KR20110076647A - Liquid crystal display device and driving method the same - Google Patents

Abstract

PURPOSE: A liquid crystal display device and a driving method thereof are provided to improve display quality by compensating a gradation phenomenon. CONSTITUTION: A liquid crystal display panel(2) is formed in intersections between a plurality of gate lines and a plurality of data lines. A backlight irradiates light to a liquid crystal display panel. A backlight controller controls the driving of the backlight. A timing controller converts an image signal from the outside into a data signal and supplies the data signal to a data driving circuit unit. The timing controller generates a dimming signal for driving the backlight and supplies the dimming signal to the backlight controller.

Description

Liquid Crystal Display Device and Driving Method the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and in particular, to compensate for a gradation phenomenon of a display screen according to a frame inversion method, thereby improving display quality by improving luminance uniformity. And a driving method thereof.

Typically, the liquid crystal display displays an image by adjusting light transmittance for each liquid crystal cell according to a signal. To this end, the liquid crystal display includes a liquid crystal display panel in which liquid crystal cells are arranged in a matrix, and a driving circuit for driving the liquid crystal display panel.

Liquid crystal cells are defined in an area where a plurality of gate lines and a plurality of data lines cross each other in the liquid crystal display panel. Each liquid crystal cell is provided with pixel electrodes and common electrodes for applying an electric field, and each of the pixel electrodes is connected to a data line via a thin film transistor (TFT) which is a switching element.

The driving circuit includes a gate driver G-IC for driving the gate lines, a data driver D-IC for driving the data lines, and a common voltage generator for driving the common electrode.

The gate driver sequentially supplies a scanning signal, that is, a gate signal for turning on the TFT, to the gate lines to sequentially drive the liquid crystal cells on the liquid crystal display panel one by one.

Whenever a gate signal is supplied to each of the gate lines, the data driver supplies a pixel voltage signal, that is, an analog data signal, to each of the data lines. The common voltage generator supplies a common voltage signal to the common electrode.

Accordingly, the liquid crystal display displays an image by adjusting the transmittance of light supplied from the backlight unit by changing the liquid crystal arrangement state between the pixel electrode and the common electrode according to the pixel voltage signal for each liquid crystal cell.

In order to prevent deterioration of the liquid crystal display panel, the liquid crystal display having such a configuration uses an inversion scheme in which data voltages having opposite polarities are alternately applied to each pixel region.

Such an inversion method includes a frame inversion method, a line (column) inversion method, and a dot inversion method. In general, the frame inversion method is widely used. It is used.

1 is a plan view schematically showing a driving method of a frame inversion method according to the prior art.

As shown in FIG. 1, the frame inversion method applies data voltages having polarities (+, −) opposite to each other to liquid crystal cells on a liquid crystal display panel for each frame.

That is, in the first frame, positive data voltages are sequentially applied to the liquid crystal cells on all the liquid crystal display panels, and in the second frame, the negative polarities are sequentially applied to the liquid crystal cells on all the liquid crystal display panels. Apply the data voltage. When inverting from the first frame to the second frame, the negative voltage is charged while the liquid crystal cell is already charged with the positive voltage.

According to the driving method of the frame inversion method according to the related art, n + 1 is applied by a parasitic capacitor of the liquid crystal cell itself when a negative data voltage is applied to the n-th gate line. There is a problem in that the data voltage of positive polarity charged in the liquid crystal cells of the first gate line is partially discharged.

Since the positive data voltage of the liquid crystal cells of the n + 1 th gate line is partially discharged, when the negative data voltage is applied to the n + 1 th gate line, the n + 1 th gate line The liquid crystal cells of are charged with a negative voltage greater than that of the negative data voltage to be charged.

This phenomenon is n + 2, n + 3, ... As the last gate line becomes more severe, in reality, a gradation phenomenon occurs in which brightness of upper and lower portions of the liquid crystal display panel is different, resulting in a decrease in uniformity of luminance.

Such a gradation phenomenon appears more clearly from the upper end to the lower end of the liquid crystal display panel. Accordingly, there is a need for a liquid crystal display and a driving method capable of compensating for gradation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and by reducing or increasing a dimming signal supplied to a backlight controller from an upper end portion to a lower end portion of a liquid crystal display panel, a liquid crystal display device capable of compensating for a gradation phenomenon and a driving method thereof are provided. For the purpose of

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device and a driving method thereof capable of improving the uniformity of luminance of the liquid crystal display panel.

