KR102210870B1 - Display device and method for driving thereof - Google Patents

Abstract

In the present invention, a display panel in which pixels are arranged, a data driver supplying a data voltage to each pixel, and a first area in which the gray level of the input data exceeds the reference gray level and the gray level of the input data are less than the reference gray level when the image is a still image. And a timing controller that converts input data of each pixel into output data so that the pixels of the first area lower the gray level of the data and increase the gray level of the pixels of the second area. It relates to the driving method.

Description

Display device and its driving method {DISPLAY DEVICE AND METHOD FOR DRIVING THEREOF}

The present invention relates to a display device that displays an image.

As the information society develops, the demand for display devices for displaying images is increasing in various forms. Recently, liquid crystal display devices (LCDs), plasma display panels (PDPs), organic Various display devices such as an OLED (Organic Light Emitting Display Device) are being used.

When an image is output from a display device, a screen protection technology that reduces the brightness of the screen is used to protect the display device. When a still image lasts for a certain period of time or longer, a screen protection technology is used to improve the level of device degradation and afterimage. However, the existing screen protection technology has a low level of improving the level of device deterioration and afterimage.

An object of the present invention is to improve the level of device deterioration and afterimage by reducing the deviation of bright and dark areas of a display image when a still image is output in a display device.

An object of the present invention is to improve the image quality and lifespan of the display device by reducing the deviation between bright and dark areas of a display image when a still image is output in a display device.

In one aspect, the present invention provides a display panel in which pixels are arranged, a data driver supplying a data voltage to each pixel, and a first region in which the grayscale of the input data exceeds the reference grayscale and the grayscale of the input data when the image is a still image. Display including a timing controller that divides the data into a second area below the reference gray level and converts the input data of each pixel into output data so that the pixels in the first area lower the gray level of the data and increase the gray level of the pixels in the second area Provide the device.

In another aspect, the present invention is a driving method of a display device including a display panel, a data driver, and a timing controller, the step of determining whether an image is a still image, a first region in which a gray level of the input data exceeds a reference gray level, and an input The step of dividing the gray level of data into a second area below the reference gray level, and converting the input data of each pixel into output data so that the pixels in the first area lower the gray level of the data and increase the gray level of the pixels in the second area. It provides a method of driving a display device including steps.

As described above, according to the present invention, when a still image is output, it is possible to improve the level of device deterioration and afterimage by reducing the deviation of the bright and dark regions of the display image.

In addition, in a display device, when a still image is output, there is an effect of improving the image quality and lifespan of the display device by reducing the deviation of the bright and dark areas of the display image.

1 is a configuration diagram of a display device according to exemplary embodiments.
2 is a partial block diagram of a display device according to an exemplary embodiment.
3 shows the concept of lowering the luminance of the first region of the still image and increasing the luminance of the second region.
4 is an equivalent circuit diagram of each subpixel included in a pixel when the display device is an organic light emitting display (OLED).
5 shows a change in luminance of an organic light-emitting diode (OLED) while changing the gradation of the driving data voltage Vdata applied to the N1 node through the data line DL, for example, from 0 to 255 gradations (total 256 gradations). Is the result of measuring.
6 shows a reference gradation positioned between low and high luminance.
7 is a partial configuration diagram of a display device according to another exemplary embodiment.
FIG. 8 illustrates a concept of dividing a first region and a second region of a still image of a display panel, lowering the luminance of the first region, and increasing the luminance of the second region.
9 illustrates sections in which luminance of a first region and a second region are adjusted during a time while a still image is maintained in a display device according to another exemplary embodiment.
10 illustrates a concept of adjusting the luminance of a first region and a second region for each section during a time while a still image is maintained in a display device according to another exemplary embodiment.
FIG. 11 illustrates dividing the display panel into first regions and second regions, as well as third regions with intermediate luminance lower than the luminance of the first region and higher than the luminance of the second region.
12 is a flowchart of a method of driving a display device according to another exemplary embodiment.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. In adding reference numerals to elements of each drawing, the same elements may have the same numerals as possible even if they are indicated on different drawings. In addition, in describing the present invention, when it is determined that a detailed description of a related known configuration or function may obscure the subject matter of the present invention, a detailed description thereof may be omitted.

