Patent Publication Number: US-2022223114-A1

Title: Tiled display device having a plurality of display panels

Description:
This application claims priority to Korean Patent Application No. 10-2021-0002570, filed on Jan. 8, 2021, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which in its entirety is herein incorporated by reference. 
     BACKGROUND 
     1. Field 
     Embodiments of the invention relate to a display device, and more particularly to a tiled display device including a plurality of display panels coupled to each other. 
     2. Description of the Related Art 
     To overcome a resolution limitation and a size limitation of a single display panel, a tiled display device implemented by coupling a plurality of display panels has been developed. In such a tiled display device, a boundary line (or a seam line) between the plurality of display panels may be viewed or perceived by a user. Accordingly, a tiled display device where a scattering lens is disposed on the boundary line to prevent the boundary line from being perceived has been developed. 
     SUMMARY 
     In a tiled display device where a scattering lens is disposed on a boundary line between a plurality of display panels therein to prevent the boundary line from being perceived, an image may be blurred in a region adjacent to the scattering lens, and an alignment error between the display panels may occur. 
     Embodiments of the invention provide a tiled display device capable of preventing a boundary line between a plurality of display panels from being perceived. 
     According to an embodiment, a tiled display device includes a plurality of display panels coupled to each other, where each of the plurality of display panels includes an edge region adjacent to a boundary line between the plurality of display panels, and a panel driver which multiplies input gray levels of input image data for the plurality of display panels by an adaptive gain, generates boundary compensated image data by adding boundary compensation gray levels to the input gray levels multiplied by the adaptive gain for the edge region, and drives the plurality of display panels based on the boundary compensated image data. In such an embodiment, the adaptive gain is gradually decreased over a plurality of frame periods in a case where a sum of each of the input gray levels for the edge region and a corresponding one of the boundary compensation gray levels exceeds a maximum gray level. 
     In an embodiment, the adaptive gain may have a value greater than 0 and less than or equal to 1. 
     In an embodiment, the adaptive gain may have a single value with respect to an entire region of the plurality of display panels. 
     In an embodiment, the adaptive gain after the plurality of frame periods may be gradually decreased along a direction from a center region of each of the plurality of display panels to the edge region. 
     In an embodiment, the adaptive gain with respect to a center region of each of the plurality of display panels may be decreased by a first amount over the plurality of frame periods, and the adaptive gain with respect to the edge region of each of the plurality of display panels may be decreased by a second amount greater than the first amount over the plurality of frame periods. 
     In an embodiment, the panel driver may include an adaptive gain control block which multiplies the input gray levels for the plurality of display panels by the adaptive gain, and an edge region boosting block which generates the boundary compensated image data by adding the boundary compensation gray levels to the input gray levels multiplied by the adaptive gain for the edge region. 
     In an embodiment, in a case where the sum of each of the input gray levels for the edge region and the corresponding one of the boundary compensation gray levels is less than or equal to the maximum gray level, the adaptive gain control block may determine the adaptive gain as 1. In such an embodiment, in a case where the sum of each of the input gray levels for the edge region and the corresponding one of the boundary compensation gray levels is greater than the maximum gray level, the adaptive gain control block may determine a target gain in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level, and may gradually decrease the adaptive gain to the target gain over the plurality of frame periods. 
     In an embodiment, the adaptive gain control block may count a number of pixels in the edge region for which the sum of the input gray level and the boundary compensation gray level exceeds the maximum gray level. In a case where the counted number is less than a reference number, the adaptive gain control block may determine the adaptive gain as 1. In such an embodiment, in a case where the counted number is greater than or equal to the reference number, the adaptive gain control block may determine a target gain in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level, and may gradually decrease the adaptive gain to the target gain over the plurality of frame periods. 
     In an embodiment, the adaptive gain control block may count a number of pixels in the edge region for which the sum of the input gray level and the boundary compensation gray level exceeds the maximum gray level, and may calculate a ratio of the counted number to a total pixel number in the edge region. In a case where the calculated ratio is less than a reference ratio, the adaptive gain control block may determine the adaptive gain as 1. In such an embodiment, in a case where the calculated ratio is greater than or equal to the reference ratio, the adaptive gain control block may determine a target gain s in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level, and may gradually decrease the adaptive gain to the target gain over the plurality of frame periods. 
     In an embodiment, the adaptive gain control block may determine sums of the input gray levels for the edge region and the boundary compensation gray levels exceeding the maximum gray level, and may calculate differences between the sums exceeding the maximum gray level and the maximum gray level. In a case where a sum of the differences is less than a reference value, the adaptive gain control block may determine the adaptive gain as 1. In such an embodiment, in a case where the sum of the differences is greater than or equal to the reference value, the adaptive gain control block may determine a target gain in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level, and may gradually decrease the adaptive gain to the target gain over the plurality of frame periods. 
     In an embodiment, the panel driver may further include a compensation gray lookup table which stores the boundary compensation gray levels corresponding to respective gray levels. In such an embodiment, the edge region boosting block may determine the boundary compensation gray levels corresponding to the input gray levels multiplied by the adaptive gain by using the compensation gray lookup table, and may generate the boundary compensated image data by adding the boundary compensation gray levels to the input gray levels multiplied by the adaptive gain for the edge region. 
     In an embodiment, the panel driver may further include a compensation data memory which stores mura compensation data, and a mura compensating block which corrects the boundary compensated image data based on the mura compensation data. 
     In an embodiment, the panel driver may receive test data from a test device, may add the boundary compensation gray levels to the test data for the edge region, and may drive the plurality of display panels based on the test data to which the boundary compensation gray levels are added. In such an embodiment, the mura compensation data may be generated by capturing an image displayed by the plurality of display panels based on the test data to which the boundary compensation gray levels are added. 
     According to an embodiment, a tiled display device includes a plurality of display panels coupled to each other, where each of the plurality of display panels includes an edge region adjacent to a boundary line between the plurality of display panels, a data driver which provides data signals to the plurality of display panels, a gate driver which provides gate signals to the plurality of display panels, and a controller which controls the data driver and the gate driver. In such an embodiment, the controller includes an adaptive gain control block which multiplies input gray levels of input image data for the plurality of display panels by an adaptive gain, and an edge region boosting block which generates boundary compensated image data by adding boundary compensation gray levels to the input gray levels multiplied by the adaptive gain for the edge region, and provides the boundary compensated image data to the data driver. In such an embodiment, the adaptive gain is gradually decreased over a plurality of frame periods in a case where a sum of each of the input gray levels for the edge region and a corresponding one of the boundary compensation gray levels exceeds a maximum gray level. 
     In an embodiment, the adaptive gain may have a single value with respect to an entire region of the plurality of display panels. 
     In an embodiment, the adaptive gain after the plurality of frame periods may be gradually decreased along a direction from a center region of each of the plurality of display panels to the edge region. 
