KR20070081521A - Driving apparatus for liquid crystal display and liquid crystal display including the same - Google Patents

Abstract

A driving apparatus and an LCD device the same are provided to enhance a contrast ratio between dark regions by adjusting a gradation voltage generator using a gradation voltage controller. A driving apparatus of an LCD(Liquid Crystal Display) device includes a signal controller(600) for processing input image data(R,G,B), a back light unit for supplying light to a liquid crystal assembly, and a gradation voltage generator for generating a reference gradation voltage. The signal controller includes a data analyzer(601), and backlight and gradation voltage controllers(603,605). The data analyzer analyzes the input image data and generates a histogram according to the result. The backlight and gradation voltage controllers which are connected to the data analyzer generate first and second control signals(CONT4,CONT3) based on the histogram, respectively.

Description

A driving device of a liquid crystal display and a liquid crystal display including the same {DRIVING APPARATUS FOR LIQUID CRYSTAL DISPLAY AND LIQUID CRYSTAL DISPLAY INCLUDING THE SAME}

With reference to the accompanying drawings will be described in detail the embodiments of the present invention to make the present invention clear.

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

2 is an equivalent circuit diagram of one pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 3 is a schematic block diagram of the signal controller shown in FIG. 1.

FIG. 4 is an example of a circuit diagram of the gray voltage generator shown in FIG. 1.

FIG. 5 is a diagram illustrating a change of an image appearing in a liquid crystal display according to an exemplary embodiment of the present invention, together with a histogram.

<Description of Drawing>

3: liquid crystal layer 100: lower display panel

191: pixel electrode 200: upper display panel

230: color filter 270: common electrode

300: liquid crystal panel assembly 400: gate driver

500: data driver 600: signal controller

601: data analyzer 603: gray voltage controller

605: backlight controller 800: gray voltage generator

900: backlight

R, G, B: Input image data DE: Data enable signal

MCLK: Main Clock Hsync: Horizontal Sync Signal

Vsync: Vertical Sync Signal CONT1: Gate Control Signal

CONT2: data control signal DAT: digital video signal

Clc: Liquid Crystal Capacitor Cst: Keeping Capacitor

Q: switching device

The present invention relates to a driving device of a liquid crystal display and a liquid crystal display including the same.

A typical liquid crystal display (LCD) includes two display panels provided with pixel electrodes and a common electrode, and a liquid crystal layer having dielectric anisotropy interposed therebetween. The pixel electrodes are arranged in a matrix and connected to switching elements such as thin film transistors (TFTs) to receive data voltages one by one in sequence. The common electrode is formed over the entire surface of the display panel and receives a common voltage. The pixel electrode, the common electrode, and the liquid crystal layer therebetween form a liquid crystal capacitor, and the liquid crystal capacitor becomes a basic unit that forms a pixel together with a switching element connected thereto.

In such a liquid crystal display, a voltage is applied to two electrodes to generate an electric field in the liquid crystal layer, and the intensity of the electric field is adjusted to adjust the transmittance of light passing through the liquid crystal layer to obtain a desired image. In this case, the light may be a separate artificial light source or natural light.

The liquid crystal display device supplies light by placing an artificial light source called a backlight unit as a light receiving element.

On the other hand, when black is displayed, light leakage may occur to prevent black from being properly implemented. In this case, black is implemented by adjusting the amount of light emitted from the backlight unit. However, in this case, the screen becomes dark overall, and it is difficult to distinguish between gray levels in the dark part.

Accordingly, an object of the present invention is to provide a driving device for a liquid crystal display device and a liquid crystal display device including the same, which can solve the problems of the related art.

According to an exemplary embodiment of the present invention, a driving device of a liquid crystal display device including a liquid crystal panel assembly having a plurality of pixels includes: a signal controller for processing and outputting input image data from the outside; A backlight unit providing light to the display panel assembly, and a gray voltage generator generating and outputting a reference gray voltage;

The signal controller may be connected to a data analyzer configured to generate the histogram by analyzing the input image data, and a backlight controller and a gray scale configured to generate first and second control signals based on the histogram, respectively. And a voltage controller.

In this case, the histogram may represent the number of pixels according to luminance.

The input image data may include black data having a low luminance, white data having a high luminance, and intermediate data having an intermediate luminance.

The input image data may include a plurality of gray scales, the black data may include a first gray scale and a second gray scale slightly larger than the gray scale, and the backlight may receive the first control signal to reduce the amount of light. have.

