KR100611662B1 - Liquid Crystal Display Device and Method for Driving the same - Google Patents

Abstract

A liquid crystal display device and a driving method thereof for preventing the occurrence of a tearing effect are disclosed. The liquid crystal display has a frame memory for writing new red, green, and blue data or reading out already written red, green, and blue data according to an address designation, and the written red, green, and blue data. And a detector for outputting a control signal so that white light is emitted to the light source controller when the new red, green and blue data are written before being output.

Tearing effect, liquid crystal display

Description

Liquid crystal display device and method for driving the same             

1 is a block diagram illustrating 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.

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

4 is a block diagram illustrating an internal configuration of a timing controller according to an exemplary embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a driving method thereof for preventing occurrence of a tearing effect.

Recently, display devices are also required to be lighter and thinner in accordance with light weight and thickness of personal computers and televisions, and according to such demands, flat panels such as liquid crystal displays (LCDs) instead of cathode ray tubes (CRTs) are required. Display is being developed.

The liquid crystal display device applies an electric field to a liquid crystal material having an anisotropic dielectric constant injected between two substrates, and adjusts the intensity of the electric field to control the amount of light transmitted from the external light source (backlight) to the substrate. It is a display device which obtains a desired image signal.

Such a liquid crystal display is representative of a portable flat panel display, and among these, a TFT-LCD using a thin film transistor (TFT) as a switching element is mainly used.

In general, the liquid crystal display may be classified into two methods, a color filter method and a field sequential driving method, according to a method of displaying a color image.

A color filter type liquid crystal display device forms a color filter layer consisting of three primary colors of red (R), green (G), and blue (B) on one of two substrates, and adjusts the amount of light transmitted through the color filter layer. By doing so, a desired image is displayed. The color filter type LCD synthesizes R, G, and B colors by adjusting the amount of light transmitted through the R, G, and B color filter layers in transmitting light emitted from a single light source to the R, G, and B color filter layers. By doing so, a desired image is displayed.

As described above, in a liquid crystal display device that displays an image using a single light source and a three-color color filter layer, a corresponding unit pixel is required for each of the R, G, and B regions, so that three times as many pixels are used as for displaying black and white. It is necessary. Therefore, in order to obtain a high resolution image, sophisticated manufacturing technology of a liquid crystal display panel is required. In addition, such a liquid crystal display device has manufacturing difficulties in that a separate color filter layer is formed on a substrate, and the luminance is lowered because the light transmittance of the color filter itself is low.

The liquid crystal display of the field sequential driving method turns on an independent light source of each of the R, G, and B colors periodically, and applies a color signal corresponding to each pixel in synchronization with the lighting cycle to produce a full color image. Get That is, according to the liquid crystal display of the field sequential driving method, R, G, and B primary colors output from R, G, and B backlights are output to one pixel without dividing one pixel into R, G, and B unit pixels. By displaying the light sequentially in time division, an image is displayed using the afterimage effect of the eye.

Such a field sequential driving method may be classified into an analog driving method and a digital driving method.

The analog driving method sets a plurality of gray voltages corresponding to the number of gray scales to be displayed, selects one gray voltage corresponding to gray data among the gray voltages, and drives the liquid crystal panel with the selected gray voltage to thereby apply the applied gray voltage. The gradation is indicated by the corresponding transmission amount.

On the other hand, in the digital driving method, the driving voltage applied to the liquid crystal is made constant, and the voltage application time is controlled to display the gray scale. According to such a digital driving method, gray scales are displayed by adjusting a cumulative amount of light transmitted through a liquid crystal by maintaining a constant driving voltage and controlling a voltage application state and a voltage non-application state in a timing manner.

In such a liquid crystal display device, when a frame frequency displayed on an image and a frequency of input data are inconsistent with each other, a tearing effect in which two or more types of data (ie, two or more frames of data) are displayed on one screen. Phenomena occur. Due to such a tearing effect, two or more frames of data are divided and displayed on one screen in a color filter type liquid crystal display, and in a field sequential type liquid crystal display, specific R, G, and B colors are used as data of the next frame. It is updated to show a different color, so that a phenomenon such as point noise is observed.

