KR102156776B1 - Organic light emitting diode display device - Google Patents

Abstract

The present invention relates to an organic light emitting display device including a configuration for compensating for a threshold voltage and electron mobility of a driving thin film transistor constituting each pixel.
According to an embodiment of the present invention, a timing controller receives a compensation control signal and controls the sensing controller and the pixel itself to sense electrical characteristics of a pixel in parallel in response to the compensation control signal.
Accordingly, the present invention compensates for the shortcomings of the two compensation methods and simplifies the pixel structure by driving the organic light emitting display device by an external compensation method before or after shipment or according to other settings, and by mixing and driving an internal compensation method in other sections. Thus, there is an effect of realizing excellent compensation characteristics while realizing a high opening rate and high resolution.

Description

Organic light emitting display device {ORGANIC LIGHT EMITTING DIODE DISPLAY DEVICE}

The present invention relates to an organic light-emitting display device, and more particularly, to an organic light-emitting display device including a configuration for compensating for a threshold voltage and electron mobility of a driving thin film transistor constituting each pixel.

As a flat panel display to replace the existing cathode ray tube display, Liquid Crystal Display, Field Emission Display, and Plasma Display Panel ) And organic light-emitting display devices (Organic Light-Emitting Diode Display, OLED Display).

Among them, the organic light emitting diode provided in the organic light emitting display device has high luminance and low operating voltage characteristics, and is a self-luminous type that emits light by itself, so it has a large contrast ratio, and it is easy to implement an ultra-thin display. . In addition, there is an advantage that it is easy to implement a moving image with a response time of several microseconds (µs), there is no limit on the viewing angle, and is stable even at low temperatures.

1 is a diagram showing an equivalent circuit diagram of one pixel of a conventional organic light emitting display device.

As shown, the organic light emitting display device includes a display panel in which a plurality of pixels PX are defined, and wires to which the scan signal Scan and the signal Vdata are input are cross formed in a matrix form. And, a wiring for supplying the power voltage ELVDD is formed, spaced apart from this by a predetermined interval, and one pixel PX is defined at the intersection.

In addition, the pixel PX is a scan thin film transistor (SC-TFT) that applies a data voltage (Vdata) to the first node (N1) in response to the scan signal (Scan), and a driving voltage (ELVDD) is applied to one electrode. A driving thin film transistor (DR-TFT) that applies a drain current to the organic light emitting diode (EL) according to a voltage applied to the first node (N1), and a gate electrode of the driving thin film transistor (DR-TFT). It includes a capacitor C1 that maintains the voltage for one frame.

In the organic light emitting display device having such a structure, in particular, the driving thin film transistor (DR-TFT) controls the amount of current flowing through the organic light emitting diode (EL) to display the gradation of an image, and plays an important role in image quality.

However, even within one display panel, a variation in electrical characteristics of the driving thin film transistor between pixels, that is, a variation in threshold voltage (Vth) and electron mobility, occurs, and the current flowing through each organic light emitting diode is not constant. There is a problem in that gradation cannot be realized.

In order to solve this problem, a structure for compensating the threshold voltage and electron mobility of the driving thin film transistor inside or outside the pixel has been proposed. However, in the internal compensation method, a plurality of thin film transistors for sensing the characteristics of the driving thin film transistor are usually required in one pixel, so that the pixel structure is complex and the aperture ratio is reduced, and mobility compensation is difficult, and the external compensation method. In the case of, there is a disadvantage in that the sensing time is delayed because the characteristic of the driving thin film transistor must be sensed for all pixels, and thus the load is high and it takes several tens to hundreds of times of the internal compensation. Accordingly, there is a problem that it is not easy to perform a sensing operation for all pixels during one frame.

The present invention was devised to solve the above-described problem, and two compensation methods while compensating for the characteristic deviation of the driving thin film transistor by driving a pixel implemented with a minimum thin film transistor by hybridizing the internal and external compensation methods. An object of the present invention is to provide an organic light emitting display device that compensates for the disadvantages of.

In addition, another object of the present invention is to provide an organic light emitting display device that minimizes a threshold voltage compensation error due to a parasitic capacitance component of a pixel in an internal compensation method.

In order to achieve the above object, an organic light emitting display device according to a preferred embodiment of the present invention includes: a display panel in which a plurality of pixels are defined at a point where a scan line, a data line, and a sensing line cross; A gate driving unit and a data driving unit supplying a scan signal and a data voltage to the pixel through the scan line and the data line; A sensing control unit sensing electrical characteristics of the pixel; And controlling the gate driver, the data driver, and the sensing controller, controlling the sensing controller to sense the electrical characteristic at a first point in time according to a set compensation control signal, and controlling the pixel at a second point different from the first point in time. And a timing controller that controls itself to sense the electrical characteristics.
A pixel according to an exemplary embodiment includes an organic light emitting diode, a driving thin film transistor connected to a power supply line and driving the organic light emitting diode, and a scan connecting the data line and a first node of the driving thin film transistor by controlling the scan signal. A thin film transistor, a sensing thin film transistor connecting the sensing wiring and a second node of the driving thin film transistor by controlling a sensing signal, a capacitor connected between the first and second nodes, and the pixel is an initialization period, A threshold voltage sensing period of the driving thin film transistor, an electron mobility correction and a writing period of the driving thin film transistor, and an emission period are sequentially driven.
During the initialization period, the scanning thin film transistor and the sensing thin film transistor are turned on, applying an offset voltage supplied to the data line to the first node, and applying an initialization voltage of the sensing line to the second node And, during the threshold voltage sensing period, the scan thin film transistor is turned on to apply the offset voltage to the first node, and the sensing thin film transistor is turned off, so that the capacitor is turned on of the driving thin film transistor. A threshold voltage is sensed and stored, and during the electron mobility correction and writing period, the scan thin film transistor maintains turn-on, applies the data voltage supplied to the data wiring to the first node, and the sensing thin film The transistor is turned off, and the capacitor stores the offset voltage and the difference voltage of the voltage change amount according to the electron mobility in the sum of the data voltage and the threshold voltage. During the emission period, the scan thin film transistor and the The sensing thin film transistor is turned off, and the driving thin film transistor drives the organic light emitting diode according to the voltage stored in the capacitor.
The pixel according to an embodiment is an organic light emitting diode, a driving thin film transistor connected to a power supply line and driving the organic light emitting diode, and connecting the data line and a first node of the driving thin film transistor by controlling a first scan signal. A first scan thin film transistor, a second scan thin film transistor that applies an offset voltage to the first node under control of a second scan signal, and the sensing wiring and a second node of the driving thin film transistor are connected by control of a sensing signal. A sensing thin film transistor to be configured, and a capacitor connected between the first and second nodes, and the pixel is an initialization section, a threshold voltage sensing section of the driving thin film transistor, an electron mobility correction and writing section of the driving thin film transistor, It is driven sequentially in the order of the emission section.
During the initialization period, the first scan thin film transistor is turned off, and the second scan thin film transistor and the sensing thin film transistor are turned on to apply the offset voltage to the first node and the offset voltage to the second node. An initialization voltage of a sensing line is applied, and during the threshold voltage sensing period, the first scan thin film transistor is turned off and the second scan thin film transistor is turned on to apply the offset voltage to the first node. And, the sensing thin film transistor is turned off, the capacitor senses and stores the threshold voltage of the driving thin film transistor, and during the electron mobility correction and writing period, the first scan thin film transistor is turned on and the The data voltage of the data line is applied to a first node, and the second scan thin film transistor and the sensing thin film transistor are turned off, and the capacitor is added to the sum of the data voltage and the threshold voltage, the offset voltage and the electron transfer. It stores a voltage difference of the amount of change in voltage according to the degree, and during the emission period, the first and second scan thin film transistors and the sensing thin film transistors are turned off, and the driving thin film transistor is configured according to the voltage stored in the capacitor. It drives the organic light emitting diode.
The pixel according to an exemplary embodiment includes an organic light emitting diode, a driving thin film transistor connected to a power supply line and driving the organic light emitting diode, and applying an initialization voltage to a first node of the driving thin film transistor by controlling a first scan signal. 1 scan thin film transistor, a second scan thin film transistor that applies a data voltage to the first node under control of a second scan signal, and a capacitor connected between the first and second nodes, and the pixel is an initialization period , A first threshold voltage sensing section, a second threshold voltage sensing section, an electronic mobility correction and writing section, and an emission section in that order.

