KR20100064933A - Liquid crystal display and driving method thereof - Google Patents

Abstract

PURPOSE: A liquid crystal display and a driving method thereof are provided to improve the response characteristics without noise by dividing the amount of over driving into adjacent cells through a time division method. CONSTITUTION: A memory stores previous frame data. The overdrive modulator compares a previous frame data with a current frame data. The overdrive modulator modulates the current frame data. An operation unit generates first correction data and second correction data. The first correction data is higher than the output of the overdrive modulator. The second correction data is lower than the output of the overdrive modulator. A selecting unit selects the first and second correction data as data to be successively provided to the first liquid crystal cell. The selecting unit selects the first and second correction data as data to be successively provided to the second liquid crystal cell.

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY AND DRIVING METHOD THEREOF}

The present invention relates to a liquid crystal display and a driving method thereof.

The flat panel display includes a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an organic light emitting diode display (OLED). ).

Liquid crystal display devices can meet the trend of light and short and short of electronic products and mass production is improving, and are rapidly replacing cathode ray tubes in many applications. An active matrix type liquid crystal display device that drives a liquid crystal cell using a thin film transistor (hereinafter referred to as "TFT") has the advantages of high image quality and low power consumption. As a result of development, it is rapidly developing in size and high resolution, and is rapidly replacing the cathode ray tube in television (hereinafter referred to as "TV") and monitor. However, the liquid crystal display device has a disadvantage in that the response speed is slow due to the inherent viscosity and elasticity of the liquid crystal as shown in Equations 1 and 2.

(gamma)는 액정분자의 회전점도(rotational viscosity)를 각각 의미한다. Where τ _r is the rising time when voltage is applied to the liquid crystal, V _a is the applied voltage, and V _F is the Freederick Transition Voltage at which the liquid crystal molecules begin their inclined motion. d is the cell gap of the liquid crystal cell,

(gamma) means rotational viscosity of liquid crystal molecules, respectively.

Here, _f denotes a falling time for the liquid crystal to return to its original position after the voltage applied to the liquid crystal is turned off, and K denotes an elastic modulus inherent in the liquid crystal.

The liquid crystal response speed of TN mode (Twisted Nematic mode), which has been the most commonly used liquid crystal display device, may vary depending on the physical properties of the liquid crystal material and the cell gap. 30 ms. The response speed of the liquid crystal is longer than one frame period (NTSC: 16.67ms). For this reason, as shown in FIG. 1, since the voltage charged in the liquid crystal cell reaches the next frame, motion blur occurs in the video.

Referring to FIG. 1, when the data VD changes from one level to another due to the slow response speed of the liquid crystal, the corresponding display luminance BL may not reach the desired luminance and thus may not display the desired color and luminance. do. As a result, the liquid crystal display device is deteriorated in image quality because motion blur appears in the video.

In order to solve the slow response speed of the liquid crystal display device, U.S. Patent No. 5,495,265 and PCT International Publication No. WO 99/05567 use a look-up table to modulate the data according to the change of data. Over driving control (ODC) has been proposed. The overdrive method modulates data on the same principle as in FIG. 2.

을 크게 하여 액정의 응답특성을 빠르게 한다. 따라서, 과구동 방법으로 구동되는 액정표시장치는 액정의 늦은 응답속도를 데이터값의 변조로 보상하여 동영상에서 모션 블러를 줄일 수 있다. Referring to FIG. 2, the overdrive method modulates the input data voltage VD into a preset voltage MVD of modulated data and applies the modulated data voltage MVD to a liquid crystal cell to obtain a desired luminance MBL. do. The overdrive method is expressed by Equation 1 based on the change of data so as to obtain a desired luminance (MBL) within one frame period.

Increase the response speed of the liquid crystal. Accordingly, the liquid crystal display device driven by the overdrive method may reduce motion blur in the video by compensating for the late response speed of the liquid crystal by modulation of the data value.

This overdrive method compares data between the previous frame and the current frame, and if there is a change between the data, modulates data of the current frame with preset modulation data.

3 is a block diagram schematically illustrating an overdrive circuit.

Referring to FIG. 3, the overdrive circuit includes first and second frame memories 33a and 33b for storing data from the data input bus 32 and a lookup table 34 for modulating the data. .

