KR102572575B1 - Organic light emitting display device and method for driving thereof - Google Patents

Abstract

In the present embodiments, a display panel in which subpixels including an organic light emitting diode and a driving transistor for driving the organic light emitting diode are arranged in a matrix type, a data driver connected to the display panel, and a subpixel line for sensing driving among a plurality of subpixel lines and a sensing unit configured to sense a voltage of a sensing line electrically connected to a first node of a driving transistor in a subpixel on a sensing subpixel line corresponding to a pixel line and perform a sensing process to output a sensed value, wherein the data driver comprises: An organic light emitting display device and a driving method for supplying different recovery image data voltages according to the gradation of image data of a corresponding subpixel during a frame period after sensing processing to a second node of the driving transistor after sensing processing, and a method for driving the same .

Description

Organic light emitting display device and its driving method {ORGANIC LIGHT EMITTING DISPLAY DEVICE AND METHOD FOR DRIVING THEREOF}

The present embodiments relate to an organic light emitting display device displaying an image and a driving method thereof.

Recently, an organic light emitting display device that has been in the limelight as a display device uses an organic light emitting diode (OLED) that emits light by itself, and has advantages such as fast response speed, luminous efficiency, luminance, and viewing angle.

However, in an organic light emitting display device, variation in characteristic values such as a threshold voltage (Vth) and mobility of a driving transistor occurs for each pixel due to various reasons such as process variation and deterioration. Therefore, the amount of current driving each organic light emitting diode is different, and as a result, a luminance deviation occurs between pixels.

In order to solve this problem, an external compensation method for compensating for a characteristic change of a driving transistor included in each pixel through correction of input image data has been disclosed.

When this external compensation method is applied to an organic light emitting display device, for various reasons, the luminance of a sub-pixel line where mobility sensing for external compensation is performed is higher than the luminance of a sub-pixel line where mobility sensing for external compensation is not performed. Since it is low, a sub-pixel line in which mobility sensing for external compensation is performed is visible to the user's eyes.

A visibility phenomenon in which a sub-pixel line in which mobility sensing for external compensation is performed is visible to the user's eyes may occur in various types of display devices using external compensation in addition to organic light emitting display devices.

An object of the present embodiments is to provide an organic light emitting display device and a driving method capable of reducing a level visible to a user's eye of a sub-pixel line in which mobility sensing for real-time external compensation is performed.

In one aspect, in the present embodiments, a display panel, a data driver connected to the display panel, and a first node of a driving transistor in a subpixel on a sensing subpixel line corresponding to a subpixel line to be sensed driven among a plurality of subpixel lines and It is possible to provide an organic light emitting display device including a sensing unit that performs a sensing process of sensing a voltage of an electrically connected sensing line and outputting a sensing value.

In this case, subpixels including organic light emitting diodes and driving transistors for driving the organic light emitting diodes may be arranged in a matrix type on the display panel.

After the sensing process, the data driver may supply different recovery image data voltages to the second node of the driving transistor according to the gray level of the image data of the corresponding subpixel during a frame period after the sensing process.

In another aspect, the present embodiments may provide a method for driving an organic light emitting display device including a display panel and a data driver connected to an upper or lower portion of the display panel.

A method of driving an organic light emitting display device includes a sensing process of sensing characteristic values of subpixels on sensing subpixel lines of a predetermined number of sensing subpixel lines in at least one predetermined area of a display panel and outputting a sensing value. and a recovery driving step of supplying different recovery image data voltages according to gradations of image data of resolution subpixels during the frame period after the sensing process to the second node of the driving transistor after the sensing process and the sensing process. can

According to the present embodiments as described above, an organic light emitting display device capable of reducing the level visible to the user's eye of a sub-pixel line in which mobility sensing for an efficient panel defect detection method and real-time external compensation is performed, and Its driving method can be provided.

1 is a system configuration diagram of an organic light emitting display device according to the present embodiments.
FIG. 2 is an exemplary view showing the structure of pixels included in an organic light emitting display panel applied to the organic light emitting display device of FIG. 1 .
3 is a diagram illustrating each sub-pixel circuit of an organic light emitting display device according to the present embodiments.
4 is a diagram illustrating a subpixel compensation circuit of an organic light emitting display device according to the present embodiments.
5 is a diagram for explaining a mobility sensing principle of a driving transistor (DRT) of an organic light emitting display device according to the present embodiments.
6 is a diagram illustrating timing of driving and sensing mobility sensing according to the present embodiments.
7 is an exemplary diagram illustrating sub-pixel lines in which mobility sensing for external compensation is performed in a general organic light emitting display device.
8 is an exemplary view illustrating a concept of performing an image recovery process to mitigate a phenomenon in which sensing subpixel lines are visible after mobility sensing in an organic light emitting display device according to an exemplary embodiment.
9 illustrates a difference in charging time of the first electrode and a difference in a non-emission area according to the gradation of input image data.
10 and 11 show the required compensation luminance for image recovery processing according to the low and high gradations of FIG. 9 .
12 is a flowchart of setting a recovery voltage by dividing the gradation of input image data into a specific number of remodeling ranges.
13 is a timing diagram of driving and sensing the mobility of a driving transistor (DRT) in a sub-pixel of the organic light emitting display device 100 according to the present embodiments for image data of low grayscale, and processing of image recovery.
14 is a timing diagram of mobility sensing driving and sensing processing of a driving transistor (DRT) in a sub-pixel of an organic light emitting display device according to the present embodiments for high grayscale image data, and image recovery processing.
15 is an example illustrating a relationship between recovery voltages according to gray levels during image recovery processing after driving and sensing the mobility of a driving transistor (DRT) in a subpixel of an organic light emitting display device according to the present embodiments.
16 is a diagram illustrating a light emitting state for each sensing progress position during mobility sensing driving and sensing processing according to the present embodiments.
17 and 18 are diagrams showing differences in restored image data voltages for each gradation at each sensing location during image recovery processing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention are described in detail below with reference to exemplary drawings. In adding reference numerals to components of each drawing, the same components may have the same numerals as much as possible even if they are displayed on different drawings. In addition, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description may be omitted.

