KR20150025104A - Liquid Crystal Display and driving method the same - Google Patents

Liquid Crystal Display and driving method the same Download PDF

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Publication number
KR20150025104A
KR20150025104A KR20130102291A KR20130102291A KR20150025104A KR 20150025104 A KR20150025104 A KR 20150025104A KR 20130102291 A KR20130102291 A KR 20130102291A KR 20130102291 A KR20130102291 A KR 20130102291A KR 20150025104 A KR20150025104 A KR 20150025104A
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South Korea
Prior art keywords
common voltage
voltage
pixels
data
level
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KR20130102291A
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Korean (ko)
Inventor
김태진
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삼성디스플레이 주식회사
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Priority to KR20130102291A priority Critical patent/KR20150025104A/en
Publication of KR20150025104A publication Critical patent/KR20150025104A/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3614—Control of polarity reversal in general
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3696—Generation of voltages supplied to electrode drivers
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0209—Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
    • G09G2320/0214—Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display with crosstalk due to leakage current of pixel switch in active matrix panels
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • G09G2330/021—Power management, e.g. power saving

Abstract

A liquid crystal display according to an embodiment of the present invention includes a pixel portion for storing a voltage level corresponding to a data signal and including a plurality of pixels including a storage capacitor connected between a pixel electrode and a second common voltage electrode; A common voltage driver for supplying a second common voltage to each of the plurality of pixels; And determining whether or not the video data of the current frame is changed from the video data of the previous frame and, if the video data is not changed, And the common voltage driver includes a switch unit connected to pixels to which a data signal of the same polarity is applied by inversion driving.

Description

[0001] The present invention relates to a liquid crystal display and a driving method thereof,

An embodiment of the present invention relates to a liquid crystal display and a driving method thereof.

A liquid crystal display device includes a liquid crystal layer formed between two substrates facing each other and arranged to align liquid crystal molecules of the liquid crystal layer by an electric field generated by applying a voltage to a pair of electrodes formed on at least one substrate of the two substrates And adjusting the light transmittance of the liquid crystal layer to display an image.

2. Description of the Related Art In general, an active matrix type liquid crystal display device in which pixels defined by gate wirings and data wirings intersecting each other are arranged in a matrix and switching elements and pixel electrodes are formed in each pixel is widely used in the liquid crystal display device.

At this time, a data signal corresponding to the image data is applied to the plurality of pixels, and considerable power is consumed to generate and drive the data signal.

On the other hand, each of the plurality of pixels may be provided with a storage capacitor for storing the level of the data signal. The storage capacitor stores the level of the data signal until the data signal is applied and the next data signal is applied. The storage capacitor is cut off from the data line carrying the data signal by the switching element other than the timing at which the data signal is applied. However, when a leakage current is generated through the switching element, the charge stored in the storage capacitor may leak and the image quality may deteriorate.

Embodiments of the present invention provide a liquid crystal display device and a method of driving the same that reduce power consumption for driving a data signal and prevent image quality degradation due to a leakage current from a storage capacitor.

It is another object of the present invention to provide a liquid crystal display device and a method of driving the same that prevent a problem of display abnormality that occurs during a screen update after the leakage current compensation for a predetermined image display is completed.

According to an aspect of the present invention, there is provided a liquid crystal display device including a plurality of pixels, each pixel including a storage capacitor connected between a pixel electrode and a second common voltage electrode, ; A common voltage driver for supplying a second common voltage to each of the plurality of pixels; And determining whether or not the video data of the current frame is changed from the video data of the previous frame and, if the video data is not changed, And the common voltage driver includes a switch unit connected to pixels to which a data signal of the same polarity is applied by inversion driving.

The switch unit may include a first switch for connecting the second common voltage electrode of the pixels to the reference second common voltage source, a second common voltage electrode for connecting the second common voltage electrode and the second common voltage source, And at least one second switch for connecting the first switch and the second switch.

At this time, the reference second common voltage source has a constant voltage level, and the second-1 common voltage source applies a positive (+) polarity data voltage to the pixel electrodes of the pixels, The second-common voltage source changes the voltage level to increase the level of the voltage to compensate for the voltage drop, and when the data voltage of negative polarity is applied to the pixel electrode of the pixels, The level of the voltage is decreased in order to compensate for the voltage drop of the voltage.

In another embodiment, the switch unit includes: a first switch unit connected to pixels to which a data signal of a first polarity is applied; And a second switch portion connected to the pixels to which the data signal of the second polarity is applied.

In this case, the first switch unit and the second switch unit are respectively composed of a 2-1 common voltage source, a reference second common voltage source having a reference voltage level, and three switches connected to the 2-2 common voltage source.

The first switch unit may further include: a 1a switch for connecting the second common voltage electrode of the pixels to which the data signal of the first polarity is applied by the first control signal to the second common voltage source; A first b switch for connecting the second common voltage electrode of the pixels to which the data signal of the first polarity is applied by the first control signal to the reference second common voltage source; And a first c switch for connecting the second common voltage electrode of the pixels to which the data signal of the first polarity is applied by the first control signal to the second-1 common voltage source.

