KR20080048246A - Lcd and drive method thereof - Google Patents

Abstract

An LCD(Liquid Crystal Display) device and a driving method thereof are provided to remove horizontal crosstalk by preventing the swing of common voltages according to the up/down conversion of the gray scale values of digital data. An LCD(Liquid Crystal Display) device includes a data pattern detecting unit(162) and a data converter(164). The data pattern detecting unit detects data patterns with the data having a periodic gray scale difference between adjacent data in a horizontal direction among inputted digital data. The data converter executes a down conversion on superior polarity data and an up conversion on inferior polarity data in the data patterns by determining superior polarity data among higher gray scale data in the data patterns. Frequency of the up/down conversions are adjusted for difference voltage between a value, which adds analog data voltages corresponding to the superior polarity data, and a common voltage to be equalized with difference voltage between a value, which adds analog data voltages corresponding to the inferior polarity data, and the common voltage.

Description

Liquid crystal display and driving method thereof

1 is a view illustrating a pixel cell included in a conventional liquid crystal display panel.

2A illustrates an example of a specific pattern.

2B is a view showing waveforms of a data voltage and a common voltage supplied to liquid crystal cells (subpixels) arranged in an i-th horizontal line Hi and an i + 1-th horizontal line Hi + 1 in a specific pattern.

3 is a diagram illustrating a swing phenomenon of a common voltage according to an average level of data voltages of horizontal lines.

4 is a diagram illustrating an example of horizontal crosstalk generated due to a swing of a common voltage.

5 is a configuration diagram of a liquid crystal display device according to the present invention.

FIG. 6 is a detailed configuration diagram of the data conversion circuit 62 of FIG.

7A and 7B illustrate an example of a data pattern according to the present invention.

8A and 8B illustrate liquid crystals disposed on the i-th horizontal line Hi and the i + 1-th horizontal line Hi + 1 after digital data in the data patterns shown in FIGS. 7A and 7B are converted into analog data voltages. A diagram showing the average level of these data voltages when supplied to cells (subpixels).

9A and 9B show changes in average levels of data voltages supplied to horizontal lines corresponding to digital data converted according to the first embodiment of the present invention.

10A and 10B are diagrams for explaining color distortion that appears when the first embodiment of the present invention is applied to the data pattern shown in FIG. 7A.

10A and 10B illustrate a conversion amount of digital data forming a black pattern rather than a conversion amount of digital data forming a white pattern in order to prevent such color distortion according to the second embodiment of the present invention. Drawing to show enlargement.

11A and 11B are diagrams for explaining color distortion that appears when the first embodiment of the present invention is applied to the data pattern shown in FIG. 7B.

11A and 11B illustrate a conversion amount of digital data forming a black pattern rather than a conversion amount of digital data forming a white pattern in order to prevent such color distortion according to the second embodiment of the present invention. Drawing to show enlargement.

FIG. 12A is a view showing a change in the average level Vd of the data voltage supplied to the i-th horizontal line Hi corresponding to FIGS. 10A and 11B.

FIG. 12B is a view showing a change in the average level Vd of the data voltage supplied to the i + 1th horizontal line Hi + 1 corresponding to FIGS. 10B and 11B.

<Description of Symbols for Main Parts of Drawings>

61: timing controller 62: data conversion circuit

63: data driving circuit 64: gate driving circuit

65: data line 66: gate line

67: liquid crystal display panel 160: line memory

162: data detector 162-1: gradation detector

162-2: polarity comparison unit 162-3: data pattern determination unit

164: data converter 164-1: dominant polarity determination unit

164-2: data conversion unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving method thereof, and more particularly, to a liquid crystal display device and a driving method thereof capable of preventing horizontal crosstalk by up-converting or down-converting grayscale values of digital data to be displayed in a specific pattern. will be.

Conventional liquid crystal display devices display an image by adjusting the light transmittance of the liquid crystal using an electric field. The liquid crystal display device includes a liquid crystal display panel in which liquid crystal cells are arranged in a matrix and a driving circuit for driving the liquid crystal display panel.

1, a thin film for driving the liquid crystal cell Clc at the intersection of the gate line GL and the data line DL and crossing the gate line GL and the data line GL, as shown in FIG. 1. A thin film transistor (TFT) is formed. The thin film transistor TFT supplies the data voltage Vd supplied through the data line to the pixel electrode Ep of the liquid crystal cell Clc in response to a scan signal supplied through the gate line GL. To this end, the gate electrode of the thin film transistor TFT is connected to the gate line GL, the source electrode is connected to the data line DL, and the drain electrode is connected to the pixel electrode of the liquid crystal cell Clc. The liquid crystal cell Clc is charged with a potential difference between the data voltage Vd supplied to the pixel electrode Ep and the common voltage Vcom supplied to the common electrode Ec, and the liquid crystal molecules are charged by an electric field formed by the potential difference. As the arrangement changes, it controls the amount of light transmitted or blocks the light. The common electrode Ec is formed on the upper substrate or the lower substrate of the liquid crystal display panel according to the method of applying an electric field to the liquid crystal cell Clc, and between the common electrode Ec and the liquid crystal cell Clc pixel electrode Ep. A storage capacitor Cst is formed to maintain the charging voltage of the liquid crystal cell Clc.

