KR20170040522A - Organic light emitting diode display device - Google Patents

Abstract

An organic light emitting diode display device (100) according to an embodiment of the present invention includes a display panel (116) including a driving switch (DR) for controlling a current which flows in an organic light emitting diode (OLED), a timing controller (124) including a lookup table (330) including over-driven gradation corresponding to the gradation of previous and current data signals, and a data driving circuit (120) which outputs a data voltage corresponding to the data signal of the over-driven gradation to the driving switch. The over-driven gradation is set based on a threshold voltage (Vth) of the driving switch (DR). Accordingly, the present invention can improve a pixel charging feature by reducing a voltage swing width.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting diode display device and an organic light emitting diode display device for over driving.

 2. Description of the Related Art In recent years, various flat panel displays (FPDs) have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. Such a flat panel display device includes a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP) And a light emitting device (Electroluminescence Device).

PDP has attracted attention as a display device that is most advantageous for large screen size but small size because of its simple structure and manufacturing process, but it has disadvantage of low luminous efficiency, low luminance and high power consumption. A TFT LCD to which a thin film transistor (hereinafter referred to as "TFT") is applied as a switching element is the most widely used flat panel display device, but it has a problem that the viewing angle is narrow and the response speed is low because it is a light emitting device. On the other hand, the electroluminescent device is divided into an inorganic light emitting diode display device and an organic light emitting diode display device according to the material of the light emitting layer. In particular, the organic light emitting diode display device uses self light emitting devices that emit self- Brightness and viewing angle are large.

The organic light emitting diode display controls the voltage between the gate terminal and the source terminal of the driving transistor to control the current flowing from the drain to the source of the driving transistor.

The current flowing from the drain to the source of the driving transistor flows through the organic light emitting diode and emits light, and the degree of light emission can be controlled by controlling the amount of current.

Conventional organic light emitting diode (OLED) display devices, liquid crystal display devices, and the like have been applied overdriving or overdrive driving methods in which image data is modulated and displayed to increase the response speed of each pixel. In the conventional overdriving method, the image data of the current frame is compared with the image data of the previous frame, and the image data value is modulated according to the difference.

However, when the previous image data has a gradation value larger than 0 and the current image data has 0 gradation, there is no gradation smaller than 0 gradation. In this case, the 0 gradation can be fixedly used, There was a problem that could not be done.

The embodiment according to the present invention is an organic light emitting diode display device capable of reducing the voltage swing width when changing the voltage from the previous data to the current data by updating the lookup table for over driving by reflecting the degradation characteristics of the threshold voltage of the driving switch. Can be provided.

An organic light emitting diode display 100 according to an embodiment of the present invention includes a display panel 116 including a driving switch DR for controlling a current flowing in an organic light emitting diode OLED, A data driving circuit 120 for outputting a data voltage corresponding to the data signal of the over-driven gradation to the driving switch, a timing controller 124 having a look-up table 330 including a over- , And the over-driven gradation is set based on the threshold voltage Vth of the drive switch DR. Also, the timing controller 124 may include a memory 310 for storing the previous data, and a memory 310 for outputting any one of the overdrived data from the current data or the lookup table 330 according to overdriving A threshold voltage variation detection unit 350 for detecting a variation amount of the threshold voltage Vth from a threshold voltage Vth of the driving switch DR and a data selection output unit 320 for outputting a threshold voltage Vth, And a lookup table updating unit 360 for updating the lookup table 330 based on the lookup table. A threshold voltage detector 350 for detecting the degree of shift of the threshold voltage, that is, the amount of variation, based on the threshold voltage of the driving switch DR sensed from the compensation circuit 130, Up table update unit 360 that updates the look-up table 330 based on the threshold voltage variation amount of the look-up table. The threshold voltage detector 350 reads information on the threshold voltage Vth of the driving switch DR from the memory 134 on the data driving circuit 120 or the compensation circuit 130 to detect the threshold voltage Vth, It is possible to detect a fluctuation amount due to the deterioration of the image sensor.

The lookup table update unit 330 may increase the overdrive gray level corresponding to the previous data of the gray level value greater than 0 and the current data of the 0 gray level as the threshold voltage Vth rises . That is, the data voltage corresponding to the data signal of the overdriving gradation level is larger than the sum voltage of the reference voltage Vref and the pre-rising threshold voltage Vth1, and the data voltage corresponding to the reference voltage Vref and the threshold voltage Vth2, So that the swing width of the previous and current data voltages can be reduced.

