KR100859468B1 - Method and apparatus for driving liquid crystal display - Google Patents

Abstract

The present invention relates to a method and apparatus for driving a liquid crystal display device to improve image quality in a field sequential driving method.

The method and apparatus for driving a liquid crystal display according to the present invention modulate the source data using preset modulation data, and time-divid the modulated data by red, green, and blue to the display panel. In addition, the method and apparatus for driving a liquid crystal display according to the present invention sequentially irradiate red light, green light, and blue light in synchronization with time-division data.

Description

TECHNICAL AND APPARATUS FOR DRIVING LIQUID CRYSTAL DISPLAY}             

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

2A to 2C are cross-sectional views showing stepwise driving of an OCB mode liquid crystal.

3 is a cross-sectional view showing a conventional liquid crystal display device.

FIG. 4 is a waveform diagram illustrating driving waveforms of the liquid crystal display shown in FIG. 3.

5 is a cross-sectional view of a liquid crystal display device driven by a conventional field sequential driving method.

FIG. 6 is a waveform diagram illustrating driving waveforms of the liquid crystal display shown in FIG. 3.

7 is a waveform diagram illustrating a change in response speed of a liquid crystal due to data modulation in the liquid crystal display according to the exemplary embodiment of the present invention.

8 is a diagram illustrating an example of data modulation.

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

FIG. 10 is a block diagram illustrating a first embodiment of the data modulator shown in FIG. 9.                 

FIG. 11 is a block diagram illustrating a second embodiment of the data modulator shown in FIG. 9.

<Description of Symbols for Main Parts of Drawings>

21,37,57: upper substrate 22,36,56: common electrode

23,32,52: lower substrate 24,33,53: pixel electrode

25, 34, 54: liquid crystal 31: white lamp

51R, 87R: Red lamp 51G, 87G: Green lamp

51B, 87B: Blue lamp 80: Timing controller

81: data modulator 82: data driver

83: gamma voltage supply unit 84: data line

85 gate line 86 liquid crystal panel

88: OCB reset section 89: gate driver

90 lamp driving unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a method and apparatus for driving a liquid crystal display device for improving image quality in a field sequential driving method.

In general, a liquid crystal display (LCD) displays an image by adjusting light transmittance of liquid crystal cells according to a video signal. An active matrix liquid crystal display device in which switching elements are formed for each liquid crystal cell is suitable for displaying moving images. As a switching element used in an active matrix liquid crystal display device, a thin film transistor (hereinafter, referred to as TFT) is mainly used.

As can be seen in Equations 1 and 2, the liquid crystal display has a disadvantage in that the response speed is slow due to the inherent viscosity and elasticity of the liquid crystal.

(gamma)는 액정분자의 회전점도(rotational viscosity)를 각각 의미한다. Where τr is the rising time when voltage is applied to the liquid crystal, Va is the applied voltage, VF is the Freederick Transition Voltage at which the liquid crystal molecules start the tilt motion, and d is the liquid crystal. The cell gap of the cell,

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

Here, τf denotes a falling time during which the liquid crystal is restored to its original position by the elastic restoring force after the voltage applied to the liquid crystal is turned off, and K denotes an elastic modulus inherent to the liquid crystal.                         

The liquid crystal mainly used in the liquid crystal display is a twisted nematic (TN) mode liquid crystal. In the TN mode liquid crystal, the twist angle of the liquid crystal molecules is set to 90 degrees by the initial alignment, and when the electric field is applied, the twisted liquid crystal molecules are spread out to transmit light. This TN mode liquid crystal has a short viewing angle and a long response time. The gray scale response time of the TN mode liquid crystal is 11 to 47 (ms) as shown in Table 1 when the voltage applied to the liquid crystal cell is V0 to V7. In general, the response time between gray levels of the TN mode liquid crystal is known to be 10 to 80 [ms].

