Display device and driving method thereof

Abstract

A display device and a driving method thereof are provided, the display device including: a display panel for displaying an image; and a signal controller for determining whether the input image signal is a still image signal, further determining whether image switching occurs if the input image signal is a still image signal, and determining whether image switching occurs if image switching occurs by using data values of two pieces of frame data between which image switching occurs. Compensating the image data according to the frame data after the image is switched; and a data driver for generating a data signal based on the image data and outputting the data signal to the display panel.

Description

[0001] This application is a divisional application of the invention patent application "Display device and driving method thereof" with application date of October 31, 2019 and application number 201911050191.1. Technical Field

[0002] Exemplary embodiments of the invention relate generally to a display device and a driving method thereof, and more particularly, to a display device and a driving method capable of reducing sticking of a still image. Background Art

[0003] Through the display of the mobile device, the user can view images or use visual content such as games, photo viewing and editing. As the mobile device market continues to expand, the demand for high-resolution displays is also growing.

[0004] In the case of a high-resolution display, a large number of pixels are located in a small area. In addition, in order to reduce the characteristic deviation of each pixel, each pixel includes a plurality of transistors. Therefore, the area occupied by the transistor included in one pixel is also small.

[0005] Depending on the method of applying gate voltage to such a transistor, a hysteresis phenomenon occurs in which the value of the leakage current flowing through the transistor has different values. The hysteresis makes it difficult for the current value passing through the driving transistor of the pixel to reach the target current value, resulting in image retention on the display when the image being displayed is switched to another image.

[0006] The above information disclosed in this Background section is only for understanding the background of the inventive concept and therefore it may contain information that does not constitute the prior art. Summary of the invention

[0007] An apparatus and method constructed according to an exemplary embodiment of the invention suppress image sticking when images are switched.

[0008] Devices and methods constructed according to exemplary embodiments of the invention also provide improvements in display quality of display devices.

[0009] Additional features of the inventive concepts will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the inventive concepts.

[0010] According to an exemplary embodiment, a display device may include: a display panel for displaying an image; a signal controller for determining whether an input image signal is a still image signal, and if the input image signal is a still image signal, further determining whether image switching occurs, and if image switching occurs, compensating image data according to frame data after the image is switched by using data values ​​of two pieces of frame data between which image switching occurs; and a data driver for generating a data signal based on the image data and outputting the data signal to the display panel.

[0011] The signal controller may include an image determining unit configured to compare at least two pieces of frame data adjacent to each other of the input image signal to determine whether the input image signal is a still image signal.

[0012] The image determination unit may receive a panel self refresh (PSR) control signal to control a PSR mode for displaying a still image having an input image signal, and determine whether the input image signal is a still image signal based on the PSR control signal.

[0013] If the image determination unit determines that the input image signal is a still image signal, the image determination unit may compare at least two pieces of frame data adjacent to each other of the input image signal to determine whether image switching occurs.

[0014] If the image determination unit determines that image switching occurs, the image compensation unit of the signal controller can compensate the image data according to the frame data after the image is switched, and can apply a data signal to any pixel included in the display panel corresponding to a grayscale different from the target grayscale based on the frame data after the image is switched.

[0015] The image compensation unit may compensate the image data during a plurality of frame periods after the image is switched.

[0016] The image compensation unit can compensate the image data according to the frame data after the image is switched during multiple frame periods after the image is switched, so that the data signal applied to any pixel corresponds to multiple grayscales different from the target grayscale based on the frame data after the image is switched.

[0017] After the image is switched, the image compensation unit may set the plurality of grayscales to converge to a target grayscale over time.

[0018] According to another exemplary embodiment, a display device may include: a display panel, the display panel including pixels, the pixels including light-emitting elements, the light-emitting elements emitting light based on a driving current corresponding to a data signal applied to a data line; a signal controller for generating image data based on an input image signal; and a data driver for generating a data signal by using the image data, wherein voltage values ​​of the data signals applied to pixels corresponding to the same grayscale are different from each other based on whether a still image displayed by the input image signal is switched.

[0019] The voltage value of the data signal applied to the pixel may increase or decrease from a point in time when the still image is switched.

[0020] The period during which the voltage value of the data signal applied to the pixel increases or decreases may be within 15 seconds.

[0021] The pixel may further include: a first transistor for conducting a driving current according to a voltage difference between a gate of the first transistor and one end of the first transistor; a capacitor for storing a voltage corresponding to a data signal; and a second transistor connected to the data line and activated by a corresponding scan signal to receive the data signal, wherein a voltage value of the data signal applied to a pixel corresponding to the same gray scale is different from a voltage value of the data signal applied to the pixel according to whether a still image displayed by an input image signal is switched.

[0022] According to an exemplary embodiment, a driving method of a display device may include the following steps: determining whether an input image signal is a still image signal; if the input image signal is a still image signal, further determining whether image switching occurs; and if image switching occurs, using data values ​​of two pieces of frame data between which image switching occurs, compensating image data according to frame data after the image is switched.

[0023] The step of further determining whether image switching occurs may include comparing at least two pieces of frame data adjacent to each other of the input image signal to determine whether the input image signal is a still image signal.