The embodiment according to the present invention can improve the pixel charging characteristic by reducing the voltage swing width when changing the voltage from the previous data to the current data by updating the lookup table for overdriving reflecting the degradation characteristics of the threshold voltage of the driving switch have.

1 is a view showing a structure of an organic light emitting diode.
2 is a circuit diagram showing one pixel equivalently in an organic light emitting diode display according to an embodiment of the present invention.
3 is a block diagram illustrating an organic light emitting diode display device according to an embodiment of the present invention.
4 is a diagram illustrating a pixel structure according to an embodiment of the present invention.
5 is a waveform diagram showing voltage waveforms on the first and second nodes during threshold voltage sensing.
6 to 8 are diagrams showing the operation of a pixel at the time of threshold voltage sensing.
9 is a block diagram of an internal structure of a data driving circuit according to an embodiment of the present invention.
10 is a diagram showing an overdriving block included in the timing controller.
11 is a graph showing variation in threshold voltage of the driving switch.
12 is a time-series representation of the threshold voltage sensing of the driving switch, the lookup table update, and the display period.

Hereinafter, an organic light emitting diode display device according to an embodiment of the present invention will be described in detail with reference to the drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the size and thickness of an apparatus may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. However, it should be understood that the present invention is not limited to the embodiments disclosed herein but may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification. The dimensions and relative sizes of the layers and regions in the figures may be exaggerated for clarity of illustration.

It will be understood that when an element or layer is referred to as being another element or "on" or "on ", it includes both intervening layers or other elements in the middle, do. On the other hand, when a device is referred to as "directly on" or "directly above ", it does not intervene another device or layer in the middle.

The terms spatially relative, "below," "lower," "above," "upper," and the like, And may be used to easily describe the correlation with other elements or components. Spatially relative terms should be understood to include, in addition to the orientation shown in the drawings, terms that include different orientations of the device during use or operation. For example, when inverting an element shown in the figures, an element described as "below" or "beneath" of another element may be placed "above" another element. Thus, the exemplary term "below" can include both downward and upward directions.

The terminology used herein is for the purpose of describing embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. &Quot; comprise "and / or" comprising ", as used in the specification, means that the presence of stated elements, Or additions.

≪ Structure of organic light emitting diode &

1 is a view showing a structure of an organic light emitting diode.

The organic light emitting diode display device may have an organic light emitting diode as shown in FIG.

The organic light emitting diode may include organic compound layers (HIL, HTL, EML, ETL, EIL) formed between the anode electrode and the cathode electrode. The organic compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer EIL). When a driving voltage is applied to the anode electrode and the cathode electrode, holes passing through the HTL and electrons passing through the ETL are transferred to the EML to form excitons, Thereby generating visible light. In addition, the organic light emitting diode includes an R emissive layer that displays red, a G emissive layer that displays green, and a blue (green) emissive layer that emits green light, depending on the color to be displayed, Blue), and further, a white organic light emitting diode having a structure in which the R light emitting layer, the G light emitting layer, and the B light emitting layer are selectively stacked. The organic light emitting diode display device arranges the pixels including the organic light emitting diode in a matrix form and controls the brightness of the pixels selected by the scan pulse according to the gray level of the digital video data. Such an organic light emitting diode display device is divided into a passive matrix type and an active matrix type using a TFT as a switching element. Among these, the active matrix method selects a pixel by selectively turning on the TFT as the active element and maintains the light emission of the pixel with the voltage held in the storage capacitor.

≪ Equivalent circuit diagram of active matrix type pixel &

2 is a circuit diagram showing one pixel equivalently in an organic light emitting diode display according to an embodiment of the present invention.