The liquid crystal display panel is driven in an inversion method in which the polarity of the data voltage Vd is inverted at regular intervals to prevent deterioration of the liquid crystal cell Clc. Inversion methods include a dot inversion method, a line inversion method, a column inversion method, and a frame inversion method. The dot inversion method inverts the data signal supplied to the liquid crystal cells in the unit of dots and in the unit of the frame, and has an advantage of providing an image having excellent image quality compared to other methods. The dot inversion method includes a vertical two dot inversion method, a horizontal two dot inversion method, and a one dot inversion method. However, this dot inversion method has a disadvantage of causing a horizontal crosstalk phenomenon in a region extending in the horizontal direction of the specific pattern when a data voltage having a specific pattern is displayed on the liquid crystal display panel.

FIG. 2A shows an example of a specific pattern, and FIG. 2B is supplied to liquid crystal cells (subpixels) arranged in the i-th horizontal line Hi and the i + 1-th horizontal line Hi + 1 in the specific pattern. The waveforms of the data voltage and the common voltage are shown. FIG. 3 shows a swing phenomenon of the common voltage according to the average level of the data voltage for each horizontal line.

As shown in FIG. 2A, a specific pattern may be represented by a white (W)-black (B)-white (W)-black (B) pattern on each pixel including three subpixels of R, G, and B. Data pattern. The R, G, and B liquid crystal cells constituting the subpixels are arranged side by side in a stripe shape, and the polarities of the data voltages supplied to adjacent liquid cells in the horizontal and vertical directions are reversed. Here, it is assumed that white gray W is 205 gray and black gray B is 50 gray.

Pixels arranged on the i-th horizontal line Hi and the i + 1-th horizontal line Hi + 1 are alternately supplied with the data voltage Vd_205 corresponding to the white gray and the data voltage Vd_50 corresponding to the black gray. do. In this case, since the average level of the data voltages of the pixels disposed in the i-th horizontal line Hi is biased toward the positive polarity based on the common voltage Vcom as shown in FIG. 2B, the common voltage Vcom is shown in FIG. As shown in Fig. 3, it swings in the positive direction by the effect of capacitor coupling with this positively biased data voltage. In addition, since the average level of the data voltages of the pixels disposed in the i + 1 th horizontal line Hi + 1 is biased toward the negative polarity based on the common voltage Vcom as shown in FIG. 2B, the common voltage Vcom ) Swings in the negative direction due to the capacitor coupling effect with the negatively biased data voltage as shown in FIG. 3. This common voltage Vcom swing phenomenon also affects the peripheral screen extending in the horizontal direction as shown in FIG. 4, which causes horizontal crosstalk in the peripheral screen.

5 shows an example of horizontal crosstalk generated in a peripheral region extending in a horizontal direction of a specific pattern.

Referring to FIG. 5, when a specific pattern B having vertical stripes is displayed on a portion of the liquid crystal panel image display unit 60, a horizontal crosstalk pattern having vertical stripes is formed in the peripheral region C extending in the horizontal direction of the specific pattern B. It can be seen that. This is because the common voltage that is shaken toward the positive or negative polarity also affects the peripheral region C in the specific pattern B according to the average level of the data voltage in the horizontal period unit.

Recently, in order to reduce horizontal crosstalk generated in the peripheral area C, a method of compensating data to be displayed in the peripheral area C has been proposed. However, since a method of compensating data to be displayed in an area where horizontal crosstalk is generated is greatly influenced by characteristics of the liquid crystal display panel, there are many problems for compensation. It should be considered that the swing width of the common voltage varies depending on the vertical, horizontal, or left and right deviations on the liquid crystal display panel. In particular, various measurements must be performed according to the characteristics of the data of the compensation portion or the application of the actual model. Although the compensation value for one liquid crystal display panel is determined through this process, the compensation value cannot be applied to another liquid crystal display panel due to the deviation between the liquid crystal display panels. This is due to the fact that the conventional compensation method is the resultant compensation method for removing the horizontal crosstalk that has already occurred.

Accordingly, an object of the present invention is to provide a liquid crystal display device and a driving method thereof capable of preventing horizontal crosstalk by up-converting or down-converting a gray value of digital data in a specific pattern.

Another object of the present invention is to provide a liquid crystal display device and a driving method thereof by controlling the amount of upconversion and the amount of downconversion to prevent color distortion in a specific pattern.

In order to achieve the above object, according to the present invention, the digital data is converted into an analog data voltage and the polarity of the analog data voltage is controlled compared to the common voltage to supply the positive analog data voltage and the negative analog data voltages to the data lines. In the liquid crystal display device for displaying an image, a data detector for detecting a data pattern including data having at least two systems in the horizontal direction among the received digital data and even having a periodicity therein. ; And a data converter for down-converting the data of the dominant polarity in the data pattern and up-converting the data of the thermal queuing in the data pattern. Equipped; The potential difference between the sum of the analog data voltages corresponding to the dominant polarities of the data and the common voltage is equal to the potential difference between the sum of the analog data voltages corresponding to the thermopolarity of the data and the common voltage. The amount of down conversion and the amount of up conversion are controlled.

The data pattern detector may include a comparator configured to compare polarities of the input digital data; A gray level detector for detecting a gray level of each of the input digital data; And a data pattern determination unit determining whether the data pattern is based on the polarity comparison and the gray level detection result.

The data converter may include: a dominant polarity determining unit configured to determine dominant polarity of digital data in the data pattern; And a data converter configured to down-convert the grayscale value of the dominant polarity data and upconvert the grayscale value of the thermofine data in the data pattern.

In the first embodiment of the present invention, the down conversion amount and the up conversion amount are the same.