During the initialization period, the second scan thin film transistor is turned off, the first scan thin film transistor is turned on to apply the initialization voltage to the first node, and a low lower than the initialization voltage to the power wiring. The low-level power voltage is applied to the second node by applying a power voltage of a level, and during the first threshold voltage sensing period, the second scan thin film transistor is turned off, and the first scan thin film transistor is turned off. -By maintaining ON to apply the initialization voltage to the first node, and by applying a high-level power voltage to the power wiring, the capacitor is primarily sensed according to the threshold voltage of the driving thin film transistor and its sensing rate. The first voltage is stored, and during the second threshold voltage sensing period, the first and second scan thin film transistors are turned off, and the capacitor is the first voltage according to the threshold voltage of the driving thin film transistor and its sensing rate. The second voltage is increased from the first voltage and is secondarily sensed, and during the correction and writing period of the electron mobility, the first scan thin film transistor is turned off, and the first scan thin film transistor is turned on. The data voltage of the data line is applied to a first node, and the data voltage, the initialization voltage, the second voltage, and a voltage reflecting a voltage change amount according to the electron mobility are stored in the capacitor, and during the emission period, The first and second scan thin film transistors are turned off, and the driving thin film transistor drives the organic light emitting diode according to a voltage stored in the capacitor.

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The organic light emitting display device according to an embodiment of the present invention is driven by an external compensation method before or after shipment or by other settings, and is driven by mixing with an internal compensation method in other sections, thereby supplementing the disadvantages of the two compensation methods and having a pixel structure. It has the effect of implementing excellent compensation characteristics while realizing a high opening rate and high resolution due to its simplicity.

1 is a diagram showing an equivalent circuit diagram of one pixel of a conventional organic light emitting display device.
2 is a diagram schematically illustrating a structure of an organic light emitting display device according to an exemplary embodiment of the present invention.
3 is a diagram illustrating an equivalent circuit diagram of a pixel having a 3T1C structure of an organic light emitting display device according to an exemplary embodiment of the present invention.
4A and 4B are diagrams illustrating signal waveforms applied when sensing a threshold voltage (Vth) and electron mobility (μ) during external compensation of an organic light emitting display device according to an exemplary embodiment of the present invention.
5A to 5D are views for explaining an internal compensation drive according to an embodiment of the present invention.
6 is a diagram showing signal waveforms applied during internal compensation driving.
7A to 7C are views for explaining an internal compensation driving method after product shipment among driving methods of an organic light emitting display device according to an exemplary embodiment of the present invention.
8 is a diagram showing signal waveforms applied during internal compensation driving.
9 is a diagram showing an equivalent circuit diagram of a 3T1C structure pixel of an organic light emitting display device according to an exemplary embodiment of the present invention.
10A to 10D are diagrams for explaining internal compensation driving of an organic light emitting display device having a 4T1C structure pixel of the present invention.
11 is a diagram showing signal waveforms applied during internal compensation driving.
12 is a diagram illustrating selection modes of a compensation method for an organic light emitting display device according to an exemplary embodiment of the present invention.
13 is a diagram illustrating a pixel having a 4T1C structure in the organic light emitting display device according to the first exemplary embodiment of the present invention.
14 is an equivalent circuit diagram of one pixel of an organic light emitting display device according to a second exemplary embodiment of the present invention.
15A to 15E are views for explaining driving of an organic light emitting display device having a 3T1C structure pixel according to another embodiment of the present invention.
16 is a diagram illustrating signal waveforms applied when driving in the form shown in FIGS. 15A to 15D.
17A and 17B are views comparing threshold voltage (Vth) compensation characteristics of organic light emitting display devices according to the first and second exemplary embodiments of the present invention.

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

2 is a diagram schematically illustrating a structure of an organic light emitting display device according to a first embodiment of the present invention.

Referring to FIG. 2, the organic light emitting display device of the present invention includes a display panel 100 in which a plurality of pixels PX are defined, and various control units and driving units 110 to 140 connected to the display panel 100. do.

In the display panel 100, a plurality of scan lines (SCL) and data lines (DL) are formed so as to cross each other on an organic substrate or a plastic substrate, and scan lines (SCL) and data lines (DL) cross each other. Pixels PX displaying gray levels corresponding to red, green, and blue are defined. In addition, each of the pixels PX is connected to a sensing wiring SSL for sensing the threshold voltage Vth and the electron mobility μ, and although not shown, the power supply voltage ELVDD and the Various wires for supplying the ground voltage ELVSS may be further formed.

