KR20160018969A - Organic light emitting display device - Google Patents

Abstract

The present invention relates to an organic light emitting display device capable of improving the display quality by changing a positive bias temperature stress (PBTS) compensation voltage range according to driving time, and a driving method thereof.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic light emitting display device,

The present invention relates to an organic light emitting display device capable of improving display quality by changing a positive bias temperature stress (PBTS) compensation voltage range according to driving time.

The organic light emitting display device is attracting attention as a next generation display device because of its high response speed, low power consumption, high resolution, large screen realization and visibility.

1 is a view for explaining a pixel of an organic light emitting display device according to the related art to which an internal compensation method is applied.

Referring to FIG. 1, a plurality of pixels are arranged in a matrix form in a display panel (OLED panel) of an organic light emitting display device. Each of the plurality of pixels includes an organic light emitting diode (OLED) and a pixel circuit for emitting the organic light emitting diode. The pixel circuit includes a switching TFT ST1, a driving TFT DT, a capacitor Cst, and a sensing TFT ST2.

The switching TFT ST1 is switched in accordance with a gate driving signal (scan) supplied to the gate line GL. The data voltage Vdata to which the switching TFT ST1 is turned on and supplied to the data line DL is supplied to the driving TFT DT.

The driving TFT DT is switched in accordance with the data voltage Vdata supplied from the switching transistor ST1. And controls the data current Ioled flowing to the organic light emitting diode OLED by switching of the driving TFT DT. The driving power source EVDD is supplied to the power source line PL and the data current Ioled is applied to the organic light emitting diode OLED when the driving TFT DT is turned on.

The capacitor Cst is connected between the gate terminal and the source terminal of the driving TFT DT. The capacitor Cst stores a voltage corresponding to the threshold voltage Vth of the driving TFT DT.

The organic light emitting diode OLED is electrically connected between the source terminal of the driving TFT DT and the cathode power supply EVSS. The organic light emitting diode OLED emits light by the data current Ioled supplied from the driving TFT DT.

There is a problem that the threshold voltage Vth and the mobility characteristics of the driving TFT DT are different from pixel to pixel due to the non-uniformity of the manufacturing process of the TFT (thin film transistor). Accordingly, even when the same data voltage (Vdata) is applied to the driving TFT DT of each pixel in a general organic light emitting display device, there is a problem that a uniform image quality can not be realized due to a deviation of a current flowing through the organic light emitting diode OLED .

In order to solve such a problem, a sensing TFT (ST2) is formed in each pixel. The threshold voltage Vth and the mobility k of the driving TFT of each pixel are sensed using the sensing TFT ST2 and the threshold voltage Vth and the mobility k of the driving TFT are determined based on the sensed result ). Thus, the driving voltage (Vdata + Vth) obtained by adding the data voltage (Vdata) and the compensation voltage (Vth) according to the video signal is supplied to the gate of the driving TFT. Hereinafter, when describing the driving characteristics of the driving TFT in the description, the meaning of the driving characteristics should be interpreted to include the threshold voltage (Vth) and the mobility (k).

The organic light emitting display device according to the related art controls the size of the data current Ioled flowing from the first driving power source EVDD to the organic light emitting diode OLED using the switching of the driving TFT DT. Thus, the organic light emitting diode (OLED) of each pixel emits light to display an image.

FIG. 2 is a view showing a luminance deviation between all the pixels of the organic light emitting display device according to the related art.

Referring to FIG. 2, even if all the pixels are manufactured by the same manufacturing process, a luminance deviation may occur even if the same data voltage is supplied to all the pixels due to manufacturing variations of the organic light emitting diode (OLED) and the pixel circuits. Therefore, after the manufacture of the display panel is completed, the screen of the display panel is inspected before being released into the product to correct the blur defects for all the pixels.

However, as the composition time elapses, the threshold voltage of the driving TFT increases, and the compensation voltage range of each pixel changes. Thus, as the driving time elapses, the center value of the compensation voltage range of all the pixels shifts, which causes a problem in that the brightness varies between the pixels.

FIG. 3 and FIG. 4 are graphs illustrating the setting of the positive bias temperature stress (PBTS) compensation voltage range among the driving voltages of the organic light emitting display device according to the related art. FIG. 3 shows a problem in the case where the PBTS compensation voltage range is set to be small, and FIG. 4 shows a problem in the case where the PBTS compensation voltage range is set large.

Referring to FIGS. 3 and 4, the data driver generates a driving voltage for supplying a driving voltage to the display panel (OLED panel) in order to emit the OLED formed in each pixel. The driving voltage includes a black display voltage (Black) for displaying a black image, a negative bias temperature illumination stress (NBTIS) compensation voltage, a lower threshold value Vth_LSL of the threshold voltage, an initial compensation value? (-)), a data voltage for emitting an OLED, a mobility compensation voltage (a_comp), a positive bias temperature stress (PBTS) compensation voltage, and an amp margin.