The data pattern may include odd-numbered odd pixel digital data including R digital data of a first polarity, G digital data of a second polarity, and B digital data of the first polarity; And second grayscale even pixel digital data including R digital data of the second polarity, G digital data of the first polarity, and B digital data of the second polarity; The sum of analog data voltages corresponding to the digital data having the first polarity among the odd and even pixel digital data and the analog data corresponding to the digital data having the second polarity among the odd and even pixel data. The voltage difference of the sum of the voltages may be greater than or equal to a predetermined threshold.

The data pattern may include: 4k + 1th pixel digital data of a first gray level including R digital data of a first polarity, G digital data of the first polarity, and B digital data of a second polarity; 4k + 2th pixel digital data of the first gray level, including R digital data of the second polarity, G digital data of the first polarity, and B digital data of the first polarity; 4k + 3th pixel digital data of a second gray level including R digital data of the second polarity, G digital data of the second polarity, and B digital data of the first polarity; And 4k + 4th pixel digital data of the second gray level, including R digital data of the first polarity, G digital data of the second polarity, and B digital data of the second polarity; The sum of analog data voltages corresponding to the digital data having the first polarity among the 4k + 1st to 4k + 4th pixel digital data and the 4k + 1st to 4k + 4th pixel digital data The voltage difference between the sum of the analog data voltages corresponding to the digital data having the second polarity is greater than or equal to a predetermined threshold.

The threshold is characterized in that 0.1 V.

When the first polarity is positive, the second polarity is negative, and the first gray level is higher than the second gray level, the data conversion unit down-converts the gray value of the digital data having the positive polarity and the negative polarity. Characterized in that the up-conversion of the gray value of the digital data having a.

If the first polarity is positive, the second polarity is negative, and the first gray level is lower than the second gray level, the data conversion unit up-converts the gray value of the digital data having the positive polarity and performs the negative polarity. Down converting the gray value of the digital data having a.

If the first polarity is negative, the second polarity is positive, and the first gray level is higher than the second gray level, the data conversion unit up-converts the gray value of the digital data having the positive polarity and performs the negative polarity. It characterized in that the down conversion of the gray value of the digital data.

If the first polarity is negative, the second polarity is positive, and the first gray level is lower than the second gray level, the data conversion unit down-converts the gray value of the digital data having the positive polarity and performs the negative polarity. Characterized in that the up-conversion of the gray value of the digital data having a.

In a second embodiment of the present invention, the down conversion amount is smaller than the up conversion amount.

The data pattern may include: 4k + 1th pixel digital data of a first gray level including R digital data of a first polarity, G digital data of the first polarity, and B digital data of a second polarity; 4k + 2th pixel digital data of the first gray level, including R digital data of the second polarity, G digital data of the first polarity, and B digital data of the first polarity; 4k + 3th pixel digital data of a second gray level including R digital data of the second polarity, G digital data of the second polarity, and B digital data of the first polarity; And 4k + 4th pixel digital data of the second gray level, including R digital data of the first polarity, G digital data of the second polarity, and B digital data of the second polarity; The sum of analog data voltages corresponding to the digital data having the first polarity among the 4k + 1st to 4k + 4th pixel digital data and the 4k + 1st to 4k + 4th pixel digital data The voltage difference between the sum of the analog data voltages corresponding to the digital data having the second polarity is greater than or equal to a predetermined threshold.

The data pattern may include odd-numbered odd pixel digital data including R digital data of a first polarity, G digital data of a second polarity, and B digital data of the first polarity; And second grayscale even pixel digital data including R digital data of the second polarity, G digital data of the first polarity, and B digital data of the second polarity; The sum of analog data voltages corresponding to the digital data having the first polarity among the odd and even pixel digital data and the analog data corresponding to the digital data having the second polarity among the odd and even pixel data. The voltage difference of the sum of the voltages may be greater than or equal to a predetermined threshold.

According to an exemplary embodiment of the present invention, the digital data is converted into an analog data voltage and the polarity of the analog data voltage is controlled relative to the common voltage to supply the analog data voltages of the positive polarity and the analog data voltages of the negative polarity to the data lines to display an image. A driving method of a liquid crystal display device includes: detecting a data pattern including data among at least two or more data neighboring in a horizontal direction among input digital data and even having a periodicity; And determining the polarity of the data having the relatively higher polarity among the data having the higher gray level in the data pattern as the dominant polarity, and down converting the dominant polarity data and upconverting the thermofine data in the data pattern. and; The potential difference between the sum of the analog data voltages corresponding to the dominant polarities of the data and the common voltage is equal to the potential difference between the sum of the analog data voltages corresponding to the thermopolarity of the data and the common voltage. The amount of down conversion and the amount of up conversion are controlled.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 5 through 12B.

5 is a configuration diagram of a liquid crystal display according to the present invention.

Referring to FIG. 5, the liquid crystal display device of the present invention includes a liquid crystal panel 67 in which a data line 65 and a gate line 66 cross each other, and a TFT for driving the liquid crystal cell Clc is formed at an intersection thereof. A data driver circuit 63 for supplying a data voltage to the data line 65 of the liquid crystal panel 67 and a gate driver circuit 64 for supplying a scanning pulse to the gate line 66 of the liquid crystal panel 67. ), The timing controller 61 to which the digital data Data and the synchronization signals H and V are supplied, and the timing controller 61 and the data driving circuit 63 to connect the input digital data RiGiBi. A data conversion circuit 62 for conversion is provided.

