Patent Publication Number: US-10762835-B2

Title: Display device and driving method thereof

Description:
This application claims the benefit of Korean Patent Application No. 10-2017-0175987, filed Dec. 20, 2017, which is hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a display device and a driving method thereof. 
     2. Description of Related Art 
     As the information technology is developed, the market for display devices as connection mediums between users and information has increased. Accordingly, the use of an organic light emitting display device is increasing. 
     An organic light emitting display device includes a display panel including a plurality of sub-pixels, a driver outputting a driving signal for driving the display panel, and a power supply unit generating power to be supplied to the display panel and the driver. The driver includes a scan driver supplying a scan signal (or a gate signal) to the display panel, a data driver for supplying a data signal to the display panel, and a data driver supplying a data signal to the display panel. 
     An organic light emitting display device includes a driving thin film transistor (TFT) adjusting a driving current flowing in a light emitting diode included in a subpixel and a plurality of switching TFTs. Elements included in a pixel must be designed for controlling a driving current flowing in a light emitting diode included in a sub pixel. The elements included in all pixels must be designed to be the same, but characteristics such as performance and the life of actual elements, and the like, are uneven according to process variations, driving time, and driving environments, and the like. 
     Such non-uniformity causes a compensation error when sensing/non-sensing compensation is performed. Therefore, it is required to do research into a compensation method for reducing the problem that the life of a display panel is shortened and a difference in degradation between subpixels in consideration of non-uniform performance and life distribution of the elements included in the subpixels. 
     SUMMARY 
     Accordingly, embodiments of the present disclosure are directed to a display device and a driving method thereof that substantially obviate one or more of the problems due to limitations and disadvantages of the related art. 
     An aspect of the present disclosure is to perform compensation such that all the elements included in a display panel have the same life by reflecting life characteristics of the elements, whereby a difference in degradation between neighboring pixels is reduced and the entire region of the display panel is degraded at a substantially uniform rate. 
     Additional features and aspects will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the inventive concepts provided herein. Other features and aspects of the inventive concepts may be realized and attained by the structure particularly pointed out in the written description, or derivable therefrom, and the claims hereof as well as the appended drawings. 
     To achieve these and other aspects of the inventive concepts, as embodied and broadly described, a display device comprises: a display panel including subpixels displaying an image; and a life controller controlling at least any one of a compensation rate and a delay rate of the subpixels on the basis of usage data obtained by calculating usage of the display panel and life data of the subpixels. 
     The life controller may increase the delay rate if the usage data is relatively large and decrease the delay rate if the usage data is relatively small. 
     The life controller may include: a usage calculation unit calculating usage data of the display panel; a life reference unit storing positions and life of the subpixels; and a rate matching unit comparing the usage data with data of the life reference unit and controlling the compensation rate and the delay rate such that the life of the subpixels is reduced at the same rate. 
     The usage calculation unit may include at least one of a timer, a data accumulation calculation unit, a per-position accumulation calculation unit, and per-time accumulation calculation unit for calculation of usage of the display panel. 
     The rate matching unit may control the compensation rate and the delay rate by multiplying a constant “α” to usage data “I” calculated by the usage calculation unit, and the constant a may be calculated by equation 1 below.
 
α=( t   life,ref /τ) n   /I    [Equation 1]
 
T life =τ·I −n, , I −n : usage equation, τ: life Ref.
 
     Here, t life  indicates time required for luminance (or brightness) to decrease, and the life Ref is set to a constant obtained by sensing the life of an actual element. 
     The rate matching unit may compare the usage data with data of the life reference unit and control the compensation rate and the delay rate such that the life of the subpixels is reduced at the same rate, which may be expressed by Equation 3 below.
 