3, when the entire range of the driving voltage is set to 20 V, the black display voltage Black is set to 0.50 V, the NBTIS compensation voltage range is set to 1.00 V, and the lower reference value of the threshold voltage Vth_LSL) is set to 1.00 V, the initial compensation value is set to 1.60 V, the data voltage range is set to 9.50 V, the mobility compensation voltage (a_comp) range is set to 1.80 V, and the PBTS compensation voltage range is set to 1.60 V, and the amp margin can be set to 2.00V.

Here, the PBTS compensation voltage range can be fixed to 1.60 V, and the data voltage range can be set to 9.50 V. Thus, when the PBTS compensation voltage range is fixed to a small value of 1.60 V, the data voltage range can be set relatively large, and the luminance of the display image can be increased. However, if the change in the driving characteristic of the driving TFT of the pixel deviates from the PBTS compensation voltage range due to the elapse of the driving time, the driving TFT of the pixel can not be normally compensated.

Meanwhile, as shown in FIG. 4, the PBTS compensation voltage range can be fixed to 3.33 V, and the data voltage range can be set to 8.00 V. Thus, when the PBTS compensation voltage range is fixed to a large value of 3.33 V, the data voltage range is set relatively small. At this time, the PBTS compensation voltage range can be set to be wide, so that the variation of the characteristics of the driving TFTs of all the pixels can be compensated, but the data voltage range is reduced and the brightness of the display image is lowered.

As described above, if the PBTS compensation voltage range is fixed to one value, it is impossible to satisfy both the compensation of the characteristic change of the driving TFT and the luminance quality of the image.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic light emitting display device and a method of driving the same that can prevent image distortion caused by driving time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic light emitting display device and a driving method thereof that can vary the PBTS compensation voltage range to compensate for a change in characteristics of a driving TFT and improve the luminance quality of an image, We will do it.

Other features and advantages of the invention will be set forth in the description which follows, or may be learned by those skilled in the art from the description and the claims.

According to an aspect of the present invention, there is provided an organic light emitting display device including: a display panel including a plurality of pixels including an organic light emitting diode and a pixel circuit for emitting light; A data driver for supplying a driving voltage to the pixel circuit and sensing a threshold voltage and a mobility of a driving TFT (Thin Film Transistor) included in the pixel circuit; And a timing controller for controlling a positive bias temperature stress (PBTS) compensation voltage range of the driving voltage based on a sensed threshold voltage and a mobility of the driving TFT, wherein the data driver controls the controlled PBTS compensation voltage range To generate the driving voltage.

The organic light emitting display device and the driving method thereof according to the embodiment of the present invention can improve or prevent the image distortion phenomenon caused by the luminance unevenness of the pixel.

The organic light emitting display device and the method of driving the same according to the embodiment of the present invention can vary the PBTS compensation voltage range and can compensate for the change in characteristics of the driving TFT and improve the luminance quality of the image, The technical problem is to provide.

The organic light emitting display device and the driving method thereof according to the embodiment of the present invention can extend the product use period by varying the compensation data according to the product situation.

Other features and effects of the present invention may be newly understood through the embodiments of the present invention in addition to the features and effects of the present invention mentioned above.

1 is a view for explaining a pixel of an organic light emitting display device according to the related art to which an internal compensation method is applied.
FIG. 2 is a view showing a luminance deviation between all the pixels of the organic light emitting display device according to the related art.
FIG. 3 and FIG. 4 are graphs illustrating the setting of the positive bias temperature stress (PBTS) compensation voltage range among the driving voltages of the organic light emitting display device according to the related art.
5 is a view schematically showing an organic light emitting display device according to an embodiment of the present invention.
6 is a diagram illustrating a data driver according to an embodiment of the present invention.
7 and 8 illustrate a method of driving an organic light emitting display according to a first embodiment of the present invention, and show a method of changing a range of a driving voltage.
9 and 10 illustrate a method of driving an organic light emitting display device according to a second embodiment of the present invention, and show another method of changing the range of the driving voltage.

It should be noted that, in the specification of the present invention, the same reference numerals as in the drawings denote the same elements, but they are numbered as much as possible even if they are shown in different drawings.

The meaning of the terms described herein should be understood as follows.

The word " first, "" second," and the like, used to distinguish one element from another, are to be understood to include plural representations unless the context clearly dictates otherwise. The scope of the right should not be limited by these terms.

It should be understood that the terms "comprises" or "having" does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

It should be understood that the term "at least one" includes all possible combinations from one or more related items. For example, the meaning of "at least one of the first item, the second item and the third item" means not only the first item, the second item or the third item, but also the second item and the second item among the first item, Means any combination of items that can be presented from more than one.

