Abstract:
A liquid crystal display device includes a liquid crystal panel which includes gate lines, data lines crossing the gate lines, and pixels connected to the gate lines and the data lines; a timing controller for receiving a control signal and image data and for generating a gate control signal and a data control signal; a gate driver for generating a gate signal based on the gate control signal and outputting the gate signal to the gate lines; and a data driver for performing data conversion on the image data based on the data control signal and outputting a conversion result to the data lines, wherein the timing controller analyzes the image data frame by frame data and applies two or more inversion driving techniques to frame data.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 from Korean Patent Application No. 10-2014-0046178 filed Apr. 17, 2014, in the Korean Intellectual Property Office, and all the benefits accruing therefrom, the contents of which are herein incorporated by reference in their entirety. 
       BACKGROUND 
       [0002]    Embodiments of the inventive concepts described herein are directed to a liquid crystal display device and a driving method thereof, and more particularly, are directed to a liquid crystal display device using inversion driving and a driving method thereof. 
         [0003]    In a liquid crystal display device, the arrangement of liquid crystal molecules may be changed by forming an electric field across a liquid crystal layer disposed between two substrates. The transmissivity of incident light may be adjusted due to variations in the arrangement of the liquid crystal molecules, thereby displaying images. 
         [0004]    Based on a phase of a data voltage applied to a data line, a method of driving a liquid crystal display device may be classified as line inversion, column inversion, or dot inversion. In line inversion, a phase of the image data being applied to a data line may be inverted every pixel row. In column inversion, a phase of the image data being applied to a data line may be inverted every pixel column. In dot inversion, a phase of the image data being applied to a data line may be inverted every pixel row and every pixel column. 
         [0005]    To prevent crosstalk or flicker from being seen, line inversion may change appropriately based on the pattern of image data that causes the crosstalk or flicker according to a pixel structure of a display panel. This technique may be known as PDF (Pattern Detect Function). 
       SUMMARY 
       [0006]    One aspect of embodiments of the inventive concept provides a liquid crystal display device comprising a liquid crystal panel that includes gate lines, data lines crossing the gate lines, and pixels connected to the gate lines and the data lines; a timing controller for receiving a control signal and image data and for generating a gate control signal and a data control signal; a gate driver for generating a gate signal based on the gate control signal and outputting the gate signal to the gate lines; and a data driver for performing data conversion on the image data based on the data control signal and outputting a conversion result to the data lines, wherein the timing controller analyzes the image data frame by frame and can apply two or more inversion driving techniques to the frame data. 
         [0007]    In exemplary embodiments, the timing controller comprises an analyzing unit for analyzing the frame data line by line; a setting unit for setting a plurality of data areas that match a Pattern Detect Function (PDF) target pattern; and an applying unit for applying an inversion driving technique independently to each data area. 
         [0008]    In exemplary embodiments, the setting unit sets the data areas using line data with the same PDF target pattern as a boundary. 
         [0009]    In exemplary embodiments, the setting unit sets the data areas using pattern data with the same PDF target pattern as a boundary. 
         [0010]    Another aspect of embodiments of the inventive concept provides a method of driving a liquid crystal display device, the method comprising analyzing a pattern type of line data of input frame data; setting a plurality of data areas that match a Pattern Detect Function (PDF) target pattern; and applying an inversion driving technique independently to each data area. 
         [0011]    In exemplary embodiments, setting a plurality of data areas that match a PDF target pattern comprises determining whether a pattern type of the line data has changed; storing a start point of a data area, if the pattern type of the line data has not changed, the line data matches the PDF target pattern and a pattern of the line data is first recognized; and storing a type of the PDF target pattern of the data area and an end point of the data area, if the pattern type of the line data has not changed, the number of line data that matches the PDF target pattern is greater than a first setting value, and the number of data areas set is less than a second setting value. 
         [0012]    In exemplary embodiments, setting a plurality of data areas that match a PDF target pattern further comprises determining whether the line data is a last line data of the frame data; and storing an end point of the last data area and a type of the PDF target pattern of the last data area, if the number of line data that matches the PDF target pattern is greater than a third setting value and the number of data areas set is less than the second setting value. 
         [0013]    In exemplary embodiments, when the line data does not match the PDF target pattern or a pattern of the line data has been recognized, the method may comprise determining whether the line data is the last line data of the frame data. 