α( x, y, z,  . . . ) * L ( x, y, z  . . . )=L after    [Equation 3]
     x: panel order (example)   y: per-position y coordinate (example)   z: per-position x coordinate (example)   

     
       
         
           
             
               
                 L 
                 after 
               
               
                 L 
                 ( 
                 
                   x 
                   , 
                   y 
                   , 
                   z 
                   , 
                   … 
                 
                 ⁢ 
                 
                     
                 
                 ) 
               
             
             = 
             
               α 
               ( 
               
                 x 
                 , 
                 y 
                 , 
                 z 
                 , 
                 … 
               
               ⁢ 
               
                   
               
               ) 
             
           
         
       
     
     Here, L indicates a rate. 
     The display device may further include: a compensation unit performing compensation such that target luminance is obtained in the subpixels according to sensing values for the subpixels, and outputting a compensation result. 
     The display device may further include: a delay unit performing degradation delay such that a degradation generated in the subpixels is delayed according to characteristics of an image displayed on the display panel, and outputting a delay result. 
     In another aspect, a method for driving a display device comprises: storing life data of subpixels of a display panel together with corresponding position; calculating usage of the display panel when an image is displayed on the display unit; and controlling at least any one of a compensation rate and a delay rate of the sub-pixels on the basis of the usage data and life data of the sub-pixels. 
     The controlling of at least any one of a compensation rate and a delay rate of the sub-pixels on the basis of the usage data and life data of the sub-pixels may include increasing the delay rate if the usage data is relatively large and decreasing the delay rate if the usage data is relatively small. 
     In the controlling of at least any one of a compensation rate and a delay rate of the sub-pixels on the basis of the usage data and life data of the sub-pixels, the compensation rate and the delay rate may be controlled by multiplying a constant “α” to the usage data “I”, wherein the constant a may be calculated by equation 1 below.
 
α=( t   life,ref /τ) n   /I    [Equation 1]
     T life =τ·I −n I −n : usage equation, τ: life Ref.   

     Here, t life  indicates time required for luminance to decrease, and the life Ref is set to a constant obtained by sensing the life of an actual element. 
     In the controlling of at least any one of a compensation rate and a delay rate of the sub-pixels on the basis of the usage data and life data of the sub-pixels, the usage data may be compared with data of the life reference unit and the compensation rate and the delay rate may be controlled such that the life of the subpixels is reduced at the same rate, which may be expressed by Equation 3 below.
 
α( x, y, z,  . . . ) * L ( x, y, z  . . . )= L   after    [Equation 3]
     x: panel order (example)   y: per-position y coordinate (example)   z: per-position x coordinate (example)   

     
       
         
           
             
               
                 L 
                 after 
               
               
                 L 
                 ( 
                 
                   x 
                   , 
                   y 
                   , 
                   z 
                   , 
                   … 
                 
                 ⁢ 
                 
                     
                 
                 ) 
               
             
             = 
             
               α 
               ( 
               
                 x 
                 , 
                 y 
                 , 
                 z 
                 , 
                 … 
               
               ⁢ 
               
                   
               
               ) 
             
           
         
       
     
