Electroluminescent display device and driving method thereof

Abstract

To provide an electroluminescent display apparatus and a method of driving the electroluminescent display apparatus, which can enhance the effect of improving an afterimage without hindering the visibility for a user.SOLUTION: An electroluminescent display apparatus comprises a display panel including a plurality of pixels each containing a light-emitting element, and a controller. The controller receives input image data for a corresponding pixel among the pixels, determines accumulated stress data applied to the light-emitting element in the corresponding pixel due to an accumulation of image implemented in the corresponding pixel while being driven, determines a stress compensation gain corresponding to the accumulated stress data, determines a target compensation gain on the basis of the stress compensation gain and at least one of a lower limit compensation gain and an upper limit compensation gain, and outputs corrected input image data on the basis of the input image data and the target compensation gain for driving the corresponding pixel.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This specification relates to an electroluminescent display device and a driving method thereof.

Background Art

[0002] Electroluminescent display devices are classified into inorganic electroluminescent display devices and organic electroluminescent display devices according to the material of the light-emitting layer. Each pixel of an electroluminescent display device includes a light-emitting element that emits light by itself, and controls the light emission amount of the light-emitting element with a data voltage according to the gradation of video data to adjust the luminance.

[0003] The degradation characteristics of the light-emitting element may vary from pixel to pixel over time. When variations in degradation occur between pixels, the driving current that contributes to light emission varies between pixels even though the same data voltage is applied. Such variations in the driving current cause luminance non-uniformity (afterimage) and degrade the image quality.

[0004] In electroluminescent display devices, various attempts have been made to delay the degradation of pixels, but the viewing patterns of users have not been considered, and a sufficient afterimage improvement effect has not been obtained.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, the present embodiment is for solving the above-described problems, and provides an electroluminescent display device and a driving method thereof that can adaptively control the amount of luminance reduction according to the viewing pattern of a user and improve the afterimage improvement effect.

Means for Solving the Problems

[0006] To overcome or mitigate the above problems of the related art, the present disclosure provides an electroluminescent display device and a driving method thereof that adaptively adjust the degree of luminance reduction based on the viewing behavior of a user in order to enhance the effect of preventing or reducing afterimages.

[0007] Further features and aspects of the present disclosure are described in the following description, and will become apparent in part from the description, or can be learned by the practice of the inventive concept provided herein. Other features and aspects of the inventive concept can be realized and achieved by structures that are particularly pointed out or can be derived from in the specification, the claims, and the accompanying drawings.

[0008] The electroluminescent display device according to the present embodiment includes a display panel including a plurality of pixels each including a light-emitting element, receives input image data for corresponding pixels among the pixels, and determines cumulative stress data applied to the light-emitting element of the corresponding pixel by the accumulation of the image embodied in the corresponding pixel during driving, determines a stress compensation gain corresponding to the cumulative stress data, determines a target compensation gain based on at least one of a lower limit compensation gain and an upper limit compensation gain and the stress compensation gain, and includes an afterimage improvement circuit that outputs corrected input image data based on the input image data for driving the corresponding pixel and the target compensation gain.

[0009] The driving method of the electroluminescent display device according to the present embodiment includes steps of receiving input image data for corresponding pixels among the pixels, determining cumulative stress data applied to the light-emitting element of the corresponding pixel by the accumulation of the image embodied in the corresponding pixel during driving, determining a stress compensation gain corresponding to the cumulative stress data, determining a target compensation gain based on at least one of a lower limit compensation gain and an upper limit compensation gain and the stress compensation gain, outputting corrected input image data based on the input image data and the target compensation gain, and driving the corresponding pixel based on the corrected input image data.

[0010] In yet another aspect of the present disclosure, the display device includes a display panel having a plurality of pixels each having a light-emitting element, a control unit, and a driving unit. The control unit receives input video data for corresponding pixels among the plurality of pixels, determines cumulative stress data representing cumulative stress applied to the light-emitting element of the corresponding pixel by an image implemented on the corresponding pixel during driving, determines a target compensation gain based on the cumulative stress data, outputs corrected input video data based on the input video data and the target compensation gain, and the driving unit drives the corresponding pixels based on the corrected image data.

[0011] In addition to the above advantages of the present disclosure, other features and advantages of the present disclosure will be described below or can be clearly understood by those skilled in the art from such descriptions or explanations.

[0012] It should be understood that both the foregoing summary of the present disclosure and the following detailed description are exemplary and are intended to provide further description of the present disclosure as claimed.

Advantages of the Invention

[0013] According to this embodiment, the following effects can be achieved. This embodiment adopts a hybrid brightness reduction method, adaptively controls the amount of brightness reduction according to the viewing mode of the user, and can improve the afterimage improvement effect without disturbing the visual perception of the user.

[0014] This embodiment can prevent the brightness from being excessively reduced under viewing conditions with high stress by setting a lower limit of the target compensation gain according to the cumulative driving time.

[0015] This embodiment can prevent the luminance increase of the element or the reverse afterimage caused by overcompensation by setting an upper limit of the target compensation gain according to the cumulative driving time.

[0016] The effects according to this specification are not limited to the contents exemplified above, and more diverse effects are included in this specification.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

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Figure 9

Best Mode for Carrying Out the Invention

[0018] Hereinafter, preferred embodiments will be described in detail with reference to the accompanying drawings. The same reference numerals throughout the specification denote substantially the same components. In the following description, if it is determined that a detailed description of the notification function or configuration according to the content of this specification is unnecessary for understanding the content or will hinder it, the detailed description thereof will be omitted.