         [0014]    In exemplary embodiments, when the number of line data that matches the PDF target pattern is less than the first setting value or the number of data areas set is greater than the second setting value, the method may comprise determining whether the line data is the last line data of the frame data. 
         [0015]    In exemplary embodiments, when the line data does not match the PDF target pattern, the number of line data that matches the PDF target pattern is less than the third setting value, or the number of line data set is greater than the second setting value, the method may comprise applying an inversion driving technique independently to each data area. 
         [0016]    In exemplary embodiments, setting a plurality of data areas that match a PDF target pattern comprises determining whether a pattern type of the line data has changed; storing first-direction and second-direction location information of a start point of a data area, where the first and second directions are orthogonal to each other, if a pattern type of the line data has not changed, the line data matches a PDF target pattern and a pattern of the line data is first recognized; and storing the first-direction and second-direction location information of an end point of the data area and a type of the PDF target pattern of the data area, if a pattern type of the line data has changed, the number of line data that matches the PDF target pattern is greater than a first setting value, and the number of data areas set is less than a second setting value. 
         [0017]    In exemplary embodiments, setting a plurality of data areas that match a PDF target pattern further comprises determining whether the line data is a last line data of the frame data; and storing the first-direction and second-direction location information of an end point of the last data area and a type of the PDF target pattern of the last data area, if the number of line data that matches the PDF target pattern is greater than a third setting value and the number of data areas set is less than the second setting value. 
         [0018]    In exemplary embodiments, when the line data does not match the PDF target pattern or a pattern of the line data has been recognized, the method may comprise determining whether the line data is the last line data of the frame data. 
         [0019]    In exemplary embodiments, when the number of line data that matches the PDF target pattern is less than the first setting value or the number of data areas set is greater than the second setting value, the method may comprise determining whether the line data is the last line data of the frame data. 
         [0020]    In exemplary embodiments, when the line data does not match the PDF target pattern, the number of line data that matches the PDF target pattern is less than the third setting value, or the number of line data set is greater than the second setting value, the method may comprise applying an inversion driving technique independently to each data area. 
         [0021]    In exemplary embodiments, setting a plurality of data areas that match a PDF target pattern comprises determining whether a pattern type of the line data has changed; storing first-direction and second-direction location information of start and intermediate points of a data area, where the first and second directions are orthogonal to each other, if a pattern type of the line data has not changed, the line data matches a PDF target pattern and a pattern of the line data is first recognized; and storing the first-direction and second-direction location information of an end point of the data area and a type of the PDF target pattern of the data area, if a pattern type of the line data has changed, the number of line data that matches the PDF target pattern is greater than a first setting value, and the number of data areas set is less than a second setting value. 
         [0022]    In exemplary embodiments, there may be a plurality of intermediate points. 
         [0023]    Still another aspect of embodiments of the inventive concept provides a method of driving a liquid crystal display device, the method comprising analyzing a pattern type of line data of input frame data to determine a number of data that matches a Pattern Detect Function (PDF) target pattern; storing the line data as an object to which PDF is applied or as an object to which PDF is not applied; and applying an inversion driving technique independently to each line data. 
         [0024]    In exemplary embodiments, storing the line data as an object to which PDF is applied or as an object to which PDF is not applied comprises determining whether the number of line data that matches a PDF target pattern is greater than a fourth setting value; storing the line data as an object to which PDF is applied, if the number of line data that matches the PDF target pattern is greater than the fourth setting value; and storing the line data as an object to which PDF is not applied, if the number of line data that matches the PDF target pattern is less than the fourth setting value. 
         [0025]    In exemplary embodiments, storing the line data as an object to which PDF is applied or as an object to which PDF is not applied further comprises determining whether the line data is a last line data of the frame data. If the line data is the last line data of the frame data, the inversion driving technique is independently applied to each line data; if the line data is not the last line data of the frame data, a pattern type of line data of input frame data is analyzed to determine the number of data that matches a PDF target pattern. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0026]      FIG. 1  is a block diagram that schematically illustrates a liquid crystal display device according to an embodiment of the inventive concept. 
           [0027]      FIG. 2  is a block diagram that schematically illustrates a timing controller shown in  FIG. 1 . 
           [0028]      FIGS. 3A-B  is a flow chart that schematically illustrates a method of changing inversion driving according to an embodiment of the inventive concept. 
           [0029]      FIG. 4  is a conceptual diagram that shows an image on which frame data is divided into areas is displayed. 