     Here, L indicates a rate. 
     Further, since compensation is performed such that all the elements included in a display panel have the same life by reflecting life characteristics of the elements, the entire region of the display panel may be degraded substantially at a uniform rate. 
     Also, since a rate of a delay/compensation algorithm is controlled according to a difference in life between regions of the display panel, an error of the delay/compensation algorithm may be reduced to optimize a compensation performance. 
     In addition, since the elements of the entire region of the display panel are controlled such that the life thereof come to an end substantially at the same time point, image quality may be uniformly maintained until the life of the display panel comes to an end. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the inventive concepts as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain various principles. In the drawings: 
         FIG. 1  is a schematic block diagram of a display device. 
         FIG. 2  is a schematic circuit diagram of a subpixel illustrated in  FIG. 1 . 
         FIG. 3  is a first exemplary view illustrating a configuration of a subpixel having a pixel compensation circuit unit and a device for driving the same. 
         FIG. 4  is a second exemplary view illustrating a configuration of a subpixel having a pixel compensation circuit unit and a device for driving the same. 
         FIG. 5  is a first exemplary view illustrating a configuration of a display device having a life controller according to an embodiment of the present invention. 
         FIG. 6  is a second exemplary view illustrating a configuration of a display device having a life controller according to an embodiment of the present invention. 
         FIG. 7  is a block diagram of a life controller according to an embodiment of the present invention. 
         FIG. 8  is a graph illustrating a life reference map according to an embodiment of the present invention. 
         FIGS. 9 and 10  are graphs illustrating an operation of a life controller according to the embodiment of the present invention. 
         FIG. 11  is a first exemplary view illustrating main circuits of a display device according to an embodiment of the present invention. 
         FIG. 12  is a second exemplary view illustrating main circuits of a display device according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, details for carrying out example embodiments of the present disclosure will be described with reference to the accompanying drawings. 
     A display device described hereinafter may be realized as a television, a video player, a personal computer (PC), a home theater, a smartphone, a virtual reality (VR) device, or the like. Hereinafter, an organic light emitting display device realized on the basis of an organic light emitting diode (OLED) (a light emitting device) will be described as an example of the display device. However, the organic light emitting display device described hereinafter may also be realized on the basis of an inorganic light emitting diode. 
     The display device described hereinafter has a display panel realized on the basis of a P-type transistor or an N-type transistor. In the case of the P-type transistor and the N-type transistor, positions of a source electrode and a drain electrode, except for a gate electrode, may be different according to types, and thus, in order not to limit them, the source electrode and the drain electrode will be referred to as a first electrode and a second electrode.  FIG. 1  is a schematic block diagram of a display device,  FIG. 2  is a schematic circuit diagram of a subpixel illustrated in  FIG. 1 ,  FIG. 3  is a first exemplary view illustrating a configuration of a subpixel having a pixel compensation circuit unit and a device for driving the same, and  FIG. 4  is a second exemplary view illustrating a configuration of a subpixel having a pixel compensation circuit unit and a device for driving the same. 
     As illustrated in  FIG. 1 , the display device includes an image processing unit  110 , a timing controller  120 , a data driver  140 , a scan driver  130 , a display panel  150 , and a power supply unit  180 . 
     The image processing unit  110  outputs driving signals for driving various devices together with image data supplied from the outside. The driving signals output from the image processing unit  110  may include a data enable signal, a vertical synchronization signal, a horizontal synchronization signal, and a clock signal, but these signals are omitted for convenience of description. 
     The timing controller  120  receives a driving signal, and the like, from the image processing unit  110  together with image data. The timing controller  120  outputs a gate timing control signal GDC for controlling an operation timing of the scan driver  130  and a data timing control signal DDC for controlling an operation timing of the data driver  140  on the basis of the driving signal. 
     The data driver  140  outputs a data signal in response to the data timing control signal DDC supplied from the timing controller  120 . The data driver  140  samples and latches a digital data signal DATA supplied from the timing controller  120  to convert the data signal into an analog voltage based on a gamma reference voltage. The data driver  140  outputs the data signal through data lines DL 1  to DLn. The data driver  140  may be formed as an integrated circuit (IC). 
     The scan driver  130  outputs a scan signal in response to the gate timing control signal GDC supplied from the timing controller  120 . The scan driver  130  outputs the scan signal through scan lines GL 1  to GLm. The scan driver  130  is formed as an integrated circuit (IC) or formed as a gate-in-panel type on the display panel  150 . 