The second switch unit may include: a 2a switch connecting the second common voltage electrode of the pixels to which the data signal of the second polarity is applied by the 2a control signal to the 2-2 common voltage source; A second switch for connecting the second common voltage electrode of the pixels to which the data signal of the second polarity is applied by the second control signal to the reference second common voltage source; And a second c switch for connecting the second common voltage electrode of the pixels to which the data signal of the second polarity is applied by the second control signal to the second-1 common voltage source.

The compensation control unit controls the storage capacitors of the plurality of pixels to store a voltage level corresponding to the video data of the current frame when the video data is changed.

In addition, the compensation controller controls the reference second common voltage to be applied to the storage capacitor during a frame period in which the video data is changed.

The compensation control unit controls the second common voltage corresponding to the inversion driving to be applied in a period for displaying the still image to display the still image based on the changed image data, The common voltage may be a 2 < nd > common voltage that changes in the direction of increasing the voltage level to compensate for the voltage drop of the pixel electrode, or a second common voltage that changes in the direction of decreasing the voltage level to compensate for the voltage drop of the pixel electrode 2-2 One of the common voltages.

A driving method of a liquid crystal display according to an embodiment of the present invention includes a liquid crystal display in which a plurality of pixels including a storage capacitor connected between a pixel electrode and a second common voltage electrode are arranged, A method of driving a device, comprising: determining whether image data of a current frame has changed from image data of a previous frame; Storing a voltage level corresponding to image data of a current frame in a storage capacitor of each of the plurality of pixels when the image data is changed; And changing a level of a second common voltage applied to the second common voltage electrode of each of the plurality of pixels when the image data is not changed, The reference second common voltage is applied to the capacitor.

Further, the method may further include displaying a new still image by the changed image data, and a second common voltage corresponding to the inversion driving is applied in a section displaying the new still image.

The second common voltage corresponding to the inversion driving may be a second common voltage or a second common voltage that changes in a direction of increasing the voltage level to compensate for the voltage drop of the pixel electrode, 2 < / RTI > common voltage that changes in the direction in which the level of the second common voltage decreases.

The step of changing the level of the second common voltage may further include the step of changing the level of the second common voltage when the video data is not changed by not writing the video data of the current frame to the pixel electrodes of the plurality of pixels, The level of the second common voltage is changed so as to compensate the voltage drop of the pixel electrode.

According to the embodiment of the present invention, power consumption for driving a data signal is reduced, and an image quality deterioration due to a leakage current from the storage capacitor is prevented.

Further, there is an advantage of preventing the problem of display abnormality, which occurs at the time of screen update, after the leakage current compensation for a predetermined image display (for example, still image display) is completed.

1 is a block diagram showing a configuration of a liquid crystal display device according to an embodiment of the present invention;
2 is a circuit diagram showing a structure of a pixel PX according to an embodiment of the present invention.
3 is a flowchart showing a method of driving a liquid crystal display according to an embodiment of the present invention.
FIG. 4 is a timing chart of signals corresponding to the driving method of the liquid crystal display according to the embodiment of the present invention shown in FIG. 3;
5 is a flowchart showing a driving method of a liquid crystal display according to another embodiment of the present invention.
6 is a circuit diagram showing a partial configuration of a liquid crystal display device according to another embodiment of the present invention.
Fig. 7 is a timing chart of signals for driving the liquid crystal display shown in Fig. 6; Fig.
8 is a circuit diagram showing a part of the configuration of a liquid crystal display device according to another embodiment of the present invention.
9 is a circuit diagram showing a part of a configuration of a liquid crystal display device according to another embodiment of the present invention.

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

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

1, a liquid crystal display 100 according to an exemplary embodiment of the present invention includes a timing controller 110, a scan driver 120, a data driver 130, a pixel unit 140, a compensation controller 150, A common voltage driver 160, a backlight driver 170, and a backlight unit 180.

The timing controller 110 receives image data and receives a data enable signal, a vertical synchronizing signal, a horizontal synchronizing signal, and a clock signal from an external device (not shown) or a control block (not shown) A data drive control signal, and a gate drive control signal.

The timing controller 110 receives input control signals such as a horizontal synchronizing signal, a clock signal, and a data enable signal, and outputs a data driving control signal. Here, the data driving control signal may include a source shift clock, a source start pulse, a polarity control signal, a source output enable signal, and the like, as a signal for controlling the operation of the data driver 130. The timing controller 110 receives a vertical synchronization signal, a clock signal, and the like, and outputs a gate drive control signal. The gate drive control signal is a signal for controlling the operation of the scan driver 120, and may include a gate start pulse and a gate output enable signal.

The scan driver 120 generates gate signals sequentially having scan pulses in accordance with the gate drive control signals supplied from the timing controller 110 and supplies the gate signals to the gate lines G1 to Gn. At this time, the scan driver 120 determines the voltage level of the scan pulse according to the high level gate voltage VGH and the low level gate voltage VGL generated from a DC / DC converter (not shown) or the like. The voltage level of the scan pulse may be varied depending on the type of the switching device provided in the pixel PX. That is, when the switching element is implemented as an n-type transistor, the scan pulse has a high-level gate voltage during the active period, and when the switching element is implemented as a p-type transistor, Voltage.

