KR102416677B1 - Organic light emitting diode display device - Google Patents

Abstract

The organic light emitting diode display 100 according to the embodiment of the present invention includes a display panel 116 including a driving switch DR for controlling a current flowing through the organic light emitting diode OLED, and grayscales of previous and current data signals. A timing controller 124 having a lookup table 330 including an overdriven gray level corresponding to , the overdriven grayscale is set based on a threshold voltage Vth of the driving switch DR.

Description

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

The present invention relates to an organic light emitting diode display and to an organic light emitting diode display for overdriving.

Recently, various flat panel displays (FPDs) capable of reducing weight and volume, which are disadvantages of cathode ray tubes, have been developed. Such flat panel displays include a liquid crystal display (hereinafter referred to as "LCD"), a field emission display (FED), a plasma display panel (hereinafter referred to as "PDP"), and an electric field. There is a light emitting device (Electroluminescence Device) and the like.

PDP is attracting attention as a display device that is light, thin, and most advantageous for a large screen because of its simple structure and manufacturing process. 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 element, but since it is a light emitting element, it has a narrow viewing angle and low response speed. In contrast, the electroluminescent device is largely 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. It has great advantages in luminance and viewing angle.

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

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

Conventional organic light emitting diode display devices, liquid crystal displays, etc. have been applied with an overdriving (or increased speed driving) method in which image data is modulated and displayed in order to speed up the response speed of each pixel. In the conventional overdriving method, the image data of the current frame and the image data of the previous frame are compared, and the image data value is modulated according to the difference and applied.

However, if the previous image data has a grayscale value greater than 0 and the current image data has a grayscale value of 0, there is no grayscale smaller than 0 grayscale. There was a problem that could not be done.

The embodiment according to the present invention reflects the deterioration characteristic of the threshold voltage of the driving switch and updates the lookup table for overdriving, thereby reducing the voltage swing width when the voltage is changed from the previous data to the current data. can provide

The organic light emitting diode display 100 according to the embodiment of the present invention includes a display panel 116 including a driving switch DR for controlling a current flowing through the organic light emitting diode OLED, and grayscales of previous and current data signals. A timing controller 124 having a lookup table 330 including an overdriven gray level corresponding to , the overdriven grayscale is set based on a threshold voltage Vth of the driving switch DR. In addition, the timing controller 124 outputs any one of the current data or the data having the overdriven grayscale from the memory 310 for storing the previous data, the current data or the lookup table 330 depending on whether overdriving is performed. data selection output unit 320, a threshold voltage fluctuation detection unit 350 for detecting the fluctuation amount of the threshold voltage Vth from the threshold voltage Vth of the driving switch DR, and the threshold voltage Vth fluctuation amount. It may further include a lookup table update unit 360 that updates the lookup table 330 based on the lookup table. And a threshold voltage detector 350 that detects a shift degree of the threshold voltage, that is, a variation amount, based on the threshold voltage of the driving switch DR sensed by the compensation circuit 130, and the threshold voltage detector 350 and a lookup table update unit 360 that updates the lookup table 330 based on the threshold voltage variation of . Meanwhile, the threshold voltage detector 350 reads information on the threshold voltage Vth of the phase driving switch DR from the memory 134 on the data driving circuit 120 or the compensation circuit 130 to obtain the threshold voltage Vth. It is possible to detect the amount of change due to the deterioration of

Also, the lookup table update unit 330 may increase the overdrive grayscale corresponding to the previous data having a grayscale value greater than 0 and the current data having a grayscale value of 0 according to the increase of the threshold voltage Vth. . That is, the data voltage corresponding to the increased overdriving grayscale data signal is greater than the sum voltage of the reference voltage Vref and the threshold voltage Vth1 before rising, and the reference voltage Vref and the increased threshold voltage Vth2. is less than the sum voltage of , so that the swing width of the previous and current data voltages can be reduced.

The embodiment according to the present invention reflects the deterioration characteristic of the threshold voltage of the driving switch and updates the lookup table for overdriving, thereby reducing the voltage swing width when changing the voltage from the previous data to the current data to improve the pixel charging characteristics. have.