     The power supply unit  180  outputs a high-potential voltage and a low-potential voltage. The high-potential voltage and low-potential voltage output from the power supply unit  180  are supplied to the display panel  150 . The high potential voltage is supplied to the display panel  150  through a first power line EVDD and the low potential voltage is supplied to the display panel  150  through a second power line EVSS. The voltage output from the power supply unit  180  may also be used in the data driver  140  or the scan driver  130 . 
     The display panel  150  displays an image corresponding to the data signal and the scan signal supplied from the data driver  140  and the scan driver  130  and power supplied from the power supply unit  180 . The display panel  150  includes sub-pixels SP which operate to display an image. 
     The subpixels SP may include a red subpixel, a green subpixel, and a blue subpixel or a white subpixel, a red subpixel, a green subpixel, and a blue subpixel. The subpixels SP may have one or more different emission areas according to emission characteristics. 
     As illustrated in  FIG. 2 , one subpixel SP includes a scan line GL 1 , a data line DL 1 , a switching transistor SW, and a pixel circuit unit PC. Driving characteristics of the sub-pixel SP vary according to configurations of the pixel circuit unit PC. The pixel circuit unit PC further includes a pixel compensation circuit unit for compensating degradation of an element. Hereinafter, the pixel compensation circuit configured as a single transistor will be described as an example. 
     As illustrated in  FIG. 3 , the sub-pixel SP includes a pixel circuit unit PC, a switching transistor SW, and a sensing transistor ST. The pixel circuit unit PC includes a driving transistor, a capacitor, an organic light emitting diode, and the like. 
     The switching transistor SW performs an operation for supplying a data signal to the inside of the pixel circuit unit PC. The switching transistor SW may be turned on/off in response to a scan signal supplied through a  1   a -th scan line GL 1   a.  The sensing transistor ST performs an operation for sensing the inside of the pixel circuit unit PC. The sensing transistor ST may be turned on/off in response to a sensing signal supplied through a  1   b -th scan line GL 1   b.    
     The data driver  140  is connected to the data line DL 1 . When the switching transistor SW is turned on, the data signal transferred through the data line DL 1  is transferred to the capacitor included in the pixel circuit unit PC of the subpixel SP. 
     An external compensation circuit unit  160  is connected to a sensing line SL 1 . When the sensing transistor ST is turned on, an element included in the pixel circuit unit PC of the sub-pixel SP is sensed. The external compensation circuit unit  160  may interwork with the sensing transistor ST serving as a pixel compensation circuit unit to sense and compensate for the characteristics of a driving transistor and the organic light emitting diode (OLED) included in the subpixel SP. 
     The external compensation circuit unit  160  obtains sensing data regarding the characteristics of the element included in at least one sub-pixel through the sensing line SL 1 . The external compensation circuit unit  160  generates compensation data so that the image data based on the sensing data may be compensated. The compensation data generated by the external compensation circuit unit  160  may be transmitted to the timing controller. However, in case where the external compensation circuit unit  160  is able to perform compensation by itself, the external compensation circuit unit  160  may be provided with the image data from the timing controller and perform compensation on the provided image data. 
     As illustrated in  FIG. 4 , the external compensation circuit unit  160  may be included in the data driver  140 . In this case, the data driver  140  has the external compensation circuit unit  160  connected to the sensing line SL 1  in addition to a signal output unit  143  connected to the data line DL 1 . Hereinafter, a connection relationship of the elements included in the sub-pixel SP will be described. 
     In the switching transistor SW, a gate electrode is connected to the  1   a -th scan line GL 1   a,  a first electrode is connected to the data line DL 1 , and a second electrode is connected to a gate electrode of the driving transistor DR. A first electrode of the driving transistor DR is connected to the first power line EVDD and a second electrode of the driving transistor DR is connected to an anode electrode of the organic light emitting diode OLED. In the capacitor Cst, a first electrode is connected to the gate electrode of the driving transistor DR and a second electrode is connected to the anode electrode of the OLED. 
     In the organic light emitting diode OLED, the anode electrode is connected to the second electrode of the driving transistor DR and a cathode electrode is connected to the second power line EVSS. In the sensing transistor ST, a gate electrode is connected to the  1   b -th scan line GL 1   b,  a first electrode is connected to the anode electrode of the organic light emitting diode OLED as a sensing node and the second electrode of the driving transistor DR, and a second electrode is connected to the sensing line SL 1 . Although the la-th scan line GL 1   a  and the  1   b -th scan line GL 1   b  are separated from each other by way of example, they may be integrated into one scan line. 