The data driver 130 supplies a data signal to the data lines D1 to Dm in response to the video data signal and the data driving control signal supplied from the timing controller 110. [ More specifically, the data driver 130 samples and latches the image data signal supplied from the timing controller 110, and then latches the image data signal supplied from the pixel unit 140 using a gamma voltage supplied from a gamma voltage generating circuit Into an analog data signal capable of expressing gradation in the pixels PX.

The pixel portion 140 includes a plurality of pixels PX located at intersections of the data lines D1 to Dm and the gate lines G1 to Gn. Each pixel PX is connected to at least one data line Di and at least one gate line Gj. The gate lines G1 to Gn extend in the row direction and are arranged in parallel, and the data lines D1 to Dm extend in the column direction and are arranged in parallel with each other. It is of course possible that the gate lines G1 to Gn extend in the column direction and the data lines D1 to Dm extend in the row direction. The structure of the pixel PX according to an embodiment of the present invention will be described with reference to FIG.

2 is a circuit diagram showing a structure of a pixel PX according to an embodiment of the present invention.

Referring to FIG. 2, a pixel PX according to an embodiment of the present invention includes a first transistor M1, a liquid crystal cell LC, and a storage capacitor Cst. The first transistor M1 has a gate electrode connected to the gate line Gj, a first electrode connected to the data line Di and a second electrode connected to the first node N1. The first transistor M1 serves as a switching element and may be implemented as a thin film transistor (TFT). The first node N1 is a node electrically equivalent to the pixel electrode. The liquid crystal cell LC is provided between the first node N1 and the first common voltage electrode Vcom1. A first common voltage is applied to the first common voltage electrode Vcom1. The liquid crystal cell LC is equivalent to a pixel electrode, a first common voltage electrode (Vocm1), and liquid crystal molecules interposed therebetween.

The storage capacitor Cst is connected between the first node N1 and the second common voltage electrode Vcom2. And a second common voltage is applied to the second common voltage electrode Vcom2.

When the scan pulse is input to the gate line Gj, the first transistor M1 is turned on and the data signal input through the data line Di is applied to the first node N1. The voltage level corresponding to the data signal is stored in the storage capacitor Cst by the data signal. The liquid crystal molecules of the liquid crystal cell LC change its orientation in accordance with the voltage of the first node N1, and the light transmittance is changed.

The common voltage driver 160 generates the first common voltage and the second common voltage and applies the first common voltage and the second common voltage to the plurality of pixels PX, respectively. The first common voltage is a voltage applied to one end of the liquid crystal cell LC and the second common voltage is a voltage applied to one end of the storage capacitor Cst. At this time, the first common voltage electrode Vcom1 and the second common voltage electrode Vcom2 may be applied with the same voltage.

However, the structure of the common voltage electrode may vary depending on the inversion driving method of the liquid crystal display device.

The liquid crystal deteriorates when a constant electric field is continuously applied to the liquid crystal layer of the liquid crystal display device, resulting in a residual image due to the DC voltage component. Therefore, in order to prevent deterioration of the liquid crystal and to remove the DC voltage component The voltage of the data signal applied to each pixel is applied in such a manner that positive and negative voltages are repeated based on the voltage, which is referred to as an inversion driving method.

The inversion driving method includes a frame inversion method in which the polarity of a data signal is inverted in units of one frame of a picture, a line inversion method in which a polarity of a data signal is inverted in units of gate lines, There is a dot inversion method in which the pixels are supplied in an inverted manner for each of adjacent pixels and are supplied in a reversed manner in units of one frame of an image.

The first common voltage electrode Vcom1 is commonly connected to the plurality of pixels PX and the second common voltage electrode Vcom2 is also connected to the plurality of pixels PX when the liquid crystal display device 100 adopts the frame inversion driving method. (PX) of the pixel PX. In this case, the common voltage driver 160 generates and outputs one first common voltage and one second common voltage electrode.

When the liquid crystal display device 100 adopts the line inversion method or the dot inversion method, the first common voltage electrode Vcom1 and the second common voltage electrode Vcom2 are connected to the pixels PX having the same polarity, May be commonly connected between the pixels PX to which the data signal of the same polarity is applied. That is, in the case of the line inversion method, the first common voltage electrode (Vcom1) and the second common voltage electrode (Vcom2) may be connected in units of rows or in units of columns. When the dot inversion method is adopted, the first common voltage electrode Vcom1 and the second common voltage electrode Vcom2 may be connected in common in units of dots. In this case, the common voltage driver 160 generates and outputs two first common voltages of different levels and two second common voltages of different levels.

The compensation controller 150 determines whether the video data of the current frame has changed from the video data of the previous frame and outputs the video data of the current frame to the storage capacitor Cst of each of the plurality of pixels PX, Stores the voltage level corresponding to the data and changes the level of the second common voltage applied to the second common voltage electrode (Vcom2) of each of the plurality of pixels (PX) when the image data is not changed, (11) and the common voltage driver (160). The detailed operation of the compensation control unit 150 will be described below again.

