Patent Publication Number: US-10319310-B2

Title: Display device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0151343, under 35 U.S.C. § 119, filed on Oct. 29, 2015 in the Korean Intellectual Property Office (KIPO), the content of which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field of disclosure 
     One or more example embodiments of the inventive concept relate to a display device. More particularly, one or more example embodiments of the inventive concept relate to a display device that may be operated based on normally black and normally white operations. 
     2. Description of the Related Art 
     A display device includes a display panel for displaying an image, and gate and data driving circuits for driving the display panel. The display panel includes gate lines, data lines, and pixels. Each pixel may include a thin film transistor, a liquid crystal capacitor, and a storage capacitor. The data driving circuit applies data driving signals to the data lines, and the gate driving circuit applies gate driving signals to drive the gate lines. 
     In general, the display device performs a gamma correction operation to match a difference between a driving characteristic (e.g., linearity) and a human visual sensation characteristic (e.g., non-linearity) of a user. A gamma corrector that performs the gamma correction operation generates gamma reference voltages based on a gamma driving voltage according to characteristics of the display panel. 
     However, the gamma driving voltage is continuously applied to the data driving circuit at a constant DC voltage. As a result, the gamma reference voltages are generated to cover all grayscale (e.g., gray level) periods regardless of image signals. Accordingly, even when the data driving circuit requires only the gamma reference voltages with a relatively low level in accordance with the image signals, the gamma reference voltages with a relatively high level, which may be unnecessary, are applied to the data driving circuit. 
     The above information disclosed in this Background section is for enhancement of understanding of the background of the inventive concept, and therefore, it may contain information that does not constitute prior art. 
     SUMMARY 
     One or more example embodiments of the inventive concept provide a display device capable of controlling a gamma driving voltage in accordance with a grayscale level (e.g., a gray level) of an image signal and capable of controlling a brightness of light provided to a display panel. 
     According to an example embodiment of the inventive concept, a display device includes: a display panel including first group pixels connected to a first gate line to receive first data voltages, and second group pixels connected to the first gate line to receive second data voltages; a backlight source configured to provide light to the display panel; a signal controller configured to divide horizontal image signals into first group image signals and second group image signals, to extract a first maximum grayscale image signal from the first group image signals, and to extract a second maximum grayscale image signal from the second group image signals; a power supply configured to generate first and second gamma driving voltages from a reference gamma driving voltage based on a grayscale level of the first maximum grayscale image signal and a grayscale level of the second maximum grayscale image signal; a first data driving circuit configured to apply the first data voltages generated based on the first gamma driving voltage and the first group image signals to the first group pixels; and a second data driving circuit configured to apply the second data voltages generated based on the second gamma driving voltage and the second group image signals to the second group pixels. 
     The signal controller may be configured to convert the first group image signals to first converted image signals based on the first maximum grayscale image signal, and to convert the second group image signals to second converted image signals based on the second maximum grayscale image signal. 
     The first data driving circuit may be configured to generate the first data voltages based on the first converted image signals, and the second data driving circuit may be configured to generate the second data voltages based on the second converted image signals. 
     The signal controller may be configured to generate the first gamma driving voltage that is lower than the reference gamma driving voltage in accordance with the grayscale level of the first maximum grayscale image signal, and to generate the second gamma driving voltage that is lower than the reference gamma driving voltage in accordance with the grayscale level of the second maximum grayscale image signal. 
     The backlight source may include first group light emitting diodes and second group light emitting diodes, the first group light emitting diodes being configured to provide a first light to the first group pixels in response to a first light control signal, and the second group light emitting diodes being configured to provide a second light to the second group pixels in response to a second light control signal. 
     The signal controller may be configured to compare the grayscale level of the first maximum grayscale image signal with a reference grayscale level, and to output the first light control signal to control a brightness of the first light according to the comparison. 
     The signal controller may be configured to generate the first light control signal to maintain the brightness of the first light at a maximum brightness and the power supply may be configured to generate the first gamma driving voltage that is lower than the reference gamma driving voltage, when the grayscale level of the first maximum grayscale image signal is greater than or equal to the reference grayscale level. 
     The signal controller may be configured to generate the first light control signal to lower the brightness of the first light from a maximum brightness and the power supply may be configured to generate the reference gamma driving voltage as the first gamma driving voltage, when the grayscale level of the first maximum grayscale image signal is less than or equal to the reference grayscale level. 
     The signal controller may be configured to generate the first light control signal to lower the brightness of the first light from a maximum brightness and the power supply may be configured to generate the first gamma driving voltage that is lower than the reference gamma driving voltage, when the grayscale level of the first maximum grayscale image signal is less than or equal to the reference grayscale level. 
     The signal controller may include: a memory configured to receive the horizontal image signals; a maximum grayscale extractor configured to extract the first maximum grayscale image signal and the second maximum grayscale image signal; an image signal converter configured to convert the first group image signals to first converted image signals based on the first maximum grayscale image signal, and to convert the second group image signals to second converted image signals based on the second maximum grayscale image signal; and a dimmer configured to control the backlight source in response to the first and second maximum grayscale image signals. 
     The image signal converter may include: a look-up table configured to store the first converted image signals and the second converted image signals; and a register configured to extract the first converted image signals corresponding to the grayscale level of the first maximum grayscale image signal from among the converted image signals stored in the look-up table, and to apply the extracted first converted image signals to the first data driving circuit. 
     The backlight source may include a plurality of light emitting diodes, and the light emitting diodes may be configured to provide the light to the first group pixels and the second group pixels in response to a light control signal. 
     The signal controller may be configured to generate a light control signal to lower a brightness of the light from a maximum brightness and the power supply may be configured to generate the first and second gamma driving voltages that are smaller than the reference gamma driving voltage, when the grayscale level of the first maximum grayscale image signal and the grayscale level of the second maximum grayscale image signal are less than or equal to a reference grayscale level. 
     The signal controller may be configured to store at least one horizontal image signal based on a maximum variation amount of a grayscale level that is variable during a horizontal blank period. 
     The signal controller may be configured to calculate a minimum gamma driving voltage that is utilized by each horizontal period based on the maximum variation amount of the grayscale level that is variable during the horizontal blank period, and the power supply may be configured to compare the minimum gamma driving voltage that is utilized by each horizontal period and the first gamma driving voltage, and to apply one of the minimum gamma driving voltage and the first gamma driving voltage to the first data driving circuit according to the comparison. 
