KR20080035333A - Liquid crystal display and method of driving the same - Google Patents

Abstract

An LCD device and a driving method thereof are provided to improve a display error by supplying optimal gate off voltages according to the operation conditions of a liquid crystal panel. An LCD(Liquid Crystal Display) device includes a liquid crystal panel(600), a driving voltage generator(200), a gate driver(300), and a driving voltage controller(500). The liquid crystal panel includes plural gate and data lines. The driving voltage generator generates gate on/off voltages. The gate driver sequentially supplies the gate on/off voltages to the gate lines. The driving voltage controller generates control signals by detecting the leakage current from the liquid crystal panel and controls the magnitude of the gate off voltage by feeding back the generated control signals to the driving voltage generator.

Description

Liquid crystal display and method of driving the same {Liquid crystal display and method of driving the same}

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

FIG. 2 is an equivalent circuit diagram of one pixel of the liquid crystal display of FIG. 1.

3 is a block diagram of the driving voltage controller of FIG. 1.

FIG. 4 is an example of the current-voltage characteristic curve of the liquid crystal panel showing the magnitude change of the gate-off voltage by the driving voltage controller of FIG. 3.

FIG. 5 is another example of the current-voltage characteristic curve of the liquid crystal panel showing the magnitude change of the gate-off voltage by the driving voltage controller of FIG. 3.

6 is a block diagram of a driving voltage controller according to another exemplary embodiment of FIG. 3.

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

100: timing controller 200: driving voltage generator

300: gate driver 400: data driver

450: gamma voltage generator 500: drive voltage controller

510: amplifier 520: signal generator

530: storage unit 540: comparison / operation unit

550: mixing / averaging unit 600: liquid crystal panel

The present invention relates to a liquid crystal display and a driving method thereof, and more particularly, to a liquid crystal display and a driving method thereof that can minimize leakage current.

In recent years, liquid crystal displays have been in the spotlight as display means.

A liquid crystal display device applies an electric field to a liquid crystal material having an anisotropic dielectric constant injected between two display panels, adjusts the intensity of the electric field, and controls the amount of light transmitted through the display panel to obtain a desired image signal. Device.

The liquid crystal display device may include a liquid crystal panel including a plurality of gate lines parallel to each other, a plurality of data lines insulated from and intersecting the gate lines, and a driving assembly supplying driving and control signals to the liquid crystal panel.

The liquid crystal panel may be driven by applying image data through a plurality of data lines while sequentially applying gate on / off voltages to the plurality of gate lines. In this case, the gate on / off voltage may be provided at a fixed value when the liquid crystal panel is driven.

However, the I-V (voltage-current) characteristic curve of the device of the liquid crystal panel, for example, the thin film transistor, is changed by the temperature of the liquid crystal panel, for example, when the liquid crystal panel is driven for a long time. Accordingly, when the gate-off voltage is provided to the liquid crystal panel, the thin film transistor may not be completely turned off, and a leakage current may occur. Such leakage current causes defects such as crosstalk, afterimage, flicker, and the like, resulting in deterioration of the quality of the liquid crystal display.

An object of the present invention is to provide a liquid crystal display device capable of minimizing leakage current.

Another object of the present invention is to provide a method of driving such a liquid crystal display.

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

According to an aspect of the present invention, there is provided a liquid crystal display device including: a liquid crystal panel including a plurality of gate lines and a plurality of data lines; a driving voltage generator configured to generate gate on / off voltages; A gate driver for sequentially providing gate on / off voltages to a plurality of gate lines, and generating a control signal by detecting a leakage current from the liquid crystal panel, and feeding back the generated control signal to the driving voltage generator to adjust the magnitude of the gate off voltage. And a driving voltage controller for adjusting.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display device, the method including: preparing a liquid crystal panel having a plurality of gate lines and a plurality of data lines; Sequentially providing the off voltage, detecting a leakage current from the liquid crystal panel, generating a control signal capable of adjusting the magnitude of the gate off voltage using the leakage current, and using the control signal to Adjusting the size.