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

Hereinafter, with reference to the drawings of an organic light emitting diode display according to an embodiment of the present invention will be described in detail. The embodiments introduced below are provided as examples so that the spirit of the present invention can be sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. And, in the drawings, the size and thickness of the device may be exaggerated for convenience. Like reference numbers refer to like elements throughout.

Advantages and features of the present invention, and a method for achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention pertains It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout. The sizes and relative sizes of layers and regions in the drawings may be exaggerated for clarity of description.

Reference to an element or layer to another element or “on” or “on” includes not only directly on the other element or layer, but also with other layers or other elements interposed therebetween. do. On the other hand, reference to an element "directly on" or "directly on" indicates that there are no intervening elements or layers.

Spatially relative terms "below, beneath", "lower", "above", "upper", etc. are one element or component as shown in the drawings. and can be used to easily describe the correlation with other devices or components. The spatially relative term should be understood as a term including different directions of the device during use or operation in addition to the directions shown in the drawings. For example, when an element shown in the figures is turned over, an element described as "beneath" or "beneath" another element may be placed "above" the other element. Accordingly, the exemplary term “below” may include both directions below and above.

The terminology used herein is for the purpose of describing the embodiments, and thus is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprise” and/or “comprising” refers to the presence of one or more other components, steps, operations, and/or elements mentioned. or addition is not excluded.

<Structure of organic light emitting diode>

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

The organic light emitting diode display may include an organic light emitting diode as shown in FIG. 1 .

The organic light emitting diode may include an organic compound layer (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 (Electron Injection layer, EIL) may be included. When a driving voltage is applied to the anode and cathode electrodes, holes passing through the hole transport layer (HTL) and electrons passing through the electron transport layer (ETL) are moved to the light emitting layer (EML) to form excitons, and as a result, the light emitting layer (EML) is produces visible light. In addition, in the organic light emitting diode, the type and concentration of the dopant of the light emitting layer (EML) are varied according to the color to be displayed. Blue) may be provided, and additionally, 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 may be provided. 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 digital video data. Such an organic light emitting diode display device is divided into a passive matrix method and an active matrix method using a TFT as a switching element. Among them, the active matrix method selects a pixel by selectively turning on the TFT, which is an active element, and maintains the light emission of the pixel with a voltage maintained in a storage capacitor.

<Equivalent circuit diagram of active matrix pixel>

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

Referring to FIG. 2 , the pixels of the organic light emitting diode display according to the embodiment of the present invention include an organic light emitting diode (OLED), a data line (D) and a gate line (G) crossing each other, and the pixel on the gate line (G). A scan switch (SW) for sequentially transferring data to pixels in a scan pulse (SP), a driving switch (DR) that generates a current by a voltage between the gate and source terminals, and a drive switch (DR) for storing data and maintaining it for a certain time A storage capacitor Cst is provided. The scan switch SW and the driving switch DR may be formed of an N-type MOS-FET. As described above, a structure composed of two transistors (SW, 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 its source electrode and the drain electrode. During the ON time period of the scan switch SW, the data voltage from the data line D passes through the source electrode and drain electrode of the scan switch SW to the gate electrode of the driving switch DR and the storage capacitor ( Cst) is applied. The driving switch DR controls the current flowing through the organic light emitting diode OLED according to the difference voltage Vgs between its gate electrode and the source electrode. The storage capacitor Cst maintains 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. The organic light emitting diode OLED implemented with the structure 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 shown in FIG. 2 is proportional to the current flowing through 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 driving switch DR, 'Vdata' is the data voltage, 'Vinit' is the initialization voltage, 'Ioled' is the driving current, 'Vth' is the threshold voltage of the drive switch (DR),

denotes a constant value determined by the mobility and parasitic capacitance of the driving switch DR, respectively. As shown in Equation 1, 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. Accordingly, the uniformity of the entire video image may be influenced by the characteristic deviation of the driving switch DR, that is, the threshold voltage deviation.

<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.

Referring to FIG. 3 , an organic light emitting diode display 100 according to an embodiment of the present invention includes a system board 123 , a display panel 116 , a gate driving circuit 118 , a data driving circuit 120 , and a timing controller. (124) may be provided.