The backlight unit 180 is disposed on the rear surface of the pixel unit 140 and is emitted by the backlight driving signal BLC supplied from the backlight driving unit 170 to apply light to the pixels PX of the pixel unit 140 Investigate. The backlight driving unit 170 generates a backlight driving signal BLC under the control of the timing control unit 110 and outputs the backlight driving signal BLC to the backlight unit 180 to control the light emission of the backlight unit 180. [

3 is a flowchart showing a driving method of a liquid crystal display according to an embodiment of the present invention.

Referring to FIG. 3, in a method of driving a liquid crystal display (LCD) according to an exemplary embodiment of the present invention, when a frame is switched and image data is input (S302), whether the image data of the current frame is changed from the image data of the previous frame (S304).

When the image data is changed, the compensation controller 150 applies a data signal to the pixel electrodes of the pixels PX and controls the timing controller 110 to store the voltage level corresponding to the data signal in the storage capacitor Cst (S305). In this case, the timing controller 110 controls the scan driver 120 and the data driver 130 so that the data driver 130 generates a data signal corresponding to the input image data and outputs the data signal to each pixel PX , And the scan driver 120 scans the pixels PX in units of rows and stores the voltage level corresponding to the data signal in the storage capacitor Cst of the pixels PX.

If the image data is not changed, the compensation controller 150 controls the common voltage driver 160 so as to compensate for the voltage drop of the pixel electrode by changing the second common voltage (S306). In this case, even if the frame is switched, the scan driver 120 and the data driver 130 do not write data signals to the pixels PX.

In the present embodiment, even when the frame is switched, the data signal is not written to the pixels PX when there is no change in the image data, that is, when the still image is displayed, . In this case, although the first transistor M1 of each of the pixels PX is turned off, a leakage current may be generated through the first transistor M1, and the voltage level of the pixel electrode may be lowered. It is difficult to substantially eliminate the leakage current of the first transistor M1. In the case where there is no change in the image data even if the frame is switched, the embodiments of the present invention can be applied to a case where the data is not written to the pixels PX, The level of the voltage is changed to prevent the deterioration of image quality due to the voltage drop of the pixel electrode. Therefore, the embodiments of the present invention can reduce the power consumption of the display device 100 and prevent the deterioration of image quality.

The manner in which the compensation control unit 150 changes the second common voltage includes, for example, a method of measuring the voltage drop of the pixel electrode of the pixels PX and changing the second common voltage according to the voltage drop level, A method of changing the second common voltage by a predetermined level every cycle, or the like.

For example, when the frame is switched, the compensation controller 150 measures the voltage of the pixel electrode of the pixels PX when a static image without change of the image data is displayed, and when the voltage drop of the pixel electrode exceeds a reference value , The voltage level of the pixel electrode of the pixels PX is compensated by changing the level of the second common voltage Vcom2 by the voltage drop amount. For this purpose, the voltage measuring unit 190 may measure a voltage of a pixel electrode of a part or all of the plurality of pixels PX. According to this embodiment, since the voltage drop of the pixel electrode is compensated by the amount in which the voltage drop actually occurs, it is possible to compensate the voltage drop of the pixel electrode more accurately.

When the second common voltage is changed, the voltage of the pixel electrode of the plurality of pixels PX is boosted through the storage capacitor Cst, so that the voltage drop is compensated.

The steps S302, S304, S305, and S306 of FIG. 3 are repeated until the driving of the display device is terminated, that is, until the input of the image data is completed (S308).

4 is a timing chart of signals corresponding to the driving method of the liquid crystal display according to the embodiment of the present invention shown in FIG.

Here, G1 is the signal level of the gate line G1 in the first row, Gn is the signal level of the gate line Gn in the nth row, Cst is the signal level of the storage capacitor of the pixel in the first row among the plurality of pixels PX, (I.e., the voltage level of the data signal applied to the pixel electrode) of the pixel of the first row, Vcom2 is the voltage level of the second common (That is, the voltage level of the second common voltage electrode). Hereinafter, any pixel in the first row is referred to as a first pixel for convenience of explanation.

Referring to FIG. 4, after the data signal is applied to the first pixel (T1), the level of the second common voltage may increase and the voltage level Vpx of the pixel electrode may be maintained constant. That is, as shown in FIG. 4, the voltage level of the storage capacitor Cst of the first pixel gradually decreases due to the leakage current. Even if the voltage across the storage capacitor Cst decreases, the second common voltage increases While boosting the voltage level Vpx of the pixel electrode through the storage capacitor Cst to maintain the voltage level Vpx of the pixel electrode constant.

In FIG. 4, the time T2 indicates a time point at which the data signal is applied to the pixel electrode after the image data is changed. Therefore, according to the present embodiment, the voltage level Vpx of the pixel electrode can be maintained constant during the first still image display interval P1 between the T1 point and the T2 point of time when there is no change in the image data.

In FIG. 4, the second common voltage level Vcom2 is continuously increased during the P1 period. However, it is also possible that the second common voltage level Vcom2 increases discontinuously.