In order to solve this problem, a color filter type liquid crystal display uses a method of changing the frame frequency displayed on the screen at the same speed as the frequency of the input data. However, when the frequency change method is applied to the liquid crystal display of the field sequential method, a problem occurs because it affects the gray scale. In the field sequential liquid crystal display, since a frame is driven by dividing one frame into an R field, a G field, and a B field, a frequency three times faster than that of the color filter method is required. This is because there is a problem with the expression.

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve the above-described problems of the prior art, and a liquid crystal display and a driving method thereof for preventing a tearing effect in which data of a next frame is updated while displaying data of a current frame. It is to provide.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating 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 the exemplary embodiment of the present invention.

Referring to FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 100, a scan driver 200, a data driver 300, a gray voltage generator 400, a timing controller 500, Light emitting diodes 600a, 600b, 600c, and 600d that output R, G, and BW light;

The liquid crystal display panel 100 includes a plurality of display signal lines S1 -Sn and D1 -Dm and a plurality of pixel circuits 110 arranged in rows and columns when viewed as an equivalent circuit.

The display signal lines S1 -Sn and D1 -Dm include a plurality of scan lines S1 -Sn for transmitting a gate signal (also referred to as a "scan signal") and data lines D1 -Dm for transmitting a data signal. The scan lines S1-Sn extend substantially in the row direction and are substantially parallel to each other, and the data lines D1-Dm extend substantially in the column direction and are substantially parallel to each other.

Comprises: (Cst storage capacitor): each pixel circuit 110 includes display signal lines (S1-Sn, D1-Dm), a liquid crystal capacitor connected thereto, and a thin film transistor 10 connected to the (liquid crystal capacitor C _LC) and a storage capacitor .

The thin film transistor 10 is a three-terminal device, the gate terminal and the source terminal of which are respectively connected to the scan line S1-Sn and the data line D1-Dm, and the drain terminal of the thin film transistor 10 is a liquid crystal capacitor C _LC and a storage capacitor Cst. )

The liquid crystal capacitor C _LC has a pixel electrode (not shown) and a common electrode (not shown) as two electrodes, and the liquid crystal layer between the two electrodes functions as a dielectric. The pixel electrode is connected to the drain terminal of the thin film transistor 10, and the common electrode receives a common voltage Vcom.

The storage capacitor Cst is formed by overlapping a lower electrode (not shown) and a pixel electrode, and the lower electrode is connected to the common electrode so that the common voltage Vcom is applied in common.

Referring to FIG. 2, when the gate signal is applied to the scan line Sn and the thin film transistor 10 is turned on, the data voltage Vd supplied to the data line Dm is applied to the pixel electrode through the thin film transistor 10. do. Then, an electric field corresponding to the difference between the pixel voltage Vp and the common voltage Vcom applied to the pixel electrode is applied to the liquid crystal (equivalently represented by the liquid crystal capacitor in FIG. 2), and thus transmittance corresponding to the intensity of the electric field. To allow light to pass through. At this time, the pixel voltage Vp should be maintained for one frame or one field, and the storage capacitor Cst serves to hold the pixel voltage Vp applied to the pixel electrode for one frame or one field.

Referring back to FIG. 1, the scan driver 200 sequentially applies a scan signal to the scan lines S1 -Sn, thereby turning on the thin film transistor having a gate electrode connected to the scan line to which the scan signal is applied.

The gray voltage generator 400 generates a gray voltage having a size corresponding to the R, G, and B data and supplies the gray voltage to the data driver 300. The data driver 300 applies the gray voltage output by the gray voltage generator 400 to the corresponding data line.

