Abstract:
An exemplary liquid crystal display ( 20 ) includes a liquid crystal display panel ( 22 ), data lines ( 26 ) connected to the liquid crystal display panel, and a common voltage generator ( 24 ) configured to output a common voltage to the liquid crystal display panel. A predetermined number of the data lines are also connected to the common voltage generator. The common voltage generator generates a common voltage according to data signals received from the predetermined number of data lines.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to liquid crystal displays (LCDs), and more particularly to a liquid crystal display with a common voltage generator for reducing crosstalk. 
       GENERAL BACKGROUND 
       [0002]    Typical LCDs provide advantages of portability, low power consumption, and low radiation. LCDs have thus been widely applied in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. 
         [0003]      FIG. 5  is a schematic, abbreviated diagram of certain components of a conventional LCD  10 , in which LCD  10  includes a liquid crystal display panel (not labeled), a gate driver  11 , and a data driver  12 . 
         [0004]    The liquid crystal panel includes a plurality of parallel gate lines  13  each extending along a first axis, a plurality of parallel data lines  14  each extending along a second axis orthogonal to the first axis, and a plurality of pixel units (not labeled) defined by the intersecting gate lines  13  and data lines  14 . The gate driver  11  is provided to drive the gate lines  13 . The data driver  12  is provided to drive the data lines  14 . 
         [0005]    Each pixel unit comprises a thin film transistor (TFT)  15 , a pixel electrode  18 , a common electrode  19 , and a pixel capacitor (not labeled) defined by the pixel electrode  18  and the common electrode  19 . The pixel capacitor includes a liquid crystal capacitor  16 , and a supplementary capacitor  17  connected in parallel with the liquid crystal capacitor  16 . A source electrode (not labeled) of the TFT  15  is connected to a corresponding data line  14 . A gate electrode (not labeled) of the TFT  15  is connected to a corresponding gate line  13 . A drain electrode (not labeled) of the TFT  15  is connected to the pixel electrode  18 . 
         [0006]    In operation, the gate driver  11  applies a plurality of gate signals, one at a time, to the gate lines  13 , such that, at any given time, only one of the gate lines  13  has a gate signal applied thereto, during which time TFTs  15  connected to the gate line  13  are turned on. The data driver  12  applies a plurality of data signals to the data lines  14 . Each data signal is transmitted to each corresponding pixel electrode  18  via a corresponding turned-on TFT  15 . Thereby, a voltage difference is generated between the pixel electrode  18  and the corresponding common electrode  19  by the data signal applied to the pixel electrode  18  and a common voltage applied to the common electrode  19 . The voltage difference controls the array angles of liquid crystal molecules, thereby controlling light transmission of the corresponding pixel unit. 
         [0007]    To improve displayed images, the LCD  10  typically employs a dot-inversion driving method, wherein voltages applied to each pixel electrode  18  have a positive polarity and then a negative polarity, relative to the common voltage. The voltage polarities of the data signals convert when corresponding TFTs  15  are turned on. However, due to parasitic capacitors between the data lines  14  and the common electrodes  19 , the data signals pull the common voltage up or down via the parasitic capacitors at the moment that the TFTs  15  are turned on, as shown in  FIG. 6 . In addition, it usually takes time for the common voltage to return to its original level. This causes crosstalk in the LCD  10 . This in turn may lead to flickering of images displayed by the LCD  10 . 
         [0008]    What is needed, therefore, is an LCD which can overcome the limitations described. 
       SUMMARY 
       [0009]    A liquid crystal display comprises a liquid crystal display panel with a plurality of data lines connected thereto and a common voltage generator configured to output a common voltage to the liquid crystal display panel. A predetermined number of the data lines are also connected to the common voltage generator. The common voltage generator generates a common voltage according to data signals received from the predetermined number of data lines. 
         [0010]    Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, all views are schematic. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an abbreviated diagram of certain components of an LCD according to a first embodiment of the present invention, the LCD including a common voltage generator. 
           [0012]      FIG. 2  is a circuit diagram of the common voltage generator. 
           [0013]      FIG. 3  is a timing chart illustrating a common voltage influenced by data signals of the LCD of  FIG. 1 . 
           [0014]      FIG. 4  is an abbreviated diagram of certain components of an LCD according to a second embodiment of the present invention. 
           [0015]      FIG. 5  is an abbreviated diagram of certain components of a conventional LCD. 
           [0016]      FIG. 6  is a timing chart illustrating a common voltage influenced by data signals of the LCD of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0017]    Reference will now be made to the drawings to describe preferred and exemplary embodiments in detail. 