[0024] The step of further determining whether image switching occurs may further include receiving a PSR control signal for controlling a PSR mode to display a still image with an input image signal, and determining whether the input image signal is a still image signal based on the PSR control signal.

[0025] The step of further determining whether image switching occurs may further include determining whether the input image signal is a still image signal, and then comparing at least two adjacent pieces of frame data of the input image signal with each other and determining whether image switching occurs.

[0026] The step of compensating the image data may include: if image switching occurs, compensating the image data according to frame data after the image switching occurs, and applying a data signal to any pixel included in the display panel corresponding to a grayscale different from a target grayscale based on the frame data after the image switching occurs.

[0027] The step of compensating the image data may further include compensating the image data for a plurality of frame periods after the image switching occurs.

[0028] The step of compensating the image data for multiple frame periods after image switching occurs may include: compensating the image data for multiple frame periods after image switching occurs according to the frame data after the image switching occurs, and compensating the data signal applied to any pixel included in the display panel corresponding to a grayscale different from a target grayscale based on the frame data after the image switching occurs.

[0029] After image switching occurs, multiple grayscales may be set to be close to the value of the target grayscale over time.

[0030] According to exemplary embodiments, image sticking caused by switching images may be reduced.

[0031] According to exemplary embodiments, the display quality of a display device may be improved.

[0032] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings illustrate exemplary embodiments of the invention and together with the description serve to explain the inventive concept. The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification.

[0034] Figure 1 is a block diagram illustrating a display device constructed according to an exemplary embodiment of the invention.

[0035] Figure 2 It is shown Figure 1 A circuit diagram of a representative pixel of a display device.

[0036] Figure 3 It is shown Figure 1 1 is a block diagram of an exemplary embodiment of a signal controller for a display device.

[0037] Figure 4A and Figure 4B is a diagram of an example in which a display device switches images according to an exemplary embodiment of the invention.

[0038] Figure 5 is a flowchart of an exemplary driving method of a display device according to an exemplary embodiment.

[0039] Figure 6 is a flowchart of an exemplary driving method of a display device according to another exemplary embodiment.

[0040] Figures 7 to 10 is a diagram illustrating application of a data signal to a pixel whose image is switched according to an exemplary driving method of a display device according to an exemplary embodiment.

[0041] Fig.11A , Fig. 11B and Fig.12 are a table and a graph showing current flowing through an organic light emitting diode according to an exemplary driving method of a display device according to an exemplary embodiment. DETAILED DESCRIPTION

[0042] In the following description, for the purpose of illustration, many specific details are set forth to provide a thorough understanding of various exemplary embodiments or implementations of the invention. As used herein, "embodiment" and "implementation" are interchangeable words as non-limiting examples of devices or methods using one or more inventive concepts disclosed herein. However, it is apparent that various exemplary embodiments can be implemented without these specific details or with one or more equivalent arrangements. In other cases, well-known structures and devices are shown in the form of block diagrams to avoid making various exemplary embodiments unnecessarily obscure. In addition, although various exemplary embodiments may be different, they do not have to be exclusive. For example, without departing from the inventive concept, the specific shape, construction and characteristics of the exemplary embodiment may be used for or implemented in another exemplary embodiment.

[0043] Unless otherwise specified, the illustrated exemplary embodiments will be understood as providing exemplary features of the details of variations of some ways in which the inventive concept can be implemented in practice. Therefore, unless otherwise specified, the features, components, modules, layers, films, panels, regions and / or aspects, etc. (hereinafter, individually or collectively referred to as "elements") of the various embodiments can be combined, separated, interchanged and / or rearranged without departing from the inventive concept.

[0044] The use of cross hatching and / or shading is usually provided in the drawings to make the boundaries between adjacent elements clear. Thus, unless otherwise specified, the presence or absence of cross hatching or shading does not express or indicate any preference or requirement for a particular material, material property, size, ratio, commonality between the elements shown, and / or any other characteristics, attributes, properties, etc. of the elements. In addition, in the drawings, the size and relative size of the elements may be exaggerated for the purpose of clarity and / or description. When the exemplary embodiments can be implemented differently, a specific process sequence may be performed in a different order than described. For example, two processes described in succession may be performed substantially simultaneously, or two processes described in succession may be performed in an order opposite to the order described. In addition, the same reference numerals represent the same elements.

[0045] When an element or layer is referred to as being "on" another element or layer, "connected to" or "bonded to" another element or layer, the element or layer may be directly on, directly connected to or directly bonded to the other element or layer, or there may be an intermediate element or intermediate layer. However, when an element or layer is referred to as being "directly on" another element or layer, "directly connected to" or "directly bonded to" another element or layer, there is no intermediate element or intermediate layer. For this reason, the term "connection" may refer to a physical connection, an electrical connection and / or a fluid connection with or without an intermediate element. In addition, the D1 axis, the D2 axis and the D3 axis are not limited to the three axes of a rectangular coordinate system, such as an x-axis, a y-axis and a z-axis, and may be interpreted in a broader sense. For example, the D1 axis, the D2 axis and the D3 axis may be perpendicular to each other, or may represent different directions that are not perpendicular to each other. For the purpose of this disclosure, "at least one of X, Y, and Z" and "at least one selected from the group consisting of X, Y, and Z" may be interpreted as only X, only Y, only Z, or any combination of two or more of X, Y, and Z, such as XYZ, XYY, YZ, and ZZ. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0046] Although the terms "first", "second", etc. may be used herein to describe various types of elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another element. Therefore, without departing from the teachings of the present disclosure, the first element discussed below may be referred to as the second element.