However, according to the embodiment shown in FIGS. 3 and 4, when a new data signal is applied after the first still image display period P1, the image of the pixel portion may be momentarily displayed abnormally.

This is because the second common voltage level increased during the P1 period is changed to the level of the specific voltage when the new data signal is applied. In this case, the voltage level of the pixel electrode written to the storage capacitor by the application of the new data signal is compensated I can not.

Accordingly, another embodiment of the present invention provides a liquid crystal display device and a method of driving the same for preventing a problem of display abnormality that occurs during a screen update after the leakage current compensation for a predetermined image display (first still image display) is completed .

Hereinafter, an embodiment for preventing a display error problem occurring in a screen update by applying various inversion driving methods in displaying a second still image by a new data signal after the first still image display period P1 described above More specifically,

5 is a flowchart showing a driving method of a liquid crystal display according to another embodiment of the present invention.

According to another embodiment of the present invention, when the video data changes during frame switching while applying the inversion driving method, the reference common voltage is applied during the corresponding frame period, and if there is no change in the video data, The level of the second common voltage is applied to each pixel.

Referring to FIG. 5, in the method of driving the liquid crystal display according to the present embodiment, when the frame is switched and the video data is inputted (S502), it is determined whether or not the video data of the current frame is changed from the video data of the previous frame (S504).

3, the compensation controller 150 controls the common voltage driver 160 so as to compensate for the voltage drop of the pixel electrode by changing the second common voltage, as in the embodiment shown in FIG. 3 (S510). In this case, even if the frame is switched, the scan driver 120 and the data driver 130 do not write data signals to the pixels PX.

When the video data is changed, the compensation control unit 150 of FIG. 1 applies a data signal to the pixel electrodes of the pixels PX to store a voltage level corresponding to the data signal in the storage capacitor Cst 1 < / RTI > At this time, the reference second common voltage is applied to the storage capacitor Cst during the frame period in which the video data is changed (S506).

 After applying the reference common voltage during the corresponding frame period, inversion driving is performed to display the second still image by the new data signal. That is, the second common voltage corresponding to the inversion driving is applied in the section displaying the second still image (S508). The inversion driving according to the present embodiment may be any one of a dot inversion method, a line inversion method, and a frame inversion method.

That is, in the embodiment of the present invention, when a new second still image is displayed, the level of the second common voltage determined by the inversion driving is applied to each pixel to change the second common voltage to compensate the voltage drop of the pixel electrode (S510).

In this case, in the embodiment of the present invention, the voltage drop of the pixel electrode is compensated for according to the polarity of the data signal voltage applied to the storage capacitor Cst and the liquid crystal cell LC of each pixel during the previous first still image display period P1 The direction in which the second common voltage Vcom2 is changed is changed.

That is, when displaying the new second still image, if a data voltage of negative polarity is applied to the pixel electrode based on the second common voltage Vcom2 during the P1 period, The data voltage of positive polarity is applied to the pixel electrode during the period of displaying the second common voltage Vcom2, so that the second common voltage Vcom2 is changed in an increasing direction to compensate for the voltage drop of the pixel electrode.

On the other hand, if a data voltage of positive polarity is applied to the pixel electrode based on the second common voltage Vcom2 during the P1 period, then during a period of displaying a new second still image, ), The second common voltage Vcom2 is changed to decrease in order to compensate for the voltage drop of the pixel electrode.

Steps S502, S504, S506, S508, and S510 are repeated until the driving of the liquid crystal display device is terminated, that is, until the input of image data is completed (S512).

FIG. 6 is a circuit diagram showing a part of the configuration of a liquid crystal display device according to another embodiment of the present invention, and FIG. 7 is a timing chart of signals for driving the liquid crystal display device shown in FIG.

6 and 7 are views for explaining an embodiment in which the dot inversion driving method is applied to the inversion driving method.

FIG. 6 is a cross-sectional view of a liquid crystal display device shown in FIG. 1, in which the common voltage driver 160 and four adjacent pixels (PX) arranged in the gate line of the first row among the plurality of pixels PX arranged in the pixel portion 140 Only the pixels are shown.

6 is applied to the pixels connected to the gate lines of the remaining rows and the data lines of the remaining columns in the liquid crystal display according to the embodiment of the present invention do.

In the dot inversion method, the polarity of the data signal is supplied in an inverted manner for each of the adjacent pixels. For example, a (+) polarity data signal is applied to the pixels PXoo connected to the odd-numbered gate lines and the odd- (-) polarity data signal is applied to the pixels PXoe connected to the odd-numbered gate lines and the even-numbered data lines.

Further, a negative (-) polarity data signal is applied to the pixels PXeo connected to the odd-numbered gate lines and the odd-numbered data lines, and the pixels PXee connected to the odd-numbered gate lines and the odd- A data signal having a positive polarity is applied.

Since the embodiment shown in FIG. 6 is an example of four pixels arranged in the gate line of the first row, data signals having (+), (-), (+) and (-) polarities from the left are applied .

