Patent Publication Number: US-2023154420-A1

Title: Light source apparatus, display apparatus including the same and method of compensating luminance difference of the same

Description:
This application is a continuation of U.S. patent application Ser. No. 17/235,105, filed on Apr. 20, 2021, which is a continuation of U.S. patent application Ser. No. 16/725,202, filed on Dec. 23, 2019, which claims priority to Korean Patent Application No. 10-2018-0171869, filed on Dec. 28, 2018 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 
     Exemplary embodiments of the invention relate to a light source apparatus, a display apparatus including the light source apparatus and a method of compensating luminance difference of the display apparatus. More particularly, exemplary embodiments of the invention relate to a light source apparatus compensating luminance difference of light source blocks, a display apparatus including the light source apparatus and a method of compensating luminance difference of the display apparatus. 
     2. Description of the Related Art 
     In a local dimming method, a degree of turning-on of a light source is determined corresponding to a luminance of a block of input image data to reduce a power consumption of a display apparatus. 
     SUMMARY 
     To operate the local dimming method, each light source blocks may be independently controlled. When the number of the light source block controllers is same as the number of the light source blocks, a manufacturing cost of a light source apparatus may be increased and a complexity of the light source apparatus may be increased. 
     Exemplary embodiments of the invention provide a light source apparatus using an active matrix method to reduce a manufacturing cost and a complexity and effectively compensating luminance difference of light source blocks. 
     Exemplary embodiments of the invention also provide a display apparatus including the light source apparatus. 
     Exemplary embodiments of the invention also provide a method of compensating luminance difference of the light source apparatus. 
     In an exemplary embodiment of a light source apparatus according to the invention, the light source apparatus includes a plurality of light source gate lines extending in a first direction, a plurality of light source data lines extending in a second direction crossing the first direction, a plurality of light source emission lines, a plurality of feedback lines and a plurality of light source blocks. At least one of the plurality of light source blocks is connected to a light source gate line of the plurality of light source gate lines, a light source data line of the plurality of light source data lines, a light source emission line of the plurality of light source emission lines and a feedback line of the plurality of feedback lines. 
     In an exemplary embodiment, the feedback line may be commonly connected to light source blocks of the plurality of light source blocks disposed in a light source block column. 
     In an exemplary embodiment, a first end portion of the feedback line may be connected to the light source blocks disposed in the light source block column and a second end portion of the feedback line is connected to a feedback resistor. The feedback resistor may be connected between a power voltage applying terminal of a light source block of the light source blocks and the second end portion of the feedback line. 
     In an exemplary embodiment, a light source block of the plurality of light source blocks may include a light emitting element, a first switching element including a control electrode connected to the light source gate line, an input electrode connected to the light source data line and an output electrode connected to a control electrode of a second switching element, the second switching element including the control electrode connected to the output electrode of the first switching element, an input electrode connected to an output electrode of a third switching element and an output electrode connected to a ground and the third switching element including a control electrode connected to the light source emission line, an input electrode connected to the light emitting element and the output electrode connected to the input electrode of the second switching element. 
     In an exemplary embodiment, the feedback line may extend in a direction parallel to the light source data line. 
     In an exemplary embodiment of a display apparatus according to the invention, the display apparatus includes a display panel, a gate driver, a data driver, a light source apparatus and a light source driver. The display panel displays an image. The gate driver applies a gate signal to the display panel. The data driver applies a data voltage to the display panel. The light source apparatus provides light to the display panel. The light source driver drives the light source apparatus. The light source apparatus includes a plurality of light source gate lines extending in a first direction, a plurality of light source data lines extending in a second direction crossing the first direction, a plurality of light source emission lines, a plurality of feedback lines and a plurality of light source blocks. At least one of the plurality of light source blocks is connected to a light source gate line of the plurality of light source gate lines, a light source data line of the plurality of light source data lines, a light source emission line of the plurality of light source emission lines and a feedback line of the plurality of feedback lines. 
     In an exemplary embodiment, the feedback line may be commonly connected to light source blocks of the plurality of light source blocks disposed in a light source block column. 
     In an exemplary embodiment, a first end portion of the feedback line may be connected to the light source blocks disposed in the light source block column and a second end portion of the feedback line is connected to a feedback resistor. The feedback resistor may be connected between a power voltage applying terminal of the light source block and the second end portion of the feedback line. 
     In an exemplary embodiment, a light source block of the plurality of light source blocks may include a light emitting element, a first switching element including a control electrode connected to the light source gate line, an input electrode connected to the light source data line and an output electrode connected to a control electrode of a second switching element, the second switching element including the control electrode connected to the output electrode of the first switching element, an input electrode connected to an output electrode of a third switching element and an output electrode connected to a ground and the third switching element including a control electrode connected to the light source emission line, an input electrode connected to the light emitting element and the output electrode connected to the input electrode of the second switching element. 
     In an exemplary embodiment, the light source block may include a light emitting element. The light source driver may include a first switching element including a control electrode connected to the light source gate line, an input electrode connected to the light source data line and an output electrode connected to a control electrode of a second switching element, the second switching element including the control electrode connected to the output electrode of the first switching element, an input electrode connected to an output electrode of a third switching element and an output electrode connected to a ground and the third switching element including a control electrode connected to the light source emission line, an input electrode connected to the light emitting element and the output electrode connected to the input electrode of the second switching element. 