In the liquid crystal panel 67, liquid crystal is injected between two glass substrates, and the data lines 65 and the gate lines 66 are orthogonal to each other on the lower glass substrate. The TFT formed at the intersection of the data lines 65 and the gate lines 66 supplies the data voltages on the data lines 65 to the liquid crystal cell Clc in response to the scan pulse. For this purpose, the gate electrode of the TFT is connected to the gate line 66 and the source electrode is connected to the data line 65. The drain electrode of the TFT is connected to a pixel electrode (not shown) of the liquid crystal cell Clc. The liquid crystal cell Clc is charged with the potential difference between the data voltage supplied to the pixel electrode and the common voltage supplied to the common electrode (not shown), and the amount of light transmitted through the change of the arrangement of the liquid crystal molecules by the electric field formed by the potential difference. Control or block the light. The common electrode may be formed on the upper substrate or the lower substrate of the liquid crystal display panel according to a method of applying an electric field to the liquid crystal cell Clc, and the liquid crystal cell Clc is charged between the common electrode and the pixel electrode of the liquid crystal cell Clc. A storage capacitor is formed to maintain the voltage.

The timing controller 61 rearranges digital data Data supplied from a digital video card (not shown). The data RiGiBi rearranged by the timing controller 61 is supplied to the data conversion circuit 62. In addition, the timing controller 61 uses the clock signal CLK and the horizontal / vertical synchronization signals H and V input thereto, and the gate control signal GDC and the data driving circuit for controlling the gate driving circuit 64. A data control signal DDC for controlling the furnace 63 is generated. The gate control signal GDC includes a gate shift clock GSC, a gate output signal GOE, a gate start pulse GSP, and the like. The data control signal DDC includes a source start pulse SSP, a source shift clock SSC, a source output signal SOE, a polarity signal POL, and the like.

The gate driving circuit 64 may include a shift register that sequentially generates scan pulses, that is, gate high pulses, in response to the gate control signal GDC supplied from the timing controller 61, and outputs a voltage of the scan pulses to the liquid crystal cell Clc. And a level shifter for shifting to a level suitable for driving. The TFT is turned on in response to this scan pulse. When the TFT is turned on, the data voltage on the data line 65 is supplied to the pixel electrode of the liquid crystal cell Clc.

The data conversion circuit 62 detects a data pattern among the input digital data RiGiBi including at least two data adjacent to each other in the horizontal direction and including data having periodicity. The data conversion circuit 62 judges the polarity of the data having the relatively higher polarity as the dominant polarity among the data having the higher gradation in the data pattern, and based on the determination result, the data having the dominant polarity in the data pattern is determined. Down-convert and up-convert thermotropic data. The amount up-converted and the amount down-converted can be adjusted to prevent the swing of the common voltage in the data pattern. The converted digital data RoGoBo is supplied to the data driving circuit 63. The data conversion circuit 62 will be described in detail with reference to FIG. 6.

The data driving circuit 63 is supplied with modulated data RoGoBo of red (R), green (G), and blue (B) colors modulated by the data conversion circuit 62, and the timing controller 61. The data control signal DDC is inputted from the. The data driving circuit 63 latches the modulated data RoGoBo of red (R), green (G), and blue (B) colors by one line after sampling according to the data control signal DDC. The data latched by this data driving circuit 63 is converted into an analog data voltage and simultaneously supplied to the data lines 65 in every scan period. The data driving circuit 63 may supply a gamma voltage corresponding to the modulated data to the data line 65.

6 shows the data conversion circuit 62 of FIG.

Referring to FIG. 6, the data conversion circuit 62 includes a line memory 160, a data pattern detector 162, and a data converter 164.

The line memory 160 is connected to the timing controller 61 to store digital data RiGiBi input from the timing controller 61 in one horizontal line unit. The line memory 81 supplies digital data RiGiBi stored in units of horizontal lines to the data pattern detector 162. The line memory 81 may be embodied as a random access memory (RAM).

The data pattern detector 162 detects a data pattern Ri1Gi1Bi1 including data in which there is even a system between at least two or more neighboring data in the horizontal direction among the input digital data RiGiBi, and even the system has periodicity. . To this end, the data detector 162 includes a gray scale detector 162-1, a polarity comparator 162-2, and a data pattern plate end 162-3.

The gray level detector 162-1 reads the digital value of the input digital data RiGiBi for one line and detects the gray level of each of the data. For example, the gray scale detection unit 162-1 may detect data having a digital value of 11001101 as 205 gray levels and data having a digital value of 00110010 as 50 gray levels in the case of 8-bit data.

The polarity comparator 162-2 synchronizes the input digital data RiGiBi for one line with the polarity signal POL from the timing controller 61 in one-to-one synchronization and compares the polarities of the input digital data RiGiBi. .

The data pattern determination unit 162-3 determines whether the gray value is a data pattern to be converted based on the gray level G from the gray level detection unit 162-1 and the polarity P from the polarity comparison unit 162-2. Judge. The data pattern determination unit 162-3 may determine whether the data pattern is performed by using an algorithm for converting grayscales of digital data into analog data voltages. The data pattern determination unit 162-3 may include the sum of the analog data sums corresponding to the digital data having the positive polarity and the analog data corresponding to the negative digital data among the digital data to be supplied to one horizontal line. If the voltage difference of the sum of the data sums is greater than or equal to a predetermined threshold, it is determined that the digital data includes the data pattern. Further, even the system between at least two adjacent data recognizes the array of data having periodicity as the data pattern to which the gray value should be converted. Here, the threshold is approximately 0.1 V, which is the minimum voltage causing the swing of the common voltage. The digital data Ri1, Gi1, and Bi1 determined as the data pattern are supplied to the data converter 164, and the digital data Ri2, Gi2, and Bi2 not determined as the data pattern are supplied to the data driving circuit.