The response time of the liquid crystal is longer than one frame period of video (NTSC: 16.67ms). Therefore, as shown in FIG. 1, since the voltage charged in the liquid crystal cell reaches the next frame before the desired voltage, the motion blurring phenomenon in which the screen is blurred in the video appears. In FIG. 1, 'VD' represents a voltage applied to the liquid crystal, and 'RT' represents a response characteristic of the liquid crystal. As can be seen from FIG. 1, when the voltage VD is applied to the liquid crystal, the luminance BL of the light passing through the liquid crystal increases as the orientation of the liquid crystal is changed, but the voltage VD of the next data is due to the slow response time of the liquid crystal. It does not reach the desired luminance BL until it is applied.

V0 V1 V2 V3 V4 V5 V6 V7 V0 - 47 45 42 40 33 27 12 V1 23 - 40 40 37 33 25 12 V2 21 24 - 39 37 30 28 12 V3 21 21 23 - 40 30 25 11 V4 20 22 24 27 - 36 25 11 V5 20 22 24 23 24 - 26 13 V6 20 22 24 26 24 21 - 21 V7 23 25 26 26 26 28 21 -

In Table 1, the left column represents the gradation voltage of previously inputted data, and the uppermost row represents the gradation voltage of the currently inputted data. VO is the voltage of the lowest gradation and shows a higher gradation voltage toward V1, V2, ..., V6, V7.

In order to solve the shortcomings of TN mode liquid crystals, liquid crystals such as In-plane Switching (hereinafter referred to as "IPS") mode and Otically Compensated Bend (hereinafter referred to as "OCB") mode are developed. It has been. Liquid crystal in IPS mode is advantageous in wide viewing angle due to a horizontal electric field, but has a slow response time of 10 to 60 ms. On the other hand, the liquid crystal of the OCB mode is structurally advantageous to the wide viewing angle, and the response time is about 3 to 11 (ms) faster than that of the TN mode liquid crystal.

2A to 2C, liquid crystal molecules 25 injected between the upper substrate 21 and the lower substrate 22 on which the electrodes 22 and 24 are formed are illustrated.

In the initial alignment state, the liquid crystal molecules 25 are arranged in a splay state as shown in FIG. 2A by an alignment layer (not shown). In the splay state, the liquid crystal molecules 25 are arranged at pretilt angles of θ ° and −θ ° on the surfaces of the upper and lower alignment layers, respectively, between the upper substrate 21 and the lower substrate 23. The tilt angle decreases toward the vertical center so that the tilt angle becomes 0 ° from the vertical center. In this splay state, when a voltage is applied to both electrodes 22 and 24 with a potential difference of about 10 V or more, the liquid crystal molecules 25 transition from the splay state to a band state as shown in FIG. 2B. In the band state, the liquid crystal molecules 25 maintain an initial pretilt angle value of ± θ ° on the surface of the upper and lower alignment layers, and the tilt angle increases toward the vertical center, thereby increasing the tilt angle at the vertical center. Is 90 °. When a data voltage is applied to the liquid crystal molecules 25 in the band state, as shown in FIG. 2C, the alignment of the liquid crystal molecules is changed vertically to transmit light. Compared with the TN mode liquid crystal, the TN mode liquid crystal has a longer response time because the liquid crystal alignment is changed vertically at the same time as the twisted arrangement is released, but the OCB mode liquid crystal molecules 25 are directly aligned in the band state. Because it changes vertically, the response time is small.

The gray scale response time of the OCB mode liquid crystal is generally 3 to 11 (ms) as shown in Table 2 when the voltage applied to the liquid crystal cell is V0 to V7.

V0 V1 V2 V3 V4 V5 V6 V7 V0 - 11 10 8 7 6 4 3 V1 4 - 10 9 8 7 5 3 V2 4 5 - 10 9 7 5 3 V3 4 4 5 - 9 8 6 4 V4 4 4 5 6 - 8 6 4 V5 4 4 5 5 6 - 7 4 V6 4 4 5 5 6 6 - 4 V7 3 3 4 4 5 5 6 -

In Table 2, the left column represents the gradation voltage of previously inputted data, and the uppermost row represents the gradation voltage of the currently inputted data. VO is the voltage of the lowest gradation and shows a higher gradation voltage toward V1, V2, ..., V6, V7.

3 is a cross-sectional structure of a liquid crystal display panel capable of color implementation.