           [0030]      FIG. 5  is a diagram that schematically illustrates an image that is displayed when a first inversion technique is applied to specific frame data. 
           [0031]      FIG. 6  is a diagram that schematically illustrates an image that is displayed when a second inversion technique is applied to the same frame data as shown in  FIG. 5 . 
           [0032]      FIG. 7  is a flow chart that schematically illustrates a method of changing an inversion driving technique, according to another embodiment of the inventive concept; 
           [0033]      FIGS. 8A-B  is a flow chart that schematically illustrates a method of changing inversion driving according to another embodiment of the inventive concept; 
           [0034]      FIG. 9  is a conceptual diagram that shows an image on which frame data that is divided into areas is displayed; 
           [0035]      FIGS. 10A-B  is a flow chart that schematically illustrates a method of changing inversion driving according to still another embodiment of the inventive concept. 
           [0036]      FIG. 11  is a conceptual diagram that shows an image on which frame data that is divided into areas is displayed. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    Embodiments will be described in detail with reference to the accompanying drawings. The inventive concept, however, may be embodied in various different forms, and should not be construed as being limited only to the illustrated embodiments. Unless otherwise noted, like reference numerals may denote like elements throughout the attached drawings and written description, and thus descriptions will not be repeated. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. 
         [0038]    It will be understood that when an element or layer is referred to as being “on”, “connected to”, “coupled to”, or “adjacent to” another element or layer, it can be directly on, connected, coupled, or adjacent to the other element or layer, or intervening elements or layers may be present. 
         [0039]      FIG. 1  is a block diagram that schematically illustrates a liquid crystal display device according to an embodiment of the inventive concept. 
         [0040]    As shown in  FIG. 1 , a liquid crystal display device  1000  according to an embodiment of the inventive concept includes a liquid crystal panel  100 , a timing controller  200 , a gate driver  300 , and a data driver  400 . 
         [0041]    In the liquid crystal panel  100 , a plurality of gate lines G 1  to Gm extend in a first direction DR 1 , and a plurality of data lines D 1  to Dn extend in a second direction DR 2  crossing the first direction DR 1 . Pixel areas may be defined by the gate lines G 1  to Gm and the data lines D 1  to Dn. Pixels PX that display an image are provided in the pixel areas, respectively. In  FIG. 1 , there is shown a pixel PX that is connected to a first gate line G 1  and a first data line D 1 . 
         [0042]    The timing controller  200  receives image data RGB and a control signal from an external graphics control unit. The control signal may contain a vertical synchronization signal, hereinafter referred to as the Vsync signal, that separates frames, a horizontal synchronization signal, hereinafter referred to as the Hsync signal, that separates rows, a data enable signal, hereinafter referred to as the DE signal, that is high only during an interval in which data is output to indicate a data-in interval, and a main clock signal MCLK. The timing controller  200  converts the image data RGB into a form suitable for the data driver  400  and outputs the converted data to the data driver  400 . The timing controller  200  generates a gate control signal GS 1  and a data control signal DS 1 . The timing controller  200  outputs the gate control signal GS 1  to the gate driver  300  and the data control signal DS 1  to the data driver  400 . The gate control signal GS 1  controls the gate driver  300 , and the data control signal DS 1  controls the data driver  400 . 
         [0043]    The timing controller  200  analyzes the image data RGB frame by frame. The timing controller  200  may apply inversion driving to the frame data N times, where N is an integer of 2 or more. This will be more fully described below. 
         [0044]    The gate driver  300  generates a gate signal based on the gate control signal GS 1  and outputs it to the gate lines G 1  to Gm. 
         [0045]    The data driver  400  converts the image data RGB based on the data control signal DS 1  and outputs resultant data to the data lines D 1  to Dn. 
         [0046]      FIG. 2  is a block diagram that schematically illustrates a timing controller shown in  FIG. 1 . 
         [0047]    Referring to  FIGS. 1 and 2 , a timing controller  200  incorporates an analyzing unit  210 , a setting unit  220 , and an applying unit  230 . 
         [0048]    The analyzing unit  210  analyzes frame data line by line. 
         [0049]    The setting unit  220  sets a plurality of data areas that match a PDF target pattern. The PDF target pattern includes a variety of patterns to which inversion driving is to be applied. 
         [0050]    The setting unit  220  may set data areas using line data having the same PDF target pattern as a boundary. 