Also, terms such as first, second, A, B, (a), and (b) may be used in describing the components of the present invention. These terms are only used to distinguish the component from other components, and the nature, sequence, order, or number of the corresponding component is not limited by the term. When an element is described as being “connected,” “coupled to,” or “connected” to another element, that element is or may be directly connected to that other element, but intervenes between each element. It will be understood that may be "interposed", or each component may be "connected", "coupled" or "connected" through other components.

1 is a schematic system configuration diagram of an organic light emitting display device 100 according to the present embodiments.

Referring to FIG. 1 , an organic light emitting display device 100 according to the present exemplary embodiments includes a plurality of data lines DL1 to DLm and a plurality of gate lines GL1 to GLn, and a plurality of subpixels SP. : The display panel 110 on which sub pixels are disposed, the data driver 120 connected to the top or bottom of the display panel 110 and driving the plurality of data lines DL1 to DLm, and the plurality of gate lines ( It includes a gate driver 130 that drives GL1 to GLn, a data driver 120 and a timing controller 140 that controls the gate driver 130, and the like.

Referring to FIG. 1 , a plurality of subpixels SP are arranged in a matrix type on the display panel 110 . Accordingly, a plurality of sub-pixel lines exist in the display panel 110, and the sub-pixel lines may be sub-pixel rows or sub-pixel columns. Below, subpixel rows are referred to as subpixel lines.

The data driver 120 drives the plurality of data lines DL1 to DLm by supplying data voltages to the plurality of data lines DL1 to DLm. Here, the data driver 120 is also referred to as a source driver.

The gate driver 130 sequentially drives the plurality of gate lines GL1 to GLn by sequentially supplying scan signals to the plurality of gate lines GL1 to GLn. Here, the gate driver 130 is also referred to as a scan driver.

The timing controller 140 controls the data driver 120 and the gate driver 130 by supplying various control signals to the data driver 120 and the gate driver 130 .

The timing controller 140 starts scanning according to the timing implemented in each frame, and converts input image data input from the outside to suit the data signal format used by the data driver 120 to convert the converted image data (Data ), and controls data drive at an appropriate time according to the scan.

Under the control of the timing controller 140, the gate driver 130 sequentially supplies scan signals of an on voltage or an off voltage to the plurality of gate lines GL1 to GLn to provide a plurality of gate lines. (GL1~GLn) are sequentially driven.

When a specific gate line is opened, the data driver 120 converts the video data (Data) received from the timing controller 140 into an analog data voltage (Vdata) and supplies it to a plurality of data lines (DL1 to DLm). , drives a plurality of data lines (DL1 to DLm).

The data driver 120 may include a logic unit including a shift register and a latch circuit, a digital analog converter (DAC), an output buffer, and the like, and in some cases, characteristics of a subpixel ( Example: A sensing unit (310 in FIG. 4 ) for sensing characteristics of a subpixel may be further included to compensate for threshold voltage and mobility of a driving transistor, threshold voltage of an organic light emitting diode, luminance of a subpixel, etc. .

Meanwhile, the timing controller 140 includes a vertical synchronization signal (Vsync), a horizontal synchronization signal (Hsync), an input data enable (DE) signal, a clock signal (CLK), and the like, together with the input image data. Receives various timing signals from the outside (eg host system).

The timing controller 140 converts the input image data input from the outside to suit the data signal format used by the data driver 120 and outputs the converted image data Data, as well as the data driver 120 and the gate. In order to control the driver 130, timing signals such as a vertical synchronization signal (Vsync), a horizontal synchronization signal (Hsync), an input DE signal, and a clock signal are input, and various control signals are generated to operate the data driver 120 and the gate output to the driver 130.

The organic light emitting display device 100 according to the present embodiments is an organic light emitting display device, and each subpixel SP includes an organic light emitting diode (OLED) and a device for driving the organic light emitting diode (OLED). It is composed of circuit elements such as a transistor (DRT: Driving Transistor) for

The type and number of circuit elements constituting each sub-pixel SP may be variously determined according to a provided function and a design method.

Meanwhile, in the organic light emitting display device 100, as the driving time of each subpixel SP increases, circuit elements such as the organic light emitting diode OLED and the driving transistor DRT deteriorate. Unique characteristic values (eg, threshold voltage, mobility, etc.) of circuit elements such as a diode (OLED) and a driving transistor (DRT) are changed.

The degree of change in characteristic values between circuit elements may be different from each other due to a difference in degree of deterioration between circuit elements.

Due to the deviation of characteristic values of the circuit elements, a luminance deviation between subpixels SP may occur. Accordingly, the luminance uniformity of the display panel 110 may be deteriorated, resulting in a deterioration in image quality.

Accordingly, the organic light emitting display device 100 according to the present exemplary embodiments may provide a “subpixel compensation function” that compensates for deviations in characteristic values of circuit elements between subpixels SPs.

In the organic light emitting display device 100 according to the present exemplary embodiments, each subpixel SP has a structure capable of sensing subpixel characteristic values and compensating for subpixel characteristic value deviations.

In addition, in order to provide a subpixel compensation function, the organic light emitting display device 100 according to the present embodiments uses a sensing configuration for sensing a subpixel characteristic value and a characteristic value deviation between each subpixel using a sensing result of the sensing configuration. A compensation configuration for compensating for may be included.

Here, the sub-pixel characteristic value may include, for example, characteristic values such as threshold voltage of the organic light emitting diode (OLED), threshold voltage of the driving transistor DRT, and characteristic values such as mobility. Below, the mobility of the driving transistor DRT is exemplified as a subpixel characteristic value.