     In an embodiment, the adaptive gain with respect to a center region of each of the plurality of display panels may be decreased by a first amount over the plurality of frame periods, and the adaptive gain with respect to the edge region of each of the plurality of display panels may be decreased by a second amount greater than the first amount over the plurality of frame periods. 
     In an embodiment, the controller may further include a compensation gray lookup table which stores the boundary compensation gray levels corresponding to respective gray levels. In such an embodiment, the edge region boosting block may determine the boundary compensation gray levels corresponding to the input gray levels multiplied by the adaptive gain by using the compensation gray lookup table, and may generate the boundary compensated image data by adding the boundary compensation gray levels to the input gray levels multiplied by the adaptive gain for the edge region. 
     According to an embodiment, a tiled display device includes a plurality of display panels coupled to each other, where each of the plurality of display panels includes an edge region adjacent to a boundary line between the plurality of display panels, a data driver which provides data signals to the plurality of display panels, a gate driver which provides gate signals to the plurality of display panels, a compensation data memory which stores mura compensation data, and a controller which control the data driver and the gate driver. In such an embodiment, the controller includes an adaptive gain control block which multiplies input gray levels of input image data for the plurality of display panels by an adaptive gain, an edge region boosting block which generates boundary compensated image data by adding boundary compensation gray levels to the input gray levels multiplied by the adaptive gain for the edge region, and a mura compensating block which corrects the boundary compensated image data based on the mura compensation data, and provides the boundary compensated image data corrected based on the mura compensation data to the data driver. In such an embodiment, the adaptive gain is gradually decreased over a plurality of frame periods in a case where a sum of each of the input gray levels for the edge region and a corresponding one of the boundary compensation gray levels exceeds a maximum gray level. 
     In an embodiment, the controller may receive test data from a test device, and may add the boundary compensation gray levels to the test data for the edge region. In such an embodiment, the mura compensation data may be generated by capturing an image displayed by the plurality of display panels based on the test data to which the boundary compensation gray levels are added. 
     In embodiments of the invention, As described herein, a tiled display device may multiply input gray levels of input image data for a plurality of display panels coupled to each other by an adaptive gain, may generate boundary compensated image data by adding boundary compensation gray levels to the input gray levels (multiplied by the adaptive gain) for an edge region adjacent to a boundary line between the plurality of display panels, and may drive the plurality of display panels based on the boundary compensated image data. In such embodiments, the adaptive gain may be gradually decreased over a plurality of frame periods in a case where a sum of each of the input gray levels for the edge region and a corresponding one of the boundary compensation gray levels exceeds a maximum gray level. Accordingly, in such embodiments of the tiled display device, the boundary line between the plurality of display panels may be effectively prevented from being perceived. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative, non-limiting embodiments will be more clearly understood from the following detailed description in conjunction with the accompanying drawings. 
         FIG. 1  is a block diagram illustrating a tiled display device according to an embodiment. 
         FIG. 2  is a diagram for describing an embodiment of an edge region boosting operation (or a seam side boosting operation) that increases input gray levels for an edge region. 
         FIG. 3  is a diagram illustrating an embodiment of an image of a conventional tiled display device and an example of an image that is compensated by an edge region boosting operation (or a seam side boosting operation). 
         FIG. 4  is a diagram illustrating an embodiment of an image where a sum of an input gray level and a boundary compensation gray level exceeds a maximum gray level. 
         FIG. 5  is a diagram for describing an embodiment where an adaptive gain is gradually decreased over a plurality of frame periods in a tiled display device according to an embodiment. 
         FIG. 6  is a diagram for describing an alternative embodiment where an adaptive gain is gradually decreased over a plurality of frame periods in a tiled display device according to an embodiment. 
         FIG. 7  is a flowchart illustrating a method of operating a tiled display device according to an embodiment. 
         FIG. 8  is a flowchart illustrating a method of operating a tiled display device according to an alternative embodiment. 
         FIG. 9  is a flowchart illustrating a method of operating a tiled display device according to another alternative embodiment. 
         FIG. 10  is a flowchart illustrating a method of operating a tiled display device according to another alternative embodiment. 
         FIG. 11  is a block diagram illustrating a tiled display device according to an alternative embodiment. 
         FIG. 12  is a block diagram illustrating an embodiment of a test device that generates mura compensation data for a tiled display device of  FIG. 11 . 
         FIG. 13  is a flowchart illustrating a method of operating a tiled display device according to an embodiment. 
         FIG. 14  is a block diagram illustrating an electronic device including a tiled display device according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, “a first element,” “component,” “region,” “layer” or “section” discussed below could be termed a second element, component, region, layer or section without departing from the teachings herein. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, “a”, “an,” “the,” and “at least one” do not denote a limitation of quantity, and are intended to include both the singular and plural, unless the context clearly indicates otherwise. For example, “an element” has the same meaning as “at least one element,” unless the context clearly indicates otherwise. “At least one” is not to be construed as limiting “a” or “an.” “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element&#39;s relationship to another element as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The term “lower,” can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The terms “below” or “beneath” can, therefore, encompass both an orientation of above and below. 
     “About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ±30%, 20%, 10% or 5% of the stated value. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims. 
     Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a block diagram illustrating a tiled display device according to an embodiment,  FIG. 2  is a diagram for describing an embodiment of an edge region boosting operation (or a seam side boosting operation) that increases input gray levels for an edge region,  FIG. 3  is a diagram illustrating an embodiment of an image of a conventional tiled display device and an embodiment of an image that is compensated by an edge region boosting operation (or a seam side boosting operation),  FIG. 4  is a diagram illustrating an embodiment of an image where a sum of an input gray level and a boundary compensation gray level exceeds a maximum gray level,  FIG. 5  is a diagram for describing an example where an adaptive gain is gradually decreased over a plurality of frame periods in a tiled display device according to an embodiment, and  FIG. 6  is a diagram for describing an alternative embodiment where an adaptive gain is gradually decreased over a plurality of frame periods in a tiled display device according to an embodiment. 
     Referring to  FIG. 1 , an embodiment of a tiled display device  100  according to the invention may include a plurality of display panels  112 ,  114 ,  116  and  118  coupled to each other and a panel driver  120  that drives the plurality of display panels  112 ,  114 ,  116  and  118 . In an embodiment, the panel driver  120  may include a data driver  130  that provides data signals DS to the plurality of display panels  112 ,  114 ,  116  and  118 , a gate driver  140  that provides gate signals GS to the plurality of display panels  112 ,  114 ,  116  and  118 , and a controller  150  that controls the data driver  130  and the gate driver  140 . 