According to an exemplary embodiment of the present invention, a liquid crystal display includes: a liquid crystal display panel having a plurality of pixels formed in respective regions defined by intersections of a plurality of gate lines and a plurality of data lines; A backlight for irradiating light onto the liquid crystal display panel; A backlight controller which controls driving of the backlight; And a timing controller for converting an image signal from an outside into the data signal and supplying the data signal to a data driving circuit, and generating and dimming a signal for driving the backlight to the backlight controller. The dimming signal is decreased or increased from the upper end of the display panel to the lower end.

In the liquid crystal display according to the exemplary embodiment of the present disclosure, the dimming signal is a control signal having a duty ratio for controlling the driving time of the backlight.

In the liquid crystal display according to the exemplary embodiment of the present disclosure, the dimming signal is a control signal of an amplitude value of current for adjusting the brightness of the backlight.

According to an exemplary embodiment of the present invention, a liquid crystal display includes: a liquid crystal display panel having a plurality of pixels formed in respective regions defined by intersections of a plurality of gate lines and a plurality of data lines; A backlight for irradiating light onto the liquid crystal display panel; A backlight control unit controlling driving of the backlight; And a timing controller for converting an image signal from an outside into the data signal and supplying the data signal to a data driving circuit unit, and generating a dimming signal for driving the backlight and supplying the dimming signal to the backlight controller. The dimming signal is decreased or increased from the first time point to the last time point within the frame.

A driving method of a liquid crystal display device according to an exemplary embodiment of the present invention includes a liquid crystal display panel and a backlight for supplying light to the liquid crystal display panel, the method comprising: driving the display panel; Decreasing or increasing the dimming signal for driving the backlight from the first time point to the last time point in one frame; And driving the backlight using the reduced or increased dimming signal.

The driving method of the liquid crystal display according to the exemplary embodiment of the present invention is characterized in that the brightness of the backlight decreases or increases from the upper end to the lower end of the liquid crystal display panel.

The liquid crystal display and the driving method according to an exemplary embodiment of the present invention reduce or increase the dimming signal supplied to the backlight controller from the upper part to the lower part of the liquid crystal display panel to compensate for the screen gradation phenomenon in the frame inversion method. Can be.

The liquid crystal display and the driving method according to an exemplary embodiment of the present invention may improve display quality by improving luminance uniformity of the liquid crystal display panel.

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

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

Referring to FIG. 2, the liquid crystal display according to the first exemplary embodiment of the present invention may include a display panel 2, a gate driving circuit unit 4, a data driving circuit unit 6, a backlight 8, a backlight control unit 10, and the like. The timing controller 12 is comprised.

The liquid crystal display panel 2 includes n gate lines G1 to Gn and m data lines D1 to Dm, and the gate lines G1 to Gn intersect with the data lines D1 to Dm. It includes a liquid crystal cell (Clc) formed for each defined region.

The liquid crystal cell Clc includes a thin film transistor TFT and a storage capacitor Cst formed at an intersection of the gate lines G1 to Gn and the data lines D1 to Dm.

The thin film transistor TFT supplies an analog data signal supplied from the data lines D1 to Dm to the liquid crystal cell Clc in response to a scan signal supplied from the gate lines G1 to Gn.

The storage capacitor Cst is formed between the pixel electrode (not shown) of the liquid crystal cell Clc and the gate line of the front end, or is formed between the pixel electrode of the liquid crystal cell Clc and the common electrode line to form the liquid crystal cell Clc. Keep the voltage constant.

The gate driving circuit unit 4 sequentially supplies scan signals to the gate lines G1 to Gn in response to the gate control signal GCS from the timing controller 12.

The data driving circuit unit 6 converts the digital video data R, G, and B into analog gamma voltages (data signals) corresponding to the gray scale values in response to the data control signals DCS from the timing controller 12, This analog gamma voltage is supplied to the data lines D1 to Dm.

The backlight 8 is used to irradiate the display panel 2 with light. The backlight 8 includes a plurality of lines in the same direction as the gate lines G1 to Gn, and is formed under the liquid crystal display panel 2.

The backlight controller 10 receives the dimming signal DS from the timing controller 12 and controls the lighting of the backlight 8.

The timing controller 12 supplies the gate control signal GCS to the gate driving circuit section 4 using the vertical / horizontal synchronization signal and the clock signal, and supplies an image signal from the outside to the data driving circuit section 6. The converted digital video data R, G, and B and the data control signal DCS are supplied.