Referring to FIG. 3, a common electrode 36 and a color filter 35 are stacked on an upper substrate 37, a pixel electrode 33 is formed on a lower substrate 32, and an upper substrate is formed in the liquid crystal panel. The liquid crystal 34 is injected between the 37 and the lower substrate 32. Under the lower substrate 32, a white lamp 31 serving as a backlight light source is installed. A black matrix (not shown) is formed on the upper substrate 37 between the red, green, and blue color filters 35. An alignment film (not shown) is formed on each of the upper substrate 37 and the lower substrate 32 on an interface in contact with the liquid crystal 34. Gate lines and data lines (not shown) are orthogonal to the lower substrate 32, and TFTs are formed at respective intersections of the gate lines and the data lines. The TFT forms a channel between the source terminal connected to the data line and the drain terminal connected to the pixel electrode 33 in response to a gate pulse applied to its gate terminal via the gate line to the pixel electrode 33. The data voltage is applied. The pixel electrode 33 is formed in the pixel area surrounded by the gate lines and the data lines. In this liquid crystal panel, a voltage is applied to the white lamp 31 as shown in FIG. 4 to continuously radiate white light. While the white lamp 31 is turned on, the TFT is turned on by the gate pulse so that red, green, and blue data voltages are simultaneously applied to the liquid crystal cell. As a result, the white light irradiated to the liquid crystal panel passes through the liquid crystal cell and then passes through the red, green, and blue color filters 35 to change into red light, green light, and blue light. The liquid crystal panel displays a desired color by combining red light, green light and blue light. In FIG. 4, 'RRT', 'GRT', and 'BRT' each represent response characteristics of a liquid crystal cell in which red, green, and blue data voltages are respectively charged. In such a liquid crystal panel, the response time of the liquid crystal for reaching the target level at which the liquid crystal cell can transmit light at a desired luminance when driven at 60 (Hz) is 16.7 (ms). Considering the response time of the liquid crystal, since the liquid crystal of the TN mode or IPS mode has a slow response time, the image quality is degraded in the video. Therefore, the liquid crystal of the OCB mode has a difficult response time. It is faster than 16.7 (ms), so it is more suitable than TN mode or IPS mode when displaying video.

However, the liquid crystal panel as shown in FIG. 3 has a disadvantage of low luminance because light is lost to about 1/3 or less while passing through the color filter 35. Field sequential has been proposed to solve such a decrease in light efficiency.

5 is a schematic cross-sectional view of a liquid crystal panel driven in a field sequential manner.
Referring to FIG. 5, the field sequential liquid crystal panel has no color filter and includes a red lamp 51R, a green lamp 51G, and a blue lamp 51B. A black matrix (not shown) is formed on the upper substrate 57 of the liquid crystal panel. An alignment film (not shown) is formed on each of the upper substrate 57 and the lower substrate 52 on an interface in contact with the liquid crystal 54. Gate lines and data lines (not shown) are orthogonal to the lower substrate 52, and TFTs are formed at respective intersections of the gate lines and the data lines. The TFT forms a channel between the source terminal connected to the data line and the drain terminal connected to the pixel electrode 53 in response to the gate pulse applied to its gate terminal via the gate line to the pixel electrode 53. The data voltage is applied. The pixel electrode 53 is formed in the pixel area surrounded by the gate lines and the data lines. In this field sequential liquid crystal panel, an AC driving voltage is applied to the red lamp 51R, the green lamp 51G, and the blue lamp 51B as shown in FIG. In response to this AC drive voltage, the red lamp 51R turns on at the beginning of the red data voltage being supplied to the liquid crystal cell at the beginning of the frame period, and goes off in the remaining period. The green lamp 51G is turned on in the period in which the green data voltage is supplied to the liquid crystal cell after the red lamp 51R is turned off, and is turned off in the remaining period. The blue lamp 51B is turned on in the later period of the frame period in which the blue data voltage is supplied to the liquid crystal cell after the green lamp 51G is turned off, and is turned off in the remaining period. The liquid crystal cell supplied with the red data voltage transmits red light while the red lamp 51R is turned on, and the liquid crystal cell supplied with the green data voltage transmits green light while the green lamp 51G is turned on. The liquid crystal cell supplied with the blue data voltage transmits blue light while the blue lamp 51B is turned on. As a result, in the field sequential driving method, the red, green, and blue data voltages are time-divided into 1/3 or less of one frame period and supplied to the liquid crystal cell, while time-divided red light, green light, and blue light are transmitted through time division.

