KR20060124952A - Liquid crystal display and method for different driving the same - Google Patents

Abstract

A liquid crystal display and a differential driving method thereof are provided to restrict lowering of dynamic contrast ratio caused due to the slow response speed of liquid crystals, and to prevent the abnormality of images due to over driving voltage. A liquid crystal display includes a frame memory(151) successively receiving a timing control signal and pixel data and storing reference frame pixel data output by dividing the pixel data by a unit of frame and previous frame pixel data supplied before a unit frame; a first lookup table(152) setting over driving data corresponding to the comparison result of the reference frame pixel data and the previous frame pixel data; a second lookup table(153) setting inverted driving data corresponding to the difference between the reference frame pixel data and the previous frame pixel data; a gamma voltage correcting unit(154) comparing the reference frame pixel data and the previous frame pixel data, compensating the reference frame pixel data by extracting the over driving data corresponding to the comparison result through the first lookup table, and extracting the inverted driving data for the difference between the reference frame pixel data and the previous frame pixel data through the second lookup table; a gamma voltage converting unit(155) converting the compensated reference frame pixel data and the extracted inverted driving data into reference gamma voltage and time delay gamma voltage according to the transmissivity-voltage characteristic of a liquid crystal panel, and outputting the reference gamma voltage; and a time delay unit(156) outputting the time delay voltage after delaying a predetermined time from the output of the reference gamma voltage.

Description

Liquid crystal display and its differential driving method {Liquid crystal display and method for different driving the same}

1 is a signal waveform diagram of a gamma voltage overdriven by a liquid crystal display according to the related art.

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

3 is a detailed block diagram illustrating an over-driving control unit according to an embodiment of the present invention.

4 is a signal waveform diagram of a gamma voltage overdriven by a liquid crystal display according to an exemplary embodiment of the present invention.

5 is a signal waveform diagram of a gamma voltage stabilized after being overdriven by a liquid crystal display according to an exemplary embodiment of the present invention.

6 is a flowchart illustrating a differential driving method of a liquid crystal display according to an exemplary embodiment of the present invention.

7 is a configuration diagram illustrating a liquid crystal display according to another exemplary embodiment of the present invention.

(Explanation of symbols for the main parts of the drawing)

100 and 200: liquid crystal display panels 110 and 210: gate drivers

120, 220: source driver 130, 230: timing controller

140 and 240: gamma voltage generator 150: overdrive controller

151: frame memory 152: first lookup table

153: second lookup table 154: gamma voltage correction unit

155: gamma voltage converter 156: time delay unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a differential driving method thereof, and more particularly, to a liquid crystal display device and a differential driving method thereof that are differentially overdriven.

In the liquid crystal display, a liquid crystal material having an anisotropic dielectric constant is injected between an upper transparent insulating substrate on which a common electrode, a color filter, a black matrix, and the like are formed, and a lower transparent insulating substrate on which a switching element and a pixel electrode are formed. By applying different potentials to the electrodes and the common electrode, the intensity of the electric field formed in the liquid crystal material is adjusted to change the molecular arrangement of the liquid crystal material, thereby controlling the amount of light transmitted through the transparent insulating substrate to express a desired image. It is a display device. In the liquid crystal display, a thin film transistor liquid crystal display (TFT LCD) using a thin film transistor (TFT) element as a switching element is mainly used.

Looking at the equivalent circuit of each pixel constituting the liquid crystal display device, a gate line and a data line are formed to cross each other, a thin film transistor and a pixel electrode are arranged at the intersection, and a liquid crystal capacitance (liquid crystal layer) and a storage capacitor are formed. .

The equivalent circuit of each pixel comprised in this way operates as follows.

First, when a gate signal is applied to a gate line and the thin film transistor is turned on, a gamma voltage set according to pixel data from a data line is applied to each pixel for each unit frame. The pixel data is a digital signal representing a gray level, and is generally set to have a value between 0 and 255.

Then, an electric field generated by the difference between the gamma voltage and the common voltage applied to each pixel is applied to the liquid crystal layer to transmit light with a transmittance corresponding to the intensity of the applied electric field. At this time, the storage capacitor maintains the gamma voltage applied to the pixel for a unit frame to display an image of the unit frame.

On the other hand, when the difference between the pixel data of the reference frame and the pixel data of the previous frame is so large that the gamma voltage applied to the liquid crystal layer is rapidly changed, it is difficult to stabilize the voltage level within the unit frame due to the slow response time of the liquid crystal. It is difficult to introduce a method of improving the response speed of the liquid crystal by over driving the pixel data for setting the gamma voltage to a higher value than the normal value.