     According to an embodiment of the inventive concept, a display device includes: a display panel including first group pixels connected to a first gate line to receive first data voltages, and second group pixels connected to the first gate line to receive second data voltages; a backlight source configured to provide light to the display panel; a signal controller configured to divide horizontal image signals into first group image signals and second group image signals, to extract a first minimum grayscale image signal from the first group image signals, and to extract a second minimum grayscale image signal from the second group image signals; a power supply configured to generate first and second gamma driving voltages from a reference gamma driving voltage based on a grayscale level of the first minimum grayscale image signal and a grayscale level of the second minimum grayscale image signal; a first data driving circuit configured to apply the first data voltages generated based on the first gamma driving voltage and the first group image signals to the first group pixels; and a second data driving circuit configured to apply the second data voltages generated based on the second gamma driving voltage and the second group image signals to the second group pixels. 
     The signal controller may be configured to convert the first group image signals to first converted image signals based on the first minimum grayscale image signal, and the first data driving circuit may be configured to generate the first data voltages based on the first converted image signals. 
     The backlight source may include first group light emitting diodes and second group light emitting diodes, the first group light emitting diodes may be configured to provide a first light to the first group pixels in response to a first light control signal, and the second group light emitting diodes may be configured to provide a second light to the second group pixels in response to a second light control signal. 
     The signal controller may be configured to generate the first light control signal to lower a brightness of the first light from a maximum brightness and the power supply may be configured to generate the reference gamma driving voltage as the first gamma driving voltage, when the grayscale level of the first minimum grayscale image signal is less than or equal to a reference grayscale level. 
     The signal controller may be configured to generate the first light control signal to maintain a brightness of the first light at a maximum brightness and the power supply may be configured to generate the first gamma driving voltage to lower the reference gamma driving voltage, when the grayscale level of the first minimum grayscale image signal is greater than or equal to a reference grayscale level. 
     According to one or more example embodiments, power consumption of the display device may be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects and features of the present disclosure will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a block diagram showing a display device according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is a timing diagram showing an operation of a gate driving circuit and a data driving circuit shown in  FIG. 1 ; 
         FIG. 3  is a block diagram showing a signal controller and a power supply shown in  FIG. 1  according to an exemplary embodiment of the present disclosure; 
         FIG. 4  is a block diagram showing a converted image signal and an emission of light, which are provided to a display panel according to an exemplary embodiment of the present disclosure; 
         FIG. 5  is a block diagram showing an image signal converter shown in  FIG. 3 ; 
         FIG. 6  is a block diagram showing the power supply shown in  FIG. 3 ; 
         FIG. 7  is a table showing an operation of a signal controller and a backlight unit according to an exemplary embodiment of the present disclosure; 
         FIG. 8  is a graph showing a first maximum grayscale image signal shown in  FIG. 7 ; 
         FIG. 9  is a graph showing a third maximum grayscale image signal shown in  FIG. 7 ; 
         FIG. 10  is a graph showing a fourth maximum grayscale image signal shown in  FIG. 7 ; 
         FIG. 11  is a flowchart showing an operation of the signal controller and the power supply shown in  FIG. 3  to output a final gamma driving voltage; 
         FIG. 12  is block diagram showing a converted image signal and an emission of light, which are provided to a display panel according to another exemplary embodiment of the present disclosure; 
         FIG. 13  is a table showing an operation of a signal controller and a backlight unit according to another exemplary embodiment of the present disclosure; 
         FIG. 14  is a block diagram showing a signal controller and a power supply according to another exemplary embodiment of the present disclosure; and 
         FIG. 15  is a table showing an operation of a signal controller and a backlight unit according to another exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, example embodiments will be described in more detail with reference to the accompanying drawings. The present inventive concept, however, may be embodied in various different forms, and should not be construed as being limited to only the illustrated embodiments herein. Rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the aspects and features of the inventive concept to those skilled in the art. Accordingly, processes, elements, and techniques that are not necessary to those having ordinary skill in the art for a complete understanding of the aspects and features of the inventive concept may not be described. Unless otherwise noted, like reference numerals denote like elements throughout the attached drawings and the written description, and thus, descriptions thereof may not be repeated. 
     In the drawings, the relative sizes of elements, layers, and regions may be exaggerated and/or simplified for clarity. Spatially relative terms, such as “beneath,” “below,” “lower,” “under,” “above,” “upper,” and the like, may be used herein for ease of explanation to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or in operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” or “under” other elements or features would then be oriented “above” the other elements or features. Thus, the example terms “below” and “under” can encompass both an orientation of above and below. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly. 
     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 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 described below could be termed a second element, component, region, layer or section, without departing from the spirit and scope of the inventive concept. 
     It will be understood that when an element or layer is referred to as being “on,” “connected to,” or “coupled to” another element or layer, it can be directly on, connected to, or coupled to the other element or layer, or one or more intervening elements or layers may be present. In addition, it will also be understood that when an element or layer is referred to as being “between” two elements or layers, it can be the only element or layer between the two elements or layers, or one or more intervening elements or layers may also be present. 
     The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the inventive concept. As used herein, the singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and “including,” when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     As used herein, the term “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent variations in measured or calculated values that would be recognized by those of ordinary skill in the art. Further, the use of “may” when describing embodiments of the inventive concept refers to “one or more embodiments of the inventive concept.” As used herein, the terms “use,” “using,” and “used” may be considered synonymous with the terms “utilize,” “utilizing,” and “utilized,” respectively. Also, the term “exemplary” is intended to refer to an example or illustration. 
     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 the present inventive concept 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/or the present specification, and should not be interpreted in an idealized or overly formal sense, unless expressly so defined herein. 
     According to one or more example embodiments, the display devices shown in  FIGS. 1 to 13  may be operated in a normally black mode NB. The term “normally black mode NB” refers to a case where a grayscale level of an image signal corresponding to a data voltage becomes high as a level of the data voltage applied to a pixel increases. 
       FIG. 1  is a block diagram showing a display device DD according to an exemplary embodiment of the present disclosure. 
     Referring to  FIG. 1 , the display device DD includes a driving circuit board  100 , a gate driving circuit  200 , a data driving circuit  300 , a display panel  400 , and a backlight unit (e.g., a backlight source)  500 . 
     The driving circuit board  100  includes a signal controller  110  to control an overall operation of the display device DD. The signal controller  110  receives a plurality of control signals CS and a plurality of image signals RGB from the outside of the display device DD. 
     The signal controller  110  outputs a plurality of driving signals in response to the control signal CS. The signal controller  110  generates a data control signal D-CS, a gate control signal G-CS, and a light control signal B-CS as the driving signals. For example, the gate control signal G-CS includes a vertical start signal, and the data control signal D-CS include a horizontal start signal, an output start signal, and a data enable signal. 