     The plurality of display panels  112 ,  114 ,  116  and  118  may be coupled, combined or attached to each other. In such an embodiment where the tiled display device  100  includes the plurality of display panels  112 ,  114 ,  116  and  118  coupled to each other, the tiled display device  100  may have a greater resolution and a larger size compared with a display device having a single display panel.  FIG. 1  illustrates one embodiment where the tiled display device  100  includes 2×2 display panels  112 ,  114 ,  116  and  118 , but not being limited thereto. In such an embodiment, the tiled display device  100  may include any number of two or more display panels  112 ,  114 ,  116  and  118 . 
     In an embodiment, each display panel  112 ,  114 ,  116  and  118  may include a plurality of data lines, a plurality of gate lines, and a plurality of pixels coupled to the plurality of data lines and the plurality of gate lines. In an embodiment, each pixel may include a switching transistor, and a liquid crystal capacitor coupled to the switching transistor, and each display panel  112 ,  114 ,  116  and  118  may be a liquid crystal display (“LCD”) panel. In an alternative embodiment, each pixel may include at least two transistors, at least one capacitor and a light emitting diode, such as an organic light emitting diode (“OLED”), and each display panel  112 ,  114 ,  116  and  118  may be a light emitting diode display panel, such as an OLED display panel. However, each display panel  112 ,  114 ,  116  and  118  is not limited to the LCD panel and the OLED display panel. 
     The data driver  130  may generate the data signals DS based on boundary compensated image data BCDAT and a data control signal DCTRL received from the controller  150 , and may provide the data signals DS to the plurality of pixels through the plurality of data lines. In one embodiment, for example, the data control signal DCTRL may include, but not limited to, an output data enable signal, a data clock signal and a load signal. In an embodiment, as illustrated in  FIG. 1 , the data driver  130  may be implemented with (or defined by) one or more data driver integrated circuits (“IC”s)  132 ,  134 ,  136  and  138 . In an embodiment, the data driver ICs  132 ,  134 ,  136  and  138  may be mounted directly on the plurality of display panels  112 ,  114 ,  116  and  118  in a chip on glass (“COG”) manner or a chip on plastic (“COP)” manner, or may be mounted on a flexible film coupled to the plurality of display panels  112 ,  114 ,  116  and  118  in a chip on film (“COF”) manner. In an alternative embodiment, the data driver  130  may be integrated in a peripheral portion of each display panel  112 ,  114 ,  116  and  118 . 
     The gate driver  140  may generate the gate signals GS based on a gate control signal GCTRL received from the controller  150 , and may sequentially provide the gate signals GS to the plurality of pixels on a row-by-row basis through the plurality of gate lines. In an embodiment, the gate control signal GCTRL may include, but not limited to, a gate start signal and a gate clock signal. In an embodiment, the gate driver  140  may be implemented with an amorphous silicon gate (“ASG”) driver that is integrated in a peripheral portion of each display panel  112 ,  114 ,  116  and  118 . In an embodiment, as illustrated in  FIG. 1 , the gate driver  140  may be implemented with one or more gate driver ICs  142 ,  144 ,  146  and  148 . In an embodiments, the gate driver ICs  142 ,  144 ,  146  and  148  may be mounted directly on the plurality of display panels  112 ,  114 ,  116  and  118  in the COG manner or the COP manner, or may be mounted on a flexible film coupled to the plurality of display panels  112 ,  114 ,  116  and  118  in the COF manner. 
     The controller  150  (e.g., a timing controller) may receive input image data IDAT and a control signal CTRL from an external host processor (e.g., a graphic processing unit (“GPU”), an application processor (“AP”), or a graphic card). In an embodiment, the input image data IDAT may be RGB image data including red image data, green image data and blue image data. In an embodiment, the control signal CTRL may include, but not limited to, a vertical synchronization signal, a horizontal synchronization signal, an input data enable signal, a master clock signal, etc. In an embodiment, the controller  150  may generate the boundary compensated image data BCDAT by performing an edge region boosting operation (or a seam side boosting operation) on the input image data IDAT, and may generate the data control signal DCTRL and the gate control signal GCTRL based on the control signal CTRL. In such an embodiment, the controller  150  may control an operation of the data driver  130  by providing the data control signal DCTRL and the boundary compensated image data BCDAT to the data driver  130 , and may control an operation of the gate driver  140  by providing the gate control signal GCTRL to the gate driver  140 . 
     In an embodiment of the tiled display device  100  according the invention, a boundary line BL (or a seam line) may exist (or be defined) between the plurality of display panels  112 ,  114 ,  116  and  118 . In the boundary line BL, no pixel may exist, and an image is not displayed. Thus, in such an embodiment of the tiled display device  100 , the boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be viewed or perceived by a user. In such an embodiment, the panel driver  120  of the tiled display device  100  may perform an edge region boosting operation that increases gray levels (hereinafter, referred to as input gray levels) of the input image data IDAT for an edge region ER adjacent to the boundary line BL in a display region of each display panel  112 ,  114 ,  116  and  118  where the plurality of pixels are disposed to prevent the boundary line BL from being perceived. In an embodiment, the boundary line BL may be referred to as a seam line, the edge region ER adjacent to the boundary line BL may be referred to as a seam side, and the edge region boosting operation may be referred to as a seam side boosting (“SSB”) operation. 
     By the edge region boosting operation, the input gray levels for the edge region ER may be increased, and thus the boundary compensated image data BCDAT representing non-increased input gray levels for the display region other than the edge region ER and increased input gray levels for the edge region ER may be generated. In an embodiment, the panel driver  120  may add boundary compensation gray levels to the input gray levels for the edge region ER to perform the edge region boosting operation, and may generate the boundary compensated image data BCDAT representing the input gray levels to which boundary compensation gray levels are added for the edge region ER. In one embodiment, for example, as illustrated in  FIG. 2 , in a case where the input image data IDAT represent 100-gray levels  100 G with respect to first and second pixels PX 1  and PX 2  of a first display panel  112  and third and fourth pixels PX 3  and PX 4  of a second display panel  114 , the display panel  20  may perform the edge region boosting operation that adds the boundary compensation gray levels of 25-gray levels to the input gray levels of the second pixel PX 2  in the edge region ER of the first display panel  112  and the third pixel PX 3  in the edge region ER of the second display panel  114 , and thus may generate the boundary compensated image data BCDAT representing the 100-gray levels  100 G with respect to the first pixel PX 1  of the first display panel  112  and the fourth pixel PX 4  of the second display panel  114  and 125-gray levels  125 G with respect to the second pixel PX 2  of the first display panel  112  and the third pixel PX 3  of the second display panel  114 .  FIG. 2  illustrates an embodiment where the edge region ER has a width ERW corresponding to a width or a length of one pixel, but the width ERW of the edge region ER of embodiments of the tiled display device  100  is not limited to the width or the length of one pixel. In one alternative embodiment, for example, the width ERW of the edge region ER may correspond to, but not limited to, a width or a length of two through ten pixels.  FIG. 2  illustrates an embodiment where the boundary line BL has a width BLW corresponding to a width or a length of one pixel, but the width BLW of the boundary line BL of embodiments of the tiled display device  100  is not limited to the width or the length of one pixel. In one alternative embodiment, for example, the width BLW of the boundary line BL may be narrower than the width or the length of one pixel, or may be wider than the width or the length of one pixel. 