The scan line SCL is formed outside the display panel 100 and is connected to the scan driver 120 outputting a scan signal Vscan, and the data line DL is a data driver outputting a data voltage Vdata. It is connected to (130).

In addition, the sensing wiring SSL formed on the display panel 100 is connected to the sensing control unit 140 that senses electrical characteristics of the driving thin film transistor through a sink current flowing through the pixel PX. In the drawing, an example in which the sensing control unit 140 is configured as an external IC separate from the data driver 130 is shown, but a form in which an integrated IC in the data driver 130 is integrated may also be applied.

The pixels PX include an organic light emitting diode, a capacitor, a scanning thin film transistor, a sensing thin film transistor, and a driving thin film transistor. Here, the organic light emitting diode may include a first electrode (hole injection electrode), an organic compound layer, and a second electrode (electron injection electrode).

The timing control unit 110 receives image data applied from the outside and timing signals such as clock signals, vertical and horizontal synchronization signals, and receives gate control signals (GCS), data control signals (DCS), and sensing drive control signals (SCS). It generates a control signal such as. The timing control unit 110 is connected to an external system through a predetermined interface and receives the image-related signals and timing signals output therefrom at high speed without noise to generate the above control signals. The timing controller 110 may be integrated with the data driver 130 as an integrated IC according to the design intention of the organic light emitting display device.

In particular, the timing control unit 110 of the present invention controls the pixel PX itself to perform compensation for characteristic deviation according to the compensation control signal CC of the operator or user, or requests the sensing control unit 140 It may be controlled to perform compensation for a characteristic deviation of the pixel PX.

The scan driver 120 sequentially applies the scan signal Vscan to each pixel PX by one horizontal line unit in response to the scan control signal SCS from the timing controller 110. The scan driver 120 may be implemented as a conventional shift register.

The data driver 130 receives an image signal RGB of a digital waveform applied from the timing controller 110 and converts it into an analog voltage type data voltage Vdata having a grayscale value that can be processed by the pixel PX. In addition, the data voltage Vdata is supplied to each pixel PX through the data line DL in response to the input data control signal DCS.

The sensing control unit 140 controls the threshold voltage of the driving thin film transistor (DR-TFT) before product shipment of the organic light emitting display device, immediately after power on/off, or at a time designated by the user according to the control of the timing control unit 110. It senses the (Vth) and mobility characteristics in parallel with the external compensation method and the internal compensation method, and reflects the sensed result to the data voltage Vdata to compensate for the difference in characteristics of the driving thin film transistor (DR-TFT).

As an example, the output current value of the driving thin film transistor DR-TFT in the normal pixel PX reflects the threshold voltage and electron mobility characteristics of the driving thin film transistor. Accordingly, when deterioration occurs, the current value by the driving thin film transistor (DR-TFT) is changed, and the current is sinked to measure the fluctuation value of the threshold voltage and mobility. The sensing control unit 140 applies a precharge voltage to each pixel PX to the sensing line SSL, and sinks the current through the driving thin film transistor (DR-TFT) sensing line SSL based on the voltage. By reflecting the data voltage Vdata, a change in characteristics of the driving thin film transistor DR-TFT is compensated.

In particular, the organic light emitting display device according to an embodiment of the present invention is characterized in that it is driven in parallel at different times by applying both an internal compensation method and an external compensation method, and the first embodiment relates to a display device having a manufacturing process completed. This is a method of performing an external compensation step through a sensing control unit before product shipment to set the compensation value of the initial thin film transistor in advance, and performing an internal compensation step in real time as an internal compensation method when driving after shipment.

In particular, in an embodiment of the present invention, the sensing time of the threshold voltage during internal compensation is quite long, and thus, it is not suitable for a high-resolution and high-frequency organic electroluminescent display device, thus omitting the step of sensing the threshold voltage fluctuation value in the internal compensation step. And only sensing and compensating for the electronic mobility.

In addition, as a form of another embodiment, a method of selectively performing an internal compensation method and an external compensation method according to a user's setting may be applied, and in another embodiment, an external compensation method is performed by a separate event. The method may be applied. As an example, there may be a method of performing external compensation driving at a predetermined period according to a preset driving time, or performing internal compensation driving in real time and performing external compensation driving each time when the display device is powered on and off.

Hereinafter, a structure of one pixel constituting the organic light emitting display device of the present invention and a driving method of the organic light emitting display device according to embodiments of the present invention will be described with reference to the structure of one pixel.

3 is a diagram illustrating an equivalent circuit diagram of a pixel having a 3T1C structure of an organic light emitting display device according to an exemplary embodiment of the present invention.

Referring to FIG. 3, one pixel PX of the organic light emitting display device of the present invention has a 3T1C structure including three thin film transistors (SC-TFT, DR-TFT, SS-TFT) and one capacitor C1. As an organic light-emitting diode (EL), a driving thin film transistor (DR-TFT) supplying current thereto, and a data voltage (Vdata) is connected between the driving thin film transistor (DR-TFT) and a scan signal (Scan). The scan thin film transistor (SC-TFT) that applies the data voltage (Vdata) to the gate of the driving thin film transistor (DR-TFT) is connected between the sensing controller 140 and the driving thin film transistor (DR-TFT) to sense A sensing thin film transistor (SS-TFT) for sinking current by a driving thin film transistor (DR-TFT) according to a signal (Sense) and a capacitor (C1) connected between the gate and the source of the driving thin film transistor (DR-TFT) Includes.

In addition, the drain of the scan thin film transistor (SC-TFT) is connected to the output terminal of a digital-analog converter (DAC) built in a data driver (not shown), and the sensing circuit unit 140 precharges the sensing wiring. It includes a switch SWT, a sampling switch SPT for sampling the sink current, and an analog-to-digital converter (ADC). In the drawings, each thin film transistor is an example of an N-channel MOS FET type having an N-channel semiconductor layer, but may be replaced with a P-channel MOS FET type thin film transistor.

Hereinafter, a method of driving an organic light emitting display device according to an embodiment of the present invention will be described with reference to the illustrated signal waveform together with the equivalent circuit diagram of FIG. 3.

4A and 4B are diagrams illustrating signal waveforms applied when sensing a threshold voltage (Vth) and an electron mobility (μ) during external compensation of the organic light emitting display device according to the first embodiment of the present invention.

First, the threshold voltage sensing method will be described with reference to FIG. 4A. When a high-level scan signal scan and a precharging signal Spre are applied to the pixel PX, the scan thin film transistor SC-TFT is turned on. , The data voltage Vdata is applied to the gate of the driving transistor DR-TFT from the digital-analog converter DAC through the data line DL. In addition, the sensing line SSL is pre-charged to a predetermined level of the precharging voltage Vpre by the precharging switch Spre. Here, it may be a predetermined reference voltage level, which is the data voltage Vdata.