The system board 123 may supply a timing signal including a vertical/horizontal synchronization signal, a dot clock signal, and a data enable signal, digital video data, and a power voltage Vcc to the timing controller 124 . The system board 123 may include a scaler circuit to adjust the resolution of 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 a low voltage differential signaling (LVDS) interface.

The display panel 116 corresponds to each other on a one-to-one basis to form m pairs of m data lines D1 to Dm, k sensing lines S1 to Sk, and n gate lines G1 to Gn and j. Pixels 122 formed at intersections of sensing control lines SC1 to SCj may be provided. Signal lines supplying the first driving power Vdd and the signal wirings supplying the second driving power Vss to each of the pixels 122 may be formed on the display panel 116 . Here, the first driving power Vdd and the second driving power Vss may be generated from the high potential driving voltage source VDD and the low potential driving voltage source VSS, respectively. The gate driving circuit 118 may generate a scan pulse SP in response to the gate control signal GDC from the timing controller 124 and sequentially supply the scan pulses SP to the gate lines G1 to Gn. Also, the gate driving circuit 118 may be controlled from the timing controller 124 to output the sensing control signal SCS, and a sensing switch in each pixel may be controlled by the sensing control signal SCS. It has been described that the gate driving circuit 118 outputs both the scan pulse SP and the sensing control signal SCS, but is not limited thereto, and is controlled by the timing controller 124 to generate the sensing control signal SCS. A separate sensing switch control driver capable of outputting may be provided. The data driving circuit 120 may be controlled by a data control signal DDC from the timing controller 124 and output a data voltage to the data lines D1 to Dm and a sensing voltage to the sensing lines S1 to Sk. can Each of the data lines D1 to Dm may be respectively connected to each pixel 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 may measure the sensing voltage on the sensing lines S1 to Sk. Specifically, by supplying the initialization voltage using one sensing line S1 to Sk, the sensing voltage using charging and floating as the initialization voltage can be detected. Although it has been described that the data driving circuit 120 can output or detect the data voltage and the sensing voltage, the present invention is not limited thereto, and a separate driver capable of outputting or detecting the sensing voltage may be provided.

<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, and this may be separately referred to as a sub-pixel. The sub-pixel 122 may include a scan switch SW, a driving 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 is a transistor for supplying data on the data line Dm to the sub-pixel 122 , and includes the data line Dm and the first It may be connected between the nodes N1. The driving switch DR is a transistor that regulates the current flowing in the organic light emitting diode OLED by the voltage between the first node N1 and the second node N2, which is its gate-source, and has a gate terminal It may be connected to the first node N1 , a source terminal may be connected to the second node N2 , and a drain terminal may be connected to the first driving power source Vdd. The sensing switch SEW is a transistor that initializes the second node N2 to detect the threshold voltage of the driving switch DR through the sensing line Sk, and controls sensing on the sensing control line SCj. It is controlled by the 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 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 the source terminal of the driving switch DR.

<Threshold voltage sensing and compensation>

5 is a waveform diagram illustrating voltage waveforms on first and second nodes when sensing a threshold voltage, and FIGS. 6 to 8 are diagrams illustrating an operation of a pixel when sensing a threshold voltage.

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

(1) Initialization period: t1

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

(2) Source follower operation period: t2

5 and 7, in the source follower driving period t2, the sensing line Sk is floating (by the sampling signal Sam signal, the sensing line Sk is electrically open with the ADC 220, The sensing line Sk and the reference voltage generator 133 are electrically open by the initialization control signal Spre), the scan switch SW and the sensing switch SEW maintain turn-on, and the storage capacitor Cst ), that is, a current flows in the driving switch DR using the high potential power Vdd as an energy source by the voltage Vgs between the gate and source terminals of the driving switch DR. In addition, as the current flowing through the driving switch DR charges the second node N2 , the voltage on the second node N2 increases. At this time, since Vgs of the driving switch DR decreases, the current flowing through the driving switch DR also decreases. In addition, when Vgs reaches the threshold voltage of the driving switch DR, no current flows through the driving switch DR, so that the voltage on the second node N2 is constantly maintained.