The timing controller 500 inputs R, G, and B image signals R, G, and B data from an external graphic controller (not shown) and an input control signal for controlling the display thereof, for example, a vertical synchronization signal Vsync. ) And horizontal sync signal (Hysnc). The timing controller 500 appropriately processes the image signals R, G, and B data based on the input image signals R, G, and B data and the input control signal, according to the operating conditions of the liquid crystal display panel 100, and gates them. After generating the control signal Sg, the data control signal Sd, the light source control signal Sb, and the like, the gate control signal Sg is sent to the gate driver 200 and the data control signal Sd is transmitted to the data driver 300. ), The processed image signals R, G, and B DATA are sent to the gray voltage generator 400 and the light source control signal Sb is sent to the light source controller 700.

Here, the timing controller 500 according to the embodiment of the present invention includes a frame memory for storing or outputting the input image signals R, G, and B DATA in units of frames according to address assignment. In addition, an address of a video signal newly written to the frame memory (for example, N + 1 th R, G, and B DATA) and an image signal already stored in the frame memory (for example, N And a detector for detecting a tearing effect by comparing an address from which the first R, G, and B DATA) are read. Accordingly, the detector detects a tearing effect caused by the data of the N + 1th frame being updated in the frame memory while reading the data of the Nth frame from the frame memory, and at that moment, the detector detects a tearing effect. The control signal Sb is applied to the light source controller 700 so that light is emitted to prevent a tearing effect.

The light emitting diodes 600a, 600b, 600c, and 600d output light corresponding to R, G, B, and W to the liquid crystal display panel 100, and the light source controller 700 includes the light emitting diodes 600a, 600b, 600c, 600d) is controlled (ON / OFF). In this case, according to an exemplary embodiment of the present invention, when the gray level data is supplied from the data driver 300 to the data line Dm, and the light source controller 700 controls the R, G, B, W light emitting diodes 600a, 600b, The timing of turning on 600c and 600d may be synchronized by a control signal provided by the timing controller 500.

A display operation of the liquid crystal display according to the exemplary embodiment of the present invention will be described in detail with reference to FIG. 3.

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

Referring to FIG. 3, the liquid crystal display according to the exemplary embodiment of the present invention displays an image by dividing one frame into three fields, that is, an R field, a G field, and a B field. If the drive frequency of one frame is 60 Hz, each field performs display operation in synchronization with 180 Hz. Here, G1, G2, ... Gn represent a scanning signal applied to each scan line, and Cr, Cg, Cb represent a lighting signal for instructing the lighting of each of the R, G, and B light emitting diodes 600a, 600b, 600c. Indicates.

One frame of R, G, and B image data supplied from the outside are separated into one frame of R image data, G image data, and B image data by the timing controller 500 to match the display operation of the liquid crystal display device. Are converted and stored in frame memory (which may be contained within a timing controller). Each of the stored image data (R, G, B DATA) is outputted in R field period of 1/180 seconds in which one frame is divided into three according to the output signal from the timing controller 500. G image data is sequentially output to the G field, and B image data is sequentially output to the B field.

In the R field, the R image data voltage is sequentially written to all the pixels according to the scan signals G1, G2, ..., Gn, and then the light emitting diode 600a lights up in accordance with the lighting signal Cr in the illumination period. The R image is displayed on the liquid crystal display panel 100.

The G image data voltage is sequentially written to all the pixels according to the scan signals G1, G2, ..., Gn in the writing section of the G field, and then the light emitting diode 600b lights up in accordance with the lighting signal Cg in the lighting section. The G image is displayed on the liquid crystal display panel 100.

The B image data voltage is sequentially written to all the pixels according to the scan signals G1, G2, ..., Gn in the writing section of the B field, and then the light emitting diode 600c lights up in accordance with the lighting signal Cb in the lighting section. The B image is displayed on the liquid crystal display panel 100.

In this way, images corresponding to the color components of R, G, and B are sequentially displayed for each field of each color of the R, G, and B fields so that the image of the R, G, and B color components is a human visual afterimage phenomenon. Is synthesized and visually recognized as a color image of one frame.