[0047] For descriptive purposes, spatially relative terms such as "under", "below", "below", "down", "above", "up", "above", "higher", "side" (e.g., as in "sidewall"), etc. may be used herein to describe the relationship of one element to another (other) element as shown in the figure. In addition to the orientations depicted in the drawings, spatially relative terms are intended to include different orientations of the device in use, operation and / or manufacture. For example, if the device in the drawings is turned over, the elements described as "under" or "below" other elements or features will subsequently be positioned as "above" the other elements or features. Therefore, the exemplary term "under" may include both above and below orientations. In addition, the device may be positioned otherwise (e.g., rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0048] The terms used here are for the purpose of describing specific embodiments, and are not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms "one (kind / person)" and "the / said" are also intended to include plural forms. In addition, when the terms "comprise", "include" and / or their variations are used in this specification, these terms illustrate the existence of the features, integral bodies, steps, operations, elements, components and / or their groups, but do not exclude the existence or addition of one or more other features, integral bodies, steps, operations, elements, components and / or their groups. It should also be noted that, as used herein, the terms "substantially", "approximately" and other similar terms are used as approximate terms rather than as degree terms, and are used to illustrate the inherent deviations in measured values, calculated values ​​and / or provided values ​​that will be appreciated by those of ordinary skill in the art.

[0049] As is customary in the art, some exemplary embodiments are described and shown in the accompanying drawings in terms of functional blocks, units and / or modules. It will be understood by those skilled in the art that these blocks, units and / or modules are physically implemented by electronic (or optical) circuits (such as logic circuits, discrete components, microprocessors, hard-wired circuits, memory elements, wiring connections, etc.) that can be formed using semiconductor-based manufacturing techniques or other manufacturing techniques. In the case where blocks, units and / or modules are implemented by microprocessors or other similar hardware, they can be programmed and controlled using software (e.g., microcode) to perform the various functions discussed herein, and they can be selectively driven by firmware and / or software. It is also contemplated that each block, unit and / or module can be implemented by dedicated hardware, or can be implemented as a combination of dedicated hardware for performing some functions and processors (e.g., one or more programmed microprocessors and associated circuits) for performing other functions. In addition, without departing from the scope of the inventive concept, each block, unit and / or module of some exemplary embodiments can be physically divided into two or more interacting and discrete blocks, units and / or modules. Furthermore, the blocks, units and / or modules of some exemplary embodiments may be physically combined into more complex blocks, units and / or modules without departing from the scope of the inventive concept.

[0050] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this disclosure is a part. Terms (such as those defined in general dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense, unless expressly defined as such herein.

[0051] Figure 1 is a block diagram illustrating a display device constructed according to an exemplary embodiment.

[0052] Reference Figure 1 , the display device 1000 may include a display panel 100 , a scan driver 110 , a data driver 120 , and a signal controller 130 .

[0053] The display device 1000 may include an organic light emitting device, a liquid crystal display, etc. In addition, the display device 1000 may be a flexible display device, a rollable display device, a curved display device, a transparent display device, and a mirror display device implemented by an organic light emitting device.

[0054] The display panel 100 may include a plurality of pixels PX and may display an image. Specifically, the display panel 100 may include a plurality of pixels PX each connected to a corresponding one of a plurality of scan lines SL1 to SLn and a corresponding one of a plurality of data lines DL1 to DLm.

[0055] The scan driver 110 may provide a scan signal to the pixels PX of the display panel 100 through the scan lines SL1 to SLn. The scan driver 110 may provide the scan signal to the display panel 100 based on the first control signal SCS received from the signal controller 130.

[0056] The data driver 120 may provide a data signal corresponding to the image data DATA to the pixel PX of the display panel 100 through the data lines DL1 to DLm. The data driver 120 may provide the data signal to the display panel 100 based on the second control signal DCS received from the signal controller 130. In an exemplary embodiment, the data driver 120 may include a gamma correction unit (or a gamma voltage generator) for converting the image data DATA into a voltage corresponding to the data signal. The image data DATA of the gray domain may be converted into a data voltage of the voltage domain by the gamma correction unit.

[0057] The signal controller 130 may receive control signals such as an input image signal IS, a data enable signal DE, and a main clock signal MCLK. In addition, when the display device 1000 interacts with an external graphic source through eDP (embedded display port) v1.3 or the like, the display device 1000 may receive a PSR control signal PCS for panel self-refresh (hereinafter referred to as "PSR").

[0058] The PSR command signal may include a PSR start signal for starting the PSR mode, a PSR end signal for ending the PSR mode, and a resynchronization end signal for ending the resynchronization mode, the resynchronization end signal being set at a predetermined interval immediately after the PSR mode ends.