     In an image displayed based on the boundary compensated image data BCDAT generated by the edge region boosting operation (or the SSB operation), the boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be effectively prevented or reduced from being perceived. As illustrated in  FIG. 3 , the boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be perceived in an image  220  displayed based on the input image data IDAT on which the edge region boosting operation (or the SSB operation) is not performed. In an embodiment, the boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be effectively prevented or reduced from being perceived in an image  240  displayed based on the boundary compensated image data BCDAT on which the edge region boosting operation (or the SSB operation) is performed. 
     In such an embodiment, since the edge region boosting operation increases the input gray levels for the edge region ER, in a case where the input image data IDAT for the edge region ER represent a maximum gray level (e.g., a 255-gray level) or the input gray levels close to the maximum gray level, the edge region boosting operation may not be effectively performed, and the boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be perceived. As illustrated in  FIG. 4 , in a case where a portion  320  of an image  300  including the boundary line BL and the edge region ER is a high gray image (having a gray level greater than a reference gray level), or in a case where the input image data IDAT corresponding to the portion  320  of the image  300  represent the input gray levels close to the maximum gray level, the edge region boosting operation may not be effectively performed. 
     Accordingly, in an embodiment of the invention, the panel driver  120  of the tiled display device  100  may multiply the input gray levels of the input image data IDAT for the plurality of display panels  112 ,  114 ,  116  and  118  by an adaptive gain AGAIN, and may add the boundary compensation gray levels to the input gray levels multiplied by the adaptive gain AGAIN for the edge region ER. Thus, in such an embodiment, the panel driver  120  may generate the boundary compensated image data BCDAT representing the input gray levels multiplied by the adaptive gain AGAIN with respect to the display region other than the edge region ER of the plurality of display panels  112 ,  114 ,  116  and  118 , and representing sums of the input gray levels multiplied by the adaptive gain AGAIN and the boundary compensation gray levels with respect to the edge region ER of the plurality of display panels  112 ,  114 ,  116  and  118 . In an embodiment, the adaptive gain AGAIN may have a value greater than 0 and less than or equal to 1. In one embodiment, for example, when the adaptive gain AGAIN is 1, the input image data IDAT×AGAIN to which the adaptive gain AGAIN is applied may be substantially the same as the input image data IDAT to which the adaptive gain AGAIN is not applied. In such an embodiment, as the adaptive gain AGAIN decreases from 1, the input image data IDAT×AGAIN to which the adaptive gain AGAIN is applied may be decreased, and luminances of the plurality of display panels  112 ,  114 ,  116  and  118  may be decreased. However, in a case where the adaptive gain AGAIN is rapidly changed (e.g., decreased), a rapid luminance change (e.g., decrease) of an image of the plurality of display panels  112 ,  114 ,  116  and  118  may be perceived. 
     In an embodiment of the tiled display device  100  according to the invention, in a case where a sum of each input gray level for the edge region ER and the boundary compensation gray level exceeds the maximum gray level (e.g., the 255-gray level), the adaptive gain AGAIN may be gradually decreased over a plurality of frame periods to prevent such a rapid luminance change. Accordingly, the luminance of the image of the plurality of display panels  112 ,  114 ,  116  and  118  may be gradually decreased during a time period corresponding to the plurality of frame periods, and such a gradual luminance decrease may not be perceived by a user or a viewer. Such a gradual changing (or decreasing) of the adaptive gain AGAIN over the plurality of frame periods may be referred to as an adaptive gradual gain (“AGG”) control operation. In an embodiment, the panel driver  120  (or the controller  150 ) of the tiled display device  100  may include an adaptive gain control block  160  and an edge region boosting block  170  to perform the AGG control operation and the SSB operation. 
     In an embodiment, the adaptive gain control block  160  may multiply the input gray levels of the input image data IDAT for the plurality of display panels  112 ,  114 ,  116  and  118  by the adaptive gain AGAIN. In such an embodiment, in a case where the sum of each input gray level for the edge region ER and the boundary compensation gray level exceeds the maximum gray level, the adaptive gain control block  160  may gradually decrease the adaptive gain AGAIN over the plurality of frame periods. In an embodiment, the controller  150  may further include a compensation gray lookup table  180  that stores the boundary compensation gray levels corresponding to respective (input) gray levels. In an embodiment, the adaptive gain control block  160  may obtain the boundary compensation gray level corresponding to the input gray level from the compensation gray lookup table  180 , may calculate a sum of the input gray level and the boundary compensation gray level, and may selectively decrease the adaptive gain AGAIN based on whether the sum of the input gray level and the boundary compensation gray level exceeds the maximum gray level. 
     In an embodiment, the adaptive gain control block  160  may gradually decrease the adaptive gain AGAIN in a case where a sum of the input gray level for any one pixel in the edge region ER and the boundary compensation gray level exceeds the maximum gray level. In an alternative embodiment, the adaptive gain control block  160  may selectively gradually decrease the adaptive gain AGAIN based on the number (or a ratio) of pixels in the edge region ER for which the sum of the input gray level and the boundary compensation gray level exceeds the maximum gray level. In another alternative embodiment, the adaptive gain control block  160  may selectively gradually decrease the adaptive gain AGAIN based on the number of the pixels in the edge region ER for which the sum exceeds the maximum gray level and a difference between the sum and the maximum gray level. 
     In an embodiment, in a case where the sum of each of the input gray levels for all the pixels in the edge region ER and the boundary compensation gray level is less than or equal to the maximum gray level, the adaptive gain control block  160  may determine the adaptive gain AGAIN as 1. In such an embodiment, in a case where the sum of the input gray level for any one pixel in the edge region ER and the boundary compensation gray level exceeds the maximum gray level, the adaptive gain control block  160  may gradually decrease the adaptive gain AGAIN over the plurality of frame periods. In one embodiment, for example, the adaptive gain control block  160  may determine a target gain in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level, and may gradually decrease the adaptive gain AGAIN to the target gain over the plurality of frame periods. In an embodiment, the adaptive gain control block  160  may multiply the input gray levels of the input image data IDAT for the plurality of display panels  112 ,  114 ,  116  and  118  by the adaptive gain AGAIN. 
