Timing controller and driving method thereof

A timing controller includes a degradation quantity generator, a degradation quantity accumulator, a feedback data generator, and a feedback reflector. The degradation quantity generator generates a degradation quantity for each of a plurality of pixels in a display panel based on image data. The degradation quantity accumulator generates an accumulated degradation quantity based on the degradation quantity for each of the pixels. The feedback data generator generates feedback image data based on the accumulated degradation quantity. The feedback reflector generates image data, in which the degradation quantity is compensated, based on the 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, 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.

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

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.

DETAILED DESCRIPTION

FIG. 1illustrates an embodiment of an organic light emitting display device including a display panel1000and a display panel driver2000. The display panel1000includes pixels P(1, 1) to P(m, n) (m and n equal to or larger than 2), m scan lines S1to Sm which transmit scan signals to the pixels P(1, 1) to P(m, n) and extend in a first direction, n data lines D1to Dn which transmit data voltages to the pixels P and extend in a second direction, and m emission control lines E1to 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 driver2000generates 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 panel1000. The display panel driver2000includes a timing controller (TC)2200, a data driver2300, and a scan driver2400. The timing controller2200, the data driver2300, and the scan driver2400may be implemented by separate electronic devices, or the entire display panel driver2000may be implemented by one electronic device (for example, a display driving Integrated Circuit (IC)).

The timing controller2200receives 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 controller2200generates timing control signals for controlling operation timings of the data driver2300and the scan driver2400based 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 driver2300, and a scan timing control signal SCS for controlling an operation timing of the scan driver2400.

The timing controller2200performs compensation on the image data RUB in consideration of an accumulated degradation quantity and outputs compensated image data RGB′ to the data driver2300for displaying an image.

The data driver2300latches the compensated image data RGB′ from the timing controller2200based on the data timing control signal DCS. In one embodiment, the data driver2300may include a plurality of source drive ICs electrically connected to the data lines D of the display panel1000, for example, by a Chip On Glass (COG) process or a Tape Automated Bonding (TAB) process.

The scan driver2400sequentially 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 driver2400may be directly formed on a substrate of the display panel1000, 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. 2illustrates an embodiment of a timing controller, which, for example, may correspond to timing controller2200. For convenience, it is assumed that the image data RGB is image data during 1 frame period for all of the pixels P.

Referring toFIGS. 1 and 2, the timing controller2200includes a degradation quantity generating unit2210, a degradation quantity accumulating unit2220, a feedback data generating unit2230, and a feedback reflecting unit2240.

The degradation quantity generating unit2210generates 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 unit2210may 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 unit2210may include, for example, a look-up table which outputs a degradation quantity when a gray scale value is input.

The degradation quantity accumulating unit2220generates 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 unit2230generates 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 unit2240generates 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.

InFIG. 2, the degradation quantity generating unit2210, the degradation quantity accumulating unit2220, the feedback data generating unit2230, the feedback reflecting unit2240are separated. In another embodiment, two or more of the degradation quantity generating unit2210, the degradation quantity accumulating unit2220, the feedback data generating unit2230, the feedback reflecting unit2240may be implemented in one IC.

FIG. 3illustrates an embodiment of a feedback data generating unit, which, for example, may correspond to feedback data generating unit2230inFIG. 2. Referring toFIG. 3, the feedback data generating unit2230includes a scaling factor generating unit2231, a scaling factor application rate generating unit2232, and a scaling factor applying unit2233. The scaling factor generating unit2231generates a scaling factor SF.

The scaling factor application rate generating unit2232generates 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 unit2233calculates the feedback image data fRGB based on the scaling factor SF generated by the scaling factor generating unit2231and the scaling factor application rate R generated by the scaling factor application rate generating unit2232. The scaling factor applying unit2233may include a look-up table. When the scaling factor applying unit2233receives 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.

InFIG. 3, the scaling factor generating unit2231, the scaling factor application rate generating unit2232, and the scaling factor applying unit223are separated. In another embodiment, two or more of the scaling factor generating unit2231, the scaling factor application rate generating unit2232, and the scaling factor applying unit223may be implemented in one IC.