(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 signal, and the voltage on the second node N2 is is detected and converted into a digital signal. Then, when the compensation data signal to be supplied to the data line Dm is generated when the characteristics of the driving switch are compensated, 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. In addition, the detected threshold voltage Vth may be provided to the timing controller 124 , and a lookup table for overdriving may be updated by detecting a variation amount of the threshold voltage Vth.

<Internal structure of data driving circuit or compensation circuit>

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

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

When the threshold voltage is sensed in response to the initialization control signal Spre, the initialization switch SW20 is turned on during the initialization period to sense the reference voltage Vref supplied from the reference voltage generator 133 of the pixel 122 . It 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 the high-level sampling signal Sam when the threshold voltage is sensed 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 .

Meanwhile, the sensing lines S1 to Sk may 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 into a digital value and provide it to the memory 134 , and the memory 134 may store the digital value. By storing , information on the threshold voltage of the driving switch DR in the pixel 122 may be stored.

The control unit 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 , and the timing controller 124 provides the data driver 120 . ) may be controlled to 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 may be considered.

Meanwhile, the ADC 132 may be a separate configuration separated from the sensing circuit 131 or may be included in the sensing circuit 131 to form a single configuration.

Meanwhile, although it has been described that the data driving circuit 120 includes a circuit for sensing the characteristics of the driving switch DR, it is not limited thereto, and sensing the characteristics of the driving switch DR and sensing the characteristics of the organic light emitting diode (OLED). The compensation circuit 130 may be provided on a separate substrate.

<Internal structure of timing controller>

10 is a block diagram of overdriving provided in the timing controller.

Referring to FIG. 10 , the timing controller 124 outputs the currently input data as it is when overdriving is not performed with the field memory 310 for storing data of the previous field, and when overdriving is performed, a lookup table Based on the threshold voltage with respect to the driving switch DR sensed from the data selection output unit 320 and the compensation circuit 130 for selecting and outputting the output value of 330, the degree of shift of the threshold voltage, that is, the amount of variation It may include a threshold voltage detector 350 to detect and a lookup table updater 360 to update the lookup table 330 based on the threshold voltage variation amount from the threshold voltage detector 350 . Meanwhile, the threshold voltage detector 350 reads information on the threshold voltage Vth of the phase driving switch DR from the memory 134 on the data driving circuit 120 or the compensation circuit 130 to obtain the threshold voltage Vth. It is possible to detect the amount of change due to the deterioration of

Specifically, the lookup table 330 may have overdriven grayscale values corresponding to the previous data signal and the current data signal. That is, when the grayscale value of the previous data signal is 10 grayscales and the grayscale value of the current data signal is 15 grayscales, the overdriven grayscale values corresponding to the previous and current data signals may be 18 grayscales. In addition, when the grayscale value of the previous data signal is 15 grayscales and the grayscale value of the current data signal is 10 grayscales, the overdriven grayscale values corresponding to the previous and current data signals may be 7 grayscales. As described above, when the grayscale value decreases from the previous data signal to the current data signal, overdriving to a grayscale lower 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, since there is no grayscale less than 0 grayscale, the overdriven grayscale value is 0 grayscale or a threshold voltage (Vth) variation to be described later Based on , a grayscale higher than 0 grayscale may be obtained. In this case, since the substantially overdriven grayscale is not lower than the 0 grayscale of the current data, it can be said that the overdrive has not been performed.

However, when the overdrive grayscale value is set to a grayscale higher than 0 grayscale based on the threshold voltage Vth variation, the current in the analog voltage corresponding to the previous data signal and the data voltage output from the data driving circuit 120 The swing width of the analog voltage corresponding to the data signal and the data voltage output from the data driving circuit 120 may be reduced. That is, the previous data output from the actual data driving circuit 120 is updated as the grayscale values that are greater than 0 and the overdrive grayscale corresponding to the current data of the zero grayscale and the previous data having a grayscale value greater than 0 are updated to a grayscale value greater than or equal to the zero grayscale. and a swing width of the current data voltage may be reduced.

In addition, when the threshold voltage Vth of the driving switch DR rises, the overdrive grayscale corresponding to the previous data having a grayscale value greater than 0 and the current data having a grayscale value of 0 may be increased (see details on this) The contents will be described later).

