Patent Publication Number: US-10762824-B2

Title: Timing controller and driving method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Korean Patent Application No. 10-2015-0138708, filed on Oct. 1, 2015, and entitled, “Timing Controller and Driving Method Thereof,” is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     One or more embodiments described herein relate to a timing controller and a method for driving a timing controller. 
     2. Description of the Related Art 
     Various displays have been developed to replace cathode ray tubes. Examples include liquid crystal displays, field emission displays, plasma display panels, organic light emitting displays. In an organic light emitting display, the quantity of light emitted for a given gray scale value may decrease when the accumulated emission quantity is increased. Also, when the level of current supplied to an organic light emitting diode of a pixel in the display is increased (in an attempt to maintain quantity of light), the life span of the display may be reduced. 
     SUMMARY 
     In accordance with one or more embodiments, a timing controller includes a degradation quantity generator to generate a degradation quantity for each of a plurality of pixels in a display panel based on image data; a degradation quantity accumulator to generate an accumulated degradation quantity based on the degradation quantity for each of the pixels; a feedback data generator to generate feedback image data based on the accumulated degradation quantity; and a feedback reflector to generate image data, in which the degradation quantity is compensated, based on the image data and the feedback image data, wherein an absolute value of the feedback image data, when the accumulated degradation quantity is a first accumulated degradation quantity level, is greater than an absolute value of the feedback image data when the accumulated degradation quantity is a second accumulated degradation quantity level higher than the first accumulated degradation quantity level. 
     The feedback data generator may include a scaling factor generator to generate a scaling factor; a scaling factor application rate generator to generate a scaling factor application rate based on the accumulated degradation quantity; and a scaling factor calculator to calculate the feedback image data based on the scaling factor and the scaling factor application rate. 
     The scaling factor application rate, when the accumulated degradation quantity is the first accumulated degradation quantity level, may be greater than the scaling factor application rate when the accumulated degradation quantity is the second accumulated degradation quantity level, and the feedback image data may be based on the following equation:
 
 fRGB =(1− R )+ R×SF  
 
where fRGB is the feedback image data, R is the scaling factor application rate, and SF is the scaling factor.
 
     When a level of the accumulated degradation quantity is in a first range, a level of the scaling factor application rate may be in a second range different from the first range, and the scaling factor may be generated based on the accumulated degradation quantity. The first range may be greater than the second range. 
     The timing controller may include a look-up table which is to output the feedback image data corresponding to the received scaling factor and scaling factor application rate. The accumulated degradation quantity may include sub accumulated degradation quantities for each pixel, and the feedback image data may includes sub feedback image data for each pixel. 
     In accordance with one or more other embodiments, a method for driving a timing controller includes generating a degradation quantity for each of a plurality of pixels in a display panel based on image data; generating an accumulated degradation quantity based on the degradation quantity for each of the pixels; generating feedback image data based on the accumulated degradation quantity; and generating image data, in which the degradation quantity is compensated, based on the image data and the feedback image data, wherein an absolute value of the feedback image data when the accumulated degradation quantity is a first accumulated degradation quantity level is greater than an absolute value of the feedback image data when the accumulated degradation quantity is a second accumulated degradation quantity level higher than the first accumulated degradation quantity level. 
     Generating the feedback image data may include generating a scaling factor; generating a scaling factor application rate based on the accumulated degradation quantity; and calculating the feedback image data based on the scaling factor and the scaling factor application rate. The feedback image data may be expressed by the following equation:
 
 fRGB =(1− R )+ R×SF  
 
where fRGB is the feedback image data, R is the scaling factor application rate, and SF is the scaling factor.
 