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. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, and only the embodiments make the disclosure of the present invention complete, and the general knowledge in the art to which the present invention belongs. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

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

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel of the liquid crystal display of FIG. 1.

First, referring to FIG. 1, the liquid crystal display 700 largely includes a liquid crystal panel 600 and a driving device 100, 200, 300, 400, 450, and 500. The driving devices 100, 200, 300, 400, 450, and 500 may include the timing controller 100, the driving voltage generator 200, the gate driver 300, the data driver 400, and the gamma voltage generator 450. ) And the driving voltage controller 500.

The liquid crystal panel 600 may include a plurality of display signal lines G ₁ to G _N , D ₁ to D _M , and a plurality of unit pixels connected thereto and arranged in a matrix form in an equivalent circuit. Include.

The display signal lines G ₁ to G _N and D ₁ to D _M are provided with a plurality of gate lines G ₁ through G _N transmitting gate driving signals to the liquid crystal panel 600 and a plurality of data lines transferring data driving signals. (D ₁ ~ D _M ). Here, the gate lines G ₁ to G _N extend in the row direction of the liquid crystal panel 600 so that they are substantially parallel to each other, and the data lines D ₁ to D _M extend in the column direction of the liquid crystal panel 600 so that the gate line Intersect the lines G ₁ to G _N , and are substantially parallel to each other.

In addition, the liquid crystal panel 600 may include at least one dummy data line (not shown). The dummy data line may detect a leakage current Ioff generated from the liquid crystal panel 600. In more detail, the dummy data line may be positioned to be substantially parallel to the plurality of data lines D ₁ to D _M of the liquid crystal panel 600, and may be formed at least one. The dummy data line detects a leakage current Ioff generated by a gate driving signal provided to the liquid crystal panel 600 from the gate driver 300, which will be described later, for example, the gate off voltage Voff. 500).

Each unit pixel includes a switching element Q connected to the display signal lines G ₁ to G _N , D ₁ to D _M , a liquid crystal capacitor C _lc , and a storage capacitor Cst connected thereto. The sustain capacitor Cst may be omitted as necessary.

Referring to FIG. 2, the liquid crystal panel 600 includes a first display panel 610 and a second display panel 620 facing each other, and a liquid crystal layer 630 interposed between the two display panels 610 and 620. In addition, as described above, the first display panel 610 may include a plurality of gate lines G _N and G _{N -1} and data lines D _M intersecting the gate lines G _N and G _{N -1} , and a switching device. Q and a pixel electrode PE, and the second display panel 620 includes a common electrode CE and a color filter CF corresponding to the pixel electrode PE of the first display panel 610.

In this case, the switching element Q uses the pixel electrode PE of the first display panel 610 and the common electrode CE of the second display panel 620 as two terminals, and the liquid crystal interposed between the two electrodes PE and CE. Layer 630 functions as a dielectric. In addition, the pixel electrode PE is connected to the switching element Q, and the common electrode CE is formed on the entire surface of the second display panel 620 and receives the common voltage Vcom. In this case, the common electrode CE may be provided on the first display panel 610. In this case, both electrodes PE and CE may be made in a linear or bar shape.

The storage capacitor Cst is formed by overlapping a separate signal line (not shown) and the pixel electrode PE provided on the first display panel 610, and a predetermined voltage such as a common voltage Vcom is applied to the separate signal line. (Independent wiring system). In addition, the storage capacitor Cst may be formed such that the pixel electrode PE overlaps the front-end gate line directly above the insulator (shear gate method).

Meanwhile, in order to implement color display, each unit pixel should display a color, which is possible by providing a red, green, or blue color filter CF in a region corresponding to the pixel electrode PE. The color filter CF may be formed in a corresponding region of the second display panel 620 or may be formed above or below the pixel electrode PE of the first display panel 610.

Referring back to FIG. 1, in order to provide driving and control signals to the liquid crystal panel 600 having the above-described structure, the liquid crystal display 700 may include a timing controller 100, a driving voltage generator 200, and a gate driver 300. ), A data driving unit 400, a gamma voltage generator 450, a driving voltage controller 500, and the like.