     In an exemplary embodiment, the feedback line may extend in a direction parallel to the light source data line. 
     In an exemplary embodiment, the display apparatus may further include a plurality of light source registers which stores sensed currents of the light source blocks of the plurality of light source blocks which are fed back through the feedback line and a light source compensator including a compensation controller which receives the sensed currents of the light source blocks which are stored in the plurality of light source registers and generates a compensated light source data signal for compensating luminance difference between the light source blocks. 
     In an exemplary embodiment, the light source compensator may include a first light source register which stores a first sensed current in response to a first light source gate signal through a first feedback line, a second light source register which stores a second sensed current in response to the first light source gate signal through a second feedback line, a third light source register which stores a third sensed current in response to a second light source gate signal through the first feedback line and a fourth light source register which stores a fourth sensed current in response to the second light source gate signal through the second feedback line. 
     In an exemplary embodiment, the light source compensator may further include a first error amplifier which compares a signal transmitted through the first feedback line to a reference voltage and a first analog to digital converter (“ADC”) connected to the first error amplifier. The first ADC may be connected to the first light source register and the third light source register. 
     In an exemplary embodiment, the light source compensator may further include a second error amplifier which compares a signal transmitted through the second feedback line to the reference voltage and a second ADC connected to the second error amplifier. The second ADC may be connected to the second light source register and the fourth light source register. 
     In an exemplary embodiment, the display apparatus may further include a driving controller which controls driving timings of the gate driver, the data driver and the light source driver. The light source compensator may be disposed in the driving controller. 
     In an exemplary embodiment, the light source compensator may be disposed in the light source driver. 
     In an exemplary embodiment, the compensated light source data signal may include luminance data bits representing a target luminance according to a local dimming method and compensation data bit for compensating the luminance difference between the light source blocks. 
     In an exemplary embodiment of a method of compensating luminance difference of a light source apparatus, the method includes applying a plurality of light source gate signals to a plurality of light source gate lines, applying a plurality of light source data signals to a plurality of light source data lines, applying a light source emission signal to a plurality of light source emission lines, sensing currents flowing through a plurality of light source blocks through a plurality of feedback lines and generating a compensated light source data signal using the sensed currents through feedback lines of the plurality of feedback lines. 
     In an exemplary embodiment, the currents flowing through the plurality of light source blocks may be sensed in an initial period when a display apparatus is turned on. 
     According to the light source apparatus, the display apparatus and the method of compensating luminance difference of the light source apparatus, the light source apparatus may be driven using the active matrix method so that the manufacturing cost and the complexity of the light source apparatus may be reduced. The light source apparatus includes the light source blocks connected to the light source gate lines, the light source data lines, the light source emission lines and the feedback line and the currents of the light source blocks are fed back so that the luminance difference between the light source blocks may be compensated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the invention will become more apparent by describing in detailed exemplary embodiments thereof with reference to the accompanying drawings, in which: 
         FIG.  1    is a block diagram illustrating an exemplary embodiment of a display apparatus according to the invention; 
         FIG.  2    is a conceptual diagram illustrating a light source apparatus of  FIG.  1   ; 
         FIG.  3    is a circuit diagram illustrating a light source block of  FIG.  2   ; 
         FIG.  4    is a timing diagram illustrating a method of sensing a current of the light source block of  FIG.  2   ; 
         FIG.  5    is a flowchart diagram illustrating a method of compensating luminance difference of the light source apparatus of  FIG.  2   ; 
         FIG.  6    is a circuit diagram illustrating light source registers storing sensed currents of light source blocks in a first light source block column of  FIG.  2   ; 
         FIG.  7    is a circuit diagram illustrating light source registers storing sensed currents of light source blocks in a second light source block column of  FIG.  2   ; 
         FIG.  8    is a circuit diagram illustrating light source registers storing sensed currents of light source blocks in a third light source block column of  FIG.  2   ; 
         FIG.  9    is a circuit diagram illustrating light source registers storing sensed currents of light source blocks in a fourth light source block column of  FIG.  2   ; 
         FIG.  10    is a circuit diagram illustrating light source registers storing sensed currents of light source blocks in a fifth light source block column of  FIG.  2   ; 
         FIG.  11    is a circuit diagram illustrating light source registers storing sensed currents of light source blocks in a sixth light source block column of  FIG.  2   ; 
         FIG.  12    is a block diagram illustrating a compensation controller compensating luminance difference of the light source apparatus of  FIG.  2   ; 
         FIG.  13    is a conceptual diagram illustrating a configuration of a compensated light source data signal generated by the compensation controller of  FIG.  12   ; 
         FIG.  14    is a timing diagram illustrating input signals to drive the light source apparatus of  FIG.  2   ; 
         FIG.  15    is a block diagram illustrating an exemplary embodiment of a compensation controller compensating luminance difference of a light source apparatus according to the invention; and 
         FIG.  16    is a circuit diagram illustrating an exemplary embodiment of a light source driver and a light source block according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the invention will be explained in detail with reference to the accompanying drawings. 
     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, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “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 exemplary 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 exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description 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 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” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     “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%, 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. 
     Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, 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. 
       FIG.  1    is a block diagram illustrating an exemplary embodiment of a display apparatus according to the invention. 