Hereinafter, preferred embodiments of the organic light emitting display device and the driving method thereof according to the present invention will be described in detail with reference to the drawings.

5 is a view schematically showing an organic light emitting display device according to an embodiment of the present invention.

Referring to FIG. 5, the organic light emitting display device according to the embodiment of the present invention includes a display panel 100 and a driving circuit for driving the display panel 100. The driving circuit unit includes a data driver 200, a gate driver 300, a timing controller 400, and a memory 500.

In the memory 500, compensation data for compensating characteristic deviations of the driving TFTs of all the pixels are stored based on the result of sensing the characteristics of the driving TFTs of all pixels after the manufacture of the display panel is completed.

The display panel 100 includes a plurality of gate lines GL, a plurality of sensing signal lines SL, a plurality of data lines DL, a plurality of driving power supply lines PL, a plurality of reference power supply lines RL, Of pixels.

The plurality of pixels includes an organic light emitting diode (OLED) and a pixel circuit (PC) for causing the organic light emitting diode (OLED) to emit light. The organic light emitting diode OLED emits light by the data current Ioled flowing from the first driving power source EVDD to the second driving power source EVSS through the driving TFT DT.

Each of the plurality of pixels P may be any one of a red pixel, a green pixel, a blue pixel, and a white pixel. One unit pixel for displaying one image may be an adjacent red pixel, a green pixel, and a blue pixel. As another example, the unit pixel may be composed of adjacent red pixels, green pixels, blue pixels, and white pixels.

The plurality of gate lines GL and the plurality of sensing signal lines SL may be formed in parallel in the first direction (e.g., the horizontal direction) in the display panel 100. At this time, a scan signal (scan, gate drive signal) is applied from the gate driver 300 to the gate line GL. A sensing signal sense is applied from the gate driver 300 to the sensing signal line SL.

The plurality of data lines DL may be formed in the display panel 100 in a second direction (e.g., vertical direction). The plurality of data lines DL may be formed to intersect the plurality of gate lines GL and the plurality of sensing signal lines SL. However, the present invention is not limited to this, and may be applied to a plurality of gate lines GL, a plurality of sensing signal lines SL, a plurality of data lines DL, a plurality of driving power supply lines PL, The orientation of the array can be changed.

A driving voltage Vd is supplied from the data driver 200 to the data line DL. Here, the driving voltage includes a data voltage (Vd) obtained by adding a compensation voltage (Vth, k) for compensating a characteristic change of the driving TFT to an initial data voltage (Vdata) according to a video signal. That is, the data voltage Vd has a voltage level to which a compensation voltage corresponding to a characteristic change (threshold voltage / mobility) of the driving TFT DT is added to an initial data voltage Vdata of the pixel P.

Here, the driving voltage SVDD includes voltages other than the data voltage Vd. The driving voltage will be described in detail with reference to FIGS. 7 to 10. FIG.

The display reference voltage Vpre_r or the sensing precharging voltage Vpre_s may be selectively supplied to the reference power line RL from the data driver 200. [ At this time, the display reference voltage Vpre_r is supplied to each reference power supply line RL during a data charging period of each pixel P. The sensing precharging voltage Vpre_s may be supplied to the reference power supply line RL in the detection period for detecting the threshold voltage / mobility of the driving TFT DT of each pixel P. [ The first driving power source EVDD is supplied to the pixel P through the plurality of driving power supply lines PL.

The sensing of the characteristics (threshold voltage / mobility) of the driving TFT and the compensation of the characteristic change of the driving TFT are performed in real time at the power-on time at which the power of the OLED display device is turned on, Or at the power-off time at which the power of the organic light emitting display device is turned off, or may be selectively performed.

6 is a diagram illustrating a data driver according to an embodiment of the present invention.

Referring to FIG. 6, the data driver 200 includes an analog-to-digital converter (ADC) and a digital-analog converter (DAC).

In the display period, the digital image data is converted into an analog data voltage using a DAC and supplied to the pixel. Then, the value obtained by sensing the threshold voltage and the mobility from the driving TFT (not shown) is converted into a digital value through the ADC formed in the data driver, and the digitalized sensing value is supplied to a timing controller do.

When the sensing voltage value sensing the characteristic of the driving TFT by using the ADC is less than 3V, the sensing voltage value is supplied to the timing controller, and compensation data is generated based on the sensing voltage value.

On the other hand, the timing controller changes the voltage range of the ADC from 3V to 6V when the sensing voltage value sensing the characteristics of the driving TFT is larger than 3V. Thereafter, the sensing voltage range of the ADC is changed from 3V to 6V, and the characteristics of the driving TFT are sensed again.