     In an alternative embodiment, the adaptive gain control block  160  may count the number of pixels in the edge region ER for which the sum of the input gray level and the boundary compensation gray level exceeds the maximum gray level, and may determine the adaptive gain AGAIN as 1 in a case where the counted number is less than a reference number. In such an embodiment, in a case where the counted number is greater than or equal to the reference number, the adaptive gain control block  160  may determine the target gain in a way such that the sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level, and may gradually decrease the adaptive gain AGAIN to the target gain over the plurality of frame periods. In such an embodiment, the adaptive gain control block  160  may multiply the input gray levels of the input image data IDAT for the plurality of display panels  112 ,  114 ,  116  and  118  by the adaptive gain AGAIN. 
     In another alternative embodiment, the adaptive gain control block  160  may count the number of pixels in the edge region ER for which the sum of the input gray level and the boundary compensation gray level exceeds the maximum gray level, may calculate a ratio of the counted number to a total pixel number in the edge region ER, and may determine the adaptive gain AGAIN as 1 in a case where the calculated ratio is less than a reference ratio. In such an embodiment, in a case where the calculated ratio is greater than or equal to the reference ratio, the adaptive gain control block  160  may determine the target gain in a way such that the sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level, and may gradually decrease the adaptive gain AGAIN to the target gain over the plurality of frame periods. In such an embodiment, the adaptive gain control block  160  may multiply the input gray levels of the input image data IDAT for the plurality of display panels  112 ,  114 ,  116  and  118  by the adaptive gain AGAIN. 
     In still another alternative embodiment, the adaptive gain control block  160  may determine sums of the input gray levels for the edge region ER and the boundary compensation gray levels exceeding the maximum gray level, may calculate differences between the sums exceeding the maximum gray level and the maximum gray level, and may determines the adaptive gain AGAIN as 1 in a case where a sum of the differences is less than a reference value. In such an embodiment, in a case where the sum of the differences is greater than or equal to the reference value, the adaptive gain control block  160  may determine the target gain in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level, and may gradually decrease the adaptive gain AGAIN to the target gain over the plurality of frame periods. In such an embodiment, the adaptive gain control block  160  may multiply the input gray levels of the input image data IDAT for the plurality of display panels  112 ,  114 ,  116  and  118  by the adaptive gain AGAIN. 
     In an embodiment, the adaptive gain AGAIN may have a single value or a same value with respect to the entire region of the plurality of display panels  112 ,  114 ,  116  and  118 . Thus, the adaptive gain control block  160  may gradually decrease the adaptive gain AGAIN over the plurality of frame periods by a same amount with respect to the entire region of the plurality of display panels  112 ,  114 ,  116  and  118 .  FIG. 5  illustrates an embodiment where the adaptive gain AGAIN is gradually decreased over the plurality of frame periods. In  FIG. 5  (and  FIG. 6 ), EP 1  may represent a position of the edge region ER of the first display panel  112  at a side distant from the second display panel  114 , CP 1  may represent a position of a center region of the first display panel  112 , EP 2 /BP may represent a position of the edge region ER of the first display panel  112  at a side close to the second display panel  114 , a position of the boundary line BL, or a position of the edge region ER of the second display panel  114  at a side close to the first display panel  112 , CP 2  may represent a position of a center region of the second display panel  114 , and EP 3  may represent a position of the edge region ER of the second display panel  114  at a side distant from the first display panel  112 . In one embodiment, for example, as illustrated in  FIG. 5 , the adaptive gain AGAIN may be gradually decreased over N frame periods FP 1 , FPN/2, . . . , and FPN by a same amount with respect to the entire region of the plurality of display panels  112 ,  114 ,  116  and  118 , where N is an integer greater than 1. In an embodiment, where a driving frequency of the plurality of display panels  112 ,  114 ,  116  and  118  is about 120 hertz (Hz), and the target gain is about 0.8, to gradually decrease the adaptive gain AGAIN for about 10 seconds, the adaptive gain control block  160  may gradually decrease the adaptive gain AGAIN from about 1 to about 0.8 over 1,200 frame periods FP 1 , FPN/2, . . . , and FPN. In such an embodiment, the adaptive gain AGAIN may have a same value of about 0.9 with respect to the entire region of the plurality of display panels  112 ,  114 ,  116  and  118  in a 600-th frame period FPN/2, and may have a same value of about 0.8 with respect to the entire region of the plurality of display panels  112 ,  114 ,  116  and  118  in a 1,200-th frame period FPN. 
     In an alternative embodiment, the adaptive gain AGAIN after the plurality of frame periods may be gradually decreased along a direction or as being away from a center region of each display panel  112 ,  114 ,  116  and  118  to the edge region ER.  FIG. 6  illustrates an embodiment of the adaptive gain AGAIN for one pixel row of the first and second display panels  112  and  114 . In one embodiment, for example, as illustrated in  FIG. 6 , the adaptive gain AGAIN may be decreased by a first amount DA 1  over N frame periods FP 1 , FPN/2, . . . , and FPN at a position CP 1  and CP 2  of the center region of each display panel  112  and  114 , and may be decreased by a second amount DA 2  greater than the first amount DA 1  over the N frame periods FP 1 , FPN/2, . . . , and FPN at a position EP 1 , EP 2 /BP and EP 3  of the edge region ER of each display panel  112  and  114 . In an embodiment, where a driving frequency of the plurality of display panels  112 ,  114 ,  116  and  118  is about 120 Hz, and the target gain is about 0.8, to gradually decrease the adaptive gain AGAIN for about 10 seconds, the adaptive gain control block  160  may gradually decrease the adaptive gain AGAIN by the second amount DA 2  of about 0.2 over 1,200 frame periods FP 1 , FPN/2, . . . , and FPN at the position EP 1 , EP 2 /BP and EP 3  of the edge region ER of each display panel  112  and  114 , and may gradually decrease the adaptive gain AGAIN by the first amount DA 1  less than the second amount DA 2  of about 0.2 over the 1,200 frame periods FP′, FPN/2, . . . , and FPN at the position CP 1  and CP 2  of the center region of each display panel  112  and  114 . 
     The edge region boosting block  170  may receive the input image data IDAT×AGAIN multiplied by the adaptive gain AGAIN from the adaptive gain control block  160 , may generate the boundary compensated image data BCDAT by performing the edge region boosting operation that adds the boundary compensation gray levels to the input gray levels of the input image data IDAT×AGAIN multiplied by the adaptive gain AGAIN for the edge region ER, and may provide the boundary compensated image data BCDAT to the data driver  130 . The data driver  130  may drive the plurality of display panels  112 ,  114 ,  116  and  118  based on the boundary compensated image data BCDAT. 