The timing controller 100 receives a predetermined signal from an external controller (not shown) to generate a signal for controlling operations of the gate driver 300 and the data driver 400, and outputs a corresponding control signal to the gate driver. 300 and the data driver 400.

In addition, the timing controller 100 processes the image signals R, G, and B provided from the outside to meet the operating conditions of the liquid crystal panel 600, and provides the data signals to the data driver 400 as data drive signals.

The driving voltage generator 200 generates a plurality of driving voltages and provides them to the gate driver 300 and the liquid crystal panel 600. The driving voltage generated by the driving voltage generator 200 includes, for example, a gate on voltage Von, a gate off voltage Voff, a common voltage Vcom, and the like. In addition, the driving voltage generator 200 may adjust the magnitude of the gate-off voltage Voff generated by the driving voltage controller 500 to be described later. In more detail, the driving voltage generator 200 may increase or decrease the magnitude of the gate-off voltage Voff by a predetermined control signal V_cnt provided from the driving voltage controller 500. The adjusted gate off voltage Voff may be provided to the liquid crystal panel 600 through the gate driver 300.

The driving voltage controller 500 generates a control signal V_cnt for adjusting the size of the gate-off voltage Voff and provides it to the driving voltage generator 200. In detail, the driving voltage controller 500 may provide a liquid crystal display when the leakage current Ioff detected from the liquid crystal panel 600, for example, the gate off voltage Voff is provided to the liquid crystal panel 600 from the gate driver 300. The switching element of the panel 600, that is, the thin film transistor, is not completely turned off, and thus the leakage current Ioff may be detected. In this case, as described above, the leakage current Ioff may be detected through the dummy data line formed in the liquid crystal panel 600 and provided to the driving voltage controller 500.

In addition, the driving voltage controller 500 generates a control signal V_cnt capable of adjusting a predetermined control signal V_cnt, for example, the gate-off voltage Voff, as the leakage current Ioff, and generates the generated control signal. The signal V_cnt is fed back to the driving voltage generator 200. As described above, the driving voltage generator 200 may adjust the magnitude of the gate-off voltage Voff according to the control signal V_cnt provided from the driving voltage controller 500 and provide it to the gate driver 300. . The driving voltage controller 500 will be described in detail later with reference to FIGS. 3 to 6.

The gate driver 300 is connected to a plurality of gate lines G ₁ to G _N of the liquid crystal panel 600, and includes a gate on voltage Von and a gate off voltage Voff provided from the driving voltage generator 200. The gate driving signal formed by the combination of the gate lines G ₁ to G _N is provided.

The data driver 400 is connected to a plurality of data lines D ₁ to D _M of the liquid crystal panel 600, and generates a plurality of gray voltages based on the plurality of gamma voltages provided from the gamma voltage generator 450. The generated gray voltage is selected and applied to the unit pixel as a data driving signal, and is typically formed of a plurality of integrated circuits.

The gamma voltage generator 450 may generate two sets of gamma voltages related to transmittance of a unit pixel. That is, one of the two gamma voltages is the positive voltage and the other is the negative voltage. Herein, the positive voltage and the negative voltage mean voltages having opposite polarities with respect to the common voltage Vcom, and are alternately provided to the liquid crystal panel 600 during inversion driving.

As described above, the driving apparatuses 100, 200, 300, 400, 450, and 500 receive driving and control signals from the outside and process the signals appropriately to provide the driving and control signals of the liquid crystal panel 600. Hereinafter, the operation of the driving apparatuses 100, 200, 300, 400, 450, and 500 will be described in more detail.

First, the timing controller 100 inputs R, G, and B image signals R, G, and B from an external graphics controller (not shown) and an input control signal for controlling the display thereof, for example, a vertical synchronization signal Vsync. The horizontal synchronization signal Hsync, the main clock signal MCLK, and the data enable signal DE are provided.

