TWI364735B - - Google Patents

Description

1364735 IX, invention description: 'Technical field of invention> A driving technology of passive matrix liquid crystal display, especially for a twisted line type (TN) and super twisted line type (STN) passive matrix type liquid crystal display device 彳 1^ 13), it can effectively shorten the liquid crystal reaction time and improve the phenomenon of dynamic bucking. [Prior Art] Due to the thin and light characteristics of liquid crystal displays and lower power consumption than conventional CRT displays, liquid crystal displays have gradually replaced CRT displays in recent years. Liquid crystal flat panel display can be divided into passive matrix according to the driving display method

Type (PM-LCD) and active matrix type (AM-LCD). The driving method of the PM-LCD is to set the column (X) direction transparent ITO (Indium Tin Oxide) electrode on one of the upper and lower glass panels, and the row (Y) direction transparent ITO electrode on the other panel. After the two panels are bonded (intermediately filled with liquid crystal), the upper and lower panels form a grid-like intersection of the electrodes, which is the element of the display panel. The potential difference of the halogen is to provide the driving voltage from the outside to control the electrodes in the X and Y directions. , to achieve the rotation of the liquid crystal in the driving element. The driving method of the AM-LCD is to set a switching element (ie, a thin film transistor (TFT)) and a secondary auxiliary capacitor (Cst) for storing signals on each of the tops of the panel. The pixel driving is performed by each pixel. The components on the halogen are independently controlled because the AM-LCD is a thin film transistor (TFT) placed on a panel, also known as a TFT-LCD. 5 1364735 Please refer to the schematic diagram of the passive correction ship crystal display plus xn) in Figure 1. Common twisted nematic (TN) and material steering type (STN) are PM_LCD products, and there are no nonlinear components (similar to a switch element) to control the operation of liquid crystal pixels, so the formation of each element v is the overlapping area of the horizontal common (C〇mmon) electrode 2 trace and the vertical data (Segment) electrode 3 trace. 1> centistoke: > The basic principle of operation is to use the electro-optic effect of the liquid crystal material on the root mean square value (R〇〇t Mean Square Value; RMS) of the applied voltage, and the reaction time of the liquid crystal material must be It is much larger than the scanning period of the driving pulse wave. If the frame rate is 60 Hz, the horizontal scanning line (ie, the common electrode 2) is selected at a time interval of 16.67 ms. Typically 200ms, this is a necessary condition for liquid crystal to root mean square (RMS) response. However, 'traditional amplitude selection drive (Alt & Pleshko Theory; APT) mode, to display dynamic surface, due to liquid crystal material If the reaction time is too slow, it will cause smear of the moving picture. If the liquid crystal material of the fast reaction I is used, the flicker will be severely flickered and the contrast will be greatly reduced. Please refer to "Figure 2", which is a block diagram of the general operation of the Over-Driving circuit. In view of the foregoing problems, a general solution is to give different values of the overdrive voltage V' for different pictures. The method is to use a picture judging circuit 1 to add a new current current frame data to a frame data (Previ〇us Field) previously stored in a storage device 11 disposed inside (or outside) the driving device. ) After a comparison of 6 1364735

If the different representations are dynamic, the data of the dynamic picture is generally sent through a look-up table operation (LUT) circuit 13 to look up the table and then send out the corresponding overdrive output. The voltage value, which is the operating principle of the Over-Driving circuit. The look-up table operation (LUT) uses an array of indices as a new overdrive voltage V'value table' to integrate some non-linear and complex calculus into constants, which omits complicated calculations throughout the operation. increased