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As shown in FIG. 5, the field sequential driving method provides a response voltage (RT) of the liquid crystal as compared to the general driving method as shown in FIG. The response time should be at least three times faster. In detail, since the red lamp 51R, the green lamp 51G, or the blue lamp 51B should be turned on after the voltage is charged to the liquid crystal cell to a target level that can transmit light at a desired luminance, the 60 ( I) In the case of driving, the liquid crystal panel of the field sequential driving method should have a response time of the liquid crystal 54 almost as fast as 16.7 / 3 (ms)-2 (ms: lamp lighting time) = 3.5 (ms). For this reason, the liquid crystals with fast response speed are required for the field sequential drive system like liquid crystal of OCB mode.

The response time of the OCB mode liquid crystal is as fast as 3 to 11 (ms), but even this OCB mode liquid crystal cannot satisfy the response time of 3.5 (ms) or less required in the field sequential driving method. As can be seen from Table 2, the liquid crystal of the OCB mode is driven with a response time of 3.5 (ms) or more in most cases depending on the amount of change whenever the data voltage between gray levels changes. Accordingly, when the liquid crystal of the OCB mode is applied to the liquid crystal panel of the field sequential driving method, the color may be distorted or the luminance may be reduced.

Accordingly, an object of the present invention is to provide a method and apparatus for driving a liquid crystal display device to improve image quality in a field sequential driving method.

In order to achieve the above object, a method of driving a liquid crystal display according to an exemplary embodiment of the present invention includes modulating source data using preset modulation data, time-dividing the modulated data by red, green, and blue. And sequentially irradiating the red light, the green light, and the blue light in synchronization with the time-divided data.

The display panel is characterized in that the OCB (OCB) mode liquid crystal is injected.

According to an exemplary embodiment of the present invention, a method of driving a liquid crystal display includes dividing source data into most significant bits and least significant bits, delaying most significant bits, comparing the most significant bits between frames, and modulating the data according to the comparison result. The method further includes the step of selecting.

The driving method of the liquid crystal display according to the exemplary embodiment of the present invention further includes comparing the source data on a full bit basis in units of frames and selecting modulation data according to the comparison result.

An apparatus for driving a liquid crystal display according to an exemplary embodiment of the present invention includes a display panel, a data modulator for modulating source data using preset modulation data, and time division of the modulated data by red, green, and blue. A data driver for supplying a light source to the display panel, a scan driver for supplying a scanning signal to the display panel, a red lamp for generating red light, a green lamp for generating green light, a blue lamp for generating blue light, and time division And a lamp driver for sequentially turning on and off red light, green light and blue light in synchronization with data.

The data modulator further includes a frame memory for delaying the most significant bit of the source data, and a lookup table for comparing the most significant bit between frames and selecting preset modulation data according to the comparison result.

The data modulator may compare the source data in units of full bits and select modulation data according to the comparison result.

The driving apparatus of the liquid crystal display according to the exemplary embodiment of the present invention further includes a timing controller for controlling the data driver, the scan driver, and the lamp driver, and supplying source data to the data modulator.                     

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 7 to 11.

을 크게 함으로써 액정의 응답속도를 더 빠르게 가속시키게 된다. Referring to FIG. 7, the method and apparatus for driving the liquid crystal display according to the exemplary embodiment of the present invention modulate the input data higher than the input data voltage VD and apply the modulated data voltage MVD to the liquid crystal cell. In FIG. 7, 'RT' represents a response characteristic of a liquid crystal when an unmodulated input data voltage VD is applied to a liquid crystal cell, and 'ART' represents a case where a modulated data voltage MVD is applied to a liquid crystal cell. The response characteristic of the liquid crystal is shown. When the data is modulated, the effective voltage applied to the liquid crystal cell, that is, in Equation 1

By increasing, the response speed of the liquid crystal is accelerated faster.

