KR20080054567A - Display device - Google Patents

Abstract

A display apparatus is provided to prevent rain falling by outputting constant data voltages during a voltage input time difference between a data driver and a gray scale generator. A display apparatus includes plural pixels, a gate driver(400), a gray scale voltage generator(800), a data driver(500), and a signal controller(600). The gate driver supplies gate signals to the pixels. The gray scale voltage generator generates plural gray scale voltages by dividing a reference voltage. The data driver selects one of the plural gray scale voltages according to image signals and supplies the selected gray scale voltage as a data signal to the pixels. The signal controller generates the reference voltage and a driving voltage of the data driver, synchronizes the reference voltage with the driving voltage, and supplies the synchronized voltages to the gray scale voltage generator and the data driver.

Description

Display device {DISPLAY DEVICE}

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 in a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a signal waveform diagram illustrating an operation of a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a block diagram of a voltage output unit of a liquid crystal display according to another exemplary embodiment of the present invention.

The present invention relates to a display device.

In recent years, with the reduction in weight and thickness of personal computers and televisions, display devices are also required to be lighter and thinner, and cathode ray tubes (CRTs) are being replaced by flat panel displays.

Such flat panel displays include liquid crystal displays (LCDs), field emission displays (FEDs), organic light emitting displays, plasma display panels (PDPs), and the like. There is this. In general, in an active flat panel display, a plurality of pixels arranged in a matrix form is arranged in a matrix form, and an image is displayed by controlling luminance of each pixel according to given image information.

The luminance information is output as a digital image signal from the signal controller of the display device, and the signal is converted into an analog data voltage by a digital-analog converter of the data driver and supplied to the corresponding pixel. The digital-to-analog converter is supplied with a plurality of gray voltages generated by a gray voltage generator made of a resistor string, and the digital-analog converter selects a gray voltage corresponding to the digital image signal from the gray voltage and outputs it as a data voltage.

On the other hand, the voltage source differs from the driving voltage for controlling the operation of the data driver and the gray reference voltage which is the basis of the gray voltage of the gray voltage generator. Therefore, when the time for outputting the respective voltages from the signal controller does not match, the data driver outputs an abnormal voltage and the raining phenomenon is observed.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a liquid crystal display for preventing rain from occurring during initial driving.

According to an exemplary embodiment of the present invention, a display device includes a plurality of pixels, a gate driver supplying a gate signal to the pixels, a gray voltage generator generating a plurality of gray voltages by dividing a reference voltage; Selecting one of the plurality of gray voltages according to an image signal to generate a data driver for supplying the pixel as a data signal, and generating a reference voltage and a driving voltage of the data driver to synchronize the reference voltage and the driving voltage. And a signal controller for supplying the gray voltage generator and the data driver, respectively.

The signal controller may include a voltage output unit configured to output the driving voltage to the data driver according to the reference voltage.

The voltage output unit includes a control terminal connected to the reference voltage, a first terminal connected to a first voltage, a first transistor including a second terminal, and a control connected to a second terminal of the first transistor. A second transistor may include a terminal, a first terminal connected to the second voltage, and a second terminal connected to the data driver.

The first voltage may be a turn on voltage level of the second transistor.

The second voltage may be a driving voltage of the data driver.

The voltage output unit may further include a resistor between the second voltage and the second transistor.

The resistance may be determined according to the magnitude of the second voltage and the driving voltage of the data driver.

In addition, the display device according to another exemplary embodiment of the present invention may operate in accordance with a plurality of pixels, a gate driver for supplying a gate signal to the pixels, a gray voltage generator for generating a plurality of gray voltages by dividing a reference voltage, and a driving voltage. And a data driver to select one of the plurality of gray voltages according to an image signal and to supply the pixel as a data signal, wherein the data driver includes a predetermined voltage until the reference voltage is supplied to the gray voltage generator. Is supplied to the pixel as the data signal.

The data driver may supply a voltage corresponding to black to the pixel until the reference voltage is supplied to the gray voltage generator.

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.

A liquid crystal display, which is one example of a display device, will now 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 in the liquid crystal display according to an exemplary embodiment of the present invention.

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 connected to the signal generator 500 and a signal controller 600 for controlling the gray voltage generator 800 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 voltage ( 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, is connected to the i-th (i = 1, 2, ..., n) gate line G _i and the j-th (j = 1, 2, ..., m) data line D _j . The pixel PX includes a switching element Q connected to the signal lines G _i and 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 thin film transistor may include polycrystalline silicon or amorphous silicon.