In addition, the timing controller 100 generates a gate control signal CONT1, a data control signal CONT2, and the like based on the input control signal, and generates image signals R, G, and B in an operating condition of the liquid crystal panel 600. Properly handle accordingly. The gate control signal CONT1 generated by the timing controller 100 is provided to the gate driver 300, and the data control signal CONT2 and the processed image data signals R ', G', and B 'are data driver. 400 is provided.

The gate control signal CONT1 is a vertical synchronization signal STV indicating the start of output of the gate on pulse (gate on voltage section), a gate clock signal CPV for controlling the output timing of the gate on pulse, and a gate on pulse, that is, A gate output enable signal OE or the like may be included to limit the width of the gate driving signal so that the gate driving signals do not overlap each other.

The data control signal CONT2 applies a horizontal synchronization start signal STH that indicates the start of input of the image data R ', G', and B ', and a data driving signal corresponding to the data lines D ₁ to D _M. May include a load signal LOAD, an inversion driving signal RVS for inverting the polarity of the data driving signal with respect to the common voltage Vcom, a data clock signal HCLK, and the like.

The data driver 400 sequentially receives image data R ′, G ′, and B ′ corresponding to one row of the liquid crystal panel 600 according to the data control signal CONT2 provided from the timing controller 100. The image data R ', G', and B 'are converted into corresponding data driving signals by selecting a gray voltage corresponding to each image data among the gray voltages.

The gate driver 300 controls the gate driving signal Von provided from the timing controller 100, that is, the gate driving signal controlled so as not to overlap each other by being limited by the width of the gate output enable signal OE. The switching elements Q connected to the gate lines G ₁ to G _N are sequentially provided to the gate lines G ₁ to G _N , thereby turning on.

Here, while a gate-on voltage Von is applied to one gate line G ₁ to G _N and a row of switching elements Q connected thereto is turned on (this period is referred to as' 1H 'or' 1 horizontal period ( horizontal period) ', which is equal to one period of the horizontal synchronization signal STH, the data enable signal DE, and the gate clock signal CPV], and the data driver 400 associates each data driving signal with a corresponding data line. Supply to (D ₁ ~ D _M ). The data driving signal thus supplied is applied to the corresponding unit pixel through the turned-on switching element Q.

The driving voltage controller 500 receives a leakage current Ioff from the liquid crystal panel 600. For example, the driving voltage controller 500 may receive a leakage current Ioff passing through at least one dummy data line formed in the liquid crystal panel 600.

In addition, the driving voltage controller 500 may generate a control signal V_cnt from the received leakage current Ioff. In detail, the driving voltage controller 500 may generate the control signal V_cnt by comparing the leakage current Ioff detected from at least two frame operations of the liquid crystal panel 600 with each other. The generated control signal V_cnt may be fed back to the driving voltage generator 200. The driving voltage generator 200 may adjust the magnitude of the gate-off voltage Voff by using the control signal V_cnt and provide the adjusted gate-off voltage Voff to the liquid crystal panel 600.

In addition, the driving voltage controller 500 sequentially applies a gate driving signal to all frame lines of the liquid crystal panel 600, that is, all gate lines G ₁ to G _N of the liquid crystal panel 600. The control signal V_cnt may be generated by operating at least once during the operation of applying the data driving signal to the pixel. The control signal V_cnt may be applied to the next frame operation of the liquid crystal panel 600 to adjust the magnitude of the gate-off voltage Voff provided to the liquid crystal panel 600.

Hereinafter, the driving voltage controller described above will be described in detail with reference to FIGS. 3 to 6.

FIG. 3 is a block diagram of the driving voltage controller of FIG. 1, FIG. 4 is an example of a current-voltage characteristic curve of a liquid crystal panel showing the magnitude change of the gate-off voltage by the driving voltage controller of FIG. 3, and FIG. 5 is a diagram of FIG. 5. It is another example of the current-voltage characteristic curve of the liquid crystal panel which shows the magnitude | size change of the gate-off voltage by the drive voltage control part of 3.