When the data modulation process is described in detail, the method and apparatus for driving the liquid crystal display according to the exemplary embodiment of the present invention first compare the data input in the previous frame Fn-1 with the data input in the current frame Fn. Subsequently, in the method and apparatus for driving the liquid crystal display according to the exemplary embodiment of the present invention, as compared with the previous data and the currently input data, the currently input data is changed to be higher or lower than the previous data as shown in the following relations ① to ③. In this case, the input data voltage VDn is modulated to a preset value. Data modulation can be performed on a full bit of input digital data, for example 8 bits, but may only modulate a few bits of the most significant bit (MSB) to reduce the burden on hardware.

VDn <VDn-1 ---> MVDn <VDn -------- ①                     

VDn = VDn-1 ---> MVDn = VDn, -------- ②

VDn> VDn-1 ---> MVDn> VDn. -------- ③

In (1) to (3), VDn-1 represents the data voltage of the previous frame, VDn represents the data voltage of the current frame, and MVDn represents the modulated data voltage, respectively.

In order to implement such data modulation in hardware, the driving apparatus of the liquid crystal display according to the exemplary embodiment of the present invention installs a look-up table between the input terminal of the digital data and the data driving circuit. In the lookup table, previous data and currently input data are input, and the modulation data optimally set according to the data change is stored in the internal memory. Table 3 below shows an example of modulation data set for the most significant bit (MSB) of 4 bits and stored in the lookup table.

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

In Table 3, the left column is the most significant 4-bit data input in the previous frame, and the uppermost row is the most significant 4-bit data input in the current frame.                     

The lookup table in which modulation data of Table 3 is stored compares the highest 4-bit data inputted from the previous frame and the current frame, and modulates the data value according to the comparison result. For example, in Table 3, the data value of the most significant 4 bits of the digital data input to the previous frame Fn-1 is '3' and the data value of the most significant 4 bits of the digital data input to the current frame Fn is '4'. If, the lookup table modulates the data value of the most significant bit 4 bits currently input to '5' as shown in FIG. The data driving circuit for supplying data to the data lines of the liquid crystal panel adds the lowest 4 bit data to the modulated highest 4 bit data, and gamma compensates the added digital data to supply the data lines.

The response time of the TN mode liquid crystal when data is modulated by the above-described data modulation method for the TN mode liquid crystal is shown in Table 4 below.

V0 V1 V2 V3 V4 V5 V6 V7 V0 - 16 16 16 16 16 16 12 V1 16 - 16 16 16 16 16 12 V2 16 16 - 16 16 16 16 12 V3 16 16 16 - 16 16 16 11 V4 18 16 16 16 - 16 16 11 V5 19 16 16 16 16 - 16 13 V6 20 16 16 16 16 16 - 21 V7 23 16 16 16 16 16 16 -

In Table 4, the left column represents the gradation voltage of previously inputted data, and the uppermost row represents the gradation voltage of the currently inputted data. VO is the voltage of the lowest gradation and shows a higher gradation voltage toward V1, V2, ..., V6, V7.

As can be seen from the comparison between Table 1 and Table 4, the response time required for 60 (㎐) driving in most gray scale ranges where the response time of TN mode liquid crystal is modulated when data is modulated compared to the case where there is no modulation process. Speeds up within 16.7ms. However, in full-white or full-black gradation, even if data is modulated, the response time of the TN mode liquid crystal exceeds the response time (16.7 ms) required for driving 60 (㎐). Therefore, TN mode liquid crystals and IPS mode liquid crystals are difficult to be applied when the driving frequency is high and the response time is shorter, as in the field sequential driving method. On the other hand, when the OCB mode liquid crystal modulates the data by the above-described data modulation method, the response time is reduced to within the response time (3.5 ms) required when driving at 60 (㎐) or 180 (㎐) as shown in Table 5. .

Table 5 shows the response time of the OCB mode liquid crystal when data is modulated by the above-described data modulation method for the OCB mode liquid crystal.