In addition, in describing the constituent elements of the present invention, terms such as first, second, A, B, (a), (b) may be used. These terms are only for distinguishing the component from other components, and the nature, order, order, or number of the component is not limited by the term. When a component is described as being "connected", "coupled" or "connected" to another component, the component may be directly connected or connected to that other component, but other components between each component It is to be understood that is "interposed", or that each component may be "connected", "coupled" or "connected" through other components.

1 is a configuration diagram of a display device according to exemplary embodiments.

Referring to FIG. 1, a display device 100 according to the present exemplary embodiments includes a display panel 110, a data driver 120, a gate driver 130, a timing controller 140, and the like.

On the display panel 110, a plurality of data lines (DL) are disposed in a first direction, a plurality of gate lines (GL) are disposed in a second direction crossing the first direction, and The pixels of are arranged in a matrix type. The data driver 120 drives data lines by supplying data voltages to the data lines. The gate driver 130 sequentially drives the gate lines by sequentially supplying scan signals to the gate lines. The timing controller 140 supplies control signals to the data driver 120 and the gate driver 130 to control the data driver 120 and the gate driver 130.

The timing controller 140 starts scanning according to the timing implemented in each frame, converts the image data input from the host system according to the data signal format used by the data driver 120 to convert the converted image data. (Data') is output, and data drive is controlled at an appropriate time according to the scan.

The gate driver 130 sequentially drives the gate lines by sequentially supplying scan signals of an on voltage or an off voltage to the gate lines under the control of the timing controller 140.

When a specific gate line is opened, the data driver 120 converts the data'Data' received from the timing controller 140 into an analog data voltage Vdata and supplies it to the data lines, thereby driving the data lines. .

The display device 100 may further include a power controller 150 that supplies various voltages or currents to the display panel 110, the data driver 120, the gate driver 130, or controls various voltages or currents to be supplied. I can. The power controller 150 is also referred to as a power management integrated circuit (PMIC).

The display device 100 briefly illustrated in FIG. 1 is, for example, a liquid crystal display device (LCD), a plasma display device, and an organic light emitting display device (OLED). ), etc.

As described above, when an image persists for a predetermined time or longer in the display device 100, the existing screen protection technology has a low level of improving the level of device deterioration and afterimage.

Hereinafter, when a still image is output, embodiments of improving the level of device deterioration and afterimage by reducing the deviation between bright and dark regions of the display image will be described.

2 is a partial block diagram of a display device according to an exemplary embodiment. 3 illustrates the concept of lowering the luminance of the first region of the still image and increasing the luminance of the second region.

1 and 2, the display device 200 according to an exemplary embodiment includes a timing controller 240, a data driver 220, and a display panel 210. Same as (100).

2 and 3, the display device 200 according to an embodiment lowers the luminance of a high luminance area (hereinafter referred to as a'first area') when a still image is continued, and a low luminance area including black ( Hereinafter, the luminance of the'second area') may be increased, thereby improving the deviation of the bright and dark areas of the display image.

At this time, the timing controller 240 lowers the gray level of the input data Data of the pixels of the first region to lower the luminance of the high luminance first region, and inputs the pixels of the second region to increase the luminance of the low luminance second region. The input data Data of each pixel is converted into output data Data' to increase the gray level of the data Data. At this time, the gray level of each pixel indicates an ability to display an intermediate brightness level between the minimum and cancel brightness, or an intermediate brightness state other than the pixel's on/off.

The timing controller 240 gradually lowers the gradation of the input data Data of the pixels in the first region as shown in FIG. 3 and maintains the same, and increases the luminance of the low luminance second region. The input data Data of each pixel may be converted into output data Data' so that the gray level of the input data Data of the pixels is gradually increased and maintained the same. At this time, gradually increasing or lowering the luminance of the region is not only increasing or lowering the luminance of the region linearly as shown in FIG. 3, but also increasing or decreasing the luminance of the region exponentially. Can be lowered.

At this time, the level of increasing or decreasing the luminance by adjusting the gray level of the input data Data of the pixels in each area may be a level that the user cannot experience, but the present invention is not limited thereto. In general, when the image is a still image, the user uses the display device 200 in many cases, so the level of increasing or decreasing the luminance by adjusting the gradation of the input data of the pixels in each area can be felt by the user. Even if it is at the level that there is, it is okay.

The data driver 220 receives data' of pixels in the first region and the second region from the timing controller 240, converts it into a data voltage Vdata, and supplies it to the pixels of the display panel 210. .