First, referring to FIGS. 1 and 3, the driving voltage controller 500 may largely include an amplifier 510, a signal generator 520, a storage 530, and a comparison / operator 540. .

The amplifier 510 amplifies the leakage current Ioff detected by the liquid crystal panel 600 to a predetermined size. In detail, the amplifier 510 amplifies the first leakage current Ioff _(N-1) detected by the N-1 frame operation of the liquid crystal panel 600 to a predetermined size and outputs the same to the storage 530 which will be described later. can do. In addition, the amplifier 510 generates an N frame operation of the liquid crystal panel 600, that is, the driving voltage controller 500 generates the control signal V_cnt by using the first leakage current Ioff _(N-1) . The second leakage current detected by the N frame operation of the liquid crystal panel 600 which adjusts the magnitude of the gate off voltage Voff using the control signal V_cnt and is supplied with the adjusted gate off voltage Voff. Ioff _(N) may be amplified and output to the comparison / operation unit 540 to be described later. The amplifier 510 may be configured as a current amplifier using a switching element, for example, a transistor, but is not limited thereto.

The signal generator 520 generates a control signal V_cnt using the leakage current Ioff detected from the liquid crystal panel 600, and feeds back the generated control signal V_cnt to the driving voltage generator 200. Adjust the magnitude of the gate-off voltage Voff. In detail, the signal generator 520 generates the first control signal V_cnt by using the first leakage current Ioff _(N-1) provided from the amplifier 510 described above, and generates the generated first control signal. The magnitude of the gate-off voltage Voff may be adjusted by feeding back V_cnt to the driving voltage generator 200. In addition, the signal generator 520 generates the second control signal V_cnt by using the current change amount ΔIoff provided from the comparison / operator 540 to be described later, and generates the second control signal V_cnt as a driving voltage. The magnitude of the gate-off voltage Voff may be adjusted by feeding back to the generator 200. The first control signal V_cnt may be provided to the driving voltage generator 200 in the N frame operation of the liquid crystal panel 600, and the second control signal V_cnt is N + 1 of the liquid crystal panel 600. In the frame operation, the driving voltage generator 200 may be provided.

The storage unit 530 stores the first leakage current Ioff _(N-1) amplified by the amplifier 510. In detail, the storage unit 530 stores the first leakage current Ioff _(N-1) detected and amplified in the N-1 frame operation of the liquid crystal panel 600, and when the N frame operation of the liquid crystal panel 600 is performed. This may be provided to the comparison / operation unit 540. Similarly, the storage unit 530 stores the second leakage current Ioff _(N) detected and amplified in the N frame operation of the liquid crystal panel 600, and compares them during the N + 1 frame operation of the liquid crystal panel 600. It may be provided to the operation unit 540. The storage unit 530 may use, for example, an EEPROM, but is not limited thereto. Also, the storage unit 530 may include at least one converter (not shown), for example, an analog-digital or digital-analog converter.

The comparator / operator 540 includes an amplified leakage current provided from the amplifier 510, for example, a second leakage current Ioff _(N ), and an amplified leakage current provided from the storage 530, for example. The first leakage current Ioff _(N-1) is compared / computed with each other to detect a predetermined amount of current change ΔIoff. In detail, the comparison / operation unit 540 includes the first leakage current Ioff _(N-1) stored in the storage unit 530 and the second leakage current provided from the amplifier 510 in the N frame operation of the liquid crystal panel 600. It is possible to compare / calculate the magnitude of (Ioff _(N) ), and according to the result, the amount of current change ΔIoff between the first and second leakage currents Ioff _(N-1) and Ioff _(N ), eg For example, the amount of change in current magnitude can be detected. Here, the current change amount ΔIoff is detected as a positive or negative value according to the magnitudes of the two leakage currents, that is, the first and second leakage currents Ioff _(N-1) and Ioff _(N) . The current change amount ΔIoff may be provided to the signal generator 520 described above. The current change amount ΔIoff decreases the type of the control signal V_cnt, for example, the amount of the positive control signal V_cnt and the gate off voltage Voff, which increases the gate off voltage Voff. A negative control signal V_cnt may be determined.