The first and second frame memories 33a and 33b alternately store data in units of frames in accordance with the pixel clock, alternately output the stored data, and output the previous frame data, that is, the n-1 th frame data, to the lookup table 34. (Fn-1) is supplied.

The lookup table 34 stores n-th frame data Fn from the n-th frame data Fn and the first and second frame memories 33a and 33b as shown in Table 1 below. The data is modulated by selecting a modulation value, using () as the address. The lookup table 34 includes a read only memory (ROM) and a memory control circuit.

division 0 One 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 0 2 3 4 5 6 7 9 10 12 13 14 15 15 15 15 One 0 One 3 4 5 6 7 8 10 12 13 14 15 15 15 15 2 0 0 2 4 5 6 7 8 10 12 13 14 15 15 15 15 3 0 0 One 3 5 6 7 8 10 11 13 14 15 15 15 15 4 0 0 One 3 4 6 7 8 9 11 12 13 14 15 15 15 5 0 0 One 2 3 5 7 8 9 11 12 13 14 15 15 15 6 0 0 One 2 3 4 6 8 9 10 12 13 14 15 15 15 7 0 0 One 2 3 4 5 7 9 10 11 13 14 15 15 15 8 0 0 One 2 3 4 5 6 8 10 11 12 14 15 15 15 9 0 0 One 2 3 4 5 6 7 9 11 12 13 14 15 15 10 0 0 One 2 3 4 5 6 7 8 10 12 13 14 15 15 11 0 0 One 2 3 4 5 6 7 8 9 11 13 14 15 15 12 0 0 One 2 3 4 5 6 7 8 9 10 12 14 15 15 13 0 0 One 2 3 3 4 5 6 7 8 10 11 13 15 15 14 0 0 One 2 3 3 4 5 6 7 8 9 11 12 14 15 15 0 0 0 One 2 3 3 4 5 6 7 8 9 11 13 15

In Table 1, the leftmost column is data of the previous frame Fn-1, and the uppermost row is data of the current frame Fn.

During the nth frame period, the nth frame data Fn is stored in the first frame memory 33a and supplied to the lookup table 34 at the same pixel clock as indicated by the solid line. At the same time, the second frame memory 33b supplies the n−1 th frame data Fn−1 to the lookup table 34 during the n th frame period.

During the n + 1 th frame period, the current n + 1 th frame data Fn + 1 is stored in the second frame memory 33b and supplied to the lookup table 34 at the same pixel clock as indicated by the dotted line. do. At the same time, the first frame memory 33a supplies the nth frame data Fn to the lookup table 34 during the n + 1th frame period.

However, in the overdrive method, in order to increase the response speed of the liquid crystal, if the modulation width of the data modulation is increased, that is, the overdrive ratio is increased, the overshoot / undershoot increases in the charging voltage of the liquid crystal cell, and thus the luminance recognized by the naked eye is recognized. May appear as a change. Due to this problem, the conventional overdrive technique overdrives the data below the overdrive ratio where no noise is observed, and as a result, the response characteristics of the liquid crystal cannot be improved beyond a certain limit.

Accordingly, an object of the present invention is to provide a liquid crystal display device and a method of driving the same, which realize the fast response characteristics of liquid crystal without noise that can be observed with the naked eye.

In order to achieve the above object, the liquid crystal display of the present invention comprises a memory for storing previous frame data; An overdrive modulator for comparing the previous frame data with the current frame data and modulating the current frame data according to a result of the comparison; A calculation unit generating first correction data larger than an output of the overdrive modulation unit and second correction data below an output of the overdrive modulation unit; And selecting the first correction data and the second correction data as data to be sequentially supplied to the first liquid crystal cell, and selecting the second correction data and the first correction data as data to be sequentially supplied to the second liquid crystal cell. It has a selection part.

A method of driving a liquid crystal display according to the present invention includes the steps of storing previous frame data in a memory; Comparing the previous frame data with the current frame data and modulating the current frame data according to the comparison result; A calculator configured to generate first correction data larger than a modulation value of the current frame data and second correction data equal to or less than a modulation value of the current frame data; And selecting the first correction data and the second correction data as data to be sequentially supplied to the first liquid crystal cell, and selecting the second correction data and the first correction data as data to be sequentially supplied to the second liquid crystal cell. Steps.

The liquid crystal display device and the driving method thereof of the present invention can improve the response characteristics of the liquid crystal without noise by increasing the overdrive ratio, dispersing the overdrive amount to neighboring liquid crystal cells, and temporally dispersing the overdrive amount.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 4 to 6H.