     The signal controller  110  applies the data control signal D-CS to the data driving circuit  300 , and applies the gate control signal G-CS to the gate driving circuit  200 . In addition, the signal controller  110  applies the light control signal B-CS to the backlight unit  500  to control a brightness of light provided to the display panel  400 . 
     In addition, the signal controller  110  applies the gate control signal G-CS to the gate driving circuit  200  through one flexible printed circuit board from among a plurality of flexible printed circuit boards  320 _ 1  to  320 _ k  included in the data driving circuit  300 , but the inventive concept is not limited thereto or thereby. That is, in another embodiment, the signal controller  110  may directly apply the gate control signal G-CS to the gate driving circuit  200 . 
     According to an exemplary embodiment, the signal controller  110  receives image signals RGB, and applies converted image signals D obtained by converting grayscale levels of the image signals RGB to the data driving circuit  300 . The signal controller  110  applies the converted image signals to the data driving circuit  300  that are obtained by converting a data format to a data format appropriate to an interface between the signal controller  110  and the data driving circuit  300 . 
     In addition, the signal controller  110  generates a maximum grayscale image signal for controlling a level of a plurality of gamma driving voltages AVDD 1  to AVDDk, and applies the maximum grayscale image signal to the power supply  120 . Here, the maximum grayscale image signal refers to an image signal (e.g., one image signal) having a maximum grayscale level (e.g., a highest grayscale level) from among the image signals RGB received by the signal controller  110  for a given frame. The power supply  120  generates a plurality of gamma driving voltages AVDD 1  to AVDDk in response to the maximum grayscale image signal, and applies the gamma driving voltages AVDD 1  to AVDDk to the data driving circuit  300 . The operation of the signal controller  110  will be described in more detail with reference to  FIG. 3 . 
     The gate driving circuit  200  generates a plurality of gate signals GS 1  to GSn in response to the gate control signal G-CS provided from the signal controller  110 . The gate signals GS 1  to GSn are sequentially applied to a plurality of pixels PX 11  to PXnm through a plurality of gate lines GL 1  to GLn in a unit of a row. As a result, the pixels PX 11  to PXnm are operated in the unit of the row. 
     The data driving circuit  300  receives the converted image signals D and the data control signal D-CS from the signal controller  110 . The data driving circuit  300  generates a plurality of data voltages corresponding to the converted image signals in response to the data control signal D-CS. The data driving circuit  300  applies the data voltages to the pixels PX 11  to PXnm through a plurality of data lines DL 1  to DLm. 
     In more detail, the data driving circuit  300  includes a plurality of source driving circuits  310 _ 1  to  310 _ k.  In an exemplary embodiment, “k” is an integer greater than 0 and less than m. The source driving circuits  310 _ 1  to  310 _ k  are mounted on the plurality of flexible printed circuit boards  320 _ 1  to  320 _ k.  The flexible printed circuit boards  320 _ 1  to  320 _ k  are connected to the driving circuit board  100  and a non-display area NDA that is adjacent to an upper portion of a display area DA. 
     The source driving circuits  310 _ 1  to  310 _ k  are mounted on the flexible printed circuit boards  320 _ 1  to  320 _ k  by a tape carrier package manner, but the inventive concept is not limited thereto or thereby. That is, in another embodiment, the source driving circuits  310 _ 1  to  310 _ k  may be mounted on the flexible printed circuit boards  320 _ 1  to  320 _ k  by a chip-on-glass manner. 
     The display panel  400  includes the display area DA and the non-display area NDA adjacent to the display area DA. For example, the non-display area NDA may surround the display area DA. 
     The display panel  400  includes the pixels PX 11  to PXnm arranged in the display area DA. In addition, the display panel  400  includes the gate lines GL 1  to GLn, and the data lines DL 1  to DLm insulated from the gate lines GL 1  to GLn and crossing the gate lines GL 1  to GLn. 
     The gate lines GL 1  to GLn are connected to the gate driving circuit  200 , and sequentially receive the gate signals GS 1  to GSn. The data lines DL 1  to DLm are connected to the data driving circuit  300 , and receive the data voltages. 
     The pixels PX 11  to PXnm are arranged at areas (e.g., crossing areas) defined by the gate lines GL 1  to GLn and the data lines DL 1  to DLm. Accordingly, the pixels PX 11  to PXnm are arranged by n rows and m columns. Here, each of “n” and “m” is an integer number greater than 0. 
     Each of the pixels PX 11  to PXnm is connected to a corresponding gate line of the gate lines GL 1  to GLn and a corresponding data line of the data lines DL 1  to DLm. The pixels PX 11  to PXnm receive the data voltages through the data lines DL 1  to DLm in response to the gate signals GS 1  to GSn provided through the gate lines GL 1  to GLn. As a result, the pixels PX 11  to PXnm display grayscale levels corresponding to the data voltages. 
     The backlight unit  500  provides light to the display panel  400 . According to an exemplary embodiment, the backlight unit  500  includes a plurality of group light emitting diodes. Each of the group light emitting diodes provides light to a corresponding area from among the entire area of the display panel  400 . Hereinafter, for convenience, the backlight unit  500  including first, second, third, and fourth group light emitting diodes  510 ,  520 ,  530 , and  540  will be described, but a number of the group light emitting diodes is not limited thereto. 
     The first to fourth group light emitting diodes  510  to  540  output first, second, third, and fourth lights L 1 , L 2 , L 3 , and L 4  to the display panel  400  in response to the backlight control signal B-CS. 
       FIG. 2  is a timing diagram showing an operation of the gate driving circuit  200  and the data driving circuit  300  shown in  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , the signal controller  110  outputs the driving signals. For example, the signal controller  110  applies a vertical start signal Vsync to the gate driving circuit  200  during a frame F. Here, the frame F refers to a period (e.g., a unit frame period), during which one image is displayed. 
     The signal controller  110  applies a signal (e.g., a horizontal synchronization signal Hsync) during horizontal periods HP to the data driving circuit  300  as a row distinction signal. In addition, the signal controller  110  applies a data enable signal DE, which may be maintained or substantially maintained at a high level during a period in which data are output, to the data driving circuit  300  to indicate a data voltage input period. 
     The vertical synchronization signal Vsync is included in the gate control signal G-CS. The horizontal synchronization signal Hsync and the data enable signal DE are included in the data control signal D-CS. The gate control signal G-CS may further include a clock signal and a clock bar signal to generate the gate signals GS 1  to GSn at, for example, the high level. 