FIG. 2 is an exemplary view showing the structure of pixels included in an organic light emitting display panel applied to the organic light emitting display device of FIG. 1 .

Referring to FIG. 2 , at least three subpixels SP form one unit pixel P:Pixel. In the following description, as shown in FIG. 2, four sub-pixels (SP), for example, a red pixel (R), a white pixel (W), a green pixel (G), and a blue pixel (B)) It is described as constituting one unit pixel P, but is not limited thereto. In this case, one sensing line RVL is disposed in one pixel P. Accordingly, when d data lines DL1 to DLd are disposed on a horizontal line of the organic light emitting display panel 110, the number k of the sensing lines RVL becomes d/4.

3 is a diagram illustrating each sub-pixel circuit of the organic light emitting display device 100 according to the present exemplary embodiments.

The subpixel as an example in FIG. 3 is an arbitrary subpixel supplied with the data voltage Vdata from the i-th data line (DLi, 1≤i≤m), and it is possible to sense the subpixel characteristic value and compensate for the deviation of the subpixel characteristic value. It is structured to make

Referring to FIG. 3 , each subpixel of the organic light emitting display device 100 according to the present exemplary embodiments includes an organic light emitting diode (OLED) and a driving circuit for driving the organic light emitting diode (OLED).

The driving circuit may include a driving transistor (DRT), a switching transistor (SWT), a sensing transistor (SENT), and a storage capacitor (Cst).

The driving transistor DRT drives the organic light emitting diode (OLED) by supplying a driving current to the organic light emitting diode (OLED). The driving transistor DRT may be connected between the organic light emitting diode OLED and the driving voltage line DVL supplying the driving voltage EVDD. The driving transistor DRT has a first node N1 corresponding to a source node or a drain node, a second node N2 corresponding to a gate node, and a third node N3 corresponding to a drain node or a source node. .

The switching transistor SWT is connected between the data line DLi and the second node N2 of the driving transistor DRT, and is turned on by receiving the scan signal SCAN through a gate node. The switching transistor SWT is turned on by the scan signal SCAN and transfers the data voltage Vdata supplied from the data line DLi to the second node N2 of the driving transistor DRT.

The sensing transistor SENT is connected between the first node N1 of the driving transistor DRT and the reference voltage line RVL for supplying the reference voltage VREF, and is a gate node that receives a sensing signal SENSE, which is a kind of scan signal. ) is authorized and turned on. The sensing transistor SENT is turned on by the sensing signal SENSE and applies the reference voltage VREF supplied through the reference voltage line RVL to the first node N1 of the driving transistor DRT.

The sensing transistor SENT may also serve as a sensing path so that the sensing configuration can sense the voltage of the first node N1 of the driving transistor DRT.

Meanwhile, the scan signal SCAN and the sensing signal SENSE may be respectively applied to the gate node of the switching transistor SWT and the gate node of the sensing transistor SENT through different gate lines.

In some cases, the same signal as the scan signal SCAN and the sensing signal SENSE may be respectively applied to the gate node of the switching transistor SWT and the gate node of the sensing transistor SENT through the same gate line.

4 is a diagram illustrating a subpixel compensation circuit of the organic light emitting display device 100 according to the present embodiments.

Referring to FIG. 4 , the organic light emitting display device 100 according to the present exemplary embodiments includes a sensing unit 310 for sensing subpixel characteristic values and a memory 320 storing sensing results of the sensing unit 310 and , a compensation unit 330 for compensating for deviations in sub-pixel characteristic values.

Here, as an example, the sensing unit 310 may be included in the data driver 120 and the compensating unit 330 may be included in the timing controller 140 .

In the organic light emitting display device 100 according to the present embodiments, in order to control sensing driving, that is, the voltage application state of the first node N1 of the driving transistor DRT in the subpixel SP is a subpixel characteristic value. In order to control a state required for sensing, a switch SAM may be further included.

Through this switch SAM, one end Nc of the reference voltage line RVL may be connected to the reference voltage supply node Na or the node Nb of the sensing unit 310 .

Referring to FIG. 4 , the reference voltage line RVL is basically a line for supplying the reference voltage VREF to the first node N1 of the driving transistor DRT through the sensing transistor SENT.

Meanwhile, a line capacitor Cline is formed in the reference voltage line RVL, and the sensing unit 310 senses a voltage charged in the line capacitor Cline on the reference voltage line RVL at a necessary time. Therefore, below, the reference voltage line RVL is also described as a sensing line.

For example, one such reference voltage line RVL may be disposed in each subpixel column, or one in each of two or more subpixel columns.

For example, when one pixel is composed of four subpixels (red subpixel, white subpixel, green subpixel, and blue subpixel) as shown in FIG. 2, one pixel may be disposed in each pixel column. there is.

The sensing unit 310 includes a sensing line (sensing line (SSPL) electrically connected to a first node N1 of a driving transistor DRT in a sub-pixel on a sensing sub-pixel line (SSPL) where sensing is driven among a plurality of sub-pixel lines). The sensing process may be performed by sensing the voltage of RVL and outputting a sensed value.

The sensing unit 310 may sense a voltage charged in the line capacitor Cline on the sensing line RVL by a current flowing through the sensing line RVL.

Here, the voltage charged in the line capacitor Cline is the voltage of the sensing line RVL, and the first node N1 of the driving transistor DRT reflects the characteristic value (threshold voltage, mobility) component of the driving transistor DRT. ) represents the voltage of

During mobility sensing driving and sensing driving, the voltage of the first node N1 of the driving transistor DRT is stored in the line capacitor Cline, and the sensing unit 310 is connected to the first node N1 of the driving transistor DRT. ) is not directly sensed, but the charged voltage of the line capacitor Cline storing the voltage of the first node N1 of the driving transistor DRT is sensed, so when the sensing transistor SENT is turned off. Even in this case, the voltage of the first node N1 of the driving transistor DRT may be sensed.

