KR100568599B1 - Method and apparatus for driving electro-luminescence display device - Google Patents

Abstract

The present invention relates to a driving device of an electro luminescence display element capable of preventing horizontal crosstalk and a driving method thereof.

The method of driving the electro luminescence display device may include determining a gray level of data input from the outside; Converting a gray level if the gray level is greater than a first threshold or less than a second threshold; And implementing an image by using the data in which the gray level is converted.

Description

TECHNICAL AND APPARATUS FOR DRIVING ELECTRO-LUMINESCENCE DISPLAY DEVICE}             

1 is a cross-sectional view schematically showing a conventional organic electroluminescent cell.

Fig. 2 is a plan view showing a passivated organic electroluminescent display element and its driving apparatus.

3 is a waveform diagram illustrating a driving signal of the organic electroluminescent display device illustrated in FIG. 2.

4 is a diagram illustrating a specific pattern including a window causing horizontal crosstalk in a conventional organic electroluminescent panel.

5 is a block diagram illustrating a driving apparatus of an electro luminescence display device according to an exemplary embodiment of the present invention.

6 is a flowchart illustrating a method of driving the electro luminescence display device illustrated in FIG. 5.

<Description of Symbols for Main Parts of Drawings>

1 substrate 2 anode

3: hole injection layer 4: light emitting layer

5: cathode 20: organic EL cell

100: graphics memory 102: timing control unit

104: mode discrimination unit 106: level converting unit

108: driving circuit section 110: EL panel

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent display element, and more particularly, to a driving apparatus for an electroluminescent display element capable of preventing horizontal crosstalk and a driving method thereof.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. Flat display devices include Liquid Crystal Display (LCD), Field Emission Display (FED), Plasma Display Panel (PDP) and Electro-luminescence (EL). Display elements;

PDP is most advantageous for large screens because of its relatively simple structure and manufacturing process, but it has the disadvantages of low luminous efficiency, low luminance and high power consumption.

As LCDs are mainly used as display elements in notebook computers, demand is increasing. However, since LCD is manufactured by a semiconductor process, it is difficult to make a large screen and it is not a self-emitting device, so a separate light source is required and power consumption is large due to the light source. In addition, LCD has a disadvantage of high light loss and a narrow viewing angle due to optical elements such as a polarizing filter, a prism sheet, and a diffusion plate.

EL display devices are classified into inorganic ELs and organic ELs, and have advantages of fast response speed and high luminous efficiency, luminance, and viewing angle. The organic EL display element is attracting attention as a next generation display element because it can display an image with a high luminance of tens of thousands [cd / m 2] with a voltage around 10 [V].

The organic EL cell forms an anode 2 made of a transparent conductive material on the glass substrate 1 as shown in FIG. 1, on which the hole injection layer 3, the light emitting layer 4 made of organic material, and a low work function are formed. A cathode 5 made of metal is stacked. When an electric field is applied between the anode 2 and the cathode 5, the holes in the hole injection layer 3 and the electrons in the metal proceed toward the light emitting layer 4, respectively, and are combined in the light emitting layer 4. Then, the fluorescent material in the light emitting layer 4 is excited and transitions to generate visible light. At this time, the luminance becomes proportional to the current between the anode 2 and the cathode 5.

FIG. 2 is a diagram illustrating an organic EL display element having a plurality of organic EL cells shown in FIG. 1.

In the organic EL display device illustrated in FIG. 2, a constant current source 21 for supplying current to the data lines DL1 to DLm, and a scan voltage Vhigh and a base voltage at each of the scan lines SL1 to SLn, respectively. Switch elements 22 for supplying GND).

m × n organic EL cells 20 are formed at intersections of the m data lines DL1 to DLm and the n scan lines SL1 to SLn.

The data lines DL1 to DLm are connected to the anode of the organic EL cell 20 to supply the constant current from the constant current source 21 to the anode of the organic EL cell 20. The scan lines SL1 to SLn are connected to the cathode of the organic EL cell 20 and are connected to the scan voltage source Vhigh and the base voltage source GND via the switch elements 22 to switch elements 22. The scan voltage Vhigh and the ground voltage GND from are supplied to the cathode of the organic EL cell 20.

The constant current source 21 is generally implemented as a current mirror including two or more switch elements and a current source.

The switch elements 22 connected to the ground voltage source GND sequentially supply the scan pulses of the ground voltage GND to the scan lines SL1 to SLn to provide the scan lines SL1 to SLn in which data is displayed. Choose. The switch elements 23 connected to the scan high voltage source Vhigh supply the scan high voltage Vhigh to the scan lines SL1 to SLn to the scan lines SL1 to SLn.

The scan pulse SCAN of the base voltage GN is applied to the cathode of the organic EL cell 20 as the forward voltage of the organic EL cell 20 to the scan lines SL1 to SLn as shown in FIG. The data pulse DATA is applied to the data lines DL1 to DLm with a positive constant current in synchronization with the scan pulse SCAN. As such, the organic EL cell 18, in which the ground voltage GND is supplied to the cathode 15 and a constant current is supplied to the anode 12, emits light while a forward current ion flows from the anode 12 to the cathode 15. Done.