Meanwhile, when a pixel includes two or more subpixels, the timing controller 240 lowers the gray level of the input data Data of the first area and increases the gray level of the input data Data of the second area. To maintain the same color coordinate, the gray scale of each data of subpixels included in the pixel may be appropriately converted.

The gray level of the input data of the first area for lowering the luminance may exceed a reference gray, and the gray level of the input data of the second area for increasing the luminance may be less than or equal to the reference gray level. In other words, when the average gray level of the first area exceeds the reference gray level and the average gray level of the second area is less than the reference gray level, the timing controller 240 lowers the gray level of the input data Data of the first area and input data of the second area. Increase the gradation of (Data).

4 is an equivalent circuit diagram of each subpixel included in a pixel when the display device is an organic light emitting display (OLED).

Referring to FIG. 4, when the display device 200 is an organic light emitting display device (OLED), each subpixel included in the pixel is basically an organic light emitting diode (OLED). And, it includes a driving transistor (DRT) for driving the organic light-emitting diode (OLED) by supplying current to the organic light-emitting diode (OLED).

The first node N1 of the driving transistor DRT is a gate node and is applied with a data voltage Vdata. A storage capacitor (Cst) connected between nodes N1 and N2 of the driving transistor DRT may be included. The storage capacitor Cst maintains a certain data voltage Vdata for one frame.

At this time, an afterimage may occur due to a Vth shift gap for each region due to a bias stress of the driving transistor DRT.

Hereinafter, the organic light emitting display device described with reference to FIG. 4 will be described as an example of a reference gray that lowers the luminance of the first region and increases the luminance of the second region.

5 is a change in luminance of an organic light emitting diode (OLED) while changing the gray level of the driving data voltage Vdata applied to the N1 node through the data line DL, for example, from 0 to 255 grays (total 256 grays) Is the result of measuring. 6 shows a reference gradation positioned between low and high luminance.

Referring to FIG. 5, looking at the luminance change amount of the organic light-emitting diode (OLED) for each gradation of the data voltage, when the luminance change amount of the organic light-emitting diode (OLED) exceeds 32 gradations of the driving data voltage Vdata in a total of 256 gradations, the driving data voltage It can be seen that the amount of change in luminance of the organic light emitting diode (OLED) is large when the gray scale of (Vdata) is less than 32. Accordingly, even if the driving data voltage Vdata is lowered when the driving data voltage Vdata exceeds 32 gray scales, the difference in the luminance change amount of the organic light emitting diode OLED is not large, so that the effect of improving the afterimage level may not be significant. On the other hand, if the data voltage is increased below 32 gradations where the luminance change amount of the organic light emitting diode (OLED) is large, the effect of improving the afterimage level can be large.

Referring to FIG. 5, a reference gray for lowering the luminance of the first region and increasing the luminance of the second region has been exemplarily described from 256 to 32 gradations, but as shown in FIG. 6, the reference gradation is displayed. Any gradation between low and high luminance may be used depending on the implementation method of the panel 210 or the like. In other words, the reference gradation may be any gradation between low and high luminance that can serve as a reference for improving the deviation of the bright and dark areas of the display image. For example, the reference grayscale may be from 1024 to 128 grayscales in total.

7 is a partial configuration diagram of a display device according to another exemplary embodiment. FIG. 8 illustrates a concept of dividing a first region and a second region of a still image of the display panel, lowering the luminance of the first region, and increasing the luminance of the second region. 9 illustrates dividing the display panel into two or more first regions and second regions according to a reference gray scale.

Referring to FIG. 7, a display device 700 according to another exemplary embodiment includes a timing controller 740, a data driver 720, and a display panel 710 according to the exemplary embodiment described with reference to FIG. 2. It is the same as the display device 200. The display device 700 according to another exemplary embodiment may additionally include a memory 760.

7 and 8, the timing controller 740 continuously maintains input data of pixels of at least two frames stored in a memory 760, for example, a frame buffer by a predetermined number. By comparing with, it is determined whether the image to be displayed on the display panel 710 is a still image.

For example, when input data of pixels of an nth frame and input data of pixels of an (n+1)th frame are stored in the frame memory 760, the The input data of the pixels are compared to check whether they are the same, and the input data of the pixels are the same in a reference number of frames or more, for example, 120 frames by comparing two adjacent frames continuously. If so, it can be judged as a still image.