1 is a signal waveform diagram of a gamma voltage overdriven by a liquid crystal display according to the related art.

If the overdrive is not applied when the liquid crystal display is driven, the response time of the liquid crystal corresponding to the change of the gamma voltage becomes an appropriate level, and the voltage may be stabilized according to the pixel data corresponding to the unit frame.

However, when over-driving is applied in the liquid crystal display, due to the charging characteristic of the liquid crystal, the over driving data (Over voltage) is maintained for over a predetermined time as shown in FIG. (Approximately 16.7 ms) may occur, and in a state where the liquid crystal is not stabilized, a voltage value corresponding to the next frame may be applied as a gamma voltage so that the output of the target pixel data may vary.

When the liquid crystal display is driven by the over-drive as described above, the liquid crystal unstable due to the over-drive affects the image of the next frame, causing inter-frame interference, thereby delaying the voltage settling time, or slow response of the liquid crystal. Due to speed, there was a problem such as a decrease in dynamic contrast ratio.

Therefore, the technical problem to be achieved by the present invention is to shorten the response time of the liquid crystal to prevent the decrease of the dynamic contrast ratio due to the slow response speed of the liquid crystal, and the abnormal image quality due to excessive over driving voltage (Over driving voltage) To prevent and to reduce the voltage settling time delayed due to over shoot (LCD) to provide a liquid crystal display device.

Another object of the present invention is to provide an efficient differential driving method of the liquid crystal display device described above.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

In accordance with one or more embodiments of the present invention, a liquid crystal display according to an embodiment of the present invention provides a timing control signal and pixel data, and accordingly, reference frame pixel data obtained by dividing the pixel data into frame units. A frame memory in which previous frame pixel data supplied before a unit frame is stored, a first lookup table in which overdrive data is set according to a comparison result of the reference frame pixel data and the previous frame pixel data, and the reference frame pixel data Comparing the second lookup table with the inversion driving data for the difference of the frame pixel data, the reference frame pixel data and the previous frame pixel data, and extracting the overdrive data according to the comparison result through the first lookup table. The reference frame pixel data A gamma voltage corrector configured to compensate for the difference between the reference frame pixel data and the previous frame pixel data through the second lookup table, and the compensated reference frame pixel data and the extracted inversion drive. A gamma voltage converter for converting data into a reference gamma voltage and a time delay gamma voltage according to the transmittance-voltage characteristics of the liquid crystal display panel, and outputting the reference gamma voltage, and a predetermined delay time from the point at which the reference gamma voltage is output. In addition, it characterized in that it comprises a time delay unit for outputting the time delay gamma voltage.

In the liquid crystal display according to the exemplary embodiment of the present invention, the predetermined delay time is preferably a response time of the liquid crystal material filled in the liquid crystal display panel, and more preferably 16.7 ms or less.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display according to an embodiment of the present invention, in which a timing control signal is supplied, pixel data is sequentially supplied, and the pixel data is divided in units of frames. Storing reference frame pixel data and previous frame pixel data supplied before the unit frame, comparing the reference frame pixel data with the previous frame pixel data, and extracting overdrive data according to a comparison result through a first lookup table Compensating the reference frame pixel data, converting the compensated reference frame pixel data into a reference gamma voltage according to a transmittance-voltage characteristic of a liquid crystal display panel, and converting the converted reference gamma voltage to the liquid crystal display panel. And applying the reference through the second lookup table. Extracting inversion driving data for a difference between frame pixel data and previous frame pixel data, converting the extracted inversion driving data into a time delay gamma voltage according to a transmittance-voltage characteristic of the liquid crystal display panel; And applying a time delay gamma voltage to the liquid crystal display panel with a predetermined delay time from when the reference gamma voltage is applied.

In the differential driving method of the liquid crystal display according to the exemplary embodiment of the present invention, it is preferable that the reference gamma voltage and the time delay gamma voltage are sequentially applied during the unit frame.

In the differential driving method of the liquid crystal display according to the exemplary embodiment of the present invention, the predetermined delay time is preferably a response time of the liquid crystal material filled in the liquid crystal display panel, and more preferably 16.7 ms or less.

Specific details of other embodiments are included in the detailed description and the drawings. Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. Like reference numerals refer to like elements throughout.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 2 to 7.