On the other hand, while the reverse voltage is applied to the organic EL cell 18 supplied with the scan high voltage Vhigh to the cathode 15, the reverse current flowing from the cathode 15 to the anode 12 does not emit light.

4 is a diagram showing a specific pattern including a window that causes horizontal crosstalk in a conventional organic EL panel.

As shown in FIG. 4, a window BW implementing black gray is displayed on a specific area of the screen implementing white gray on the organic EL panel. That is, EL cells located in the window area BW display the same gray, and EL cells located in the remaining area except the window area BW display the same gray.

On the other hand, the voltage drop of the data pulse DATA supplied to the data line DL connected to the EL cells not displaying the window region BW is relatively small, while the EL cells displaying the window region BW are connected. The voltage drop of the data pulse DATA supplied to the data line DL is relatively large. In this case, since the current from all the EL cells passes through the scan line SL, a voltage difference occurs along the scan line SL when integrating the current from the EL cell in the scan line SL. In particular, a voltage difference occurs along the scan lines SL located in the T2 section including the window area BW and the scan lines SL located in the T1 section not including the window area BW. As a result, the EL cells driven in the T2 section including the window region BW appear to have a horizontal crosstalk that appears relatively brighter than the EL cells driven in the T1 section not including the window region BW. do.

Accordingly, it is an object of the present invention to provide a driving device of an EL display element and a driving method thereof which can prevent horizontal crosstalk.

In order to achieve the above object, a method of driving an electro luminescence display device according to an embodiment of the present invention comprises the steps of determining the gray level of data input from the outside; Converting a gray level if the gray level is greater than a first threshold or less than a second threshold; And implementing an image by using the data in which the gray level is converted.

Implementing the image using the gray level converted data may include implementing a black window on a full white background using the gray level converted data.

When the gray level is larger than the first threshold or smaller than the second threshold, converting the gray level may include converting the gray level of the white data larger than the first threshold to a level less than or equal to the first threshold. It is characterized by including.

Implementing an image using the gray level converted data may include implementing a white window on a full black background using the gray level converted data.

When the gray level is larger than the first threshold or smaller than the second threshold, converting the gray level may include converting the gray level of the black data smaller than the second threshold to a level higher than or equal to the second threshold. It is characterized by including.

In order to achieve the above object, a driving apparatus of an electroluminescence display device according to an embodiment of the present invention includes a mode determination unit for determining the gray level of the data input from the outside to generate the first and second mode signals; A level converter for converting gray levels of data input from the outside in response to any one of the first and second mode signals; And an electro luminescence display device for realizing an image using the gray level converted data.

The mode determining unit may include generating the first mode signal when the gray level is greater than the first threshold value or less than the second threshold value, and generating the second mode signal when the gray level is other than the first threshold value.

The driving device of the electro luminescence display element is a timing for supplying the data to the level converting unit in response to the first mode signal and for supplying data input from the outside to the driving circuit unit in response to the second mode signal. A control unit is further provided.

The electro luminescence display device may implement a black window on a full white background or a white window on a full black background.

The level converting unit converts a gray level of the white data whose gray level of the data is greater than a first threshold to a value less than or equal to a first threshold in response to the first mode control signal, and wherein the gray level is smaller than a second threshold. And converts the gray levels of to more than the second threshold.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 5 and 6.

5 is a block diagram showing a driving apparatus of an organic EL display element according to the present invention.

Referring to Fig. 5, the driving apparatus of the organic EL display element according to the present invention is for controlling the EL panel 110, the driving circuit portion 108 for driving the EL panel 110, and the driving circuit portion 108 for controlling the EL circuit 110. The timing controller 102, the graphics memory 100 for supplying the digital video data Data and the synchronization signals H and V to the timing controller 102, and the digital video data Data from the graphics memory 100. And a mode determining unit 104 for determining a mode corresponding to the above, and a level converting unit 106 for limiting the level of pixel data of a specific gray level.

The graphic memory 100 converts an analog input video signal into digital video data and detects a synchronization signal included in the video signal.

The mode determining unit 104 detects the maximum value (lowest value) of the gray levels of the red, green, and blue digital video data from the graphics memory 100 to generate the first and second mode signals M1 and M2. do. That is, when the digital video data input from the graphics memory 100 includes the digital video data having the highest level gray level or the digital video data having the lowest level gray level, the first mode signal M1 is supplied to the timing controller 102. Otherwise, the second mode signal M2 is supplied to the timing controller 102. Here, the case where the maximum level grayscale data is implemented is a case where a black window is implemented on a full white background, and when the case where the minimum level grayscale data is included is a case where a white window is implemented on a full black background.

The timing controller 102 generates the control signal CS including the scan control signal and the data control signal by using the synchronization signals H and V from the graphic memory 100 to control the driving circuit unit 108. do. In addition, the timing controller 102 rearranges data from the graphics memory 100 according to the mode signals M1 and M2 supplied from the mode determination unit 104 to the driving circuit unit 108 or the level converting unit 106. Supply. That is, the timing controller 102 supplies data to the level converter 106 in response to the first mode signal M1 from the mode determiner 104, and responds to the second mode signal M2 from the mode determiner 104. Data is sorted and supplied to the driving circuit unit 108.