Thereafter, the value obtained by sensing the threshold voltage and the mobility from the driving TFT (not shown) is converted into a digital value through the ADC, and the digitalized sensing value is supplied to the timing controller and reflected in the compensation data.

At the beginning of the driving of the organic light emitting display device, since the degree of the characteristic change of the driving TFT is small, the sensing voltage range of the ADC is set to 3V to sense the characteristic change of the driving TFT. do. After the elapse of the driving time, since the degree of characteristic change of the driving TFT is large, the sensing voltage range of the ADC is increased to 6V to sense the characteristic change of the driving TFT. That is, it is possible to increase the ADC sensing voltage range from the initially set 3V to 6V by reflecting the increase in the characteristic change of the driving TFT according to the elapsed driving time. By increasing the ADC sensing voltage range from 3V to 6V, the characteristics of the driving TFT can be accurately sensed even if the characteristics of the driving TFT are greatly changed.

Here, the sensing voltage range of the ADC is not necessarily set to 3V or 6V, and the sensing voltage range of the ADC may vary depending on the size and characteristics of the display panel.

7 and 8 illustrate a method of driving an organic light emitting display according to a first embodiment of the present invention, and show a method of changing a range of a driving voltage.

First, referring to FIG. 7, the data driver 200 generates a driving voltage to supply a driving voltage to a display panel (OLED panel) in order to emit light of an OLED formed in each pixel. The drive voltage is determined by the black display voltage Black, the NBTIS (Negative Bias Temperature Illumination Stress) compensation voltage, the threshold voltage lower reference value Vth_LSL, the initial compensation values? _Init (+ A mobility compensation voltage a_comp, a positive bias temperature stress (PBTS) compensation voltage, and an amp margin. The range of the driving voltage is determined by the output voltage range of the data driver 200. In the present invention, the range of the driving voltage may be 18V to 25V including the amp margin.

The black display voltage black means a voltage for displaying a black image, and a minimum voltage is set for displaying a black image.

The NBTIS compensation voltage range is set based on the measurement of the NBTS (Negative Bias Temperature Stress) while the TFT is irradiated with light. The threshold voltage of the driving TFT shifts in the negative direction during the initial driving of the display device To compensate for the characteristics.

In FIG. 7, two NBTIS compensation voltage ranges are shown. The first NBTIS compensation voltage range is for compensating the threshold voltage of the driving TFT during initial driving using the reference voltage Vref. The second NBTIS compensation voltage range is for compensating the threshold voltage of the driving TFT using the data voltage (Vdata).

The lower reference value Vth_LSL of the threshold voltage is set to the lower limit value of the region below the median of the threshold voltage.

The initial compensation values? _Init (+) and? _Init (-) compensate the characteristic deviation of the driving TFTs of all the pixels based on the result of sensing the characteristics of the driving TFTs of all the pixels after the manufacture of the display panel is completed .

A voltage range for adjusting the luminance of the OLED in the data voltage range (Vdata) is set, and a_comp is a value that sets the mobility compensation voltage range.

The degradation of the driving TFT proceeds according to the driving time and the threshold voltage is increased. When the PBTS compensation voltage range is fixed to a constant value, pixels which can not be compensated are generated. In order to solve such a problem, the present invention gradually increases the PBTS compensation voltage range as the driving TFT deteriorates according to the driving time and the threshold voltage increases.

The organic light emitting display device according to the first embodiment of the present invention can set the driving voltage range to X [V] (for example, 18 [V] to 25 [V]). Here, the range of the driving voltage is constant regardless of the driving time, but the voltage range of some of the configurations included in the driving voltage is set differently at the first point of time at which the driving is started and at the second point in time when the driving is performed for a certain time.

In the first embodiment of the present invention, the black display voltage black, the NBTIS compensation voltage range, the threshold voltage lower reference value Vth_LSL, the initial compensation value? _Init (+),? _Init (- ) And the amplifier margin maintain a constant value regardless of the driving time. On the other hand, the data voltage range (Vdata), the mobility compensation voltage range (? _Comp), and the PBTS compensation voltage range in the range of the driving voltage vary in accordance with the driving time.

The black display voltage black, the NBTIS compensation voltage range, the lower reference value Vth_LSL of the threshold voltage, and the threshold voltage Vth_LSL are set within the 34 to 36% voltage range at the first time point of the drive start time when the drive voltage range is set to 20 [V] Set the initial compensation values (∮_init (+), ∮_init (-)) and the amplifier margin. Then, the data voltage range (Vdata), the mobility compensation voltage range (? _Comp), and the PBTS compensation voltage range are set within the voltage range of 64 to 66%.

As described above, since the degree of the positive shift of the characteristics of the driving TFT formed in each pixel is small at the first time point of driving, the PBTS compensation voltage range is set to 7.0 to 9.0% in the entire driving voltage. Then, the data voltage range (Vdata) is set to 46.5 to 48.5% of the total driving voltage according to the set PBTS compensation voltage range.

