends are parallel connected with an input terminal of an external signal connected to 1st and 2nd transformers T 1  and T 2 . Also included as parts are a first transistor Q 1  having a base terminal connected to the other end of first bias resistor R 1  to be commonly connected to 1st transformer T 1 , an emitter terminal grounded and a collector terminal connected to 1st and 2nd transformers T 1  and T 2 , and a second transistor Q 2  having a base terminal commonly connected to 1st transformer T 1  with the other end of second bias resistor R 2 , an emitter terminal commonly grounded with the emitter terminal of 1st transistor Q 1  and a collector terminal connected to 1st transformer T 1 . In addition to these, an oscillating capacitor C 5  has one end connected to 1st transformer T 1  to be commonly with the collector terminal of 2nd transistor Q 2 , and the other end connected to the collector terminal of first transistor Q 1 . 1st controller CT 1  having the above-described construction operates as a Royer circuit for converting the externally-supplied DC signal into the AC signal. 
     Meanwhile, the first electrodes of 1st and 2nd lamps  223   a  and  223   b  are respectively connected to the output terminals at the high voltage level of 1st and 2nd transformers T 1  and T 2  via 1st and 2nd ballast capacitors C 1  and C 2 . At this time, the output terminals at the high voltage level of 1st and 2nd transformers T 1  and T 2  respectively connected to the first electrodes of 1st and 2nd lamps  223   a  and  223   b  have the coils wound in the reverse direction opposite to each other. 
     In more detail, the output terminal at the high voltage level of 1st transformer T 1  electrically connected to the first electrode of 1st lamp  223   a  is set as the starting point of wiring the coil. Whereas the output terminal at the high voltage level of 2nd transformer T 2  electrically connected to the first electrode of 2nd lamp  223   b  is set as the ending point of wiring the coil. 
     Therefore, the AC signals respectively applied to 1st lamp  223   a  and 2nd lamp  223   b  from 1st and 2nd transformers T 1  and T 2  have a phase difference of 180° from each other. At this time, the output terminals at the low voltage level of the secondary sides of 1st and 2nd transformers T 1  and T 2  directly connected to stabilizing circuit  227  on the electrical basis supply the feedback current for stabilizing the current flowing through 1st and 2nd lamps  223   a  and  223   b  to respective 1st and 2nd lamps  223   a  and  223   b.    
     When the phase difference of the AC signals respectively supplied to 1st and 2nd lamps  223   a  and  223   b  is 180° from each other as stated above, a virtually zero voltage is generated at the second electrodes portion of 1st and 2nd lamps  223   a  and  223   b  which are directly connected on the electrical basis. 
     Accordingly, as shown in FIG. 10, a potential difference is generated between the first electrode and second electrode of 1st lamp  223   a  at the portions denoted by reference alphabets “A” and “B” to allow 1st and 2nd lamps  223   a  and  223   b  to carry out the light emitting operation. 
     The following Table 2 represents the operational characteristics of the conventional lamp driving system as shown in FIG.  4  and the lamp driving system according to the present invention as shown in FIG.  8 . 
     Referring to Table 2, the conventional driving system shown in FIG.  4  and driving system according to the present invention shown in FIG. 8 have little difference in terms of the power dissipation of the inverter and leakage current of the lamp. In view of the luminance of the backlight, they show similar luminance at the current values of respective lamps. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                   
                 Backlight Luminance 
                 Inverter Power 
                 Lamp Leakage Current 
               
               
                 Respective 
                 (nits) 
                 Dissipation (W) 
                 (mArms) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Lamp 
                   
                 Present 
                   
                 Present 
                 Prior 
                 Present 
               
               
                 Current 
                 Prior Art 
                 Invention 
                 Prior Art 
                 Invention 
                 Art 
                 Invention 
               
               
                 (mArms) 
                 (FIG. 4) 
                 (FIG. 8) 
                 (FIG. 4) 
                 (FIG. 8) 
                 (FIG. 4) 
                 (FIG. 8) 
               
               
                   
               
               
                  6.0 
                 1965 
                 1958 
                 19.3 
                 19.3 
                 1.3 
                 1.3 
               
               
                 5.0 
                 1785 
                 1778 
                 17.2 
                 17.2 
                 1.7 
                 1.7 
               