Referring to FIG. 8, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 10, a data driving circuit 12, a gate driving circuit 13, a timing controller 11, and an overdrive control circuit ( 14).

In the liquid crystal display panel 10, a liquid crystal layer is formed between two glass substrates. The liquid crystal cells of the liquid crystal display panel 10 are arranged in a matrix by a cross structure of the data lines 14 and the gate lines 16.

The lower glass substrate of the liquid crystal display panel 10 is connected to the data lines 14, the gate lines 16, the TFTs, and the TFTs, and is driven by an electric field between the pixel electrodes 1 and the common electrode 2. The liquid crystal cells Clc, the storage capacitor Cst, and the like are formed.

The black matrix, the color filter, and the common electrode 2 are formed on the upper glass substrate of the liquid crystal display panel 10.

The common electrode 2 is formed on the upper glass substrate in a vertical electric field driving method such as twisted nematic (TN) mode and vertical alignment (VA) mode, and has an in plane switching (IPS) mode and a fringe field switching (FFS) mode. In the same horizontal electric field driving method, the pixel electrode 1 is formed on the lower glass substrate. On the upper glass substrate and the lower glass substrate of the liquid crystal display panel 10, a polarizing plate having an optical axis orthogonal to each other is attached, and an alignment layer for setting a pre-tilt angle of the liquid crystal is formed at an interface in contact with the liquid crystal.

The liquid crystal mode of the liquid crystal display panel applicable to the present invention may be implemented in any liquid crystal mode as well as the above-described TN mode, VA mode, IPS mode, FFS mode. In addition, the liquid crystal display of the present invention may be implemented in any form, such as a transmissive liquid crystal display, a transflective liquid crystal display, a reflective liquid crystal display. In the transmissive liquid crystal display device and the transflective liquid crystal display device, a backlight unit omitted in the drawings is required.

The data driving circuit 12 receives the digital video data RGB (ODC) transmitted from the timing controller 11 in a mini LVDS scheme and analogizes the data RGB (ODC) under the control of the timing controller 11. The data voltage is converted into data voltages and supplied to the data lines 14 of the liquid crystal display panel 10.

The gate driving circuit 13 generates a gate pulse (or scan pulse) in response to the gate timing control signal from the control board CTRB, and sequentially supplies the gate pulse to the gate lines 16.

The timing controller 11 supplies the input digital video data RGB to the overdrive control circuit 13 and outputs the data RGB (ODC) modulated by the overdrive control circuit 16 to the data driving circuit 12. To feed.

The timing controller 11 generates timing control signals for controlling the operation timing of each of the data driving circuit 12 and the gate driving circuit 13 using timing signals DE and CLK input from the outside. The gate timing control signal includes a gate start pulse (GSP), a gate shift clock (GSC), a gate output enable signal (Gate Output Enable, GOE), and the like. The gate start pulse GSP is applied to the first integrated circuit IC of the gate driving circuit 13 to indicate a scan start time at which the first gate pulse is generated. The gate shift clock GSC is a clock signal for shifting the gate start pulse GSP. The gate output enable signal GOE controls the output of the gate driving circuit 13. The data timing control signal includes a source sampling clock (SSC), a polarity control signal (POL), a source output enable signal (Source Output Enable, SOE), and the like. The source sampling clock SSC instructs the sampling and latching operation of the data of the data driving circuit 12 based on the rising or falling edge. The polarity control signal POL controls the polarity of the analog video data voltage output from the data driving circuit 12. The source output enable signal SOE controls the output of the data driver circuit 62. In addition, the timing controller 11 generates the frame inversion signal FRC of FIG. 5 for controlling the overdrive control circuit 13. The logic of the frame inversion signal FRC is inverted at a predetermined time period. In the following embodiment, the inversion period of the frame inversion signal FRC is one frame period.