Even if the PBTS compensation voltage range is set to a small value of 7.0 to 9.0% in the entire driving voltage, the characteristic change of the driving TFT of all the pixels can be sufficiently compensated at the first point in the initial stage of driving. Accordingly, it is possible to improve or prevent the occurrence of screen unevenness due to the luminance deviation of the pixels. The data voltage range (Vdata) can be set to 46.5 to 48.5% of the total driving voltage, so that an image can be displayed with a high luminance, and the display quality can be improved.

Subsequently, as the drive time elapses, the characteristic change of the driving TFT becomes severe. The timing controller controls the PBTS for compensating the shift of the threshold voltage at the second time point, which is driven for a predetermined time based on the sensing result of the driving TFT of all the pixels. Increase the compensation voltage range. At this time, the PBTS compensation voltage range is sequentially increased as the driving time elapses.

For example, after a certain period of driving, the PBTS compensation voltage range at the second time point is increased from 7.0 to 9.0% of the total driving voltage to 9.9 to 11.9%. As the PBTS compensation voltage range is increased, the data voltage range (Vdata) is decreased from 46.5 to 48.5% to 44.0 to 46.0%. At this time, the mobility compensation voltage range (? _Comp) is set to 9% of the total driving voltage at the first time point of the driving. The mobility compensation voltage range (? _Comp) can be reduced to 8.5 to 8.7% of the total driving voltage at the second time point at which the constant driving is performed.

Reducing the mobility compensation voltage range (α_comp) as well as the data voltage range (Vdata) together allows more precise control of the PBTS compensation voltage range and further increases the PBTS compensation voltage range.

The PBTS compensation voltage range is increased from 12.75 to 14.75%, which is 9.9 to 11.9% of the total driving voltage, at a third point in time after the drive time elapses from the second point in time. As the PBTS compensation voltage range is increased, the data voltage range (Vdata) is decreased from 44.0 to 46.0% to 41.5 to 43.5%. At this time, the compensation voltage range (? _Comp) which was 8.5 to 8.7% of the total driving voltage at the second time point can be reduced to 8.15 to 8.35% at the third time point.

The PBTS compensation voltage range is increased from 15.65 to 17.65%, which is 12.75 to 14.75% of the total driving voltage, at the fourth time point after the drive time elapses at the third time point. As the PBTS compensation voltage range is increased, the data voltage range (Vdata) of 41.5 ~ 43.5% is reduced to 39.0 ~ 41.0% of the total driving voltage. At this time, the compensation voltage range (? _Comp) which was 8.15 to 8.35% of the total driving voltage at the third time point can be reduced to 7.75 to 7.95% at the fourth time point.

Here, a value for increasing the PBTS compensation voltage range is set based on the sensing value of the characteristics of the driving TFT of all the pixels so as to compensate for the characteristic change of the driving TFT of all the pixels. Then, the data voltage range (Vdata) and the mobility compensation voltage range (? _Comp) are set based on the sensed values of the characteristics of the driving TFTs of all the pixels so as to compensate the change in the characteristics of the driving TFTs of all the pixels.

The PBTS compensation voltage range, the data voltage range (Vdata), and the mobility compensation voltage range (? _Comp) are varied according to the driving time. However, the black display voltage black, the NBTIS compensation voltage range, the threshold voltage lower reference value Vth_LSL, the initial compensation values? _Init (+),? _Init (-) and the amplifier margin are not changed.

The organic light emitting display device and the driving method thereof according to the first embodiment of the present invention increase the deterioration of the TFT as the driving time elapses and gradually increase the PBTS compensation voltage range as the threshold voltage increases. And, as the PBTS compensation voltage range increases, the data voltage range and the mobility compensation voltage decrease. Therefore, the entire range of the drive voltage supplied from the data driver is kept constant.

As the PBTS compensation voltage range increases, the data voltage range is reduced and the luminance is somewhat reduced. However, since the PBTS compensation voltage range is increased, all the pixels can be compensated, thereby preventing the screen unevenness due to the luminance deviation of each pixel. That is, even if the driving time has elapsed, the entire screen can be kept even, and the display quality can be improved.

In the present invention, an upper specification value (USL) and an under specification limit (LSL) are set based on a middle value among the compensation voltage ranges of a plurality of pixels.

Here, the pixels exceeding the upper reference value USL and the lower reference value LSL are very small in number among all the pixels, but in order to compensate for all the pixels that deviate from the upper reference value USL and the lower reference value LSL There is a burden to set the NBTIS compensation voltage range and the PBTS compensation voltage range to very large values.