     The data voltages DS output from the data driving circuit  300  include positive data voltages having a positive value with respect to a common voltage, and/or negative data voltages having a negative value with respect to the common voltage. During the horizontal periods HP, a part of the data voltages DS applied to the data lines DL 1  to DLm has a positive polarity, and another part of the data voltages DS applied to the data lines DL 1  to DLm has a negative polarity. 
     Meanwhile, the gate signals GS 1  to GSn are sequentially output to correspond to the horizontal periods HP. The data voltages DS are applied to the pixels connected to corresponding gate lines from among the gate lines GL 1  to GLn during each of the horizontal periods HP. 
     In addition, the display panel  400  includes a display period DP during which an image is displayed based on the corresponding frame, and a blank period BP during which no image is displayed. The display period DP for displaying the image corresponds to a period during which the data voltages DS are applied to the data lines DL 1  to DLm, and the data enable signal DE has a high level during the display period DP. The blank period BP corresponds to a period during which the data voltages DS are not applied to the data lines DL 1  to DLm, and the data enable signal DE has a low level during the blank period BP. 
       FIG. 3  is a block diagram showing the signal controller  110  and the power supply  120  shown in  FIG. 1  according to an exemplary embodiment of the present disclosure.  FIG. 4  is a block diagram showing a converted image signal and an emission of light, which are provided to the display panel  400  according to an exemplary embodiment of the present disclosure,  FIG. 5  is a block diagram showing an image signal converter  113  shown in  FIG. 3 , and  FIG. 6  is a block diagram showing the power supply  120  shown in  FIG. 3 . 
     Referring to  FIGS. 3 and 4 , the signal controller  110  includes a memory  111 , a maximum grayscale extractor  112 , an image signal converter  113 , and a dimming part (e.g., a dimmer)  114 . 
     The memory  111  receives the image signals RGB every frame. According to an exemplary embodiment, the memory  111  stores the image signals RGB for each horizontal period in accordance with the frames. That is, the memory  111  stores the image signals corresponding to the data voltages that is to be output for the corresponding horizontal period from among the image signals RGB. Hereinafter, the image signals stored in the memory  111  based on the horizontal period will be described as horizontal image signals. 
     In addition, the memory  111  classifies the horizontal image signals according to each horizontal period into a plurality of group image signals. 
     According to an exemplary embodiment, the memory  111  classifies the horizontal image signals into the group image signals based on the number of the source driving circuits  310 _ 1  to  310 _ k  included in the data driving circuit  300 . 
     As shown in  FIG. 4 , in the case where the data driving circuit  300  includes first to fourth source driving circuits  310 _ 1  to  310 _ 4 , the memory  111  classifies the horizontal image signals according to each horizontal period into four group image signals. 
     According to an exemplary embodiment, the memory  111  classifies the horizontal image signals into the group image signals based on the number of group light emitting diodes included in the backlight unit  500 . As shown in  FIG. 4 , the display panel  400  includes first to fourth light areas  31  to  34  receiving first to fourth lights L 1  to L 4  output from the first to fourth group light emitting diodes  510  to  540 , respectively. 
     Hereinafter, for convenience, the memory  111  that classifies the horizontal image signals into first to fourth group image signals sRGB 1  to sRGB 4  will be described. Accordingly, first to fourth group pixels are respectively connected to the first to fourth source driving circuits  310 _ 1  to  310 _ k  in each horizontal period. 
     The memory  111  applies the first to fourth group image signals sRGB 1  to sRGB 4  to the maximum grayscale extractor  112  and the image signal converter  113 . 
     The maximum grayscale extractor  112  receives the group image signals from the memory  111 , and extracts a maximum grayscale image signal having a maximum grayscale level (e.g., a highest grayscale level) from the group image signals. 
     In more detail, the maximum grayscale extractor  112  receives the first to fourth group image signals sRGB 1  to sRGB 4 . The maximum grayscale extractor  112  extracts a first maximum grayscale image signal Dm 1  having the maximum grayscale level (e.g., the highest grayscale level) from among the first group image signals sRGB 1 . The maximum grayscale extractor  112  extracts a second maximum grayscale image signal Dm 2  having the maximum grayscale level (e.g., the highest grayscale level) from among the second group image signals sRGB 2 . The maximum grayscale extractor  112  extracts a third maximum grayscale image signal Dm 3  having the maximum grayscale level (e.g., the highest grayscale level) from among the third group image signals sRGB 3 . The maximum grayscale extractor  112  extracts a fourth maximum grayscale image signal Dm 4  having the maximum grayscale level (e.g., the highest grayscale level) from among the fourth group image signals sRGB 4 . 
     The maximum grayscale extractor  112  applies the first to fourth maximum grayscale image signals Dm 1  to Dm 4  extracted from the first to fourth group image signals sRGB 1  to sRGB 4  to the image signal converter  113 , the dimming part  114 , and the power supply  120 . 
     The image signal converter  113  receives the first to fourth group image signals sRGB 1  to sRGB 4  from the memory  111 , and receives the first to fourth maximum grayscale image signals Dm 1  to Dm 4  from the maximum grayscale extractor  112 . 
     The image signal converter  113  converts the first to fourth group image signals sRGB 1  to sRGB 4  to first to fourth converted image signals D 1  to D 4  in response to the first to fourth maximum grayscale image signals Dm 1  to Dm 4 . 
     For example, the image signal converter  113  converts the grayscale level of the first maximum grayscale image signal Dm 1  having the maximum grayscale level (e.g., the highest grayscale level) from among the first group image signals sRGB 1  toward a white grayscale level based on a reference gamma curve, to allow the first maximum grayscale image signal Dm 1  to be expressed in the data driving circuit  300 . In addition, the image signal converter  113  converts the grayscale level of first group image signals sRGB 1 , except for the first maximum grayscale image signal Dm 1 , toward the white grayscale level based on the reference gamma curve, to allow the first group image signals sRGB 1 , except for the first maximum grayscale image signal Dm 1 , to be expressed in the data driving circuit  300 . 
     That is, the image signal converter  113  generates the first converted image signals D 1  obtained by controlling the first group image signals sRGB 1  toward the white grayscale level based on the reference gamma curve. The image signal converter  113  converts the second to fourth group image signals sRGB 2  to sRGB 4  to the second to fourth converted image signals D 2  to D 4  using the above-described method. Accordingly, detailed descriptions of the conversion of the second to fourth group image signals sRGB 2  to sRGB 4  to the second to fourth converted image signals D 2  to D 4  will be omitted. 
     Referring to  FIG. 5 , the image signal converter  113  includes a register  113   a  and a look-up table  113   b.    