[0059] The signal controller 130 may control driving of the scan driver 110 and the data driver 120. The signal controller 130 may generate a first control signal SCS and a second control signal DCS, and provide the first control signal SCS and the second control signal DCS to the scan driver 110 and the data driver 120, respectively, so as to be able to control the scan driver 110 and the data driver 120. In addition, the signal controller 130 may drive the display device 1000 in a normal mode or a PSR mode based on the PSR control signal PCS.

[0060] Figure 2 is a diagram showing a structure according to an exemplary embodiment Figure 1 A circuit diagram of a pixel of a display device.

[0061] like Figure 2 As shown in , the pixel PX may include a first transistor T1, a second transistor T2, a storage capacitor Cst, and an organic light emitting diode OLED. The pixel PX may be located in an i-th pixel row and a j-th pixel column.

[0062] The first transistor T1 may be a driving transistor. In an exemplary embodiment, the first transistor T1 may include a gate connected to the first node N1, one end connected to the first power voltage ELVDD, and the other end connected to the anode of the organic light emitting diode OLED.

[0063] Drive current I OLED is a current corresponding to a voltage difference between the gate electrode of the first transistor T1 and one end of the first transistor T1 , and may vary corresponding to a data voltage according to a data signal applied through the data line DLj.

[0064] The second transistor T2 may transmit the data signal to the first node N1 according to the level of the i-th scan signal. In an exemplary embodiment, the second transistor T2 may include a gate connected to the i-th scan line SLi, one end connected to the data line DLj, and the other end connected to the first node N1.

[0065] The storage capacitor Cst is connected between the first power voltage ELVDD and the first node N1. In an exemplary embodiment, the storage capacitor Cst may include one end connected to the first power voltage ELVDD and the other end connected to the first node N1.

[0066] The organic light emitting diode OLED can be driven by the driving current I flowing from the first transistor T1. OLED In an exemplary embodiment, the organic light emitting diode OLED may include an anode connected to the other end of the first transistor T1 and a cathode connected to the second power voltage ELVSS.

[0067] Figure 3 It is shown Figure 1 A block diagram of a signal controller of a display device.

[0068] like Figure 3 As shown in , the signal controller 130 may include an image determination unit 131 , an image compensation unit 133 , and a frame memory 135 .

[0069] The image determination unit 131 may receive an input image signal IS and may determine whether the input image signal IS reflects a still image or a moving image. In an exemplary embodiment, the image determination unit 131 may compare at least two pieces of frame data of the input image signal IS to determine whether the input image signal IS is a still image signal or a moving image signal. Here, the at least two pieces of frame data may be adjacent to each other.

[0070] For example, the image determination unit 131 may determine the image quality of a plurality of pieces of frame data (eg, Figure 4A The image determination unit 131 compares at least two pieces of frame data adjacent to each other in F1 to Fk in the image data. Specifically, the image determination unit 131 can compare the first piece of frame data F1 and the second piece of frame data F2. The image determination unit 131 can compare the first data value included in the first frame data (for example, the first data value at a specific position) and the second data value included in the second frame data (for example, the second data value at the specific position). If the difference between the first data value and the second data value (or the size of the difference) is less than a predetermined reference value, the image determination unit 131 can determine that the input image signal IS is a still image signal. If the difference between the first data value and the second data value exceeds a predetermined reference value, the image determination unit 131 can determine that the input image signal IS is a moving image signal.

[0071] As another example, the image determination unit 131 may determine the image quality of a plurality of pieces of frame data (eg, Figure 4B The image determination unit 131 compares the data values ​​of the partial area SA1 in at least two pieces of frame data adjacent to each other in the first piece of frame data (F1 to Fk). For example, the image determination unit 131 can compare the data values ​​of the partial area SA1 in the first piece of frame data F1 and the second piece of frame data F2. Specifically, the determination unit 131 can compare the first data value corresponding to the area SA1 in the first frame data and the second data value corresponding to the area SA1 in the second frame data. If the difference (or the size of the difference) between the first data value and the second data value is less than a predetermined reference value, the image determination unit 131 can determine that the input image signal IS is a still image signal. If the difference between the first data value and the second data value exceeds a predetermined reference value, the image determination unit 131 can determine that the input image signal IS is a moving image signal.

[0072] When the image determination unit 131 receives the PSR control signal PCS, the image determination unit 131 may determine that the PSR mode period is started based on the PSR start signal included in the PSR control signal PCS, and the image determination unit 131 may determine that the input image signal IS received from the external graphic source is a still image signal. When the image determination unit 131 receives the PSR start signal, the image determination unit 131 may store frame data of the received input image signal IS to the frame memory 135.

[0073] If the input image signal IS is a still image or has a still image area, the image determination unit 131 may determine whether image switching occurs in the input image signal IS. For example, similar to the method of determining whether an image is a still image, the image determination unit 131 may compare at least two pieces of frame data of the input image signal IS to determine whether image switching occurs. If the frame data is pre-stored in the frame memory 135 (i.e., when the PSR mode according to the PSR start signal is started), the image determination unit 131 may compare the frame data of the input image signal IS and the frame data pre-stored in the frame memory 135 and determine whether the image is switched.

[0074] Reference Figure 4A and Figure 4B , describes in detail the method of switching images.

[0075] Figure 4A and Figure 4B is a diagram of an example in which a display device switches images according to an exemplary embodiment.