               
                 4.0 
                 1545 
                 1545 
                 15.1 
                 15.2 
                 2.2 
                 2.2 
               
               
                   
               
            
           
         
       
     
     When considering the result of measuring, the conventional lamp driving system as shown in FIG.  4  and the lamp driving system according to the present invention as shown in FIG. 8 display the similar result in the backlight luminance, power dissipation of the inverter and leakage current of the lamp. However, in the lamp driving system according to the present invention as shown in FIG. 8, the second electrodes of respective lamps are not connected to the stabilizing circuit within the interior of the inverter unlike the conventional lamp driving system. Instead, the second electrodes are directly connected to each other on the electrical basis. This reduces the space occupied by the wiring of the RTN as well as the manufacturing cost of the LCD device. 
     On the other hand, as shown in FIG. 7, because two driving signals are utilized when two lamps are arranged up and down, the driving signals respectively applied to 1st and 2nd lamps  223   a  and  223   b  has the phase difference of 180° from each other. However, the number of lamps may be further increased as required. In this case, the phase of the driving signals supplied to the lamps is variably set in accordance with the number of lamps. FIGS. 11,  12 ,  13  and  14  show another examples of the construction of the lamps shown in FIG.  7 . 
     Referring to FIG. 11, the backlight assembly employs three lamps, i.e., 5th, 6th and 7th lamps  227   a ,  227   b    227   c , as the light source of backlight. A 6th inverter INV 6  for driving 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c  has the transformers, i.e., 5th, 6th and 7th transformers T 5 , T 6  and T 7 , numbering the same as the number of 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c . 5th, 6th and 7th transformers T 5 , T 6  and T 7  are driven by the driving signals from 3rd controller CT 3 . 
     The connection of 5th, 6th and 7th transformers T 5 , T 6  and T 7  and 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c  is the same as that of two lamps. More specifically, the output terminals at the high voltage level of the secondary sides of 5th, 6th and 7th transformers T 5 , T 6  and T 7  are respectively connected to the first electrodes of 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c . 5th, 6th and 7th ballast capacitors C 5 , C 6  and C 7  for stabilizing the current of 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c  are respectively interposed between the first electrodes of 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c and the output terminals at the high voltage level of the secondary sides of 5th, 6th and 7th transformers T 5 , T 6  and T 7 . Additionally, the output terminals at the low voltage level of the secondary sides of 5th, 6th and 7th transformers T 5 , T 6  and T 7  are directly connected to stabilizing circuit  230  for stabilizing the current of 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c  to supply the feedback current. Furthermore, the output sides, i.e., second electrodes, of 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c  are directly connected to one another on the electrical basis. 
     In case of forming by three lamps as described above, the phase difference of the driving signals supplied to respective lamps is determined by the number of lamps. As shown in FIG. 12, the driving signal supplied to 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c  is provided to have a phase difference as many as a value obtained by diving 360° by the number of lamps. That is, if 1st driving signal DS 1  supplied to 5th lamp  227   a  is provided in the form of a sine waveform starting from zero degree, 2nd driving signal DS 2  supplied to 6th lamp  227   b  has a phase delayed as many as 120° from 1st driving signal DS 1  and 3rd driving signal DS 3  supplied to 7th lamp  227   c has a phase delayed as many as 120° from 2nd driving signal DS 2 . 
     Therefore, the sum of the voltage values at respective phases of 1st, 2nd and 3rd driving signals DS 1 , DS 2  and DS 3  is always zero. For example, in FIG. 12, phases of 1st, 2nd and 3rd driving signals DS 1 , DS 2  and DS 3  at a point denoted by a reference alphabet “A” are 90°, −210° and −330° when viewed from 1st driving signal DS 1  as a reference. If it is converted into the voltage value at the corresponding phase, respective voltage values of 1st, 2nd and 3rd driving signals DS 1 , DS 2  and DS 3  can be denoted by V 1 , −V 2  and −V 3 . Therefore, the sum of the voltage values at respective phases of 1st, 2nd and 3rd driving signals D 1 , D 2  and D 3  in the output side of connecting respective second electrodes of 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c  becomes zero to drive 5th, 6th and 7th lamps  227   a ,  227   b  and  227   c.    
