KR102274926B1 - Displya device - Google Patents

Abstract

The present invention relates to a threshold of a driving transistor using a display panel in which each pixel includes a light emitting element and a driving transistor for driving the light emitting element, a gate driver for driving gate lines connected to each pixel, and a sensing line connected to each pixel. A data driver that senses a voltage and supplies a data voltage to data lines connected to each pixel, aligns the input image data and supplies the image data to the data driver in response to the threshold voltage of the driving transistor sensed by the data driver A display device including a timing controller for compensating and adjusting a target peak luminance according to an average image level of image data according to a threshold voltage of a driving transistor is provided.

Description

display device {DISPLYA DEVICE}

The present invention relates to a display device for displaying an image.

As the information society develops, the demand for a display device for displaying an image is increasing in various forms, and a liquid crystal display device (LCD), a plasma display device (Plasma Display Device), an organic light emitting display device ( Various types of display devices such as OLED: Organic Light Emitting Display Device) are being used.

For example, each of the plurality of pixels constituting the organic light emitting display device includes an organic light emitting diode (OLED) including an organic light emitting layer between an anode and a cathode, and a driving circuit for driving the OLED. In this case, in a self-luminous display device such as an organic light emitting display device, an organic light emitting diode included in a pixel is deteriorated, thereby reducing the lifespan of the display device. In particular, when each pixel includes two or more sub-pixels, there is a problem in that the lifetime of the display device itself is shortened due to deterioration of one sub-pixel due to deterioration of the sub-pixels.

An object of the present invention to solve the above problems is to provide a display device in which the lifespan of the display device is increased by controlling the data voltages above a specific gray level to minimize the deterioration deviation over time of sub-pixels included in the pixel. .

In order to achieve the above object, a display device according to an exemplary embodiment of the present invention provides a display panel including two or more pixels including two or more sub-pixels, and a display panel that supplies data voltages to data lines connected to each sub-pixel. The data driver aligns the data driver, the gate driver drives gate lines connected to each sub-pixel, and the input image data of each sub-pixel, and the data driver supplies the first image data of one of the two or more sub-pixels at a specific first grayscale or higher. and a timing controller controlling the data voltage of the sub-pixel to be constant.

In this case, the timing controller may increase the data voltage of another second sub-pixel among the two or more sub-pixels to maintain the peak luminance of the pixel including the first sub-pixel.

In addition, the timing controller controls the data voltage of another third sub-pixel among the two or more sub-pixels to be constant at a specific second grayscale or higher, and increases the data voltage of the second sub-pixel to increase the data voltage of the first sub-pixel and the third sub-pixel. It is possible to control to maintain the peak luminance of the pixel including the sub-pixel.

The present invention has the effect of increasing the lifespan of the display device by controlling the data voltages above a specific gray scale in the display device to minimize the deterioration deviation of sub-pixels included in the pixel over time.

1 is a schematic system configuration diagram of a display device 100 according to an embodiment.
2 shows a method of using a white organic light emitting diode (WOLED) and RGB color filters (CFr, CFg, CFb).
FIG. 3 is a diagram exemplarily explaining the setting of each data signal of FIG. 2 .
FIG. 4 shows transmittance of each sub-pixel in the RGBW sub-pixel structure of FIG. 2 .
5 shows a peak luminance curve according to grayscale.
6 shows the concept of an average picture level.
7 is a graph showing a peak luminance control (PLC) function according to an average image level.
8 illustrates deterioration characteristics of each sub-pixel according to time in the RGBW sub-pixel structure.
FIG. 9 shows a color temperature curve according to grayscale and changes in a color temperature curve according to grayscale when the same data voltage is applied after time elapses.
10 is a configuration diagram of a timing controller according to an exemplary embodiment.
11A and 11B are conceptual diagrams of pixel driving according to APL reduction of a timing controller according to an exemplary embodiment.
12A to 12D are diagrams illustrating luminance curves during grayscale expression according to APL reduction of the timing controller according to an exemplary embodiment.
FIG. 13 shows that the color coordinate for white shifts toward yellow when peak luminance is displayed in a small APL. 14 illustrates deterioration characteristics of sub-pixels according to time of a general display panel and a display panel according to an exemplary embodiment.
15 illustrates that the color coordinate movement state is improved even after time has elapsed in the display panel according to an exemplary embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. In adding reference numerals to components of each drawing, the same components may have the same reference numerals as much as possible even though they are indicated in different drawings. In addition, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description may be omitted.