     Referring to  FIG.  1   , the display apparatus includes a display panel  100  and a display panel driver. The display panel driver includes a driving controller  200 , a gate driver  300 , a gamma reference voltage generator  400  and a data driver  500 . The display apparatus may further include a light source apparatus BLU providing light to the display panel  100  and a light source driver  600  driving the light source apparatus BLU. 
     The display panel  100  includes a plurality of gate lines GL, a plurality of data lines DL and a plurality of pixels electrically connected to the gate lines GL and the data lines DL. The gate lines GL may extend in a first direction D 1  and the data lines DL may extend in a second direction D 2  crossing the first direction D 1 . 
     The display panel  100  may include a first base substrate on which the gate lines GL, the data lines DL, the pixels and switching elements are disposed, a second base substrate facing the first base substrate and including a common electrode and a liquid crystal layer disposed between the first base substrate and the second base substrate. 
     The driving controller  200  may receive the input image data IMG and an input control signal CONT from an external apparatus. In an exemplary embodiment, the input image data IMG may include red image data, green image data and blue image data, for example. In an exemplary embodiment, the input image data IMG may include white image data, for example. In an exemplary embodiment, the input image data IMG may include magenta image data, cyan image data and yellow image data, for example. However, the invention is not limited thereto, and in another exemplary embodiment, the input image data IMG may include various other color data. The input control signal CONT may include a master clock signal and a data enable signal. The input control signal CONT may further include a vertical synchronizing signal and a horizontal synchronizing signal. 
     The driving controller  200  generates a first control signal CONT 1 , a second control signal CONT 2 , a third control signal CONT 3  and a data signal DATA based on the input image data IMG and the input control signal CONT. 
     The driving controller  200  generates the first control signal CONT 1  for controlling an operation of the gate driver  300  based on the input control signal CONT, and outputs the first control signal CONT 1  to the gate driver  300 . The first control signal CONT 1  may include a vertical start signal and a gate clock signal. 
     The driving controller  200  generates the second control signal CONT 2  for controlling an operation of the data driver  500  based on the input control signal CONT, and outputs the second control signal CONT 2  to the data driver  500 . The second control signal CONT 2  may include a horizontal start signal and a load signal. 
     The driving controller  200  generates the data signal DATA based on the input image data IMG. The driving controller  200  outputs the data signal DATA to the data driver  500 . 
     The driving controller  200  generates the third control signal CONT 3  for controlling an operation of the gamma reference voltage generator  400  based on the input control signal CONT, and outputs the third control signal CONT 3  to the gamma reference voltage generator  400 . 
     The driving controller  200  may output a light source gate signal LGS, a light source data signal LDS and a light source emission signal LEM to the light source driver  600 . 
     In addition, the driving controller  200  generates a dimming signal DIMM to control a dimming operation of the light source apparatus BLU based on the input image data IMG. The driving controller  200  outputs the dimming signal to the light source driver  600 . The dimming signal may be a local dimming signal representing a degree of dimming of each light source blocks of the light source apparatus BLU. In an exemplary embodiment, the light source data signal LDS may include the dimming signal, for example. 
     The gate driver  300  generates gate signals driving the gate lines GL in response to the first control signal CONT 1  received from the driving controller  200 . The gate driver  300  may output the gate signals to the gate lines GL. 
     The gamma reference voltage generator  400  generates a gamma reference voltage VGREF in response to the third control signal CONT 3  received from the driving controller  200 . The gamma reference voltage generator  400  provides the gamma reference voltage VGREF to the data driver  500 . The gamma reference voltage VGREF has a value corresponding to a level of the data signal DATA. 
     In an exemplary embodiment, the gamma reference voltage generator  400  may be disposed in the driving controller  200 , or in the data driver  500 . 
     The data driver  500  receives the second control signal CONT 2  and the data signal DATA from the driving controller  200 , and receives the gamma reference voltages VGREF from the gamma reference voltage generator  400 . The data driver  500  converts the data signal DATA into data voltages having an analog type using the gamma reference voltages VGREF. The data driver  500  outputs the data voltages to the data lines DL. 
     The light source driver  600  may receive the light source gate signal LGS, the light source data signal LDS and the light source emission signal LEM from the driving controller  200 . The light source driver  600  may drive the light source apparatus BLU based on the light source gate signal LGS, the light source data signal LDS and the light source emission signal LEM. 
       FIG.  2    is a conceptual diagram illustrating the light source apparatus BLU of  FIG.  1   .  FIG.  3    is a circuit diagram illustrating a light source block LB of  FIG.  2   . 
     Referring to  FIGS.  1  to  3   , the light source apparatus BLU includes a plurality of light source blocks LB 1  to LB 36 . The light source apparatus BLU further includes a plurality of light source gate lines LGL 1  to LGL 6  extending in the first direction D 1  and a plurality of light source data lines LDL 1  to LDL 6 , a plurality of light source emission lines LEML and a plurality of feedback lines FB 1  to FB 6  extending in the second direction D 2  crossing the first direction D 1 . The light source emission lines LEML may be commonly connected. 