Next, the precharging signal Spre is applied at a low level to turn off the precharging switch Spre, and a high level sensing signal Sense is applied to turn on the sensing thin film transistor SS-TFT. Is done. Accordingly, the driving thin film transistor (DR-TFT) is driven in the saturation region according to the difference voltage between the data voltage (Vdata, reference voltage) stored in the capacitor C1 and the precharging voltage (Vpre), so that the sink current flows, The precharging voltage Vpre of the sensing wiring SSL rises to a voltage Vpre' corresponding to the saturation region. Thereafter, when the voltage Vpre' reaches the threshold voltage Vth of the driving thin film transistor DR-TFT, the sensing wiring SSL becomes saturated. At the point of saturation, the sensing signal (Sense) is applied at a low level and the sampling signal (Sam) is applied at a high level, and the sampling switch (Sam) is turned on, and the charged voltage (Vpre') is converted to analog-digital. The threshold voltage is sensed by sampling by the converter ADC.

Next, referring to the method of sensing the electron mobility (μ) with reference to FIG. 4B, a sensing signal (Sense) and a precharging signal (Spre) are applied at a high level to apply the sensing wiring (SSL) to a precharging voltage (Vpre). Then, the scan signal Scan is applied at a high level to apply the data voltage Vdata to the gate of the driving thin film transistor DR-TFT. Accordingly, the difference voltage between the data voltage Vdata and the precharging voltage Vpre is stored in the capacitor C1.

Thereafter, when the supply of the data voltage Vdata is stopped by applying the scan signal Scan at a low level, the driving thin film transistor DR-TFT is turned on by the difference voltage stored in the capacitor C1 and is proportional to it. Current is applied to the organic light emitting diode EL, and when the precharging signal Spre is applied at a low level after a predetermined period, the precharging voltage Vpre of the sensing wiring SSL is driven by the thin film transistor (DR-TFT). And as the sensing thin film transistor (SS-TFT) is charged, the voltage of the sensing wiring SSL increases.

At this time, the voltage change amount (ㅿV) of the sensing wiring (SSL) is the product of the current amount (i) and the time change amount (ㅿt) reflecting the electron mobility (μ) component of the driving thin film transistor (DR-TFT). It is the value obtained by dividing the capacitance (C) of (SSL), and therefore, the driving thin film transistor (DR-TFT) of the current pixel (PX) is compared with the voltage change amount (ㅿV') through the pixel as a preset reference. The change in electron mobility (μ) can be estimated.

Thereafter, the sensing thin film transistor (SS-TFT) is turned off, the sampling switch (SWT) is turned on, and the changed voltage level of the sensing wiring (SSL) is sampled through an analog-to-digital converter (ADC). The degree (μ) is sensed.

The threshold voltage (Vth) and electron mobility (μ) values sampled by the above method are stored in a separate memory, and the result is reflected in the data voltage (Vdata) by a compensation means preset in the sensing control unit. The external compensation drive is completed before shipment of the light emitting display device. That is, in the completed organic light emitting display device, the external compensation drive is performed once for the first time.

Thereafter, when the organic light emitting display device is driven after the product is shipped, internal compensation driving is performed in real time. 5A to 5D are views for explaining internal compensation driving according to an embodiment of the present invention, and FIG. 6 is a diagram illustrating signal waveforms applied during internal compensation driving.

Referring to FIGS. 5A and 6 together, in the initial step, first, a high-level sensing signal Sense is input to turn on the sensing thin film transistor SS-TFT, and the voltage of the second node N2 That is, the source voltage of the driving thin film transistor (DR-TFT) is discharged to the initialization voltage (Vini), and then the scan signal (Scan) is supplied at a high level to the data voltage (Vdata) of the horizontal line (N-1th) of the previous stage. Is applied to the gate of the first node N1, that is, the driving thin film transistor DR-TFT, and the driving thin film transistor DR-TFT is turned on with the gate voltage. Subsequently, when the data voltage Vdata is lowered to the offset voltage Vofs level, the first node voltage level becomes the offset voltage Vofs.

Next, referring to FIG. 5B, in the threshold voltage sensing section (Vth Sensing), when the sensing thin film transistor (SS-TFT) is turned off by applying the sensing signal (Sense) at a low level, the driving thin film transistor (DR-TFT) ), the voltage of the second node N2 rises from the offset voltage Vofs to the difference voltage of the threshold voltage Vth of the driving thin film transistor DR-TFT, and eventually the threshold voltage Vth is applied to the capacitor C1. ) Will be saved.

Next, referring to FIG. 5C, in the electronic mobility correction and writing section (μ compensation & writing), the first node N1 is applied by applying the grayscale to be displayed, that is, the data voltage Vdata of the corresponding horizontal line Nth. When the data voltage (Vdata) is raised to the voltage level, the second node (N2) is gradually charged according to the characteristics of the electron mobility (μ) of the driving thin film transistor (DR-TFT), and eventually, the capacitor (C1) is In the sum of the voltage Vdata and the threshold voltage Vth, the difference voltage between the offset voltage Vofs and the voltage change amount (ㅿV(μ)) according to the electron mobility is stored.

At this time, the voltage change amount (ㅿV(μ)) has a nonlinear proportional relationship between two thin film transistors with different electron mobility (μ), and flows through the two thin film transistors with different electron mobility (μ1, μ2). To make the currents (l1,l2) the same, the following equation 1,

ㅿV(μ,t) (voltage change according to time and electron mobility) must be set to satisfy.

Here, since ㅿV(μ,t)=I(t)*t/C (current amount over time * time/capacitor), the above equation is corrected for electron mobility and optimized time (t) in the writing section. It should be set so that 1 is satisfied.

In particular, as the data voltage (Vdata) corresponds to a low grayscale, the amount of current (I(t)) over time decreases exponentially. Therefore, when displaying a low grayscale image, the time (t ) Is set longer.

Next, referring to FIG. 5D, a scan signal (Scan) is applied at a low level to the emission section to turn off the scan thin film transistor (SC-TFT), and drive by the voltage level stored in the capacitor (C1). The thin film transistor DR-TFT applies a current Ioled whose threshold voltage Vth and electron mobility μ are corrected to the organic light emitting diode EL.