[0019] The terms "first", "second", A, B, (a), (b), etc. may be used in this specification to describe various elements, but these elements are not used to define the specific nature, order, sequence, priority, or number of such elements, so they should not be construed as being limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the present disclosure, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element.

[0020] In interpreting an element, the element should be construed as including an error or tolerance even if no explicit description of such error or tolerance is provided.

[0021] FIG. 1 is a block diagram showing an electroluminescent display device according to an embodiment of the present specification. Referring to FIG. 1, an electroluminescent display device according to an embodiment of the present specification may include a display panel 10, a timing controller 11, a data driver 12, a gate driver 13, a memory circuit 20, and an afterimage improvement circuit 111. In FIG. 1, the timing controller 11 and the data driver 12 may be integrated in whole or in part within a drive integrated circuit.

[0022] On the screen where the input video is displayed on the display panel 10, data lines 14 extending in the column (or vertical) direction and gate lines 15 extending in the row (or horizontal) direction intersect, and pixels PIX are arranged in a matrix for each intersection region to form a pixel array. Each data line 14 is commonly connected to adjacent pixels PIX in the column direction, and each gate line 15 is commonly connected to adjacent pixels PIX in the row direction.

[0023] Pixels PIX included in the pixel array can be grouped in plural numbers to represent various colors. When defining a pixel group for color representation as a unit pixel, one unit pixel can also be composed of R (red), G (green), and B (blue) pixels, and can be composed of R (red), G (green), B (blue), and W (white) pixels.

[0024] Each of the pixels PIX includes a light-emitting element and a driving element that generates a driving current according to the voltage between the gate and the source to drive the light-emitting element. The light-emitting element can include an anode electrode, a cathode electrode, and an organic compound layer formed between these electrodes. The organic compound layer can include, but is not limited to, a hole injection layer (Hole Injection layer, HIL), a hole transport layer (Hole transport layer, HTL), an emission layer (Emission layer, EML), an electron transport layer (Electron Injection layer, EIL), etc. When a driving current flows through the light-emitting element, holes that have passed through the hole transport layer HTL and electrons that have passed through the electron transport layer ETL move to the emission layer EML to form excitons, and as a result, the emission layer EML can emit visible light. On the other hand, the organic compound layer can also be replaced with an inorganic compound layer.

[0025] The driving element can be implemented by a low-temperature polysilicon (Low-Temperature-Poly-Silicon, LTPS) or oxide (Oxide) thin film transistor on an organic substrate (or plastic substrate) base, but is not limited thereto. The driving element can also be implemented as a CMOS transistor on a silicon wafer (Si-wafer) base.

[0026] There has been an increasing attempt to embody some elements included in a pixel circuit (particularly, a switching element in which a source or a drain is connected to a gate of a driving element) as an oxide transistor. The oxide transistor uses an oxide, i.e., an oxide IGZO in which indium (In), gallium (Ga), zinc (Zn), and oxygen (O) are combined, instead of polysilicon as a semiconductor material. The oxide transistor has advantages that its electron mobility is more than 10 times higher than that of an amorphous silicon transistor and its manufacturing cost is much lower than that of an LTPS transistor. Also, since the oxide transistor has a low off-current, it also has an advantage of high driving stability and reliability during low-speed driving when the off-period of the transistor is relatively long. Therefore, an oxide transistor can be adopted for an OLED TV that requires high resolution and low power driving or cannot support a screen size in a low-temperature polysilicon process.

[0027] The electrical characteristics (e.g., operating point voltage or threshold voltage) of the light-emitting element must be uniform for all pixels, but there may be a difference (hereinafter referred to as pixel-to-pixel degradation deviation) between pixels PIX due to stress over time of driving. If pixel-to-pixel degradation deviation occurs, the driving current contributing to light emission in the pixel can only change even if the same data voltage is applied. Such a deviation of the driving current causes afterimages and degrades the image quality.

[0028] The afterimage improvement circuit 111 uses a hybrid brightness reduction method in which a timer-based brightness reduction method and an OLED stress-based brightness reduction method are mixed to delay the degradation of the pixel PIX.

[0029] The timer-based brightness reduction method is a method of gradually reducing the brightness based on a target compensation gain set according to the cumulative driving time of the light-emitting element. According to the timer-based brightness reduction method, since the brightness is reduced only by the cumulative driving time regardless of viewing conditions such as the type and intensity of the video, the afterimage improvement effect is not great for videos with strong stress or videos based on heavy user criteria.

[0030] The OLED stress-based brightness reduction method is a method of reducing stress by adjusting the degree of brightness decrease according to the viewing behavior of consumers. According to the OLED stress-based brightness reduction method, the amount of brightness reduction varies depending on the viewing conditions.

[0031] The hybrid brightness reduction method of this embodiment derives the cumulative stress data applied to the light-emitting element from the cumulative image realized by the pixel (PIX) during the cumulative driving time, and when the cumulative stress data is lower than a preset reference stress value, the brightness is reduced at the timer-based brightness reduction method level, and if the cumulative stress data is greater than or equal to the reference stress value, the brightness is reduced at the OLED stress-based brightness reduction method level.

[0032] The hybrid brightness reduction method of this embodiment can prevent the brightness from being excessively reduced under viewing conditions with high stress by setting the lower limit of the target compensation gain according to the cumulative driving time.