Referring to FIG. 2, the pixel of the organic light emitting diode display according to the exemplary embodiment of the present invention includes an organic light emitting diode (OLED), data lines D and gate lines G intersecting with each other, A scan switch SW for sequentially transmitting data to the pixels in the scan pulse SP, a drive switch DR for generating a current by a voltage between the gate and the source terminals, And a storage capacitor Cst. The scan switch SW and the drive switch DR may be formed of an N-type MOS-FET. The structure consisting of two transistors SW and DR and one capacitor Cst can be simply referred to as a 2T-1C structure. The scan switch SW is turned on in response to the scan pulse SP from the gate line G to conduct a current path between the source electrode and the drain electrode. The data voltage from the data line D during the ON time period of the scan switch SW is supplied to the gate electrode of the drive switch DR and the storage capacitor CL2 through the source electrode and the drain electrode of the scan switch SW Cst. The driving switch DR controls the current flowing in the organic light emitting diode OLED according to the difference voltage Vgs between the gate electrode and the source electrode of the driving switch DR. The storage capacitor Cst keeps the voltage supplied to the gate electrode of the driving switch DR constant for one frame period by storing the data voltage applied to one electrode of the storage capacitor Cst. An organic light emitting diode (OLED) having the structure as shown in FIG. 1 is connected between the source electrode of the driving switch DR and the low potential driving voltage source VSS. The current flowing through the organic light emitting diode OLED is proportional to the brightness of the pixel, which is determined by the gate-source voltage of the driving switch DR. The brightness of the pixel as shown in FIG. 2 is proportional to the current flowing in the organic light emitting diode OLED, as shown in Equation 1 below.

Equation 1

는 구동 스위치(DR)의 이동도 및 기생용량에 의해 결정되는 상수값을 각각 의미한다. 수학식 1과 같이, 유기발광다이오드(OLED)의 전류(Ioled)는 구동 스위치(DR)의 문턱전압(Vth)에 크게 영향 받는다는 것을 알 수 있다. 따라서 전체 영상 이미지의 균일도는 구동 스위치(DR)의 특성 편차, 즉 문턱전압의 편차에 의해 좌우될 수 있다. Here, 'Vgs' is the difference voltage between the gate voltage Vg and the source voltage Vs of the drive switch DR, 'Vdata' is the data voltage, 'Vinit' is the initialization voltage, 'Ioled' Vth 'is the threshold voltage of the drive switch DR,

Quot; means a constant value determined by the mobility and the parasitic capacitance of the drive switch DR. It can be seen that the current Ioled of the organic light emitting diode OLED is greatly affected by the threshold voltage Vth of the driving switch DR, as shown in Equation (1). Therefore, the uniformity of the entire image can be influenced by the characteristic deviation of the drive switch DR, that is, the deviation of the threshold voltage.

≪ Block Diagram of Organic Light Emitting Diode Display Device >

3 is a block diagram illustrating an organic light emitting diode display device according to an embodiment of the present invention.

3, an organic light emitting diode display 100 according to an exemplary embodiment of the present invention includes a system board 123, a display panel 116, a gate driving circuit 118, a data driving circuit 120, (Not shown).

The system board 123 can supply a timing signal including a vertical / horizontal synchronizing signal, a dot clock signal, a data enable signal, and the like, digital video data, and a power supply voltage Vcc to the timing controller 124. The system board 123 incorporates a scaler circuit to adjust the resolution of the digital video data to be supplied to the timing controller 124. The system board 123 may transmit a timing signal and digital video data to the timing controller 124 through an LVDS (Low Voltage Differential Signaling) interface.

The display panel 116 includes m data lines D1 to Dm, k sensing lines S1 to Sk, n gate lines G1 to Gn, and j And pixels 122 formed in a crossing region of the sensing control lines SC1 to SCj. Signal lines for supplying the first driving power Vdd to the respective pixels 122 and signal lines for supplying the second driving power Vss may be formed on the display panel 116. [ Here, the first driving power supply Vdd and the second driving power supply Vss may be generated from the high potential driving voltage source VDD and the low potential driving voltage source VSS, respectively. The gate drive circuit 118 generates a scan pulse SP in response to the gate control signal GDC from the timing controller 124 and sequentially supplies the scan pulse SP to the gate lines G1 to Gn. The gate drive circuit 118 can also output a control signal SCS from the timing controller 124 and the sensing switch in each pixel can be controlled by the sensing control signal SCS. The gate driving circuit 118 outputs both the scan pulse SP and the sensing control signal SCS. However, the present invention is not limited thereto, and the timing control circuit 124 may control the sensing control signal SCS It is also possible to provide a sensing switch control driver which can output a large amount of data. The data driving circuit 120 can be controlled by the data controller DDC from the timing controller 124 and outputs the sensing voltage to the data lines D1 to Dm and the sensing voltages S1 to Sk . Each of the data lines D1 to Dm may be connected to each of the pixels 122 to apply a data voltage to each of the pixels 122. [ Each of the sensing lines S1 to Sk may be connected to the pixel 122 to supply a sensing voltage and measure a sensing voltage on the sensing lines S1 to Sk. Specifically, by supplying the initialization voltage using one sensing line (S1 to Sk), it is possible to detect the sensing voltage using charging and floating with the initialization voltage. The data driving circuit 120 can output or detect the data voltage and the sensing voltage. However, the present invention is not limited to this, and may include a separate driver capable of outputting or detecting the sensing voltage.