The data converter 164 derives the dominant polarity of the digital data Ri1, Gi1, and Bi1 included in the data pattern. The data converter 164 down-converts the dominant polarity data and up-converts the thermotropical data. To this end, the data converter 164 includes a dominant polarity determining unit 164-1 and a data converter 164-2. The dominant polarity determining unit 164-1 determines the polarity of the data having the relatively higher polarity among the data having the higher gray levels in the data pattern as the dominant polarity. The data converter 164-2 lowers the gradation value of the dominant data in the data pattern based on this dominance and increases the gradation value of the data of the thermopolarity. By the conversion of the gray scale values, the potential difference between the sum of analog data voltages corresponding to the dominant data and the common voltage is equal to the potential difference between the sum of analog data voltages corresponding to the thermopolar data and the common voltage. Will be the same. The down conversion amount and the up conversion amount by the data converter 164-2 may be equally or differently adjusted depending on the case. This will be described in detail through the first and second embodiments of the present invention. The digital data RoGoBo having the gray level converted by the data converter 164-2 is supplied to the data driving circuit.

7A and 7B show an example of a data pattern according to the present invention. 8A and 8B illustrate liquid crystals disposed in the i-th horizontal line Hi and the i + 1-th horizontal line Hi + 1 after digital data in the data patterns shown in FIGS. 7A and 7B are converted into analog data voltages. It shows the average level of these data voltages when supplied to cells (sub pixels).

The data pattern shown in FIG. 7A is a data pattern in which white (W)-white (W)-black (B)-black (B) patterns are displayed on each pixel including three subpixels of R, G, and B. to be. It is assumed that the white gray W is 205 gray and the black gray B is 50 gray. The polarities of the digital data forming the data pattern are determined such that the subpixels are driven in a horizontal two dot inversion scheme.

The data pattern shown in FIG. 7B is a data pattern in which white (W)-black (B)-white (W)-black (B) patterns are displayed on each pixel including three subpixels of R, G, and B. to be. It is assumed that the white gray W is 205 gray and the black gray B is 50 gray. The polarities of the digital data forming the data pattern are determined such that the subpixels are driven in a dot inversion method.

7A and 7B, the polarities of data having relatively high polarity among data having high gray levels in the data pattern adjacent in the horizontal direction become dominant polarity. Since the digital data of the positive polarity is relatively contained in the white pattern to be supplied to the i-th horizontal line Hi, the dominant polarity of the digital data to be supplied to the i-th horizontal line Hi becomes positive. In addition, since a large amount of negative digital data is included in the white pattern to be supplied to the i + 1th horizontal line Hi + 1, the digital data to be supplied to the i + 1th horizontal line Hi + 1 is included. The dominant polarity becomes negative. The determination of the dominant polarity is made by the dominant polarity determination unit 164-1 in the data converter 164, as described with reference to FIG.

According to the dominant polarity, the average data voltage value of the digital data for each horizontal line is biased toward the positive or negative polarity based on the common voltage. The average level Vd of the data voltage supplied to the i-th horizontal line Hi is biased toward the positive polarity with respect to the common voltage Vcom, as shown in FIG. 8A. The average level Vd of the data voltage supplied to the i + 1th horizontal line Hi + 1 is biased toward the negative polarity (−) based on the common voltage Vcom, as shown in FIG. 8B. When the average level Vd of the data voltage is biased toward one polarity based on the common voltage Vcom, the common voltage Vcom swings toward the dominant polarity as described in the related art. In an embodiment of the present invention, the digital data in the data pattern is converted such that the positive data voltage and the negative data voltage are symmetrical with respect to the common voltage Vcom in order to prevent the swing of the common voltage Vcom. That is, among the digital data constituting the data pattern, data having the same polarity as the dominant polarity is down-converted, and data having a polarity different from the dominant polarity (hereinafter, referred to as "thermal polarity") is up-converted.

9A and 9B show a change in the average level of the data voltage supplied to the horizontal line corresponding to the digital data converted according to the first embodiment of the present invention. In the first embodiment of the present invention, the down conversion amount and the up conversion amount are the same.

7A and 7B, since the dominant polarity of the digital data supplied to the i-th horizontal line Hi is positive, the data converter 164-2 in the data converter 164 supplies the i-th horizontal line Hi. Down-convert the positive digital data among the digital data, and up-convert the negative digital data. The average level Vd of the positive data voltage and the average level Vd of the negative data voltage are symmetrical with respect to the common voltage by the data conversion through the data converter 164-2, as shown in FIG. 9A. It is worn. During data conversion by the data converter 164-2, the down conversion amount and the up conversion amount are the same.

7A and 7B, since the dominant polarity of the digital data supplied to the i + 1 th horizontal line Hi + 1 is negative, the data converter 164-2 in the data converter 164 has the i + 1 th horizontal. Down-convert the negative digital data among the digital data supplied to the line Hi + 1 and up-convert the positive digital data. The average level Vd of the positive data voltage and the average level Vd of the negative data voltage are symmetrical with respect to the common voltage by data conversion through the data converter 164-2, as shown in FIG. 9B. It is worn. During data conversion by the data converter 164-2, the down conversion amount and the up conversion amount are the same.

As in the first embodiment of the present invention, by converting the digital data in the data pattern, it is possible to prevent the swing of the common voltage due to the data pattern, thereby eliminating the cause of horizontal crosstalk.