Each subpixel may be driven to sense the threshold voltage of the driving transistor DRT or to sense the mobility of the driving transistor DRT. Accordingly, the sensing value sensed by the sensing unit 310 may be a sensing value for sensing the threshold voltage Vth of the driving transistor DRT or a sensing value for sensing the mobility of the driving transistor DRT. there is.

Each of the first node N1 and the second node N2 of the driving transistor DRT is initialized with the data voltage Vdata and the reference voltage VREF for driving the mobility sensing, and then the driving transistor DRT One node N1 is floated, and the voltage of the first node N1 of the driving transistor DRT rises.

In this case, the voltage rise rate (change amount of the voltage rise value with respect to time) represents the current capability of the driving transistor DRT, that is, the mobility. Accordingly, the voltage at the first node N1 of the driving transistor DRT rises more steeply as the current capability (mobility) of the driving transistor DRT increases.

As the voltage rises, the line capacitor Cline on the sensing line RVL is charged by the current flowing through the driving transistor DRT to the sensing line RVL. The sensing unit 310 senses the voltage Vsense charged in the line capacitor Cline on the sensing line RVL.

The memory 320 may store sensing values for each sensing subpixel line SSPL as many as a predetermined number N of sensing subpixel lines. Depending on the available capacity of the memory 320, the predetermined number N of sensing subpixel lines may be the same as the number of all subpixel lines present in the display panel 110, and may be less than the number of all subpixel lines. may be

The compensator 330 may determine the characteristic values (eg, threshold voltage, mobility) of the driving transistor DRT in the corresponding subpixel based on the sensed value stored in the memory 320 and perform a characteristic value compensation process. Here, the characteristic value compensation process may include a mobility compensation process for compensating for the mobility of the driving transistor DRT.

The mobility compensation process may include a process of calculating a compensation value for compensating the mobility, storing the calculated compensation value in the memory 320, or changing corresponding image data (Data) with the calculated compensation value. .

The compensator 330 may change image data Data through mobility compensation processing and supply the changed data to the data driver 120 .

At this time, the digital-to-analog converter (DAC: Digital Analog Converter, 300) in the data driver 120 converts the analog voltage into a data voltage (Vdata) and supplies it to the corresponding subpixel, thereby compensating for the characteristic value (threshold voltage compensation, mobility) compensation) is actually applied.

Through the compensator 330 described above, a characteristic value of a driving transistor may be compensated to reduce or prevent a luminance deviation between subpixels.

Hereinafter, a principle of sensing the mobility of the driving transistor DRT in order to compensate for a mobility deviation between the driving transistors DRT will be briefly described with reference to FIG. 5 .

The above-described sensing unit 310 may be implemented by including an analog digital converter (ADC) that converts an analog voltage value into a digital value.

5 is a diagram for explaining a mobility sensing principle of the driving transistor DRT of the organic light emitting display device 100 according to the present embodiments.

Referring to FIG. 5, the mobility sensing principle for the driving transistor DRT is simply described. A voltage obtained by adding a constant voltage Vth_comp to the data voltage Vdata at the gate node N2 of the driving transistor DRT is applied to the gate node N2 of the driving transistor DRT. authorize it Here, the constant voltage (Vth_comp) is a voltage corresponding to the threshold voltage compensation value.

In this way, the current capability (i.e., mobility) of the driving transistor DRT can be relatively determined through the amount of voltage (ΔV) charged in the line capacitor Cline for a certain period of time, and through this, correction for compensation can be made. Rescue Gain.

This mobility sensing is characterized in that the sensing speed is fast because the driving transistor DRT is basically turned on. Accordingly, the mobility sensing mode is also referred to as a fast mode (F-Mode).

The aforementioned mobility compensation through mobility sensing may be performed by consuming a certain amount of time when the screen is driven. In this way, it is possible to sense and compensate for parameters of the driving transistor DRT that vary in real time.

In the present embodiments, the sensing operation is a "sensing drive" that drives a corresponding subpixel so that the voltage of the first node N1 of the driving transistor DRT becomes a voltage state that can reflect the mobility of the driving transistor DRT. ", and the voltage of the first node N1 of the driving transistor DRT in which the sensing unit 310 reflects the mobility of the driving transistor DRT, that is, the line capacitor Cline on the sensing line RVL is charged A “sensing process” of sampling and measuring (sensing) the voltage may be included.

6 is a diagram illustrating timing of mobility sensing according to the present embodiments.

Since mobility sensing takes a relatively short time compared to threshold voltage sensing, it can be performed while the screen is being driven.

For example, as shown in FIG. 6 , mobility sensing may be performed for one or more sub-pixel lines during a blank time interval based on the vertical synchronization signal VSYNC. Of course, in consideration of the threshold voltage sensing time, the threshold voltage sensing may be performed for one or more sub-pixel lines during the blank time interval.

According to this mobility sensing, subpixels included in the corresponding subpixel line are driven (mobility sensing driven) for each blank time interval, and the sensing unit 310 performs sensing processing (voltage measurement and conversion processing) for each blank time interval. can be done

As described above, since sensing driving and sensing processing for mobility sensing are performed in the blank time interval, the mobility can be sensed without significantly affecting the screen display.

7 is an exemplary diagram illustrating sub-pixel lines in which mobility sensing for external compensation is performed in a general organic light emitting display device.

In FIG. 7 , point A represents one subpixel formed on a subpixel line where mobility sensing for external compensation is not performed, and point B is on a subpixel line where mobility sensing for external compensation is performed. Indicates any one sub-pixel that has been formed.

In addition, (a) of FIG. 7 shows the luminance at the point A, and (b) of FIG. 7 shows the luminance at the point B.