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

1 is a schematic system configuration diagram of a display device 100 according to an embodiment. 2 shows a method of using a white organic light emitting diode (WOLED) and RGB color filters (CFr, CFg, CFb). FIG. 3 is a diagram exemplarily explaining the setting of each data signal of FIG. 2 .

Referring to FIG. 1 , the display device 100 according to the embodiment includes a display panel 110 , a data driver 120 , a gate driver 130 , a timing controller 140 , a memory 150 , and the like.

In the display panel 110 , data lines DL1 , DL2 , ... , DLm and gate lines GL1 , GL2 ... , GLn are formed, and data lines DL1 , DL2 , ... , DLm) and the gate lines GL1 , GL2 ... , GLn are formed at each intersection.

The data driver 120 supplies a data voltage to the data lines DL1, DL2, ..., DLm. The data driver 120 may include two or more data driver integrated circuits (DICs). The data driver 120 converts digital data into data voltages and supplies them to each pixel through each of the data lines DL1, DL2, ..., DLm.

The gate driver 130 sequentially supplies scan signals to the gate lines GL1 , GL2 ... , GLn.

The timing controller 140 controls the data driver 120 and the gate driver 130 . Since the timing controller 140 adjusts the target peak luminance according to the average image level of the image data, power consumption may be reduced.

Meanwhile, a driving circuit including at least one driving transistor is configured in pixels formed in the display panel 110 . Here, the driving circuit in the pixel may further include at least one capacitor, an organic light emitting diode (OLED), etc., in addition to at least one driving transistor, depending on a circuit design method or a type of a display device.

The display panel 110 has a red sub-pixel (SPr), a green sub-pixel (SPg), a blue sub-pixel (SPb), and a white sub-pixel (SPw) (hereinafter referred to as "SPw") in order to prevent deterioration of luminance and color of a pure color while increasing light efficiency. It may be implemented as a sub-pixel structure including RGBW sub-pixels). At this time, the RGBW sub-pixels (SPr, SPg, SPb, SPw) are an organic light emitting diode that emits red, green, blue and white light, or as shown in FIG. 2 , a white organic light emitting diode (WOLED) and RGB color filters (CFr, CFg). , CFb) can be implemented in such a way.

In this case, since the RGB sub-pixels SPr, SPg, and SPb convert white light emitted from the white organic light emitting diode WOLED into red, green, and blue, the RGB color filters CFr, CFg, and CFb are included. In contrast, the W sub-pixel SPw does not include a color filter since the white light emitted from the white organic light emitting diode WOLED is emitted as it is.

The display device 100 described above uses the RGB sub-pixels SPr, SPg, SPb, and SPw to express the desired color coordinates on the display panel 110 in addition to the W sub-pixel SPw and the RGB sub-pixels SPr and SPg. , SPb), some or all of them are compensated for light emission.

For example, as shown in FIG. 3 , the R data signal of the R sub-pixel SPr in the N frame has the lowest luminance value compared to the GB data signal of the GB sub-pixels SPg and SPb, so the luminance value of the R data signal is W It can be replaced with a data signal, and the R data signal can be set to 0. In addition, the luminance of the GB data signal may be lowered based on the R data signal set to 0. As a result, the luminance of the RGB data signal is set to 50, 120, and 80 before data conversion, but is changed to 0, 70, 30, and 50 after data conversion.

FIG. 4 shows transmittance of each sub-pixel in the RGBW sub-pixel structure of FIG. 2 .

Referring to FIG. 4 , a difference in transmittance of each sub-pixel in the RGBW sub-pixel structure of FIG. 2 is shown. Due to the characteristics of the current color filter, the transmittance of the B sub-pixel SPb and the R sub-pixel SPr is 5% or less, but the transmittance of the G sub-pixel SPg is 35% or more.