<Pixel Structure>

4 is a diagram illustrating a pixel structure according to an embodiment of the present invention.

The pixel 122 described in the present invention may refer to any one of red, green, blue, and white, which may be referred to as a sub-pixel separately. The sub-pixel 122 may include a scan switch SW, a drive switch DR, a sensing switch SEW, an organic light emitting diode OLED, and a storage capacitor Cst. The scan switch SW is controlled by the scan pulse SP on the gate line Gn and supplies data on the data line Dm to the sub pixel 122. The scan switch SW is a transistor for controlling the data line Dm, And may be connected between the node N1. The driving switch DR is a transistor for adjusting a current flowing in the organic light emitting diode OLED by a voltage between a first node N1 and a second node N2 which are gate-source of the driving switch DR, The source terminal may be connected to the second node N2, and the drain terminal may be connected to the first driving power source Vdd. The sensing switch SEW is a transistor for controlling the threshold voltage of the driving switch DR through the initialization and sensing line Sk to the second node N2 and controls the sensing control line SCj May be controlled by a signal SCS and may be connected between the second and third nodes N2 and N3. The anode terminal of the organic light emitting diode OLED may be connected to the second node N2, and the cathode terminal thereof may be connected to the second driving power source Vss. The storage capacitor Cst may be connected between the first and second nodes N1 and N2, that is, between the gate and source terminals of the drive switch DR.

<Threshold Voltage Sensing and Compensation>

FIG. 5 is a waveform diagram showing voltage waveforms on the first and second nodes during threshold voltage sensing, and FIGS. 6 to 8 are diagrams showing the operation of pixels upon threshold voltage sensing.

The threshold voltage of the driving switch DR can be sensed and compensated through the following process.

(1) Initialization period: t1

5 and 6, the scan switch SW and the sensing switch SEW are turned on in the initialization period t1 and the sensing voltage Vsen provided from the data line Dm is applied to the scan switch SW, And the reference voltage Vref provided from the sensing line Sk in response to the initialization control signal Spre is supplied to the second node N2 through the sensing switch SEW, (Supplied). And the storage capacitor Cst is initialized to a voltage difference on the first and second nodes N1 and N2, that is, Vsen-Vref. At this time, the organic light emitting diode OLED is driven by the reference voltage Vref and the second driving power source Vss so as not to emit light by the reference voltage Vref supplied to the second node N2 through the sensing switch SEW, The voltage of at least one of the reference voltage Vref and the second driving power source Vss may be set so that the potential difference of the reference voltage Vref does not exceed the threshold voltage of the organic light emitting diode OLED.

(2) Source follower Driving period: t2

5 and 7, in the source follower driving period t2, the sensing line Sk is floated (by the sampling signal Sam signal), the sensing line Sk is electrically opened with the ADC 220, The sensing line Sk and the reference voltage generating portion 133 are electrically opened by the initialization control signal Spre and the scan switch SW and the sensing switch SEW are kept turned on and the storage capacitor Cst A current flows to the drive switch DR by using the high potential power supply Vdd as an energy source by the voltage stored in the voltage supply source Vdd, that is, the voltage Vgs between the gate and source terminals of the drive switch DR. Then, the current flowing through the drive switch DR charges the second node N2, and the voltage on the second node N2 rises. At this time, since the Vgs of the drive switch DR decreases, the current flowing in the drive switch DR also decreases. When Vgs reaches the threshold voltage of the driving switch DR, no current flows to the driving switch DR and the voltage on the second node N2 is kept constant.

(3) Threshold voltage detection period: t3

5 and 8, in the threshold voltage detection period t3, the sensing line Sk is electrically connected to the ADC 220 by the sampling signal Sam, and the voltage on the second node N2 And is changed to a digital signal. Then, when generating the compensation data signal to be supplied to the data line Dm in the characteristic compensation of the driving switch, the threshold voltage Vth of the driving switch DR is used by using the detected threshold voltage Vth of the driving switch DR, ) Can be compensated. Further, the detected threshold voltage Vth is provided to the timing controller 124, and a variation amount of the threshold voltage Vth may be detected to update a lookup table for overdriving.