         [0051]    In exemplary embodiments, the setting unit  220  determines a pattern type of the line data. If a pattern type of line data does not change and the number of line data that matches the PDF target pattern and a line data type are first recognized, the setting unit  220  stores a start point of the data area. If a pattern type of the line data change and the number of line data that matches the PDF target pattern is greater than a first setting value and the number of data areas set is less than a second setting value, the setting unit  220  stores an end point of the data area and a type of the PDF target pattern of the data area. The setting unit  220  determines whether the line data is the last line data of the frame data. If the number of line data matched with the PDF target pattern is greater than a third setting value and the number of data areas set is less than the second setting value, the setting unit  220  stores an end point of the last data area and a type of the PDF target pattern of the last data area. 
         [0052]    In other exemplary embodiments, the setting unit  220  may set data areas using pattern data of line data having the same PDF target pattern as a boundary. The line data may be formed of segments of the respective line data. That is, in other exemplary embodiments, the data areas may be partitioned using a vertical line as well as a horizontal line as a boundary. The setting unit  220  determines whether a pattern type of the line data changes. If a pattern type of the line data does not change and the line data matches the PDF target pattern and a pattern in the line data is first recognized, the setting unit  220  stores first-direction and second-direction location information of a start point of a data area. If a pattern type of line data changes and the number of line data that match the PDF target pattern is greater than the first setting value and the number of data areas set is less than the second setting value, the setting unit  220  stores first-direction and second-direction location information of an end point of the data area. The setting unit  220  determines whether the line data is the last line data of the frame data. If the number of line data matched with the PDF target pattern is greater than the third setting value and the number of data areas set is less than the second setting value, the setting unit  220  stores the first-direction and second-direction location information of an end point of the last data area and a type of the PDF target pattern of the last data area. 
         [0053]    In still other exemplary embodiments, the setting unit  220  determines whether a pattern type of the line data changes. If a pattern type of the line data does not change and the line data matches the PDF target pattern and a pattern of the line data is first recognized, the setting unit  220  stores first-direction and second-direction location information of each of the start and end points of a data area. If the number of line data that matches the PDF target pattern is greater than the first setting value and the number of data areas set is less than the second setting value, the setting unit  220  stores the first-direction and second-direction location information of an end point of the data area and a type of the PDF target pattern of the data area. 
         [0054]    In still other exemplary embodiments, the setting unit  220  may store the line data as a target to which PDF may or may not be applied. 
         [0055]    The applying unit  230  may independently apply inversion driving to the data areas. At this time, the applying unit  230  may determine whether to apply the inversion driving to each data area and may apply different inversion driving techniques to the data areas. 
         [0056]    Below, referring to  FIGS. 3 and 4 , will be described a method of dividing a frame of image data into a plurality of data areas and independently applying inversion driving to each data area. 
         [0057]      FIGS. 3A-B  is a flow chart that schematically illustrates a method of changing inversion driving according to an embodiment of the inventive concept.  FIG. 4  is a conceptual diagram that shows an image on which frame data that is divided into areas is displayed. 
         [0058]    Referring to  FIGS. 3A-B  and  4 , in step S 1 , a frame of image data is received. Below, a frame of image data may be referred to as frame data F-DATA. The frame data F-DATA includes a plurality of line data L-DATA. The line data L-DATA may be data that is to be applied to pixels connected by a gate line. 
         [0059]    In step S 2 , a pattern type is determined by analyzing an input pattern of the line data L-DATA. In step S 3 , it is determined whether a pattern type of ith line data, where i is a natural number, changes. This may accomplished by comparing a pattern type of an i-th line data with that of (i−1)th line data. First line data may be determined as a pattern type that is unchanged, since the object to be compared with the first line data does not exist. 
         [0060]    If a pattern type does not change, it is determined in step S 4  whether the ith line data matches with a PDF target pattern. The PDF target pattern may be a pattern of the object to be inversely driven and may include a plurality of patterns. If the ith line data is determined as matching the PDF target pattern, the number of line data following the ith line data that match the PDF target pattern is counted in step S 5 . If the ith line data is determined as not matching the PDF target pattern, it is determined in step S 8  whether the ith line data is the last line data of the frame data F-DATA. 
         [0061]    In step S 6 , it is determined whether the ith line data is line data of an input pattern that has been first recognized in the continuous line data with the same PDF target pattern. If so, in step S 7 , the ith line data is stored as a start point of a data area. If not, the method proceeds to step S 8  in which it is determined whether the ith line data is the last line data of the frame data F-DATA. 