In the organic light emitting display device 100, mobility sensing for external compensation is generally performed in units of one sub-pixel line (scan line), and in particular, as shown in FIG. 6, between frames, vertical It is being done in blank time.

In this case, an image is not output during the vertical blank time in the sub-pixel line where the mobility sensing for external compensation is performed. Accordingly, a sub-pixel line in which mobility sensing for external compensation is performed is displayed as a dark line as shown in FIG. 7 . For example, since an image is not output from subpixels formed on a subpixel line where mobility sensing for external compensation is performed, the subpixel line has low luminance compared to other subpixel lines. .

More specifically, as shown in (b) of FIG. 7 , a period in which the subpixel does not emit light (no emission) occurs in a subpixel where sensing for external compensation is performed. In this case, the no emission period in which the organic light emitting diode does not emit light includes not only the period in which the mobility sensing is performed, but also the organic light emitting period after the mobility sensing period, as shown in FIG. A period (curved section) for charging the first electrode for light emitting diodes (OLEDs) is also included.

However, as shown in (a) of FIG. 7 , subpixels in which sensing for external compensation is not performed continuously emit light.

Accordingly, the luminance of the subpixel line on which mobility sensing for external compensation is performed is lower than the luminance of the subpixel line on which mobility sensing for external compensation is not performed. Accordingly, the sub-pixel line on which the mobility sensing for external compensation is performed is visible to the user's eyes.

As described above, even if mobility sensing is performed during the blank time period rather than the active time period corresponding to each frame display driving period, the subpixel line in which mobility sensing is performed during the active time period after sensing driving and sensing processing In , a corresponding subpixel does not emit light, and thus a subpixel line (sensing subpixel line) in which mobility sensing is performed may appear on the screen. This phenomenon is referred to as a "sensing subpixel line visibility phenomenon".

In order to alleviate the phenomenon of the line visibility of the sensing subpixels, when the blank time period is reached and the mobility sensing drive and sensing process proceed, the screen displayed in the active time period (i frame) prior to the mobility sensing drive and sensing process is moved. It is necessary to perform image recovery processing in order to ensure that the image is continuously displayed even in the next active time interval (i+1 frame) after sensing driving and sensing processing.

8 is an exemplary view illustrating a concept of performing an image recovery process to mitigate a phenomenon in which sensing subpixel lines are visible after mobility sensing in an organic light emitting display device according to an exemplary embodiment.

In the organic light emitting display device 100 according to an exemplary embodiment, when a blank time interval is reached and mobility sensing driving and sensing processing are performed in order to alleviate the visibility of sensing subpixel lines after mobility sensing, mobility sensing driving and sensing In order to ensure that the screen displayed in the previous active time interval (i frame) is continuously displayed in the next active time interval (i+1 frame) after the mobility sensing drive and the sensing process, an image recovery process is performed. carry out

To perform the image recovery process, the organic light emitting display device 100 according to an exemplary embodiment applies different recovery image data voltages to subpixels where mobility sensing for external compensation is performed according to the gray level of input image data during the recovery time period. supply to

After the sensing process, the data driver 120 may supply the recovery image data voltage to the second node of the driving transistor DRT for the next frame period (i+1 frame) after the sensing process.

The recovered image data voltage is calculated using various information calculated when the mobility sensing drive and sensing process for external compensation are actually executed in the manufacturing process of the display panel 110 or through various simulations. After that, it can be stored in the memory 320.

For example, the restored image data voltage may be calculated by considering at least one of a gray level of the input image data, a position of a sensing subpixel line, and a color. That is, since the restored image data voltage can be variously changed according to the gray level of the input image data, the position of the sensing subpixel line, and the color of the corresponding subpixel, it can be calculated by considering all of the above information.

At this time, the recovery video data voltage is the recovery voltage (image data in the previous active time period (normal driving data It may be a voltage obtained by adding a voltage corresponding to a value added to ).

Accordingly, the timing controller 140 according to the present embodiments, after the mobility sensing driving and sensing process for a specific subpixel during the blank time interval, image data (normal Recovery image data (also referred to as recovery driving data) obtained by adding the recovery voltage to driving data (also referred to as normal driving data) may be supplied to the corresponding subpixel.

According to the above-described mobility sensing driving and the image recovery process after the sensing process, the data driver 120, in the frame period (i frame) after the mobility sensing driving and sensing process, the second of the driving transistor DRT. The recovery video data voltage (an analog voltage obtained by converting the recovery video data (recovery driving data) into analog) is supplied to the second node N2.

The recovery voltage is calculated using various information calculated when mobility sensing for external compensation is actually executed during the manufacturing process of the display panel 110 or calculated through various simulations and stored in the memory 320. can be stored

For example, the recovery voltage may be calculated by considering at least one of a gray level of input image data, a position of a sensing subpixel line, and a color. That is, since the restored image data voltage can be variously changed according to the gray level of the input image data, the position of the sensing subpixel line, and the color of the corresponding subpixel, it can be calculated by considering all of the above information.

As described above, by performing an image recovery process after the mobility sensing driving and sensing process during the blank time period, it is possible to reduce a sense of screen difference between frames according to the mobility sensing driving and sensing process.

9 illustrates a difference in charging time of the first electrode and a difference in a non-emission area according to the gradation of input image data. 10 and 11 show the required compensation luminance for image recovery processing according to the low and high gradations of FIG. 9 .

Referring to FIG. 9 , since the current level is lower in sub-pixels that emit light with lower gradations (for example, 10 gradations from 0 to 255 gradations), the charging time of the first electrode becomes longer. That is, even if the recovery image data voltage is applied after the mobility sensing, the non-emission area becomes longer, and a phenomenon in which the sensing subpixel line is visible to the user's eyes may be intensified.