5 shows a peak luminance curve according to grayscale.

In a general display device, as shown in FIG. 5, the luminance curve is set to rise along a specific gamma curve (shown as gamma 2.2 in FIG. 5, but other gammas are possible) up to the peak luminance. In some cases, the peak luminance setting is differently set according to the area of the emission luminance region in the display panel 110 by applying a peak luminance control (PLC) technology to the display device.

That is, in the self-luminous display device, the peak luminance control (PLC) method of adjusting the peak luminance of the panel in units of one frame is used.

6 shows the concept of an average picture level.

The display device 100 implements luminance control according to an average picture level (APL) in order to realize low power consumption. That is, as shown in FIG. 6 , the display device 100 increases the luminance as the actual display area where the image is output at APL5% rather than APL25% among the entire display area of the panel on which the image is displayed decreases. It is realizing high-brightness and high-definition, which is the desire of consumers. At this time, in FIG. 6 , the pattern of the actual display area in which the image of the central part is output is set to the peak luminance, and the background is 0 gradation. Here, the average picture level (APL) refers to an average image level of an input image, and is a percentage of a difference between a reference white level and a black level of an input image for one frame. For example, a value obtained by normalizing each pixel of the input image to a maximum value may be obtained by taking gamma and multiplying the luminance ratio of each pixel as an average value.

The above-described PLC (Peak Luminance Control) technology calculates the average picture level (APL) of each frame image, and applies the maximum luminance set according to the calculated average picture level (APL) value to realize the input image. .

7 is a graph showing a peak luminance control (PLC) function according to an average image level.

For example, as shown in FIG. 7 , when the average image level (APL) is 100%, that is, data with gradation values of R, G, B (255, 255, 255) are output in the entire display area. Assuming that the luminance at this time (in this case, the entire display area becomes the actual display area) is 170 nits, when the average image level (APL) is 60%, that is, the gradation value of the data is the same, but the actual display area is reduced and the average When the image level is reduced to 60%, the luminance may appear as 320 nits, which is increased from 170 nits. When the average image level (APL) is 25%, that is, when the grayscale value of the data is the same, but the actual display area is further reduced and the average image level is reduced to 25%, the luminance may appear as 500 nits increased from 200 nits.

When the display device 100 controls the luminance according to an average picture level (APL), the luminance may increase exponentially from the luminance curve according to the gradation shown in FIG. 5 to the higher gradation. Since the display device 100 continues to use the same color coordinate even when going to a higher gray level, the amount of current used by the B sub-pixel SPb increases as the gray level increases. This is because, as shown in FIG. 4 , the color filter transmittance of the B sub-pixel SPb is low, and thus the efficiency is lowered. In particular, the efficiency of the sub-pixel B SPb may be further reduced as the gray scale increases.

In the above example, the RGBW sub-pixels (SPr, SPg, SPb, SPw) use a white organic light emitting diode (WOLED) and RGB color filters (CFr, CFg, CFb) as shown in FIG. 2 (white OLED) Although it has been described as an example implementation and that the amount of current increases according to the color filter transmittance, the method implemented with an organic light emitting diode that emits red, green, blue and white (RGB patterning OLED) also emits blue in the same way. Since the luminous efficiency of the organic light emitting diode is relatively low or the degradation level is high, the efficiency of the sub-pixel B SPb may be further reduced as the gray scale increases.

8 illustrates deterioration characteristics of each sub-pixel according to time in an RGBW sub-pixel structure. 9 shows a color temperature curve according to a gray level and a change in a color temperature curve according to a gray level when the same data voltage is applied after a lapse of time.