10A to 12B are views for explaining a second embodiment of the present invention.

10A and 10B show color distortion when the first embodiment of the present invention is applied to the data pattern shown in FIG. 7A. 10A and 10B illustrate a conversion amount of digital data forming a black pattern rather than a conversion amount of digital data forming a white pattern in order to prevent such color distortion according to the second embodiment of the present invention. Show enlargement. For reference, the amount of change shown in FIGS. 10A and 10B is proportional to the number of arrows.

As in the first embodiment, if down / up-conversion of digital data biased with positive or negative polarity is performed in the same amount, horizontal crosstalk can be eliminated by preventing the swing of the common voltage, but this causes color distortion. .

In detail, when the digital data are converted as in the first embodiment of FIG. 10A (a), all analog data voltages corresponding to the digital data are lowered. Due to the reduction of the data voltages, the brightness of the positive data voltages is decreased, and the brightness of the negative data voltages is increased. In addition, when the digital data are converted as in the first embodiment of FIG. 10B (a), all analog data voltages corresponding to the digital data are increased. As the data voltages increase, the luminance of the positive data voltages increases, and the luminance of the negative data voltages decreases. Among the data voltages forming the white pattern, since the R and B data voltages are positive and negative, they cancel each other and do not affect the R and B brightness changes. However, since the G data voltages are all negative, the G brightness is large. Will fall. Due to the decrease in the G luminance, the R and B luminances increase relatively in the white pattern, and the color of the white pattern changes to purple. Among the data voltages forming the black pattern, the R and B data voltages have positive and negative polarities, so they cancel each other and do not affect the change of the R and B luminance. However, since the G data voltages are all positive, the G luminance is large. Will increase. In this black pattern, the G luminance increases, so that the color of the black pattern turns green. As a result, the white pattern looks purple and the black pattern looks green due to the color distortion caused by the luminance change. In this case, since the white pattern having a high gradation has more influence on color distortion than the black pattern having a low gradation, the date patterns of FIGS. 10A and 10B have a purple color as a whole.

In the second embodiment of the present invention, the above-mentioned color distortion is prevented by changing the conversion amount of the digital data in the white pattern and the conversion amount of the digital data in the black pattern.

That is, in the second embodiment of the present invention, the conversion amount of the digital data forming the black pattern is larger than the conversion amount of the digital data forming the white pattern as shown in FIGS. 10A and 10B. This is to balance the G luminance decrease (relative R, B luminance increase) in the white pattern by increasing the G luminance in the black pattern which has a relatively less effect on color distortion. Increasing the conversion amount of digital data in the black pattern compared to the white pattern means that the conversion amount of the dominant digital data is small, and the conversion amount of the digital data of the thermostriplarity is large. Of course, the average level of the analog data voltages corresponding to the converted digital data should be symmetrical with respect to the common voltage.

11A and 11B show color distortion when the first embodiment of the present invention is applied to the data pattern shown in FIG. 7B. 11A and 11B illustrate a conversion amount of digital data forming a black pattern rather than a conversion amount of digital data forming a white pattern in order to prevent such color distortion according to the second embodiment of the present invention. Show enlargement. For reference, the amount of change shown in FIGS. 11A and 11B is proportional to the number of arrows.

As in the first embodiment, if down / up-conversion of digital data biased with positive or negative polarity is performed in the same amount, horizontal crosstalk can be eliminated by preventing the swing of the common voltage, but this causes color distortion. .

In detail, when the digital data are converted as in the first embodiment of FIG. 11A (a), all analog data voltages corresponding thereto are lowered. Due to the reduction of the data voltages, the brightness of the positive data voltages is decreased, and the brightness of the negative data voltages is increased. In addition, when converting the digital data as in the first embodiment in (a) of FIG. 11B, all analog data voltages corresponding to the digital data are increased. As the data voltages increase, the luminance of the positive data voltages increases, and the luminance of the negative data voltages decreases. In the white pattern, the R and B luminances decrease and the G luminance increases, so that the color of the white pattern changes to green. In the black pattern, the G luminance decreases and the R and B luminance increase, so that the color of the black pattern turns purple. As a result, the white pattern looks green and the black pattern looks purple due to the color distortion caused by the luminance change. At this time, since the white pattern having a high gradation has more influence on color distortion than the black pattern having a low gradation, the date patterns of FIGS. 11A and 11B have a green color as a whole.

In the second embodiment of the present invention, the above-mentioned color distortion is prevented by changing the conversion amount of the digital data in the white pattern and the conversion amount of the digital data in the black pattern.

That is, in the second embodiment of the present invention, the conversion amount of the digital data forming the black pattern is larger than the conversion amount of the digital data forming the white pattern as shown in FIGS. 11A and 11B. This is to balance the increase in the G luminance in the white pattern by increasing the R, B luminance in the black pattern which has a relatively less effect on the color distortion. Increasing the conversion amount of digital data in the black pattern compared to the white pattern means that the conversion amount of the dominant digital data is small, and the conversion amount of the digital data of the thermostriplarity is large. Of course, the average level of the analog data voltages corresponding to the converted digital data should be symmetrical with respect to the common voltage.

FIG. 12A illustrates a change in the average level Vd of the data voltage supplied to the i-th horizontal line Hi corresponding to FIGS. 10A and 11B, and FIG. 12B is a block diagram of FIG. 11B shows a change in the average level Vd of the data voltage supplied to the i + 1th horizontal line Hi + 1, corresponding to (b) of FIG. 11B.