[0076] like Figure 4A As shown, during the period from t1 to t2, the first still image displays a plurality of pieces of frame data F1 to Fk-1 on the display panel 100. The frame data Fk after time t2 is data for displaying a second still image different from the first still image.

[0077] For example, the image determination unit 131 compares the data value included in the frame data Fk-1 with the data value included in the frame data Fk, and if the difference exceeds a predetermined reference value, the image determination unit 131 may determine that the image is switched. That is, the image determination unit 131 may determine whether the image is switched based on the result of comparing the frame data F1 to the frame data Fn included in the input image signal IS.

[0078] As another example, the image determination unit 131 may compare the data value included in the frame data stored in the frame memory 135 with the data value included in the input frame data to determine whether the image is switched. For example, it is assumed that the PSR mode is activated at time t1. The image determination unit 131 stores the received frame data F1 in the frame memory 135 when the PSR mode is activated. In addition, when the data enable signal DE is received from the external graphic source, the image determination unit 131 may compare the frame data Fk at that time with the frame data F1 stored in the frame memory 135 to determine whether the image is switched.

[0079] like Figure 4B As shown, during the period from t1 to t2, the first still image SA1 displays a plurality of pieces of frame data F1 to Fk-1 on a partial area of ​​the display panel 100. The frame data Fk after time t2 is data for displaying a second still image SA2 different from the first still image SA1 in a partial area of ​​the display panel 100. The size of the area where the first still image SA1 is displayed and the size of the area where the second still image SA2 is displayed are not limited, and it is assumed in the following description that the two areas are equal to each other. Figure 4B Examples of image switching include a case in which, after being controlled by a data signal to emit light for displaying a first still image SA1 during a period from t1 to t2 (i.e., during a plurality of frame periods), any pixel PX of the display panel 100 is controlled by the data signal to emit light for displaying a second still image SA2.

[0080] The image determination unit 131 may compare a data value for displaying the first still image SA1 among the data values ​​included in the frame data Fk-1 and a data value for displaying the second still image SA2 among the data values ​​included in the frame data Fk, and if the difference exceeds a predetermined reference value, the image determination unit 131 may determine that the image is switched. That is, the image determination unit 131 may determine whether the image is switched based on the result of comparing the frame data F1 to the frame data Fn included in the input image signal IS.

[0081] The image determination unit 131 may generate image data DATA from the input image signal IS and transmit the image data DATA to the image compensation unit 133. When the image determination unit 131 determines that the image is switched, the image determination unit 131 may output an image compensation control signal to the image compensation unit 133.

[0082] When the image compensation control signal is input to the image compensation unit 133, the image compensation unit 133 compensates the transmitted image data DATA and outputs it to the data driver 120. When the image compensation control signal is not input to the image compensation unit 133, the image compensation unit 133 outputs the transmitted image data DATA to the data driver 120.

[0083] When image switching has occurred such that the pixel for displaying the first gray value actually displays the second gray value, the image compensation unit 133 may compensate the image data DATA to any gray value between the first gray value and the second gray value.

[0084] For example, when image switching has occurred so that the pixel for displaying high grayscale displays low grayscale, the image compensation unit 133 can compensate the image data DATA to an arbitrary grayscale value between high grayscale and low grayscale. At this time, the greater the difference between high grayscale and low grayscale, the greater the arbitrary grayscale value can be. For example, when image switching has occurred so that the pixel for displaying high grayscale 32 displays low grayscale 0, the compensated grayscale level is 3, and when image switching has occurred so that the pixel for displaying high grayscale 48 displays low grayscale 0, the compensated grayscale level is 5.

[0085] As another example, when image switching occurs so that a pixel displaying a low grayscale displays a high grayscale, the image compensation unit 133 can compensate the image data DATA to an arbitrary grayscale value between the high grayscale and the low grayscale. At this time, the greater the difference between the high grayscale and the low grayscale, the smaller the arbitrary grayscale value can be. For example, when image switching has occurred so that a pixel displaying a low grayscale of 16 displays a high grayscale of 48, the compensated grayscale level is 46, and when image switching has occurred so that a pixel displaying a low grayscale of 32 displays a high grayscale of 48, the compensated grayscale level is 47.

[0086] The image compensation unit 133 may include a predetermined compensation lookup table LUT according to physical characteristics of the display panel 100. The image compensation unit 133 may compensate the image data DATA by referring to the compensation lookup table LUT. An example of the lookup table LUT is shown in Table 1 below.

[0087] Table 1

[0088] If the grayscale value of the data signal input to the pixel PX in the K-1 frame is 32 and the grayscale value of the data signal input to the pixel PX in the K frame is 0, the image compensation unit 133 can compensate the grayscale value of the data signal input to the pixel PX to 3 (a value between 32 and 0).

[0089] If the grayscale value of the data signal input to the pixel PX in the K-1 frame is 32 and the grayscale value of the data signal input to the pixel PX in the K frame is 48, the image compensation unit 133 can compensate the grayscale value of the data signal input to the pixel PX to 47 (a value between 48 and 32).

[0090] Next, refer to Figure 5 , a method of driving a display device according to an exemplary embodiment is described in detail.