     In an embodiment, as shown in  FIG. 1 , the controller  150  may further include a compensation gray lookup table  180  that stores the boundary compensation gray levels corresponding to respective (input) gray levels. According to an embodiment, values of the boundary compensation gray levels may be determined based on, but not limited to, a width of the boundary line BL, a pixel pitch of each display panel  112 ,  114 ,  116  and  118 , etc. In an embodiment, the edge region boosting block  170  may determine the boundary compensation gray levels corresponding to the input gray levels multiplied by the adaptive gain AGAIN by using the compensation gray lookup table  180 , and may generate the boundary compensated image data BCDAT by adding the boundary compensation gray levels to the input gray levels multiplied by the adaptive gain AGAIN for the edge region ER. 
     In an embodiment, as described above, the tiled display device  100  may multiply the input gray levels of the input image data IDAT for the plurality of display panels  112 ,  114 ,  116  and  118  coupled to each other by the adaptive gain AGAIN, may generate the boundary compensated image data BCDAT by adding the boundary compensation gray levels to the input gray levels (multiplied by the adaptive gain AGAIN) for the edge region ER adjacent to the boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118 , and may drive the plurality of display panels  112 ,  114 ,  116  and  118  based on the boundary compensated image data BCDAT. Accordingly, in such an embodiment of the tiled display device  100 , the boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be effectively prevented or reduced from being perceived. Further, in such an embodiment of the tiled display device  100 , the adaptive gain AGAIN may be gradually decreased over the plurality of frame periods in a case where the sum of the input gray level for the edge region ER and the boundary compensation gray level exceeds the maximum gray level. Accordingly, even when a high gray image is displayed in the edge region ER, the edge region boosting operation may be performed while the luminance reduction caused by the adaptive gain AGAIN is not perceived. 
       FIG. 7  is a flowchart illustrating a method of operating a tiled display device according to an embodiment. 
     Referring to  FIGS. 1 and 7 , in an embodiment of a method of operating a tiled display device  100 , a panel driver  120  may receive input image data IDAT (S 410 ), and an adaptive gain control block  160  of the panel driver  120  may control an adaptive gain AGAIN based on whether a sum of an input gray level of the input image data IDAT and a boundary compensation gray level exceeds a maximum gray level (S 420 , S 430 , S 440  and S 450 ). 
     In a case where a sum of each of input gray levels for all pixels in an edge region ER and the boundary compensation gray level is less than or equal to the maximum gray level (S 420 : NO), the adaptive gain control block  160  may determine the adaptive gain AGAIN as 1 (S 430 ). 
     In a case where the sum of the input gray level for any one pixel in the edge region ER and the boundary compensation gray level is greater than the maximum gray level (S 420 : YES), the adaptive gain control block  160  may gradually decrease the adaptive gain AGAIN over a plurality of frame periods (S 440  and S 450 ). In one embodiment, for example, the adaptive gain control block  160  may determine a target gain in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level (S 440 ), and may gradually decrease the adaptive gain AGAIN to the target gain over the plurality of frame periods (S 450 ). 
     The adaptive gain control block  160  may multiply the input gray levels of the input image data IDAT for a plurality of display panels  112 ,  114 ,  116  and  118  by the adaptive gain AGAIN, and an edge region boosting block  170  of the panel driver  120  may generate boundary compensated image data BCDAT by performing an edge region boosting operation that adds the boundary compensation gray levels to the input gray levels of the input image data IDAT×AGAIN multiplied by the adaptive gain AGAIN for the edge region ER (S 460 ). 
     The edge region boosting block  170  may provide the boundary compensated image data BCDAT to a data driver  130 , and the data driver  130  may drive the plurality of display panels  112 ,  114 ,  116  and  118  based on the boundary compensated image data BCDAT (S 470 ). Accordingly, in such an embodiment of the tiled display device  100 , a boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be effectively prevented or reduced from being perceived. In such an embodiment, even when a high gray image is displayed in the edge region ER, the edge region boosting operation may be effectively performed while a luminance reduction caused by the adaptive gain AGAIN is not perceived. 
       FIG. 8  is a flowchart illustrating a method of operating a tiled display device according to an alternative embodiment. 
     Referring to  FIGS. 1 and 8 , in an embodiment of a method of operating a tiled display device  100 , a panel driver  120  may receive input image data IDAT (S 510 ), and an adaptive gain control block  160  of the panel driver  120  may control an adaptive gain AGAIN based on the number of pixels in an edge region ER for which a sum of an input gray level of the input image data IDAT and a boundary compensation gray level exceeds a maximum gray level (S 520 , S 530 , S 540 , S 550  and S 560 ). 
     The adaptive gain control block  160  may count the number of pixels in the edge region ER for which the sum of the input gray level and the boundary compensation gray level exceeds the maximum gray level (S 520 ). In a case where the counted number is less than a reference number (S 530 : YES), the adaptive gain control block  160  may determine the adaptive gain AGAIN as 1 (S 540 ). 
     In a case where the counted number is greater than or equal to the reference number (S 530 : NO), the adaptive gain control block  160  may gradually decrease the adaptive gain AGAIN over a plurality of frame periods (S 550  and S 560 ). In one embodiment, for example, the adaptive gain control block  160  may determine a target gain in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level (S 550 ), and may gradually decrease the adaptive gain AGAIN to the target gain over the plurality of frame periods (S 560 ). 
     The adaptive gain control block  160  may multiply the input gray levels of the input image data IDAT for a plurality of display panels  112 ,  114 ,  116  and  118  by the adaptive gain AGAIN, and an edge region boosting block  170  of the panel driver  120  may generate boundary compensated image data BCDAT by performing an edge region boosting operation that adds the boundary compensation gray levels to the input gray levels of the input image data IDAT×AGAIN multiplied by the adaptive gain AGAIN for the edge region ER (S 570 ). 
     The edge region boosting block  170  may provide the boundary compensated image data BCDAT to a data driver  130 , and the data driver  130  may drive the plurality of display panels  112 ,  114 ,  116  and  118  based on the boundary compensated image data BCDAT (S 580 ). Accordingly, in such an embodiment of the tiled display device  100 , a boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be effectively prevented or reduced from being perceived. In such an embodiment, even when a high gray image is displayed in the edge region ER, the edge region boosting operation may be effectively performed while a luminance reduction caused by the adaptive gain AGAIN is not perceived. 
       FIG. 9  is a flowchart illustrating a method of operating a tiled display device according to another alternative embodiment. 
     Referring to  FIGS. 1 and 9 , in an embodiment of a method of operating a tiled display device  100 , a panel driver  120  may receive input image data IDAT (S 1510 ), and an adaptive gain control block  160  of the panel driver  120  may control an adaptive gain AGAIN based on a ratio of the number of pixels in an edge region ER for which a sum of an input gray level and a boundary compensation gray level exceeds a maximum gray level to a total pixel number in the edge region ER (S 1520 , S 1525 , S 1530 , S 1540 , S 1550  and S 1560 ). 