     FIG. 13 shows an example of employing four lamps, i.e., 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d , as the light source of the backlight assembly. FIG. 14 shows the phase difference of 4th, 5th, 6th and 7th driving signals DS 4 , DS 5 , DS 6  and DS 7  respectively supplied to 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d.    
     As illustrated, a 7th inverter INV 7  for driving 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d  has 8th, 9th, 10th and 11th transformers T 8 , T 9 , T 10  and T 11  numbering the same as the number of 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d . 8th, 9th, 10th and 11th transformers T 8 , T 9 , T 10  and T 11  are driven by 4th, 5th, 6th and 7th driving signals DS 4 , DS 5 , DS 6  and DS 7  from a 4th controller CT 4 . 
     In the same manner, the output terminals at the high voltage level of the secondary sides of 8th, 9th, 10th and 11th transformers T 8 , T 9  T 10  and T 11  are connected to the first electrodes of 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d . 8th, 9th, 10th and 11th ballast capacitors C 8 , C 9 , C 10  and C 11  for stabilizing the current of 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d  are respectively interposed between the first electrodes of 8th, 9th, 10th and 11th lamps and output terminals at the high voltage level of the secondary sides of 8th, 9th, 10th and 11th transformers T 8 , T 9 , T 10  and T 11 . Also, the output terminals at the low voltage level of the secondary sides of 8th, 9th, 10th and 11th transformers T 8 , T 9 , T 10  and T 11  are directly connected to a stabilizing circuit  233  for stabilizing the current of 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d  to supply the feedback current. The output sides, i.e., second electrodes, of 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d  are directly connected to one another on the electrical basis. 
     In case of forming by four lamps as described above, the phase difference of the driving signals supplied to respective lamps is determined by the number of lamps. As shown in FIG. 14, 4th, 5th, 6th and 7th driving signals DS 4 , DS 5 , DS 6  and DS 7  supplied to 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d  are supplied to have the phase difference having a value of dividing 360° by the number of lamps. In describing with reference to FIG. 14, if 4th driving signal DS 4  supplied to 8th lamp  231   a  is provided in the form of the sine waveform starting from zero degree, 5th driving signal DS 5  supplied to 9th lamp  231   b  has a phase delayed by 90° from 4th driving signal DS 4 . Then, 6th driving signal DS 6  supplied to 10th lamp  231   c  has a phase delayed by 90° from 5th diving signal DS 5 , and 7th driving signal DS 7  supplied to 11th lamp  231   d  has a phase delayed by 90° from 6th driving signal DS 6 . 
     Therefore, the sum of respective phases of 4th, 5th, 6th and 7th driving signals DS 4 , DS 5 , DS 6  and DS 7  is always zero. For example, in FIG. 14, the phases of 4th, 5th, 6th and 7th driving signals DS 4 , DS 5 , DS 6  and DS 7  are respectively 90°, 0°, −270° and 0° at the point of reference alphabet “B” from the point of supplying the signals. When these are converted into the voltage values at corresponding phases, 4th, 5th, 6th and 7th driving signals DS 4 , DS 5 , DS 6  and DS 7  respectively have voltage values of V 4 , V 5 , −V 6  and V 7 . Consequently, the sum of the voltage values at respective phases of 4th, 5th, 6th and 7th driving signals D 4 , D 5 , D 6  and D 7  on the output sides of connecting respective second electrodes of 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d  becomes zero to drive 8th, 9th, 10th and 11th lamps  231   a ,  231   b ,  231   c  and  231   d.    
     While the number of lamps is two to four with reference to FIGS. 7 to  14  described hereinbefore, the connecting method of the lamps and transformers and method of deciding the phase difference of the driving signals supplied from the transformers to the lamps are identical even if the number of lamps is increased to four or more. In other words, since the driving signals supplied to respective lamps are provided in the sine waveform to have the phase difference obtained by dividing 360° by the number of overall lamps, the directly-connected second electrode sides of respective lamps has the voltage value of zero. Accordingly, the RTNs extending from the second electrodes of the lamps toward the inverter module side prior to being connected to the stabilizing circuit can be eliminated free from the number of lamps to make it possible to shrink overall size of the backlight assembly and economize the manufacturing cost. 