         [0062]    Returning to step S 3 , if a pattern type of the ith line data is determined as changing, it is determined in step S 9  whether the number of line data following the ith line data matched with the PDF target pattern is greater than a first setting value. The first setting value may be a reference for determining whether to set a separate data block for changing an inversion technique. The smaller the first setting value, the greater the number of data areas obtained from the frame data F-DATA. An inversion driving technique may change under this condition, but the size of memory needed to store the data areas increases. If the number of line data that follow the ith line data matched with the PDF target pattern is less than the first setting value, the method proceeds to step S 8 . 
         [0063]    If the number of line data that follow the ith line data matched with the PDF target pattern is greater than the first setting value, the method proceeds to step S 10 , in which it is determined whether the number of data areas currently stored is greater than a second setting value. Since the size of memory for storing data areas increases as the number of data areas increases, it is determined whether to set additional data areas based on the second setting value. If the number of data areas is greater than the second setting value, the method proceeds to step S 8  without setting a data area. If the number of data areas is less than the second setting value, in which case there remains memory for storing data areas, the method proceeds to step S 11 , in which the (i−1)-th line data before the pattern type change is stored as an end point of a data area. In step S 12 , the type of the PDF target pattern of the data area between the start point and the end point is stored. 
         [0064]    Returning to step S 8 , if the ith line data is the last line data of the frame data F-DATA, the method proceeds in step S 13 , in which it is determined whether the ith line data matches with the PDF target pattern. If it is determined that the ith line data is the last line data, steps S 13  to S 16  are performed to determine whether to set the last data block, since the setting of a data block must be terminated regardless of whether a pattern type changes. If it is determined that the ith line data is the last line data of the frame data F-DATA, the method proceeds to step S 2  to set a new data area. 
         [0065]    Returning to step S 13 , if the ith line data matches the PDF target pattern, the method proceeds to step S 14 , in which it is determined whether number of line data following the ith line data that match the PDF target pattern is greater than a third setting value. The third setting value may be a reference that is used to determine whether to set the last data block for changing an inversion technique. The third setting value may be equal to the first setting value. If it is determined that number of line data following the ith line data that match the PDF target pattern is less than the third setting value, the method proceeds to step S 18  to terminate the setting of a data area. 
         [0066]    If it is determined that number of line data following the ith line data that match the PDF target pattern is greater than the third setting value, in step S 14 , it is determined whether the number of data areas currently stored is greater than a second setting value. If the number of data areas currently stored is greater than the second setting value, the method proceeds to step S 18  to terminate the setting of a data area. 
         [0067]    If it is determined that the number of data areas currently stored is less than the second setting value, i.e. memory remains to store data areas, the ith line data is stored in step S 16  as an end point of the last data area. In step S 17 , the type of the PDF target pattern of the last data area is stored. In step S 18 , an inversion driving technique is independently applied every data area. According to an embodiment of the inventive concept, it is possible to apply a different inversion driving technique to each data area as well as to determine whether to apply an inversion driving technique independently to each data area. 
         [0068]    In  FIG. 4 , the frame data F-DATA is illustrated as being divided into three data areas DA 1  to DA 3 . Each data area DA 1  to DA 3  may include a plurality of line data L-DATA. In  FIG. 4 , each data area DA 1  to DA 3  is illustrated as including three line data L-DATA. Different inversion driving techniques may be applied to the data areas DA 1  to DA 3 . Also, an inversion driving technique may be applied to some but not all of the data areas DA 1  to DA 3 . 
         [0069]      FIG. 5  is a diagram that schematically illustrates an image that is displayed when a first inversion technique is applied to specific frame data. FIG.  6  is a diagram that schematically illustrates an image that is displayed when a second inversion technique is applied to the same frame data as shown in  FIG. 5 . 
         [0070]    In  FIGS. 5 and 6 , frame data is illustrated as being displayed on a 24×16 pixel part of a liquid crystal panel  100 . In  FIGS. 5 and 6 , a sign “+” indicates that a polarity of a data voltage applied to a pixel is positive, and a sign “−” indicates that a polarity of a data voltage applied to a pixel is negative. A hatched box indicates a pixel to which a data voltage with “0” gray scale (black), hereinafter referred to as off data, is applied, and a white box indicates a pixel to which a data voltage with a gray scales other than “0”, hereinafter referred to as on data, is applied. 