[0091] Figure 5 is a flowchart of a method for driving a display device according to an exemplary embodiment. Figure 5 In the embodiment, it is assumed that the signal controller 130 does not receive the PSR control signal separately.

[0092] The image determination unit 131 of the signal controller 130 receives an input image signal IS ( S100 ).

[0093] Next, the image determination unit 131 determines whether the input image signal IS is a still image signal ( S110 ).

[0094] If the input image signal IS is a still image signal, the image determination unit 131 determines whether the image is switched in the input image signal IS (S120). If the image switching has occurred in the input image signal IS, the image determination unit 131 may generate image data DATA using the input image signal IS and output an image compensation control signal to the image compensation unit 133.

[0095] Then, the image compensation unit 133 compensates the image data DATA after the image is switched (S130). At this time, the image compensation unit 133 may compensate the image data DATA before the image is switched and may compensate the image data DATA after the image is switched.

[0096] The image compensation unit 133 outputs the compensated image data DATA to the data driver 120 ( S140 ).

[0097] If it is determined in step S110 that the input image signal IS is not a still image signal or if it is determined in step S120 that image switching does not occur in the input image signal IS, the image determination unit 131 generates image data DATA using the input image signal IS, and the image compensation unit 133 outputs the image data DATA to the data driver 120 (S140).

[0098] Next, refer to Figure 6 , a method of driving a display device according to an exemplary embodiment is described in detail.

[0099] Figure 6 is a flowchart of a method for driving a display device according to another exemplary embodiment. Figure 6 In the embodiment, it is assumed that the signal controller 130 receives the PSR control signal alone.

[0100] The image determination unit 131 of the signal controller 130 receives an input image signal IS ( S200 ).

[0101] Next, the image determination unit 131 determines whether the input image signal IS is a still image signal according to the PSR control signal PCS ( S210 ).

[0102] If the input image signal IS is a still image signal, the image determination unit 131 determines whether the image is switched in the input image signal IS (S220). If the image switching has occurred in the input image signal IS, the image determination unit 131 may generate image data DATA using the input image signal IS and output an image compensation control signal to the image compensation unit 133.

[0103] Then, the image compensation unit 133 compensates the image data DATA after the image is switched (S230). At this time, the image compensation unit 133 may compensate the image data DATA before the image is switched and may compensate the image data DATA after the image is switched.

[0104] The image compensation unit 133 outputs the compensated image data DATA to the data driver 120 ( S240 ).

[0105] If it is determined in step S210 that the input image signal IS is not a still image signal or if it is determined in step S220 that image switching does not occur in the input image signal IS, the image compensation unit 133 outputs the image data DATA generated using the input image signal IS to the data driver 120 (S240).

[0106] Next, refer to Figures 7 to 10 , describes the data signal applied to any pixel PX when the image is switched.

[0107] Figures 7 to 10 is a diagram illustrating application of a data signal to a pixel whose image is switched according to a driving method of a display device according to an exemplary embodiment.

[0108] exist Figures 7 to 10 In the present invention, during the display period in which a still image is displayed, the same data signal Vdata is applied to the pixel PX for each frame. However, when the still image starts to be displayed, the data signal Vdata is not applied in some frames.

[0109] exist Figures 7 to 10 In the present embodiment, the image is switched, and thus in order to display the second gray scale, the second voltage V2 is applied to the pixel PX which displayed the first gray scale by applying the first voltage V1 before the image switching (first gray scale<second gray scale).

[0110] like Figure 7 As shown in , during the period from the first frame F1 to the k-1th frame Fk-1, the data signal Vdata applied to the pixel PX may be a first voltage V1. When image switching occurs in the k-th frame Fk, the data signal Vdata applied to the pixel PX may be a second voltage V2. The first voltage V1 is a voltage for displaying a low gray scale, the second voltage V2 is a voltage for displaying a high gray scale, and the first voltage V1 is higher than the second voltage V2. After the image is switched, the data signal Vdata of the second voltage V2 is applied to the pixel PX until the n-th frame Fn.

[0111] like Figure 8 As shown in , during the period from the first frame F1 to the i-1 frame Fi-1, the data signal Vdata applied to the pixel PX may be the first voltage V1. When image switching occurs in the i-th frame Fi, the image compensation unit 133 may compensate the image data DATA so that the data signal Vdata applied to the pixel PX has a voltage corresponding to a grayscale between a first grayscale according to the first voltage V1 and a second grayscale according to the second voltage V2. The data signal Vdata applied to the pixel PX in the i-th frame Fi may be a third voltage V3. The third voltage V3 may be a voltage corresponding to any grayscale between the first grayscale and the second grayscale.

[0112] The data signal Vdata of the third voltage V3 may be applied to the pixel PX during at least one period of the frame Fi to Fj-1. The period of Fi to Fj-1 may be within 15 seconds, but is not limited thereto. When the difference between the first grayscale and the second grayscale is greater, the period of Fi to Fj-1 may have a greater value, but is not limited thereto.

[0113] When the period of the frame Fi to the frame Fj-1 passes, the data signal Vdata of the second voltage V2 is applied to the pixel PX from the j-th frame Fj to the n-th frame Fn.