The intermediate data or the white data may include a third gray level, and the gray voltage generator may receive the second control signal and increase the gray voltage for the second gray level and the third gray level.

On the other hand, the liquid crystal display device according to an embodiment of the present invention, a liquid crystal panel assembly having a plurality of pixels, a signal controller for processing and outputting the input image data from the outside, a backlight unit for providing light to the liquid crystal panel assembly, And a gray voltage generator which generates and exports a reference gray voltage.

The signal controller may be connected to a data analyzer configured to generate the histogram by analyzing the input image data, and a backlight controller and a gray scale configured to generate first and second control signals based on the histogram, respectively. It may include a voltage controller.

In this case, the histogram may represent the number of pixels according to luminance.

The input image data may include black data having a low luminance, white data having a high luminance, and intermediate data having an intermediate luminance.

The input image data may include a plurality of gray scales, the black data may include a first gray scale and a second gray scale slightly larger than the gray scale, and the backlight may receive the first control signal to reduce the amount of light. have.

The intermediate data or the white data may include a third gray level, and the gray voltage generator may receive the second control signal and increase the gray voltage for the second gray level and the third gray level.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

First, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel of the liquid crystal display according to an exemplary embodiment of the present invention. 3 is a schematic block diagram of the signal controller shown in FIG. 1, and FIG. 4 is an example of a circuit diagram of the gray voltage generator shown in FIG. 1.

As shown in FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel assembly 300, a gate driver 400, a data driver 500, and a data driver 500 connected thereto. The gray voltage generator 800, the backlight 900, and a signal controller 600 controlling the gray voltage generator 800 connected to the 500 are included.

The liquid crystal panel assembly 300 may include a plurality of signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels PX connected to the plurality of signal lines G ₁ -G _n , D ₁ -D _m , and arranged in a substantially matrix form. Include. On the other hand, in the structure shown in FIG. 2, the liquid crystal panel assembly 300 includes lower and upper panels 100 and 200 facing each other and a liquid crystal layer 3 interposed therebetween.

The signal lines G ₁ -G _n and D ₁ -D _m are a plurality of gate lines G ₁ -G _n for transmitting a gate signal (also called a “scan signal”) and a plurality of data lines for transmitting a data signal ( D ₁ -D _m ). The gate lines G ₁ -G _n extend substantially in the row direction and are substantially parallel to each other, and the data lines D ₁ -D _m extend substantially in the column direction and are substantially parallel to each other.

Each pixel PX, for example, the pixel PX connected to the i-th (i = 1, 2,, n) gate line G _i and the j-th (j = 1, 2,, m) data line Dj. ) Includes a switching element Q connected to the signal line G _i D _j , a liquid crystal capacitor Clc, and a storage capacitor Cst connected thereto. Holding capacitor Cst can be omitted as needed.

The switching element Q is a three-terminal element of a thin film transistor or the like provided in the lower panel 100, the control terminal of which is connected to the gate line G _i , and the input terminal of which is connected to the data line D _j . The output terminal is connected to the liquid crystal capacitor Clc and the storage capacitor Cst.

The liquid crystal capacitor Clc has two terminals, the pixel electrode 191 of the lower panel 100 and the common electrode 270 of the upper panel 200, and the liquid crystal layer 3 between the two electrodes 191 and 270 is a dielectric material. Function as. The pixel electrode 191 is connected to the switching element Q, and the common electrode 270 is formed on the front surface of the upper panel 200 and receives the common voltage Vcom. Unlike in FIG. 2, the common electrode 270 may be provided in the lower panel 100. In this case, at least one of the two electrodes 191 and 270 may be formed in a linear or bar shape.

The storage capacitor Cst, which serves as an auxiliary part of the liquid crystal capacitor Clc, is formed by overlapping a separate signal line (not shown) and the pixel electrode 191 provided on the lower panel 100 with an insulator interposed therebetween. A predetermined voltage such as the common voltage Vcom is applied to the separate signal line. However, the storage capacitor Cst may be formed such that the pixel electrode 191 overlaps the front gate line directly above the insulator.

On the other hand, in order to implement color display, each pixel PX uniquely displays one of the primary colors (spatial division) or each pixel PX alternately displays the primary colors over time (time division). The desired color is recognized by the spatial and temporal sum of these primary colors. Examples of the primary colors include three primary colors such as red, green, and blue. FIG. 2 illustrates that each pixel PX includes a color filter 230 representing one of the primary colors in an area of the upper panel 200 corresponding to the pixel electrode 191 as an example of spatial division. Unlike FIG. 2, the color filter 230 may be formed above or below the pixel electrode 191 of the lower panel 100.