     Meanwhile,  FIG. 4  illustrates the subpixel SP having a 3T (transistor)  1 C (capacitor) structure including the switching transistor SW, the driving transistor DR, the capacitor Cst, the organic light emitting diode OLED, and the sensing transistor ST. The sub-pixel SP has been described as an example. However, the subpixel SP may be configured in various manners such as 3T2C, 4T2C, 5T1C, 6T2C, and the like, according to configurations of the pixel compensation circuit unit, and thus, the present invention is not limited thereto. 
     The display device described above adopts a compensation technique for compensating for a degradation applied to each element or delaying the degradation. However, a degradation delay/compensation algorithm applied to the organic light emitting display device does not consider the life of each element and the related art method displays data of desired luminance by applying a larger gain as the degradation progresses. Thus, in the related art method, since a larger gain is applied as the degradation progresses, the degradation is rather accelerated due to compensation, causing a phenomenon in which the life of the element is shortened. That is, time required for luminance to be reduced to 50% is rather shortened, relative to the case where compensation is not performed. 
     Thus, in example embodiments of the present invention, life dispersion information of elements is collected in advance at the time of manufacturing display devices and the delay/compensation algorithm application rate is controlled according to life dispersion of each element when the delay/compensation algorithm is applied. For example, although the same delay/compensation value is set, each of the elements generates different luminance if the life thereof is different. An element with the relatively short life is controlled to generate relatively low luminance compared to an element with the long life. Accordingly, the difference in life between the element with the short life and the element with the long life may be reduced. 
       FIG. 5  is a first exemplary view illustrating main circuits of a display device according to an embodiment of the present invention,  FIG. 6  is a second exemplary view illustrating main circuits of a display device according to an embodiment of the present invention, and  FIG. 7  is a block diagram specifically illustrating a life controller illustrated in  FIGS. 5 and 6 . 
     As illustrated in  FIG. 5 , the display device according to a first embodiment of the present invention includes the image processing unit  110 , the external compensation circuit unit  160 , a life controller  170 , and the timing controller  120 . 
     As illustrated in  FIG. 6 , the display device according to a second embodiment of the present invention includes the image processing unit  110 , the external compensation circuit unit  160 , the life controller  170 , and the timing controller  120 . The life controller  170  is included in the timing controller  120 . 
     The life controller  170  illustrated in  FIGS. 5 and 6  controls the life of the elements included in the display panel to come to an end at the substantially same time. The life controller  170  may estimate a usage according to input image data transferred from the image processing unit  110  and calculate a rate of degradation compensation/degradation delay compensation to be applied to each element according to stored life/performance dispersion information of each element. Accordingly, life uniformity of the elements may be enhanced by differentially applying the rate of degradation compensation/degradation delay compensation according to life/performance dispersion. 
     Hereinafter, the life controller  170  will be described in detail as follows. 
     As illustrated in  FIG. 7 , the life controller  170  includes a usage calculation unit  172 , a life reference (Ref.) unit  174 , and a rate matching unit  176 . 
     The usage calculation unit  172  calculates usage of the display panel when an image is finally displayed after the processing of the input image data is completed. The display panel usage may be calculated as the sum of currents I used to display the input image. The usage calculation unit  172  may include components which may be able to calculate usage such as a timer, data accumulation, an accumulation by position, an accumulation by time, and the like. 
     The life reference (Ref.) unit  174  includes information on positions and life information of elements in the display panel. The life reference (Ref.) unit  174  may include life information composed of values representing the life of the elements by location, region, or constant, and the like. Referring to  FIG. 8 , the elements in the display panel may have different performance and life. The performance and life of the elements are non-uniformly distributed according to process variations, driving time, driving environment, and the like. The life reference (Ref.) unit  174  may store life information of each element measured at the time of manufacturing of the display panel. 
     The rate matching unit  176  compares current usage of the display panel calculated by the usage calculation unit  172  with the life reference (Ref.) unit  174 . If the current usage is greater, the rate matching unit  176  increases the degree of delay, and if the current usage is smaller, the rate matching unit  176  lowers the degree of delay. In this manner, the rate matching unit controls the remaining life of all the elements to be similar. Thus, the rate matching unit  176  outputs I*α corrected by multiplying a constant “α” to the original usage I. Here, the constant a may be expressed by Equation 1 below.
 