<Internal Structure of Data Driving Circuit or Compensating Circuit>

9 is a block diagram of an internal structure of a data driving circuit according to an embodiment of the present invention.

9, the data driving circuit 120 includes a sampling switch SW10 and an initialization switch SW20 for applying a reference voltage Vref, a sensing circuit 131, an analog-to-digital converter (ADC) 132, and a reference voltage generator 133.

The initialization switch SW20 is turned on during the initialization period in response to the initialization control signal Spre to sense the reference voltage Vref supplied from the reference voltage generator 133 to the sensing Can be supplied to the line Sk.

The initialization control signal Spre for controlling the initialization switch SW20 may be provided from the timing controller 124. [

The sampling switch SW10 is turned on by a sampling signal Sam at a high level during threshold voltage sensing so that the sensing circuit 131 can detect the sensing voltage on the sensing lines S1 to Sk. The sampling signal Sam for controlling the sampling switch SW10 may be provided from the timing controller 124. [

On the other hand, the sensing lines S1 to Sk can be floated by the low logic signal of the sampling signal Sam and the low logic signal of the initialization control signal Spre.

The ADC 132 may convert the sensing voltage on the sensing lines S1 to Sk detected by the sensing circuit 240 to a digital value and provide the digital value to the memory 134, Thereby storing information on the threshold voltage of the driving switch DR in the pixel 122. [

The controller 135 provides information on the threshold voltage of the driving switch DR in the pixel 122 stored in the memory 134 to the timing controller 124. The timing controller 124 controls the data driver 120 Can provide the compensated data voltage to the data lines D1 to Dm. Thus, the threshold voltage of the driving switch DR in the pixel 122 can be considered.

The ADC 132 may be separate from the sensing circuit 131 or included in the sensing circuit 131.

However, the present invention is not limited to this. It is also possible to use a circuit for sensing the characteristics of the drive switch DR and the characteristics of the organic light emitting diode (OLED) The compensating circuit 130 may be provided on a separate substrate.

<Internal Structure of Timing Controller>

10 is a diagram showing an overdriving block included in the timing controller.

Referring to FIG. 10, the timing controller 124 includes a field memory 310 for storing data of a previous field and a field memory 310 for outputting currently input data as it is when over driving is not performed, The amount of shift of the threshold voltage, that is, the amount of variation, is calculated based on the threshold voltage of the data selection output unit 320 for selecting and outputting the output value of the driving circuit 330 and the driving switch DR sensed by the compensation circuit 130 And a lookup table update unit 360 that updates the lookup table 330 based on the threshold voltage variation amount from the threshold voltage detection unit 350. [ The threshold voltage detector 350 reads information on the threshold voltage Vth of the driving switch DR from the memory 134 on the data driving circuit 120 or the compensation circuit 130 to detect the threshold voltage Vth, It is possible to detect a fluctuation amount due to the deterioration of the image sensor.

Specifically, the lookup table 330 may have an overdrafted tone value corresponding to the previous data signal and the current data signal. That is, when the gray level value of the previous data signal is 10 gray levels and the gray level value of the current data signal is 15 gray levels, overdrafted gray level values corresponding to the previous and present data signals may be 18 gray levels. When the gray level of the previous data signal is 15 gray levels and the gray level of the current data signal is 10 gray levels, the overdrived gray level values corresponding to the previous and current data signals may be 7 gray levels. When the gray level value is lowered from the previous data signal to the current data signal, overdriving at a lower gray level than the current data signal may be referred to as underdriving.

If the grayscale value of the previous data signal is 10 grayscale and the grayscale value of the current data signal is 0 grayscale, there is no grayscale of 0 grayscale or less. Therefore, the overdrived grayscale value is 0 grayscale or a threshold voltage (Vth) The gradation can be higher than the 0 gradation. In this case, it can be said that the overdrived tone is not overdrived since the overdrive tone is not lower than the 0 tone of the current data.