         [0071]    The frame data has a first data area DD 1  and a second data area DD 2 . In the first data area DD 1 , the on data and off data are alternately displayed in a first direction DR 1  with the on data and off data each displayed on two pixels. Also, in the first data area DD 1 , on data or off data is continuously displayed in a second direction DR 2 . In the second data area DD 2 , the on data and off data are alternately displayed in the first direction DR 1  with the on data and off data each displayed on three pixels. Also, in the second data area DD 2 , the on data and off data are alternately displayed in the second direction DR 2  with the on data and off data each displayed on one pixel. 
         [0072]    Below, data applied to a row of pixels adjacent in the first direction DR 1  may be referred to as horizontal line data. 
         [0073]    Referring to  FIG. 5 , a first inversion technique is a technique in which a polarity of a data voltage is inverted every two pixels in the first direction DR 1 , which is the direction along which gate lines extend, but it is inverted every pixel in the second direction DR 2 , which is the direction along which data lines extend. 
         [0074]    In the first data area DD 1 , all on data included in the horizontal line data may have the same polarity (“+” or “−”). Horizontal line data, such as first line data, with “+” polarity on-data may shift a common voltage in a positive-polarity direction, and horizontal line data, such as second line data, with “−” polarity on-data may be shift the common voltage in a negative-polarity direction. In this case, a horizontal line is seen every pixel row, and crosstalk may occur between outer data and the first data area DD 1  when the outer data exists outside of the first data area DD 1 . 
         [0075]    In the second data area DD 2 , a ratio of positive polarities to negative polarities of on data in the horizontal line data is equal to one. However, only on data having the same polarity may be displayed in a part AA 1  of the second data area DD 2 , which appears as a horizontal line every other pixel line. 
         [0076]    Referring to  FIG. 6 , it may be assumed that an inversion technique of the first and second data areas DD 1  and DD 2  has changed from a first inversion technique to a second inversion technique. 
         [0077]    The second inversion technique is a technique in which polarities of the 5 th  and 6 th  dots and polarities of the 7 th  and 8 th  dots are switched on the basis of eight dots in a first direction DR 1 . For example, a first dot row has polarities of “++−−++−−” according to the first inversion technique, but it has polarities of “++−−−−++” according to the second inversion technique. 
         [0078]    A ratio of positive polarities to negative polarities of on data included in horizontal line data may be equal to one by applying the second inversion technique to the first data area DD 1 . Thus, it is possible to correct the voltage shift, described with reference to  FIG. 5 , that occurs in the first data area DD 1  when the first inversion technique is applied. 
         [0079]    In the second data area DD 2 , the number of on data having the same polarity in an area AA 2  increases as compared with  FIG. 5  where the first inversion technique is used. This means that a horizontal line may be more clearly seen in plural pixel rows as compared with  FIG. 5 . 
         [0080]    The voltage shift described with reference to  FIGS. 5 and 6  may occur when the same inversion technique is applied to one frame data. According to an embodiment of the inventive concept, one frame data may be divided into a plurality of data areas and independent inversion driving techniques may be applied to each of the data areas. Thus, a horizontal line, a vertical line, and crosstalk may not appear although an image is displayed that includes the first and second data areas DD 1  and DD 2  in a frame. 
         [0081]    Referring to  FIG. 7 , a method of applying an inversion driving technique independently to each line data of a frame of image data will be described. 
         [0082]      FIG. 7  is a flow chart that schematically illustrates a method of changing an inversion driving technique, according to another embodiment of the inventive concept. 
         [0083]    Referring to  FIG. 7 , in step S 20 , a frame of image data is received. Below, a frame of image data is referred to as frame data. The frame data includes a plurality of line data to be applied to pixels connected to a gate line. 
         [0084]    In step S 21 , the number of data that matches a PDF target pattern is determined by analyzing an input pattern of the line data. In step S 22 , it is determined whether the number of data from ith line data, where i is a natural number, that matches the PDF target pattern is greater than a fourth setting value. The fourth setting value may be a reference that is used to determine whether to apply an inversion driving technique to the ith line data. 
         [0085]    In step S 23 , the ith line data is stored as a PDF target when the number of data from ith line data that matches the PDF target pattern, is greater than the fourth setting value. In step S 23 , the line data may be stored with a pattern type of the line data as well as information indicating that it is the PDF target. If the number of data from ith line data that matches the PDF target pattern is smaller than the fourth setting value, the ith line data is stored in step S 24  as an object to which PDF is not applied. 