[0114] In addition, if Fig. 9 As shown in FIG. 1 , during the period from the first frame F1 to the i-1th frame Fi-1, the data signal Vdata applied to the pixel PX may be the first voltage V1. When image switching occurs in the i-th frame Fi, the image compensation unit 133 may compensate the image data DATA so that the data signal Vdata applied to the pixel PX has a voltage corresponding to a grayscale level between the first grayscale and the second grayscale.

[0115] Specifically, the image compensation unit 133 may set the intermediate gray level between the first gray and the second gray to a decimal rather than an integer. In this case, the plurality of frames may be regarded as one unit, and some of the plurality of frames corresponding to one unit may be emitted as the first intermediate gray, and the remaining frames of the plurality of frames corresponding to one unit may be emitted as the second intermediate gray. Fig. 9 In the example, the data signal Vdata applied to the pixel PX in the i-th frame Fi to the i+2-th frame Fi+2 (e.g., Fi to Fi+2) among the four frames corresponding to one unit may be the first intermediate voltage Va, and the data signal Vdata applied to the pixel PX in the i+3-th frame Fi+3 may be the second intermediate voltage Vb. If the intermediate gray level is a decimal (e.g., 47.75) rather than an integer, four frames are repeated as a unit, the data signal of the first intermediate voltage (corresponding to 48 grays) may be applied to three of the four frames, and the data signal of the second intermediate voltage (corresponding to 47 grays) may be applied to the remaining one frame.

[0116] In the above, four frames as one unit are an example. The number of the intermediate voltages may also be two or more, and the order of the frames in which the second intermediate voltage Vb is applied among the four frames is not limited.

[0117] Then, four frames may be repeated until the j-th frame Fj, at which the data signal Vdata of the second voltage V2 is applied.

[0118] like Fig.10 As shown in , during the period from the first frame F1 to the i-1 frame Fi-1, the data signal Vdata applied to the pixel PX may be the first voltage V1. When image switching occurs in the i-th frame Fi, the image compensation unit 133 may compensate the image data DATA so that the data signal Vdata applied to the pixel PX has a voltage corresponding to a grayscale between the first grayscale and the second grayscale. The data signal Vdata applied to the pixel PX in the i-th frame Fi may be a fourth voltage V4. The fourth voltage V4 may be a voltage corresponding to any grayscale between the first grayscale and the second grayscale.

[0119] The data signal Vdata of the fourth voltage V4 may be applied to the pixel PX during at least one period of the frames Fi to Fj-1. When the period of Fi to Fj-1 passes, the image data DATA may be compensated to have a voltage corresponding to a third grayscale between the fourth grayscale and the second grayscale. The data signal Vdata applied to the pixel PX in the j-th frame Fj may be the third voltage V3. The data signal Vdata of the third voltage V3 may be applied to the pixel PX during at least one frame period of Fj to Fl-1.

[0120] Since the third grayscale and the fourth grayscale are grayscales between the first grayscale and the second grayscale, when the third grayscale is stored in the LUT, the fourth grayscale can be calculated by interpolation. Since any method known in the art can be used, the description of the interpolation method is omitted.

[0121] In addition, the length of the period from Fi to Fj-1 and the length of the period from Fj to Fl-1 may be the same as or different from each other. The length of the period from Fi to Fj-1 and the length of the period from Fj to Fl-1 may be determined by considering at least one of the difference between the first grayscale and the fourth grayscale, the difference between the fourth grayscale and the third grayscale, and the difference between the third grayscale and the second grayscale, but is not limited thereto.

[0122] When the period Fj to F1-1 passes, the data signal Vdata of the second voltage V2 is applied to the pixel PX from the 1st frame F1 to the nth frame Fn.

[0123] exist Fig.10 In the embodiment, the data signal corresponding to the second grayscale is compensated by the data signal corresponding to the third grayscale and the data signal corresponding to the fourth grayscale, but the data signal corresponding to the second grayscale may be compensated by the data signal corresponding to a plurality of grayscales, and the number of grayscales used for compensation is not limited. In another embodiment, the data signal corresponding to the second grayscale is compensated by the data signal corresponding to the fifth grayscale, the data signal corresponding to the fourth grayscale, and the data signal corresponding to the third grayscale, and the data signals may be sequentially output from the data driver 120 (first grayscale < fifth grayscale < fourth grayscale < third grayscale < second grayscale).

[0124] Fig.11A , Fig. 11B and Fig.12 are a table and a graph showing current flowing through an organic light emitting diode according to a driving method of a display device according to an exemplary embodiment.

[0125] Fig.11A 1 is a graph showing the voltage value of the data signal Vdata and the driving current I applied to the pixel PX when the image is switched from 0 gray to 48 gray. OLED A table of values ​​of Fig. 11B 2 is a graph showing the voltage value of the data signal Vdata and the driving current I applied to the pixel PX when the image is switched from 255 grayscale to 48 grayscale. OLED A table of values.

[0126] Reference Fig.11A and Fig.12 In the BTG1 curve, when the image switches from 0 gray to 48 gray (target gray), if the value of the data signal Vdata applied to the pixel PX is 5.35V corresponding to 48 gray, the driving current I OLEDThe value of is a very high value such as 377pA or 343pA due to the hysteresis of the transistor. Therefore, image sticking due to switching images occurs. After 17 seconds, the driving current I OLED The value of converges to 301 pA (ie, the value of the target drive current corresponding to the data signal Vdata of 5.35 V).