The overdrive control circuit 16 increases the overdrive ratio in order to speed up the response characteristics of the liquid crystal, and distributes the modulation amount of data in time so that noise luminance is not observed due to the increased overdrive ratio, and between adjacent liquid crystal cells. Disperse. For example, when the gray level of data supplied to neighboring liquid crystal cells is changed to "G20-> G20-> G180-> G180-> G180" for 5 frame periods, the existing overdrive technology is a bright light recognized as noise. The grayscale of the data was modulated to "G20-> G20-> G230-> G180-> G180" by limiting the overdrive ratio so that luminance did not appear. In contrast, the overdrive control circuit 16 modulates the data to " G20-> G20-> G255-> G180-> G180 " by increasing the overdrive ratio, so as not to observe the noise of bright brightness. It modulates G20-> G20-> G255-> G160-> G180 "or modulates" G20-> G20-> G160-> G255-> G180 "to distribute the luminance variation in time. In addition, the overdrive control circuit 16 modulates the data supplied to the neighboring liquid crystal cells by increasing the overdrive ratio to " G20-> G20-> G255-> G180-> G180 " In order not to modulate the gradation value of data charged in A liquid crystal cell to "G20-> G20-> G255-> G180-> G180", the gradation value of data to be charged in A liquid crystal cell and neighboring B liquid crystal cell "G20-> G20-> G160-> G180-> G180" modulates the luminance variation spatially.

The liquid crystal display device of the present invention can be implemented in any liquid crystal mode as well as the above-described TN mode, VA mode, IPS mode, FFS mode. In addition, the liquid crystal display of the present invention may be implemented in any form, such as a transmissive liquid crystal display, a transflective liquid crystal display, a reflective liquid crystal display.

5 is a circuit diagram showing the overdrive control circuit 16 in detail.

Referring to FIG. 5, the overdrive control circuit 16 includes an overdrive modulator 51, a memory 52, a comparator 53, a calculator 54, and first to fourth selectors 55 to 58. And the like.

The overdrive modulator 51 compares the currently input digital video data (or current frame data) with data of a previous frame stored in the memory 52 and modulates data of the current frame as shown in Equations 3 to 5 below. .

Fn (RGB) <Fn-1 (RGB) ---> Fn (MRGB) <Fn (RGB)

Fn (RGB) = Fn-1 (RGB) ---> Fn (MRGB) = Fn (RGB)

Fn (RGB)> Fn-1 (RGB) ---> Fn (MRGB)> Fn (RGB)

In Equations 3 to 5, Fn (RGB) is digital video data input in the current frame period Fn, and Fn-1 (RGB) is input to the previous frame Fn-1 and stored in the memory 52. Digital video data of a frame. Fn (MRGB) is digital video data modulated by the overdrive modulation section 51. The overdrive modulator 51 may modulate the digital video data input to the current frame using a lookup table as shown in Table 1 and a circuit as shown in FIG. 3. The over-drive modulation unit 51 is Korean Patent Application No. 10-2001-0032364, Korean Patent Application No. 10-2001-0057119, Korean Patent Application No. 10-2001-0054123, Republic of Korea Patent Application No. 10-2001-0054124, Republic of Korea Patent Application No. 10-2001-0054125, Republic of Korea Patent Application No. 10-2001-0054127, Republic of Korea Patent Application No. 10-2001-0054128, Republic of Korea Patent Application No. 10-2001 -0054327, Republic of Korea Patent Application No. 10-2001-0054889, Republic of Korea Patent Application No. 10-2001-0056235, Republic of Korea Patent Application No. 10-2001-0078449, Republic of Korea Patent Application No. 10-2002-0046858, Republic of Korea Patent Patent Application No. 10-2002-0074366, Republic of Korea Patent Application No. 2003-0098100, Republic of Korea Patent Application No. 2004-0015499, Republic of Korea Patent Application No. 2004-0049541, Republic of Korea Patent Application No. 2004-0115730, Republic of Korea Patent Application No. 2004- 0116342, Republic of Korea Patent Application No. 2004-0116347, Republic of Korea The overdrive modulation technique disclosed in Patent Application No. 2006-0116974 or the like can also be applied.

The memory 52 stores the digital video data input in the previous frame period and supplies the data to the overdrive modulator 51, the comparator 53, and the calculator 53.