As a result, when the display device 100 controls the maximum peak luminance according to the average picture level (APL), as shown in FIG. 8 , the B sub-pixel SPb is used the most and the B sub-pixel SPb ) is degraded first, and as a result, the lifespan of the display device 100 is reduced. Next, since the white sub-pixel (SPw), which is frequently used, deteriorates next, as shown in FIG. 9, the color temperature according to the gradation decreases as time elapses (after lapse of time), but the color coordinate becomes lower at the high gradation. it goes wrong

In the above example, the B sub-pixel SPb, which has the lowest current transmittance and is frequently used, is exemplified as the first to deteriorate, but the first to deteriorate due to the use of various control techniques or the improvement of the color filter implementation technology in the future. The subject can run.

Hereinafter, a display device that controls the data voltage of a sub-pixel that deteriorates first above a specific gray level to be constant in order to solve the problem that the lifespan of the display device 100 is reduced according to the sub-pixel that is used the most and deteriorates first will be described. do. Furthermore, there is provided a display device that controls data voltages of sub-pixels so that the lifetime of the display device 100 does not decrease due to deterioration of a specific sub-pixel as a whole by maintaining the same degree of deterioration over time of the sub-pixels included in the pixel. .

10 is a configuration diagram of a timing controller according to an exemplary embodiment. 11A and 11B are conceptual diagrams of pixel driving according to APL reduction of a timing controller according to an exemplary embodiment. 12A to 12D are diagrams illustrating luminance curves in grayscale expression according to a decrease in APL of the timing controller according to an exemplary embodiment.

The timing controller 140 illustrated in FIG. 10 analyzes the input image data RGB in units of, for example, one or more frames to calculate an average picture level (hereinafter, referred to as APL). The timing controller 140 sets peak luminance for each frame according to the calculated APL as shown in FIG. 7 . For example, the timing controller 140 may set the peak luminance by referring to the peak luminance according to a PLC function stored as a lookup table in the memory 150 .

As shown in FIGS. 11A and 12A , the timing controller 140 converts RGB image data input from an external system into RWGB image data based on peak luminance for each frame according to the set APL. The reason for converting RGB image data into RWGB image data is to drive the display panel including the RWGB sub-pixels shown in FIG. 2 . In the above example, the timing controller 140 has been described as converting RGB image data into RWGB image data, but may be rearranged into RGB image data or other image data.

The timing controller 140 converts RGB image data input from an external system into RWGB image data when the grayscale is less than a specific grayscale among the gamma curves that will occur up to the peak luminance shown in FIG. 5 when the display device 100 expresses the grayscale.

On the other hand, the timing controller 140 expresses the target color coordinates for each gradation using a sub-pixel different from a white sub-pixel when the gamma curve generated up to the peak luminance shown in FIG. 5 is higher than a specific gradation when the display device 100 expresses the gradation. In this way, the target color coordinates representing the grayscale may be changed by matching the ratio of the data voltages of each sub-pixel when the grayscale is expressed.

For example, as shown in FIG. 12B , the timing controller 140 controls the data voltage of one of the two or more sub-pixels to be constant at a specific first gray level (eg, 240 gray levels) or higher. . At this time, as shown in FIGS. 12C and 11B , the timing controller 140 increases the data voltage of another second sub-pixel among the two or more sub-pixels to maintain the peak luminance of the pixel including the first sub-pixel. have.

That is, the timing controller 140 maintains a constant data voltage of the first sub-pixel for the image data RWGB of each pixel P at a specific first grayscale (eg, 240 grayscale) or higher, and the data of the second pixel P The image data R'W'G'B' corrected to increase the voltage is output to the data driver 120 through the data line.

The pixel including the first sub-pixel and the second sub-pixel may be located in a specific region expressing the maximum peak luminance of the display panel 110 . For example, the specific region may be an APL of a specific % or less. That is, the pixel including the first sub-pixel and the second sub-pixel may be located in a specific area of the display panel 110 with an average image level of 5% or less expressing the maximum peak luminance as shown in FIG. 6 . A specific region having an average image level of 5% or less expressing the maximum peak luminance may be located anywhere in the display panel 110 instead of only in the center of the display panel 110 as shown in FIG. 6 .

In other words, the driving control of the timing controller 140 may be applied only to a specific region of an actual image, for example, an area having an APL of 5% or less. This is because even if a very strong peak luminance is expressed in a small area, the luminance is better recognized by the human eye than the color coordinate recognition.