     Meantime, the above-described lamp driving system may be identically applied to a wedge-type light guide plate  224   a  as shown in FIG. 15 as well as the edge-type LCD device in which the lamps are installed to both ends of light guide plate  224  as shown in FIG.  7 . 
     In more detail, the second electrodes of 12th and 13th lamps  231   a and  231   b  protected by a third lamp cover  232  on one end of wedge-type light guide plate  224   a  to be installed up and down are directly connected to each other on the electrical basis as shown in FIG.  8 . Additionally, the first electrodes of 12th and 13th lamps  231   a and  231   b  are, as shown in FIG. 8, respectively connected to the separate output terminals at the high voltage level of transformers, and the output terminals at the low voltage level of respective transformers are connected to the stabilizing circuit within the inverter. Consequently, in case of the wedge-type light guide plate  224   a  as shown in FIG. 15, the RTNs of 12th and 13th lamps  231   a and  231   b  are also eliminated to obtain the same effect as of FIG.  8 . 
     FIG. 16 is a view showing another example of the configuration of the lamps of backlight assembly as shown in FIG.  6  and the inverter module for driving the same. 
     Respective second electrodes of the pairs of 1st &amp; 2nd lamps  223   a  &amp;  223   b  and 3rd &amp; and 4th lamps  225   a  &amp;  225   b  shown in FIG. 7 may be connected by extending long toward an 8th inverter INV 8  side. 
     When giving 14th and 15th lamps  234   a  and  234   b  shown in FIG. 16 as an example, the first electrodes of 14th and 15th lamps  234   a  and  234   b  are connected to the output terminals at the high voltage level of the secondary sides of 12th and 13th transformers T 12  and T 13  respectively forming 8th inverter INV 8 . 12th and 13th ballast capacitors C 12  and C 13  for stabilizing the current of 14th and 15th lamps  234   a  and  234   b  are interposed between them. 
     The second electrode of 14th lamp  234   a  extends long to the interior of 8th inverter INV 8 , which in turn extends toward the second electrode side of 15th lamp  234   b  from the interior of 8th inverter INV 8 , thereby being directly connected to the second electrode of 15th lamp  124   b  on the electrical basis. 
     A stabilizing circuit (not shown) for stabilizing the current of 14th and 15th lamps  234   a  and  234   b  is furnished within the interior of 8th inverter INV 8  as shown in FIG.  9 . The feedback current supplied to the unshown stabilizing circuit for stabilizing the current of 14th and 15th lamps  234   a  and  234   b  is applied via the output terminals at the low voltage level of the secondary side of 12th and 13th transformers T 12  and T 13 . 
     In the examples described hereinbefore, the second electrodes of the lamps employed to the backlight assembly of the LCD device shown in FIG. 6 are directly connected to each other, and the transformers of the inverter module numbers the same as the number of lamps to allow the first electrodes of the lamps to be supplied with the driving signals having the phase difference different from each other from the corresponding transformers. However, the plurality of lamps may be driven by using just two transformers regardless of the number of lamps in association with the combination of the electrodes of the plurality of lamps. 
     FIG. 17 is a view showing another example of the configuration of the lamps of the backlight assembly shown in FIG.  6  and the inverter for driving the same, which describes a case that the plurality of lamps are serially connected to one another. FIG. 18 is a circuit diagram more specifically showing the configuration of the lamp shown in FIG.  13  and the inverter module. FIG. 19 shows a modification of the configuration of the lamps shown in FIG.  13  and inverter module. If the plurality of lamps are serially connected, the circuit configuration may have the same form regardless of the number of lamps. Here, a case of utilizing three or four lamps is taken as an example for more detailed description. 
     As shown in FIGS. 17,  18  and  19 , a 9th inverter INV 9  has a 6th controller CT 6  and 14th and 15th transformers T 14  and T 15  driven in response to the driving signals from 6th controller CT 6 . 15th, 16th and 17th lamps  236   a ,  236   b  and  236   c  are serially connected to one another, in which the first electrode of 15th lamp  236   a and the first electrode of 17th lamp  236   c  are arranged to oppose to each other. 
     Thus, as shown in FIG. 18, the first electrode of 15th lamp  236   a is connected to the output  20  terminal at the high voltage level of the secondary side of 14th transformer T 14  by interposing a 14th ballast capacitor C 14 . Also, the first electrode of 17th lamp  236   a  extends long to 9th inverter INV 9  side to be connected to the output terminal at the high voltage level of the secondary side of 15th transformer T 15  by interposing 15th ballast capacitor C 15  between them. 