The comparator 53 compares the most significant 5 bits (MSB) of the data MRGB input from the overdrive modulation unit 51 with the most significant 5 bits of the previous frame data input from the memory 52. And outputs a control signal for controlling the second and fourth selectors 56 and 58 according to the comparison result. In this case, the comparator 53 does not compare the lower 3 bits of the data. The second and fourth selectors 56 and 58 are corrected by the calculation unit 54 when the system of the previous frame data and the current frame data is greater than or equal to a predetermined threshold in response to a control signal input from the comparator 53. On the other hand, if the gray level difference of the data is less than the threshold value, the data MRGB from the overdrive modulation unit 51 is output. The threshold value is a value determined by the result of the overdrive quality test, and may be set to '10'. When the difference between the previous frame data and the current frame data is less than 10 gray scales, the inventors of the present invention modulate the voltage to be charged in the liquid crystal cells A and B using the output of the calculation unit 54. The result was not confirmed. On the other hand, the comparator 53 compares the input data of the current frame before being input to the overdrive modulator 51 with the previous frame data from the memory 52 and compares the second and fourth multiplexers in the manner described above. You can also control it.

The calculation unit 54 is a first larger than the modulation data MRGB of the current frame based on a difference between the data of the current frame modulated by the overdrive modulation unit 51 and the previous frame data from the memory 52. The correction data ODC1 is calculated, and the second correction data ODC2 equal to or less than the modulation data MRGB of the current frame is calculated. The first and second correction data ODC1 and ODC2 are determined as gray values satisfying Equation 6 below.

ΔY _A '+ ΔY _B ' = ΔY _A + ΔY _B

Here, ΔY _A is the luminance change of the A liquid crystal cell according to the change of the voltage when the data of the previous frame is changed to the modulation data (MRGB), and ΔY _B is the voltage when the data is changed from the data of the previous frame to the modulation data (MRGB) The change in luminance of the B liquid crystal cell according to the change of. ΔY _A ′ is the luminance change of the A liquid crystal cell according to the change of the voltage when the first correction data ODC1 is changed from the data of the previous frame, and ΔY _B ′ is the second correction data ODC2 from the data of the previous frame. The change in the luminance of the B liquid crystal cell according to the change of the voltage. The operation of the calculation unit 54 will be described in more detail with reference to the examples of FIGS. 6A to 6H.

The first to fourth selectors 55 to 58 include a multiplexer.

The first correction data ODC1 is input to the first input terminal of the first selector 55, and the second correction data ODC2 is input to the second input terminal of the first selector 55. The first selector 55 supplies the first correction data ODC1 to the second selector 56 in the odd frame period under the control of the frame inversion signal FRC, while the second correction data ( ODC2) is supplied to the second selector 56. Therefore, the first selector 55 switches the correction data ODC1 and ODC2 to be input to the second selector 56 every frame.

Correction data ODC1 and ODC2 from the first selector 55 are input to the first input terminal of the second selector 56, and the overdrive modulation unit is input to the second input terminal of the second selector 56. The modulation data MRGB from 51 is input. In response to the control signal from the comparator 53, the second selector 56 outputs the output of the overdrive modulator 51 when the gray level difference between the previous frame data and the modulation data of the current frame is less than a threshold value. Output as digital video data to be charged to a cell. On the other hand, the second selector 56 outputs the first selector 55 when the gray level difference between the previous frame data and the modulation data of the current frame is greater than or equal to the threshold in response to the control signal from the comparator 53. Is output as digital video data to be charged in the A liquid crystal cell. Accordingly, the second selector 55 compares the previous frame data to be charged in the A liquid crystal cell and the current frame data, and modulates the data of the current frame to be charged in the A liquid crystal cell according to the gray level difference. Select one of (ODC1, ODC2).

The second correction data ODC2 is input to the first input terminal of the third selector 57, and the first correction data ODC1 is input to the second input terminal of the third selector 57. The third selector 57 supplies the second correction data ODC2 to the fourth selector 58 in the odd frame period under the control of the frame inversion signal FRC, while the first correction data ( The ODC1) is supplied to the fourth selector 56. Therefore, the third selector 55 switches the correction data ODC1 and ODC2 to be input to the fourth selector 58 every frame.

Correction data (ODC1, ODC2) from the third selector 57 is input to the first input terminal of the fourth selector 58, and the overdrive modulation unit is input to the second input terminal of the fourth selector 58. The modulation data MRGB from 51 is input. In response to the control signal from the comparator 53, the fourth selector 58 outputs the B-drive output of the overdrive modulator 51 when the gray level difference between the previous frame data and the modulation data of the current frame is less than the threshold value. Output as digital video data to be charged to a cell. On the other hand, the second selector 56 outputs the first selector 55 when the gray level difference between the previous frame data and the modulation data of the current frame is greater than or equal to the threshold in response to the control signal from the comparator 53. Is output as digital video data to be charged in the B liquid crystal cell. Accordingly, the second selector 55 compares the previous frame data to be charged in the B liquid crystal cell and the current frame data, and modulates the data of the current frame to be charged in the B liquid crystal cell according to the gray level difference. Select one of (ODC1, ODC2).