     At least one of the light source blocks LB 1  to LB 36  is connected to the light source gate line, the light source data line, the light source emission line and the feedback line. In an exemplary embodiment, each of the light source blocks LB 1  to LB 36  may be connected to the light source gate line, the light source data line, the light source emission line and the feedback line, for example. When the light source gate signal is applied to the light source gate line, a switching element in each of the light source blocks LB 1  to LB 36  is turned on so that the light source data signal is charged to the light source block LB 1  to LB 36 . During the light source emission signal is applied, the light source blocks LB 1  to LB 36  emit light in a luminance corresponding to the light source data signal. In an exemplary embodiment, the light source data signal is divided into a plurality of bits and emission durations of the bits may be variously set so that the light source blocks LB 1  to LB 36  may be driven in a digital driving method, for example. 
     The light source block includes a light emitting element. In an exemplary embodiment, the light source block may include a single light emitting element, for example. In an alternative exemplary embodiment, the light source block may include a plurality of light emitting elements. The light source block may include a light emitting element string including a plurality of light emitting elements connected to each other in series. In an exemplary embodiment, the light emitting element may be a light emitting diode (“LED”), for example. 
     Although the light source apparatus includes the thirty six light source blocks LB 1  to LB 36  forming a six by six matrix in the illustrated exemplary embodiment, the invention is not limited thereto. In an alternative exemplary embodiment, the light source apparatus may include light source blocks less than thirty six or more than thirty six. 
     The feedback line may be commonly connected to the light source blocks disposed in the light source block column. A first feedback line FB 1  may be connected to a first light source block LB 1 , a seventh light source block LB 7 , a thirteenth light source block LB 13 , a nineteenth light source block LB 19 , a twenty fifth light source block LB 25  and a thirty first light source block LB 31  disposed in a first light source block column. A second feedback line FB 2  may be connected to a second light source block LB 2 , an eighth light source block LB 8 , a fourteenth light source block LB 14 , a twentieth light source block LB 20 , a twenty sixth light source block LB 26  and a thirty second light source block LB 32  disposed in a second light source block column. A third feedback line FB 3  may be connected to a third light source block LB 3 , a ninth light source block LB 9 , a fifteenth light source block LB 15 , a twenty first light source block LB 21 , a twenty seventh light source block LB 27  and a thirty third light source block LB 33  disposed in a third light source block column. A fourth feedback line FB 4  may be connected to a fourth light source block LB 4 , a tenth light source block LB 10 , a sixteenth light source block LB 16 , a twenty second light source block LB 22 , a twenty eighth light source block LB 28  and a thirty fourth light source block LB 34  disposed in a fourth light source block column. A fifth feedback line FB 5  may be connected to a fifth light source block LB 5 , an eleventh light source block LB 11 , a seventeenth light source block LB 17 , a twenty third light source block LB 23 , a twenty ninth light source block LB 29  and a thirty fifth light source block LB 35  disposed in a fifth light source block column. A sixth feedback line FB 6  may be connected to a sixth light source block LB 6 , a twelfth light source block LB 12 , an eighteenth light source block LB 18 , a twenty fourth light source block LB 24 , a thirtieth light source block LB 30  and a thirty sixth light source block LB 36  disposed in a sixth light source block column. 
     A first end portion of the feedback line may be connected to the light source blocks in the light source block column and a second end portion of the feedback line may be connected to a feedback resistor. In an exemplary embodiment, a first end portion of the first feedback line FB 1  may be connected to the light source blocks LB 1 , LB 7 , LB 13 , LB 19 , LB 25  and LB 31  in the first light source block column and a second end portion of the first feedback line FB 1  may be connected to a first feedback resistor R 1 , for example. In the same way, the second feedback line FB 2  may be connected to a second feedback resistor R 2 , the third feedback line FB 3  may be connected to a third feedback resistor R 3 , the fourth feedback line FB 4  may be connected to a fourth feedback resistor R 4 , the fifth feedback line FB 5  may be connected to a fifth feedback resistor R 5  and the sixth feedback line FB 6  may be connected to a sixth feedback resistor R 6 . 
     The feedback resistors R 1  to R 6  may be connected between a power voltage applying terminal VLED of the light source block and the second end portion of the feedback lines FB 1  to FB 6 . 
     The light source block LB may include a light emitting element LED, a first switching element T 1 , a second switching element T 2  and a third switching element T 3 . The first switching element T 1  includes a control electrode connected to the light source gate line LGL, an input electrode connected to the light source data line LDL and an output electrode connected to a control electrode of the second switching element T 2 . The second switching element T 2  includes a control electrode connected to the output electrode of the first switching element T 1 , an input electrode connected to an output electrode of the third switching element T 3  and an output electrode connected to a ground. The third switching element T 3  includes a control electrode connected to the light source emission line LEML, an input electrode connected to the light emitting element LED and the output electrode connected to the input electrode of the second switching element T 2 . Although the light emitting element LED is a single light emitting diode in  FIG.  3   , the light emitting element LED may be a light emitting diode string including a plurality of light emitting diodes. The light source block LB may further include a capacitor C connected between a control terminal of the second switching element T 2  and the ground. 
     In the illustrated exemplary embodiment, the plurality of feedback lines FB 1  to FB 6  may extend in a direction parallel to the light source data lines LDL 1  to LDL 6  in an area corresponding to the display area of the display panel  100 . 
     In addition, the plurality of light source emission lines (a plurality of branches of LEML) may extend in a direction parallel to the light source data lines LDL 1  to LDL 6  in the area corresponding to the display area of the display panel  100 . 