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

2, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 100, a gate driver 110, a source driver 120, a timing controller 130, and a gamma voltage generator 140. And an over-driving control unit 150.

In the liquid crystal display panel 100, a plurality of gate lines and data lines are intersected and thin film transistors and pixel electrodes are disposed at each intersection, and the scan signal supplied through the gate lines and the analog pixel signal supplied through the data lines are provided. Accordingly, an image is displayed.

The gate driver 110 sequentially supplies scan signals to the gate lines of the liquid crystal display panel 100.

The source driver 120 converts the pixel data input from the timing controller 130 into a gamma voltage, which is an analog signal, and supplies the same to the data lines of the liquid crystal display panel 100. In this case, the pixel data is generally a digital signal having a value between 0 and 255, and the source driver 120 converts the pixel data using a plurality of levels of gamma voltages supplied from the gamma voltage generator 140.

The timing controller 130 supplies timing control signals to the gate driver 110 and the source driver 120 to control the liquid crystal display panel 100, and supplies pixel data to the source driver 120 together with the timing control signal. Supply.

The gamma voltage generator 140 generates gamma voltages having a plurality of levels suitable for the transmittance-voltage characteristic of the liquid crystal display panel 100 by a resistor group in which a plurality of resistors are arranged in series. The gamma voltage is implemented to have an accurate and constant value so that the liquid crystal display panel 100 can display an image while maintaining a stable display quality.

The over driving controller 150 compensates the reference frame pixel data applied during the actual unit frame in consideration of over driving, and transmits the compensated reference frame pixel data to the source driver 120 so that the reference gamma voltage is liquid crystal. The display driver 100 is controlled to be applied to the display panel 100, and the source driver 120 is controlled to apply the time delay gamma voltage to the liquid crystal display panel 100 after a predetermined delay time passes from the time when the reference gamma voltage is applied.

The over-drive controller 150 applies gamma voltage values for the pixel data sequentially differently within the unit frame, thereby preventing inter-frame interference due to excessive over-driving, thereby reducing image quality abnormalities and liquid crystal characteristics in subsequent frames. To stabilize.

3 is a detailed block diagram illustrating an over-driving control unit according to an embodiment of the present invention.

Referring to FIG. 3, the overdrive controller 150 may include a frame memory 151, a first look-up table 152, a second look-up table 153, a gamma voltage corrector 154, and a gamma. A voltage converter 155, a time delay unit 156, and the like.

The frame memory 151 sequentially receives and stores pixel data along with a timing control signal. Here, since the pixel data is divided and stored in units of frames, the frame memory 151 stores reference frame pixel data and previous frame pixel data that are continuous in time. The previous frame pixel data is pixel data supplied one frame (unit frame) before the reference frame.

The first lookup table 152 sets overdrive data according to a comparison result of the reference frame pixel data and the previous frame pixel data.

The second lookup table 153 sets inversion driving data for the difference between the reference frame pixel data and the previous frame pixel data.

The gamma voltage corrector 154 compares the reference frame pixel data with the previous frame pixel data supplied one frame before, extracts the overdrive data according to the comparison result through the first lookup table 152, and stores the reference frame pixel data. To compensate. The inversion driving data for the difference between the reference frame pixel data and the previous frame pixel data is extracted through the second lookup table 153. Here, the first lookup table 152 and the second lookup table 153 use a nonvolatile memory such as an SRAM.

The gamma voltage converter 155 transmits the reference frame pixel data and the inverted driving data, which are compensated by transmitting / receiving data with the gamma voltage generator 140, to the reference gamma voltage according to the transmittance-voltage characteristics of the liquid crystal display panel 100. The gamma voltage is converted into a time delay gamma voltage, and a reference gamma voltage is output to be applied to the liquid crystal display panel 100.

The time delay unit 156 may have a predetermined delay time from the time point at which the reference gamma voltage is output, and output the time delay gamma voltage to be applied to the liquid crystal display panel 100. Here, the predetermined delay time is preferably the response time of the liquid crystal material filled in the liquid crystal display panel, and more preferably 16.7 ms or less.

4 is a signal waveform diagram of a gamma voltage overdriven by a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 5 is a gamma stabilized after overdriven by a liquid crystal display according to an exemplary embodiment of the present invention. Signal waveform diagram of voltage.

In the related art, the reference gamma voltage driving 1 applied to the reference frame pixel data is applied as shown in FIG. 4 so that the reference gamma voltage driving 1 cannot be stabilized during one frame due to the over driving. Interference between frames occurred due to the effect on the frame, and image quality abnormality occurred.