Substantial image processing efficiency. The output voltage value sent out can correspond to the correct output overdrive voltage ν' of the data electrode 3, which can effectively shorten the driving method used by the conventional passive matrix liquid crystal display (TN type and STN type) as the amplitude selective driving (APT). The reaction time reduces the phenomenon of smear in the dynamic display. Because the passive matrix type liquid crystal display (TN type and STN type) is a type 2 structure, there is no switching element in each element, and the liquid storage, closing, and electric charge cannot be locked, so when the data electrode output voltage After that, the liquid charge will leak through the stray capacitance (Cgd) or its charging path, and the liquid b can not maintain a fixed level, so the data electrode is in a frame and then in the liquid phase. The true effective potential of the halogen capacitor is higher than that of the data electrode 1 , which results in the display of dynamic edge blurring (Blurring). [2] In order to solve the above-mentioned deficiency, avoiding the existence of the defect, the present invention Type-steering type (TN) and super-torsional nematic (stn) passive matrix 振幅 之 amplitude selection drive (Αρτ), using overdrive (〇να 7 1364735 driving) compensation method and frequency update rate The concept is applied to passive matrix liquid crystal displays such as twisted linear (tn) and super-twisted linear (STN), which can effectively shorten the reaction time and improve the dynamic bucking. In order to achieve the above purpose, the present invention utilizes the operating principle of overdrive, and passes the judgment mechanism of the dynamic surface after inputting the red, green and blue (RGB) three primary color data bus, as long as the current data and the previous data are used. Differently, an overdrive (〇ver_Driving) compensation potential that is higher or lower than the original output potential is given N times in an update time of each data bus through an output frequency multiplier circuit, and N is a positive integer (2SNS8) of 2 or more and less than or equal to 8. Under normal circumstances, only the data voltage outputted once in two frame times will charge the liquid crystal capacitor, because the passive matrix liquid crystal display (TN type and STN type) has no switching elements in each of the books, the liquid crystal capacitor The internal charge will pass through stray capacitance (such as its charging path leakage, so after a frame time, the voltage on the liquid crystal capacitor is not enough to reach the expected voltage level of the input data bus. We change it to a graph Repeat the output N times in the frame time (that is, charge the halogen capacitor N times in the frame = time), and give the higher or lower = drive compensation voltage, so it can be used in a shorter time. The liquid crystal is rotated up to the desired target brightness, and the problem of the reaction time of the passive matrix type liquid crystal display such as the twisted nematic (TN) and the super twisted type (STN) is greatly improved. The compensation potential V' is the value corresponding to the original output potential v after the look-up table (LUT), and the corresponding overdrive output voltage value is different 1364735. The voltage range is the highest voltage of the OgV'S liquid crystal drive. We can convert the three primary color RGB data of the image data into YCbCr data, compress and sample and combine according to the video compression standard. The compressed sampling is selected from Y: Cb : Cr=4 : 2 : 〇 and Y : Cb : Cr = k One of the sampling calculation rules of 4:1:1, whereby the amount of stored data can be effectively reduced by half. [Embodiment] g The details and technical description of the present invention are further described by way of examples. It should be understood that the embodiments are for illustrative purposes only and are not to be construed as limiting of the embodiments of the invention. Twisted nematic (TN) and super twisted nematic (STN) passive matrix types The driving method used in the liquid crystal display, the data of the driving device converts different output gray scale voltages according to the digital red, green and blue (RGB) three primary color data input by each frame (optically correspondingly The brightness of a gray scale.) Because the twisted nematic (TN) and super twisted nematic (STN) • /, there are two states, and the gray scale is generated at the time of one scan line (1 line). Pulse width modulation inside (Pulse W Idth Modulation; PWM) way to distinguish. Please refer to "Figure 3", which is a schematic diagram of the output waveform of the data electrode signal SEG j in a scan frame. It is assumed that there are time in the alpha frame. m scanning lines (mxn matrix type liquid crystal display =) One read/write (WR) period indicates the time of one scanning line (1 Hne me)_' It can be seen from "Fig. 3" that the data electrode signal SEG is different according to the data. Output gray scale voltage, and rotate different pulse width modulation waveforms. As shown in Figure 4, assume that the time for charging a scan line is divided into 16 equal parts by 9 1364735, and the data electrode signal SEG0 is in a certain section. The black aliquot of the line time is 6/16, the next line is 12/16, and the data electrode signal SEG1 is all black in the time of this line is 13 VIII, one line It is 10/16.

However, because passive matrix liquid crystal displays (TN type and STN type) are a passive architecture, there is no switching element in each pixel, so when the number of electrodes is output voltage, the charge in the liquid crystal capacitor will pass through the stray capacitance (1). Buckle) or its charging path leakage 'so liquid crystal capacitor can not maintain a fixed level, so the data electrode is charged in a frame time, the real effective potential of the liquid crystal pixel capacitor will be more than the data electrode output. Please refer to the figure in Figure 5 for the position of the liquid crystal from the initial brightness to the target brightness. The data electrode needs to go through multiple graphs =

After the time is charged, the liquid crystal in the halogen has a six-fold voltage Veff from the initial position to the target position, so the reaction of the twisted nematic (TN) and the super-twisted nematic (STN) passive matrix liquid crystal display Time JI is so slow. "Figure 5" shows that when the first frame time 'the charging voltage in the liquid crystal capacitor is VI, but because the stray capacitance St is the leakage current dl ', the last frame time data Electrode Y, charging circuit ........... one - $ crystal capacitor 'frame dl