     In the same manner, a stabilizing circuit  235  as shown in FIG. 9 is furnished within 9th inverter INV 9 . The output terminals at the low voltage level of the secondary sides of 14th and 15th transformers T 14  and T 15  are directly connected to stabilizing circuit  235 , and the feedback current for stabilizing the current of 15th, 16th and 17th lamps  236   a ,  236   b  and  236   c  is supplied to stabilizing circuit  235  via the output terminals at the low voltage level of the secondary sides of 14th and 15th transformers T 14  and T 15 . 
     At this time, the driving signals respectively supplied to the first electrodes of 15th and 17th lamps  236   a and  236   c  from the output terminals at the high voltage level of the secondary sides of 14th and 15th transformers T 14  and T 15  via 14th and 15th ballast capacitors C 14  and C 15  have the phase difference of 180° from each other. This is because, even if the number of lamps is three, 15th, 16th and 17th lamps  236   a ,  236   b  and  236   c  are serially connected to one another, and just the first electrode of 15th lamp that is the most preceding lamp and the first electrode of 17th lamp  236   c  that is the finally succeeding lamp are respectively supplied with the driving signals from 14th and 15th transformers T 14  and T 15 . In other words, when the plurality of lamps are serially connected, always two driving signals are utilized regardless of the number of lamps. For this reason, it is enough to maintain the phase difference of 180° between two driving signals. 
     In such a lamp driving system, 9th inverter INV 9  for driving 15th, 16th and 17th lamps  236   a ,  236   b  and  236   c  is installed to any one side of 15th, 16th and 17th lamps  236   a ,  236   b  and  236   c  as illustrated. Due to this fact, the first electrode of 15th lamp  236   a or the first electrode of 17th lamp  236   c  inevitably extends long toward 9th inverter INV 9  side depending on the installing position of 9th inverter INV 9 . 
     However, when considering that the input stage of the lamps, i.e., first electrodes of 15th, 16th and 17th lamps  236   a ,  236   b  and  236   c , for the backlight of the LCD device, as shown in FIG. 19, 14th and 15th transformers T 14  and T 15  forming 9th inverter INV 9  may be separately arranged to place to be near to the first electrodes of 15th and 17th lamps  236   a and  236   c.    
     FIGS. 20 and 21 show an example of serially connecting four lamps. 
     As shown in FIGS. 20 and 21, a 10th inverter INV 10  has a 7th controller CT 7 , and 16th and 17th transformers T 16  and T 17  driven in response to the driving signal from 7th controller CT 7 . 18th, 19th, 20th and 21st lamps  239   a ,  239   b ,  239   c  and  239   d  are serially connected to one another, which are even-numbered. Accordingly, unlike the three lamps shown in FIG. 17, the first electrode of 18th lamp  239   a and the first electrode of 21st lamp  239   d  are arranged in the same direction. 
     As shown in FIG. 21, the first electrode of 18th lamp  239   a  is connected to the output terminal at the high voltage level of the secondary side of 16th transformer T 16  by interposing a 16th ballast capacitor C 16 . Also, the first electrode of 21st lamp  239   d  extends long toward 10th inverter INV 10  side to be connected to the output terminal at the high voltage level of the secondary side of 17th transformer T 17  by interposing a 17th ballast capacitor C 17 . 
     Similarly, a stabilizing circuit  235  as shown in FIG. 9 is furnished within 10th inverter INV 10  as shown in FIG.  9 . Also, the output terminals at the low voltage level of the secondary sides of 16th and 17th transformers T 16  and T 17  are directly connected to stabilizing circuit  235 . The feedback current for stabilizing the current of 18th, 19th, 20 th and 21st lamps  239   a ,  239   b ,  239   c  and  239   d  is supplied to stabilizing circuit  235  via the output terminals at the low voltage level of the secondary sides of 16th and 17th transformers T 16  and T 17 . 
     At this time, the driving signals respectively supplied to the first electrodes of 18th and 21st lamps  239   a  and  239   d  from the output terminals at the high voltage level of the secondary sides of 16th and 17th transformers T 16  and T 17  via 16th and 17th ballast capacitors C 16  and C 17  have the phase difference of 180° from each other. This is because, when the plurality of lamps are serially connected, just two driving signals are always utilized regardless of the number of lamps even if the lamps number four. Therefore, it is enough for two driving signals to maintain the phase difference of 180°. 