     When a level of the accumulated degradation quantity is in a first range, a level of the scaling factor application rate in a second range may be different from the first range, and the scaling factor may be generated based on the accumulated degradation quantity. The first range may be greater than the second range. 
     In accordance with one or more other embodiments, an apparatus includes first logic to generate a degradation quantity for each of a plurality of pixels based on first image data; second logic to generate an accumulated degradation quantity based on the degradation quantity for each of the pixels; third logic to generate feedback image data based on the accumulated degradation quantity; and fourth logic to generate second image data for output to a display, the second image data corresponds to a compensated degradation quantity based on the first image data and the feedback image data. 
     An absolute value of the feedback image data, when the accumulated degradation quantity is a first accumulated degradation quantity level, may be greater than an absolute value of the feedback image data when the accumulated degradation quantity is a second accumulated degradation quantity level higher than the first accumulated degradation quantity level. The third logic may generate a scaling factor; generate a scaling factor application rate based on the accumulated degradation quantity; and calculate the feedback image data based on the scaling factor and the scaling factor application rate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features will become apparent to those of skill in the art by describing in detail exemplary embodiments with reference to the attached drawings in which: 
         FIG. 1  illustrates an embodiment of an organic light emitting display device; 
         FIG. 2  illustrates an embodiment of a timing controller; 
         FIG. 3  illustrates an embodiment of a feedback data generating unit; 
         FIGS. 4 and 5  illustrate examples of displayed images; 
         FIG. 6  illustrates an example of an accumulated degradation quantity; 
         FIG. 7  illustrates an example of a change in a scaling factor application rate; 
         FIG. 8  illustrates an embodiment of a method for driving a timing controller; and 
         FIG. 9  illustrates an embodiment for generating feedback image data. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey exemplary implementations to those skilled in the art. The embodiments may be combined to form additional embodiments. 
     In the drawings, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout. 
     When an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the another element or be indirectly connected or coupled to the another element with one or more intervening elements interposed therebetween. In addition, when an element is referred to as “including” a component, this indicates that the element may further include another component instead of excluding another component unless there is different disclosure. 
       FIG. 1  illustrates an embodiment of an organic light emitting display device including a display panel  1000  and a display panel driver  2000 . The display panel  1000  includes pixels P(1, 1) to P(m, n) (m and n equal to or larger than 2), m scan lines S 1  to Sm which transmit scan signals to the pixels P(1, 1) to P(m, n) and extend in a first direction, n data lines D 1  to Dn which transmit data voltages to the pixels P and extend in a second direction, and m emission control lines E 1  to Em which transmit emission control signals to the pixels P and extend in the first direction. Each pixel P(i, j) may be electrically connected to a corresponding scan line Si, data line Dj, and emission control line Ei. In another embodiment, two or more scan lines Si and Si−1 may be electrically connected to each pixel P(i, j). 
     The display panel driver  2000  generates data voltages for input to the data lines D, scan signals for input to the scan lines S, and emission control signals for input to the emission control lines E in order to drive the display panel  1000 . The display panel driver  2000  includes a timing controller (TC)  2200 , a data driver  2300 , and a scan driver  2400 . The timing controller  2200 , the data driver  2300 , and the scan driver  2400  may be implemented by separate electronic devices, or the entire display panel driver  2000  may be implemented by one electronic device (for example, a display driving Integrated Circuit (IC)). 
     The timing controller  2200  receives image data RGB and timing signals from a source. The image data RGB includes gray scale values for the pixels P. According to an exemplary embodiment, the gray scale values may be in a range of 0 to 255. When the gray scale value is low, the luminance of light emitted by a pixel is low, e.g., a gray scale value of 0 may correspond to black. 
     The timing signals include a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal DE, and a dot clock signal CLK. The timing controller  2200  generates timing control signals for controlling operation timings of the data driver  2300  and the scan driver  2400  based on the timing signals. The timing control signals include a data timing control signal DCS for controlling an operation timing and a data sampling start timing of the data driver  2300 , and a scan timing control signal SCS for controlling an operation timing of the scan driver  2400 . 
     The timing controller  2200  performs compensation on the image data RUB in consideration of an accumulated degradation quantity and outputs compensated image data RGB′ to the data driver  2300  for displaying an image. 