In the present invention, a pixel which deviates from the upper reference value USL and the lower reference value LSL is darkened so that the pixels outside the upper reference value USL and the lower reference value LSL do not affect the PBTS compensation voltage range . For example, the upper reference value USL and the lower reference value LSL can be set to 0.90 V, and the pixels exceeding the upper reference value USL of 0.90 V and the lower reference value LSL of 0.90 V can be ignited .

Accordingly, it is possible to improve the problem that the NBTIS compensation voltage range and the PBTS compensation voltage range increase due to the pixels that deviate from the upper reference value USL and the lower reference value LSL.

Next, a specific driving method of varying the PBTS compensation voltage range will be described with reference to FIG.

When the power of the organic light emitting display device is turned on, the threshold voltage and the mobility of a driving TFT (Thin Film Transistor) of each pixel are sensed through the ADC of the data driver 200 (S10).

Then, characteristics of the driving TFTs of all the pixels are analyzed based on the threshold voltage and the sensing value of the mobility of each driving TFT (S11).

Thereafter, the PBTS compensation voltage range is controlled based on the characteristics of the entire driving TFT analyzed (S12). At this time, when the voltage range for compensating the deviation of the characteristics of the entire driving TFT is larger than the currently set PBTS compensation voltage range, the PBTS compensation voltage range is increased to a value capable of compensating for the deviation of the characteristics of the entire driving TFT.

Thereafter, the data voltage range is adjusted according to the increased PBTS compensation voltage range based on the sensing of the characteristics of the driving TFT (S13). At this time, the data voltage range can be reduced and the mobility compensation voltage range can also be reduced.

Thereafter, the image data is converted into a data voltage according to the data voltage range adjusted in S13 and supplied to each pixel. At this time, the digital data is converted into an analog data voltage using the RGB gamma (Gamma) generated according to each color of R, G and B (S14).

Thereafter, the driver IC (D-IC) outputs the data voltage to each pixel to display an image (S15).

9 and 10 illustrate a method of driving an organic light emitting display device according to a second embodiment of the present invention, and show another method of changing the range of the driving voltage.

First, referring to FIG. 9, the data driver 200 generates a driving voltage to supply a driving voltage to a display panel (OLED panel) to emit light of an OLED formed in each pixel. The drive voltage is determined by the black display voltage Black, the NBTIS (Negative Bias Temperature Illumination Stress) compensation voltage, the threshold voltage lower reference value Vth_LSL, the initial compensation values? _Init (+ A mobility compensation voltage a_comp, a positive bias temperature stress (PBTS) compensation voltage, and an amp margin.

The degradation of the driving TFT proceeds according to the driving time and the threshold voltage is increased. When the PBTS compensation voltage range is fixed to a constant value, pixels which can not be compensated are generated. In order to solve such a problem, the present invention gradually increases the PBTS compensation voltage range as the driving TFT deteriorates according to the driving time and the threshold voltage increases.

In the second embodiment of the present invention, the black display voltage black, the NBTIS compensation voltage range, the threshold voltage lower reference value Vth_LSL, the initial compensation values? _Init (+),? _Init (- ) And the amplifier margin maintain a constant value regardless of the driving time. On the other hand, the data voltage range (Vdata), the mobility compensation voltage range (? _Comp), and the PBTS compensation voltage range in the range of the driving voltage vary in accordance with the driving time.

The black display voltage black, the NBTIS compensation voltage range, the lower threshold value Vth_LSL of the threshold voltage, and the threshold voltage Vth_LSL are set within the 34 to 36% voltage range at the first time point of the drive start time when the drive voltage range is set to 20 [V] Set the initial compensation values (∮_init (+), ∮_init (-)) and the amplifier margin. Then, the data voltage range (Vdata), the mobility compensation voltage range (? _Comp), and the PBTS compensation voltage range are set within the voltage range of 64 to 66%.

As described above, since the degree of the positive shift of the characteristics of the driving TFT formed in each pixel is small at the first time point of the driving start, the PBTS compensation voltage range is set to a small value. Then, the data voltage range (Vdata) is set to a large value in accordance with the set PBTS compensation voltage range.

Even if the PBTS compensation voltage range is set to a small value of 7.0 to 9.0% in the entire driving voltage, the characteristic change of the driving TFT of all the pixels can be sufficiently compensated at the first point in the initial stage of driving. Accordingly, it is possible to improve or prevent the occurrence of screen unevenness due to the luminance deviation of the pixels. The data voltage range (Vdata) can be set to 46.5 to 48.5% of the total driving voltage, so that an image can be displayed with a high luminance, and the display quality can be improved.

Subsequently, as the drive time elapses, the characteristic change of the driving TFT becomes worse. At the second point in time, the PBTS compensation voltage range for compensating the shift of the threshold voltage is increased. At this time, the PBTS compensation voltage range is sequentially increased as the driving time elapses.