     Here, it is described by giving examples of three and four lamps which are serially connected to one another, but the driving signals are supplied to only the first electrode of the most preceding lamp and the first electrode of the finally succeeding lamp among the plurality of serially-connected lamps, even though the number of lamps increases to four or more. Therefore, by supplying the driving signals having the phase difference of 180° from each other to the first electrodes of the most preceding lamp and the finally succeeding lamp by using two transformers, the driving effect identical to the above-described case can be obtained. 
     FIG. 22 is a sectional view showing the sectional structure of the lamp unit of the direct-type LCD device according to a preferred embodiment of the present invention. FIG. 23 is a view schematically showing the configuration of the lamps shown in FIG.  22  and inverter module for driving the same. FIG. 24 is a waveform for showing the waveforms of the driving signals supplied to respective lamps from the inverter module shown in FIG.  23 . FIG. 25 is a view showing another example of the configuration of the lamps shown in FIG.  22  and inverter for driving the same. 
     As shown in FIG. 22, the direct-type LCD device is formed having a plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  arranged to be separated from one another by a predetermined distance on the bottom plane of mold frame  400  by interposing reflecting plate  228 . At this time, the LCD device utilizes no light guide plate  224  for guiding the side light source toward display unit  210  as in the edge-type LCD device as shown in FIG. 6 because lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  provide the light source from the rear plane of display unit  210 . Diffuision sheet members  226  as a light controlling unit for adjusting the luminance of the light and so on are coupled to the upper plane of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  by securing a predetermined space for advancing the light from lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b.    
     By reflecting the foregoing structural characteristic, the direct-type LCD device shown in FIG. 22 can employ a plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  as shown in FIG.  23 . That is, it is easy to vary the number of lamps in accordance with the area of the LCD panel in the direct-type LCD device. 
     11th inverter INV 11  shown in FIG. 23 employs the formation of 5th inverter INV 5  as shown in FIG. 8, in which the coupling structure of the first electrodes of plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  and the plurality of transformers (not shown) forming 11th inverter INV 1  is identical to that of 1st, 2nd, 3rd and 4th lamps  223   a ,  223   b ,  225   a  and  225   b  and 5th inverter INV 5  shown in FIG.  8 . In other words, 11th inverter INV 11  has the same number of transformers as the number of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b.    
     Additionally, the first electrodes of plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  are connected to the output terminals at the high voltage level of the secondary sides of corresponding transformers among the plurality of transformers in 11th inverter INV 11 . Also, the second electrodes of plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  are directly connected to one another on the electrical basis. 
     In the same manner, the output terminals at the low voltage level of the respective secondary sides of the plurality of transformers constituting 11th inverter INV 11  are directly connected to a stabilizing circuit (not shown) furnished to the interior of 11th inverter INV 11  to supply the feedback current for stabilizing the current of plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  to the stabilizing circuit. 
     Here, 1st, 2nd, 3rd, 4th, 5th, 6th, 7th and 8th driving signals DS 1 , DS 2 , DS 3 , DS 4 , DS 5 , DS 6 , DS 7  and DS 8  respectively provided from the unshown plurality of transformers of 11th inverter INV 11  to plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  respectively have the phase difference different from one another as described with reference to FIGS. 11,  12 ,  13  and  14 . In more detail, when being formed by eight lamps as illustrated, 1st, 2nd, 3rd, 4th, 5th, 6th, 7th and 8th driving signals DS 1 , DS 2 , DS 3 , DS 4 , DS 5 , DS 6 , DS 7  and DS 8  are supplied to have the phase difference of 360° divided by eight. 
     In describing the phase with reference to FIG. 24, first driving signal DS 1  has the phase of zero degree at the supplying point of 1st, 2nd, 3rd, 4th, 5th, 6th, 7th and 8th driving signals DS 1 , DS 2 , DS 3 , DS 4 , DS 5 , DS 6 , DS 7  and DS 8 . Similarly, 2nd, 3rd, 4th, 5th, 6th, 7th and 8th driving signals DS 2 , DS 3 , DS 4 , DS 5 , DS 6 , DS 7  and DS 8  respectively have the phase values of 45°, 90°, 135°, 0°, −225°, −270° and −315° when viewed from 1st driving signal DS 1  as a reference. If these are converted into the voltage values at the corresponding phases, the sum of the voltage values of respective phases of 1st, 2nd, 3rd, 4th, 5th, 6th, 7th and 8th driving signals DS 1 , DS 2 , DS 3 , DS 4 , DS 5 , DS 6 , DS 7  and DS 8  on the output sides connected to the second electrodes of plurality of lamps  244   a ,  244   b ,  244   a ,  244   b    248   a ,  248   b ,  250   a  and  250   b  become zero. Consequently, the sum of the voltage values of respective phases of 4th, 5th, 6th and 7th driving signals DS 4 , DS 5 , DS 6  and DS 7  becomes zero to drive plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b.    