     The register  113   a  may extract (e.g., read out) the first to fourth converted image signals D 1  to D 4  stored in the look-up table  113   b  in response to the first to fourth group image signals sRGB 1  to sRGB 4 . The register  113   a  applies the extracted (e.g., read-out) first to fourth converted image signals D 1  to D 4  to the first to fourth flexible printed circuit boards  320 _ 1  to  320 _ k,  respectively, as shown in  FIG. 4 . 
     The look-up table  113   b  stores the converted image signals obtained by converting the grayscale level of the corresponding group image signal toward the white grayscale level in accordance with the gamma curve. The look-up table  113   b  stores (e.g., previously stores) converted image signals respectively corresponding to 0 to 255 grayscale levels. 
     Therefore, the register  113   a  may extract (e.g., read out) the converted image signal stored in the look-up table  113   b  based on the grayscale level of the corresponding group image signal. 
     The dimming part  114  receives the first to fourth maximum grayscale image signals Dm 1  to Dm 4  from the maximum grayscale extractor  112 . The dimming part  114  controls a brightness of light generated by the backlight unit  500  in response to the first to fourth maximum grayscale image signals Dm 1  to Dm 4 . 
     According to an exemplary embodiment, the dimming part  114  performs a local dimming individually on the first to fourth group light emitting diodes  510  to  540 . 
     For example, the dimming part  114  performs the local dimming on each of the first to fourth group light emitting diodes  510  to  540 , and thus, the first to fourth lights L 1  to L 4  emitted from the first to fourth group light emitting diodes  510  to  540  may have different brightnesses from each other. As a result, the lights having different brightnesses from each other may be provided to the light areas B 1  to B 4  of the display panel  400 , respectively. 
     In more detail, the dimming part  114  generates first to fourth light control signals B-CS 1  to B-CS 4  in response to the first to fourth maximum grayscale image signals Dm 1  to Dm 4 . The first group light emitting diodes  510  emit the first light L 1  in response to the first light control signal B-CS 1 . The second group light emitting diodes  520  emit the second light L 2  in response to the second light control signal B-CS 2 . The third group light emitting diodes  530  emit the third light L 3  in response to the third light control signal B-CS 3 . The fourth group light emitting diodes  540  emit the fourth light L 4  in response to the fourth light control signal B-CS 4 . 
     The power supply  120  receives the first to fourth maximum grayscale image signals Dm 1  to Dm 4  from the maximum grayscale extractor  112 . The power supply  120  generates first to fourth gamma driving voltages AVDD 1  to AVDD 4  from a reference gamma driving voltage in response to the first to fourth maximum grayscale image signals Dm 1  to Dm 4 . Here, the reference gamma driving voltage may be used to express the maximum grayscale level (e.g., the 255 grayscale level) according to a normal gamma curve. 
     According to an exemplary embodiment, the power supply  120  generates the first to fourth gamma driving voltages AVDD 1  to AVDD 4 , which have levels that are the same or substantially the same as each other or have at least one different level, in response to the first to fourth maximum grayscale image signals Dm 1  to Dm 4 . 
     Referring to  FIG. 6 , the power supply  120  includes a register  121 , a look-up table  122 , a decoder  123 , a switch array  124 , and a resistor string  125 . 
     The register  121  may extract (e.g., read out) a switching control signal QS stored in the look-up table  122  in response to the maximum grayscale image signal. The register  121  applies the extracted (e.g., read-out) switching control signal QS to the decoder  123 . 
     The look-up table  122  stores (e.g., previously stores) a plurality of switching control signals QS corresponding to each of the grayscale levels of the maximum grayscale image signal. That is, the look-up table  122  stores (e.g., previously stores) the switching control signals QS respectively corresponding to 0 to 255 grayscale levels. In an embodiment, the switching control signals QS may be realized as a digital signal of 8-bits. 
     The decoder  123  decodes the switching control signal QS provided from the register  121 , and applies the decoded switching control signal QS to a plurality of output pins P 0  to P 255 . The decoder  123  includes, for example, 256 output pins P 0  to P 255  corresponding to a number of the switching control signals QS of 8-bits. 
     The switch array  124  includes a plurality of switches T 0  to T 255 . Gate terminals G of the switches T 0  to T 255  are electrically connected to the output pins P 0  to P 255 , respectively. The gate terminals G of the switches T 0  to T 255  receive the decoded switching control signals through the output pins P 0  to P 255 . Drain terminals D of the switches T 0  to T 255  are electrically connected to voltage-division voltage nodes n 0  to n 255 , respectively, and resistors R 1  to R 255  included in the resistor string  125  are connected between corresponding ones of the voltage-division voltage nodes n 0  to n 255 . Source terminals S of the switches T 0  to T 255  are commonly connected to a gamma supply line VSL. 
     The gamma driving voltage AVDD according to each maximum grayscale image signal may be set to one gamma driving voltage AVDD of the voltage-division voltages. That is, since one switch of the switches T 0  to T 255  is turned on in response to the decoded switching control signal, one voltage-division voltage of the voltage-division voltages may be selected as the gamma driving voltage AVDD. 
     As a result, the gamma driving voltage AVDD may decrease from the reference gamma driving voltage VDD of the maximum grayscale image signal to at or near an analog gamma compensation voltage. 
     The resistor string  125  includes the resistors R 1  to R 255  connected to each other in series between the reference gamma driving voltage VDD and a ground voltage GND. The resistor string  125  generates the voltage-division voltages having different levels from each other through the voltage-division voltage nodes n 0  to n 255  arranged between the resistors R 1  to R 255 . 
       FIG. 7  is a table showing an operation of a signal controller and a backlight unit (e.g., a backlight source) according to an exemplary embodiment of the present disclosure,  FIG. 8  is a graph showing a first maximum grayscale image signal shown in  FIG. 7 ,  FIG. 9  is a graph showing a third maximum grayscale image signal shown in  FIG. 7 , and  FIG. 10  is a graph showing a fourth maximum grayscale image signal shown in  FIG. 7 . 
     The table shown in  FIG. 7  shows that the gamma driving voltage AVDD and the light L are controlled depending on the grayscale level of the maximum grayscale image signal. In the graphs shown in  FIGS. 8 to 10 , horizontal axes indicate the gamma compensation voltage V corresponding to each grayscale level, and vertical axes indicate the grayscale level T. 
     Hereinafter, the first, the third, and the fourth maximum grayscale image signals Dm 1 , Dm 3 , and Dm 4  from among the first to fourth maximum grayscale image signals Dm 1  to Dm 4  shown in  FIG. 3  will be described in more detail. 