       FIG.  4    is a timing diagram illustrating a method of sensing a current of the light source block LB of  FIG.  2   .  FIG.  5    is a flowchart diagram illustrating a method of compensating luminance difference of the light source apparatus BLU of  FIG.  2   .  FIG.  6    is a circuit diagram illustrating light source registers LREG 1 , LREG 7 , LREG 13 , LREG 19 , LREG 25  and LREG 31  storing sensed currents of light source blocks LB 1 , LB 7 , LB 13 , LB 19 , LB 25  and LB 31  in the first light source block column of  FIG.  2   .  FIG.  7    is a circuit diagram illustrating light source registers LREG 2 , LREG 8 , LREG 14 , LREG 20 , LREG 26  and LREG 32  storing sensed currents of light source blocks LB 2 , LB 8 , LB 14 , LB 20 , LB 26  and LB 32  in the second light source block column of  FIG.  2   .  FIG.  8    is a circuit diagram illustrating light source registers LREG 3 , LREG 9 , LREG 15 , LREG 21 , LREG 27  and LREG 33  storing sensed currents of light source blocks LB 3 , LB 9 , LB 15 , LB 21 , LB 27  and LB 33  in the third light source block column of  FIG.  2   .  FIG.  9    is a circuit diagram illustrating light source registers LREG 4 , LREG 10 , LREG 16 , LREG 22 , LREG 28  and LREG 34  storing sensed currents of light source blocks LB 4 , LB 10 , LB 16 , LB 22 , LB 28  and LB 34  in the fourth light source block column of  FIG.  2   .  FIG.  10    is a circuit diagram illustrating light source registers LREG 5 , LREG 11 , LREG 17 , LREG 23 , LREG 29  and LREG 35  storing sensed currents of light source blocks LB 5 , LB 11 , LB 17 , LB 23 , LB 29  and LB 35  in the fifth light source block column of  FIG.  2   .  FIG.  11    is a circuit diagram illustrating light source registers LREG 6 , LREG 12 , LREG 18 , LREG 24 , LREG 30  and LREG 36  storing sensed currents of light source blocks LB 6 , LB 12 , LB 18 , LB 24 , LB 30  and LB 36  in the sixth light source block column of  FIG.  2   .  FIG.  12    is a block diagram illustrating a compensation controller (e.g., LED current compensation controller)  220  compensating luminance difference of the light source apparatus BLU of  FIG.  2   . 
     Referring to  FIGS.  1  to  12   , the display apparatus may include a light source compensator including a plurality of light source registers LREG 1  to LREG 36  and the compensation controller  220 . The light source registers LREG 1  to LREG 36  stores the sensed currents of the light source blocks LB 1  to LB 36  which are fed back through the feedback lines FB 1  to FB 6 . In an exemplary embodiment, the number of the light source registers may be same as the number of the light source blocks, for example. 
     In the illustrated exemplary embodiment, the light source compensator may be disposed in the driving controller  200 . 
     When the light source apparatus BLU includes light source blocks forming two by two matrix, the light source compensator may include a first light source register storing a first sensed current in response to a first light source gate signal through a first feedback line, a second light source register storing a second sensed current in response to the first light source gate signal through a second feedback line, a third light source register storing a third sensed current in response to a second light source gate signal through the first feedback line and a fourth light source register storing a fourth sensed current in response to the second light source gate signal through the second feedback line. 
     When the light source apparatus BLU includes light source blocks forming a two by two matrix, the light source compensator may further include a first error amplifier and a first analog to digital converter (“ADC”). The first error amplifier may compare the signal transmitted through the first feedback line to a reference voltage. The first ADC may be connected to the first error amplifier. Herein, the first ADC may be connected to the first light source register and the third light source register. In addition, when the light source apparatus BLU includes light source blocks forming the two by two matrix, the light source compensator may further include a second error amplifier and a second ADC. The second error amplifier may compare the signal transmitted through the second feedback line to the reference voltage. The second ADC may be connected to the second error amplifier. Herein, the second ADC may be connected to the second light source register and the fourth light source register. 
     When the light source apparatus BLU includes light source blocks LB 1  to LB 36  forming a six by six matrix as shown in  FIG.  2   , the light source compensator may include thirty six light source registers and six error amplifiers and six ADCs. 
     To compensate the luminance difference of the light source apparatus BLU, the plurality of light source gate signals LGS 1  to LGS 6  may be applied to the plurality of light source gate lines LGL 1  to LGL 6 , a plurality of test light source data signals may be applied to the plurality of light source data lines LDL 1  to LDL 6  and the light source emission signal LEM may be applied to the plurality of light source emission lines LEML. The currents flowing through the light source blocks LB 1  to LB 36  may be sensed through the feedback lines FB 1  to FB 6 . In an exemplary embodiment, the test light source data signals may correspond to a maximum luminance, for example. In an alternative exemplary embodiment, the test light source data signals may correspond to a predetermined luminance. 
     The compensated light source data signal is generated using the currents sensed through the feedback lines FB 1  to FB 6  so that the luminance difference between the light source blocks LB 1  to LB 36  of the light source apparatus BLU may be compensated. 