[0033] The hybrid brightness reduction method of this embodiment can prevent the reverse afterimage caused by the brightness increase or overcompensation of the element by setting the upper limit of the target compensation gain according to the cumulative driving time.

[0034] The afterimage improvement circuit 111 may be implemented in the timing controller 11, but is not limited thereto. The afterimage improvement circuit 111 corrects the input image data DATA with the target compensation gain to generate corrected image data CDATA, and supplies the corrected image data CDATA to the data driver 12.

[0035] The timing controller 11 inputs timing signals such as a vertical synchronization signal (Vsync), a horizontal synchronization signal (Hsync), a data enable signal (DE), and a dot clock (DCLK) from the host system, and generates timing control signals for controlling the operation timing of the data driver 12 and the gate driver 13. The timing control signals can include a gate timing control signal GDC and a data timing control signal DDC.

[0036] The data driver 12 is connected to the pixel PIX via the data line 14. The data driver 12 generates the data voltage required for driving the pixel PIX and supplies it to the data line 14. The data driver 12 samples and latches the correction image data CDATA input from the afterimage improvement circuit 111 based on the data timing control signal DDC, replaces it with parallel data, maps the parallel data to the gamma compensation voltage, and converts it into an analog data voltage. The data voltage can have different voltage levels so as to correspond to the image gradations to be represented by the pixel PIX.

[0037] The data driver 12 can be composed of a plurality of source driver integrated circuits. The source driver integrated circuit can include a shift register, a latch, a level shifter, a DAC (Digital to Analog Converter), and an output buffer.

[0038] The gate driver 13 is connected to the pixel PIX through the gate line 15. The gate driver 13 generates a scan signal based on the gate timing control signal GDC, and supplies each scan signal to the gate line 15 in accordance with the supply timing of the data voltage. The horizontal pixel line to which the data voltage is supplied is selected by the scan signal. Each of the scan signals can be generated in a pulse type that swings between a gate on voltage and a gate off voltage. The gate on voltage is set to a voltage higher than the threshold voltage of the transistor, and the gate off voltage is set to a voltage lower than the threshold voltage of the transistor. The transistor is turned on in response to the gate on voltage, while it is turned off in response to the gate off voltage.

[0039] The gate driver 13 can be composed of a number of gate drive integrated circuits each including a gate shift register, a level shifter for converting the output signal of the gate shift register into a swing width suitable for driving the transistors of the pixels, and an output buffer, etc. Alternatively, the gate driver 13 can also be directly formed on the substrate of the display panel 10 in the GIP (Gate driver In Panel) method. In the case of the GIP method, the level shifter is mounted on a PCB (Printed Circuit Board), and the gate shift register can be formed in the bezel area which is the non-display area of the display panel 10. The gate shift register includes a number of scan output stages connected to each other in a cascade manner. The scan output stages are independently connected to the gate lines and output scan signals to the gate line 15.

[0040] The memory circuit 20 stores a preset target compensation gain graph. The target compensation gain graph defines the operating range of the target compensation gain based on the cumulative driving time and the cumulative stress data, and can include a plurality of look-up tables. The memory circuit 20 can be composed of a NAND memory or a flash memory.

[0041] FIG. 2 is a block diagram showing the afterimage improvement circuit according to the present embodiment. FIG. 3 is a diagram showing the stress conversion process performed by the stress accumulation circuit according to the present embodiment. FIG. 4 is a diagram showing the cumulative stress data according to the cumulative driving time and the stress compensation gain mapped to the cumulative stress data. FIG. 5 is a diagram showing the setting range of the target compensation gain according to the cumulative driving time. And FIG. 6 is a diagram showing the operation procedure of the gain calculation circuit according to the present embodiment.

[0042] Referring to FIG. 2, the afterimage improvement circuit 111 can include a timer TM, a stress accumulation circuit SAC, a look-up circuit LUT, a gain calculation circuit GCC, and a data compensation circuit GCC.

[0043] The timer TM counts the time for which the light-emitting elements included in each pixel of the display panel emit light and outputs the cumulative driving time. The cumulative driving time is the sum of the time during which video is played on the display panel. The timer TM counts the time during which the screen of the display panel is on and outputs the cumulative driving time.

[0044] The stress accumulation circuit SAC derives the cumulative stress data applied to the light-emitting elements by the cumulative video embodied in the pixels during the cumulative driving time. The stress accumulation circuit SAC derives the stress value corresponding to each gradation of the input video data DATA by referring to a stress conversion look-up table set in advance as shown in FIG. 3. The stress value indicates the predicted degradation amount of the light-emitting elements due to the cumulative driving time. In the stress conversion look-up table, the stress values corresponding to each gradation of the input video data DATA are mapped to the cumulative driving time. The stress conversion look-up table can be created in advance through a stress value conversion algorithm. Examples of such stress value conversion algorithms include, but are not limited to, the following equations. Stress = I n (Equation 1) Stress = I * exp(Ea / KT) (Equation 2) Here, "I" is the current, "n" is the luminance acceleration coefficient, "Ea" is the activation energy, "K" is the Boltzmann constant, and "T" is the temperature.