     According to an exemplary embodiment, the gamma driving voltage AVDD and the light L may be controlled depending on the grayscale level of the maximum grayscale image signal. 
     Referring to  FIGS. 7 and 8 , the level of the gamma driving voltage AVDD decreases based on the first maximum grayscale image signal Dm 1 , and the brightness level of the light L is maintained or substantially maintained at a maximum level. 
     In more detail, the first maximum grayscale image signal Dm 1  may have a first grayscale level G 1 . In this case, the first grayscale level G 1  corresponds to a grayscale level between a first reference grayscale level C and a second reference grayscale level B. For example, the first reference grayscale level C is at about 250 grayscale level, and the second reference grayscale level B is at about 180 grayscale level. 
     According to an exemplary embodiment, in the case where the first maximum grayscale image signal Dm 1  has the grayscale level between the first reference grayscale level C and the second reference grayscale level B, the power supply  120  outputs the first gamma driving voltage AVDD 1  obtained by controlling the reference gamma driving voltage. That is, the power supply  120  outputs the first gamma driving voltage AVDD 1  obtained by lowering a level of a first driving voltage V 1   a , which is the reference gamma driving voltage, to a level of a second driving voltage V 1   b.    
     As a result, the data driving circuit  300  (e.g., refer to  FIG. 1 ) generates second gamma compensation voltages VB, which are applied to the first group pixels, based the first gamma driving voltage AVDD 1  and the first converted image signals D 1  in accordance with a second gamma curve C 2 . A first gamma curve C 1  may be a gamma curve of normal gamma compensation voltages VA according to normal image signals. 
     In this case, as shown in  FIG. 8 , a voltage level of the second gamma compensation voltages VB generated based on the first gamma driving voltage AVDD 1  and the first converted image signals D 1  may be lower than a voltage level of the first gamma compensation voltages VA generated based on the reference gamma driving voltage and the reference image signals. As a result, power consumption used to drive the display device DD may be reduced more than when the gamma compensation voltages are generated based on the reference gamma driving voltage. 
     As described above, the reference gamma driving voltage may be the voltage (e.g., a DC voltage) used to generate the maximum grayscale level of the normal image signal regardless of the maximum grayscale image signal. The reference image signals may be, but not limited to, image signals corresponding to a plurality of group images in which the grayscale levels thereof are not changed. 
     The dimming part  114  outputs the first light control signal B-CS 1  to maintain or substantially maintain the brightness of the first light L 1  at a first level (e.g., 100%), because the first maximum grayscale image signal Dm 1  has the grayscale level between the first reference grayscale level C and the second reference grayscale level B. The first level (e.g., 100%) refers to the light having a maximum brightness. In the case where the brightness of the first light L 1  is maintained or substantially maintained at the first level (e.g., 100%), the first group light emitting diodes  510  may be operated at a maximum power. 
     As described above, in the case where the grayscale level of the maximum grayscale image signal has a high grayscale level corresponding to between the first reference grayscale level C and the second reference grayscale level B, the brightness of the light is maintained or substantially maintained at the maximum brightness in accordance with a human visual sensation characteristic of a user. In addition, the level of the gamma driving voltage AVDD applied to the data driving circuit  300  may be changed to be lower than that of the reference gamma driving voltage. 
     Referring to  FIGS. 7 and 9 , the level of the gamma driving voltage AVDD is maintained or substantially maintained at the reference gamma driving voltage based on the third maximum grayscale image signal Dm 3 , and the brightness of the light is lowered. 
     In more detail, the third maximum grayscale image signal Dm 3  has a third grayscale level G 3 . In this case, the third grayscale level G 3  has a grayscale level between the second reference grayscale level B and a third reference grayscale level A. In an exemplary embodiment, the second reference grayscale level B is at about 190 grayscale level, and the third reference grayscale level A is at about 128 grayscale level. 
     According to an exemplary embodiment, in the case where the third maximum grayscale image signal Dm 3  has the grayscale level between the second reference grayscale level B and the third reference grayscale level A, the power supply  120  outputs the reference gamma driving voltage as the third gamma driving voltage AVDD 3 . That is, the power supply  120  outputs the first driving voltage V 1   a , which is the reference gamma driving voltage, as the third gamma driving voltage AVDD 3 . 
     As a result, the data driving circuit  300  (e.g., refer to  FIG. 1 ) generates third gamma compensation voltages VC, which are applied to the third group pixels, based on the third gamma driving voltage AVDD 3  and the third converted image signals D 3  in accordance with a third gamma curve C 3 . 
     The dimming part  114  outputs the third light control signal B-CS 3  to lower the brightness of the third light L 3  to a second level (e.g., 50%), because the third maximum grayscale image signal Dm 3  has the grayscale level between the second reference grayscale level B and the third reference grayscale level A. Because the brightness of the third light L 3  is lowered to the second level (e.g., 50%) from the first level (e.g., 100%), the power consumption in the third group light emitting diodes  530  may be reduced. 
     As described above, in the case where the grayscale level of the maximum grayscale image signal has an intermediate grayscale level corresponding to between the second reference grayscale level B and the third reference grayscale level A, the brightness level of the light may be controlled to be lowered. In addition, the level of the gamma driving voltage AVDD applied to the data driving circuit  300  is maintained or substantially maintained at the reference gamma driving voltage. In more detail, because the brightness level of the light is controlled to be lowered, the level of the gamma compensation voltages may be increased to compensate for the lowered brightness level of the light. That is, because the level of the gamma compensation voltages increases to compensate for the lower brightness level of the light, it may be undesirable to control the level of the gamma driving voltage AVDD used to generate the gamma compensation voltages. 
     Referring to  FIGS. 7 and 10 , the level of the gamma driving voltage AVDD is lowered based on the fourth maximum grayscale image signal Dm 4 , and therefore, the brightness of the light is lowered. 
     In more detail, the fourth maximum grayscale image signal Dm 4  has a third grayscale level G 4 . In this case, the fourth grayscale level G 4  has a grayscale level between the third reference grayscale level A and a minimum grayscale level (e.g., a 0 grayscale level). 
     According to an exemplary embodiment, in the case where the fourth maximum grayscale image signal Dm 4  has the grayscale level between the third reference grayscale level A and the minimum grayscale level, the power supply  120  outputs the fourth gamma driving voltage AVDD 4  obtained by controlling the reference gamma driving voltage. That is, the power supply  120  outputs the fourth gamma driving voltage AVDD 4  obtained by lowering the level of the first driving voltage V 1   a , which is the reference gamma driving voltage, to a level of a fourth driving voltage V 1   d.    