         [0086]    In step S 25 , it is determined whether the ith line data is the last line data of the frame data. If not, the method proceeds to step S 21 . If so, the method proceeds to step S 26 . In step S 26 , an inversion driving technique is applied every line data, based on information stored with every line data that indicates whether PDF is to be applied. 
         [0087]    With the method described with reference to  FIG. 7 , it is possible to determine whether to apply PDF every line data. Thus, defects that may occur when an image with various patterns is displayed, such as a horizontal line, a vertical line, and crosstalk, may be eliminated. 
         [0088]      FIGS. 8A-B  is a flow chart that schematically illustrates a method of changing inversion driving according to another embodiment of the inventive concept.  FIG. 9  is a conceptual diagram that shows an image on which frame data that is divided into areas is displayed. 
         [0089]    Referring to  FIGS. 8A-B  and  9 , in step S 31 , a frame of image data is received. Below, a frame of image data may be referred to as frame data F-DATA. The frame data F-DATA includes a plurality of line data L-DATA. The line data L-DATA may be applied to pixels connected with a gate line. 
         [0090]    In step S 32 , a type of a pattern is determined by analyzing an input pattern of the line data L-DATA. In step S 33 , it is determined whether a pattern type of ith line data, where i is a natural number, has changed. This may accomplished by comparing a pattern type of an ith line data with that of (i−1)th line data. First line data may be determined to be an unchanged pattern type, since the object to be compared with does not exist. 
         [0091]    If a pattern type is determined as being unchanged, it is determined in step S 34  whether the ith line data matches a PDF target pattern. The PDF target pattern may be an object pattern to be inversely driven and may include a plurality of patterns. If the ith line data is determined as being matched with the PDF target pattern, then, in step S 35 , the number of line data following the ith line data that match the PDF target pattern is counted. If the ith line data is determined as not matching the PDF target pattern, the method proceeds to step S 38 , in which it is determined whether the ith line data is the last line data of the frame data F-DATA. 
         [0092]    In step S 36 , it is determined whether an input pattern of the ith line data is first recognized as the same PDF target pattern. If so, in step S 37 , first-direction and second-direction location information of an input pattern of the ith line data is stored as a start point of a data area. In  FIG. 9 , first-direction and second-direction location information (x1, y1) and (x2, y1) of an input pattern first recognized as matching the PDF target pattern is stored as a start point of a data area DA 4 . 
         [0093]    If it is determined that an input pattern of the ith line data is not line data that is first recognized as the same PDF target pattern, the method proceeds to step S 38  in which it is determined whether the ith line data is the last line data of the frame data F-DATA. 
         [0094]    Returning to step S 33 , if a pattern type of the ith line data is determined as having changed, then it is determined in step S 39  whether the number of line data following the ith line data that match the PDF target pattern is greater than a first setting value. The first setting value may be a reference for determining whether to set a separate data block for changing an inversion technique. The smaller the first setting value, the greater the number of data areas that may be obtained from the frame data F-DATA. An inversion driving technique may change under this condition, but the size of memory needed to store the data areas increases. If the number of line data following the ith line data that match the PDF target pattern is less than the first setting value, the method proceeds to step S 38 . 
         [0095]    If the number of line data following the ith line data that match the PDF target pattern is greater than the first setting value, the method proceeds to step S 40 , in which it is determined whether the number of data areas currently stored is greater than a second setting value. Since the size of memory for storing data areas increases as the number of data areas increases, whether to set additional data areas may be determined based on the second setting value. If the number of data areas is greater than the second setting value, the method proceeds to step S 38  without setting a data area. If the number of data areas is less than the second setting value, in which case there remains memory for storing data areas, the method proceeds to step S 41 , in which first-direction and second-direction location information of an input pattern of the (i−1)th line data before a pattern type changes is stored as an end point of a data area. In  FIG. 9 , first-direction and second-direction location information (x3, y2) and (x4, y2) of an input pattern last recognized may be stored as an end point of a data area DA 4  that matches the PDF target pattern. 
         [0096]    In step S 42 , the PDF target pattern type of the data area between the start point and the end point is stored. 