V0 V1 V2 V3 V4 V5 V6 V7 V0 - 3 3 3 3 3 3 3 V1 4 - 3 3 3 3 3 3 V2 4 3 - 3 3 3 3 3 V3 4 3 3 - 3 3 3 4 V4 4 3 3 3 - 3 3 4 V5 4 3 3 3 3 - 3 4 V6 4 3 3 3 3 3 - 4 V7 3 3 3 3 3 3 3 -

In Table 5, the left column represents the gradation voltage of previously inputted data, and the uppermost row represents the gradation voltage of the currently inputted data. VO is the voltage of the lowest gradation and shows a higher gradation voltage toward V1, V2, ..., V6, V7.

9 illustrates a liquid crystal display of a field sequential driving method according to an embodiment of the present invention.

Referring to FIG. 9, the liquid crystal display of the field sequential driving method according to the embodiment of the present invention includes a liquid crystal panel 86 in which a data line 84 and a gate line 85 cross each other and a TFT is formed at an intersection thereof. A data driver 82 for supplying data to the data line 84 of the liquid crystal panel 86, a gate driver 89 for supplying scanning pulses to the gate line 85 of the liquid crystal panel 86, and digital A timing controller 80 to which video data and synchronization signals H and V are supplied, and a data modulator 81 connected between the timing controller 80 and the data driver 82 to modulate the data RGB; And an OCB reset unit 88 for initializing the OCB mode liquid crystal, and a lamp driver 90 for driving the red lamp 87R, the green lamp 87G, and the blue lamp 87B.

In the liquid crystal panel 86, liquid crystal oriented in OCB mode is injected between two glass substrates. TFTs formed at the intersections of the data lines 84 and the gate lines 85 of the liquid crystal panel 86 generate data on the data lines 84 in response to the scanning pulses from the gate driver 89 in the OCB mode. Supply to the liquid crystal cell (Clc). The source electrode of this TFT is connected to the data line 84, and the drain electrode is connected to the pixel electrode of the liquid crystal cell Clc. The gate electrode of the TFT is connected to the gate line 85.

The timing controller 80 rearranges the digital video data supplied from the digital video card (not shown) for each of red (R), green (G), and blue (B). The data RGB rearranged by the timing controller 80 is supplied to the data modulator 81. In addition, the timing controller 80 controls the data control signal DDC and the gate at a frequency required for the field sequential driving method, that is, a frequency of 180 (Hz) or more, using the horizontal / vertical synchronization signals H and V input to the timing controller 80. Generate signal GDC. The data control signal DDC is supplied to the data driver 82 including a dot clock Dclk, a source shift clock SSC, a source enable signal SOE, a polarity inversion signal POL, and the like. The gate control signal GDC is supplied to the gate driver 89 including a gate start pulse GSP, a gate shift clock GSC, a gate output enable GOE, and the like. In addition, the timing controller 80 senses a time point when the power is turned on to drive the OCB reset unit 88 and control the lamp driver 90.

The data modulator 81 compares only the most significant bit MSB between the previous frame Fn-1 and the current frame Fn and modulates the data RGB into modulated data previously stored in the lookup table. The data modulator 81 compares the data RGB between the previous frame Fn-1 and the current frame Fn by a full bit, for example, 8 bits, and sets the 8-bit bandwidth in the lookup table according to the comparison result. Modulation data may be selected to modulate the data RGB.

The data driver 82 samples the data modulated by the data modulator 81 according to the data control signal DDC from the timing controller 51, and then latches the sampled data by one line and latches the latched data. The gamma voltage supply unit 83 converts the analog gamma voltage.

The gate driver 89 includes a shift register that sequentially generates scan pulses in response to the gate control signal GDC from the timing controller 80, and sets the voltage of the scan pulses to a voltage level suitable for driving the liquid crystal cell Clc. Includes a level shifter for shifting. The TFT is turned on in response to this scan pulse. When the TFT is turned on, video data on the data line 84 is supplied to the pixel electrode of the liquid crystal cell Clc.