     On the other hand, lamps  244   a ,  244   b ,  244   a ,  244   b    248   a ,  248   b ,  250   a  and  250   b  may be, as shown in FIG. 25, formed by combining adjacent two lamps as pairs, and directly connecting the second electrodes of two lamps in a single pair on the electrical basis. 
     In FIG. 25, a 12th inverter INV 12  is formed by transformers (not shown) numbering the same as the number of plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  and a stabilizing circuit (not shown). The output terminals at the low voltage level of the secondary sides of the plurality of transformers constituting 12th inverter INV 12  are directly connected to the stabilizing circuit to supply the feedback current for stabilizing the current of plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  to the stabilizing circuit. 
     At this time, the driving signals respectively supplied to the first electrodes of plurality of lamps  244   a ,  244   b ,  244   a ,  244   b ,  248   a ,  248   b ,  250   a  and  250   b  are identical to those shown in FIG.  17 . That is, the driving signals are supplied from the plurality of transformers of 12th inverter INV 12  to be fed to each of the lamp pairs, e.g., lamps  244   a &amp;  244   b , lamps  244   b  &amp;  244   a , lamps  244   a &amp;  244   b , lamps  244   b &amp;  248   a , lamps  248   a &amp;  250   a  and lamps  250   a  &amp;  250   b , which are directly connected among plurality of lamps  244   a ,  244   b ,  244   a ,  244   b    248   a ,  248   b ,  250   a  and  250   b  to have the phase difference of 180° from each other. 
     According to the backlight assembly and LCD device having the same as described above, the lamps employed to the backlight assembly for supplying the light are driven by the AC signals from the inverter module consisting of the transformers, controllers and stabilizing circuit. 
     At this time, the numbers of the lamps and the transformers in the inverter module are the same or two transformers may be used. If the numbers of the lamps and the transformers number the same, the first electrodes of the lamps are respectively connected to the output terminals at the high voltage level of the secondary sides of the corresponding transformers among the plurality of transformers within the inverter module, and the second electrodes of the lamps are directly connected to the other on the electrical basis. In addition, when two transformers are employed, the plurality of lamps are serially connected to allow the first electrodes of the most preceding lamp and finally succeeding lamp to be connected to the output terminals at the high voltage level of the secondary sides of two transformers. 
     Furthermore, the output terminals at the low voltage level of the secondary sides of the plurality of transformers are directly connected to the stabilizing circuit within the inverter module to supply the feedback current for stabilizing the current of the lamps to the stabilizing circuit. Also, when the plurality of lamps are serially connected, the AC signals supplied from the inverter module to the lamps are provided to have the phase difference of 180° in the lamps adjacent to each other. Unlike this, if the first electrodes of the plurality of lamps are respectively supplied with the driving signals from the corresponding transformers while the second electrodes are directly connected to each other, respective first electrodes of the plurality of lamps are supplied with the driving signals to have the phase difference of one period of the AC signals in the sine waveform, i.e., the value obtained by dividing 360° by the number of lamps. 
     As a result, respective second electrodes of the lamps are not required to extend to the stabilizing circuit of the inverter module for supplying the feedback current to the stabilizing circuit regardless of the number of lamps, thereby employing no RTNs. 
     Therefore, the wiring structure of the electrode lines of the lamps employed into the backlight assembly is simplified to reduce not only the size of the backlight assembly but also the manufacturing cost of the backlight assembly and LCD device. 
     While the present invention has been particularly shown and described with reference to particular embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the spirit and scope of the invention as defined by the appended claims.