Accordingly, the organic light emitting display device according to an embodiment of the present invention is driven by the external compensation method before product shipment by the above-described method, and is driven by the internal compensation method in real time when driving after shipment.

Meanwhile, according to the above-described embodiment, when driving internal compensation after product shipment, a considerable amount of time is required in the threshold voltage (Vth) compensation section during one horizontal period (1H). By omitting this, only the electronic mobility correction is performed to achieve high resolution. And a high frequency organic light emitting display device.

7A to 7C are views for explaining an internal compensation driving method after product shipment among the driving methods of the organic light emitting display device according to the first embodiment of the present invention, and FIG. 8 is a diagram illustrating signal waveforms applied during internal compensation driving. It is a drawing showing.

Referring to FIGS. 7A and 8 together, in the initial step, first, a high-level sensing signal Sense is input to turn on the sensing thin film transistor SS-TFT, and the voltage of the second node N2 That is, the source voltage of the driving thin film transistor (DR-TFT) is discharged to the initialization voltage (Vini), and then the scan signal (Scan) is supplied at a high level to the data voltage (Vdata) of the horizontal line (N-1th) of the previous stage. Is applied to the gate of the first node N1, that is, the driving thin film transistor DR-TFT, and the driving thin film transistor DR-TFT is turned on with the gate voltage. Accordingly, the data voltage Vdata of the previous stage may be used as the offset voltage Vofs.

Next, referring to FIG. 7B, in the electronic mobility correction and writing section (μ compensation & writing), as the data voltage Vdata to be displayed is applied, the first node N1 is charged with the data voltage Vdata and sensed. When the sensing thin film transistor (SS-TFT) is turned off by applying a signal (Sense) at a low level, the second node (N2) gradually decreases according to the characteristics of the electron mobility (μ) of the driving thin film transistor (DR-TFT). As a result, the capacitor C1 stores the offset voltage Vofs in the data voltage Vdata and the difference voltage between the voltage change amount (ㅿV(μ)) according to the electron mobility.

Here, the voltage change amount (ㅿV(μ)) is set to satisfy the above equation.

Next, referring to FIG. 7C, a scan signal (Scan) is applied at a low level to the emission section to turn off the scan thin film transistor (SC-TFT), and is driven by the voltage level stored in the capacitor (C1). The current Ioled, whose electron mobility μ of the thin film transistor DR-TFT is corrected, is applied to the organic light emitting diode EL.

Accordingly, according to the present invention, the organic light emitting display device is driven by an external compensation method before product shipment by the above-described method, and when driving after shipment, it is driven by an internal compensation method in real time excluding the threshold voltage compensation section to display high resolution and high frequency. Application to the device is advantageous.

Meanwhile, in the above embodiment, an example of a pixel having a 3T1C structure including three thin film transistors has been described, but a structure that reduces driving time by supplying a separate reference voltage Vref is also applicable.

9 is a diagram showing an equivalent circuit diagram of a 3T1C structure pixel of an organic light emitting display device according to an exemplary embodiment of the present invention.

Referring to FIG. 9, one pixel PX of the organic light emitting display device of the present invention includes four thin film transistors (SC-TFT1, SC-TFT2, DR-TFT, SS-TFT) and one capacitor C1. As a 4T1C structure provided, it is connected between an organic light emitting diode (EL), a driving thin film transistor (DR-TFT) supplying current thereto, and a driving thin film transistor (DR-TFT) while receiving a data voltage (Vdata). 1 A reference voltage according to a first scan thin film transistor (SC-TFT1) applying a data voltage (Vdata) to the gate of a driving thin film transistor (DR-TFT) according to the scan signal (scan1) and a second scan signal (scan2) A second scan thin film transistor (SC-TFT2) that applies (Vref) to the gate of the driving thin film transistor (DR-TFT), and the sensing signal is connected between the sensing control unit 140 and the driving thin film transistor (DR-TFT). sense), and a sensing thin film transistor (SS-TFT) that sinks a current by a driving thin film transistor (DR-TFT) and a capacitor (C1) connected between the gate and the source of the driving thin film transistor (DR-TFT). .

In addition, the drain of the first scan thin film transistor (SC-TFT1) is connected to the output terminal of a digital-analog converter (DAC) built in the data driver (not shown), and the sensing circuit unit 140 is for precharging the sensing wiring. It includes a precharging switch (SWT), a sampling switch (SPT) for sampling sink current and an analog-to-digital converter (ADC).

In the organic light emitting display device having such a structure, in the external compensation drive before product shipment, the second scan signal Scan2 is always fixed to a low state, so that the threshold voltage and electron mobility compensation are performed in the same manner as in the above embodiment. In the internal compensation drive after product shipment, the driving time is shortened by supplying the reference voltage Vref to the second node N2 in the initialization and threshold voltage compensation section.

10A to 10D are diagrams for explaining internal compensation driving of the organic light emitting display device having a 4T1C structure pixel of the present invention, and FIG. 11 is a diagram illustrating signal waveforms applied during internal compensation driving.

Referring to FIGS. 10A and 11 together, in the initial step, first, a high-level sensing signal (Sense) and a second scan signal (Scan2) are input to provide a sensing thin film transistor (SS-TFT) and a second scan thin film. Turn-on the transistor SC-TFT and set the voltages of the first and second nodes N1 and N2, that is, the gate voltage and the source voltage of the driving thin film transistor DR-TFT, respectively, to the reference voltage Vref and the initialization voltage ( Vini). Accordingly, the reference voltage Vref is used as the offset voltage Vofs.

Accordingly, discharging to the offset voltage is performed faster than the conventional case where the data voltage Vdata of the previous stage N-1 th is used.

Next, referring to FIG. 10B, in the threshold voltage sensing period (Vth Sensing), when the sensing thin film transistor (SS-TFT) is turned off by applying the sensing signal (Sense) at a low level, the driving thin film transistor (DR-TFT) ), the voltage of the second node N2 rises from the offset voltage Vofs to the difference voltage of the threshold voltage Vth of the driving thin film transistor DR-TFT, and the threshold voltage Vth at the capacitor C1 Will be saved.

Subsequently, referring to FIG. 10C, in the electronic mobility correction and writing section (μ compensation & writing), as the first scan signal Scan1 is applied at a high level and the second scan signal Scan2 is applied at a low level, When the first node N1 is raised to the voltage level of the data voltage Vdata by applying the data voltage Vdata of the horizontal line Nth, the electron mobility of the driving thin film transistor DR-TFT (μ) The second node N2 is gradually charged according to the characteristics of, and as a result, the amount of change in voltage according to the offset voltage Vofs and the electron mobility in the sum of the data voltage Vdata and the threshold voltage Vth in the capacitor C1 The difference voltage of ㅿV(μ)) is stored. Here, the electron mobility is corrected by adjusting the correction time to optimize the voltage change amount (ㅿV(μ)).