In this case, when determining the input image as a still image, the timing controller 740 may divide the display panel 710 into two or more first regions and second regions according to the reference gray scale as illustrated in FIG. 8. The timing controller 740 lowers the gray level of the input data Data of the pixels corresponding to the first regions to lower the luminance of the first regions, and inputs the pixels corresponding to the second region to increase the luminance of the second region. The input data Data of each pixel is converted into output data Data' to increase the gray level of the data Data. In other words, the display device 100 according to an exemplary embodiment may divide the same regions into first regions and second regions exhibiting high and low luminance, and may individually adjust the luminance of the first regions and the second regions. .

In FIG. 9, it is shown that the edges of the first region and the second region are rectangular and that the first region and the second region are regularly arranged. The edges of the first region and the second region may have various shapes or have no specific shape, and the first region and the second region may be irregularly arranged.

The timing controller 740 gradually lowers the gray level of the input data Data of the pixels in the first area and maintains the same level as shown in FIG. 8. In order to increase the brightness of the low-luminance second area, the The input data Data of each pixel may be converted into output data Data' so that the gray level of the input data Data of the pixels is gradually increased and maintained the same.

Meanwhile, when a pixel includes two or more subpixels, the timing controller 740 lowers the gray level of the input data Data in the first area and increases the gray level of the input data Data in the second area. To maintain the same color coordinate, the gray scale of each data of subpixels included in the pixel may be appropriately converted.

When the timing controller 740 converts the input data of pixels in the first region and the second region into output data Data', the timing controller 740 converts the input data according to each gray level into output data Data'. The lookup table stored in the memory 760 may be used to do so.

The data driver 720 receives data' of pixels in the first and second regions from the timing controller 740, converts the data into a data voltage Vdata, and supplies them to the pixels of the display panel 710. .

9 illustrates sections for adjusting luminance of a first region and a second region during a time while a still image is maintained in a display device according to another exemplary embodiment. 10 illustrates a concept of adjusting the luminance of a first region and a second region for each section during a time while a still image is maintained in a display device according to another exemplary embodiment.

As shown in FIG. 9, in the display device according to another embodiment, the periods for adjusting the luminance of the first area and the second area are maintained during the period during which the still image is maintained, the pause period T1 and the luminance adjustment period T2. It can be divided into a section (T3) and a return section (T4). This is to improve the effect of improving device deterioration and afterimage while allowing the user to experience less or less of the image switching.

As illustrated in FIG. 10, the timing controller 740 may adjust the luminance of the first region and the second region for each section during the time that the still image is maintained.

When it is determined as a still image, the timing controller 740 does not convert the input data (Data) of the pixels in the first region and the second region into output data (Data') and maintains the same luminance during the idle period (T1). The input data Data of the pixels in the first region and the second region may be kept the same.

Next, the timing controller 740 gradually lowers the gray level of the input data Data of the pixels in the first region to the first sustained luminance during the luminance adjustment period T2, and decreases the input data Data of the pixels in the second region. The input data Data of each pixel may be converted into output data Data' so as to gradually increase the gradation to the second sustained luminance. This luminance control section is a section in which a video is converted from a moving image to a still image, and the image can be naturally switched so that the user cannot experience the transition of the image or less, without immediately switching to the maintenance luminance.

At this time, the first maintained luminance may be higher than the second maintained luminance, but the present invention is not limited thereto, and the first maintained luminance may be the same as the second maintained luminance. The first sustained luminance may be a luminance obtained by lowering the luminance according to the grayscale of the input data of the pixels in the first area by a predetermined first ratio. In addition, the second sustained luminance is a luminance obtained by lowering the luminance according to the gray level of the input data of the pixels in the second area to a predetermined second ratio. In this case, the first ratio and the second ratio may be the same. However, the first ratio may be larger than the second ratio, and the second ratio may be larger than the first ratio. Meanwhile, the first sustained luminance is equal to or greater than the luminance corresponding to the reference gradation. In addition, the second sustained luminance may be equal to or smaller than the luminance corresponding to the reference gray scale.

Next, the timing controller 740 may convert the input data Data of each pixel in the first region and the second region into output data Data' so as to maintain the luminance at a constant luminance during the sustain period T3. The timing controller 740 may convert input data Data of each pixel of the first region into output data Data' so as to maintain the luminance at the first sustained luminance during the sustain period T3. The timing controller 740 may convert input data Data of each pixel of the second region into output data Data' so as to maintain the luminance at the second sustained luminance during the sustain period T3.