The NBTIS compensation voltage range is required at the first point of time of the initial driving, but the characteristic of the driving TFT is shifted in the positive direction at the second point of time in which the driving is performed for a predetermined time.

Therefore, the timing controller can reduce the NBTIS compensation voltage range or eliminate the NBTIS compensation voltage range at the second time point, which is driven for a predetermined time based on the sensing result of the driving TFT of all the pixels, To increase the PBTS compensation voltage range.

For example, at the second time point, the initially set NBTIS compensation voltage range is reduced from 1.00 [V] to 0.50 [V]. Then, as the two NBTIS compensation voltage ranges are reduced, the PBTS compensation voltage range is further increased by 1.00 [V]. That is, the PBTS compensation voltage range is increased by decreasing the NBTIS compensation voltage range.

If the PBTS compensation voltage range is to be further increased at a third time point after the driving time elapses from the second time point, the two NBTIS compensation voltage ranges reset at the second time point are changed from 0.50 V to 0 V ]. That is, the NBTIS compensation voltage range is eliminated. Then, at the third time point, the PBTS compensation voltage range is further increased by 1.00 [V] as the two NBTIS compensation voltage ranges are reduced. That is, the PBTS compensation voltage range is further increased by decreasing the NBTIS compensation voltage range.

If the PBTS compensation voltage range should be further increased at the fourth time point after the drive time has elapsed after removing the NBTIS compensation voltage range and increasing the PBTS compensation voltage range, increase the PBTS compensation voltage range and increase the data voltage range (Vdata ).

For example, increasing the PBTS compensation voltage range from 17.0% to 19.0% of the total drive voltage to 19.5% to 21.5%. Then, the data voltage range (Vdata) is reduced from 44.5% to 46.0%, which is 46.5% to 48.5% of the total driving voltage. At this time, the mobility compensation voltage range? _Comp can maintain the initially set voltage value. However, the present invention is not limited to this, and the data voltage range (Vdata) and the mobility compensation voltage range may be reduced together as the data voltage range (Vdata) increases. For example, the mobility compensation voltage range (? _Comp) set at 9% of the total driving voltage can be reduced to 8.5 to 8.7%.

The PBTS compensation voltage range is increased from 19.5 to 21.5% of the total driving voltage to 22.0 to 24.0% in the case of further increasing the PBTS compensation voltage range at the fifth time point after the driving time has elapsed since the fourth point in time. Then, the data voltage range (Vdata) is reduced from 41.0% to 46.5% of the total driving voltage to 41.5% to 43.5%. At this time, the mobility compensation voltage range? _Comp can maintain the initially set voltage value. However, the present invention is not limited to this, and the data voltage range (Vdata) and the mobility compensation voltage range may be reduced together as the data voltage range (Vdata) increases. For example, the compensation voltage range (? _Comp) which was 8.5 to 8.7% of the total driving voltage at the third time point can be reduced to 8.15 to 8.35% at the fourth time point.

Here, a value for increasing the PBTS compensation voltage range is set based on the sensing value of the characteristics of the driving TFT of all the pixels so as to compensate for the characteristic change of the driving TFT of all the pixels. Then, the data voltage range (Vdata) and the mobility compensation voltage range (? _Comp) can be set based on the sensed values of the characteristics of the driving TFTs of all the pixels so as to compensate the change in the characteristics of the driving TFTs of all the pixels.

However, the black display voltage black, the NBTIS compensation voltage range, the threshold voltage lower reference value Vth_LSL, the initial compensation values? _Init (+),? _Init (-) and the amplifier margin are not changed.

The organic light emitting display device and the driving method thereof according to the second embodiment of the present invention gradually increase the deterioration of the TFT and the PBTS compensation voltage range as the threshold voltage increases as the driving time elapses. And, as the PBTS compensation voltage range increases, the NBTIS compensation voltage range is first reduced. Thereafter, when the PBTS compensation voltage range is further increased, the data voltage range is reduced. At this time, the entire range of the driving voltage supplied from the data driver is kept constant.

By selectively reducing the data voltage range (Vdata) as well as the NBTIS compensation voltage range and mobility compensation voltage range (α_comp), the PBTS compensation voltage range can be controlled more precisely and the PBTS compensation voltage range can be further increased .

In the second embodiment of the present invention, when PBTS is increased according to the driving time, NBTIS required only at the initial driving time is first reduced to prevent occurrence of screen unevenness due to luminance deviation of the pixel without decreasing the luminance.

It also reduces the data voltage range and increases the PBTS compensation voltage range if the PBTS compensation voltage range needs to be further increased after removing NBTIS. As the PBTS compensation voltage range increases, the data voltage range is reduced and the luminance is somewhat reduced. However, since the PBTS compensation voltage range is increased, all the pixels can be compensated, thereby preventing the screen unevenness due to the luminance deviation of each pixel. That is, even if the driving time has elapsed, the entire screen can be kept even, and the display quality can be improved.