The first sub-pixel, which maintains a constant data voltage above a specific first gradation, is the sub-pixel that deteriorates the most due to the relatively high frequency of use, and the second sub-pixel has relatively low frequency of use and thus deterioration due to the characteristics of the device. It may be the worst sub-pixel. For example, as shown in FIGS. 11B and 12B , the first sub-pixel may be a blue sub-pixel SPb and the second sub-pixel may be a red sub-pixel SPr.

As described above, the timing controller 140 may control the amount of current used, ie, the data voltage, of the blue sub-pixel SPb to be fixed when the target color coordinate is greater than or equal to a specific grayscale. In this case, instead of fixing the amount of current used (data voltage) of the blue sub-pixel SPb, the luminance up to the peak luminance may be controlled to be driven by increasing the use ratio of the other sub-pixels. As a result, white balance may be slightly changed when a gray level greater than a specific gray level is expressed.

Even if a white balance is changed in the driving control of the timing controller 140 , the white sub-pixel SPw may be driven in the same manner as the blue sub-pixel SPb. The reason is that although the element deterioration due to the maximum current of the blue sub-pixel SPb is severe, the white sub-pixel SPw also deteriorates easily due to the high frequency of use.

That is, the timing controller 140 controls the data voltage of another third sub-pixel among the two or more sub-pixels to be constant at a specific second gray level or higher, and increases the data voltage of the second sub-pixel to increase the data voltage of the first sub-pixel. It is possible to control to maintain the peak luminance of the pixel including the pixel and the third sub-pixel.

In this case, the first sub-pixel is the sub-pixel that deteriorates the most in the characteristics of the device, the third sub-pixel is the sub-pixel that deteriorates less than the first sub-pixel in the characteristics of the device, and the second sub-pixel is the sub-pixel that deteriorates the least in the characteristics of the device. It may be a sub-pixel. For example, as shown in FIG. 8 , the first sub-pixel may be a blue sub-pixel SPr, the third sub-pixel may be a white sub-pixel SPw, and the second sub-pixel may be a red sub-pixel SPr.

The specific second gradation may be the same as the specific first gradation, but the second gradation may be larger than the first gradation. In other words, as shown in FIG. 12D , the timing controller 140 controls the data voltage of the blue sub-pixel SPr, which deteriorates the most in device characteristics at a specific first gray level or higher, to be constant, and controls the data voltage of the second gray level greater than the first gray level. The data voltage of the white sub-pixel SPw, which deteriorates more easily than the blue sub-pixel SPr, is controlled to be constant in the grayscale or higher.

As a result, when driving with W + G + B sub-pixels, for example, when expressing grayscale, the blue sub-pixel (SPb) stops driving (tracking) first in the middle of driving toward the peak luminance, and then the white sub-pixel (SPw) Next, driving is stopped to limit the maximum data voltages of the blue sub-pixel SPb and the white sub-pixel SPw.

As a result, in the worst case, that is, when peak luminance is displayed in a small APL, the color coordinate for white may shift toward yellow. In this case, if necessary, other sub-pixels with low frequency of use, for example, the red sub-pixel SPr, may be driven as well.

In other words, the timing controller 140 may intentionally stop driving a frequently used sub-pixel (tracking) even if a color coordinate shift occurs when driving peak luminance in a specific region, and use another sub-pixel instead to generate peak luminance. This color coordinate shift may support peak luminance to sub-pixels that are less deteriorated due to low frequency of use in accordance with the deterioration conditions of each sub-pixel of the display panel 110 .

FIG. 13 shows that the color coordinate for white shifts toward yellow when peak luminance is displayed in a small APL. 14 illustrates deterioration characteristics of sub-pixels according to time of a general display panel and a display panel according to an exemplary embodiment. 15 illustrates that the color coordinate movement state is improved even after time has elapsed in the display panel according to an exemplary embodiment.