6A to 6H measure changes in luminance of neighboring liquid crystal cells A and B when driving the liquid crystal cells A and B using only the output of the overdrive modulator 51. FIG. Experimental results obtained by comparing the liquid crystal response characteristics of the two liquid crystal cells by measuring the luminance change when driving the liquid crystal cells A and B with the space-time division correction data ODC1 and ODC2 of the control circuit 16 are compared.

Referring to FIG. 6A, when the gray level of the data voltages to be charged in the adjacent liquid crystal cells A and B by the overdrive modulation unit 51 is changed from G63 to G191, the calculation unit 54 may not change the gray level. Accordingly, G255 is calculated by adding the first weight to G191, and G95 is generated by subtracting the second weight from G191. The first and second selectors 55 and 56 output G255 as a digital value of the data voltage to be charged in the A liquid crystal cell during the odd frame period in response to the frame inversion signal. 58) outputs G95 as a digital value of the data voltage to be charged in the B liquid crystal cell. The first and second selectors 56 output G95 as a digital value of the data voltage to be charged in the A liquid crystal cell during the even frame period, and the third and fourth selectors 57 and 58 output the B liquid crystal cell. G255 is output as the digital value of the data voltage to be charged. As a result, the response characteristic of the liquid crystal was not significantly improved than the output of the overdrive modulator 51, that is, the existing overdrive technology, but the overshoot width was reduced to reduce the change in luminance seen as noise.

Referring to FIG. 6B, when the gray level of the data voltages to be charged in the adjacent liquid crystal cells A and B by the overdrive modulation unit 51 is changed from G63 to G159, the calculation unit 54 may not change the gray level. Accordingly, G255 is calculated by adding the first weight value to G159, and G64 is generated by subtracting the second weight value from G191. The first and second selectors 55 and 56 output G255 as a digital value of the data voltage to be charged in the A liquid crystal cell during the odd frame period in response to the frame inversion signal. 58) outputs G63 as a digital value of the data voltage to be charged in the B liquid crystal cell. The first and second selectors 55 and 56 output G63 as a digital value of the data voltage to be charged in the A liquid crystal cell during the even frame period, and the third and fourth selectors 57 and 58 output the B liquid crystal. G255 is output as the digital value of the data voltage to be charged in the cell. As a result, the response characteristics of the liquid crystals were not significantly improved than the existing overdrive technology, but the overshoot width was reduced to reduce the change in luminance seen as noise.

Referring to FIG. 6C, when the gray level of the data voltages to be charged in the adjacent liquid crystal cells A and B by the overdrive modulation unit 51 is changed from G223 to G159, the calculating unit 54 may not change the gray level. Accordingly, G223 is calculated by adding the first weight value to G159, and G31 is generated by subtracting the second weight value from G159. The first and second selectors 55 and 56 output G223 as a digital value of the data voltage to be charged in the A liquid crystal cell during the odd frame period in response to the frame inversion signal, and the third and fourth selectors 57, 56 and 56 respectively. 58) outputs G31 as a digital value of the data voltage to be charged in the B liquid crystal cell. The first and second selectors 55 and 56 output G31 as a digital value of the data voltage to be charged in the A liquid crystal cell during the even frame period, and the third and fourth selectors 57 and 58 respectively output the B liquid crystal. G223 is output as the digital value of the data voltage to be charged in the cell. As a result, the response characteristics of the liquid crystal were not significantly improved than the existing overdrive technology, but the undershoot width was reduced to reduce the change in luminance seen as noise.

Referring to FIG. 6D, if the grayscales of the data voltages to be charged in the adjacent liquid crystal cells A and B by the overdrive modulation unit 51 are changed from G159 to G63, the calculating unit 54 may change the gray level. Accordingly, G95 is calculated by adding the first weight to G63, and G0 is generated by subtracting the second weight from G63. The first and second selectors 55 and 56 output G95 as a digital value of the data voltage to be charged in the A liquid crystal cell during the odd frame period in response to the frame inversion signal, and the third and fourth selectors 57, 56 and 56 respectively. 58) outputs G0 as a digital value of the data voltage to be charged in the B liquid crystal cell. The first and second selectors 55 and 56 output G0 as a digital value of the data voltage to be charged in the A liquid crystal cell during the even frame period, and the third and fourth selectors 57 and 58 output the B liquid crystal. G95 is output as a digital value of the data voltage to be charged in the cell. As a result, the response characteristics of the liquid crystal were not significantly improved than the existing overdrive technology, but the undershoot width was reduced to reduce the change in luminance seen as noise.