     As a result, the data driving circuit  300  (e.g., refer to  FIG. 1 ) generates fourth gamma compensation voltages VD, which are applied to the fourth group pixels, based on the fourth gamma driving voltage AVDD 4  and the fourth converted image signals D 4  in accordance with a fourth gamma curve C 4 . 
     In this case, as shown in  FIG. 10 , a voltage level of the fourth gamma compensation voltages VD generated based on the fourth gamma driving voltage AVDD 4  and the fourth converted image signals D 4  may be lower than the voltage level of the first gamma compensation voltages VA generated based on the reference gamma driving voltage and the reference image signals. As a result, the power consumption used to drive the display device DD may be reduced more than when the gamma compensation voltages are generated based on the reference gamma driving voltage. 
     The dimming part  114  outputs the fourth light control signal B-CS 4  to lower the brightness of the fourth light L 4  to a third level (e.g., 25%), because the fourth maximum grayscale image signal Dm 4  has the grayscale level between the third reference grayscale level A and the minimum grayscale level. Because the brightness of the fourth light L 4  is lowered to the third level (e.g., 25%) from the first level (e.g., 100%), the power consumption in the fourth group light emitting diodes  540  may be reduced. 
     As described above, in the case where the grayscale level of the maximum grayscale image signal has a low grayscale level corresponding to between the third reference grayscale level A and the minimum grayscale level, the gamma driving voltage AVDD and the brightness level of the light may be controlled to be lowered. 
     In more detail, in the case where the image is displayed at the intermediate or high grayscale level, the brightness level of the light L is lowered, and it may be undesirable to change the level of the gamma driving voltage AVDD used to compensate for the light L. However, in the case where the image is displayed at the low grayscale level, variation (e.g., significant variation) in visual characteristics may not be recognized by the user, even though the brightness level of the light L and the level of the gamma driving voltage AVDD are lowered. 
     According to an exemplary embodiment, the gamma driving voltage may be controlled every horizontal period, and the brightness of the light may be controlled every frame. 
       FIG. 11  is a flowchart showing an operation of the signal controller  110  and the power supply  120  shown in  FIG. 3  to output a final gamma driving voltage. 
     Referring to  FIGS. 3 and 11 , the signal controller  110  calculates a maximum grayscale range that is variable between the maximum grayscale image signals during a horizontal blank period H (e.g., refer to  FIG. 2 ) (S 110 ). Here, the horizontal blank period H corresponds to a period obtained by subtracting a period in which the data voltage is output from the horizontal period HP shown in  FIG. 2 . 
     The signal controller  110  measures a time during which the minimum grayscale level is converted to the maximum grayscale level (S 120 ). 
     The signal controller  110  calculates the number of the horizontal blank periods H, which is used to convert the minimum grayscale level to the maximum grayscale level (S 130 ). 
     The signal controller  110  stores the horizontal image signals based on the calculated number of the horizontal blank periods H (S 140 ). For example, in the case where three horizontal blank periods H are used to convert the minimum grayscale level to the maximum grayscale level, the signal controller  110  stores three horizontal image signals. 
     The signal controller  110  calculates the first gamma driving voltage V 1  corresponding to the maximum grayscale image signal from among the group image signals corresponding to one horizontal period (S 150 ). 
     The signal controller  110  calculates a minimum gamma driving voltage V 2  used by the one horizontal period based on the time used to convert the minimum grayscale level to the maximum grayscale level (S 160 ). 
     The signal controller  110  compares the first gamma driving voltage V 1  and the second gamma driving voltage V 2 , and selects one of the first gamma driving voltage V 1  and the second gamma driving voltage V 2  during the one horizontal period according to the compared result (S 170 ). 
     The power supply  120  outputs the selected gamma driving voltage (S 180 ). 
       FIG. 12  is block diagram showing a converted image signal and an emission of light, which are provided to a display panel according to another exemplary embodiment of the present disclosure, and  FIG. 13  is a table showing an operation of a signal controller and a backlight unit (e.g., a backlight source) according to another exemplary embodiment of the present disclosure. 
     Referring to  FIGS. 12 and 13 , a data driving circuit  300  and a display panel  400  shown in  FIG. 12  may have the same or substantially the same structure as those of the data driving circuit  300  and the display panel  400  shown in  FIG. 4 , and thus, detailed descriptions of the data driving circuit  300  and the display panel  400  will not be repeated. 
     A backlight unit (e.g., a backlight source)  600  shown in  FIG. 12  is realized as a single group of light emitting diodes different from those of the backlight unit  500  shown in  FIG. 4 . 
     In more detail, the backlight unit  600  may provide the light at a constant or substantially constant brightness to the entire area of the display panel  400 . That is, the backlight unit  600  provides the light having the constant or substantially constant brightness using a global dimming, rather than the local dimming of the backlight unit  500  shown in  FIG. 4 . 
     The dimming part  114  (e.g., refer to  FIG. 3 ) generates a light control signal B-CS, and applies the light control signal B-CS to the backlight unit  600  to control an operation of the backlight unit  600 . 
     Referring to  FIG. 13 , the dimming part  114  generates the light control signal B-CS to lower the brightness level of the light L in the case where the grayscale levels G 1 , G 3 , and G 4  of the first, third, and fourth maximum grayscale image signals Dm 1 , Dm 3 , and Dm 4  correspond to the low grayscale level. In this case, the power supply  120  (e.g., refer to  FIG. 3 ) outputs the fourth gamma driving voltage AVDD 4  obtained by lowering the level of the first driving voltage V 1   a  to the level of the fourth driving voltage V 1   d . The low grayscale level may have the grayscale level between the minimum grayscale level (e.g., the 0 grayscale level) and the third reference grayscale level A. 
       FIG. 14  is a block diagram showing a signal controller and a power supply according to another exemplary embodiment of the present disclosure, and  FIG. 15  is a table showing an operation of a signal controller and a backlight unit (e.g., a backlight source) according to another exemplary embodiment of the present disclosure. 
     A display device shown in  FIGS. 14 and 15  may be operated in a normally white mode WB. The term “normally white mode WB” as used herein refers to a case where the grayscale level of the image signal corresponding to the data voltage is lowered as the level of the data voltage applied to the pixel decreases. 
     Referring to  FIG. 14 , a signal controller  1000  includes a memory  1100 , a minimum grayscale extractor  1200 , an image signal converter  1300 , and a dimming part (e.g., a dimmer)  1400 . The signal controller  1000  shown in  FIG. 14  may have the same or substantially the same structure and function as those of the signal controller  110  shown in  FIG. 3 , except for the minimum grayscale extractor  1200 . 