In addition, the timing controller 12 supplies the dimming signal DS and the backlight control signal GCS corresponding to the digital video data R, G, and B to the backlight controller 10.

In this case, the timing controller 12 reduces and supplies the dimming signal DS supplied to the backlight controller 10 from the upper end portion to the lower end portion of the display panel 2.

That is, the timing controller 12 is positioned below the lower end of the display panel 2 of the backlights 8 of the plurality of lines than the backlight located below the upper end of the display panel 2 of the backlights 8 of the plurality of lines. Supply a small dimming signal DS to the backlight.

The size of the dimming signal DS corresponds to a duty ratio for controlling the driving time of the backlight 8 through the backlight controller 10.

In the normally white liquid crystal panel, when the above-mentioned gradation phenomenon occurs when the frame inversion is driven, the luminance of the lower portion is greater than the luminance of the upper portion of the liquid crystal display panel 2.

Therefore, the dimming signal for driving the backlight corresponding to the lower end of the liquid crystal display panel 2 is reduced and input than the dimming signal supplied to the backlight corresponding to the upper end of the liquid crystal display panel 2. That is, the backlight corresponding to the lower end of the liquid crystal display panel is controlled to display the reduced luminance.

To this end, by inputting the dimming signal DS reduced in the backlight control unit 10, the duty ratio is reduced to reduce the driving time of the backlight 8. As a result, the backlight corresponding to the lower end of the liquid crystal display panel 2 may have a reduced luminance corresponding to the duty value according to the dimming signal.

On the other hand, in the normally black liquid crystal display panel, when the above-described gradation phenomenon occurs when the frame inversion is driven, the luminance of the lower end portion of the liquid crystal display panel 2 becomes smaller than the luminance of the upper end portion of the liquid crystal display panel 2.

Therefore, the dimming signal for driving the backlight located under the lower end of the liquid crystal display panel 2 is increased from the original dimming signal. That is, the backlight corresponding to the lower end of the liquid crystal display panel is controlled to display the increased luminance.

To this end, by inputting the increased dimming signal DS to the backlight controller 10, the duty ratio is increased to increase the driving time of the backlight 8. As a result, the backlight corresponding to the lower end of the liquid crystal display panel 2 may have increased luminance corresponding to the duty value according to the dimming signal.

3 is a view schematically illustrating a display panel and a backlight driving time according to the first embodiment of the present invention.

As shown in FIG. 3, in a normally white panel, a liquid crystal display panel 2 may be used rather than a dimming signal for driving a backlight corresponding to an upper end of the liquid crystal display panel 2 among the backlights 8 of the plurality of lines. ) By reducing and supplying a dimming signal for driving the backlight corresponding to the lower end, it is controlled to reduce the duty ratio of the backlight. When the duty value is decreased, the driving time of the backlight corresponding to the lower end of the liquid crystal display panel 2 is reduced, thereby reducing the luminance.

As described above, in the liquid crystal display according to the first exemplary embodiment of the present invention, the backlight controller 10 may be configured according to whether the liquid crystal display panel 2 is normally white or normally black. The duty ratio of the backlight may be controlled by decreasing or increasing the input dimming signal. Through this, the gradation phenomenon due to the frame inversion driving can be compensated. Due to the compensation of the gradation phenomenon, the luminance uniformity of the liquid crystal display may be improved.

In FIG. 3, a case of a normally white liquid crystal display panel is illustrated as an example, but this is an example. In the case of a normally black liquid crystal display panel, the backlight controller 10 increases the duty ratio for driving the backlight to correspond to the increased dimming signal DS, thereby increasing the duty ratio of the liquid crystal display panel 2. The driving time of the backlight corresponding to the lower end can be increased.

4 is a diagram schematically illustrating a display panel and a backlight driving current according to a second embodiment of the present invention. Hereinafter, the liquid crystal display and the driving method according to the second embodiment of the present invention will be described with reference to FIG. 4.

The liquid crystal display according to the second exemplary embodiment of the present invention has the same structure as the liquid crystal display according to the first exemplary embodiment shown in FIG. 2. However, driving of the dimming signal DS supplied from the timing controller 12 to the backlight controller 10 and the backlight 8 controlled by the backlight controller 10 are different.

As shown in FIG. 4, in the liquid crystal display according to the second exemplary embodiment, the driving current for driving the backlight 8 in the normally white liquid crystal display panel 2 is increased. The upper and lower portions of the liquid crystal display panel 2 are controlled to become smaller.