         [0018]      FIG. 1  is a schematic, abbreviated diagram of certain components of an LCD  20  according to a first embodiment of the present invention. The LCD  20  includes a printed circuit board (PCB)  21 , a liquid crystal display panel  22 , and a number of flexible printed circuit boards (FPCBs)  23 . The PCB  21  is connected to the liquid crystal display panel  22  via the FPCBs  23 . 
         [0019]    Each of the FPCBs  23  includes a plurality of data lines  26  extending into the liquid crystal display panel  22 , and a data driver  25  for driving the data lines  26 . The PCB  21  includes a common voltage generator  24 . In the illustrated embodiment, six data lines  26  among all of the data lines  26  also extend into the common voltage generator  24 . In the illustrated embodiment, the six data lines  26  are located at the one same FPCB  23 , and are adjacent to each other. 
         [0020]      FIG. 2  is a circuit diagram of the common voltage generator  24 , comprising an inverting-amplifier  241 , a first resistor  242 , a second resistor  243 , six coupling capacitors  245 , six first input terminals  244 , and a second input terminal  246 . In the illustrated embodiment, the resistances of the first and second resistors  242 ,  243  are respectively R 1  and R 2 . 
         [0021]    The six data lines  26  are connected to the six first input terminals  244 , respectively. Each of the first input terminals  244  is connected to a corresponding terminal (not labeled) of the second resistor  243  via one coupling capacitor  245 , respectively. The other terminal of the second resistor  243  is connected to a negative input terminal (not labeled) of the inverting-amplifier  241 . A positive input terminal (not labeled) of the inverting-amplifier  241  is connected to the second input terminal  246 . An output terminal (not labeled) of the inverting-amplifier  241  provides a common voltage for the LCD  20 , and is connected to the negative input terminal via the first resistor  242 . 
         [0022]    In operation, the positive input terminal of the inverting-amplifier  241  receives a reference voltage V ref . Thereby, the common voltage generator  24  outputs a stable common voltage V com . When TFTs (not shown) of the liquid crystal display panel  22  are turned on, the common voltage may be pulled up or down by the influence of the data signals, due to parasitic capacitors that exist between the data lines  26  and a common electrode (not shown). 
         [0023]    Simultaneously, six data signals are applied to the six first input terminals  244  of the common voltage generator  24  via the six data lines  26 , respectively. Thereby, a total voltage V in  is applied to the negative input terminal of the inverting-amplifier  241 . In the present embodiment, V in  is expressed as: 
         [0000]        V   in   =V 1+ V 2+ V 3+ V 4+ V 5+ V 6   (1) 
         [0000]    where V 1 , V 2 , V 3 , V 4 , V 5 , and V 6  respectively represent the six data signals. As a result, the inverting-amplifier  241  outputs a common voltage V out  having a reverse phase. In the present embodiment, V out  is expressed by: 
         [0000]        V   out =( R 1/ R 2)*( V   ref   −V   in )+ V   ref    (2) 
         [0000]    Therefore, when the common voltage V com  is pulled down or up by the data signals, the common voltage generator  24  outputs a reverse phase common voltage V out . The two voltages V com , V out  are superimposed, thus the pulled-down or pulled-up common voltage is soon pulled back, as shown in  FIG. 3 . 
         [0024]    As described, the common voltage generator  24  outputs the common voltage V out  according to the data signals. When the common voltage V com  is pulled down or up by the data signals, the common voltage generator  24  outputs a reverse phase common voltage V out . The two voltages V com , V out  are superimposed, thus the pulled-down or pulled-up common voltage is soon pulled back. As a result, any crosstalk in the LCD  20  is reduced or even eliminated. Accordingly, flickering of images displayed by the LCD  10  can be reduced or even eliminated. 
         [0025]    Furthermore, there are only six data lines  26  connected to the common voltage generator  24 , located at the FPCBs  23 . The LCD  20  with this structure can be easily made. 
         [0026]      FIG. 4  is a schematic, abbreviated diagram of certain components of an LCD  30  according to a second embodiment of the present invention. The LCD  30  has a structure similar to that of the LCD  20 . However, six data lines  36  extending into a common voltage generator  34  are divided into two separate groups (not labeled). Each group includes three adjacent data lines  36 . 
         [0027]    Various modifications and alterations to the above-described embodiments are possible. For example, 6n (where n is a positive integer) data lines  26  may extend into the common voltage generator  24 . The 6n data lines  23  may respectively connect to 2n red pixel units, 2n green pixel units, and 2n blue pixel units of the liquid crystal display panel  22 . The 6n data lines  26  can be adjacently located at one of the FPCBs  23 . The  6 n data lines can instead be located at at least two of the FPCBs  23 . 
         [0028]    It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only; and that changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.