[0045] In the data pattern approval process, the gradation-specific data pattern in the initial state before degradation is applied to the display panel and the current is measured. In the stress value conversion process, the measured current value is converted into a stress value using a predefined functional equation. For example, it is one of the above stress conversion algorithms. However, the present disclosure is not limited thereto. Stress may generally be determined as a function of several factors that affect the pixel lifetime, and a predetermined function may be selected by those skilled in the art. For example, such a function can be represented as one of the following general functions. Stress = f(current density, temperature,...) (Equation 3) Stress = f(factor 1, factor 2, factor 3,...) (Equation 4)

[0046] The stress accumulation circuit SAC outputs the accumulated stress data derived through the stress conversion look-up table. The stress accumulation circuit SAC may further include an internal memory for updating and storing the accumulated stress data.

[0047] The look-up circuit LUT can include a plurality of look-up tables downloaded in the memory circuit 20 when the system power is turned on. The look-up circuit LUT includes a lower limit target look-up table TTL1, an upper limit target look-up table TTL2, and a stress target look-up table OTL.

[0048] The lower limit target look-up table TTL1 outputs a timer lower limit compensation gain LL-G using the accumulated drive time input from the timer TM as a read address. The timer lower limit compensation gain LL-G is located on the timer lower limit line of the target compensation gain graph in FIG. 5.

[0049] The upper limit target look-up table TTL2 outputs a timer upper limit compensation gain UL-G using the accumulated drive time input from the timer TM as a read address. The timer upper limit compensation gain UL-G is located on the timer upper limit line of the target compensation gain graph in FIG. 5.

[0050] The stress target look-up table OTL outputs a stress compensation gain S-G using the accumulated stress data input from the stress accumulation circuit SAC as a read address. The stress target look-up table OTL can be configured as shown in FIG. 4 as an example. In FIG. 4, the accumulated stress data according to the accumulated drive time and the stress compensation gain S-G mapped to the accumulated stress data are set in advance. The stress compensation gain S-G is located within the gain region AA surrounded by the timer lower limit line and the timer upper limit line in the target compensation gain graph of FIG. 5.

[0051] The gain calculation circuit GCC calculates the target compensation gain based on the lower limit compensation gain LL-G, the upper limit compensation gain UL-G, and the stress compensation gain S-G input from the look-up circuit LUT.

[0052] As shown in FIG. 6, the gain calculation circuit GCC sets the relatively smaller value among the upper limit compensation gain UL-G and the stress compensation gain S-G as the first calculation value (S31). Subsequently, the gain calculation circuit GCC sets the relatively larger value among the first calculation value and the lower limit compensation gain LL-G as the second calculation value (S32). Subsequently, the gain calculation circuit GCC outputs the second calculation value as the target compensation gain (S33).

[0053] The data compensation circuit GCC corrects the video data DATA written into the pixels downward based on the target compensation gain input from the gain calculation circuit GCC.

[0054] Since the target compensation gain multiplied by the video data DATA is 1 as shown in FIG. 5, the corrected video data CDATA becomes lower than the original gradation value.

[0055] The hybrid brightness reduction method of this embodiment can be realized by the operation of the afterimage improvement circuit 111 based on the target compensation gain graph in FIG. 5. The form of the target compensation gain graph can be set as shown in FIG. 5 so that the brightness reduction degree can be adaptively adjusted according to the cumulative driving time and the user's viewing behavior.

[0056] Specifically, at the first cumulative drive time (0) of the target compensation gain graph, the timer lower limit line and the timer upper limit line have the same first target compensation gain. At the second cumulative drive time (50000) of the target compensation gain graph, which is more than the first cumulative drive time (0), the timer lower limit line and the timer upper limit line have the same second target compensation gain. And at the third cumulative drive time (0 - 50000) of the target compensation gain graph, which is between the first cumulative drive time (0) and the second cumulative drive time (50000), the timer lower limit line has a third target compensation gain, and the timer upper limit has a fourth target compensation gain. Here, the first target compensation gain is 1, the second target compensation gain is 0.5, the third target compensation gain is a first value between 0.5 and 1, and the fourth target compensation gain is a second value between 0.5 and 1. And the second value is higher than the first value.

[0057] If the brightness is excessively lowered for afterimage improvement, it will interfere with the user's visual perception, which is not preferable. The applicant set the minimum value of the target compensation gain to 0.5 through multiple experiments and determined the time (T50) when the brightness reaches 50% as the reference brightness specification.

[0058] In the target compensation gain graph, in order to enhance the afterimage improvement effect and increase T50, the timer lower limit line and the timer upper limit line can be designed to have inflection points near the target compensation gain of 0.6 respectively.

[0059] Specifically, the timer lower limit line includes a first lower limit line SLP1 having a first slope and a second lower limit line SLP2 having a second slope that is gentler than the first slope. The first lower limit line SLP1 and the second lower limit line SLP2 may be connected to each other via a first inflection point IFP1.

[0060] The timer upper limit line includes a first upper limit line SLP3 having a third slope and a second upper limit line SLP4 having a fourth slope that is gentler than the third slope. The first upper limit line SLP3 and the second upper limit line SLP4 may be connected to each other via a second inflection point IFP2.

[0061] The first lower limit line SLP1 having a first slope and the first upper limit line SLP3 having a third slope coincide with each other at the first cumulative drive time (0). And the second lower limit line SLP2 having a second slope and the second upper limit line SLP4 having a fourth slope coincide with each other at a second cumulative drive time 50000 which is more than the first cumulative drive time.

[0062] The second slope is gentler than the first slope, and the fourth slope is gentler than the third slope. Due to the relatively inclined first and third slopes, the luminance can rapidly decrease before the light-emitting element deteriorates, improving the afterimage. And due to the relatively gentle second and fourth slopes, T50 increases. The visual perception of the user can be improved.