Hereinafter, an exemplary embodiment of the operation of the driving voltage controller will be described with reference to FIGS. 1, 3, and 5.

First, the driving voltage controller 500 receives the first leakage current Ioff _(N-1) detected in the N-1 frame operation of the liquid crystal panel 600 provided with the first gate off voltage Voff _(N-1 ). The first control signal is generated and fed back to the driving voltage generator 200 to generate a second gate off voltage Voff _(N) . The second gate off voltage Voff _(N) may be provided in the N frame operation of the liquid crystal panel 600. In addition, the second gate off voltage Voff _(N) is a first voltage change amount ΔV1 from the first gate off voltage Voff _(N-1 ), for example, a first voltage having a magnitude of negative (−). The size can be adjusted by the change amount ΔV1.

Next, the driving voltage controller 500 detects the second leakage current Ioff _(N) from the N frame operation of the liquid crystal panel 600 provided with the second gate off voltage Voff _(N) . In this case, the first leakage current Ioff _(N-1) described above may be amplified by the amplifier 510 of the driving voltage controller 500 and stored in the storage unit 530.

In addition, the detected second leakage current Ioff _(N) may be amplified by the amplifier 510 and provided to the comparison / operator 540. Here, the comparison / operation unit 540 compares / operates the first leakage current Ioff _(N-1 ) and the detected and amplified second leakage current Ioff _(N) stored in the storage unit 530 to generate a first current. The change amount ΔI1 is detected. In this case, the detected first current change amount ΔI1 may be, for example, a first current change amount ΔI1 having a positive value. In addition, the amplified second leakage current Ioff _(N) may be stored in the storage unit 530.

Next, the detected first current change amount ΔI1 is provided to the signal generator 520 to generate a second control signal, and the third gate off voltage Voff _{(N +)} is adjusted according to the second control signal. ₁₎ ). In detail, the signal generator 520 may generate a second control signal from the positive first current change amount ΔI1. The second control signal may be a second voltage change ΔV2 having a direction opposite to the first voltage change ΔV1, for example, a second voltage change ΔV2 having a positive value. . Accordingly, the third gate off voltage Voff _{(N + 1)} generated by the second control signal may be scaled in a positive direction from the first gate off voltage Voff _(N-1) . The third gate off voltage Voff _{(N + 1)} may be provided to the N + 1 frame operation of the liquid crystal panel 600. In addition, the third leakage current Ioff _{(N + 1)} detected in the N + 1 frame operation of the liquid crystal panel 600 provided with the third gate off voltage Voff _{(N + 1} ) is the first leakage current Ioff _{( N-1)} ) may be represented as a second current change amount ΔI2 having a negative value, and is minimal compared to the first and second leakage currents Ioff _(N-1) and Ioff _(N) . It can be detected as a value of. Therefore, in the N + 1 frame operation of the liquid crystal panel 600, a switching element Q error, that is, a phenomenon in which the switching element Q is not turned off due to a large leakage current, can be prevented. It is possible to improve the screen defects.

Hereinafter, another exemplary embodiment of the operation of the driving voltage controller will be described with reference to FIGS. 1, 3, and 5.

First, as described above, the driving voltage controller 500 may detect the first leakage current Ioff _(N) detected in the N-1 frame operation of the liquid crystal panel 600 provided with the first gate off voltage Voff _(N-1) . _-1) generates a first control signal, and feeds it back to the driving voltage generator 200 to generate a second gate off voltage Voff _(N) . The second gate off voltage Voff _(N) may be provided in the N frame operation of the liquid crystal panel 600. In addition, the second gate off voltage Voff _(N) is a first voltage change amount ΔV1 from the first gate off voltage Voff _(N-1 ), for example, a first voltage having a magnitude of negative (−). The size can be adjusted by the change amount ΔV1.