At least one polarizer (not shown) for polarizing light is attached to an outer surface of the liquid crystal panel assembly 300.

The gray voltage generator 800 generates two sets of gray voltages (or reference gray voltage sets) related to the transmittance of the pixel PX. One of the two sets has a positive value for the common voltage Vcom and the other set has a negative value.

3 illustrates an example of such a gray voltage generator 800.

The gray voltage generator 800 is connected to the multiplexers 840 and 850 connected to the pair of gamma registers 820 and 830 and the rear gamma register 830 by a 10-bit bus, and each multiplexer 840 and 850. A plurality of rows of resistors 841 and 851.

The gamma registers 820 and 830 receive and store the gray voltage control signal CONT4 from the signal controller 600, and the gray voltage control signal CONT4 is a digital value.

The multiplexers 840 and 850 select two of the voltages divided by the resistor strings 841 and 851 by using digital values stored in the gamma registers 820 and 830 as a selection signal, thereby converting the two bus wirings into analog voltages. Output to the data driver 500 through. For example, as shown, the most significant one bit of the 10-bit data is used as a selection signal for opening and closing the switching elements SW1 and SW2, and the remaining 9 bits are used as the selection signals of the multiplexers 840 and 850. In the case of 9 bits, all 512 can be selected. In this case, the multiplexer 840 may output 8 positive reference voltages, and the multiplexer 850 may output 8 negative reference voltages, respectively, and the output analog voltage GAM_IN may be the buffer 860. Amplified through, it is supplied to the data driver 500 as described above.

Both ends of each of the resistor strings 841 and 851 are connected to constant reference voltages VREF1, VREF2, VREF3 and VREF4, respectively, and the centers of the resistor strings 841 and 851 are respectively fixed to the constant center voltages VCNT1 and VCNT2. It is connected.

A gate driver 400, a gate line (G ₁ -G _n) and is connected to the gate turn-on voltage (Von), and a gate signal consisting of a combination of a gate-off voltage (Voff), a gate line (G ₁ of the liquid crystal panel assembly 300 -G _n ).

The data driver 500 is connected to the data lines D ₁ -D _m of the liquid crystal panel assembly 300, and selects a gray voltage from the gray voltage generator 800 and uses the data line D as a data signal. ₁ -D _m ). However, when the gray voltage generator 800 provides only a predetermined number of reference gray voltages instead of providing all of the voltages for all grays, the data driver 500 divides the reference gray voltages to divide the gray voltages for all grays. Generate and select the data signal from it.

The backlight unit 900 includes an inverter 910 and a light source unit 920 to provide light to the liquid crystal panel assembly 300.

As illustrated in FIG. 4, the signal controller 600 receives image data R, G, and B and analyzes the number of pixels according to luminance, and a gray voltage controller 603 connected thereto. And a backlight controller 605. The signal controller 600 controls the gate driver 400, the data driver 500, the gray voltage generator 800, the backlight 900, and the like.

Each of the driving devices 400, 500, 600, and 800 may be mounted directly on the liquid crystal panel assembly 300 in the form of at least one integrated circuit chip, or may be a flexible printed circuit film (not shown). It may be mounted on the liquid crystal panel assembly 300 in the form of a tape carrier package (TCP) or mounted on a separate printed circuit board (not shown). Alternatively, these driving devices 400, 500, 600, and 800 may be integrated in the liquid crystal panel assembly 300 together with the signal lines G ₁ -G _n , D ₁ -D _m and the thin film transistor switching element Q. It may be. In addition, the driving devices 400, 500, 600, and 800 may be integrated into a single chip, in which case at least one of them or at least one circuit element constituting them may be outside the single chip.

Next, the operation of the liquid crystal display will be described in detail.

The signal controller 600 receives input image signals R, G, and B and an input control signal for controlling the display thereof from an external graphic controller (not shown). Examples of the input control signal include a vertical sync signal Vsync, a horizontal sync signal Hsync, a main clock MCLK, and a data enable signal DE.