To this end, the timing controller 12 reduces the driving dimming signal for driving the backlight corresponding to the lower end of the liquid crystal display panel 2 from the upper end to the lower end thereof, and supplies it to the backlight controller 10.

Here, the dimming signal DS, which is reduced from the upper end to the lower end of the liquid crystal display panel 2, is supplied to correspond to the amplitude of the current for controlling the current of the backlight 8 through the backlight controller 10. The reduced dimming signal DS reduces the magnitude of the current to reduce the brightness of the backlight 8.

That is, the driving of the backlight located at the lower end of the liquid crystal display panel 2 is inputted by reducing the dimming signal from the original dimming signal, thereby reducing the magnitude of the current flowing in the backlight corresponding to the lower end of the liquid crystal display panel 2. .

Accordingly, the gradation phenomenon in which the lower end of the liquid crystal display panel 2 becomes brighter than the upper end in the frame inversion method may be compensated. Due to the compensation of the gradation phenomenon, the luminance uniformity of the liquid crystal display may be improved.

In the description with reference to FIG. 4, the case in which the normally white is a liquid crystal display panel is taken as an example. In contrast, in the case of the normally black liquid crystal display panel,

The dimming signal for driving the backlight corresponding to the lower end of the liquid crystal display panel 2 is increased by inputting the original dimming signal, thereby increasing the magnitude of the driving current supplied to the backlight to increase the brightness of the backlight. Through this, the gradation phenomenon can be compensated for.

In the above-described first and second embodiments of the present invention, the dimming signal is decreased or increased from the upper end to the lower end of the liquid crystal display panel. However, in the frame inversion method, since the dimming signal is supplied in units of frames, the timing controller 12 decreases or increases the dimming signal supplied to the backlight controller from the first time point to the last time point in one frame. It can be interpreted as.

Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. Therefore, it is to be understood that the embodiments described above are exemplary in all respects and not restrictive.

The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. do.

1 is a plan view schematically showing a driving method of a frame inversion method according to the prior art.

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

3 is a view schematically illustrating a display panel and a backlight driving time according to the first embodiment of the present invention.

4 is a diagram schematically illustrating a display panel and a backlight driving current according to a second embodiment of the present invention.

<Explanation of Signs of Major Parts of Drawings>

2: display panel 4: gate driving circuit part

6 data driving circuit 8 backlight

10: backlight control unit 12: timing controller

Claims (9)

A liquid crystal display panel having a plurality of pixels formed for each region defined by the intersection of the plurality of gate lines and the plurality of data lines; A backlight for irradiating light onto the liquid crystal display panel; A backlight controller which controls driving of the backlight; And And a timing controller for converting an image signal from an outside into the data signal and supplying the data signal to a data driving circuit unit, and generating a dimming signal for driving the backlight and supplying the dimming signal to the backlight controller. And the timing controller decreases or increases the dimming signal from the upper end to the lower end of the liquid crystal display panel. The method of claim 1, The backlight is And a plurality of lines formed in the gate line direction of the liquid crystal display panel and formed below the liquid crystal display panel. The method of claim 1, The dimming signal is And a duty ratio control signal for controlling the driving time of the backlight. The method of claim 1, The dimming signal is And a control signal having an amplitude value for controlling the brightness of the backlight. A liquid crystal display panel having a plurality of pixels formed for each region defined by the intersection of the plurality of gate lines and the plurality of data lines; A backlight for irradiating light onto the liquid crystal display panel; A backlight control unit controlling driving of the backlight; And A timing controller for converting an image signal from an outside into the data signal and supplying the data signal to a data driving circuit unit, and generating a dimming signal for driving the backlight and supplying the dimming signal to the backlight controller; And the timing controller decreases or increases the dimming signal from the first time point to the last time point in one frame. In the driving method of a liquid crystal display device comprising a liquid crystal display panel and a backlight for supplying light to the liquid crystal display panel, Driving the display panel; Decreasing or increasing the dimming signal for driving the backlight from the first time point to the last time point in one frame; And And driving the backlight using the reduced or increased dimming signal. The method of claim 6, The dimming signal is And a control signal having a duty ratio for controlling the driving time of the backlight. The method of claim 6, The dimming signal is And a control signal of an amplitude value of current for adjusting the brightness of the backlight. The method of claim 6, And a brightness of the backlight decreases or increases from an upper end portion of the liquid crystal display panel to a lower end portion thereof.

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