FIGS. 4 and 5illustrate examples of images displayed by the organic light emitting display device ofFIG. 1.FIG. 6is a graph illustrating an example of an accumulated degradation quantity generated by the degradation quantity accumulating unit during the display of the image inFIGS. 4 and 5.FIG. 7is 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 ofFIGS. 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. 4illustrates an image displayed in a section from a time of 0 to a first time t1(seeFIG. 6), andFIG. 5illustrates an image displayed in a section from the first time t1to a second time t2(seeFIG. 6) that is after the first time t1(seeFIG. 6).

Referring toFIG. 4, in the section from the time of 0 to the first time t1, the gray scale value of a portion corresponding to a first area A1in the image data RGB is 0 (e.g., black). As a result, the portion corresponding to the first area A1in the display panel1000does not emit light. The gray scale value of a portion corresponding to a second area A2(which does not overlap the first area A1in the image data RGB, seeFIG. 1) is greater than 0. As a result, the portion corresponding to the second area A2in the display panel1000emits light. Thus, only the pixels in the second area A2emit 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 A2in 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 t1, some portions of the display panel1000emit light. Therefore, the accumulated degradation quantity tDet (seeFIG. 6) is increased.

Referring toFIG. 5, in the section from time t1to time t2, the gray scale value of the portion corresponding to the first area A1in the image data RGB is greater than 0. As a result, the portion corresponding to the first area A1in the display panel1000emits light. The gray scale value of the portion corresponding to the second area A2in the image data RGB is 0. As a result, the portion corresponding to the second area A2in the display panel1000does not emit light. Thus, only the pixels in the first area A1emit 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 A1in 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 A2in the image data RGB from the time=0 to time t1, but this is only an example and is not necessary.) In the section from time t1to time t2, some portions of the display panel1000emit light. Therefore, the accumulated degradation quantity tDet is increased.

Referring toFIG. 6, the accumulated degradation quantity tDet in the section from time=0 to second time t2is increased. At first time t1, the level of the accumulated degradation quantity tDet is a first accumulated degradation quantity level tDet1. At the second time t2, the level of the accumulated degradation quantity tDet is a second accumulated degradation quantity level tDet2. InFIG. 6, the curve for time t between first time t1and the second time t2has a greater slope than the slope of the curve between time t=0 to first time t1. The curve may have different slopes in another embodiment.

Referring toFIG. 7, at first time t1, the accumulated degradation quantity tDet is the first accumulated degradation quantity level tDet1. Thus, the scaling factor application rate generating unit2232(see, e.g.,FIG. 3) generates a first scaling factor application rate R1. At the second time t2, the accumulated degradation quantity tDet is the second accumulated degradation quantity level tDet2. Thus, the scaling factor application rate generating unit2232(see, e.g.,FIG. 3) generates a second scaling factor application rate R2. In this embodiment, the first scaling factor application rate R1is greater than the second scaling factor application rate R2. Thus, when the accumulated degradation quantity tDet is increased, the scaling factor application rate R is decreased.

The first scaling factor application rate R1is greater than the second scaling factor application rate R2. Thus, the absolute value of the feedback image data fRGB (see, e.g.,FIG. 2) at first time t1is greater than the absolute value of the feedback image data fRGB (see, e.g.,FIG. 2at second time t2.

FIG. 8illustrates an embodiment of a method for driving a timing controller, which, for example, may correspond to timing controller2200inFIG. 1. For illustrative purposes only the method will be described with reference toFIGS. 1 to 8.

In operation S1100, the degradation quantity generating unit2210generates degradation quantities Det based on image data RGB from a source. The degradation quantities Det include degradation quantities of respective pixels P.

In operation S1200, the degradation quantity accumulating unit2220generates 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 S1300, the feedback data generating unit2230generates feedback image data fRGB based on the accumulated degradation quantity tDet.

In operation S1400, the feedback reflecting unit2240generates compensated image data RGB′ based on the image data RGB and the feedback image data fRGB from the feedback data generating unit2230.

FIG. 9illustrates an embodiment of an operation for generating feedback image data based on the accumulated degradation quantity ofFIG. 8. Operation S1300includes operation S1310, operation S1320, and operation S1330.

In operation S1310, the scaling factor generating unit2231generates 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 S1320, the scaling factor application rate generating unit2232generates 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 S1330, the scaling factor applying unit2233generates 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 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.