α=( t   life,ref /τ) n   /I    [Equation 1]
     T life =τ·I −n , I −n : usage equation, τ: life Ref.   

     Here, t life  denotes time required for luminance to decrease. For example, t 50  may refer to time required for luminance to be halved to 50%. t life  may be set to vary according to system design methods, such as 20%, 30%, and 40%. The life Ref may be set to a constant obtained by sensing the life of the actual element. 
     The principle of rate matching will be described in detail with reference to  FIGS. 9 and 10 .  FIGS. 9 and 10  are graphs illustrating the characteristics of elements at points {circle around ( 1 )} and {circle around ( 2 )} of different positions. 
     According to the time and luminance graph of  FIG. 9 , it can be seen that the elements at points {circle around ( 1 )} and {circle around ( 2 )} exhibit the same luminance at first but the luminance of the element at the point {circle around ( 2 )} decreases more rapidly as time passes. That is, since the life of the element at the point {circle around ( 2 )} is relatively shorter than the life of the element at the point {circle around ( 1 )}, luminance at the point {circle around ( 2 )} is darker than the point {circle around ( 1 )} although the same time is used, causing non-uniformity of luminance. For this reason, as illustrated in the graph of time and usage of  FIG. 9 , if the elements at the points {circle around ( 1 )} and {circle around ( 2 )} are used under the same conditions, the degradation of the element at the point {circle around ( 2 )} progresses more rapidly. 
       FIG. 10  is a view illustrating the principle of controlling the remaining life of all elements to be similar according to an embodiment of the present invention. As discussed in  FIG. 9 , the life of the element at the point {circle around ( 2 )} is relatively shorter than the life of the element at the point {circle around ( 1 )}. Thus, in order to match the life of the elements at the points {circle around ( 1 )} and {circle around ( 2 )}, usage of the element at the point {circle around ( 2 )} must be relatively reduced. That is, as illustrated in the graph of time and usage of  FIG. 10 , use time of the elements is controlled to be different such that the element at the point {circle around ( 2 )} is used less than the element at the point {circle around ( 1 )}. The rate matching unit  176  controls the remaining life of all the elements to be similar in a manner of increasing the degree of delay if current usage of each element is large and decreasing the degree of delay if current usage is small on the basis of the life reference (Ref.) unit  174 . As a result, as illustrated in the graph of time and luminance of  FIG. 10 , degradations of the element at the point {circle around ( 1 )} and the element at the point {circle around ( 2 )} progress at the substantially same rate, preventing generation of a different in luminance between the points {circle around ( 1 )} and {circle around ( 2 )} although time passes. 
     As described above, an equation for calculating the rate of the degradation compensation/degradation delay compensation to be applied to each element according to the life information of the elements at the point {circle around ( 1 )} and the element at the point {circle around ( 2 )} is as follows. 
     