In this case, the pixels PXoo to which the data signals of the first polarity (for example, the (+) polarity) are applied among the pixels arranged in the gate line of the same row are connected to the first switch unit And the pixels PXoe to which the data signals of the second polarity (for example, (-) polarity) are applied are connected to the second switch unit 164 of the common voltage driver 160. [

The first switch unit 162 and the second switch unit 164 are respectively connected to the second-1 common voltage source + VCOM2, the reference second common voltage source ref_VCOM2 having the reference voltage level, And -VCOM2.

In this case, the reference second common voltage source ref_VCOM2 has a constant voltage level, and the second-1 common voltage source + VCOM2 corresponds to a case where a positive (+) polarity data voltage is applied to the pixel electrode (- VCOM2) changes in a direction in which the level of the voltage increases in order to compensate for the voltage drop of the pixel electrode. When the data voltage of negative polarity is applied to the pixel electrode The level of the voltage is decreased in order to compensate the voltage drop of the pixel electrode.

That is, the first switch unit 162 is connected to the 1a-th switch T1a (T1a) for connecting the second common voltage electrode of the pixels PXoo to the 2-2 common voltage source (-VCOM2) by the 1a control signal CS1a A first b switch T1b for connecting a second common voltage electrode of the pixels PXoo to a reference second common voltage source ref_VCOM2 having a reference voltage level by a first control signal CS1b, And a first c switch T1c for connecting the second common voltage electrode of the pixels PXoo to the second-1 common voltage source + VCOM2 by a signal CS1c.

Similarly, the second switch unit 164 is connected to the second switch T2a (T2a) for connecting the second common voltage electrode of the pixels PXoe with the second-second common voltage source (-VCOM2) by the second control signal CS2a, A second b switch T2b for connecting a second common voltage electrode of the pixels PXoe to a reference second common voltage source ref_VCOM2 having a reference voltage level by a second control signal CS2b, And a second c switch T2c for connecting the second common voltage electrode of the pixels PXoe to the second-1 common voltage source (+ VCOM2) by a signal CS2c.

A method of driving a dot inversion driving type liquid crystal display according to an embodiment of the present invention will be described with reference to FIGS. 6 and 7. FIG.

7 is a timing chart of the driving waveform of FIG. 4, in which the image data is changed after the first still image display period P1 and the data signal is applied to the pixel electrode, To T3) and a period (P2, T3 to T4) for displaying a new second still image by the data signal applied during the frame period will be described.

G1 is the signal level of the gate line G1 in the first row, Gn is the signal level of the gate line Gn in the nth row, Cst is the voltage level of the storage capacitor Cst, Vpx is the voltage level of the pixel electrode (That is, the voltage level of the data signal applied to the pixel electrode), + Vcom2 is the level of the second common voltage (i.e., the voltage level of the second-1 common voltage source + VCOM2) Ref_Vcom2 is the level of the second common voltage having the reference voltage level (that is, the voltage level of the reference second common voltage source ref_VCOM2), and -Vcom2 is the voltage level of the second common voltage (I.e., the voltage level of the second-second common voltage source (-VCOM2)).

Hereinafter, among the pixels arranged in the first row, PXoo and PXoe in FIG. 6 will be described.

CS1b, CS1a and CS1c are control signals applied to the first switch unit 162 of the common voltage driver 160 connected to PXoo of FIG. 6, and CS2b, CS2a and CS2c are control signals applied to the common voltage driver And the control signal applied to the second switch unit 164 of the second switch 160.

That is, referring to FIG. 7, the reference second common voltage ref_Vcom2 is applied during one frame period (T2 to T3) after the time T2 when a new data signal is applied to the PXoo.

To this end, a high level CS1b signal is applied to turn on the first b switch T1b connected to the reference second common voltage source ref_VCOM2 having the reference voltage level.

As shown in FIG. 3, since a positive polarity data voltage is applied to the pixel electrode based on the reference second common voltage ref_Vcom2 during the P1 period, (-) polarity data voltage is applied to the pixel electrode during the period P2, so that -Vcom2 is applied to the section P2 as shown in the figure.

At this time, -Vcom2 changes in a decreasing direction to compensate for the voltage drop of the pixel electrode as shown in the figure.

To this end, during the period P2, a high-level CS1a signal is applied to turn on the 1a-th switch T1a connected to the 2-2 common voltage source (-VCOM2).

6 and 7 are dot inversion driving, in the case of PXoe, which is a pixel adjacent to the PXoo, during the P1 interval, the data voltage (-) of negative polarity is applied to the pixel electrode based on the reference second common voltage (ref_Vcom2) .

Referring to FIG. 7, a reference second common voltage (ref_Vcom2) is applied during one frame period (T2 to T3) after a new data signal is applied to the PXoe (T2) The CS2b signal of high level is applied so as to turn on the second switch T2b connected to the second common voltage source ref_VCOM2.

However, since the data voltage of negative polarity is applied to the pixel electrode on the basis of the reference second common voltage (ref_Vcom2) during the period P1 in the PXoe, during the period P2 during which the second still image is displayed, The data voltage of positive polarity is applied to the electrode, and the second-1 common voltage + Vcom2 is applied to the electrode during the period P2 as shown in FIG.