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 in FIG. 2, the color filter 230 may be disposed 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.

Referring back to FIG. 1, the gray voltage generator 800 generates two sets of gray voltages 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. The number of gray voltages included in the set of gray voltages generated by the gray voltage generator 800 may be the same as the number of grays that the liquid crystal display can display.

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 ).

Data driver 500 is connected with the data lines (D ₁ -D _m) of the liquid crystal panel assembly 300, select a gray voltage from the gray voltage generator 800 and the data lines do this as a data voltage (D ₁ -D _m ).

The signal controller 600 controls the gate driver 400, the data driver 500, the gray voltage generator 800, and the like, and outputs a driving voltage to the data driver 500 (not shown). It includes. This voltage output unit (not shown) will be described in detail later.

Each of the 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 switching element Q. Alternatively, these driving devices 400, 500, 600, 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 may be mounted on a separate printed circuit board (not shown). 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). The input image signals R, G, and B contain luminance information of each pixel PX, and the luminance is a predetermined number, for example, 1024 (= 2 ¹⁰ ), 256 (= 2 ⁸ ), or 64 (= 2 ⁶ ) It has gray. 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 and the data control signal CONT2, 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 transmitted to the data driver 500. Export to).

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 applies an analog data voltage to the horizontal synchronizing start signal STH and the data lines D ₁ -D _m indicating the start of transmission of the digital image signal DAT for one row of pixels PX. Includes a load signal LOAD and a data clock signal HCLK. The data control signal CONT2 is also an inverted signal that inverts the voltage polarity of the analog data voltage relative to the common voltage Vcom (hereinafter referred to as " polarity of the data voltage " 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 pixel PX in one row and corresponds to each digital image signal DAT. By selecting the gray scale voltage, the digital image signal DAT is converted into an analog data voltage and then 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 voltage applied to the data lines D ₁ -D _m is applied to the pixel PX through the turned-on switching element Q.

The difference between the voltage of the data voltage applied to the pixel PX and the common voltage Vcom is shown as the charging voltage of the liquid crystal capacitor C _LC , 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 the transmittance of light by a polarizer attached to the display panel assembly 300, whereby the pixel PX displays the luminance represented by the gray level of the image signal DAT.

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, and the data voltage is applied to all the pixels PX to display 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 voltage applied to each pixel PX is opposite to the polarity of the previous frame. "Invert frame"). In this case, the polarities of the data voltages flowing through one data line may be changed (eg, row inversion and point inversion), or polarities of data voltages applied to one pixel row may be different depending on the characteristics of the inversion signal RVS within one frame. (E.g. column inversion, point inversion).

Hereinafter, a liquid crystal display capable of preventing rain from falling will be described with reference to FIGS. 3 to 4.

3 is a signal waveform diagram illustrating an operation of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the signal controller 600 generates a driving voltage VDD instructing the operation of the data driver 500 based on the first voltage Vin. In addition, the signal controller 600 generates a gray reference voltage AVDD of the gray voltage generator 800 through a DC-DC converter.

However, it takes time for the signal controller 600 to read the data stored in the EEPROM or the like to operate the DC-DC converter, so that the output of the driving voltage VDD and the gray reference voltage AVDD may not occur at the same time. In this case, since the gray voltage generator 800 does not output the gray voltage to the data driver 500, the data driver 500 outputs an arbitrary voltage as the data voltage Vdat, thereby causing an abnormal output, that is, a non-falling phenomenon. The back is visually recognized.

At this time, the signal controller 600 according to an exemplary embodiment of the present invention outputs the data control signal CONT2 to the data driver 500 to output the preparation period T1, that is, the gray voltage reference voltage after the driving voltage VDD is output. The output of the data driver 500 is controlled until the AVDD is output.

As shown in FIG. 3, when the data voltage Vdat is maintained at a fixed level of the fixed voltage V1 during the preparation period T1, the pixels PX in each column of the liquid crystal panel assembly 300 display the same color to display the same color. Phenomenon such as falling can be prevented. In addition, when outputting a voltage corresponding to the gray level of the black with a fixed voltage (V1), it is recognized as a non-display period can improve the recognition.