Next, referring to FIG. 10D, the first scan signal Scan1 is applied at a low level to the emission section to turn off the first scan thin film transistor SC-TFT1, and the voltage stored in the capacitor C1 According to the level, the driving thin film transistor DR-TFT applies a current Ioled whose threshold voltage Vth and electron mobility μ are corrected to the organic light emitting diode EL.

Accordingly, the organic light emitting display device according to an embodiment of the present invention is driven by an external compensation method before product shipment by the above-described method, and is driven by a high-speed real-time internal compensation method when driven after shipment.

12 is a diagram illustrating selection modes of a compensation method for an organic light emitting display device according to a first embodiment of the present invention.

Referring to FIG. 12, in the first embodiment of the present invention, the external compensation driving and the internal compensation driving may be set in parallel based on whether a product is shipped. That is, before product shipment, the external compensation driving method including the threshold voltage sensing step, the electronic mobility sensing step, and the result value storage step is performed once for the first time, and after the product is shipped, the initialization step, threshold voltage sensing by reflecting the external compensation result. Step, an internal compensation driving method including an electronic mobility sensing step and a screen display step is performed (a).

In addition, the present invention may be set to perform external compensation driving and internal compensation driving in parallel according to an event occurring in a specific situation. As an example, an external compensation driving method including a threshold voltage sensing step, an electronic mobility sensing step, and a result value storage step is performed at the power-on and power-off times of the organic light emitting display device, and in normal operation, the external compensation result In reflection, an internal compensation driving method including an initialization step, a threshold voltage sensing step, an electronic mobility sensing step, and a screen display step is performed (b).

In addition, the external compensation driving and the internal compensation driving may be set in parallel according to the user setting, and may be set to selectively perform any one of a threshold voltage sensing step and an electronic movement sensing step in each compensation step. As an example, when the user selects the external compensation drive, only the threshold voltage sensing step and the result value storage step are performed, and when the internal compensation drive is selected, only the initialization step, the electronic mobility sensing step, and the image display step are performed. Can be (c).

In addition, as a driving method of the organic light emitting display device of the present invention, it may be set to alternately perform an external compensation step and an internal compensation step according to a preset period (d). As an example, if it is set to perform the external compensation step every 10 hours, the internal compensation step is performed in real time when the display device is driven, but when the accumulated driving time reaches 10 hours, the external compensation step is performed and then the internal compensation step is performed again. Can be set to perform.

On the other hand, in the internal compensation driving of the above-described first embodiments, when a low-gradation image is realized, an image imbalance occurs.

13 is a view showing a pixel of a 4T1C structure in the organic light emitting display device according to the first exemplary embodiment of the present invention. Referring to FIG. 12, a driving thin film transistor (DR-TFT) is commonly used in an exemplary embodiment of the present invention. The threshold voltage (Vth) is stored in the second node (N2) and then the threshold voltage (Vth) information is transmitted to the first node (N1) in the emission section. In this process, the parasitics of the first node (N1) The threshold voltage Vth transmitted by the parasite capacitance component is lowered.

The loss of the threshold voltage Vth due to the parasitic capacitance corresponds to Equation 2 below.

Here, Cpara is the parasitic capacitance of the first node N1, and Cstg is the capacitance of the capacitor C1.

The loss of the threshold voltage causes a relatively high difference in voltage Vgs between gate sources, especially in a low grayscale image, and causes an image quality imbalance with respect to the threshold voltage Vth. In addition, the compensation range of the threshold voltage Vth decreases, which reduces the yield of the pixel.

Hereinafter, a pixel structure and a driving method thereof of an organic light emitting display device having improved the threshold voltage loss problem according to a second embodiment of the present invention will be described with reference to the drawings.

14 is an equivalent circuit diagram of one pixel of an organic light emitting display device according to a second exemplary embodiment of the present invention.

Referring to FIG. 14, one pixel PX of the organic light emitting display device according to the second embodiment of the present invention includes three thin film transistors SC-TFT1, SC-TFT2, and DR-TFT, and one capacitor ( As a 3T1C structure having C1), an organic light emitting diode EL, a driving thin film transistor (DR-TFT) supplying current thereto, and an initialization voltage Vini are driven according to the first scan signal scan1. It is connected between the first scan thin film transistor (SC-TFT1) applied to the gate of the (DR-TFT) and the driving thin film transistor (DR-TFT) while receiving the data voltage (Vdata) to receive the second scan signal (scan2). Accordingly, the second scan thin film transistor SC-TFT2 applying the data voltage Vdata to the gate of the driving thin film transistor DR-TFT and the capacitor C1 connected between the gate and the source of the driving thin film transistor DR-TFT ).

This pixel structure is a structure for compensating the section in which the threshold voltage Vth is lost by subdividing the threshold voltage sensing section Vth into two stages after the initialization section. In particular, the driving thin film transistor (DR-TFT) The supplied power voltage ELVDD is output as an AC waveform AC, and a second threshold voltage sensing section is further included after the first threshold voltage sensing section.

15A to 15D are views for explaining driving of an organic light emitting display device having a 3T1C structure pixel according to another embodiment of the present invention, and FIG. 16 is a diagram illustrating driving in the form shown in FIGS. 15A to 15D. It is a diagram showing the applied signal waveform.

16 shows driving characteristics of two arbitrary pixels among the pixels of the organic light emitting display device, which are used to compensate for voltage loss due to the parasitic capacitance.

In the following description, the organic light emitting display device of the present invention includes an initial period, a first threshold voltage sensing period (1st Vth sensing), a second threshold voltage sensing period (2rd Vth sensing), and an electron mobility. It is driven through 5 steps of compensation and writing section (μ compensation & writing) and emission section (emission).

First, referring to FIGS. 15A and 16 together, in the initial period, the power supply voltage ELVDD is output at a low level for one horizontal period, and the first scan signal Scan1 is output at a high level to perform a first scan. The thin film transistor is turned on to charge the first node N1 with the initialization voltage Vini, and the second node N2 with the low-level power voltage ELVDD. At this time, the low-level power voltage ELVDD is at least a lower level than the initialization voltage Vini and is a negative (-) voltage.