At this time, + Vcom2 is changed in an increasing direction to compensate for the voltage drop of the pixel electrode as shown in the figure.

To this end, during the period P2, a high level CS2c signal is applied to turn on the second c switch T2c for connecting to the second-1 common voltage source (+ VCOM2).

8 is a circuit diagram showing a partial configuration of a liquid crystal display device according to another embodiment of the present invention.

FIG. 8 is a view for explaining an embodiment in which a line inversion driving method is applied among the inversion driving methods. In the configuration of the liquid crystal display device shown in FIG. 1, the common voltage driving part 160 and the pixel part 140 are arranged Only three adjacent pixels arranged in the gate line of the first row among the plurality of pixels PX and adjacent three pixels arranged in the gate line of the second row are shown.

However, this is for convenience of explanation, and the liquid crystal display according to the embodiment of the present invention is equally applied to the pixels shown in FIG. 8 connected to the gate lines of the remaining rows.

In the line inversion driving method, the polarity of the data signal is supplied in a line-by-line manner. For example, a (+) polarity data signal is applied to the pixels PXo connected to the odd-numbered gate lines, A data signal of (-) polarity is applied to the connected pixels PXe.

6, the pixels PXo arranged in the odd-numbered gate lines to which the data signals of the first polarity (for example, (+) polarity) are applied are supplied to the common voltage driver 160 The pixels PXe to which the data signals of the second polarity (for example, (-) polarity) are applied are connected to the second switch unit 164 of the common voltage driver 160 ).

However, the configuration of the first and second switch sections 162 and 164 and the connection relationship thereof are the same as those of the embodiment of FIG. 6, and thus a detailed description thereof will be omitted.

9 is a circuit diagram showing a part of the configuration of a liquid crystal display according to another embodiment of the present invention.

FIG. 9 is a view for explaining an embodiment in which a frame inversion driving method is applied among the inversion driving methods.

In the frame inversion driving method, the polarity of the data signal is supplied in a frame-by-frame manner. For example, in the odd-numbered frame, a data signal having a positive polarity is applied to all pixels PX of the pixel unit 140, (+) Polarity data signal is applied to all the pixels PX of the pixel portion 140 in the frame.

Accordingly, in the embodiment of the present invention, when a data signal having a (+) polarity is applied to the pixels in the first still image display period P1, then in the second still image display period P2, Is applied.

For this, in the embodiment of FIG. 9, unlike the embodiment of FIG. 8, one common switch unit 166 is provided in the common voltage driver 160, and the third switch unit 166 is connected to the (+ VCOM2) to which the voltage (+ VCOM2) and the second-second common voltage (-VCOM2) are alternately applied and a reference second common voltage source (ref_VCOM2) having the reference voltage level As shown in FIG.

That is, the third switch unit 166 is connected to the third common voltage source (ref_VCOM2) having the reference voltage level by connecting the second common voltage electrode of the pixels PX with the third control signal CS3a, The second common voltage + VCOM2 and the second common voltage -VCOM2 are alternately turned on by the second common voltage electrode of the pixels PX by the switch T3a and the third control signal CS3b, And a third switch T3b for connecting the second common voltage source (+/- VCOM2) to the second common voltage source (+/- VCOM2).

That is, the third switch T3b serves to connect the second common voltage electrode of the pixels to the second-1 common voltage source or the second -2 common voltage source.

However, the frame inversion driving method can also be performed through the configuration of the embodiment shown in Fig.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the present invention.

100: liquid crystal display device 140:
160: common voltage driving unit 162: first switch unit
164: second switch unit 166: switch unit

Claims (18)