Next, a specific driving method of varying the PBTS compensation voltage range will be described with reference to FIG.

When the power of the organic light emitting display device is turned on, the threshold voltage and the mobility of a driving TFT (Thin Film Transistor) of each pixel are sensed through an ADC of the data driver 200 (S20).

Then, the characteristics of the driving TFTs of all the pixels are analyzed based on the threshold voltage and the sensing value of the mobility of each driving TFT (S21).

Then, it is determined whether to control the NBTIS compensation voltage range (S22). The characteristics of the driving TFTs of all the pixels are sensed and it is confirmed whether or not the PBTS compensation voltage range should be increased based on the characteristics of the entire driving TFTs analyzed. At this time, when the voltage range for compensating the deviation of the characteristics of the entire driving TFT is larger than the currently set PBTS compensation voltage range, the PBTS compensation voltage range should be increased to a value that can compensate for the deviation of the characteristics of the entire driving TFT. In this case, the NBTIS compensation voltage range is controlled.

Thereafter, the NBTIS compensation voltage range is decreased and the PBTS compensation voltage range is increased by decreasing the NBTIS compensation voltage range (S23).

Then, it is determined whether to control the data voltage range (S24). The characteristics of the driving TFTs of all the pixels are sensed and it is confirmed whether or not the PBTS compensation voltage range should be further increased based on the characteristics of the entire driving TFTs analyzed. At this time, when the voltage range for compensating the deviation of the characteristics of the entire driving TFT is larger than the currently set PBTS compensation voltage range, the PBTS compensation voltage range should be increased to a value that can compensate for the deviation of the characteristics of the entire driving TFT. In this case, the data voltage range is additionally controlled (S25). At this time, the PBTS compensation voltage range is increased and the data voltage range is decreased to a value capable of compensating for the deviation of the characteristics of the entire driving TFT.

Thereafter, the image data is converted into a data voltage according to the data voltage range adjusted in S25 and supplied to each pixel. At this time, the digital data is converted into an analog type data voltage by using the RGB gamma (Gamma) generated according to each color of R, G and B (S26).

Thereafter, the driver IC (D-IC) outputs the data voltage to each pixel to display an image (S27).

As described above, the organic light emitting display device and the driving method thereof according to the embodiment of the present invention can cope with the threshold voltage increasing actively by varying the compensation voltage range over time, Can be improved and the lifetime can be increased.

Since the prior art fixes the PBTS compensation voltage range to a small value or a large value, the driving voltage of the driving TFT of the pixel whose data voltage range is large but out of the PBTS compensation voltage range can not be compensated or the PBTS compensation voltage range can be set wide, There is a problem that the brightness of the image is lowered. The organic light emitting display device and the driving method thereof according to the present invention can control the PBTS compensation voltage range according to an increasing threshold voltage.

In addition, the organic light emitting display device and the driving method thereof according to the embodiment of the present invention can eliminate or prevent the smear occurring due to the deviation from the compensation voltage range, thereby improving or preventing the image distortion phenomenon caused by the luminance unevenness of the OLED pixel.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

100: display panel 200: data driver
300: Gate driver 400: Timing controller
500: Memory

Claims (7)

A display panel in which a plurality of pixels including an organic light emitting diode and a pixel circuit for emitting the organic light emitting diode are arranged;
A data driver for supplying a driving voltage to the pixel circuit and sensing a threshold voltage and a mobility of a driving TFT (Thin Film Transistor) included in the pixel circuit; And
And a timing controller for controlling a positive bias temperature stress (PBTS) compensation voltage range of the driving voltage based on a threshold voltage and a mobility of the sensing driving TFT,
Wherein the data driver generates the drive voltage based on the controlled PBTS compensation voltage range. The method according to claim 1,
Wherein the timing controller controls a data voltage range based on the PBTS compensation voltage range. The method according to claim 1,
Wherein the timing controller controls the mobility compensation voltage based on the PBTS compensation voltage range. The method according to claim 1,
Wherein the timing controller controls a voltage range of an ADC (Analog-Digital Converter) according to a sensing value of the driving TFT. The method according to claim 1,
Wherein the NBTIS (Negative Bias Temperature Illumination Stress) compensation voltage range is reduced by the PBTS compensation voltage range which is increased when the PBTS compensation voltage range is set. The method according to claim 1,
Wherein the NBTIS compensation voltage range is removed and the PBTS compensation voltage range is increased by the NBTIS compensation voltage range when the PBTS compensation voltage range is set. The method according to any one of claims 3, 5, and 6,
Wherein when the PBTS compensation voltage range is set, the data voltage range is decreased and the PBTS compensation voltage range is increased.

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