For example, looking at the color coordinates when the APL is 25% and the APL is 0% as shown in FIG. 13 , the data voltage of the blue sub-pixel SPb is maintained constant at a specific first gray level or higher, and the white sub-pixel is maintained at the second gray level. It can be seen that when the data voltage of the blue sub-pixel SPb of the pixel SPw is kept constant and the data voltage of the red sub-pixel SPr is increased instead, the color coordinate is shifted to the yellow side.

According to the above-described exemplary embodiment, when the peak luminance of a small area is expressed, the pixel driving can be performed in a state in which the stress applied to the sub-pixel having a high use data voltage (current) or a high use frequency is reduced. That is, according to the above-described embodiment, the lifespan of the display panel 110 can be maximized by balancing the frequency of use for each sub-pixel and the total amount of applied bias.

According to the above-described embodiment, as shown in FIG. 14 , the lifetime of the display device 100 is not reduced due to deterioration of a specific sub-pixel as a whole by maintaining the same degree of deterioration over time of the sub-pixels included in the pixel. can

According to the above-described embodiment, it is possible to minimize the device deterioration deviation for each sub-pixel, so that the color coordinate shift (CCT lifespan) according to time can be improved as shown in FIG. 15 when grayscale is expressed. That is, according to the above-described exemplary embodiment, the lifespan of the display device is increased by controlling the data voltages above a specific gray level to minimize the deterioration deviation over time of the sub-pixels included in the pixel.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the technical field to which the present invention pertains that various substitutions, modifications and changes are possible within the scope without departing from the technical spirit of the present invention. It will be clear to those who have the knowledge of

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical configuration of the present invention can be changed to other specific forms by those skilled in the art to which the present invention pertains without changing the technical spirit or essential features of the present invention. It will be appreciated that this may be practiced. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. In addition, the scope of the present invention is indicated by the claims to be described later rather than the above detailed description. In addition, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention.

110: display panel
120: data driving unit
130: gate driver
140: timing controller

Claims (11)

a display panel including two or more pixels including two or more sub-pixels;
a data driver supplying data voltages to data lines connected to each of the sub-pixels;
a gate driver driving gate lines connected to each of the sub-pixels; and
The input image data of each sub-pixel is arranged and supplied by the data driver, and the data voltage of one of the two or more sub-pixels is controlled so that the data voltage of one of the two or more sub-pixels is constant at a specific first gray level or higher, a timing controller for controlling the data voltage of another second sub-pixel among the pixels to increase;
The data voltage supplied to the first sub-pixel is constant above the first gray scale. According to claim 1,
The timing controller is
and controlling to maintain a peak luminance of a pixel including the first sub-pixel by increasing the data voltage of the second sub-pixel. 3. The method of claim 2,
The display device according to claim 1, wherein the pixel is located in a specific region expressing the maximum peak luminance of the display panel. 4. The method of claim 3,
The specific area is an area having an average image level of a specific % or less. 5. The method of claim 4,
An average image level of less than or equal to a certain % is an average image level of less than or equal to 5%. 3. The method of claim 2,
The display device according to claim 1, wherein the first sub-pixel is a sub-pixel with the greatest degradation in device characteristics, and the second sub-pixel is a sub-pixel with the least degradation in device characteristics. 7. The method of claim 6,
wherein the first sub-pixel is a blue sub-pixel and the second sub-pixel is a red sub-pixel. According to claim 1,
The timing controller is
controlling the data voltage of another third sub-pixel among the two or more sub-pixels to be constant at a specific second gray level or higher;
and controlling to maintain peak luminance of pixels including the first sub-pixel and the third sub-pixel by increasing the data voltage of the second sub-pixel. 9. The method of claim 8,
The second gradation is a gradation greater than the first gradation. 9. The method of claim 8,
The first sub-pixel is a sub-pixel with the greatest deterioration in device characteristics, the third sub-pixel is a sub-pixel having less deterioration in device characteristics than the first sub-pixel, and the second sub-pixel is a sub-pixel with the least deterioration in device characteristics. A display device, characterized in that it is a pixel. 11. The method of claim 10,
wherein the first sub-pixel is a blue sub-pixel, the third sub-pixel is a white sub-pixel, and the second sub-pixel is a red sub-pixel.

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