A pixel portion for storing a voltage level corresponding to the data signal and including a storage capacitor connected between the pixel electrode and the second common voltage electrode;
A common voltage driver for supplying a second common voltage to each of the plurality of pixels; And
The method comprising: determining whether the video data of the current frame has changed from the video data of the previous frame; and if the video data is not changed, determining whether the level of the second common voltage applied to the second common voltage electrode of each of the plurality of pixels And a compensation controller for controlling the common voltage driver to change the common voltage,
The common voltage driver includes:
And a switch unit connected to pixels to which a data signal of the same polarity is applied by inversion driving. The method according to claim 1,
Wherein,
A first switch for connecting the second common voltage electrode of the pixels to the reference second common voltage source,
And at least one second switch for connecting the second common voltage electrode of the pixels to the second common voltage source or the second common voltage source. 3. The method of claim 2,
The reference second common voltage source has a constant voltage level,
The second-1 common voltage source changes in a direction in which the level of the voltage increases to compensate for the voltage drop of the pixel electrode in response to the application of a positive (+) polarity data voltage to the pixel electrode of the pixels ,
The second -2 common voltage source changes in a direction in which the level of the voltage decreases in order to compensate for the voltage drop of the pixel electrode in response to the application of the data voltage of negative polarity to the pixel electrode of the pixels Wherein the liquid crystal display device is a liquid crystal display device. The method according to claim 1,
Wherein,
A first switch connected to the pixels to which the data signal of the first polarity is applied;
And a second switch connected to the pixels to which the data signal of the second polarity is applied. 5. The method of claim 4,
Wherein the first switch unit and the second switch unit are respectively composed of a 2-1 common voltage source, a reference second common voltage source having a reference voltage level, and three switches connected to the 2-2 common voltage source. Device. 6. The method of claim 5,
The second-1 common voltage source changes in a direction in which the level of the voltage increases to compensate for the voltage drop of the pixel electrode in response to the application of a positive (+) polarity data voltage to the pixel electrode of the pixels ,
The second -2 common voltage source changes in a direction in which the level of the voltage decreases in order to compensate for the voltage drop of the pixel electrode in response to the application of the data voltage of negative polarity to the pixel electrode of the pixels Wherein the liquid crystal display device is a liquid crystal display device. 6. The method of claim 5,
Wherein the first switch unit comprises:
A 1a switch connecting a second common voltage electrode of a pixel to which the data signal of the first polarity is applied by the 1a control signal to a 2-2 common voltage source;
A first b switch for connecting the second common voltage electrode of the pixels to which the data signal of the first polarity is applied by the first control signal to the reference second common voltage source;
And a first c switch for connecting the second common voltage electrode of the pixels to which the data signal of the first polarity is applied by the first control signal to the second-1 common voltage source. 6. The method of claim 5,
Wherein the second switch unit comprises:
An 2a switch connecting a second common voltage electrode of the pixels to which the data signal of the second polarity is applied by the 2a control signal to the 2-2 common voltage source;
A second switch for connecting the second common voltage electrode of the pixels to which the data signal of the second polarity is applied by the second control signal to the reference second common voltage source;
And a second c switch for connecting the second common voltage electrode of the pixels to which the data signal of the second polarity is applied by the second control signal to the second-1 common voltage source. The method according to claim 1,
Wherein the compensation controller controls the storage capacitor of each of the plurality of pixels to store a voltage level corresponding to the video data of the current frame when the video data is changed. 10. The method of claim 9,
Wherein the compensation controller controls the reference second common voltage to be applied to the storage capacitor during a frame period in which the video data is changed. 11. The method of claim 10,
Wherein the compensation controller controls the second common voltage corresponding to the inversion driving to be applied in a period of displaying the still image to display the still image based on the changed image data. 12. The method of claim 11,
And a second common voltage corresponding to the inversion driving,
A second-1 common voltage that changes in a direction in which the level of the voltage increases in order to compensate for the voltage drop of the pixel electrode, or a second-2 common voltage that changes in a direction in which the voltage level decreases to compensate for the voltage drop of the pixel electrode. And a voltage is applied to the liquid crystal layer. A method of driving a liquid crystal display (LCD) device including a plurality of pixels, each pixel including a storage capacitor connected between a pixel electrode and a second common voltage electrode,
Determining whether image data of a current frame has changed from image data of a previous frame;
Storing a voltage level corresponding to image data of a current frame in a storage capacitor of each of the plurality of pixels when the image data is changed; And
And changing a level of a second common voltage applied to the second common voltage electrode of each of the plurality of pixels when the image data is not changed,
And a reference second common voltage is applied to the storage capacitor during a frame period in which the image data is changed. 14. The method of claim 13,
Further comprising the step of displaying a new still image based on the changed image data. 15. The method of claim 14,
And a second common voltage corresponding to the inversion driving is applied in a period in which the new still image is displayed. 16. The method of claim 15,
And a second common voltage corresponding to the inversion driving,
A second-1 common voltage that changes in a direction in which the level of the voltage increases in order to compensate for the voltage drop of the pixel electrode, or a second-2 common voltage that changes in a direction in which the voltage level decreases to compensate for the voltage drop of the pixel electrode. And a voltage of the liquid crystal display device. 14. The method of claim 13,
Wherein when the image data is not changed, the image data of the current frame is not written to the pixel electrodes of the plurality of pixels. 14. The method of claim 13,
Wherein the step of changing the level of the second common voltage changes the level of the second common voltage so as to compensate the voltage drop of the pixel electrode of each of the plurality of pixels.
KR20130102291A 2013-08-28 2013-08-28 Liquid Crystal Display and driving method the same KR20150025104A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106292016A (en) * 2015-05-29 2017-01-04 鸿富锦精密工业（深圳）有限公司 Display device
CN109036315A (en) * 2018-09-06 2018-12-18 京东方科技集团股份有限公司 Driving method, driving device and the display equipment of display panel
US10540939B2 (en) 2016-05-24 2020-01-21 Samsung Display Co., Ltd. Display apparatus and a method of driving the same

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106292016A (en) * 2015-05-29 2017-01-04 鸿富锦精密工业（深圳）有限公司 Display device
CN106292016B (en) * 2015-05-29 2019-08-13 鸿富锦精密工业（深圳）有限公司 Display device
US10540939B2 (en) 2016-05-24 2020-01-21 Samsung Display Co., Ltd. Display apparatus and a method of driving the same
CN109036315A (en) * 2018-09-06 2018-12-18 京东方科技集团股份有限公司 Driving method, driving device and the display equipment of display panel

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