However, in one frame, the R image data, the G image data, and the B image data of the Nth frame must be sequentially written, respectively, and the R image data of the Nth frame is written and the light emitting diode C When 600a) is turned on to display an R image on the liquid crystal display panel 100, and the image data of the N + 1th frame is written in the middle of G image data being written, that is, a tearing effect occurs. In the G lighting section, the white (W) light is emitted by the combination of the R, G, and B light emitting diodes 600a, 600b, and 600c without sending a lighting signal Cg (W) in FIG. 3. The diode 600d is turned on (section (a) in FIG. 3) so that the N + 1st image data which is incorrectly written in the liquid crystal display device 100 is not displayed. As described above, the liquid crystal display according to the exemplary embodiment of the present invention detects a time point at which a tearing effect occurs, and instantly whites a combination of the R, G, and B light emitting diodes 600a, 600b, and 600c. (W) The tearing effect can be eliminated by emitting light or turning on the W LED 600d.

In FIG. 3, each field is divided into a writing period and an illumination period to display an image. However, the present invention is not limited thereto, and a reset period for erasing the data voltage applied in the previous field may be separately included.

Hereinafter, detailed drawings for solving the tearing effect problem in the liquid crystal display as described above will be described with reference to FIGS. 4 and 5.

4 is a block diagram showing an internal configuration of a timing controller according to the first embodiment of the present invention. In FIG. 4, only a frame memory for detecting R, G, and B data and outputting the tearing effect and a detector for detecting a tearing effect are shown in the timing controller.

Referring to FIG. 4, a timing controller 500 according to an embodiment of the present invention includes a frame memory 510 and a detector 520.

In the frame memory 510, R, G, and B data of one frame are separately stored or output. That is, R, G, B data (for example, N-th frame R, G, B data) to be output from the external graphic controller (not shown) to the current frame (for example, N-th frame) is stored in each frame memory. Write to 510. At this time, the N-th frame R, G, B data is updated in the frame memory 510 by receiving a command of a write address. In addition, the N-th frame R, G, and B data stored in the frame memory 510 receive an output address command, respectively, and sequentially gray-scale the N-th frame R, G, and B data of the corresponding address. It is output to the voltage generator 400. The frame memory 510 is a dual port RAM capable of writing and reading.

The detector 520 may write addresses of the frames R, G, and B that are written to the frame memory 510, and frames R, G that are output to the gray voltage generator 400. B Compares the read addresses of the data. If it is determined that the output address is later than the write address, the detector 520 uses a combination of R, G, and B light emitting diodes 600a, 600b, and 600c. Outputs a control signal Sb for causing the light emitting diode 600d to light up or to the light source controller 700.

For example, the process of detecting the tearing effect of FIG. 4 will be described below.

For example, suppose that the address of the frame memory 510 is from 1 to 10, and write and output operations proceed sequentially in ascending order of addresses. In operation (read), the R, G, and B data of the Nth frame already stored are read from address 1, and the R, G, and B data of address 4 are read. At this time, if the R, G, B data of the N + 1th frame is written to address 5 in the write operation, the Nth frame of the 5th address already stored in the read operation is written. Instead of outputting the R, G, and B data, the R, G, and B data of the N + 1th frame of the newly written address 5 is read to display a completely different color. . That is, a tearing effect is generated. In this case, a read operation of the R, G, and B data of the Nth frame may be performed first, and a write operation of the R, G, and B data of the N + 1th frame may be performed. An operation and a write operation may occur at the same time.

At this time, the detector 520 compares the write address and the read address of the frame memory 510 to detect a case where the write address is faster than the read address. Outputs a control signal Sb to the light source controller 700 for emitting white (W) light or for turning on the W light emitting diode 600d by a combination of the R, G, and B light emitting diodes 600a, 600b, and 600c. do. That is, when new R, G, and B data are written before the R, G, and B data written in the frame memory 510 is output, the detector 520 outputs the control signal Sb. The detector 520 generates a white (W) light by combining the R, G, and B light emitting diodes 600a, 600b, and 600c, or outputs a control signal Sb for turning on the W light emitting diode 600d. The case occurs when [Equation 1] below.