Next, the timing controller 740 raises to return to the same gray level as the input data Data of the pixels in the first area during the return period T4, and returns the same gray level as the input data Data of the pixels in the second area. The input data Data of each pixel may be converted into output data Data' so as to be lowered. At this time, the slope (luminance change amount) for converting input data (Data) to output data (Data') in the return section (T4) is to convert input data (Data) to output data (Data') in the luminance control section (T2). It may be larger than the slope (amount of luminance change).

This return section (T4) is a section for converting an image from a still image to a moving image. Instead of immediately returning to the same grayscale as the input data of the pixels in the first region and the second region, the user You can naturally switch the video so that you can not feel the conversion or feel less.

The lookup table stored in the memory 760 has output data (Data') for input data (Data) according to each gray level for each section during the time that the still image shown in FIG. 10 is maintained. When the timing controller 740 converts the input data of the pixels of the first region and the second region into output data Data', the timing controller 740 is A lookup table for converting input data Data into output data Data′ may be stored in the memory 760, and the input data Data may be converted into output data Data′ using the lookup table.

On the other hand, as described with reference to FIG. 8, the timing controller 740 is configured with only the luminance adjustment period T2 and the sustain period T3 without the pause period T1 and the return period T4. The input data Data of each pixel may be converted into output data Data'. In particular, when the difference in grayscale between the first region and the second region is not large, even if there is no pause period T1 and return period T4, the user may not experience the transition of the image or experience less.

FIG. 11 illustrates dividing the display panel into first regions and second regions, as well as third regions with intermediate luminance lower than the luminance of the first region and higher than the luminance of the second region.

The display device 700 according to another exemplary embodiment described with reference to FIGS. 7 to 10 is described as dividing the display panel 710 into two or more first regions and second regions when an image is determined to be a still image. However, in the display device 700 according to another embodiment, as illustrated in FIG. 11, the display panel 710 is lower than the luminance of the first region and the luminance of the second region as well as the first regions and the second regions. It can also be divided into third areas of high medium luminance. In this case, the third area may be an area that is larger than the first reference grayscale and smaller than or equal to the second reference grayscale. Even when the image is determined to be a still image, the timing controller 740 may maintain a constant gray level of the input data Data of the pixels in the third area. For example, if the luminance according to the gradation of the input data of the pixels in the first area is lowered by 50%, but not lower than the luminance according to the reference gradation, for example, 32 gradations, the gradation of the input data corresponding to 63 to 32 gradations If the luminance according to is lowered by 50%, the luminance corresponding to less than 32 gradations is lowered, so an area corresponding to 63 to 32 gradations may be defined as a third region. In this case, the second reference gradation may be, for example, a total of 256 to 64 gradations or a total of 1024 to 128 gradations.

In this case, the timing controller 740 does not lower the gray level of the input data Data of the pixels of the first area to be lower than the gray level of the input data Data of the pixels of the third area, but the input data of the pixels of the second area. The input data Data of each pixel may be converted into output data Data' so that the gray level of) is not higher than the gray level of the input data Data of the pixels in the third area.

12 is a flowchart of a method of driving a display device according to another exemplary embodiment.

Referring to FIGS. 1 and 12, in a method 1200 of driving a display device according to another exemplary embodiment, determining whether an image is a still image (S1210), a first area in which a grayscale of input data exceeds a reference grayscale, and Step of dividing the gray level of the input data into a second area less than the reference gray level (S1220), the input data of each pixel so that the pixels of the first area lower the gray level of the data and increase the gray level of the data of the pixels of the second area. ) To the output data (Data') (S1230).

In determining whether the image is a still image (S1210), when two adjacent frames are compared and input data of pixels are the same in a reference number or more, it may be determined as a still image.

In the step of dividing the first region into the second region (S1220 ), as illustrated in FIG. 8, the first region and the second region may be two or more. In this case, as shown in FIG. 11, it may be further divided into third regions having an intermediate luminance lower than the luminance of the first region and higher than the luminance of the second region. In this case, the gray level of the input data Data of the pixels in the third area may be kept constant.

In the step of converting the input data into output data (S1230), as shown in FIGS. 9 and 10, the gray level of the input data of the pixels in the first area is gradually lowered in the luminance adjustment period T2, and then the sustain period T3. ), the gradation of the input data of the pixels in the second region is gradually increased in the luminance control section (T2), and then the second luminance level is maintained in the sustain section (T3). The input data (Data) of the pixel may be converted into output data (Data').