However, if the overdrive tone value is set to a gradation higher than the 0 gradation based on the threshold voltage (Vth) variation, the data voltage output from the analog voltage data driving circuit 120 corresponding to the previous data signal The swing width from the analog voltage corresponding to the data signal to the data voltage output from the data driving circuit 120 can be reduced. That is, by updating the previous data of the gradation value larger than 0 and the overdrived gradation corresponding to the current gradation of 0 gradation to a gradation value of 0 gradation or more, rather than 0 gradation, And the swing width of the current data voltage can be reduced.

Further, when the threshold voltage Vth of the driving shoe position DR rises, it is possible to increase the overdrived gradation corresponding to the previous data of the gradation value larger than 0 and the current data of the 0 gradation The contents will be described later).

<Shift of Threshold Voltage>

11 is a graph showing variation in threshold voltage of the driving switch. And FIG. 12 is a diagram showing the threshold voltage sensing of the driving switch, the lookup table update, and the display period in a time-wise manner.

As the drive switch DR is deteriorated, the threshold voltage Vth can be shifted along with the drive switch DR, and the drive switch DR can be restored to its original state when the drive switch DR is not driven. However, depending on the material used for manufacturing the drive switch DR, the threshold voltage shift due to the deterioration and the degree of the threshold voltage shift due to the recovery may be different, so that the threshold voltage is shifted in the positive or negative direction .

According to the above-mentioned Equation (1), the data voltage value for gradation representation can be changed according to the shift of the threshold voltage.

According to Equation 1, the current Ioled flowing in the organic light emitting diode OLED is the gate of the drive switch DR, which is the voltage difference on the first and second nodes N1 and N2 on the pixel 122 in Fig. It can be understood that it can be changed not only according to the voltage difference between the source terminals Vgs but also on the threshold voltage Vth of the drive switch DR.

[Table 1]

For example, when the reference voltage Vref is supplied to the second node N2 and the threshold voltage Vth of the drive switch DR has a positive value, Is assumed to be as shown in Table 1.

- 1st City Area

More specifically, the threshold voltage Vth of the drive switch DR on the display panel 116 is sensed during the first time period T1, and the first threshold voltage Vth, which is the information of the threshold voltage Vth of the drive switch DR, The compensated data voltage as shown in Table 1 can be generated based on the threshold voltage Vth1.

In this case, the threshold voltage Vth of the drive switch DR on the display panel 116 during the first time period T1 is set to the first threshold voltage Vth, which is the information of the threshold voltage Vth of the sensed drive switch DR RTI ID = 0.0 &gt; Vth1) &lt; / RTI &gt; The lookup table 330 on the timing controller 124 may be updated by the lookup table updater 360 that has received the output signal from the threshold voltage detector 350 that detects the amount of variation in the threshold voltage.

[Table 2]

At this time, it is assumed that the drive switch DR is not deteriorated. It is assumed that the lookup table for overdriving on the lookup table is as shown in Table 2. In Table 2, X has an arbitrary gradation value, and A, B, C, D, E, and F can have 0 gradation.

- Second City Area

The second time period T2 which is the time period between the first and third time periods T1 and T3 is a display period and the second time period T2 is a time period Images can be displayed. In this case, as shown in Table 1, the data voltage of the first node N1 may be less than the sum voltage (Vref + Vth) of the reference voltage (Vref) and the threshold voltage (Vth) Assuming that the voltage difference (Vgs) between the gate and the source terminal of the drive switch DR should be less than or equal to 1V and less than 2V in order to express the 10 gradations, the data voltage of the first node N1 is set to the reference voltage Vref (Vref + Vth) + 2V from the sum voltage (Vref + Vth) +1 V of the threshold voltage (Vth), and the voltage difference between the gate and source terminals of the drive switch DR The data voltage of the first node N1 is increased from the sum voltage (Vref + Vth) + 3V of the reference voltage (Vref) and the threshold voltage (Vth) Vref + Vth) + 5V.

It is also assumed that the data voltage can be expressed by each of the gradations from 0.1 to 10 gradations from 0 gradation.

However, such a data voltage value is only an example, and the present invention is not limited thereto and may be varied.

- Third City Area

The threshold voltage Vth of the drive switch DR on the display panel 116 is sensed during the third time period T3 and the second threshold voltage Vth2, which is the information of the threshold voltage Vth of the drive switch DR, ) Information. Here, it is assumed that the threshold voltage Vth rises and the second threshold voltage Vth2 is 0.3V higher than the first threshold voltage Vth1. The lookup table update unit 360 may update the lookup table 330 based on the information about the second threshold voltage Vth2.