Write address> read address

Here, the R, G, and B data written to the write address are the N + 1th frame data, and the R, G, and B data output to the read address are the Nth frame data.

Except in the case of Equation 1, the detector 520 outputs a control signal for emitting light of the corresponding light emitting diode to the light source controller 700.

According to the timing controller 500 of the liquid crystal display according to the exemplary embodiment of the present invention, the N + 1th frame data is stored in the frame memory while the image of the Nth frame is read and the image is displayed on the liquid crystal display panel. Detects a tearing effect that is written in and causes white (W) light to come out in a combination of R, G, and B light emitting diodes 600a, 600b, and 600c, or turns off the W light emitting diode 600d. The lighting can prevent the tearing effect problem.

In the above-described embodiment of the present invention, the timing controller 500 includes a frame memory 510 for storing R, G, and B data and a detector 520 for detecting a tearing effect. However, the present invention is not limited thereto and may be installed in the data driver 300 or separately.

The scope of the present invention is not limited to the above embodiments, but various modifications and improvements of those skilled in the art using the basic concept of the present invention as defined in the following claims are also within the scope of the present invention.

As described above, the liquid crystal display according to the exemplary embodiment of the present invention writes the R, G, and B data of the N + 1th frame to the frame memory before the R, G, and B data of the Nth frame is read. ) Tearing effect is detected and instantaneous white (W) light is emitted by the combination of R, G, and B light emitting diodes 600a, 600b, 600c, or the W light emitting diode 600d is turned on. Tearing effec t Prevents problems.

Claims (18)