     As shown in  FIG.  4   , the currents of the first to sixth light source blocks LB 1  to LB 6  are sensed through the first to sixth feedback lines FB 1  to FB 6  in a duration when the first light source gate signal LGS 1  has an active level. The currents of the seventh to twelfth light source blocks LB 7  to LB 12  are sensed through the first to sixth feedback lines FB 1  to FB 6  in a duration when the second light source gate signal LGS 2  has an active level. The currents of the thirteenth to eighteenth light source blocks LB 13  to LB 18  are sensed through the first to sixth feedback lines FB 1  to FB 6  in a duration when the third light source gate signal LGS 3  has an active level. The currents of the nineteenth to twenty fourth light source blocks LB 19  to LB 24  are sensed through the first to sixth feedback lines FB 1  to FB 6  in a duration when the fourth light source gate signal LGS 4  has an active level. The currents of the twenty fifth to thirtieth light source blocks LB 25  to LB 30  are sensed through the first to sixth feedback lines FB 1  to FB 6  in a duration when the fifth light source gate signal LGS 5  has an active level. The currents of the thirty first to thirty sixth light source blocks LB 31  to LB 36  are sensed through the first to sixth feedback lines FB 1  to FB 6  in a duration when the sixth light source gate signal LGS 6  has an active level. 
     Herein, the method of compensating the luminance difference of the light source apparatus is explained step by step referring to  FIG.  5   . After the display apparatus is turned on (operation S10), a current calibration operation of the light source apparatus BLU is enabled (operation S20). 
     As shown in  FIG.  4   , the currents of the light source blocks disposed in the first to sixth light source block rows are sensed by sequentially activating the first to sixth light source gate signals LGS 1  to LGS 6  (operation S30 to operation S80). 
     The sensed currents may be stored in the light source registers LREG 1  to LREG 36 . The compensation controller  220  may generate the compensated light source data signal using the sensed currents which are stored in the light source registers LREG 1  to LREG 36  (operation S90). 
     After the compensated light source data signal is generated, the current calibration operation of the light source apparatus BLU is disabled (operation S100). 
     After the current calibration operation of the light source apparatus BLU is disabled, the compensated light source data signal is outputted to the light source apparatus BLU (operation S110). 
     As shown in  FIG.  6   , the light source compensator includes a first error amplifier EA 1  and a first ADC ADC 1 . The first error amplifier EA 1  compares a signal transmitted through the first feedback line FB 1  to a reference voltage VREF. The first ADC ADC 1  is connected to the first error amplifier EA 1 . The first ADC ADC 1  is connected to the first light source register LREG 1  and stores the sensed current of the first light source block LB 1  to the first light source register LREG 1  when the first gate signal LGS 1  has an active level. The first ADC ADC 1  is connected to the seventh light source register LREG 7  and stores the sensed current of the seventh light source block LB 7  to the seventh light source register LREG 7  when the second gate signal LGS 2  has an active level. The first ADC ADC 1  is connected to the thirteenth light source register LREG 13  and stores the sensed current of the thirteenth light source block LB 13  to the thirteenth light source register LREG 13  when the third gate signal LGS 3  has an active level. The first ADC ADC 1  is connected to the nineteenth light source register LREG 19  and stores the sensed current of the nineteenth light source block LB 19  to the nineteenth light source register LREG 19  when the fourth gate signal LGS 4  has an active level. The first ADC ADC 1  is connected to the twenty fifth light source register LREG 25  and stores the sensed current of the twenty fifth light source block LB 25  to the twenty fifth light source register LREG 25  when the fifth gate signal LGS 5  has an active level. The first ADC ADC 1  is connected to the thirty first light source register LREG 31  and stores the sensed current of the thirty first light source block LB 31  to the thirty first light source register LREG 31  when the sixth gate signal LGS 6  has an active level. 
     As shown in  FIG.  7   , the light source compensator includes a second error amplifier EA 2  and a second ADC ADC 2 . The second error amplifier EA 2  compares a signal transmitted through the second feedback line FB 2  to the reference voltage VREF. The second ADC ADC 2  is connected to the second error amplifier EA 2 . The second ADC ADC 2  is connected to the second light source register LREG 2  and stores the sensed current of the second light source block LB 2  to the second light source register LREG 2  when the first gate signal LGS 1  has the active level. The second ADC ADC 2  is connected to the eighth light source register LREG 8  and stores the sensed current of the eighth light source block LB 8  to the eighth light source register LREG 8  when the second gate signal LGS 2  has the active level. The second ADC ADC 2  is connected to the fourteenth light source register LREG 14  and stores the sensed current of the fourteenth light source block LB 14  to the fourteenth light source register LREG 14  when the third gate signal LGS 3  has the active level. The second ADC ADC 2  is connected to the twentieth light source register LREG 20  and stores the sensed current of the twentieth light source block LB 20  to the twentieth light source register LREG 20  when the fourth gate signal LGS 4  has the active level. The second ADC ADC 2  is connected to the twenty sixth light source register LREG 26  and stores the sensed current of the twenty sixth light source block LB 26  to the twenty sixth light source register LREG 26  when the fifth gate signal LGS 5  has the active level. The second ADC ADC 2  is connected to the thirty second light source register LREG 32  and stores the sensed current of the thirty second light source block LB 32  to the thirty second light source register LREG 32  when the sixth gate signal LGS 6  has the active level. 