[0063] FIG. 7 is a diagram showing the afterimage distribution according to the drive time when the timer and stress-based luminance reduction algorithms are applied.

[0064] Referring to FIG. 7, the hybrid luminance reduction method (solid line notation) of the present embodiment adaptively adjusts the luminance reduction degree according to the cumulative drive time and the viewing behavior of the user. Therefore, compared with other luminance reduction methods (target not applied, timer-based luminance reduction method), there is an effect that the ratio of afterimage generation can be lowered at a relatively short cumulative drive time (10000 - 20000).

[0065] FIG. 8 is a diagram for explaining the risk when the timer upper limit line and the timer lower limit line are not set in the target compensation gain graph.

[0066] The potential risk when there is no timer lower limit can be explained by the embedded mode and the heavy use mode in FIG. 8 (XX reference). Since the store mode uses high luminance for sales promotion, the luminance reaches 50% in about 2200 hours. The heavy use mode is used for gaming purposes, and excessive stress is applied to the light-emitting element, so the luminance reaches 50% in about 5800 hours. Thus, without a timer lower limit, the luminance becomes excessively low within a short time, which can degrade the visual perception of the user.

[0067] The risk in the case of no timer upper limit can be explained through the luminance increase mode in FIG. 8 (refer to XY). The luminance increase mode may increase the luminance of the element, cause overcompensation, accelerate the stress applied to the light-emitting element, and cause reverse afterimages.

[0068] On the contrary, since the hybrid luminance reduction mode of this embodiment includes a timer lower limit line, a timer upper limit line, and a gain region AA, the above-described problems can be avoided.

[0069] FIG. 9 is a diagram for explaining the compensation results according to various forms of the timer upper limit line and the timer lower limit line set in the target compensation gain graph.

[0070] Referring to FIG. 9, when the timer lower limit line is set in a step shape, the luminance can rapidly decrease during step-down, deteriorating the user's visual perception. The same applies to the timer upper limit. From the perspective of the user's visual perception, it is preferable that the luminance be gradually reduced over a long period of time.

[0071] Also, if the timer lower limit line is set too low, the quality of the luminance performance cannot be maintained due to excessive luminance reduction.

[0072] Also, if the target is not set, the stress applied to the light-emitting element may be accelerated due to high luminance, and reverse afterimages may occur.

[0073] On the contrary, since the timer lower limit line and the timer upper limit line of this embodiment each have an inclination inflection point and have a form of gradually decreasing the luminance, they are effective for improving afterimages without hindering the user's visual perception.

[0074] The present invention can embody the following effects and advantages.

[0075] The present invention can enhance the effect of reducing afterimages without disturbing the visibility of a user by adaptively adjusting the degree of brightness reduction based on the viewing behavior of the user by using a hybrid brightness reduction method.

[0076] The lower limit of the target compensation gain may be set based on the cumulative drive time amount so that the brightness does not excessively decrease under viewing conditions with high stress.

[0077] The upper limit of the target compensation gain can be set based on the cumulative drive time amount to prevent the occurrence of reverse afterimages due to overcompensation and the increase in element brightness.

[0078] The effects and advantages according to the exemplary embodiments of the present disclosure are not limited to the above examples, and various other effects and advantages can be actually realized.

[0079] The exemplary embodiments of the present disclosure can be described as follows.

[0080] The electroluminescent display device according to the present invention includes a display panel including a plurality of pixels each including a light-emitting element, and a control unit. The control unit receives input image data for a corresponding pixel among the pixels, determines cumulative stress data applied to the light-emitting element of the corresponding pixel by the accumulation of the image embodied in the corresponding pixel during driving, determines a stress compensation gain corresponding to the cumulative stress data, determines a target compensation gain based on at least one of a lower limit compensation gain and an upper limit compensation gain and the stress compensation gain, and outputs corrected input image data based on the input image data for driving the corresponding pixel and the target compensation gain.

[0081] The control unit may be further configured to count the drive time during which the light-emitting element emits light and output the cumulative drive time. The lower limit compensation gain and the upper limit compensation gain may each correspond to the cumulative drive time amount.

[0082] Preferably, it further includes a memory circuit that stores a target compensation gain graph indicating a setting range of a target compensation gain according to the cumulative drive time and the cumulative stress data. The setting range of the target compensation gain may include a timer lower limit representing a lower limit compensation gain, a timer upper limit representing an upper limit compensation gain, and a gain region surrounded by the timer lower limit and the timer upper limit in the target compensation gain graph. The stress compensation gain may be within the gain region of the target compensation gain graph.

[0083] The timer lower limit and the timer upper limit can have the same first target compensation gain at a first cumulative drive time in the target compensation gain graph. The timer lower limit and the timer upper limit may have the same second target compensation gain at a second cumulative drive time amount in the target compensation gain graph, and the second cumulative drive time amount is larger than the first cumulative drive time amount. At a third cumulative drive time amount in the target compensation gain graph between the first cumulative drive time amount and the second cumulative drive time amount, the timer lower limit may have a third target compensation gain, and the timer upper limit may have a fourth target compensation gain. The first target compensation gain can be 1, the second target compensation gain can be 0.5, the third target compensation gain can have a first value between 0.5 and 1, and the fourth target compensation gain can have a second value between 0.5 and 1. The second value may be larger than the first value.