Referring to FIG. 6E, when the gray level of the data voltages to be charged in the adjacent liquid crystal cells A and B by the overdrive modulation unit 51 is changed from G95 to G191, the calculating unit 54 may be different from the gray level difference. Accordingly, G255 is calculated by adding the first weight to G191, and G63 is generated by subtracting the second weight from G191. The first and second selectors 55 and 56 output G255 as a digital value of the data voltage to be charged in the A liquid crystal cell during the odd frame period in response to the frame inversion signal. 58) outputs G63 as a digital value of the data voltage to be charged in the B liquid crystal cell. The first and second selectors 55 and 56 output G63 as a digital value of the data voltage to be charged in the A liquid crystal cell during the even frame period, and the third and fourth selectors 57 and 58 output the B liquid crystal. G255 is output as the digital value of the data voltage to be charged in the cell. As a result, the response characteristics of the liquid crystal were not significantly improved than the existing overdrive technology, but the undershoot width was reduced to reduce the change in luminance seen as noise.

Referring to FIG. 6F, if the gradation of the data voltages to be charged in the adjacent liquid crystal cells A and B by the overdrive modulator 51 is changed from G31 to G159, the calculation unit 54 may be different from the gradation difference. Accordingly, G223 is calculated by adding the first weight to G159, and G0 is generated by subtracting the second weight from G159. The first and second selectors 55 and 56 output the G223 as a digital value of the data voltage to be charged in the A liquid crystal cell during the odd frame period in response to the frame inversion signal, and the third and fourth selectors 57, 58) outputs G0 as a digital value of the data voltage to be charged in the B liquid crystal cell. The first and second selectors 55 and 56 output G0 as a digital value of the data voltage to be charged in the A liquid crystal cell during the even frame period, and the third and fourth selectors 57 and 58 output the B liquid crystal. G223 is output as the digital value of the data voltage to be charged in the cell. Experimental results show that the overshoot width is larger than that of the existing overdrive technique, but the response characteristics of the liquid crystal are improved.

Referring to FIG. 6G, when the gray level of the data voltages to be charged in the adjacent liquid crystal cells A and B by the overdrive modulation unit 51 is changed from G191 to G95, the calculating unit 54 may not change the gray level. Accordingly, G127 is calculated by adding the first weight to G95, and G0 is generated by subtracting the second weight from G95. The first and second selectors 55 and 56 output G127 as a digital value of the data voltage to be charged in the A liquid crystal cell during the odd frame period in response to the frame inversion signal, and the third and fourth selectors 57, 56 and 56 respectively. 58) outputs G0 as a digital value of the data voltage to be charged in the B liquid crystal cell. The first and second selectors 55 and 56 output G0 as a digital value of the data voltage to be charged in the A liquid crystal cell during the even frame period, and the third and fourth selectors 57 and 58 output the B liquid crystal. G127 is output as the digital value of the data voltage to be charged in the cell. The experimental results showed that the response characteristics of the liquid crystals were similar to those of the conventional overdrive technique, and the overshoot and undershoot widths were similar to those of the conventional overdrive technique.

Referring to FIG. 6H, when the gray level of the data voltages to be charged in the adjacent liquid crystal cells A and B by the overdrive modulation unit 51 is changed from G159 to G127, the calculating unit 54 may not change the gray level. Accordingly, G191 is calculated by adding the first weight to G127, and G0 is generated by subtracting the second weight from G127. The first and second selectors 55 and 56 output G191 as a digital value of the data voltage to be charged in the A liquid crystal cell during the odd frame period in response to the frame inversion signal, and the third and fourth selectors 57, 56 and 56 respectively. 58) outputs G0 as a digital value of the data voltage to be charged in the B liquid crystal cell. The first and second selectors 55 and 56 output G0 as a digital value of the data voltage to be charged in the A liquid crystal cell during the even frame period, and the third and fourth selectors 57 and 58 output the B liquid crystal. G191 is output as the digital value of the data voltage to be charged in the cell. As a result, the response characteristics of the liquid crystal are significantly improved than the conventional overdrive technique, and the undershoot width is larger than that of the conventional overdrive technique.