The OCB reset unit 88 is driven when the power is turned on under the control of the timing controller 80 to transfer a voltage for transferring the OCB mode liquid crystal in the liquid crystal panel 86 from the splay mode to the band mode. ) To the data lines 84. At the same time, when the voltage for transitioning from the splay mode to the band mode is supplied to the data lines 84, the OCB reset unit 88 controls the gate driver 89 to sequentially scan pulses to the gate lines 85. To supply.

The lamp driver 90 sequentially turns on and off the red lamp 87R, the green lamp 87G and the blue lamp 87B within one frame period under the control of the timing controller 90. As illustrated in FIG. 6, the red lamp 87R is turned on when red data is completely charged in the OCB mode liquid crystal cell Clc, and is turned off before the green data is supplied to the data lines 84. The green lamp 87G is turned on when the green data is completely charged in the OCB mode liquid crystal cell Clc as shown in FIG. 6, and is turned off before the blue data is supplied to the data lines 84. As illustrated in FIG. 6, the blue lamp 87B is turned on when the blue data is completely charged in the OCB mode liquid crystal cell Clc, and is turned off before the red data is supplied to the data lines 84.

The waveforms of the data, the scan signal, and the lamp driving signal generated from the liquid crystal display are substantially the same as in FIG. 6.

10 shows the data modulator 81 in detail.                     

Referring to FIG. 10, the data modulator 81 is commonly connected to the frame memory 103 connected to the upper bit bus line 102 and the output terminals of the upper bit bus line 102 and the frame memory 103. A lookup table 104 is provided.

The frame memory 103 stores the most significant bit MSB for one frame period and supplies the stored data to the lookup table 104. Here, the most significant bit MSB is set to the upper four bits among the eight bits of source data RGB.

The lookup table 104 selects the most significant bit MSB of the current frame Fn supplied from the upper bit bus line 102 and the most significant bit MSB of the previous frame Fn-1 supplied from the frame memory 103. After comparison, Table 1 and pre-stored modulation data MMSB are selected according to the comparison result.

The most significant bit modulated data MMSB selected by the lookup table 104 is added to the least significant bit LSB supplied from the lower bit bus line 101 and supplied to the data driver 82.

Meanwhile, as illustrated in FIG. 11, the data modulator 81 is a frame memory 111 that stores 8 bits of full bits and a lookup table 112 that outputs full bits of modulated data by comparing normal data of the full bits. It can also be configured to modulate data in units of full bits.

As described above, the method and apparatus for driving a liquid crystal display according to the present invention inject a liquid crystal oriented in an OCB mode into a liquid crystal panel in a liquid crystal display device driven by a field sequential driving method and apply a voltage applied to the OCB mode liquid crystal. It will modulate the data to increase it. As a result, the method and apparatus for driving the liquid crystal display according to the present invention can drive the liquid crystal within the response time required in the field sequential driving method, thereby minimizing the deterioration of the image quality in the field sequential driving method, thereby improving the image quality.

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. For example, the data modulator may be implemented in the form of a program and a microprocessor for executing the program in addition to the lookup table. 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 (8)

Modulating the source data using the preset modulation data; Time-dividing the modulated data into red, green, and blue colors and supplying the modulated data to a display panel; Sequentially irradiating red light, green light and blue light in synchronization with the time-divided data, Modulating the source data, Dividing the source data into most significant bits and least significant bits; Delaying the most significant bit; And comparing the most significant bit between frames and selecting the modulated data according to the comparison result. The method of claim 1, And an OCB (OCB) mode liquid crystal is injected into the display panel. delete delete Display panel, A data modulator for modulating source data using preset modulation data; A data driver for time division of the modulated data into red, green, and blue colors and supplying the modulated data to the display panel; A scan driver for supplying a scanning signal to the display panel; A red lamp for generating red light, A green lamp for generating green light, A blue lamp for generating blue light, A lamp driver for sequentially turning on and off red light, green light, and blue light in synchronization with the time-divided data; The data modulator, A frame memory for delaying the most significant bit of the source data; And a lookup table for comparing the most significant bit between frames and selecting the preset modulation data according to the comparison result. delete delete The method of claim 5, wherein And a timing controller for controlling the data driver, the scan driver, and the lamp driver, and supplying the source data to the data modulator.

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