       
         
         
             
             
         
       
     
     Here, t 50 =τ·I −n , I −n : usage equation, τ: life Ref 
     Here, t life  refers to time required for luminance to decrease. For example, t 50  may refer to time required for luminance to be halved to 50%. t life  may be set to vary according to system design methods, such as 20%, 30%, 40%, and the like. The life Ref may be set to a constant obtained by sensing the life of an actual element. 
     In order to adjust the degradation rate as described above, the rate matching unit  176  outputs I*α corrected by multiplying a constant “α” to the original usage I. The constant a may be expressed by the equation below. 
     
       
         
           
             α 
             = 
             
               
                 
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                       t 
                       
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                         , 
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     The image is displayed on the display panel according to “I*α” corrected through the calculation process. The rate of the degradation compensation/degradation delay compensation to be applied to each element, that is, I*a, is calculated to be different according to the life information of the element at the point {circle around ( 1 )} and the element at the point {circle around ( 2 )}, and, as a result, the element at the point {circle around ( 1 )} and the element at the point {circle around ( 2 )} may be degraded at the substantially same rate. 
     For example, when t life  is set to a time for luminance to be halved to 50%, the above equation may be expressed as follows. 
     
       
         
           
             α 
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                       t 
                       
                         50 
                         , 
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                             n 
                           
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     As described above, the elements included in the display panel have different life, and the difference in life may cause non-uniformity of luminance of an image in the long term. In order to prevent this, life information of the elements in the display panel which is acquired in advance at the stage of manufacturing of the display device is stored in the life reference unit  174 , and a rate of degradation compensation/degradation delay compensation to be applied to each element may be differentially applied according to life information of each element, whereby life uniformity of the elements may be improved. 
       FIG. 11  is a first exemplary view illustrating main circuits of a display device according to an embodiment of the present invention. 
     As illustrated in  FIG. 11 , the display device according to the first embodiment of the present invention includes a delay unit  186 , a voltage/current conversion unit  184 , a life controller  170 , and a current/voltage conversion unit  182 . 
     The delay unit  186  may perform a delay algorithm generally used for improving image quality of the display device. For example, the delay unit  186  may perform various delay algorithms applied in the art, such as luminance reduction prevention or peak luminance algorithm, a degradation delay algorithm, an HDR algorithm, and the like. 
     The voltage/current conversion unit  184  converts an image signal processed by the delay unit  186  into a current value and delivers the current value to the life controller  170 . 
     The life controller  170  includes a usage calculation unit  172 , a life reference (Ref.) unit  174 , and a rate matching unit  176 . 
     The usage calculation unit  172  calculates usage of the display panel when an image is finally displayed after processing of input image data is completed. The display panel usage may be calculated as the sum of currents I used to display the input image. The usage calculation unit  172  may include components which may be able to calculate usage, such as a timer, data accumulation, accumulation by position, an accumulation by time, and the like. 
     The life reference (Ref.) unit  174  includes information on positions and life information of elements in the display panel. The life reference (Ref.) unit  174  may include life information composed of values representing the life of the elements by location, region, or constant, and the like. The elements in the display panel may have different performance and life. The performance and life of the elements are non-uniformly distributed according to process variations, driving time, driving environment, and the like. The life reference (Ref.) unit  174  may store life information of each element measured at the time of manufacturing of the display panel. 
     The rate matching unit  176  compares current usage of the display panel calculated by the usage calculation unit  172  with the life reference (Ref.) unit  174 . 
     If the current usage is greater, the rate matching unit  176  increases the degree of delay, and if the current usage is smaller, the rate matching unit  176  lowers the degree of delay. In this manner, the rate matching unit controls the remaining life of all the elements to be similar. Whether the current usage is large or small according to a life reference may be determined with the constant α. The constant α reflects a position, a panel, process dispersion, and the like, and the rate L may be matched by comparing the constant α. The constant α may be expressed as Equation 3 below.
 
α( x, y, z,  . . . ) * L ( x, y, z  . . . )=L after    [Equation 3]
     x: panel order (example)   y: per-position y coordinate (example)   z: per-position x coordinate (example)   

     
       
         
           
             
               
                 L 
                 after 
               
               
                 L 
                 ( 
                 
                   x 
                   , 
                   y 
                   , 
                   z 
                   , 
                   … 
                 
                 ⁢ 
                 
                     
                 
                 ) 
               
             
             = 
             
               α 
               ( 
               
                 x 
                 , 
                 y 
                 , 
                 z 
                 , 
                 … 
               
               ⁢ 
               
                   
               
               ) 
             
           
         
       
     