In FIG. 10, (a) shows the luminance distribution during normal driving with low grayscale input image data between two frames (frame i and frame i+1), and (b) moves in the blank time interval between the two frames. It also shows the luminance distribution at the time of sensing. The difference in luminance between them becomes the magnitude of required image luminance to be restored through image recovery processing. Accordingly, when the input image data is of a low gray level, as shown in FIG. 10 , the necessary compensation luminance to be restored through image recovery processing may be large.

Referring back to FIG. 9 , the charging time of the first electrode is shortened because the current level is higher in subpixels emitting light in a middle gray level (for example, 32 gray levels) or high gray levels (for example, 64 gray levels). That is, when the recovery image data voltage is applied after the mobility sensing, the non-emission area is shortened, and the visibility of the sensing subpixel line to the user's eyes can be weakened.

In FIG. 11, (a) shows the luminance distribution during normal driving with high-grayscale input image data between two frames (frame i and frame i+1), and (b) moves in the blank time interval between the two frames. It also shows the luminance distribution at the time of sensing. The difference in luminance between them becomes the magnitude of required image luminance to be restored through image recovery processing. Therefore, when the input image data has a low gray level, as shown in FIG. 11, the required compensation luminance to be restored through the image recovery process may be small.

Accordingly, the recovery image data voltage may be variously changed according to the gray level of the input image data. The sensing unit 310 may perform mobility sensing driving and sensing processing in the blank time section, and the data driver 120 may supply a recovery image data voltage in the blank time section. After the sensing process, the data driver 120 is the second node of the driving transistor DRT, and the recovery image data voltage is different according to the gradation of the image data of the subpixel during the frame period after the mobility sensing drive and sensing process. can supply

As shown in FIG. 8, the recovery image data voltage may be a voltage obtained by adding a different recovery voltage according to the gray level of the image data to the image data voltage supplied to the second node of the driving transistor DRT during the frame period before the sensing process. but not limited thereto. As shown in FIG. 8 , the recovery voltage for the input image data may be changed according to the gray level of the input image data.

Accordingly, the timing controller 140 according to the present embodiments, after the mobility sensing of a specific subpixel during the blank time period, changes the gradation of the image data (normal driving data) to the image data (normal driving data) in the previous active time period. According to , recovery image data (restoration drive data) added by a specific value corresponding to another recovery voltage may be supplied to the corresponding subpixel.

The recovery voltage for the input image data may be set in various ways according to the gray level of the input image data. For example, the gradation of the input image data may be divided into a specific number of remodeling ranges, and a recovery voltage may be determined for each remodeling area, or a different restoration voltage may be determined for each gradation.

For example, the gradation range of the input image data is largely divided into two low gradation ranges (hereinafter referred to as low gradations) and high gradation ranges (hereinafter referred to as high gradations), and the recovery image data voltage and Recovery image data voltages for input image data of high grayscale may be set differently. The recovery voltage for the image data of the low gray level may be greater than the recovery voltage for the image data of the high gray level.

12 is a flowchart of setting a recovery voltage by dividing the gradation of input image data into a specific number of remodeling ranges.

Referring to FIG. 12, it is determined whether the data voltage corresponding to the input image data is less than or equal to a specific voltage, for example, 3V (S1210).

If the data voltage corresponding to the input image data is 3V or less, the preset recovery voltage is raised (S1220). If the data voltage corresponding to the input image data is not 3V or less, that is, if it exceeds 3V, the preset recovery voltage is maintained (S1330).

Next, an image recovery process is performed by adding the recovery voltage set in step S1220 or step S1230 to the image data voltage supplied to the second node of the driving transistor DRT during the frame period before the mobility sensing drive and sensing process. time is applied (S1240).

In this case, the preset recovery voltage may be a specific voltage, for example, 0V, but is not limited thereto and may be a voltage greater than 0V. In other words, for the image data of high grayscale, only the image data voltage supplied to the second node of the driving transistor DRT during the frame period (i frame) before the mobility sensing driving and sensing process is applied as the recovery image data voltage, and For grayscale image data, a voltage obtained by adding the recovery voltage to the image data voltage supplied to the second node of the driving transistor DRT during the frame period (i frame) before the mobility sensing driving and sensing process is applied as the recovery image data voltage. can do.

13 is a timing diagram of driving and sensing the mobility of a driving transistor (DRT) in a sub-pixel of the organic light emitting display device 100 according to the present embodiments for image data of low grayscale, and processing of image recovery. 14 is a timing diagram of driving and sensing the mobility of a driving transistor (DRT) in a sub-pixel of the organic light emitting display device 100 according to the present embodiments for image data of high grayscale, and processing of image recovery.

As shown in FIGS. 13 and 14 , mobility sensing driving and sensing processing for low grayscale image data and high grayscale image data are the same.

Referring to FIGS. 4, 13, and 14, the mobility sensing driving and sensing process is performed by first initializing voltages of the N1 node (gate node) and the N2 node (source node or drain node) of the driving transistor DRT. STEP 1, a second step (STEP 2) of increasing the voltage of the N2 node of the driving transistor DRT by floating the N2 node of the driving transistor DRT, and the N2 node of the driving transistor DRT When the voltage of the node rises, a third step (STEP 3) of sensing the voltage of the N2 node of the driving transistor DRT at a specific point of time proceeds.

In the first step (STEP 1), the scan signal SCAN is applied to the gate node of the switching transistor SWT, so that the switching transistor SWT is turned on. Also, the sense signal SENSE is applied to the gate node of the sensing transistor SENT, so the sensing transistor SENT is turned on. In the first step (STEP 1), the data voltage Vdata supplied to the data line DL is applied to the N1 node of the driving transistor DRT through the turned-on switching transistor SWT.

In the first step (STEP 1), the first switch SPRE is turned on, and the reference voltage Vref is supplied to the reference voltage line RVL. The reference voltage VREF supplied to the reference voltage line RVL is applied to the N2 node of the driving transistor DRT through the turned-on sensing transistor SENT.