Next, as a first threshold voltage sensing section (1st Vth Sensing), as the first and second scan signals Scan1 maintain high and low levels, respectively, the first node N1 is the initialization voltage Vini. Will be maintained. In addition, the power supply voltage ELVDD is output at a high level to flow a current through the driving thin film transistor DR-TFT to sense the threshold voltage Vth. Accordingly, a voltage of Vini-Vth×α is applied to the second node N2, and Vth×α, which is the difference between the two nodes N1 and N2, is charged to the capacitor C1. Here, α is a constant indicating a threshold voltage (Vth) sensing rate, and a larger value of α indicates a lower threshold voltage (Vth) sensing rate.

Subsequently, as a second threshold voltage sensing section (2rd Vth Sensing), referring to FIGS. 15B and 16, the first and second scan thin film transistors are output by outputting the first and third scan signals Scan1 and Scan2 at a low level. When both (SC-TFT1, SC-TFT2) are turned off, the first and second nodes N1 and N2 are in a floating state, and each node N1 and N2 is a driving thin film transistor ( DR-TFT), the voltage level gradually rises closer to the actual threshold voltage Vth according to the voltage between the gate and the source. That is, the voltages of the first and second nodes N1 and N2 are Vini +ΔVs and Vini-Vth×α+ΔVs, respectively. Here, the voltage change amount ΔVs is proportional to α, and is inversely proportional to the Vth value. That is, the larger the Vth value, the smaller the α value, and the Vth value is sensed at a faster time.

Next, in the electronic mobility correction and data writing section (μ compensation & writing), referring to FIGS. 15C and 16, the first scan signal Scan1 is applied at a low level and the second scan signal Scan2 is set to high. The first node N1 is charged with the data voltage Vdata by applying the data voltage Vdata at the same time as the level. Accordingly, in response to the characteristic of the electron mobility μ of the driving thin film transistor DR-TFT, the second node N2 is gradually charged, and as a result, the capacitor C1 is pre-charged Vini-Vth×α+ΔVs. The voltage change amount (ㅿV(μ)) according to the electron mobility is added to.

Here, the coupling according to the voltage change of the first node N1 is much smaller than the capacitance of the organic light emitting diode EL and can be ignored. In addition, the ㅿV(μ) indicates the amount of change in voltage of the N2 node N2 according to the electron mobility sensing of the driving thin film transistor (DR-TFT). As the value of μ increases, the ㅿV(μ) increases. -The voltage between the sources (Vgs) decreases and the electron mobility is compensated in the direction of reducing the current. As the value of μ increases, the ㅿV (μ) increases, so the voltage between the gate and source (Vgs) becomes relatively large. Is compensated.

Next, referring to FIGS. 15D and 16, in the emission section, the first and second scan thin film transistors SC-TFT1 are applied by applying both the first and second scan signals Scan1 and Scan2 at a low level. After turning off, the driving thin film transistor DR-TFT applies current Ioled to the organic light emitting diode EL in response to Vgs-Vth stored in the capacitor C1 to emit light.

Meanwhile, the voltage Vgs-Vth stored in the capacitor C1 corresponds to Equation 3 below.

The DTE indicates a voltage loss due to coupling due to the parasitic capacitance component of the first node N1, and the threshold voltage Vth is also affected, and compensation is required. To this end, ΔVs is adjusted to compensate for the DTE by comparing the voltage between the gate and the source for any two pixels.

This ΔVs can be adjusted by shortening or lengthening the time of the second threshold voltage sensing period (2rd Vth Sensing).

Referring to FIG. 16, when the threshold voltages of two arbitrary pixels are Vth1 and Vth2, respectively, Vgs1 of pixel 1 is DTE=[Vdata-(Vini-Vth×α1+ΔVs1+ΔV(μ))], Vgs2 of the second pixel becomes DTE=[Vdata-(Vini-Vth×α2+ΔVs2+ΔV(μ))].

Here, if Vgs2-Vgs1=ΔVth is satisfied, it means that Vth is 100% compensated, so referring to Equation 4 below,

Here, β denotes the threshold voltage sensing ratio, and when Vth2> Vth1 satisfies α2 <β <1, ΔVs2 <ΔVs1 is established.

That is, ΔVs is adjusted so that ΔVth×β-ΔVs2+ΔVs1 = 1/DTE×ΔVth, and amplified sensing is performed to perform compensation.

Accordingly, β×ΔVth is about 0.9×ΔVth in the first threshold voltage sensing period, but the threshold voltage can be compensated for about 1.1×ΔVth through the second threshold voltage sensing period.

17A and 17B are views comparing threshold voltage (Vth) compensation characteristics of organic light emitting display devices according to the first and second embodiments of the present invention.

Referring to FIG. 17A, in the organic light emitting display device according to the first embodiment of the present invention, the compensation error rate according to the sensing of ΔVth was measured to be about 7.5%. Since the compensation error rate according to the sensing of ΔVth is measured to be less than 1%, it can be seen that the compensation error rate is greatly improved. Although many items are specifically described in the above description, this should be interpreted as an example of a preferred embodiment rather than limiting the scope of the invention. Therefore, the invention should not be determined by the described embodiments, but should be defined by the claims and equivalents to the claims.

100: display panel 110: timing control unit
120: scan driving unit 130: data driving unit
140: sensing control unit PX: pixel
SCL: Scan wiring DL: Data wiring
SSL: Sync wiring

Claims (22)