         [0097]    If it is determined that the ith line data is the last line data, steps S 43  to S 46  for determining whether to set the last data block are performed, since the setting of a data block must be terminated regardless of whether a pattern type changes. Returning to step S 38 , if the ith line data is the last line data of the frame data F-DATA, the method proceeds in step S 43 , in which it is determined whether the ith line data matches the PDF target pattern. If it is determined that the ith line data is not the last line data of the frame data F-DATA, the method proceeds to step S 32  to set a new data area. 
         [0098]    Returning to step S 43 , if the ith line data matches the PDF target pattern, the method proceeds to step S 44 , in which it is determined whether the number of line data following the ith line data that matches the PDF target pattern is greater than a third setting value. The third setting value may be a reference that is used to determine whether to set the last data block for changing an inversion technique. The third setting value may be equal to the first setting value. If it is determined that number of line data following the ith line data that matches the PDF target pattern is less than the third setting value, the method proceeds to step S 48  to terminate the setting of a data area. 
         [0099]    If it is determined in step S 44  that number of line data following the ith line data that matches the PDF target pattern is greater than the third setting value, then it is determined in step S 45  whether the number of data areas currently stored is greater than a second setting value. If the number of data areas currently stored is greater than the second setting value, the method proceeds to step S 48  to terminate the setting of a data area. 
         [0100]    If it is determined that the number of data areas currently stored is less than a second setting value, in which case there remains memory for storing data areas, then, in step S 46 , first-direction and second-direction location information of the ith line data is stored as an end point of the last data area. In step S 47 , a type of the PDF target pattern having the last data area is stored. In step S 48 , an inversion driving technique is independently applied to each data area. According to an embodiment of the inventive concept, it is possible to apply a different inversion driving technique to each data area as well as to determine whether to apply an inversion driving technique independently to each data area. 
         [0101]    In  FIG. 9 , the frame data F-DATA is illustrated as being divided into two data areas DA 4  and DA 5 . Different inversion driving techniques may be applied to the data areas DA 4  and DA 5 . In addition, an inversion driving technique may be applied to one, but not both of the data areas DA 4  and DA 5 . The data area DA 4  may be an area where first-direction (DR 1 ) and second-direction (DR 2 ) location information of the start point and first-direction and second-direction location information of the end point are linked. 
         [0102]      FIGS. 10A-B  is a flow chart that schematically illustrates a method of changing inversion driving according to still another embodiment of the inventive concept.  FIG. 11  is a conceptual diagram that shows an image on which frame data that is divided into areas is displayed. 
         [0103]    A method shown in  FIGS. 10A-B  is substantially the same as that shown in  FIGS. 8A-B , except for step S 57 , and a repeated description thereof is thus omitted. Below, an operation associated with step S 57  will be more fully described with reference to  FIGS. 10A-B . 
         [0104]    Referring to step S 36 , if an input pattern of ith line data is line data that is first recognized as having the same PDF target pattern, the method proceeds to step S 57 , in which first-direction and second-direction location information of an input pattern of the ith line data may be stored as a start point of a data area and first-direction and second-direction location information of an intermediate point may be stored. There may be a plurality of intermediate points. As the number of intermediate points increases, it is possible to set a data area to which the PDF is to be applied to approximate an input pattern. 
         [0105]    In case there is one intermediate point, second-direction location information of the intermediate point may be obtained by adding half the number of line data counted in step S 35  to second-direction location information of a start point. In  FIG. 11 , first-direction (DR 1 ) and second-direction (DR 2 ) location information (x1, y1) and (x2, y1) of an input pattern first recognized to set a data area DA 6  matched with a PDF target pattern may be stored as a start point of a data area. In addition, line data may be selected as an intermediate point based on the number of line data matched with the PDF target pattern and the second-direction (DR 2 ) location information of the start point, and first-direction (DR 1 ) and second-direction (DR 2 ) location information (x5, y3) and (x6, y3) of the intermediate points may be stored. 
         [0106]    In  FIG. 11 , the frame data F-DATA is illustrated as being divided into two data areas DA 6  and DA 7 . Different inversion driving techniques may be applied to the data areas DA 6  and DA 7 . In addition, an inversion driving technique may be applied to one but not both of the data areas DA 6  and DA 7 . The data area DA 6  may be an area where first-direction (DR 1 ) and second-direction (DR 2 ) location information of the start point, first-direction and second-direction location information of the intermediate points, and first-direction and second-direction location information of the end point are linked. 
         [0107]    While embodiments of the inventive concept have been described with reference to exemplary embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present inventive concept. Therefore, it should be understood that the above embodiments are not limiting, but illustrative.