[0084] The timer lower limit line includes a first lower limit line having a first slope and a second lower limit line having a second slope gentler than the first slope, and the first lower limit line and the second lower limit line may be connected at a first inflection point in the target compensation gain graph. The timer upper limit includes a first upper limit line having a third slope and a second upper limit line having a fourth slope gentler than the third slope, and the first upper limit line and the second upper limit line may be connected at a second inflection point in the target compensation gain graph.

[0085] The first lower limit line having a first slope intersects a first upper limit line having a third slope at a first cumulative driving time in the target compensation gain graph. The second lower limit line having a second slope may intersect a second upper limit line having a fourth slope at a second cumulative driving time greater than the first cumulative driving time in the target compensation gain graph. The first target compensation gain corresponding to the first lower limit line and the first upper limit line at the first cumulative driving time is 1, and the second target compensation gain corresponding to the second lower limit line and the second upper limit line at the second cumulative driving time may be 0.5.

[0086] In some exemplary embodiments, the electroluminescent display device may further include a data driver that drives corresponding pixels based on the corrected image data.

[0087] In another embodiment, a method of driving an electroluminescent display device includes: a display panel having a plurality of pixels each having a light emitting device; receiving input image data of a corresponding pixel among the pixels; determining cumulative stress data applied to the light emitting device in the corresponding pixel by accumulation of an image embodied in the corresponding pixel during driving; determining a stress compensation gain corresponding to the accumulated stress data; calculating a target compensation gain based on the stress compensation gain and at least one of a lower limit compensation gain and an upper limit compensation gain; outputting corrected input image data based on the input image data and the target compensation gain; and driving corresponding pixels based on the corrected input image data.

[0088] The method may further include counting a driving time during which the light emitting device emits light and outputting a cumulative driving time. The lower limit compensation gain and the upper limit compensation gain may each correspond to an amount of the cumulative driving time.

[0089] The method may further include a step of storing a target compensation gain graph representing a setting range of a target compensation gain based on cumulative driving time and cumulative stress data. The setting range of the target compensation gain may include a timer lower limit representing a lower limit compensation gain, a timer upper limit representing an upper limit compensation gain, and a gain region surrounded by the timer lower limit and the timer upper limit in the target compensation gain graph. The stress compensation gain may be within the gain region of the target compensation gain graph.

[0090] The timer lower limit and the timer upper limit may have the same first target compensation gain at a first cumulative driving time in the target compensation gain graph. The timer lower limit and the timer upper limit may have the same second target compensation gain at a second cumulative driving time amount in the target compensation gain graph, and the second cumulative driving time amount is greater than the first cumulative driving time amount. At a third cumulative driving time amount in the target compensation gain graph between the first cumulative driving time amount and the second cumulative driving time amount, the timer lower limit may have a third target compensation gain, and the timer upper limit may have a fourth target compensation gain. The first target compensation gain may be 1, the second target compensation gain may be 0.5, the third target compensation gain may have a first value between 0.5 and 1, and the fourth target compensation gain may have a second value between 0.5 and 1. The second value may be greater than the first value.

[0091] The timer lower limit line includes a first lower limit line having a first slope and a second lower limit line having a second slope gentler than the first slope, and the first lower limit line and the second lower limit line may be connected at a first inflection point in the target compensation gain graph. The timer upper limit includes a first upper limit line having a third slope and a second upper limit line having a fourth slope gentler than the third slope, and the first upper limit and the second upper limit may be connected to each other at a second inflection point in the target compensation gain graph.

[0092] The first lower limit line having the first slope intersects the first upper limit line having the third slope at the first cumulative driving time in the target compensation gain graph. The second lower limit line having the second slope can intersect the second upper limit line having the fourth slope at a second cumulative driving time greater than the first cumulative driving time in the target compensation gain graph. The first target compensation gain corresponding to the first lower limit line and the first upper limit line at the first cumulative driving time is 1, and the second target compensation gain corresponding to the second lower limit and the second upper limit line at the second cumulative driving time is 0.5.

[0093] In other exemplary embodiments, the display device includes a display panel having a plurality of pixels each having a light-emitting element, a control unit, and a data driver. The control unit receives input video data for corresponding pixels among the plurality of pixels, determines cumulative stress data representing the cumulative stress applied to the light-emitting elements of the corresponding pixels by the images implemented on the corresponding pixels during driving, determines a target compensation gain based on the cumulative stress data, outputs corrected input video data based on the input video data and the target compensation gain, and the data driver drives the corresponding pixels based on the corrected image data.

[0094] In some exemplary embodiments, the control unit determines the cumulative driving time during which the light-emitting element emits light, and determines the target compensation gain based on the cumulative driving time and the cumulative stress data.

[0095] In some exemplary embodiments, the control unit determines a lower limit compensation gain and an upper limit compensation gain corresponding to the amount of the cumulative driving time, determines a stress compensation gain corresponding to the cumulative stress data, and determines the target compensation gain based on the lower limit compensation gain, the upper limit compensation gain, and the stress compensation gain.

[0096] The display device may further include a memory circuit that stores a target compensation gain graph representing a predetermined range of the target compensation gain according to the cumulative drive time and the cumulative stress data. The predetermined range of the target compensation gain may include a timer lower limit representing a lower limit compensation gain, a timer upper limit representing an upper limit compensation gain, and a gain region surrounded by the timer lower limit and the timer upper limit in the target compensation gain graph. The stress compensation gain may be within the gain region of the target compensation gain graph.