A display panel in which a plurality of pixels are defined at a point where the scan line, the data line, and the sensing line intersect;
A gate driving unit and a data driving unit supplying a scan signal and a data voltage to the pixel through the scan line and the data line;
A sensing control unit sensing electrical characteristics of the pixel; And
The gate driver, the data driver, and the sensing controller are controlled, and according to a set compensation control signal, the sensing controller controls to sense the electrical characteristic at a first point in time, and the pixel itself at a second point different from the first point in time Including a timing controller for controlling to sense the electrical characteristics,
The pixel is
An organic light emitting diode, a driving thin film transistor connected to a power line and driving the organic light emitting diode, a scan thin film transistor connecting the data line and the first node of the driving thin film transistor by controlling the scan signal, and a sensing signal control By means of a sensing thin film transistor connecting the sensing wiring and a second node of the driving thin film transistor, a capacitor connected between the first and second nodes,
The pixels are sequentially driven in the order of an initialization period, a threshold voltage sensing period of the driving thin film transistor, an electron mobility correction and writing period of the driving thin film transistor, and an emission period,
During the initialization period, the scanning thin film transistor and the sensing thin film transistor are turned on, applying an offset voltage supplied to the data line to the first node, and applying an initialization voltage of the sensing line to the second node and,
During the threshold voltage sensing period, the scan thin film transistor is turned on to apply the offset voltage to the first node, the sensing thin film transistor is turned off, and the capacitor is the threshold voltage of the driving thin film transistor Is sensed and saved,
During the electron mobility correction and writing period, the scan thin film transistor maintains turn-on, applies the data voltage supplied to the data line to the first node, and the sensing thin film transistor is turned off, and the The capacitor stores the difference voltage between the offset voltage and the amount of voltage change according to the electron mobility in the sum of the data voltage and the threshold voltage,
During the emission period, the scanning thin film transistor and the sensing thin film transistor are turned off, and the driving thin film transistor drives the organic light emitting diode according to a voltage stored in the capacitor. A display panel in which a plurality of pixels are defined at a point where the scan line, the data line, and the sensing line intersect;
A gate driving unit and a data driving unit supplying a scan signal and a data voltage to the pixel through the scan line and the data line;
A sensing control unit sensing electrical characteristics of the pixel; And
The gate driver, the data driver, and the sensing controller are controlled, and according to a set compensation control signal, the sensing controller controls to sense the electrical characteristic at a first point in time, and the pixel itself at a second point different from the first point in time Including a timing controller for controlling to sense the electrical characteristics,
The pixel is
An organic light emitting diode, a driving thin film transistor connected to a power supply line and driving the organic light emitting diode, a first scan thin film transistor connecting the data line and a first node of the driving thin film transistor by controlling a first scan signal, 2 A second scan thin film transistor that applies an offset voltage to the first node by controlling a scan signal, a sensing thin film transistor connecting the sensing wiring and a second node of the driving thin film transistor by controlling a sensing signal, and the first It is composed of a capacitor connected between the first and second nodes,
The pixels are sequentially driven in the order of an initialization period, a threshold voltage sensing period of the driving thin film transistor, an electron mobility correction and writing period of the driving thin film transistor, and an emission period,
During the initialization period, the first scan thin film transistor is turned off, and the second scan thin film transistor and the sensing thin film transistor are turned on to apply the offset voltage to the first node and the offset voltage to the second node. Apply the initializing voltage of the sensing wiring,
During the threshold voltage sensing period, the first scan thin film transistor is turned off and the second scan thin film transistor is turned on to apply the offset voltage to the first node, and the sensing thin film transistor is turned on. Is off, the capacitor senses and stores the threshold voltage of the driving thin film transistor,
During the electron mobility correction and writing period, the first scan thin film transistor is turned on to apply the data voltage of the data line to the first node, and the second scan thin film transistor and the sensing thin film transistor are turned off. Thus, the capacitor stores the difference voltage of the amount of voltage change according to the offset voltage and the electron mobility in the sum of the data voltage and the threshold voltage,
During the emission period, the first and second scan thin film transistors and the sensing thin film transistors are turned off, and the driving thin film transistor drives the organic light emitting diode according to a voltage stored in the capacitor. The method of claim 1,
Before the initialization period,
A section in which the scanning thin film transistor is turned off, the sensing thin film transistor is turned on, and the initialization voltage is applied to the second node,
The organic electric field further comprises a section in which the scanning thin film transistor and the sensing thin film transistor are turned on, the data voltage of the previous horizontal line of the data wiring is applied to the first node and the initialization voltage is applied to the second node Luminous display device. The method according to any one of claims 1 and 2,
The organic electroluminescent display device in which the electron mobility correction and writing section is set to correct the electron mobility. The method of claim 4,
The sensing control unit,
A precharging switch for applying a precharging voltage to the sensing line in response to a precharging signal;
An analog-to-digital converter for sampling a voltage applied to the sensing line; And
Sampling switch connecting the sensing wiring and analog-digital converter in response to a sampling signal
An organic light emitting display device comprising a. The method of claim 4,
The compensation control signal,
Upon initial driving, the electrical characteristic is sensed at least once by the sensing control unit, and then the pixel itself is controlled to sense the electrical characteristic.
An organic light emitting display device characterized by a. The method of claim 4,
The compensation control signal,
The electrical characteristics are sensed by the sensing controller at least once at power-on and power-off times, and the pixel itself senses the electrical characteristics during the remaining driving period.
An organic light emitting display device characterized by a. The method of claim 4,
The compensation control signal,
It is applied according to a set period and senses the electrical characteristic by the sensing control unit, and controls the pixel itself to sense the electrical characteristic during the remaining driving period.
An organic light emitting display device characterized by a. delete delete delete delete delete Each of the plurality of pixels includes an organic light emitting diode, a driving thin film transistor connected to a power line and driving the organic light emitting diode, and a first applying an initialization voltage to a first node of the driving thin film transistor under control of a first scan signal. A scan thin film transistor, a second scan thin film transistor that applies a data voltage to the first node under control of a second scan signal, and a capacitor connected between the first and second nodes,
The pixels are driven in the order of an initialization section, a first threshold voltage sensing section, a second threshold voltage sensing section, an electronic mobility correction and writing section, and an emission section,
During the initialization period, the second scan thin film transistor is turned off, the first scan thin film transistor is turned on to apply the initialization voltage to the first node, and a low lower than the initialization voltage to the power wiring. Applying a power voltage of a level to apply the power voltage of the low level to the second node,
During the first threshold voltage sensing period, the second scan thin film transistor is turned off, and the first scan thin film transistor is turned on to apply the initialization voltage to the first node, and a high voltage to the power wiring. By applying a power supply voltage of a level, the capacitor stores the first voltage sensed first according to the threshold voltage of the driving thin film transistor and the sensing rate, and during the second threshold voltage sensing period, the first and second voltages The 2 scan thin film transistor is turned off, and the capacitor stores a second voltage sensed secondly by rising from the first voltage according to the threshold voltage of the driving thin film transistor and a sensing rate thereof,
During the electromobility correction and writing period, the first scan thin film transistor is turned off and the first scan thin film transistor is turned on to apply a data voltage of a data line to the first node, and the capacitor is A data voltage, the initialization voltage, the second voltage, and a voltage in which a voltage change amount according to the electron mobility is reflected, and
During the emission period, the first and second scan thin film transistors are turned off, and the driving thin film transistor drives the organic light emitting diode according to a voltage stored in the capacitor. delete delete delete delete delete delete delete The method of claim 14,
An organic light emitting display device in which a period of the second threshold voltage sensing period is adjusted by comparing a gate-source voltage for two arbitrary pixels.

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