As can be clearly seen from the above experimental results, the liquid crystal display device and the driving method thereof according to an embodiment of the present invention improve the response characteristics of the liquid crystal by increasing the overdrive ratio and increase the overdrive ratio, even though the overdrive amount is adjacent to the liquid crystal cell. By distributing the power over the wire and also over time, the overshoot and undershoot width can be reduced in most cases to reduce noise fluctuations seen as noise.

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.

1 is a waveform diagram showing a change in luminance according to data in a conventional liquid crystal display.

2 is a waveform diagram showing an example of a luminance change caused by data modulation in the overdrive method.

3 is a circuit diagram showing an overdrive circuit.

4 is a block diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 5 is a circuit diagram illustrating in detail the overdrive control circuit shown in FIG. 4.

6A to 6H are graphs illustrating a response characteristic test result of a liquid crystal display according to an exemplary embodiment of the present invention.

Description of the Related Art

11: Timing Controller 16: Overdrive Control Circuit

51: overdrive modulator 52: memory

53: comparison unit 54: calculation unit

55 ~ 58: Selection part

Claims (10)

A memory for storing previous frame data; An overdrive modulator for comparing the previous frame data with the current frame data and modulating the current frame data according to a result of the comparison; A calculation unit generating first correction data larger than an output of the overdrive modulation unit and second correction data below an output of the overdrive modulation unit; And Selecting the first correction data and the second correction data as data to be sequentially supplied to the first liquid crystal cell, and selecting the second correction data and the first correction data as data to be sequentially supplied to the second liquid crystal cell A liquid crystal display device comprising a portion. The method of claim 1, And a comparison unit configured to generate a first control signal for controlling the selection unit by comparing a difference between the modulation value of the current frame data and the previous frame data with a predetermined threshold value. The method of claim 2, And a timing controller for generating a second control signal in which logic is inverted by a predetermined time unit. The method of claim 3, wherein The selection unit, A first selector configured to output the second correction data after outputting the first correction data in response to the second control signal; A second selector which selects an output of the first selector as data to be supplied to the first liquid crystal cell when the gray level difference between the previous frame data and the current frame data is greater than or equal to the threshold value in response to the first control signal; A third selector configured to output the first correction data after outputting the second correction data in response to the second control signal; And A fourth selector configured to select an output of the third selector as data to be supplied to the second liquid crystal cell when the gray level difference between the previous frame data and the current frame data is greater than or equal to the threshold value in response to the first control signal; Liquid crystal display device characterized in that. The method of claim 4, wherein And the logic of the second control signal is inverted in units of one frame period. Storing previous frame data in a memory; Comparing the previous frame data with the current frame data and modulating the current frame data according to the comparison result; A calculator configured to generate first correction data larger than a modulation value of the current frame data and second correction data equal to or less than a modulation value of the current frame data; And Selecting the first correction data and the second correction data as data to be sequentially supplied to the first liquid crystal cell, and selecting the second correction data and the first correction data as data to be sequentially supplied to the second liquid crystal cell Method of driving a liquid crystal display device comprising a. The method of claim 6, And generating a first control signal for controlling the selection unit by comparing a difference between the modulation value of the current frame data and the previous frame data with a predetermined threshold value. . The method of claim 7, wherein And generating a second control signal in which logic is inverted in a predetermined time unit. The method of claim 8, Selecting the first correction data and the second correction data as data to be sequentially supplied to the first liquid crystal cell, and selecting the second correction data and the first correction data as data to be sequentially supplied to the second liquid crystal cell Is, Outputting the second correction data after outputting the first correction data in response to the second control signal; Selecting an output of the first selector as data to be supplied to the first liquid crystal cell when the gray level difference between the previous frame data and the current frame data is greater than or equal to the threshold value in response to the first control signal; Outputting the first correction data after outputting the second correction data in response to the second control signal; And And selecting an output of the third selector as data to be supplied to the second liquid crystal cell when the gray level difference between the previous frame data and the current frame data is greater than or equal to the threshold value in response to the first control signal. A method of driving a liquid crystal display device. The method of claim 9, And the logic of the second control signal is inverted in units of one frame period.

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