[0097] The timer lower limit and the timer upper limit can have the same first target compensation gain at a first cumulative drive time in the target compensation gain graph. The timer lower limit and the timer upper limit may have the same second target compensation gain at a second amount of the cumulative drive time in the target compensation gain graph, and the second amount is greater than the first amount. At a third amount of the cumulative drive time in the target compensation gain graph between the first amount of the cumulative drive time and the second amount of the cumulative drive time, the timer lower limit may have a third target compensation gain, and the timer upper limit may have a fourth target compensation gain. The first target compensation gain can be 1, the second target compensation gain can be 0.5, the third target compensation gain can have a first value between 0.5 and 1, and the fourth target compensation gain can have a second value between 0.5 and 1. The second value may be greater than the first value.

[0098] The timer lower limit line includes a first lower limit line having a first slope and a second lower limit line having a second slope gentler than the first slope, and the first lower limit line and the second lower limit line may meet at a first inflection point in the target compensation gain graph. The timer upper limit includes a first upper limit line having a third slope and a second upper limit line having a fourth slope gentler than the third slope, and the first upper limit line and the second upper limit line may meet at a second inflection point in the target compensation gain graph.

[0099] In some exemplary embodiments, the control unit may include a first look-up table configured to provide a lower limit compensation gain based on the amount of cumulative driving time, a second look-up table configured to provide an upper limit compensation based on the amount of cumulative driving time, and a third look-up table configured to provide a stress compensation gain based on the accumulated stress data.

[0100] As described above, the preferred embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, but the technical scope of the present disclosure is not limited to such examples. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. Therefore, the foregoing exemplary embodiments disclosed herein should be construed as illustrative of the principles of the present disclosure, but not as limiting. The scope of the present disclosure is not limited to the foregoing exemplary embodiments. Therefore, the above exemplary embodiments should not be construed as exhaustive in any way.

[0101] From the above description, those skilled in the art will understand that various changes and modifications can be made without departing from the technical idea of the present invention. Therefore, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the scope of the claims.

Explanation of Reference Numerals

[0102] 10 Display panel 11 Timing controller 12 Data driver 13 Gate driver 20 Memory circuit 30 Compensation circuit 113 Compensation gain calculation circuit 210 First memory

Claims

1. A display panel including a plurality of pixels each including a light-emitting element, and a control unit, wherein the control unit receives input image data for corresponding pixels among the pixels, determines cumulative stress data applied to the light-emitting elements of the corresponding pixels by accumulation of an image embodied in the corresponding pixels during driving, determines a stress compensation gain corresponding to the cumulative stress data, determines a target compensation gain based on at least one of a lower limit compensation gain and an upper limit compensation gain and the stress compensation gain, outputs the input image data corrected based on the input image data for driving the corresponding pixels and the target compensation gain, the control unit further counts a time during which the light-emitting element of the corresponding pixel emits light and outputs a cumulative driving time, the lower limit compensation gain and the upper limit compensation gain respectively correspond to the cumulative driving time, further includes a memory circuit storing a target compensation gain graph indicating a setting range of the target compensation gain according to the cumulative driving time and the cumulative stress data, the setting range of the target compensation gain includes, in the target compensation gain graph, a timer lower limit line at which the lower limit compensation gain is located, a timer upper limit line at which the upper limit compensation gain is located, and a gain area surrounded by the timer lower limit line and the timer upper limit line, the stress compensation gain is within the gain area, an electroluminescent display device.

2. At a first cumulative driving time of the target compensation gain graph, the timer lower limit line and the timer upper limit line have the same first target compensation gain, at a second cumulative driving time of the target compensation gain graph greater than the first cumulative driving time, the timer lower limit line and the timer upper limit line have the same second target compensation gain, at a third cumulative driving time of the target compensation gain graph between the first cumulative driving time and the second cumulative driving time, the timer lower limit line has a third target compensation gain and the timer upper limit line has a fourth target compensation gain, the first target compensation gain is 1, the second target compensation gain is 0.5, the third target compensation gain is a first value between 0.5 and 1, and the fourth target compensation gain is a second value between 0.5 and 1, the second value is greater than the first value, The electroluminescent display device according to Claim 1.

3. The timer lower limit line includes a first lower limit line having a first slope and a second lower limit line having a second slope gentler than the first slope, and the first lower limit line and the second lower limit line are connected to each other via a first inflection point. The timer upper limit line includes a first upper limit line having a third slope and a second upper limit line having a fourth slope gentler than the third slope, and the first upper limit line and the second upper limit line are connected to each other via a second inflection point. The electroluminescent display device according to claim 1.

4. The first lower limit line having the first slope intersects the first upper limit line having the third slope at the first cumulative driving time. The second lower limit line having the second slope intersects the second upper limit line having the fourth slope at a second cumulative driving time longer than the first cumulative driving time. The first target compensation gain corresponding to the first lower limit line and the first upper limit line at the first cumulative driving time is 1. At the second cumulative driving time, the second target compensation gain corresponding to the second lower limit line and the second upper limit line is 0.

5. The electroluminescent display device according to claim 3.

5. Further including a data driver for driving corresponding pixels based on the corrected input image data. The electroluminescent display device according to claim 1.