The signal controller 600 properly processes the input image signals R, G, and B according to operating conditions of the liquid crystal panel assembly 300 based on the input image signals R, G, and B and the input control signal, and controls the gate. After generating the signal CONT1, the data control signal CONT2, the inverter control signal CONT3, the gray voltage control signal CONT4, and the like, the gate control signal CONT1 is sent to the gate driver 400, and the data control signal ( CONT2) and the processed image signal DAT are sent to the data driver 500. In addition, the inverter control signal CONT3 is sent to the inverter 910 of the backlight unit 900, and the gray voltage control signal CONT4 is sent to the gray voltage generator 800.

The gate control signal CONT1 includes a scan start signal STV indicating a scan start and at least one clock signal controlling an output period of the gate-on voltage Von. The gate control signal CONT1 may also further include an output enable signal OE that defines the duration of the gate-on voltage Von.

The data control signal CONT2 is a load for applying a data signal to the horizontal synchronization start signal STH and the data lines D ₁ -D _m indicating the start of image data transmission for the pixels PX in one row [bundling]. Signal LOAD and data clock signal HCLK. The data control signal CONT2 is also an inverted signal that inverts the voltage polarity of the data signal relative to the common voltage Vcom (hereinafter referred to as " polarity of the data signal " by reducing the " voltage polarity of the data signal for the common voltage &quot;) RVS) may be further included.

According to the data control signal CONT2 from the signal controller 600, the data driver 500 receives the digital image signal DAT for the pixels PX in one row (bundling), and each digital image signal DAT. By converting the digital image signal DAT into an analog data signal by selecting a gray scale voltage corresponding to), it is applied to the corresponding data lines D ₁ -D _m .

The gate driver 400 applies the gate-on voltage Von to the gate lines G ₁ -G _n in response to the gate control signal CONT1 from the signal controller 600, thereby applying the gate lines G ₁ -G _n . Turn on the switching element (Q) connected to. Then, the data signal applied to the data lines D ₁ -D _m is applied to the pixel PX through the switching element Q turned on.

The difference between the voltage of the data signal applied to the pixel PX and the common voltage Vcom is shown as the charging voltage of the liquid crystal capacitor Clc, that is, the pixel voltage. The arrangement of the liquid crystal molecules varies depending on the magnitude of the pixel voltage, thereby changing the polarization of light passing through the liquid crystal layer 3. The change in polarization is represented by a change in transmittance of light by a polarizer attached to the display panel assembly 300.

This process is repeated in units of one horizontal period (also referred to as "1H" and equal to one period of the horizontal sync signal Hsync and the data enable signal DE), thereby all the gate lines G ₁ -G _n. ), The gate-on voltage Von is sequentially applied to the data signal to all the pixels PX, thereby displaying an image of one frame.

When one frame ends, the state of the inversion signal RVS applied to the data driver 500 is controlled so that the next frame starts and the polarity of the data signal applied to each pixel PX is opposite to the polarity of the previous frame. "Invert frame"). In this case, the polarity of the data signal flowing through one data line is changed (eg, row inversion and point inversion) or the polarity of the data signal applied to one pixel row is different depending on the characteristics of the inversion signal RVS within one frame. (E.g. column inversion, point inversion).

Next, an operation of the driving apparatus of the liquid crystal display according to the exemplary embodiment of the present invention will be described in detail with reference to FIG. 5.

5 is a diagram illustrating a process of processing image data input to a liquid crystal display according to an exemplary embodiment of the present invention with a histogram.

Here, an example of an image (hereinafter, referred to as an original image) that can be displayed by the input image data R, G, and B is shown on the left side of FIG. On the left side of b), the original image shown in FIG. 5A is displayed by controlling the backlight unit 900. On the left side of FIG. 5C, the image shown in FIG. 5B is shown. An image displayed by controlling the gray voltage generator 800 is illustrated.

5 (a) to (c), the bar graph shows the luminance represented by each region (x, x ', x ", y, y') and the number of pixels according to the luminance in the image shown on the left. More specifically, when the image data R, G, and B are 8-bit signals, the histogram can be represented by 256 gray scales, ranging from 0 gray scale to 255 gray scales. Assuming that the liquid crystal display is normally black mode, it has a gamma curve that increases in luminance when the gray scale increases, and hereinafter, black data when the image data R, G, and B are near zero gray scale. For example, when 255 gradations are near, white data is called, and gradation between them is called intermediate data.

The data analyzer 601 of the signal controller 600 analyzes the luminance of the input image data R, G, and B and generates a histogram of the number of pixels according to the luminance.