     The minimum grayscale extractor  1200  receives first to fourth group image signals wRGB 1  to wRGB 4  from the memory  1100 . The minimum grayscale extractor  1200  extracts a first minimum grayscale image signal Dn 1  having a minimum grayscale level (e.g., a lowest grayscale level) from among the first group image signals wRGB 1 . The minimum grayscale extractor  1200  extracts a second minimum grayscale image signal Dn 2  having the minimum grayscale level (e.g., the lowest grayscale level) from among the second group image signals wRGB 2 . The minimum grayscale extractor  1200  extracts a third minimum grayscale image signal Dn 3  having the minimum grayscale level (e.g., the lowest grayscale level) from among the third group image signals wRGB 3 . The minimum grayscale extractor  1200  extracts a fourth minimum grayscale image signal Dn 4  having the minimum grayscale level (e.g., the lowest grayscale level) from among the fourth group image signals wRGB 4 . 
     The minimum grayscale extractor  1200  applies the first to fourth minimum grayscale image signals Dn 1  to Dn 4  extracted from the first to fourth group image signals wRGB 1  to wRGB 4  to each of the image signal converter  1300 , the dimming part  1400 , and a power supply  2000 . 
     For example, the image signal converter  1300  converts the grayscale level of the first minimum grayscale image signal Dn 1  having the minimum grayscale level from among the first group image signals wRGB 1  toward a black grayscale level based on a reference gamma curve, to allow the first minimum grayscale image signal Dn 1  to be expressed in the data driving circuit  300 . In addition, the image signal converter  1300  converts the grayscale level of first group image signals wRGB 1 , except for the first minimum grayscale image signal Dn 1 , toward the black grayscale level based on the reference gamma curve, to allow the first group image signals wRGB 1 , except for the first minimum grayscale image signal Dn 1 , to be expressed in the data driving circuit  300 . 
     That is, the image signal converter  1300  generates first converted image signals D 1  obtained by controlling the first group image signals wRGB 1  toward the black grayscale level based on the reference gamma curve. The image signal converter  1300  converts the second to fourth group image signals wRGB 2  to wRGB 4  to second to fourth converted image signals D 2  to D 4  using the above-mentioned method. Accordingly, detailed descriptions of the conversion of the second to fourth group image signals wRGB 2  to wRGB 4  to the second to fourth converted image signals D 2  to D 4  will be omitted. 
     The power supply  2000  shown in  FIG. 14  receives the first to fourth minimum grayscale image signals Dn 1  to Dn 4  from the minimum grayscale extractor  1200 . The power supply  2000  generates first to fourth gamma driving voltages AVDD 1  to AVDD 4  from the reference gamma driving voltage in response to the first to fourth minimum grayscale image signals Dn 1  to Dn 4 . 
     According to an exemplary embodiment, the power supply  2000  generates the first to fourth gamma driving voltages AVDD 1  to AVDD 4 , which have levels that are the same or substantially the same as each other or have at least one different level, in response to the first to fourth minimum grayscale image signals Dn 1  to Dn 4 . That is, the power supply  2000  generates the gamma driving voltages having the level lower than that of the reference gamma driving voltage in accordance with the first to fourth minimum grayscale image signals Dn 1  to Dn 4 . As a result, the overall power consumption of the display device may be reduced. 
     Referring to  FIG. 15 , in the case where the first minimum grayscale image signal Dn 1  has the grayscale level between the minimum grayscale level (e.g., a 0 grayscale level) and the third reference grayscale level A, the signal controller  1000  generates the first light control signal B-CS 1  to lower the brightness of the first light L 1  from the maximum brightness. As a result, the first group light emitting diodes  510  emits the first light L 1  having the brightness lowered to the third level (e.g., 25%) from the first level (e.g., 100%) in response to the first light control signal B-CS 1 . In addition, the power supply  2000  generates the first gamma driving voltage AVDD 1  obtained by lowering a first driving voltage V 2   a , which is the reference gamma driving voltage, to a second driving voltage V 2   b.    
     For example, in the case where the third minimum grayscale image signal Dn 3  has the grayscale level between the third reference grayscale level A and the second reference grayscale level B, the signal controller  1000  generates the third light control signal B-CS 3  to lower the brightness of the third light L 3  from the maximum brightness. As a result, the third group light emitting diodes  530  emits the third light L 3  having the brightness lowered to the second level (e.g., 50%) from the first level (e.g., 100%) in response to the third light control signal B-CS 3 . In addition, the power supply  2000  maintains or substantially maintains the first driving voltage V 2   a  that is the reference gamma driving voltage. 
     As an example, in the case where the fourth minimum grayscale image signal Dn 4  has the grayscale level between the second reference grayscale level B and the first reference grayscale level C, the signal controller  1000  generates the fourth light control signal B-CS 4  to maintain or substantially maintain the fourth light L 4  at the maximum brightness. In addition, the power supply  2000  generates the fourth gamma driving voltage AVDD 4  obtained by lowering the first driving voltage V 2   a , which is the reference gamma driving voltage, to the fourth driving voltage V 2   d.    
     The electronic or electric devices (e.g., the signal controller, the maximum grayscale extractor, the minimum grayscale extractor, the image signal converter, the dimming part, etc.) and/or any other relevant devices or components according to embodiments of the inventive concept described herein may be implemented utilizing any suitable hardware, firmware (e.g. an application-specific integrated circuit), software, or a combination of software, firmware, and hardware. For example, the various components of these devices may be formed on one integrated circuit (IC) chip or on separate IC chips. Further, the various components of these devices may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or formed on one substrate. Further, the various components of these devices may be a process or thread, running on one or more processors, in one or more computing devices, executing computer program instructions and interacting with other system components for performing the various functionalities described herein. The computer program instructions are stored in a memory which may be implemented in a computing device using a standard memory device, such as, for example, a random access memory (RAM). The computer program instructions may also be stored in other non-transitory computer readable media such as, for example, a CD-ROM, flash drive, or the like. Also, a person of skill in the art should recognize that the functionality of various computing devices may be combined or integrated into a single computing device, or the functionality of a particular computing device may be distributed across one or more other computing devices without departing from the spirit and scope of the exemplary embodiments of the inventive concept. 
     Although exemplary embodiments of the present invention have been described, it is to be understood that the present invention should not be limited to these exemplary embodiments, but that various changes and modifications may be made by one ordinary skilled in the art without departing from the spirit and scope of the present invention as defined by the following claims, and their equivalents.