The effective voltage of Veff2 is Vl_dl = Veffl, and so on, the effective voltage of the first data electrode to the liquid crystal capacitor is also Vi. The target brightness after the same electric wish is sent out 12 times by the data electrode', so the reaction time of the liquid crystal display is By our time 16.67msxl2, close to 200ms. <Fig. 6 of the solid frame, which is a schematic diagram of the block 1364735 of the present invention. As with the general over-driving (Over-Driving), the current incoming frame data (Current Field) is previously stored with a facet judgment circuit 20 for different values of different overdrive voltages V' given for different pictures. Before the storage device 21 disposed inside the drive device (outside), a frame field (Previous Field) is compared with each other by the comparison device 22, and if the display is a dynamic picture, the data of the dynamic picture is generally transmitted through a The look-up table operation (LUT) circuit 23 uses the look-up table to look up the table and sends the value of the corresponding overdrive voltage V'. The present invention utilizes the principle of overdrive operation to input red, green and blue (RGB) three primary colors. The comparing means 22 for judging the dynamic picture behind the bus bar, as long as the current data is found to be different from the previous one, is elastically transmitted through an output frequency multiplying circuit 24 located after the look-up operation (LUT) circuit 23. An overdrive compensation potential V' higher or lower than the original output potential V is given N times in the refresh time of the data bus, and the N is greater than or equal to 2, less than A positive integer equal to 8 (2SNS 8), and the compensation potential V is a value corresponding to the original output potential V through a table lookup operation (LUT), and the corresponding overdrive output voltage value is sent, and the voltage range is 〇SV. , the highest voltage of the LCD driver. Therefore, the data electrode of the driving component is written to the display panel at a frequency N times the input frequency of the red, green and blue (RGB) three primary color data bus. Please refer to the figure shown in Figure 7 for describing the data electrode of the drive component. The frequency of the write panel will be a comparison of the N times (6 times) of the input data bus update frequency with the original update frequency. The right side shows the voltage level of the liquid crystal from the initial zero level to the target brightness (Target Voltage), number 1364735