For example, as illustrated in FIG. 5A, image data R, G, and B in which the original image may be represented by a dark area x, a slightly darker area x ', and a bright area y are shown. ) Is input, the luminance for each area (x, x ', y) is obtained and the number of pixels having the luminance is obtained.

On the other hand, this information is sent to the gray scale voltage controller 603 and the backlight controller 605, respectively.

As shown in FIG. 5A, the backlight controller 605 receives the backlight control signal CONT3 when the input image data R, G, and B include black data near zero gray scale and other intermediate data. Export to the inverter 910 of the backlight unit 900.

The inverter 910 adjusts the brightness of the image by adjusting the amount of light emitted from the light source unit 920, and produces an image as shown on the left in FIG. That is, as shown in the histogram on the right side, the luminance of the image is lowered to move slightly to the left about the reference lines RL1 and RL2. However, the histograms shown in FIGS. 5B and 5C are not generated by the data analyzer 601, but are shown according to FIG. 5A only for convenience of description.

Each area (x, x ', y) of the original image moves to a slightly darker area (x', x ", y '), especially the dark areas (x, x') of the original image are darker than the original It shows more accurate black, that is, when the original image is displayed as it is, blurry black due to light leakage becomes clear.

However, when the gray level difference between the two areas (x, x ') of the original image is not very small, the difference in luminance is insignificant in the two areas (x', x ") of FIG. As a result, the contrast ratio may drop.

This phenomenon is improved by the gray voltage controller 603 generating the gray voltage control signal CONT4 to control the gray voltage generator 800.

That is, the gray voltage generator 800 receiving the gray voltage control signal CONT4 increases the reference voltage for data corresponding to the two areas x and y except for the darker area x 'of the original image. Export to the data driver 500. As such, when the reference voltage for the data corresponding to the two areas (x, y) of the original image is increased, the light emitted from the backlight unit 900 may be reduced, so that the overall dark image may have the same brightness as the original image. .

Through this processing, the dark region x 'of the original image is changed to a darker region x ", and the two regions x and y of the original image restore the original brightness. In the histogram shown in Fig. 2), region x "coincides with reference line RL3, region x 'coincides with reference line RL1, and region y coincides with reference line RL2.

Thus, while displaying a clear black, the two dark areas (x, x ") are different in brightness and the contrast ratio is high.

In this way, it is possible to clearly display black even when black is not clearly displayed due to light leakage, and also to increase the contrast ratio between dark areas.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (10)

A driving device of a liquid crystal display device comprising a liquid crystal panel assembly provided with a plurality of pixels, A signal controller which processes and exports input image data from outside; A backlight unit providing light to the liquid crystal panel assembly, and Gray voltage generator to generate and export the reference gray voltage Including, The signal controller A data analyzer which analyzes the input image data and generates a histogram; A backlight controller and a gray voltage controller which are connected to the data analyzer and generate first and second control signals based on the histogram, respectively. Containing Driving device for liquid crystal display device. In claim 1, And the histogram represents the number of pixels according to luminance. In claim 2, And the input image data includes black data having a low luminance, white data having a high luminance, and intermediate data having an intermediate luminance. In claim 3, The input image data includes a plurality of gray levels, The black data includes a first gray scale and a second gray scale slightly larger than this, The backlight unit receives the first control signal and reduces the amount of light. Driving device for liquid crystal display device. In claim 4, The intermediate data or the white data includes a third gray scale, The gray voltage generator receives the second control signal and outputs the gray voltages for the second gray and the third gray by increasing them. Driving device for liquid crystal display device. A liquid crystal panel assembly having a plurality of pixels, A signal controller which processes and exports input image data from outside; A backlight unit providing light to the liquid crystal panel assembly, and Gray voltage generator to generate and export the reference gray voltage Including, The signal controller A data analyzer which analyzes the input image data and generates a histogram; A backlight controller and a gray voltage controller which are connected to the data analyzer and generate first and second control signals based on the histogram, respectively. Containing Liquid crystal display. In claim 6, And the histogram represents the number of pixels according to luminance. In claim 7, The input image data includes black data having a low luminance, white data having a high luminance, and intermediate data having an intermediate luminance. In claim 8, The input image data includes a plurality of gray levels, The black data includes a first gray scale and a second gray scale slightly larger than this, The backlight unit receives the first control signal and reduces the brightness of the light. Liquid crystal display. In claim 9, The intermediate data or the white data includes a third gray scale, The gray voltage generator receives the second control signal and outputs the gray voltages for the second gray and the third gray by increasing them. Liquid crystal display.

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