     The data driver  2300  latches the compensated image data RGB′ from the timing controller  2200  based on the data timing control signal DCS. In one embodiment, the data driver  2300  may include a plurality of source drive ICs electrically connected to the data lines D of the display panel  1000 , for example, by a Chip On Glass (COG) process or a Tape Automated Bonding (TAB) process. 
     The scan driver  2400  sequentially supplies the scan signals to the scan lines S based on the scan timing control signal SCS and sequentially applies the emission control signals to the emission control lines E. The scan driver  2400  may be directly formed on a substrate of the display panel  1000 , for example, by a Gate In Panel (GIP) scheme, or may be electrically connected to the scan lines S and the emission control lines E by the TAB scheme. 
       FIG. 2  illustrates an embodiment of a timing controller, which, for example, may correspond to timing controller  2200 . For convenience, it is assumed that the image data RGB is image data during 1 frame period for all of the pixels P. 
     Referring to  FIGS. 1 and 2 , the timing controller  2200  includes a degradation quantity generating unit  2210 , a degradation quantity accumulating unit  2220 , a feedback data generating unit  2230 , and a feedback reflecting unit  2240 . 
     The degradation quantity generating unit  2210  generates degradation quantities Det based on the image data RGB. The degradation quantities Det include degradation quantities of the respective pixels P. For example, for one pixel P(i, j), the degradation quantity generating unit  2210  may extract a gray scale value corresponding to the pixel P(i, j) in the image data RGB and may calculate the degradation quantity of the pixel P(i, j) corresponding to the extracted gray scale value. When the calculation is performed on all of the pixels P, degradation quantities of all of the pixels P are generated. The degradation quantities Det include degradation quantities of the respective pixels P. According to an exemplary embodiment, the degradation quantity generating unit  2210  may include, for example, a look-up table which outputs a degradation quantity when a gray scale value is input. 
     The degradation quantity accumulating unit  2220  generates an accumulated degradation quantity tDet based on the degradation quantities Det. The accumulated degradation quantity tDet includes an accumulated degradation quantity of all the pixels P, in which degradation quantities of the respective pixels P are all added. According to an exemplary embodiment, the accumulated degradation quantity tDet may also include accumulated degradation quantities for the respective pixels P, in which degradation quantities of the respective pixels P are added for each pixel. 
     The feedback data generating unit  2230  generates feedback image data fRGB based on the accumulated degradation quantity tDet. The feedback image data fRGB includes feedback gray scale values corresponding to the pixels P. When an absolute value of the feedback image data fRGB is large, the degradation quantity may be compensated to a greater degree. According to an exemplary embodiment, the feedback image data fRGB may also include sub feedback image data for each pixel. 
     The feedback reflecting unit  2240  generates the image data RGB′, in which the degradation quantity is compensated, based on the image data RGB and the feedback image data fRGB. The compensated image data RGB′ includes compensated gray scale values corresponding to the pixels P. The compensated gray scale values may be generated by adding the feedback gray scale values within the feedback image data fRGB to the gray scale values within the image data RGB or by subtracting the feedback gray scale values within the feedback image data fRGB from the gray scale values within the image data RGB. 
     In  FIG. 2 , the degradation quantity generating unit  2210 , the degradation quantity accumulating unit  2220 , the feedback data generating unit  2230 , the feedback reflecting unit  2240  are separated. In another embodiment, two or more of the degradation quantity generating unit  2210 , the degradation quantity accumulating unit  2220 , the feedback data generating unit  2230 , the feedback reflecting unit  2240  may be implemented in one IC. 
       FIG. 3  illustrates an embodiment of a feedback data generating unit, which, for example, may correspond to feedback data generating unit  2230  in  FIG. 2 . Referring to  FIG. 3 , the feedback data generating unit  2230  includes a scaling factor generating unit  2231 , a scaling factor application rate generating unit  2232 , and a scaling factor applying unit  2233 . The scaling factor generating unit  2231  generates a scaling factor SF. 
     The scaling factor application rate generating unit  2232  generates a scaling factor application rate R based on the accumulated degradation quantity tDet. For example, when the level of the accumulated degradation quantity tDet is high (e.g., above a predetermined value), a low scaling factor application rate R is generated. For example, when the accumulated degradation quantity tDet is increased, the scaling factor application rate R is decreased. 
     The scaling factor application unit  2233  calculates the feedback image data fRGB based on the scaling factor SF generated by the scaling factor generating unit  2231  and the scaling factor application rate R generated by the scaling factor application rate generating unit  2232 . The scaling factor applying unit  2233  may include a look-up table. When the scaling factor applying unit  2233  receives the scaling factor SF and the scaling factor application rate R, the look-up table may output the feedback image data fRGB corresponding to the received scaling factor SF and scaling factor application rate R. The feedback image data fRGB may be expressed by Equation 1.
 