6. A driving method of an electroluminescent display device including a display panel having a plurality of pixels each including a light emitting element, comprising: Receiving input image data for a corresponding pixel among the pixels; Determining cumulative stress data applied to the light emitting element of the corresponding pixel by cumulative of an image embodied in the corresponding pixel during driving; Determining a stress compensation gain corresponding to the cumulative stress data; Determining a target compensation gain based on at least one of a lower limit compensation gain and an upper limit compensation gain and the stress compensation gain; Outputting corrected input image data based on the input image data and the target compensation gain; Driving the corresponding pixel based on the corrected input image data, and Further including counting the time during which the light emitting element of the corresponding pixel emits light to output a cumulative driving time, The lower limit compensation gain and the upper limit compensation gain respectively correspond to the cumulative driving time. Further including the step of storing a target compensation gain graph indicating the setting range of the target compensation gain according to the cumulative driving time and the cumulative stress data, The setting range of the target compensation gain includes, in the target compensation gain graph, a timer lower limit line where the lower limit compensation gain is located, a timer upper limit line where the upper limit compensation gain is located, and a gain region surrounded by the timer lower limit line and the timer upper limit line, The stress compensation gain is a driving method of an electroluminescent display device within the gain region.

7. At the first cumulative driving time of the target compensation gain graph, the timer lower limit line and the timer upper limit line have the same first target compensation gain, At the second cumulative driving time of the target compensation gain graph that is more than the first cumulative driving time, the timer lower limit line and the timer upper limit line have the same second target compensation gain, At the third cumulative driving time of the target compensation gain graph between the first cumulative driving time and the second cumulative driving time, the timer lower limit line has a third target compensation gain, and the timer upper limit line has a fourth target compensation gain, The first target compensation gain is 1, the second target compensation gain is 0.5, the third target compensation gain is a first value between 0.5 and 1, and the fourth target compensation gain is a second value between 0.5 and 1, The second value is greater than the first value, The driving method of the electroluminescent display device according to claim 6.

8. The timer lower limit line includes a first lower limit line having a first slope and a second lower limit line having a second slope gentler than the first slope, and the first lower limit line and the second lower limit line are connected to each other via a first inflection point, The timer upper limit line includes a first upper limit line having a third slope and a second upper limit line having a fourth slope gentler than the third slope, and the first upper limit line and the second upper limit line are connected to each other via a second inflection point, The driving method of the electroluminescent display device according to claim 6.

9. The first lower limit line having the first slope intersects the first upper limit line having the third slope at the first cumulative driving time, The second lower limit line having the second slope intersects the second upper limit line having the fourth slope at a second cumulative driving time that is more than the first cumulative driving time, At the first cumulative driving time, the first target compensation gain corresponding to the first lower limit line and the first upper limit line is 1. At the second cumulative driving time, the second target compensation gain corresponding to the second lower limit line and the second upper limit line is 0.

5. The driving method of the electroluminescent display device according to claim 8.

10. A display panel having a plurality of pixels each including a light emitting element, A control unit, And a driving unit, The control unit, Receives input image data for the corresponding pixel among the pixels, Determines cumulative stress data applied to the light emitting element of the corresponding pixel by the accumulation of the image realized in the corresponding pixel during driving, Determines a target compensation gain based on the cumulative stress data, and outputs corrected input image data based on the input image data and the target compensation gain. The driving unit drives the corresponding pixel based on the corrected input image data. The control unit, Determines the cumulative driving time during which the light emitting element of the corresponding pixel emits light, Determines the target compensation gain further based on the cumulative driving time, Determines a lower limit compensation gain and an upper limit compensation gain so as to correspond to the cumulative driving time respectively, Determines a stress compensation gain corresponding to the cumulative stress data, Determines the target compensation gain based on the lower limit compensation gain, the upper limit compensation gain, and the stress compensation gain. Further includes a memory circuit in which a target compensation gain graph showing the setting range of the target compensation gain according to the cumulative driving time and the cumulative stress data is stored. The setting range of the target compensation gain includes, in the target compensation gain graph, a timer lower limit line where the lower limit compensation gain is located, a timer upper limit line where the upper limit compensation gain is located, and a gain region surrounded by the timer lower limit line and the timer upper limit line. The stress compensation gain is within the gain region. An electroluminescent display device.

11. At the first cumulative driving time of the target compensation gain graph, the timer lower limit line and the timer upper limit line have the same first target compensation gain. At the second cumulative driving time of the target compensation gain graph that is more than the first cumulative driving time, the timer lower limit line and the timer upper limit line have the same second target compensation gain. At a third cumulative drive time of the target compensation gain graph that is between the first cumulative drive time and the second cumulative drive time, the timer lower limit line has a third target compensation gain, and the timer upper limit line has a fourth target compensation gain. The first target compensation gain is 1, the second target compensation gain is 0.5, the third target compensation gain is a first value between 0.5 and 1, and the fourth target compensation gain is a second value between 0.5 and 1. The second value is greater than the first value. The electroluminescent display device according to claim 10.

12. The timer lower limit line includes a first lower limit line having a first slope and a second lower limit line having a second slope gentler than the first slope, and the first lower limit line and the second lower limit line intersect at a first inflection point. The timer upper limit line includes a first upper limit line having a third slope and a second upper limit line having a fourth slope gentler than the third slope, and the first upper limit line and the second upper limit line intersect at a second inflection point. The electroluminescent display device according to claim 10.

13. The control unit includes a first look-up table that provides the lower limit compensation gain based on the cumulative drive time, a second look-up table that provides the upper limit compensation gain based on the cumulative drive time, and a third look-up table that provides the stress compensation gain based on the cumulative stress data. The electroluminescent display device according to claim 10.

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