In the step of converting input data into output data (S1230), input data of pixels in the first area and the second area are converted into output data'Data' in the idle period T1 before the luminance control period T2. It is possible to maintain the same input data Data of the pixels in the first region and the second region without conversion.

At this time, after the maintenance period T3, the return period T4 is increased to return to the same gray level as the input data Data of the pixels in the first area, and gradually returns to the same gray level as the input data Data of the pixels in the second area. The input data Data of each pixel may be converted into output data Data' so as to decrease to.

At this time, as shown in FIG. 7, a lookup table for converting the input data Data according to each gray level into output data Data' during the time the still image is maintained is stored in the memory. At this time, in the step of converting the input data into output data (S1230), the input data Data may be converted into the output data Data' using a lookup table stored in the memory.

Thereafter, the display device 100 drives the data lines by converting the converted output data Data' into an analog data voltage Vdata and supplying them to the data lines. At this time, the display device 100 receives the data'Data' of the pixels in the first area and the second area, converts it into a data voltage Vdata, and supplies the data to the pixels of the display panel 110.

According to the above-described embodiment, the luminance of the first region having high luminance is lowered and the luminance of the second region having low luminance is increased, so that the threshold voltage shift difference (Vth shift) for each region is caused by a bias stress of the driving transistor DRT. gap) can improve the level of afterimages.

According to the embodiments described above, when a still image is output, it is possible to improve the level of device deterioration and afterimage by reducing the deviation of the bright and dark areas of the display image.

According to the above-described embodiments, when a still image is output, it is possible to improve the image quality and lifespan of the display device by reducing the deviation between bright and dark areas of the display image.

The description above and the accompanying drawings are merely illustrative of the technical idea of the present invention, and those of ordinary skill in the technical field to which the present invention pertains, combinations of configurations without departing from the essential characteristics of the present invention Various modifications and variations, such as separation, substitution, and alteration, will be possible. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

100, 200, 700: display device
110, 210, 710: display panel
120, 220, 720: data driver
130: gate driver
140, 240, 740: timing controller
760: memory

Claims (10)

A display panel on which pixels are arranged;
A data driver supplying a data voltage to each pixel; And
If the image is a still image, the first area in which the gray level of the input data exceeds the reference gray level and the second area in which the gray level of the input data is less than the reference gray level are divided, and the gray level of the pixels of the first area is lowered, A timing controller for converting input data of each pixel into output data to increase gray scale of the data of the pixels of the two areas,
The timing controller gradually lowers the gray level of the input data of the pixels of the first area in the luminance control section and maintains the same level as the first luminance in the maintenance section, and inputs the pixels of the second area in the luminance control section. A display device for converting input data of each pixel into output data so that the gray level of data is gradually increased and then the same as the second sustained level in the sustain period. delete The method of claim 1,
The timing controller does not convert the input data of the pixels of the first area and the second area into output data in the idle period before the luminance adjustment period, and makes the input data of the pixels of the first area and the second area the same. Holding display. The method of claim 1,
After the sustain period, the input data of each pixel is gradually increased to return to the same gray level as the input data of the pixels of the first area and gradually lowered to return to the same gray level as the input data of the pixels of the second area in the return period. A display device that converts to output data. The method of claim 3,
The first area and the second area are at least two. The method of claim 1,
The timing controller compares two adjacent frames at a time and determines a still image when input data of the pixels are the same in a reference number or more of frames. The method of claim 1,
The reference gradation is a total of 256 gradations to 32 gradations, and a total of 1024 to 128 gradations. The method of claim 1,
The timing controller divides the third regions into intermediate luminances lower than the luminance of the first region and higher than the luminance of the second region, and maintains a constant gray level of the input data Data of the pixels of the third region. Device. The method of claim 1,
Further comprising a memory for storing a lookup table for converting the input data (Data) according to each gray level to output data (Data') during the still image is maintained,
The timing controller converts the input data into the output data using the lookup table. A method of driving a display device including a display panel, a data driver, and a timing controller,
Determining whether the image is a still image;
Dividing a first area in which the gray level of the input data exceeds a reference gray level and a second area in which the gray level of the input data is less than the reference gray level; And
The gray level of the data of the pixels in the first area is gradually lowered in the luminance control section, and the gray level of the data of the pixels in the second area is gradually lowered in the sustain period. And converting input data of each pixel into output data so as to increase and maintain the same as the second sustained period during the sustain period.

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