In an exemplary embodiment of the present invention, as shown in FIG. 4, the differential driving method of sequentially applying the reference gamma voltage Driving 1 and the time delay gamma voltage Driving 2 to which the over driving is applied has a predetermined delay time Td. As a result, as shown in FIG. 5, the differential driving voltage stabilized within one frame is applied to the liquid crystal display panel 100 to stabilize the voltage during the unit frame.

Referring to FIG. 4, in one embodiment of the present invention, a driving voltage for driving the liquid crystal display is sequentially applied twice. First, the reference gamma voltage Driving 1 is applied to one frame, and then the time delay gamma voltage Driving 2 is applied with a predetermined delay time Td. Here, the delay time Td is a time interval in which voltage is sequentially applied in a unit frame, and the time when the reference gamma voltage Driving 1 is applied to the liquid crystal display panel 100 and the time delay gamma voltage Driving 2 are determined. It is the difference of the time applied to the liquid crystal display panel 100, and becomes the response time of a liquid crystal.

The reference gamma voltage driving 1 is an over-drive voltage value generated by over-drive data when the pixel data difference between frames is relatively large, and the corresponding pixel data is obtained through a separate first lookup table 152 configured for over-drive. Overdrive data for is extracted and applied.

Since the time delay gamma voltage driving 2 is relatively large in pixel data difference between frames, the reference gamma voltage driving 1 is overdriven and then applied after a predetermined delay time Td to stabilize the overdrive voltage value. It is generated by the inversion driving data extracted from the second lookup table 153 to the voltage value.

By stabilizing the liquid crystal during over-driving in this manner, it is possible to prevent the liquid crystal destabilized by the over-driving affects the image of the next frame, thereby causing inter-frame interference, or an abnormality in image quality due to inter-frame interference. .

6 is a flowchart illustrating a differential driving method of a liquid crystal display according to an exemplary embodiment of the present invention.

First, in step S100, the timing control signal is supplied, and the pixel data is sequentially supplied.

Next, in step S110, reference frame pixel data obtained by dividing the pixel data into frame units and previous frame pixel data supplied before the unit frame are stored.

Next, in step S120, the reference frame pixel data is compared with the previous frame pixel data, and the overdrive data according to the comparison result is extracted through the first lookup table 152 to compensate the reference frame pixel data.

Next, in operation S130, the compensated reference frame pixel data is converted into a reference gamma voltage according to the transmittance-voltage characteristic of the liquid crystal display panel 100.

Next, in operation S140, the converted reference gamma voltage is applied to the liquid crystal display panel 100.

Next, in operation S150, the inversion driving data regarding the difference between the reference frame pixel data and the previous frame pixel data is extracted through the second lookup table 153.

Next, in operation S160, the extracted inversion driving data is converted into a time delay gamma voltage according to the transmittance-voltage characteristic of the liquid crystal display panel 100.

Next, in operation S170, a predetermined delay time is applied from the time point at which the reference gamma voltage is applied, and the converted time delay gamma voltage is applied to the liquid crystal display panel 100.

Here, the reference gamma voltage and the time delay gamma voltage are preferably applied sequentially during the unit frame. The predetermined delay time is preferably a response time of the liquid crystal material filled in the liquid crystal display panel 100, and more preferably 16.7 ms or less.

An example of such a process is that the previous frame pixel data is '10', the reference frame pixel data is '95', and the overdrive data for the pixel data difference '85' on the first lookup table 152 is '10'. The case where the inversion driving data for the pixel data difference '85' is set to '-10' on the second lookup table 153 will be described below.

First, in step S100, the timing control signal is supplied, and the pixel data is sequentially supplied.

Next, in step S110, the previous frame pixel data '10' and the reference frame pixel data '95', which are divided into pixel units, are stored.

Next, in operation S120, the pixel data difference '85' is recognized for two consecutive frames by comparing the previous frame pixel data '10' and the reference frame pixel data '95' and through the first lookup table 152. The overdrive data '10' for the previous frame pixel data '10' and the reference frame pixel data '95' is extracted to compensate the reference frame pixel data with '105'.

Next, in steps S130 and S140, the compensated reference frame pixel data '105' is converted into a reference gamma voltage according to the transmittance-voltage characteristic of the liquid crystal display panel 100 and applied to the liquid crystal display panel 100.

Next, in operation S150, the inversion driving data '-10' for the difference '85' between the reference frame pixel data and the previous frame pixel data is extracted through the second lookup table 153.