Therefore, in the first step (STEP 1), the N1 node (gate node) of the driving transistor DRT is initialized to the data voltage Vdata, and the N2 node (source node or drain node) of the driving transistor DRT is the reference It is initialized with voltage (VREF).

In the second step (STEP 2) following the first step (STEP 1), the scan signal (SCAN) is continuously applied to the gate node of the switching transistor (SWT), so that the switching transistor (SWT) maintains an on state. Also, since the sense signal SENSE is continuously applied to the gate node of the sensing transistor SENT, the sensing transistor SENT may also maintain an on state.

However, referring to FIGS. 2 and 3 , in the second step (STEP 2), the first switch SPRE is turned off and the reference voltage VREF is not supplied to the reference voltage line RVL. Accordingly, the N2 node of the driving transistor DRT is floated.

As the N2 node of the driving transistor DRT floats, the voltage at the N2 node of the driving transistor DRT starts to rise from the reference voltage Vref.

In the third step (STEP 3), the second switch SAM is turned on, and the reference voltage line RVL corresponding to the sensing line SL is connected to the sensing unit 310. Accordingly, the sensing unit 310 may sense the voltage of the reference voltage line RVL.

Referring to FIGS. 4, 13 and 14, the mobility sensing driving and sensing process is performed by applying a black data voltage to a corresponding subpixel to reset after the mobility sensing driving and sensing process of the driving transistor DRT. Step (STEP4) and a fifth step (STEP5) of applying a recovery image data voltage to the corresponding subpixel.

When high grayscale image data is input to the corresponding sub-pixel, as shown in FIG. 13, the second step of the driving transistor DRT during the frame period (i frame) before the sensing process with the recovery image data voltage in step 5 (STEP5). Only the video data voltage supplied to the node is applied.

When low grayscale image data is input to the corresponding sub-pixel, as shown in FIG. 14, the second step of the driving transistor DRT during the frame period (i frame) before the sensing process with the recovery image data voltage in step 5 (STEP5). A voltage obtained by adding a recovery voltage to the video data voltage supplied to the node is applied.

15 is an example illustrating a relationship between recovery voltages according to gray levels during image recovery processing after driving and sensing the mobility of a driving transistor (DRT) in a subpixel of an organic light emitting display device 100 according to the present embodiments. .

Referring to FIG. 15 , a recovery voltage from a recovery image data voltage applied during image recovery processing after driving and sensing the mobility of a driving transistor DRT in a subpixel of an organic light emitting display device 100 according to the present embodiments. is different for each gray level, and a recovery voltage for image data of a small gray level may be greater than a recovery voltage for image data of a relatively large gray level.

That is, the recovery voltage has a different value for each gray level, and the gray level and the recovery voltage may have an inversely proportional relationship. Accordingly, the recovery voltage for each gradation may be stored in the memory 320 and the recovery voltage according to the gradation of the input image data may be added as the recovery image data voltage. Instead of storing the recovery voltage for each gray level in the memory 320, the timing controller 140 may modulate the image data according to a predetermined rule, or the data driver 120 may receive analog data from the timing controller 140. When converting to voltage (Vdata), certain rules may be applied.

16 is a diagram illustrating a light emitting state for each sensing progress position during mobility sensing driving and sensing processing according to the present embodiments. 17 and 18 are diagrams showing differences in restored image data voltages for each gradation at each sensing location during image recovery processing.

Referring to FIG. 16 , the organic light emitting display device 100 according to the present embodiments drives an image for an i-frame during an active time period, and when a blank time period occurs, sensing driving and sensing processing are performed. After the blank time interval, video driving for the i+1 frame is performed during the next active time interval.

Before and after the sensing operation during the blank time interval, it is necessary to perform image recovery processing in order to reduce the screen difference between frames.

Accordingly, the timing controller 140 according to the present embodiments, after sensing is performed during the blank time interval, for image driving for the i+1 frame, image data (normal driving) in the previous active time interval for the i frame. Recovery image data (also referred to as recovery driving data) obtained by adding a recovery amount to data (also referred to as normal driving data) may be supplied to the corresponding subpixel.

Here, the recovery voltage to be added to the image data (normal driving data) in the previous active time interval according to the difference between the length of time for light emission with recovery driving data (Trcv) and the length of time for light emission with normal driving data (Tnrm). Size can be determined differently.

As shown in FIGS. 17 and 18, the greater the difference between the length of time for light emission with recovery driving data (Trcv) and the length of time for light emission with normal driving data (Tnrm), the higher the image data in the previous active time interval. The recovery voltage to be added to (normal driving data) can be reduced. The smaller the difference between the length of time for light emission with recovery driving data (Trcv) and the length of time for light emission with normal driving data (Tnrm), the greater the recovery voltage to be added to the image data (normal driving data) in the previous active time interval. can do.

Here, the recovery voltage may be in inverse proportion to the degree of difference between the length of time for light emission with recovery driving data (Trcv) and the length of time for light emission with normal driving data (Tnrm).

The smaller the difference, the larger the recovery voltage. That is, the smaller the difference is, the larger the recovery driving data is than the normal driving data.

The greater the difference, the smaller the recovery voltage. That is, as the difference increases, recovery driving data becomes identical to normal driving data.

In the case of sensing the sub-pixel line in the panel center area CA (Case 1), since the difference between the length of time for light emission with recovery driving data (Trcv) and the length of time for light emission with normal driving data (Tnrm) is small, As the recovery voltage increases, the recovery driving data has a larger data value than the normal driving data.

In the case of sensing the uppermost sub-pixel line in the panel upper area UA (Case 2), the length of time Trcv for emitting light with recovery drive data is very short compared to the length of time Tnrm for emitting light with normal drive data. , Since the difference between the length of time for light emission with recovery drive data (Trcv) and the length of time for light emission with normal drive data (Tnrm) is very large, the recovery voltage becomes very small, and normal drive data and recovery drive data are identical or can be almost identical.