A liquid crystal display panel including a plurality of scan lines for transmitting a scan signal, a plurality of data lines crossing the scan lines, and a plurality of pixel circuits arranged in an area where the scan lines and the data lines intersect; A light source controller configured to emit light of red, green, and blue light emitting diodes on the liquid crystal display panel; A scan driver for applying a scan signal to the plurality of scan lines; A data driver configured to output gray, green, and blue gray voltages to the plurality of data lines; A gray voltage generator which outputs gray voltages corresponding to red, green, and blue data to the data driver; And A timing controller configured to output red, green, and blue data to the gray voltage generator and to control operations of the data driver and the light source controller;  The timing controller may include a frame memory for writing new red, green, and blue data or reading the written red, green, and blue data according to an address designation. When the new red, green, and blue data is written before the written red, green, and blue data is output, the light source may emit white (W) light through the light emitting combination of the red, green, and blue light emitting diodes. And a detector for outputting a control signal to the controller. The method of claim 1, The detector, And comparing the write addresses of the new red, green, and blue data with the output addresses of the output red, green, and blue data, and outputting the control signal when the write address is faster than the output address. . The method of claim 1, And the red, green, and blue data output from the frame memory are N-th frame data, and the new red, green, and blue data written in the frame memory are N + 1th frame data. The method of claim 1, The frame memory, And a dual port RAM having an input port for writing the new red, green, and blue data and an output port for outputting the red, green, and blue data. The method of claim 4, wherein The detector, A first input terminal connected to the input port; A second input terminal connected to the output port; And And an output terminal connected to the light source controller. The method of claim 1, The pixel circuit, A switching transistor transferring red, green, and blue data voltages sequentially transmitted through the data line in response to a selection voltage of the scan line; And A liquid crystal capacitor configured to transmit light of the red, green, and blue light emitting diodes according to the red, green, and blue data voltages; And And a storage capacitor connected in parallel with the liquid crystal capacitor to maintain the red, green, and blue data voltages for one frame. A liquid crystal display panel; A light source controller configured to emit light of red, green, and blue light emitting diodes on the liquid crystal display panel; A gradation voltage generator for outputting gradation voltages corresponding to red, green, and blue data to the data driver; And a timing controller including a frame memory for outputting red, green and blue data to the gray voltage generator and a detector for controlling an operation of a light source controller. An output step of outputting the red, green, and blue data from the frame memory; A writing step of writing new red, green, and blue data into the frame memory; A comparison step of comparing, at the detector, a write address of a position at which the new red, green and blue data is to be written with an output address at a position at which the red, green and blue data is output; And And a control step of outputting a control signal to the light source controller so that the white light is emitted from the detector by the light emitting combination of the red, green, and blue light emitting diodes when the write address is earlier than the output address after the comparing step. Method of driving display device. The method of claim 7, wherein The red, green, and blue data output from the frame memory are Nth frame data, and the new red, green, and blue data written in the frame memory are N + 1th frame data. Driving method. The method of claim 7, wherein The writing step, And a driving method performed simultaneously with the output step. A liquid crystal display panel including a plurality of scan lines for transmitting a scan signal, a plurality of data lines crossing the scan lines, and a plurality of pixel circuits arranged in an area where the scan lines and the data lines intersect; A light source controller controlling red, green, blue, and white light emitting diodes to emit light on the liquid crystal display panel; A scan driver for applying a scan signal to the plurality of scan lines; A data driver configured to output gray, green, and blue gray voltages to the plurality of data lines; A gray voltage generator which outputs gray voltages corresponding to red, green, and blue data to the data driver; And A timing controller configured to output red, green, and blue data to the gray voltage generator and to control operations of the data driver and the light source controller;  The timing controller may include a frame memory for writing new red, green, and blue data or reading the written red, green, and blue data according to an address designation. And a detector for outputting a control signal to the light source controller to turn on the white light emitting diode when the new red, green and blue data is written before the written red, green and blue data is output. A liquid crystal display device. The method of claim 10, The detector, And comparing the write addresses of the new red, green and blue data with the output addresses of the output red, green and blue data, and outputting the control signal when the write address is faster than the output address. Device. The method of claim 10, And the red, green, and blue data output from the frame memory are N-th frame data, and the new red, green, and blue data written in the frame memory are N + 1th frame data. The method of claim 10, The frame memory, And a dual port RAM having an input port for writing the new red, green, and blue data and an output port for outputting the red, green, and blue data. The method of claim 13, The detector, A first input terminal connected to the input port; A second input terminal connected to the output port; And And an output terminal connected to the light source controller. The method of claim 1, The pixel circuit, A switching transistor transferring red, green, and blue data voltages sequentially transmitted through the data line in response to a selection voltage of the scan line; And A liquid crystal capacitor configured to transmit light of the red, green, blue, and white light emitting diodes according to the red, green, and blue data voltages; And And a storage capacitor connected in parallel with the liquid crystal capacitor to maintain the red, green, and blue data voltages for one frame. A liquid crystal display panel; A light source controller controlling red, green, blue, and white light emitting diodes to emit light on the liquid crystal display panel; A gradation voltage generator for outputting gradation voltages corresponding to red, green, and blue data to the data driver; And a timing controller including a frame memory for outputting red, green, and blue data to the gray voltage generator and a detector for controlling an operation of a light source controller. An output step of outputting the red, green, and blue data from the frame memory; A writing step of writing new red, green, and blue data into the frame memory; A comparison step of comparing, at the detector, a write address of a position at which the new red, green and blue data is to be written with an output address at a position at which the red, green and blue data is output; And And a control step of outputting a control signal to the light source controller to turn on the white light emitting diode in the detector when the write address is earlier than the output address after the comparing step. The method of claim 16, The red, green, and blue data output from the frame memory are Nth frame data, and the new red, green, and blue data written in the frame memory are N + 1th frame data. Driving method. The method of claim 16, The writing step, And a driving method performed simultaneously with the output step.

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