Next, the driving voltage controller 500 detects the second leakage current Ioff _(N) from the N frame operation of the liquid crystal panel 600 provided with the second gate off voltage Voff _(N) . In this case, the first leakage current Ioff _(N-1) described above may be amplified by the amplifier 510 of the driving voltage controller 500 and stored in the storage unit 530.

In addition, the detected second leakage current Ioff _(N) may be amplified by the amplifier 510 and provided to the comparison / operator 540. Here, the comparison / operation unit 540 compares / operates the first leakage current Ioff _(N-1 ) and the detected and amplified second leakage current Ioff _(N) stored in the storage unit 530 to generate a first current. The change amount ΔI1 is detected. At this time, the detected first current change amount ΔI1 may be, for example, a first current change amount ΔI1 having a negative value. In addition, the amplified second leakage current Ioff _(N) may be stored in the storage unit 530.

Next, the detected first current change amount ΔI1 is provided to the signal generator 520 to generate a second control signal, and the third gate off voltage Voff _{(N +)} is adjusted according to the second control signal. ₁₎ ). In detail, the signal generator 520 may generate a second control signal from the negative first current change amount ΔI1. The second control signal may be a second voltage change amount ΔV2 having the same direction as the first voltage change amount ΔV1, for example, a second voltage change amount ΔV2 having a negative value. . Accordingly, the third gate off voltage Voff _{(N + 1)} generated by the second control signal may be adjusted in a negative direction from the first gate off voltage Voff _(N−1) . The third gate off voltage Voff _{(N + 1)} may be provided to the N + 1 frame operation of the liquid crystal panel 600. In addition, the third leakage current Ioff _{(N + 1)} detected in the N + 1 frame operation of the liquid crystal panel 600 provided with the third gate off voltage Voff _{(N + 1} ) is the first leakage current Ioff _{( N-1)} ) may be represented as a second current change amount ΔI2 having a negative value, and is minimal compared to the first and second leakage currents Ioff _(N-1) and Ioff _(N) . It can be detected as a value of. Therefore, in the N + 1 frame operation of the liquid crystal panel 600, a switching element Q error, that is, a phenomenon in which the switching element Q is not turned off due to a large leakage current, can be prevented. Accordingly, afterimages, crosstalk and flicker It is possible to improve the screen defects.

As described above, FIGS. 3 to 5 have described the operation of the driving voltage controller for controlling the magnitude of the gate-off voltage by using leakage current detected in two frame operations of the liquid crystal panel. However, the present invention is not limited thereto, and the operation of the driving voltage controller according to the present invention may be performed by using leakage current detected in at least two frame operations of the liquid crystal panel, that is, N-1, N, N + 1 frame operations of the liquid crystal panel. It is obvious that the magnitude of the gate-off voltage can be controlled.

Hereinafter, a driving voltage controller according to another exemplary embodiment of the present invention will be described in detail with reference to FIG. 6. 6 is a block diagram of a driving voltage controller according to another exemplary embodiment of FIG. 3. For convenience of description, members having the same functions as the members shown in FIG. 3 are denoted by the same reference numerals, and thus description thereof is omitted. As shown in FIG. 6, the driving voltage control part of this embodiment has the same structure except the following. That is, as shown in FIG. 6, the driving voltage controller 501 according to the present embodiment may further include a mixing / averaging unit 550.

1 and 6, the mixing / averaging unit 550 receives a plurality of leakage currents Ioff1, Ioff2, Ioff3, and Ioff4 from the liquid crystal panel 600. In this case, the plurality of leakage currents Ioff1, Ioff2, Ioff3, and Ioff4 may be detected and provided through a plurality of dummy data lines (not shown) formed in the liquid crystal panel 600 as described above. Here, the plurality of leakage currents Ioff1, Ioff2, Ioff3, and Ioff4 may be detected in the N-1 frame operation of the liquid crystal panel 600.