In the case of sensing the lowermost sub-pixel line within the panel lower area UA (Case 3), the length of time for light emission with recovery drive data (Trcv) is very long compared to the length of time for light emission with normal drive data (Tnrm). That is, since the difference between the length of time for light emission with recovery drive data (Trcv) and the length of time for light emission with normal drive data (Tnrm) is very large, the recovery voltage becomes very small, and the normal drive data and recovery drive data may be identical or nearly identical.

In addition, even at the same location, as shown in FIG. 18, different recovery voltages are applied according to the gray level of the input image data. For example, even at the same location, the recovery voltage for low grayscale input image data may be greater than the recovery voltage for high grayscale input image data.

Accordingly, the above-described recovery voltage may be different according to the location of a corresponding subpixel. That is, the recovery voltage may be greater when at least one of the upper, middle, and lower ends of the organic light emitting display device is different from at least the other one, and has a low gray level rather than a high gray level.

19 is a flowchart of a method of driving an organic light emitting display device according to another exemplary embodiment.

1 and 19, a display panel 110 in which subpixels including organic light emitting diodes (OLEDs) and driving transistors (DRTs) for driving the organic light emitting diodes (OLEDs) are arranged in a matrix type, and display In the driving method 1900 of the organic light emitting display device 100 according to another embodiment including the data driver 120 connected to the top or bottom of the panel 110, the driving method is predetermined in the display panel 110. After the sensing processing step (S1910) of performing a sensing processing of outputting a sensed value by sensing characteristic values of subpixels on the sensing subpixel lines of a predetermined number of sensing subpixel lines in at least one or more partial areas, and the sensing processing, driving A recovery drive step of supplying different recovery image data voltages according to the gray level of the image data of the corresponding subpixel during the frame period after the sensing process to the second node of the transistor DRT.

In this case, as described above, the restored image data voltage may be a voltage obtained by adding a different recovery voltage according to the gray level of the image data to the image data voltage supplied to the second node of the driving transistor during the frame period before the sensing process.

In this case, a recovery voltage for the image data of a low gray level may be greater than a recovery voltage for the image data of a high gray level. Meanwhile, the recovery voltage may be different according to the position of the corresponding subpixel.

According to the present embodiments as described above, an organic light emitting display device capable of reducing the level visible to the user's eye of a sub-pixel line in which mobility sensing for an efficient panel defect detection method and real-time external compensation is performed, and Its driving method can be provided.

The above description and accompanying drawings are merely illustrative of the technical idea of the present invention, and those skilled in the art can combine the configuration within the scope not departing from the essential characteristics of the present invention. , various modifications and variations such as separation, substitution and alteration will be possible. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be construed according to the claims below, and all technical ideas within the equivalent range should be construed as being included in the scope of the present invention.

100: organic light emitting display device
110: display panel
120: data driver
130: gate driver
140: timing controller
310: sensing unit
320: memory
330: compensation unit

Claims (13)

a display panel in which subpixels including organic light emitting diodes and driving transistors for driving the organic light emitting diodes are arranged in a matrix type;
a data driver connected to the display panel; and
A sensing unit that performs sensing processing to output a threshold voltage or mobility sensing value of the driving transistor;
The data driver, after the sensing process, supplies different recovery image data voltages to the driving transistor according to the gray level of the image data of the corresponding subpixel during a frame period after the sensing process;
The restored image data voltage is a voltage obtained by adding the restored voltage according to the gray level of the image data to the image data voltage supplied to the driving transistor during the frame period before the sensing process. According to claim 1,
wherein the sensing unit performs the sensing process during a blank time period, and the data driver supplies the recovery image data voltage during the blank time period. According to claim 1,
A recovery voltage for the image data of low grayscale is greater than a recovery voltage for the image data of high grayscale. According to claim 1,
The recovery voltage is different for each gray level of the organic light emitting display device. According to claim 1,
An organic light emitting display device in which the recovery voltage is different according to a position or color of a corresponding subpixel. According to claim 1,
wherein the recovery voltage is different from at least one of the upper end, the middle part, and the lower end of the organic light emitting display device. According to claim 1,
The data driver supplies a black data voltage between the sensing process and recovery driving. According to claim 1,
The recovery voltage is inversely proportional to a difference between a length of time for emitting light with the recovery image data and a length of time for emitting light with the image data. According to claim 1,
wherein the recovery voltage divides the gradation of the image data into a plurality of gradation ranges, and has different recovery voltages for each of the gradation ranges. A method of driving an organic light emitting display device including a display panel in which subpixels including organic light emitting diodes and driving transistors for driving the organic light emitting diodes are arranged in a matrix type, and a data driver connected to the display panel, the method comprising:
Sensing processing of sensing characteristic values of subpixels on sensing subpixel lines of a predetermined number of sensing subpixel lines in at least one predetermined partial area of the display panel and outputting a threshold voltage or mobility sensing value of the driving transistor. a sensing processing step to be performed; and
After the sensing process, a recovery driving step of supplying, by the driving transistor, different recovery image data voltages according to the gray level of the image data of the corresponding subpixel during a frame period after the sensing process;
The recovery image data voltage is a voltage obtained by adding the recovery voltage according to the gray level of the image data to the image data voltage supplied to the driving transistor during the frame period before the sensing process. According to claim 10,
A method of driving an organic light emitting display device in which a recovery voltage for the image data of low grayscale is greater than a recovery voltage for the image data of high grayscale. According to claim 10,
A method of driving an organic light emitting display device in which the recovery voltage is different according to a position or color of a corresponding subpixel. According to claim 10,
wherein the recovery voltage divides the gradation of the image data into a plurality of gradation ranges, and has different recovery voltages for each of the gradation ranges.

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