[0127] Reference Fig.11A and Fig.12 BTG2 curve, when the image switches from 0 gray to 48 gray, if the value of the data signal Vdata applied to the pixel PX is 5.4V corresponding to 43 gray (0.1 second) by compensating the image data DATA, the driving current I OLED The value of has a target value such as 312 pA due to the hysteresis of the transistor. Then, the data signal Vdata corresponding to the gray scale of 44 to 47 is sequentially applied to the pixel PX so that the driving current I OLED The deviation from the target driving current value is reduced. As a result, image sticking caused by switching images can be improved.

[0128] Reference Fig. 11B and Fig.12 In the WTG1 curve, when the image switches from 255 grayscale to 48 grayscale (target grayscale), if the value of the data signal Vdata applied to the pixel PX is 5.35V corresponding to 48 grayscale, the driving current I OLED The value of has a very low value, such as 239 pA or 257 pA, due to the hysteresis of the transistor. Therefore, image sticking due to switching images occurs. After 16 seconds, the driving current I OLED The value of converges to 280 pA (ie, the value of the target drive current corresponding to the data signal Vdata of 5.35 V).

[0129] Reference Fig. 11B and Fig.12 In the WTG2 curve, when the image is switched from 255 grayscale to 48 grayscale, if the value of the data signal Vdata applied to the pixel PX is 5.31V corresponding to 51 grayscale (0.1 second) by compensating the image data DATA, the driving current I OLED The value of has a target value such as 272 pA due to the hysteresis of the transistor. Then, the data signal Vdata corresponding to the 49 gray scale is sequentially applied to the pixel PX so that the driving current I OLED The deviation from the target driving current value is reduced. Therefore, image sticking caused by switching images can be improved.

[0130] Although certain exemplary embodiments and implementations have been described herein, other embodiments and modifications will be apparent from this description. Therefore, the inventive concept is not limited to these embodiments, but is defined by the broader scope of the appended claims and various obvious modifications and equivalent arrangements that will be apparent to those of ordinary skill in the art.

Claims

1. A display device, comprising: A display panel for displaying an image, the display panel comprising pixels, the pixels comprising light emitting elements, the light emitting elements emitting light based on a driving current corresponding to a data signal applied to a data line; a signal controller, configured to generate image data according to an input image signal corresponding to the image; as well as a data driver for generating the data signal by using the input image signal, wherein voltage values ​​of data signals applied to pixels corresponding to the same grayscale are different from each other based on whether a still image displayed by the input image signal corresponding to the image is switched from the first still image to the second still image based on whether a difference between the first still image and the second still image exceeds a reference value, The pixel further includes: a first transistor for conducting a driving current according to a voltage difference between a gate of the first transistor and one end of the first transistor; a capacitor for storing a voltage corresponding to the data signal; and a second transistor connected to the data line and activated by a corresponding scan signal to receive the data signal.

2. The display device according to claim 1, wherein: The voltage value of the data signal applied to the pixel increases or decreases from a time point when the still image is switched.

3. The display device according to claim 2, wherein: A period during which the voltage value of the data signal applied to the pixel increases or decreases is within 15 seconds.

4. A method for driving a display device for displaying an image, the method comprising the following steps: comparing at least two pieces of frame data adjacent to each other of the input image signal to determine whether the input image signal corresponding to the image is a still image signal, and when the input image signal is a still image signal, determining whether an image switch from a first still image to a second still image occurs; as well as When the image switching from the first still image to the second still image occurs, the image data corresponding to the second still image is compensated according to the frame data after the image switching using the data values ​​of the two pieces of frame data between which the image switching occurs.

5. The driving method according to claim 4, wherein: The step of comparing at least two adjacent pieces of frame data of the input image signal comprises: A panel self-refresh control signal is received to control a self-refresh mode for displaying a still image having an input image signal, and it is determined whether the input image signal is a still image signal based on the panel self-refresh control signal.

6. The driving method according to claim 4, wherein: The step of comparing at least two adjacent pieces of frame data of the input image signal comprises: The input image signal is determined to be a still image signal, and then at least two pieces of adjacent frame data of the input image signal are compared to determine whether the image switching occurs.

7. The driving method according to claim 6, wherein: The step of compensating the image data comprises: When the image switching occurs, the image data is compensated according to the frame data after the image switching occurs, and a data signal is applied to pixels included in a display panel corresponding to a grayscale different from a target grayscale based on the frame data after the image switching occurs.

8. The driving method according to claim 7, wherein: The step of compensating the image data further comprises: The image data is compensated for a plurality of frame periods after the image switching occurs.

9. The driving method according to claim 8, wherein: The step of compensating the image data in a plurality of frame periods after the image switching occurs comprises: After the image switching occurs, the image data is compensated for multiple frame periods according to the frame data after the image switching occurs, and the data signal applied to the pixel included in the display panel is compensated corresponding to a grayscale different from a target grayscale based on the frame data after the image switching occurs.

10. The driving method according to claim 9, wherein: After the image switching occurs, a plurality of grayscales are set to be close in value to the target grayscale over time.

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