 fRGB =(1− R )+ R×SF   (1)
 
where fRGB is feedback image data, R is scaling factor application rate, and SF is a scaling factor.
 
     When the scaling factor SF is larger than 1 and when the scaling factor application rate R is large (e.g., above a predetermined value), the absolute value of the feedback image data fRGB is large and a change in luminance due to degradation is compensated to a greater extent. When the level of the accumulated degradation quantity tDet is high (e.g., above a predetermined value), the scaling factor application rate R is low. Thus, the absolute value of the feedback image data fRGB is decreased. For example, the absolute value of the image data fRGB when the accumulated degradation quantity tDet has a first level is greater than an absolute value of the feedback image data when the accumulated degradation quantity tDet has a second level that is higher than the first level. Thus, when the accumulated degradation quantity is large (e.g., above a predetermined value), the degree of compensation of degradation quantity is decreased. 
     In  FIG. 3 , the scaling factor generating unit  2231 , the scaling factor application rate generating unit  2232 , and the scaling factor applying unit  223  are separated. In another embodiment, two or more of the scaling factor generating unit  2231 , the scaling factor application rate generating unit  2232 , and the scaling factor applying unit  223  may be implemented in one IC. 
       FIGS. 4 and 5  illustrate examples of images displayed by the organic light emitting display device of  FIG. 1 .  FIG. 6  is a graph illustrating an example of an accumulated degradation quantity generated by the degradation quantity accumulating unit during the display of the image in  FIGS. 4 and 5 .  FIG. 7  is a graph illustrating a change in a scaling factor application rate generated by the scaling factor application rate generating unit during the display of the image of  FIGS. 4 and 5 . In the following description, the accumulated degradation quantity tDet includes an accumulated degradation quantity of all the pixels P, in which degradation quantities of the respective pixels P are all added. 
       FIG. 4  illustrates an image displayed in a section from a time of 0 to a first time t 1  (see  FIG. 6 ), and  FIG. 5  illustrates an image displayed in a section from the first time t 1  to a second time t 2  (see  FIG. 6 ) that is after the first time t 1  (see  FIG. 6 ). 
     Referring to  FIG. 4 , in the section from the time of 0 to the first time t 1 , the gray scale value of a portion corresponding to a first area A 1  in the image data RGB is 0 (e.g., black). As a result, the portion corresponding to the first area A 1  in the display panel  1000  does not emit light. The gray scale value of a portion corresponding to a second area A 2  (which does not overlap the first area A 1  in the image data RGB, see  FIG. 1 ) is greater than 0. As a result, the portion corresponding to the second area A 2  in the display panel  1000  emits light. Thus, only the pixels in the second area A 2  emit light, and thus are subject to being degraded due to emission. (For convenience of the description, it may be assumed that the gray scale values of the pixels in the second area A 2  in the image data RGB are the same as each other, but this is only an example and is not necessary). In the section from time t=0 to time t 1 , some portions of the display panel  1000  emit light. Therefore, the accumulated degradation quantity tDet (see  FIG. 6 ) is increased. 
     Referring to  FIG. 5 , in the section from time t 1  to time t 2 , the gray scale value of the portion corresponding to the first area A 1  in the image data RGB is greater than 0. As a result, the portion corresponding to the first area A 1  in the display panel  1000  emits light. The gray scale value of the portion corresponding to the second area A 2  in the image data RGB is 0. As a result, the portion corresponding to the second area A 2  in the display panel  1000  does not emit light. Thus, only the pixels in the first area A 1  emit light, and therefore are subject to being degraded due to emission. (For convenience of the description, it may be assumed that the gray scale values of the pixels in the first area A 1  in the image data RGB are the same as each other and are the same as the gray scale values of the pixels in the second area A 2  in the image data RGB from the time=0 to time t 1 , but this is only an example and is not necessary.) In the section from time t 1  to time t 2 , some portions of the display panel  1000  emit light. Therefore, the accumulated degradation quantity tDet is increased. 
     Referring to  FIG. 6 , the accumulated degradation quantity tDet in the section from time=0 to second time t 2  is increased. At first time t 1 , the level of the accumulated degradation quantity tDet is a first accumulated degradation quantity level tDet 1 . At the second time t 2 , the level of the accumulated degradation quantity tDet is a second accumulated degradation quantity level tDet 2 . In  FIG. 6 , the curve for time t between first time t 1  and the second time t 2  has a greater slope than the slope of the curve between time t=0 to first time t 1 . The curve may have different slopes in another embodiment. 
     Referring to  FIG. 7 , at first time t 1 , the accumulated degradation quantity tDet is the first accumulated degradation quantity level tDet 1 . Thus, the scaling factor application rate generating unit  2232  (see, e.g.,  FIG. 3 ) generates a first scaling factor application rate R 1 . At the second time t 2 , the accumulated degradation quantity tDet is the second accumulated degradation quantity level tDet 2 . Thus, the scaling factor application rate generating unit  2232  (see, e.g.,  FIG. 3 ) generates a second scaling factor application rate R 2 . In this embodiment, the first scaling factor application rate R 1  is greater than the second scaling factor application rate R 2 . Thus, when the accumulated degradation quantity tDet is increased, the scaling factor application rate R is decreased. 