Since the dominant polarity of the digital data supplied to the i-th horizontal line Hi is positive, the data converter 164-2 in the data converter 164 has a positive polarity among the digital data supplied to the i-th horizontal line Hi. Down converts the polar digital data and up converts the negative digital data. The data converter 164-2 may reduce the amount of down conversion for the positive digital data to be less than the amount of upconversion for the negative digital data in order to prevent the color distortion described above. The average level (Vd) of the positive data voltage and the average level (Vd) of the negative data voltage are symmetrical with respect to the common voltage (Vcom) as shown in FIG. 12A, but the amount of change of the average level through data conversion is The negative polarity is greater than the positive polarity.

Since the dominant polarity of the digital data supplied to the i + 1th horizontal line Hi + 1 is negative, the data converter 164-2 in the data converter 164 performs the i + 1th horizontal line Hi + 1. Down-convert the negative digital data among the digital data supplied to the up-convert, and up-convert the positive digital data. The data conversion unit 164-2 reduces the down conversion amount for the negative digital data to be smaller than the up conversion amount for the positive digital data in order to prevent the color distortion described above. The average level Vd of the positive data voltage and the average level Vd of the negative data voltage are symmetrical with respect to the common voltage Vcom as shown in FIG. 12B, but the amount of change of the average level through data conversion is It is larger in the positive polarity than the negative polarity.

As described above, the liquid crystal display and the driving method thereof according to the present invention can cause the horizontal crosstalk to be generated by up-converting or down-converting the grayscale values of digital data in a specific data pattern so that the common voltage does not swing. Can be removed

Furthermore, the liquid crystal display and the driving method thereof according to the present invention up-convert or down-convert the gray value of digital data in a specific data pattern to prevent the common voltage from swinging, but adjust the amount of up-conversion and the amount of down-conversion. Therefore, color distortion in a specific data pattern can be prevented.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (33)