Next, in steps S160 and S170, the extracted inversion driving data '-10' is converted into a time delay gamma voltage according to the transmittance-voltage characteristic of the liquid crystal display panel 100, and after the predetermined delay time, 100).

7 is a configuration diagram illustrating a liquid crystal display according to another exemplary embodiment of the present invention.

Referring to FIG. 7, a liquid crystal display according to another exemplary embodiment of the present invention may include a liquid crystal display panel 200, a gate driver 210, a source driver 220, a timing controller 230, and a gamma voltage generator 240. It is configured to include.

In another embodiment of the present invention, the timing controller 230 simultaneously performs the function of the timing controller 130 and the function of the overdrive controller 150 included in one embodiment to compensate for the reference frame pixel data, and compensates. The reference frame pixel data is transmitted to the source driver 220 to control the source driver 120 to apply the reference gamma voltage and the time delay gamma voltage to the liquid crystal display panel 200 with a predetermined delay time.

In addition, since the liquid crystal display panel 200, the gate driver 210, the source driver 220, the timing controller 230, and the gamma voltage generator 240 perform a function as described in FIG. Detailed description thereof will be omitted.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, since the embodiments described above are provided to fully inform the scope of the invention to those skilled in the art, it should be understood that they are exemplary in all respects and not limited. The invention is only defined by the scope of the claims.

The liquid crystal display according to the exemplary embodiment and the other exemplary embodiment of the present invention configured as described above shortens the response time of the liquid crystal to prevent a decrease in the dynamic contrast ratio due to the slow response speed of the liquid crystal, and excessive over It is possible to prevent abnormalities in image quality due to over driving voltage and to reduce voltage settling time delayed due to over shoot.

In addition, the differential driving method of the liquid crystal display according to the exemplary embodiment and the other embodiment of the present invention can efficiently drive the above-described liquid crystal display.

Claims (7)

A frame memory configured to store reference frame pixel data obtained by dividing the pixel data in units of frames and previous frame pixel data supplied before a unit frame as timing control signals and pixel data are sequentially supplied; A first lookup table in which over driving data is set according to a result of comparing the reference frame pixel data with previous frame pixel data; A second lookup table in which inversion driving data is set for a difference between the reference frame pixel data and previous frame pixel data; Comparing the reference frame pixel data with previous frame pixel data, extracting the overdrive data according to a comparison result through the first lookup table to compensate the reference frame pixel data, and performing the reference through the second lookup table. A gamma voltage corrector extracting the inversion driving data with respect to a difference between frame pixel data and previous frame pixel data; A gamma voltage converter configured to convert the compensated reference frame pixel data and the extracted inversion driving data into a reference gamma voltage and a time delay gamma voltage according to transmittance-voltage characteristics of a liquid crystal display panel, and output the reference gamma voltage; And And a time delay unit configured to output the time delay gamma voltage at a predetermined delay time from when the reference gamma voltage is output. The method of claim 1, The predetermined delay time is, And a response time of the liquid crystal material filled in the liquid crystal display panel. The method of claim 2, The predetermined delay time is, It is 16.7 ms or less, The liquid crystal display device characterized by the above-mentioned. Supplying a timing control signal and sequentially supplying pixel data; Storing reference frame pixel data obtained by dividing the pixel data into frame units and previous frame pixel data supplied before a unit frame; Compensating the reference frame pixel data by comparing the reference frame pixel data with previous frame pixel data, extracting overdrive data according to a comparison result through a first lookup table; Converting the compensated reference frame pixel data into a reference gamma voltage according to a transmittance-voltage characteristic of a liquid crystal display panel; Applying the converted reference gamma voltage to the liquid crystal display panel; Extracting inversion driving data for a difference between the reference frame pixel data and previous frame pixel data through a second lookup table; Converting the extracted inversion driving data into a time delay gamma voltage according to a transmittance-voltage characteristic of the liquid crystal display panel; And And applying the time delay gamma voltage to the liquid crystal display panel with a predetermined delay time from when the reference gamma voltage is applied. The method of claim 4, wherein The reference gamma voltage and the time delay gamma voltage are A differential driving method of a liquid crystal display, characterized in that sequentially applied during a unit frame. The method of claim 4, wherein The predetermined delay time is, And a response time of the liquid crystal material filled in the liquid crystal display panel. The method of claim 6, The predetermined delay time is, A differential driving method of a liquid crystal display device, characterized in that less than 16.7ms.

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