     As shown in  FIG.  8   , the light source compensator includes a third error amplifier EA 3  and a third ADC ADC 3 . The third error amplifier EA 3  compares a signal transmitted through the third feedback line FB 3  to the reference voltage VREF. The third ADC ADC 3  is connected to the third error amplifier EA 3 . The third ADC ADC 3  is connected to six of the light source registers and stores the corresponding sensed current of light source blocks to the six light source registers as explained referring to  FIGS.  6  and  7   . 
     As shown in  FIG.  9   , the light source compensator includes a fourth error amplifier EA 4  and a fourth ADC ADC 4 . The fourth error amplifier EA 4  compares a signal transmitted through the fourth feedback line FB 4  to the reference voltage VREF. The fourth ADC ADC 4  is connected to the fourth error amplifier EA 4 . The fourth ADC ADC 4  is connected to six of the light source registers and stores the corresponding sensed current of light source blocks to the six light source registers as explained referring to  FIGS.  6  and  7   . 
     As shown in  FIG.  10   , the light source compensator includes a fifth error amplifier EA 5  and a fifth ADC ADC 5 . The fifth error amplifier EA 5  compares a signal transmitted through the fifth feedback line FB 5  to the reference voltage VREF. The fifth ADC ADC 5  is connected to the fifth error amplifier EA 5 . The fifth ADC ADC 5  is connected to six of the light source registers and stores the corresponding sensed current of light source blocks to the six light source registers as explained referring to  FIGS.  6  and  7   . 
     As shown in  FIG.  11   , the light source compensator includes a sixth error amplifier EA 6  and a sixth ADC ADC 6 . The sixth error amplifier EA 6  compares a signal transmitted through the sixth feedback line FB 6  to the reference voltage VREF. The sixth ADC ADC 6  is connected to the sixth error amplifier EA 6 . The sixth ADC ADC 6  is connected to six of the light source registers and stores the corresponding sensed current of light source blocks to the six light source registers as explained referring to  FIGS.  6  and  7   . 
       FIG.  13    is a conceptual diagram illustrating a configuration of a compensated light source data signal generated by the compensation controller  220  of  FIG.  12   .  FIG.  14    is a timing diagram illustrating input signals to drive the light source apparatus BLU of  FIG.  2   . 
     Referring to  FIGS.  1  to  14   , the compensated light source data signal may include luminance data bits representing a target luminance according to a local dimming method and compensation data bit for compensating the luminance difference between the light source blocks LB. 
     Although the luminance data bits are ten bits and the compensation data bits are four bits in  FIG.  13   , the invention is not limited to the number of the luminance data bits and the number of the compensation data bits. In an exemplary embodiment, when the luminance difference between the light source blocks LB are relatively great, the number of the compensation bits may be set to be great, for example. In contrast, when the luminance difference between the light source blocks LB are relatively little, the number of the compensation bits may be set to be little. 
     In an exemplary embodiment, the luminance data bits have a value of “0000000000” for a minimum luminance (e.g. 0 grayscale) and a value of “1111111111” for a maximum luminance (e.g. 1023 grayscale), for example. 
     In an exemplary embodiment, the compensation data bits have a value of “0000” for a minimum compensation value (e.g. 0 grayscale) and “1111” for a maximum compensation value (e.g. 15 grayscale), for example. 
     In  FIG.  14   , a compensation period corresponding to the compensation data bits may be disposed in an early period of the compensated light source data signal and a luminance period corresponding to the luminance data bits may be disposed in a late period of the compensated light source data signal. 
     When a light source vertical start signal LSTV has an active level (e.g. a high level), a frame starts. During a non-emission duration, the light source emission signal LEM has an inactive level (e.g. a low level). During the non-emission duration, the compensated light source data signal is written to the light source block. During an emission duration, the light source emission signal LEM has an active level (e.g. a high level). During the emission duration, the light source block provides light to the display panel  100  based on the compensated light source data signal which is written to the light source block. 
     The compensation period corresponds to a length for four bits. Although the luminance period corresponds to a length for ten bits, the luminance period is illustrated corresponding to a length for five bits in  FIG.  14    for convenience of explanation. 
     In an exemplary embodiment, when a light source block represents relatively maximum luminance in the light source apparatus for a target luminance, the light source block may be compensated by the minimum compensation value (e.g. 0000), for example. In contrast, when a light source block represents relatively minimum luminance in the light source apparatus for the target luminance, the light source block may be compensated by the maximum compensation value (e.g. 1111). Thus, the luminance difference between the light source blocks may be compensated by the compensation data bits. 
     The compensation value may be varied according to the target luminance of the luminance data bits. In an exemplary embodiment, when the target luminance of the luminance data bits is great, the compensation value may be great, for example. In an exemplary embodiment, when the target luminance of the luminance data bits is little, the compensation value may be little, for example. 
     According to the illustrated exemplary embodiment, the light source apparatus BLU may be driven using the active matrix method so that the manufacturing cost and the complexity of the light source apparatus BLU may be reduced. The light source apparatus BLU includes the light source blocks LB 1  to LB 36  connected to the light source gate lines LGL 1  to LGL 6 , the light source data lines LDL 1  to LDL 6 , the light source emission lines LEML and the feedback lines FB 1  to FB 6 , and the currents of the light source blocks LB 1  to LB 36  are fed back so that the luminance difference between the light source blocks LB 1  to LB 36  may be compensated. 