     The adaptive gain control block  160  may count the number of pixels in the edge region ER for which the sum of the input gray level and the boundary compensation gray level exceeds the maximum gray level (S 1520 ), and may calculate a ratio of the counted number to the total pixel number in the edge region ER (S 1525 ). In a case where the calculated ratio is less than a reference ratio (S 1530 : YES), the adaptive gain control block  160  may determine the adaptive gain AGAIN as 1 (S 1540 ). 
     In a case where the calculated ratio is greater than or equal to the reference ratio (S 1530 : NO), the adaptive gain control block  160  may determine a target gain in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level (S 1550 ), and may gradually decrease the adaptive gain AGAIN to the target gain over a plurality of frame periods (S 1560 ). 
     The adaptive gain control block  160  may multiply the input gray levels of the input image data IDAT for a plurality of display panels  112 ,  114 ,  116  and  118  by the adaptive gain AGAIN, and an edge region boosting block  170  of the panel driver  120  may generate boundary compensated image data BCDAT by performing an edge region boosting operation that adds the boundary compensation gray levels to the input gray levels of the input image data IDAT×AGAIN multiplied by the adaptive gain AGAIN for the edge region ER (S 1570 ). 
     The edge region boosting block  170  may provide the boundary compensated image data BCDAT to a data driver  130 , and the data driver  130  may drive the plurality of display panels  112 ,  114 ,  116  and  118  based on the boundary compensated image data BCDAT (S 1580 ). Accordingly, in such an embodiment of the tiled display device  100 , a boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be effectively prevented or reduced from being perceived. In such an embodiment, even when a high gray image is displayed in the edge region ER, the edge region boosting operation may be effectively performed while a luminance reduction caused by the adaptive gain AGAIN is not perceived. 
       FIG. 10  is a flowchart illustrating a method of operating a tiled display device according to another alternative embodiment. 
     Referring to  FIGS. 1 and 10 , in an embodiment of a method of operating a tiled display device  100 , a panel driver  120  may receive input image data IDAT (S 610 ), and an adaptive gain control block  160  of the panel driver  120  may control an adaptive gain AGAIN based on the number of sums of input gray levels of the input image data IDAT for and edge region ER and boundary compensation gray levels exceeding a maximum gray level, and differences between the sums and the maximum gray level (S 620 , S 630 , S 640 , S 650 , S 660  and S 670 ). 
     The adaptive gain control block  160  may determine the sums of the input gray levels for the edge region ER and the boundary compensation gray levels exceeding the maximum gray level (S 620 ), and may calculate the differences between the sums exceeding the maximum gray level and the maximum gray level (S 630 ). In a case where a sum of the differences is less than a reference value (S 640 : YES), the adaptive gain control block  160  may determine the adaptive gain AGAIN as 1 (S 650 ). 
     In a case where the sum of the differences is greater than or equal to the reference value (S 640 : NO), the adaptive gain control block  160  may gradually decrease the adaptive gain AGAIN over a plurality of frame periods (S 660  and S 670 ). In one embodiment, for example, the adaptive gain control block  160  may determine a target gain in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level (S 660 ), and may gradually decrease the adaptive gain AGAIN to the target gain over the plurality of frame periods (S 670 ). 
     The adaptive gain control block  160  may multiply the input gray levels of the input image data IDAT for a plurality of display panels  112 ,  114 ,  116  and  118  by the adaptive gain AGAIN, and an edge region boosting block  170  of the panel driver  120  may generate boundary compensated image data BCDAT by performing an edge region boosting operation that adds the boundary compensation gray levels to the input gray levels of the input image data IDAT×AGAIN multiplied by the adaptive gain AGAIN for the edge region ER (S 680 ). 
     The edge region boosting block  170  may provide the boundary compensated image data BCDAT to a data driver  130 , and the data driver  130  may drive the plurality of display panels  112 ,  114 ,  116  and  118  based on the boundary compensated image data BCDAT (S 690 ). Accordingly, in such an embodiment of the tiled display device  100 , a boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be effectively prevented or reduced from being perceived. In such an embodiment, even when a high gray image is displayed in the edge region ER, the edge region boosting operation may be effectively performed while a luminance reduction caused by the adaptive gain AGAIN is not perceived. 
       FIG. 11  is a block diagram illustrating a tiled display device according to an alternative embodiment, and  FIG. 12  is a block diagram illustrating an embodiment of a test device that generates mura compensation data for a tiled display device of  FIG. 11 . 
     Referring to  FIG. 11 , an embodiment of a tiled display device  700  according to the invention may include a plurality of display panels  112 ,  114 ,  116  and  118  and a panel driver  720 . The panel driver  720  may include a data driver  130 , a gate driver  140 , a compensation data memory  795  and a controller  750 . The controller  750  may include an adaptive gain control block  160 , an edge region boosting block  170 , a compensation gray lookup table  180  and a mura compensating block  790 . The tiled display device  700  of  FIG. 11  may have a similar configuration and a similar operation to a tiled display device  100  of  FIG. 1 , except that the panel driver  720  may further include the compensation data memory  795  and the mura compensating block  790 . The same or like elements shown in  FIG. 11  have been labeled with the same reference characters as used above to describe the embodiment of the tiled display device  100  shown in  FIG. 1  and any repetitive detailed description thereof will hereinafter be omitted or simplified. 
     The compensation data memory  795  may store mura compensation data MCD. In an embodiment, the mura compensation data MCD of the compensation data memory  795  may be generated based on an image displayed based on image data on which an edge region boosting operation is performed when the tiled display device  700  is manufactured. In one embodiment, for example, as illustrated in  FIG. 12 , when the tiled display device  700  is manufactured, the panel driver  720  may receive test data TDAT from a test device  800 , may perform the edge region boosting operation that adds boundary compensation gray levels to the test data TDAT for the edge region ER, and may drive the plurality of display panels  112 ,  114 ,  116  and  118  based on the test data TDAT to which the boundary compensation gray levels are added. The test device  800  may capture an image displayed by the plurality of display panels  112 ,  114 ,  116  and  118  based on the test data TDAT to which the boundary compensation gray levels are added by using a camera  850 , may generate the mura compensation data MCD based on the captured image, and may write or store the mura compensation data MCD to the compensation data memory  795  of the tiled display device  700 . 
     The mura compensating block  790  may correct boundary compensated image data BCDAT based on the mura compensation data MCD. In an embodiment, the mura compensation data MCD may represent a plurality of mura compensation values respectively for all pixels of the plurality of display panels  112 ,  114 ,  116  and  118 , and the mura compensating block  790  may perform a pixel-wise mura correction operation by adding the plurality of mura compensation values to the boundary compensated image data BCDAT. The mura compensating block  790  may provide the boundary compensated image data BCDAT′ corrected based on the mura compensation data MCD to the data driver  130 , and the data driver  130  may drive the plurality of display panels  112 ,  114 ,  116  and  118  based on the boundary compensated image data BCDAT′ corrected based on the mura compensation data MCD. Since the mura compensation data MCD are generated based on the test data TDAT on which the edge region boosting operation is performed, in an image displayed based on the boundary compensated image data BCDAT′ corrected based on the mura compensation data MCD, a boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be further effectively prevented or reduced from being perceived. 