The level converting unit 106 lowers the gray level value below the first threshold value when the data of the maximum level gray level included in the data from the timing controller 102 is equal to or greater than the first threshold value. Alternatively, when the data of the lowest level gray level included in the data from the timing controller 102 is less than or equal to the second threshold value, the data of the lowest level gray level is raised above the second threshold value. That is, when the black window is implemented on the full white background, the grayscale value is lowered below the first threshold for white data having a gray level greater than or equal to the first threshold, and when the white window is implemented on the full black background, The grayscale value is raised to black data having a gray level above the second threshold. In this way, the data converted by the level converting section 106 is supplied to the driving circuit section 108.

The driving circuit unit 108 includes a scan driving circuit unit and a data driving circuit unit. The scan driving circuit unit sequentially supplies the negative scan pulses to the plurality of scan lines SL in line order. The data driving circuit unit converts the digital data signal input from the outside into an analog data signal using the reference gamma voltage from the gamma voltage generator. The data driving circuit unit supplies an analog data signal to the data lines DL every time a scan pulse is supplied.

The EL panel 110 is provided with a plurality of EL cells 20 as shown in FIG. Each of the EL cells 20 is selected when a scan pulse is applied to the scan line SL, which is a cathode, to generate light corresponding to a pixel signal, that is, a current signal, which is supplied to the data line DL, which is an anode. Each of the EL cells 20 is represented by a diode equivalently connected between the data line DL and the scan line SL. As shown in FIG. 3, each of the EL cells is supplied with a negative scan pulse SCAN to the scan line SL and a positive current corresponding to the data signal DATA is applied to the data line DL in a forward direction. When voltage is applied, it emits light. In contrast, the reverse direction voltage is applied to the EL cells 20 included in the scan line SL which is not selected so that the EL cells 20 do not emit light. In other words, forward light is charged in the EL cells 20 that emit light, whereas reverse charge is charged in the EL cells 20 that do not emit light.

6 is a flowchart showing a method of driving the organic EL display device shown in FIG.

As shown in FIG. 6, the graphic memory converts the input analog input video signal into digital video data and supplies it to the mode discrimination unit (step S11). It is determined whether or not the threshold of the gray level included in the digital video data inputted to the mode discrimination unit is [less than or equal to] (step S12). If the gray level of the digital video data is below the minimum threshold or above the maximum threshold, the first mode signal is supplied to the timing controller. The timing controller supplies the digital video data and the first mode signal to the level converter. The level converting unit converts the gray level of the digital video data in response to the second mode signal and supplies it to the driving circuit unit (steps S13 and S14). On the other hand, the second mode signal is supplied to the timing controller when the gray level of the digital video data is lower than or equal to or below the minimum threshold. The timing controller supplies digital video data to the driver circuit in response to the second mode signal (step S14).

As described above, the EL display device driving apparatus and the driving method thereof according to the present invention adjust the gray level of the white data so as not to exceed the threshold when implementing the black pattern on the full white background, and adjust the white pattern on the full black background. The implementation adjusts the gray level of the black data beyond the threshold. Accordingly, horizontal crosstalk can be prevented by reducing the variation in luminance by controlling the current amount between the lines in the same manner.                     

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (10)

Determining a gray level of data input from the outside; Converting a gray level if the gray level is greater than a first threshold or less than a second threshold; And implementing an image by using the data in which the gray level is converted. The method of claim 1, Implementing an image using the data whose gray level is converted is And implementing a black window on a full white background using the gray level-converted data. The method of claim 2, Converting the gray level when the gray level is greater than the first threshold or less than the second threshold And converting a gray level of the white data larger than the first threshold to be less than or equal to the first threshold by a level converting unit. The method of claim 1, Implementing an image using the data whose gray level is converted is And implementing a white window on a full black background using the gray level-converted data. The method of claim 4, wherein Converting the gray level when the gray level is greater than the first threshold or less than the second threshold And converting a gray level of the black data smaller than the second threshold value by a level converting portion to a value greater than or equal to the second threshold value. A mode determination unit configured to determine a gray level of data input from the outside and generate first and second mode signals; A level converter for converting gray levels of data input from the outside in response to any one of the first and second mode signals; And an electro luminescence display element for realizing an image using the gray level converted data. The method of claim 6, The mode determination unit Generating the first mode signal when the gray level is greater than the first threshold or less than the second threshold, and otherwise generating the second mode signal. Device driving device. The method of claim 7, wherein And a timing controller for supplying the data to the level converter in response to the first mode signal and for supplying data input from the outside to the driver circuit in response to the second mode signal. Driving device of luminescence display element. The method of claim 8, The electro luminescence display device may include a black window on a full white background or a white window on a full black background. The method of claim 9, The level converter In response to the first mode control signal, the gray level of the white data in which the gray level of the data is greater than the first threshold value is converted to the first threshold value or less, and the gray level of the black data in which the gray level is smaller than the second threshold value is set. A drive device for an electro luminescence display device, characterized in that the conversion is greater than or equal to a second threshold.

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