[Table 3]

And that the updated look-up table 330 is as shown in Table 3. As shown in Table 3, A, B, C, D, E, and F may have 0 to 3 gradations.

- Fourth City Area

Based on the first threshold voltage (Vth1) information sensed during the first time period (T1) during the fourth time period (T4) after updating the lookup table (330), video display is performed based on Table 1 A data voltage corresponding to each gradation can be supplied to the first node N1.

During the fourth time period T4, for example, when the previous data is 20 gradations and the current data is 0 gradation, the data voltage during the previous data is either Vref + Vth1 + 3V to Vref + Vth1 + 5V Voltage value. The current data is referenced to the look-up table 330 of the updated Table 3, and any one of the data voltages of 0 V or more and Vref + Vthl + 0.3 V or less, which are the data voltages corresponding to 0 gradation to 3 gradation on Table 1 Voltage can be output. Since the threshold voltage Vth of the current drive switch DR has been changed to the second threshold voltage Vth2 even if the data voltage is 0 V or higher and Vref + Vth1 + 0.3 V or lower, 0 gradation can be expressed even when 0V or more and a voltage lower than Vref + Vth1 + 0.3V, which is a data voltage corresponding to 0 gradation to 3 gradation on one phase, is outputted.

Preferably, the A, B, C, D, E, and F gradation values in Table 2 are preferably 1 to 3 gradations in the 0 gradation to the 3 gradation. In this case, from any one of the voltages of Vref + Vth1 + 3V and Vref + Vth1 + 5V which are the previous data of 20 gradations and Vref + Vth1 + 0.3V So that the swing width can be smaller than the swing width to the current data voltage corresponding to the 0 gradation, so that the charging characteristic can be improved.

- The 5th time zone

[Table 5]

The threshold voltage Vth of the drive switch DR on the display panel 116 is sensed during the fifth time period T5 and the third threshold voltage Vth3, which is the information of the threshold voltage Vth of the drive switch DR, The compensated data voltage can be generated as shown in Table 4. &lt; tb &gt; &lt; TABLE &gt; At this time, the third threshold voltage Vth3 due to the deterioration of the drive switch DR can be all reflected to the data voltage in accordance with the compensation of the data voltage. Therefore, the A, B, C, D, E, and F gradation values of the lookup table may be changed to 0 gradation levels as shown in Table 2 (note that the arbitrary gradation values of X may vary).

On the other hand, as shown in Fig. 11, the threshold voltage Vth can be periodically sensed. The lookup table 330 may be updated based on the sensed threshold voltage (Vth) information. Also, the process of generating compensation data based on the sensed threshold voltage Vth may be performed after sensing at least one threshold voltage Vth.

On the other hand, based on the sensed threshold voltage Vth, the display device 100 can be turned on at a power-on time, for a predetermined time after the power-off time, or at a specific time point during driving of the display device 100, The threshold voltage (Vth) sensing for updating the lookup table 330 may be performed periodically and may include threshold voltage (Vth) sensing for compensation of image data and threshold voltage (Vth) sensing Can be achieved by the method described in FIGS. 6 to 8. FIG.

On the other hand, the previous data and the current data may be data applied for each gate line Gn. That is, the field memory 310 on the timing controller 124 is a data signal applied to the pixel corresponding to the previous gate line Gn-1, and the data of the current field is the data signal applied to the next gate line Gn- May be a data signal applied to a pixel corresponding to the pixel Gn. By over-driving each line as described above and updating the look-up table 330 based on the threshold voltage Vth of the drive switch DR, the swing width of the data voltage that can be changed for each line is reduced, The charging characteristics can be improved.

Further, as the gate line Gn moves away from the data driving circuit 120, the gain of the data voltage is increased and output, thereby preventing deterioration of the charge characteristics due to the load on the display panel 116. [

As described above, according to the rise of the threshold voltage Vth of the drive switch DR, the previous data of the tone value larger than 0 on the lookup table 330 and the overdrived tone corresponding to the current data of the 0th tone, Driving gradation, and the data voltage corresponding to the data signal of the increased overdriving gradation is set to be equal to or less than the sum of the reference voltage and the increased threshold voltage, more preferably, The data voltage corresponding to the data signal of the overdriving gradation can be obtained by setting the data voltage to be higher than the data voltage corresponding to the 0 gradation before the generation of the data signal and the voltage lower than the sum of the reference voltage and the increased threshold voltage, Is higher than the sum of the reference voltage Vref and the pre-rising threshold voltage Vth1, and the reference voltage Vref and the increased threshold voltage Vth2 ) So that the swing width of the previous and current data voltages can be reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