       FIG. 13  is a flowchart illustrating a method of operating a tiled display device according to an embodiment. 
     Referring to  FIGS. 11 and 13 , in an embodiment of a method of operating a tiled display device  700 , a compensation data memory  795  of the tiled display device  700  may store mura compensation data MCD (S 910 ). In an embodiment, when the tiled display device  700  is manufactured, a panel driver  720  may receive test data from a test device, may add boundary compensation gray levels to the test data for an edge region ER, and may drive a plurality of display panels  112 ,  114 ,  116  and  118  based on the test data to which the boundary compensation gray levels are added. The mura compensation data MCD may be generated by capturing an image displayed by the plurality of display panels  112 ,  114 ,  116  and  118  based on the test data to which the boundary compensation gray levels are added. 
     The panel driver  720  may receive input image data IDAT (S 920 ), and an adaptive gain control block  160  of the panel driver  720  may control an adaptive gain AGAIN according to whether a sum of an input gray level of the input image data IDAT and a boundary compensation gray level exceeds a maximum gray level (S 930 , S 940 , S 950  and S 960 ). 
     In a case where a sum of the input gray level for the edge region ER and the boundary compensation gray level is less than or equal to the maximum gray level (S 930 : NO), the adaptive gain control block  160  may determine the adaptive gain AGAIN as 1 (S 940 ). 
     In a case where the sum of the input gray level for the edge region ER and the boundary compensation gray level is greater than the maximum gray level (S 930 : YES), the adaptive gain control block  160  may determine a target gain in a way such that sums of the input gray levels multiplied by the target gain and the boundary compensation gray levels are less than or equal to the maximum gray level (S 950 ), and may gradually decrease the adaptive gain AGAIN to the target gain over a plurality of frame periods (S 960 ). 
     The adaptive gain control block  160  may multiply the input gray levels of the input image data IDAT for the plurality of display panels  112 ,  114 ,  116  and  118  by the adaptive gain AGAIN, and an edge region boosting block  170  of the panel driver  720  may generate boundary compensated image data BCDAT by performing an edge region boosting operation that adds the boundary compensation gray levels to the input gray levels of the input image data IDAT×AGAIN multiplied by the adaptive gain AGAIN for the edge region ER (S 970 ). 
     A mura compensating block  790  of the panel driver  720  may correct the boundary compensated image data BCDAT based on the mura compensation data MCD stored in the compensation data memory  795  (S 980 ). The mura compensating block  790  may provide the boundary compensated image data BCDAT′ corrected based on the mura compensation data MCD to a data driver  130 , and the data driver  130  may drive the plurality of display panels  112 ,  114 ,  116  and  118  based on the boundary compensated image data BCDAT′ corrected based on the mura compensation data MCD (S 990 ). Accordingly, in such an embodiment of the tiled display device  700 , a boundary line BL between the plurality of display panels  112 ,  114 ,  116  and  118  may be effectively prevented or reduced from being perceived. In such an embodiment, even when a high gray image is displayed in the edge region ER, the edge region boosting operation may be effectively performed while a luminance reduction caused by the adaptive gain AGAIN is not perceived. 
       FIG. 14  is a block diagram illustrating an electronic device including a tiled display device according to an embodiment. 
     Referring to  FIG. 14 , an embodiment of an electronic device  1100  may include a processor  1110 , a memory device  1120 , a storage device  1130 , an input/output (“I/O”) device  1140 , a power supply  1150 , and a tiled display device  1160 . The electronic device  1100  may further include a plurality of ports for communicating with a video card, a sound card, a memory card, a universal serial bus (“USB”) device, other electric devices, etc. 
     The processor  1110  may perform various computing functions or tasks. The processor  1110  may be an AP, a micro-processor, a central processing unit (“CPU”), etc. 
     The processor  1110  may be coupled to other components via an address bus, a control bus, a data bus, etc. Further, in an embodiment, the processor  1110  may be further coupled to an extended bus such as a peripheral component interconnection (“PCI”) bus. 
     The memory device  1120  may store data for operations of the electronic device  1100 . In one embodiment, for example, the memory device  1120  may include at least one non-volatile memory device such as an erasable programmable read-only memory (“EPROM”) device, an electrically erasable programmable read-only memory (“EEPROM”) device, a flash memory device, a phase change random access memory (“PRAM”) device, a resistance random access memory (“RRAM”) device, a nano floating gate memory (“NFGM”) device, a polymer random access memory (“PoRAM”) device, a magnetic random access memory (“MRAM”) device, a ferroelectric random access memory (“FRAM”) device, etc., and/or at least one volatile memory device such as a dynamic random access memory (“DRAM”) device, a static random access memory (“SRAM”) device, a mobile DRAM device, etc. 
     The storage device  1130  may be a solid state drive (“SSD”) device, a hard disk drive (“HDD”) device, a CD-ROM device, etc. The I/O device  1140  may be an input device such as a keyboard, a keypad, a mouse, a touch screen, etc., and an output device such as a printer, a speaker, etc. The power supply  1150  may supply power for operations of the electronic device  1100 . The tiled display device  1160  may be coupled to other components through the buses or other communication links. 
     In such an embodiment, the tiled display device  1160  may multiply input gray levels of input image data for a plurality of display panels coupled to each other by an adaptive gain, may generate boundary compensated image data by adding boundary compensation gray levels to the input gray levels (multiplied by the adaptive gain) for an edge region adjacent to a boundary line between the plurality of display panels, and may drive the plurality of display panels based on the boundary compensated image data. In such an embodiment, the adaptive gain may be gradually decreased over a plurality of frame periods in a case where a sum of each of the input gray levels for the edge region and a corresponding one of the boundary compensation gray levels exceeds a maximum gray level. Accordingly, in such an embodiment of the tiled display device  1160 , the boundary line between the plurality of display panels may be effectively prevented or reduced from being perceived. 
     Embodiments of the invention described herein may be applied to any tiled display device  1160 , and any electronic device  1100  including the tiled display device  1160 , for example, a smart phone, a wearable electronic device, a tablet computer, a mobile phone, a television (“TV”), a digital TV, a 3D TV, a personal computer (“PC”), a home appliance, a laptop computer, a personal digital assistant (“PDA”), a portable multimedia player (“PMP”), a digital camera, a music player, a portable game console, a navigation device, etc. 
     The invention should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art. 
     While the invention has been particularly shown and described with reference to embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit or scope of the invention as defined by the following claims.