4 is a block diagram of a voltage output unit of a liquid crystal display according to another exemplary embodiment of the present invention.

Referring to FIG. 4, the liquid crystal display according to another exemplary embodiment of the present invention further includes a voltage output unit 610.

The voltage output unit 610 is a circuit that controls the output of the driving voltage VDD of the data driver 500 according to the output of the gray reference voltage AVDD, and may minimize the time difference between the two voltage outputs.

The input terminal IN of the voltage output unit 610 is connected to one pin of the GPIO of the signal controller 600, and the output terminal OUT is connected to the input terminal of the data driver 500. Transistors Q1 and Q2.

The first transistor Q1 includes a control terminal connected to the input terminal IN, an input terminal connected to the turn-on voltage V _H , and an output terminal connected to the control terminal of the second transistor Q2. .

The second transistor Q2 includes a control terminal connected to the output terminal of the first transistor Q1, an input terminal connected to the first voltage Vin, and an output terminal connected to the output terminal OUT. .

In this case, the first voltage Vin may be a voltage that is the basis of the driving voltage VDD of the data driver 500 and may be at the same level as the driving voltage VDD. When the first voltage Vin is at a voltage level different from the driving voltage VDD, the resistor V further includes a predetermined resistor R between the first voltage Vin and the input terminal of the second transistor Q2. The driving voltage VDD is set to be output to the output terminal OUT by voltage division according to the turn-on resistance of R and the second transistor Q2.

When the first voltage Vin of the high voltage is output according to the signal waveform of FIG. 3 and the gray level reference voltage AVDD maintains a low voltage level, the signal controller 600 inputs a voltage for turning off the first transistor Q2. Output as (IN).

Therefore, since the first transistor Q1 maintains the turn-off state, the turn-on voltage V _H is not output to the second transistor Q2, and thus the driving voltage VDD is not output to the output terminal OUT.

Next, when the gray reference voltage AVDD transitions to a high voltage, the gray reference voltage AVDD of the high voltage is output to the gray voltage generator 800 and the signal controller 600 turns on the first transistor Q1. Output voltage to input terminal (IN). Accordingly, the turn-on voltage V _H is applied to the second transistor Q2 through the turned-on first transistor Q1 to turn on the second transistor Q2. Accordingly, the driving voltage VDD is output to the data driver 500 through the turned-on second transistor Q2 and the output terminal OUT, and the data driver 500 starts to operate.

As described above, according to the present invention, it is possible to prevent the falling down by matching the voltage input time of the data driver and the gray voltage generator and outputting a constant data voltage during the time difference between the two voltage inputs.

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 (9)

A plurality of pixels, A gate driver supplying a gate signal to the pixel; A gray voltage generator for generating a plurality of gray voltages by dividing the reference voltage; A data driver which selects one of the plurality of gray voltages according to an image signal and supplies the pixel signal as a data signal; and A signal controller which generates a driving voltage of the reference voltage and the data driver and supplies the gray voltage generator and the data driver to each other in synchronization with the reference voltage and the driving voltage; Display device comprising a. In claim 1, The signal controller A voltage output unit configured to output the driving voltage to the data driver according to the reference voltage Containing Display device. In claim 2, The voltage output unit A first transistor comprising a control terminal connected to the reference voltage, a first terminal connected to a first voltage, and a second terminal, and A second transistor including a control terminal connected to a second terminal of the first transistor, a first terminal connected to the second voltage, and a second terminal connected to the data driver Containing Display device. In claim 3, And the first voltage is a turn on voltage level of the second transistor. In claim 4, And the second voltage is a driving voltage of the data driver. In claim 4, The voltage output unit further includes a resistor between the second voltage and the second transistor. In claim 6, The resistance is determined by the magnitude of the second voltage and a driving voltage of the data driver. A plurality of pixels, A gate driver supplying a gate signal to the pixel; A gray voltage generator for generating a plurality of gray voltages by dividing the reference voltage; and A data driver which operates according to a driving voltage, selects one of the plurality of gray voltages according to an image signal, and supplies the same to the pixel as a data signal. Including; The data driver supplies a predetermined voltage to the pixel as the data signal until the reference voltage is supplied to the gray voltage generator. Display device. In claim 8, And the data driver supplies a voltage corresponding to black to the pixel until the reference voltage is supplied to the gray voltage generator.

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