According to the time required for the electrode to pass, I can send the same round-out voltage νι and listen to _) the time of the second standard brightness. So the reaction time is π between 16.6msx6, close to 1〇〇ms, and the complex leakage path is pulled down. Voltage level. In the "Fig. 7 = pixel, my job electrode, the original turn-out potential V1 is in the material" = 'one frame time), when the output frequency multiplier circuit is updated, V1 is repeatedly output six times, so it can be - The voltage in the frame time reaches the target brightness we expect, so the reaction time can be = the time of the frame, .6ms.町] month 匕 纽 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到 到Shorter (reaction time can be less than - ί box time) 'Improve the twisted nematic (ΤΝ) and super-twisted nematic passive matrix display reaction time is too slow. In this way, not only does the data electrode output an effective voltage that is larger (or smaller) than the original turn-off potential, but also a plurality of data update times, so that the liquid crystal can be rotated to reach me in a shorter time. The target brightness greatly improves the problem of moving image blurring due to the slow reaction time of the passive matrix type liquid crystal display such as the twisted nematic (ΤΝ) and the super twisted nematic (STN). Please refer to the figure in Figure 9 for the overdrive (〇ver_Driving) compensation data electrode level waveform (the output level of the "Figure 4" output level 12 1364735 waveform is overdriven) 'after the overdrive data electrode SEGO The all black aliquot of the time in a certain line is the entire scan line time (13/16 of 1 line, the next line is 14/16, and the data electrode SE(}1 is within a certain line time). The all black aliquot is i 5/16, and the lower - line is 12/16. The overdrive compensation of the data electrode SEG output N times in each data update time enables the liquid crystal in the pixel to be more The short-time (close to one frame time) reaches or approaches the target brightness of the effective voltage Veff of the liquid crystal from the initial position to the target position in the pixel, so that the phenomenon of moving picture blur can be greatly improved. The basic driving method of column type (TN) and super twisted nematic (STN) is amplitude selective driving (Αρτ), which is operated by using the electro-optic light generated by the liquid crystal material to the root mean square value (RM s ) of the applied voltage. Overdrive voltage compensation method of the present invention After the rms value, there is no serious flicker. In terms of cost saving, the original overdrive (〇ver_Driving) compensation method needs to add an additional drawing memory (GRAM) to store the previous picture. The material is used to compare the data of the three primary colors of the image data into YCbCr data, and the compression and sampling are combined according to the video compression standard. Please refer to the “Figure 1”. A block diagram of another implementation of the overdrive circuit of the present invention, so that the previous frame data first passes through a first conversion unit 25, and the first conversion unit 25 accesses the image data of the three primary colors RGB of the previous frame, and the three primary colors are The RGB data is converted into YCbCr data as shown in the "nth image", wherein the compressed sampling is selected from one of Y: Cb: cr=4: 2: 〇 and Y: Cb: Cr=4:1:1. The calculation rule is to store the YCbCr data in the storage device 21 inside the driving device (or 13 1364735), and a second converting unit 26 converts the YCbCr data into three primary color RGB data, and sends the data to the comparing device 22 .because The meaning represented by Y is the luminance signal, and the meaning of cb and Cr is that the color difference signal 'the Y component that has the greatest influence on the human eye' is compressed by sampling of a sampling ratio and then stored in the memory. The size of the memory required by the driving device. Thereby, the amount of stored data can be effectively reduced by half, so that the data of the previous one and the current picture after being subjected to the drive compensation processing can be directly stored in the original driving device. Internal drawing memory, no additional drawing memory required. However, the above is only the preferred embodiment of the present invention, and the scope of the present invention cannot be limited thereto, that is, the simple equivalent change and the genus of the description according to the scope of the present invention. The scope of the invention is covered. White milk 1364735 [Simple description of the diagram] Figure 1 is a schematic diagram of the structure of a passive matrix liquid crystal display (mxn). The 2 figure is a block diagram of the general operation of the overdrive circuit. Figure 3 is a schematic diagram of the output waveform of the data electrode signal (SEG) in a frame of a scan frame. Fig. 4 is a schematic diagram showing the data electrode signal (SEG) divided into 16 equal-part round-off level waveforms in one line time. Figure f is a schematic diagram showing the position of the liquid crystal in a pixel from the initial brightness to the target brightness. Figure 6 is a block diagram showing the overdrive circuit of the present invention. Figure 7 depicts the frequency of the data electrode write panel of the drive component as a comparison of the N-fold (6 times) frequency of the input data bus update with the original update frequency. Fig. 8 is a view showing a comparison of the data electrode of the driving element with the overdrive voltage writing panel' and the frequency will be N times (6 times) the update frequency of the input data bus and the original voltage update frequency. Figure 9 is a schematic diagram of the overdrive compensation data electrode signal (SEG) divided into 16 equal output level waveforms at one line time. Figure 10 is a block diagram showing another embodiment of the overdrive circuit of the present invention. Figure 11 is a schematic diagram of the conversion of the RGB data of the three primary colors by YCbCr (4: 2: 〇). [Description of main component symbols] 1 : pixel 2 . Common electrode 3 : data electrode 10 , 20 : facet judgment circuit 15 1364735 11 , 21 : storage device 12 , 22 : comparison device 13 , 23 : look-up table operation circuit 24 Output multiplier circuit 25: first conversion unit 26: second conversion unit V': overdrive voltage C0M1~COMm: common pole signal SEG1~SEGn: data signal

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Claims (1)

X. The scope of application for patents: Using the operating principle of overdrive, after the dynamic screen judgement machine is input, the data bus mechanism of the three primary colors of red, green and blue (RGB) is input as long as the current data is different from the previous one, 'transmission-output frequency multiplier circuit Elastically updating, in each data bus, an overdrive compensation potential higher or lower than the original turn-off potential to compensate for leakage of charge in the liquid crystal capacitor of the liquid crystal display; and the n is A positive integer greater than 2 and less than or equal to 8. 2. According to the age-approved patent, the method of driving the rewards, in which the step-by-step driving of the 仏-potential system is through the _ wire operation, the method of driving the circuit paste, sending 1 corresponding to different faces given different The compensation potential is driven, and the overdrive compensation potential range is greater than or equal to 〇, which is less than or equal to the highest voltage of the liquid crystal drive. 3. According to the driving method of the 请 · 围 围 , , , , , , , , , , , , , , , , , , 围 围 围 围 围 围 围 围 围 围 围 围 围 围 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动According to the driving method of the third embodiment of the patent application scope, the compression sampling is selected from the Y-Cb:Cr=4:2:0 and Y:Cb:Cr=4:hl-sampling calculation rules. 17