100 display device
116 Display panel
122 pixels
118 Gate drive circuit
120 data drive circuit
123 system board
124 Timing controller
130 Compensation circuit
131 sensing circuit
132 analog digital conversion section
133 Reference voltage generator
134 Memory on Compensation Circuit
135 control unit
310 Memory on the timing controller
330 Lookup Table
350 threshold voltage variation amount detector
360 lookup table update unit

Claims (11)

A display panel including a drive switch for adjusting a current flowing through the organic light emitting diode;
A timing controller having a look-up table including over-driven gradations corresponding to gradations of previous and current data signals; And
And a data driving circuit for outputting a data voltage corresponding to the overdrived gradation data signal to the driving switch,
And the overdrived gradation is set based on a threshold voltage of the drive switch. The method according to claim 1,
The timing controller includes:
A memory for storing the previous data,
A data selection / output unit for outputting either the current data or the data having the overdrive gradation from the lookup table according to whether overdriving is performed,
A threshold voltage variation amount detecting section for detecting a variation amount of the threshold voltage from a threshold voltage of the driving switch,
And a look-up table updating unit for updating the look-up table based on a variation amount of the threshold voltage. The method according to claim 1,
Wherein the lookup table updating unit comprises:
And updates the overdrived gradation corresponding to the previous data of the gradation value greater than 0 and the current data of the 0 gradation. The method of claim 3,
Wherein the lookup table updating unit comprises:
And increases the overdrived gradation corresponding to the previous data of the gradation value larger than 0 and the current data of the 0 gradation in accordance with the rise of the threshold voltage. 5. The method of claim 4,
In the display panel,
A scan switch for providing a data signal on a data line to a gate terminal of the drive switch in response to a scan pulse on the gate line,
Further comprising a sensing switch for supplying a reference voltage on a sensing line to a source terminal of the drive switch in response to a sensing control signal,
The overdrived gradation corresponding to the previous data of the gradation value larger than 0 and the current data of the 0 gradation on the lookup table fluctuates in accordance with the increase of the threshold voltage to the overdriving gradation increased,
Wherein the data voltage corresponding to the data signal of the overdriving gradation level is equal to or less than the sum of the reference voltage and the threshold voltage. A scan switch for providing a data signal on a data line in response to a scan pulse on a gate line to a gate terminal of the drive switch, A display panel including a sensing switch for supplying a reference voltage on a line to a source terminal of the drive switch;
A timing controller having a look-up table including over-driven gradations corresponding to gradations of previous and current data signals; And
And a data driving circuit for outputting a data voltage corresponding to the overdrived gradation data signal to the driving switch,
Wherein the overdrived gradation is set based on a threshold voltage of the drive switch sensed. The method according to claim 6,
The gate and source terminals of the drive switch are initialized by turning on the scan switch and the sensing switch,
The voltage of the source terminal of the drive switch rises by the floating of the sensing line until the potential difference between the gate and the source terminal of the drive switch becomes the threshold voltage of the drive switch,
And detects a source terminal voltage of the driving switch to store a threshold voltage of the driving switch. 8. The method of claim 7,
A threshold voltage variation amount detecting unit for detecting a variation amount of the threshold voltage from a threshold voltage of the driving switch;
And a look-up table updating unit for updating the look-up table based on a variation amount of the threshold voltage. 9. The method of claim 8,
Wherein the lookup table updating unit comprises:
And updates the overdrived gradation corresponding to the previous data of the gradation value greater than 0 and the current data of the 0 gradation. 9. The method of claim 8,
The overdrived gradation corresponding to the previous data of the gradation value larger than 0 and the current data of the 0 gradation on the lookup table fluctuates in accordance with the increase of the threshold voltage to the overdriving gradation increased,
Wherein the data voltage corresponding to the data signal of the overdriving gradation level is equal to or less than the sum of the reference voltage and the threshold voltage. 11. The method of claim 10,
Wherein the data voltage corresponding to the data signal of the increased overdriving gradation is larger than the sum voltage of the reference voltage and the pre-rising threshold voltage, and is equal to or smaller than the sum of the reference voltage and the increased threshold voltage.

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