     The first scaling factor application rate R 1  is greater than the second scaling factor application rate R 2 . Thus, the absolute value of the feedback image data fRGB (see, e.g.,  FIG. 2 ) at first time t 1  is greater than the absolute value of the feedback image data fRGB (see, e.g.,  FIG. 2  at second time t 2 . 
       FIG. 8  illustrates an embodiment of a method for driving a timing controller, which, for example, may correspond to timing controller  2200  in  FIG. 1 . For illustrative purposes only the method will be described with reference to  FIGS. 1 to 8 . 
     In operation S 1100 , the degradation quantity generating unit  2210  generates degradation quantities Det based on image data RGB from a source. The degradation quantities Det include degradation quantities of respective pixels P. 
     In operation S 1200 , the degradation quantity accumulating unit  2220  generates an accumulated degradation quantity tDet based on the degradation quantities of respective pixels in the degradation quantities Det. The accumulated degradation quantity tDet may include accumulated degradation quantities for respective pixels P, in which degradation quantities of the respective pixels P are added for each pixel. The accumulated degradation quantity tDet may include an accumulated degradation quantity of all the pixels P, in which the degradation quantities of the respective pixels are added. 
     In operation S 1300 , the feedback data generating unit  2230  generates feedback image data fRGB based on the accumulated degradation quantity tDet. 
     In operation S 1400 , the feedback reflecting unit  2240  generates compensated image data RGB′ based on the image data RGB and the feedback image data fRGB from the feedback data generating unit  2230 . 
       FIG. 9  illustrates an embodiment of an operation for generating feedback image data based on the accumulated degradation quantity of  FIG. 8 . Operation S 1300  includes operation S 1310 , operation S 1320 , and operation S 1330 . 
     In operation S 1310 , the scaling factor generating unit  2231  generates a scaling factor SF. According to an exemplary embodiment, the scaling factor SF may also be formed based on the accumulated degradation quantity tDet. 
     In operation S 1320 , the scaling factor application rate generating unit  2232  generates a scaling factor application rate R based on the accumulated degradation quantity tDet. When the accumulated degradation quantity tDet is increased, the scaling factor application rate R is decreased as described above. 
     In operation S 1330 , the scaling factor applying unit  2233  generates the feedback image data fRGB based on the scaling factor SF and the scaling factor application rate R. The feedback image data fRGB is inversely proportional to the accumulated degradation quantity tDet. 
     The methods, processes, and/or operations described herein may be performed by code or instructions to be executed by a computer, processor, controller, or other signal processing device. The computer, processor, controller, or other signal processing device may be those described herein or one in addition to the elements described herein. Because the algorithms that form the basis of the methods (or operations of the computer, processor, controller, or other signal processing device) are described in detail, the code or instructions for implementing the operations of the method embodiments may transform the computer, processor, controller, or other signal processing device into a special-purpose processor for performing the methods described herein. 
     The controllers, units, drivers, and other processing features of the embodiments disclosed herein may be implemented in logic which, for example, may include hardware, software, or both. When implemented at least partially in hardware, the controllers, units, drivers, and other processing features may be, for example, any one of a variety of integrated circuits including but not limited to an application-specific integrated circuit, a field-programmable gate array, a combination of logic gates, a system-on-chip, a microprocessor, or another type of processing or control circuit. 
     When implemented in at least partially in software, the controllers, units, drivers, and other processing features may include, for example, a memory or other storage device for storing code or instructions to be executed, for example, by a computer, processor, microprocessor, controller, or other signal processing device. The computer, processor, microprocessor, controller, or other signal processing device may be those described herein or one in addition to the elements described herein. Because the algorithms that form the basis of the methods (or operations of the computer, processor, microprocessor, controller, or other signal processing device) are described in detail, the code or instructions for implementing the operations of the method embodiments may transform the computer, processor, controller, or other signal processing device into a special-purpose processor for performing the methods described herein. 
     By way of summation and review, in at least one type of an organic light emitting display, the quantity of light emitted in response to a same gray scale value is decreased when an accumulated emission quantity is increased. Also, when the level of current supplied to an organic light emitting diode of a pixel of the display is increased (in an attempt to maintain quantity of light), the life span of the display may be reduced. 
     In accordance with one or more of the aforementioned embodiments, a timing controller and a method for driving a timing controller in an organic light emitting display increases the life span of the display by decreasing the quantity of fed-back gray scale values when an accumulated emission quantity is increased. 
     Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the embodiments set forth in the claims.