     As described above, the life dispersion acquired in advance is reflected on a delay rate when the delay algorithm is applied, whereby the same luminance is generated even at different positions, different regions, or different panels when the same algorithm is applied. Therefore, when the same usage occurs in all the elements, the same luminance may be obtained and the same life may be obtained. 
     Meanwhile, although the configuration of the delay unit  186  is replaced with a “compensation unit”, the same configuration may be applied. The compensation unit may perform a compensation algorithm generally used for improving image quality of the display device. Currently, many compensation algorithms compensate for luminance by increasing luminance of a partial region or by adjusting luminance of a specific pattern, and the like. However, the existing compensation method by the “compensation unit” is a method which does not consider the life of each element. Therefore, when the same algorithm is applied by reflecting a previously obtained life dispersion on the degree of compensation in applying the compensation algorithm, the same luminance is generated even at different positions, different regions, and different panels. If the life is basically different, different luminance appears in spite of the same compensation value, which results in a compensation error. Thus, if the same usage is generated in all the elements, the same luminance may appear and the same life may be obtained. Using this, difference in the life only in some panels or some regions may be prevented and luminance error dispersion may be reduced. 
       FIG. 12  is a second exemplary view illustrating main circuits of A display device of an embodiment of the present invention, in which a case where the configuration of a compensation unit  188  is added as compared with  FIG. 11 . 
     As illustrated in  FIG. 12 , the display device according to the first embodiment of the present invention includes a delay unit  186 , a compensation unit  188 , a voltage/current conversion unit  184 , a life controller  170 , and a current/voltage conversion unit  182 . 
     The delay unit  186  may perform a delay algorithm generally used for improving image quality of the display device. For example, the delay unit  186  may perform various delay algorithms applied in the art, such as luminance reduction prevention or peak luminance algorithm, a degradation delay algorithm, an HDR algorithm, and the like. 
     The compensation unit  188  may perform a compensation algorithm generally used for improving image quality of the display device. Currently, many compensation algorithms compensate for luminance by increasing luminance of a partial region or by adjusting luminance of a specific pattern, and the like. 
     The voltage/current conversion unit  184  converts an image signal processed by the delay unit  186  and the compensation unit  188  into a current value and delivers the current value to the life controller  170 . 
     The life controller  170  includes the usage calculation unit  172 , the life reference (Ref.) unit  174 , and the rate matching unit  176 . 
     The usage calculation unit  172  calculates usage of the display panel when an image is finally displayed after processing of input image data is completed. The display panel usage may be calculated as the sum of currents I used to display the input image. The usage calculation unit  172  may include components which may be able to calculate usage, such as a timer, data accumulation, accumulation by position, an accumulation by time, and the like. 
     The life reference (Ref.) unit  174  includes information on positions and life information of elements in the display panel. The life reference (Ref.) unit  174  may include life information composed of values representing the life of the elements by location, region, or constant, and the like. The elements in the display panel may have different performance and life. The performance and life of the elements are non-uniformly distributed according to process variations, driving time, driving environment, and the like. The life reference (Ref.) unit  174  may store life information of each element measured at the time of manufacturing of the display panel. 
     The rate matching unit  176  compares current usage of the display panel calculated by the usage calculation unit  172  with the life reference (Ref.) unit  174 . If the current usage is greater, the rate matching unit  176  increases the degree of delay, and if the current usage is smaller, the rate matching unit  176  lowers the degree of delay. In this manner, the rate matching unit controls the remaining life of all the elements to be similar. 
     The rate matching unit  176  reflects the life acquired in advance in the life reference (Ref.) Unit  174  to the delay speed when the delay/compensation algorithm is applied, Or the same luminance may be generated in different panels. If the life of each element is different, different luminance is displayed even with the same delay/compensation value, and this appears as dispersion of luminance error. Thus, embodiments of the present invention may exhibit the same luminance and the same life when the same amount of usage occurs in all the devices. 
     The rate matching unit  176  may generate the same luminance even at different positions, different regions, or different panels when the same algorithm is applied, by reflecting life dispersion obtained in advance from life reference (Ref.) unit  174  on a delay rate and on the degree of compensation when the delay/compensation algorithm is applied. If unique life of each element is different, different luminance may be obtained in spite of the same delay/compensation value, which results in a luminance error dispersion. Thus, when the same usage occurs in all the elements, the same luminance may be obtained and the same life may be obtained. 
     As described above, since compensation is performed such that all the elements included in a display panel have the same life by reflecting life characteristics of the elements, the entire region of the display panel may be degraded substantially at a uniform rate. Also, since a rate of a delay/compensation algorithm is controlled according to a difference in life between regions of the display panel, an error of the delay/compensation algorithm may be reduced to optimize a compensation performance. In addition, since the elements of the entire region of the display panel are controlled such that the life thereof come to an end substantially at the same time point, image quality may be uniformly maintained until the life of the display panel comes to an end. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the display device of the present disclosure without departing from the technical idea or scope of the disclosure. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.