A liquid crystal display for converting digital data into analog data voltages and controlling the polarity of the analog data voltages relative to a common voltage to supply positive analog data voltages and negative analog data voltages to data lines to display an image. A data pattern detector for detecting a data pattern including data having at least two systems neighboring in a horizontal direction among the received digital data and having a periodicity; And And a data converter which down-converts the dominant data in the data pattern and up-converts the thermo-fine data in the data pattern by judging the polarity of the data having the relatively high polarity among the data having a high gradation in the data pattern. and; The potential difference between the sum of the analog data voltages corresponding to the dominant polarities of the data and the common voltage is equal to the potential difference between the sum of the analog data voltages corresponding to the thermopolarity of the data and the common voltage. And the down conversion amount and the up conversion amount are controlled. The method of claim 1, The data pattern detector, A comparator for comparing polarities of the input digital data; A gray level detector for detecting a gray level of each of the input digital data; And And a data pattern determination unit determining whether the data pattern is based on the polarity comparison and the gray level detection result. The method of claim 2, The data converter, A predominance polarity determining unit which determines a predominance polarity of the digital data in the data pattern; And And a data converter configured to down-convert the gradation value of the dominant polarity data and up-convert the gradation value of the thermofine data in the data pattern. The method of claim 3, wherein And the down conversion amount and the up conversion amount are the same. The method of claim 4, wherein The data pattern is, Odd-numbered odd pixel digital data including R digital data of a first polarity, G digital data of a second polarity, and B digital data of the first polarity; And A second grayscale pixel digital data including R digital data of the second polarity, G digital data of the first polarity, and B digital data of the second polarity; The sum of analog data voltages corresponding to the digital data having the first polarity among the odd and even pixel digital data and the analog data corresponding to the digital data having the second polarity among the odd and even pixel data. And the voltage difference of the sum of the voltages is greater than or equal to a predetermined threshold. The method of claim 5, wherein And the threshold is 0.1V. The method of claim 6, If the first polarity is positive and the second polarity is negative and the first gray level is higher than the second gray level, And the data conversion unit down converts the gray value of the digital data having the positive polarity and up converts the gray value of the digital data having the negative polarity. The method of claim 6, When the first polarity is positive and the second polarity is negative and the first gray level is lower than the second gray level, And the data converter up-converts the gray value of the digital data having the positive polarity and down converts the gray value of the digital data having the negative polarity. The method of claim 6, If the first polarity is negative and the second polarity is positive and the first gray level is higher than the second gray level, And the data converter up-converts the gray value of the digital data having the positive polarity and down converts the gray value of the digital data having the negative polarity. The method of claim 6, When the first polarity is negative and the second polarity is positive and the first gray level is lower than the second gray level, And the data conversion unit down converts the gray value of the digital data having the positive polarity and up converts the gray value of the digital data having the negative polarity. The method of claim 4, wherein The data pattern is, 4k + 1th pixel digital data of a first gray level including R digital data of a first polarity, G digital data of the first polarity, and B digital data of the second polarity; 4k + 2th pixel digital data of the first gray level, including R digital data of the second polarity, G digital data of the first polarity, and B digital data of the first polarity; 4k + 3th pixel digital data of a second gray level including R digital data of the second polarity, G digital data of the second polarity, and B digital data of the first polarity; And 4k + 4th pixel digital data of the second gray level, including R digital data of the first polarity, G digital data of the second polarity, and B digital data of the second polarity; The sum of analog data voltages corresponding to the digital data having the first polarity among the 4k + 1st to 4k + 4th pixel digital data and the 4k + 1st to 4k + 4th pixel digital data The voltage difference of the sum of the analog data voltages corresponding to the digital data having the second polarity is greater than or equal to a predetermined threshold. The method of claim 11, And the threshold is 0.1V. The method of claim 12, If the first polarity is positive and the second polarity is negative and the first gray level is higher than the second gray level, And the data conversion unit down converts the gray value of the digital data having the positive polarity and up converts the gray value of the digital data having the negative polarity. The method of claim 12, When the first polarity is positive and the second polarity is negative and the first gray level is lower than the second gray level, And the data converter up-converts the gray value of the digital data having the positive polarity and down converts the gray value of the digital data having the negative polarity. The method of claim 12, If the first polarity is negative and the second polarity is positive and the first gray level is higher than the second gray level, And the data converter up-converts the gray value of the digital data having the positive polarity and down converts the gray value of the digital data having the negative polarity. The method of claim 12, If the first polarity is negative and the second polarity is positive and the first gray level is lower than the second gray level, And the data conversion unit down converts the gray value of the digital data having the positive polarity and up converts the gray value of the digital data having the negative polarity. The method of claim 3, wherein Wherein the amount of down conversion is less than the amount of up conversion. The method of claim 17, The data pattern is, 4k + 1th pixel digital data of a first gray level including R digital data of a first polarity, G digital data of the first polarity, and B digital data of the second polarity; 4k + 2th pixel digital data of the first gray level, including R digital data of the second polarity, G digital data of the first polarity, and B digital data of the first polarity; 4k + 3th pixel digital data of a second gray level including R digital data of the second polarity, G digital data of the second polarity, and B digital data of the first polarity; And 4k + 4th pixel digital data of the second gray level, including R digital data of the first polarity, G digital data of the second polarity, and B digital data of the second polarity; The sum of analog data voltages corresponding to the digital data having the first polarity among the 4k + 1st to 4k + 4th pixel digital data and the 4k + 1st to 4k + 4th pixel digital data The voltage difference of the sum of the analog data voltages corresponding to the digital data having the second polarity is greater than or equal to a predetermined threshold. The method of claim 18, And the threshold is 0.1V. The method of claim 19, If the first polarity is positive and the second polarity is negative and the first gray level is higher than the second gray level, And the data conversion unit down converts the gray value of the digital data having the positive polarity and up converts the gray value of the digital data having the negative polarity. The method of claim 19, When the first polarity is positive and the second polarity is negative and the first gray level is lower than the second gray level, And the data converter up-converts the gray value of the digital data having the positive polarity and down converts the gray value of the digital data having the negative polarity. The method of claim 19, If the first polarity is negative and the second polarity is positive and the first gray level is higher than the second gray level, And the data converter up-converts the gray value of the digital data having the positive polarity and down converts the gray value of the digital data having the negative polarity. The method of claim 19, When the first polarity is negative and the second polarity is positive and the first gray level is lower than the second gray level, And the data conversion unit down converts the gray value of the digital data having the positive polarity and up converts the gray value of the digital data having the negative polarity. The method of claim 17, The data pattern is, Odd-numbered odd pixel digital data including R digital data of a first polarity, G digital data of a second polarity, and B digital data of the first polarity; And A second grayscale pixel digital data including R digital data of the second polarity, G digital data of the first polarity, and B digital data of the second polarity; The sum of analog data voltages corresponding to the digital data having the first polarity among the odd and even pixel digital data and the analog data corresponding to the digital data having the second polarity among the odd and even pixel data. And the voltage difference of the sum of the voltages is greater than or equal to a predetermined threshold. The method of claim 24, And the threshold is 0.1V. The method of claim 25, If the first polarity is positive and the second polarity is negative and the first gray level is higher than the second gray level, And the data conversion unit down converts the gray value of the digital data having the positive polarity and up converts the gray value of the digital data having the negative polarity. The method of claim 25, When the first polarity is positive and the second polarity is negative and the first gray level is lower than the second gray level, And the data converter up-converts the gray value of the digital data having the positive polarity and down converts the gray value of the digital data having the negative polarity. The method of claim 25, If the first polarity is negative and the second polarity is positive and the first gray level is higher than the second gray level, And the data converter up-converts the gray value of the digital data having the positive polarity and down converts the gray value of the digital data having the negative polarity. The method of claim 25, When the first polarity is negative and the second polarity is positive and the first gray level is lower than the second gray level, And the data conversion unit down converts the gray value of the digital data having the positive polarity and up converts the gray value of the digital data having the negative polarity. A method of driving a liquid crystal display device for converting digital data into analog data voltages and controlling the polarity of the analog data voltages relative to a common voltage to supply positive analog data voltages and negative analog data voltages to data lines to display an image. To Detecting a data pattern including data among the received digital data, wherein a system exists between at least two adjacent data in a horizontal direction and even the system has periodicity; And Determining the polarity of the data having the relatively higher polarity among the data having the higher gradation in the data pattern as the dominant polarity, and down converting the dominant polarity data in the data pattern and upconverting the thermal tripolar data. ; The potential difference between the sum of the analog data voltages corresponding to the dominant polarities of the data and the common voltage is equal to the potential difference between the sum of the analog data voltages corresponding to the thermopolarity of the data and the common voltage. And a down conversion amount and an up conversion amount are controlled. The method of claim 30, Detecting the data pattern, Comparing the polarity of each of the input digital data; Detecting a gray level of each of the input digital data; And And determining whether the data pattern is based on the result of the polarity comparison and the gray level detection. The method of claim 31, wherein And the down conversion amount and the up conversion amount are the same. The method of claim 31, wherein And the down conversion amount is less than the up conversion amount.

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