In addition, the mixing / averaging unit 550 may merge the input leakage currents Ioff1, Ioff2, Ioff3, and Ioff4 into one leakage current Ioff _(N−1) . In detail, the mixing / averaging unit 550 may add the input leakage currents Ioff1, Ioff2, Ioff3, and Ioff4, and average the generated leakage currents Ioff _(N−1) . The first leakage current Ioff _(N-1) generated as described above may be provided to the amplifier 510 as described above with reference to FIG. 3, and the driving voltage controller 500 may generate the first leakage current ( The control signal V_cnt capable of adjusting the magnitude of the gate-off voltage Voff may be generated based on Ioff _(N-1) ).

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, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

As described above, the liquid crystal display device and the driving method thereof according to the present invention can provide an optimum gate-off voltage according to the operating environment of the liquid crystal panel, thereby minimizing leakage current of the liquid crystal panel. Screen defects such as flicker and crosstalk can be improved.

Claims (13)

A liquid crystal panel having a plurality of gate lines and a plurality of data lines; A driving voltage generator configured to generate a gate on / off voltage; A gate driver sequentially providing the gate on / off voltages to the plurality of gate lines; And And a driving voltage controller configured to detect a leakage current from the liquid crystal panel, generate a control signal, and feed back the generated control signal to the driving voltage generator to adjust a magnitude of the gate-off voltage. The method of claim 1, wherein the driving voltage control unit, An amplifier for amplifying the leakage current detected from the liquid crystal panel to a predetermined magnitude; A storage unit for storing the amplified leakage current; A comparison / operation unit which compares / operates the amplified leakage current provided from the amplifier and the pre-stored leakage current provided from the storage unit to detect a predetermined amount of current change; And And a signal generator for generating a control signal according to the detected amount of current change and feeding back the generated control signal to the driving voltage generator. The method of claim 2, The signal generation unit generates a first control signal using the first leakage current detected from the N-1 frame operation of the liquid crystal panel, and the first control signal is fed back to the N frame operation of the liquid crystal panel. Device. The method of claim 3, wherein And the amplifying unit amplifies the first leakage current to output the storage unit, and amplifies the second leakage current detected from the N frame operation of the liquid crystal panel and outputs the second leakage current to the comparison / operation unit. The method of claim 3, wherein And the comparing / operating unit detects the amount of change of current having a positive (+) or negative (−) value by comparing / operating the magnitudes of the first leakage current and the second leakage current. The method of claim 3, wherein The signal generation unit generates a second control signal using the current change amount, and the second control signal is fed back to the N + 1 frame operation of the liquid crystal panel. Preparing a liquid crystal panel having a plurality of gate lines and a plurality of data lines; Sequentially providing a gate on / off voltage to the liquid crystal panel; Detecting a leakage current from the liquid crystal panel and generating a control signal capable of adjusting the magnitude of the gate-off voltage using the leakage current; And And adjusting the size of the gate-off voltage using the control signal. The method of claim 7, wherein generating a control signal capable of adjusting the magnitude of the gate off voltage, Providing a first gate-off voltage to an N-1 frame operation of the liquid crystal panel to detect a first leakage current and to amplify / store the detected first leakage current; Generating a first control signal using the first leakage current; Providing a second gate off voltage generated by the first control signal to an N frame operation of the liquid crystal panel to detect a second leakage current and amplify the detected second leakage current; Comparing / operating the stored first leakage current and the second leakage current to detect a current change amount; And And generating a second control signal using the current change amount. The method of claim 8, And the second gate off voltage is adjusted in size from the first gate off voltage to a first voltage change amount. The method of claim 8, And the current change amount is detected as a positive value or a negative value according to a change in magnitude between the first leakage current and the second leakage current. The method of claim 10, And when the amount of current change is positive, the second control signal has a second voltage change amount in a direction opposite to the first voltage change amount. The method of claim 10, And when the current change amount is negative, the second control signal has a second voltage change amount in the same direction as the first voltage change amount. The method of claim 8, Adjusting the magnitude of the gate off voltage using the control signal may include driving a liquid crystal display device to provide a third gate off voltage generated by the second control signal to an N + 1 frame operation of the liquid crystal panel. Way.

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