       FIG.  15    is a block diagram illustrating a compensation controller compensating luminance difference of a light source apparatus according to an exemplary embodiment of the invention. 
     The light source apparatus and the display apparatus according to the illustrated exemplary embodiment is substantially the same as the light source apparatus and the display apparatus of the previous exemplary embodiment explained referring to  FIGS.  1  to  14    except that the compensation controller is disposed in the light source driver. Thus, the same reference numerals will be used to refer to the same or like parts as those described in the previous exemplary embodiment of  FIGS.  1  to  14    and any repetitive explanation concerning the above elements will be omitted. 
     Referring to  FIGS.  1  to  11  and  13  to  15   , the display apparatus includes a display panel  100  and a display panel driver. The display panel driver includes a driving controller  200 , a gate driver  300 , a gamma reference voltage generator  400  and a data driver  500 . The display apparatus may further include a light source apparatus BLU providing light to the display panel  100  and a light source driver  600  driving the light source apparatus BLU. 
     The display apparatus may include a light source compensator including a plurality of light source registers LREG 1  to LREG 36  and a compensation controller (e.g., LED current compensation controller)  620 . The light source registers LREG 1  to LREG 36  stores the sensed currents of the light source blocks LB 1  to LB 36  which are fed back through the feedback lines FB 1  to FB 6 . In an exemplary embodiment, the number of the light source registers may be same as the number of the light source blocks, for example. 
     In the illustrated exemplary embodiment, the light source compensator may be disposed in the light source driver  600 . In the illustrated exemplary embodiment, the feedback signal FB may be transmitted to the light source driver  600  and may not be transmitted to the driving controller  200 . 
     According to the illustrated exemplary embodiment, the light source apparatus BLU may be driven using the active matrix method so that the manufacturing cost and the complexity of the light source apparatus BLU may be reduced. The light source apparatus BLU includes the light source blocks LB 1  to LB 36  connected to the light source gate lines LGL 1  to LGL 6 , the light source data lines LDL 1  to LDL 6 , the light source emission lines LEML and the feedback lines FB 1  to FB 6 , and the currents of the light source blocks LB 1  to LB 36  are fed back so that the luminance difference between the light source blocks LB 1  to LB 36  may be compensated. 
       FIG.  16    is a circuit diagram illustrating a light source driver and a light source block according to an exemplary embodiment of the invention. 
     The light source apparatus and the display apparatus according to the illustrated exemplary embodiment is substantially the same as the light source apparatus and the display apparatus of the previous exemplary embodiment explained referring to  FIGS.  1  to  14    except for the structure of the light source block. Thus, the same reference numerals will be used to refer to the same or like parts as those described in the previous exemplary embodiment of  FIGS.  1  to  14    and any repetitive explanation concerning the above elements will be omitted. 
     Referring to  FIGS.  1 ,  2 ,  4  to  14  and  16   , the display apparatus includes a display panel  100  and a display panel driver. The display panel driver includes a driving controller  200 , a gate driver  300 , a gamma reference voltage generator  400  and a data driver  500 . The display apparatus may further include a light source apparatus BLU providing light to the display panel  100  and a light source driver  600  driving the light source apparatus BLU. 
     In the illustrated exemplary embodiment, the light source block LB includes a light emitting element LED. The light source circuit  640  of the light source driver  600  may include a first switching element T 1 , a second switching element T 2  and a third switching element T 3 . The first switching element T 1  includes a control electrode connected to the light source gate line LGL (refer to  FIG.  2   ), an input electrode connected to the light source data line LDL and an output electrode connected to a control electrode of the second switching element T 2 . The second switching element T 2  includes a control electrode connected to the output electrode of the first switching element T 1 , an input electrode connected to an output electrode of the third switching element T 3  and an output electrode connected to a ground. The third switching element T 3  includes a control electrode connected to the light source emission line LEML, an input electrode connected to the light emitting element LED and the output electrode connected to the input electrode of the second switching element T 2 . The light source circuit  640  may further include a capacitor C connected between a control terminal of the second switching element T 2  and the ground. 
     According to the illustrated exemplary embodiment, the light source apparatus BLU may be driven using the active matrix method so that the manufacturing cost and the complexity of the light source apparatus BLU may be reduced. The light source apparatus BLU includes the light source blocks LB 1  to LB 36  connected to the light source gate lines LGL 1  to LGL 6 , the light source data lines LDL 1  to LDL 6 , the light source emission lines LEML and the feedback lines FB 1  to FB 6  and the currents of the light source blocks LB 1  to LB 36  are fed back so that the luminance difference between the light source blocks LB 1  to LB 36  may be compensated. 
     According to the invention as explained above, the manufacturing cost and the complexity of the light source apparatus BLU may be reduced and the luminance difference between the light source blocks may be effectively compensated using the active matrix method. 
     The foregoing is illustrative of the invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of the invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of the invention. Accordingly, all such modifications are intended to be included within the scope of the invention as defined in the claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Therefore, it is to be understood that the foregoing is illustrative of the invention and is not to be construed as limited to the specific exemplary embodiments disclosed, and that modifications to the disclosed exemplary embodiments, as well as other exemplary embodiments, are intended to be included within the scope of the appended claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.