<shift of threshold voltage>

11 is a graph illustrating a threshold voltage variation of a driving switch. And FIG. 12 is a view showing the threshold voltage sensing of the driving switch, the update of the lookup table, and the display period in time series.

As the driving switch DR deteriorates, the threshold voltage Vth may shift accordingly, and may be restored to an original state when the driving switch DR is not driven. However, depending on the material used to manufacture the driving switch DR, the threshold voltage shift due to deterioration and the threshold voltage shift due to recovery may vary, so that the threshold voltage is shifted in a positive or negative direction. can

Meanwhile, according to Equation 1 described above, a data voltage value for grayscale expression may be changed according to a shift of the threshold voltage.

According to Equation 1, the current Ioled flowing through the organic light emitting diode OLED is the gate of the driving switch DR, which is the voltage difference between the first and second nodes N1 and N2 on the pixel 122 of FIG. 4 , and It can be seen that it may vary depending on the threshold voltage Vth of the driving switch DR as well as the voltage difference Vgs between the source terminals.

[Table 1]

For example, when the reference voltage Vref is supplied to the second node N2 and the threshold voltage Vth of the driving switch DR has a positive value, for grayscale expression, the first node N1 It is assumed that the voltage of should be as shown in Table 1.

- 1st time period

Specifically, by sensing the threshold voltage Vth of the driving switch DR on the display panel 116 during the first time period T1 , the first threshold voltage which is information of the threshold voltage Vth of the driving switch DR Based on (Vth1), a compensated data voltage as shown in Table 1 may be generated.

In this case, the first threshold voltage Vth that is information of the threshold voltage Vth of the driving switch DR sensed by the threshold voltage Vth of the driving switch DR on the display panel 116 during the first time period T1 A compensated data voltage may be generated based on Vth1). In addition, the lookup table 330 on the timing controller 124 may be updated by the lookup table updater 360 that receives the output signal from the threshold voltage detector 350 that detects the amount of change in the threshold voltage.

[Table 2]

At this time, it is assumed that the driving switch DR is not deteriorated. In addition, it is assumed that the lookup table for overdriving on the lookup table is as shown in Table 2. And in Table 2, X may have an arbitrary grayscale value, and A, B, C, D, E, and F may have 0 grayscale.

- 2nd time period

In addition, a second time period T2, which is a time period between the first and third time periods T1 and T3, is a display period, and during the second time period T2, based on the first threshold voltage Vth1, video 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 from 0V in order to express 0 grayscale, Assuming that the voltage difference Vgs between the gate and source terminals of the driving switch DR should be 1V or more and less than 2V in order to express the 10 grayscale, the data voltage of the first node N1 is the reference voltage Vref and The threshold voltage Vth may be less than the sum voltage (Vref+Vth)+1V from the sum voltage (Vref+Vth)+2V, and the voltage difference between the gate and the source terminals of the driving switch DR to express 20 grayscales. Assuming that (Vgs) should be 3V or more and less than 5V, the data voltage of the first node N1 is the sum voltage (Vref+Vth)+3V of the reference voltage Vref and the threshold voltage Vth to the sum voltage ( Vref+Vth)+5V can be less.

Also, it is assumed that the data voltage increases by 0.1V from 0 to 10 grayscales to express each grayscale.

However, such a data voltage value is merely an example and is not limited thereto, and may vary.

- 3rd time period

Also, by sensing the threshold voltage Vth of the driving switch DR on the display panel 116 during the third time period T3 , the second threshold voltage Vth2 which is information of the threshold voltage Vth of the driving switch DR ) can be obtained. At this time, it is assumed that the threshold voltage Vth increases so that the second threshold voltage Vth2 is 0.3V higher than the first threshold voltage Vth1. In addition, the lookup table update unit 360 may update the lookup table 330 based on the information on the second threshold voltage Vth2 .

[Table 3]

And it is assumed that the updated lookup table 330 is as shown in Table 3. And as shown in Table 3, A, B, C, D, E, and F may have 0 to 3 grayscales.

- 4th time period

During the fourth time period T4 after updating the lookup table 330, the image display is displayed based on the first threshold voltage Vth1 information sensed during the first time period T1, that is, based on Table 1. A data voltage corresponding to each gray level may be supplied to the first node N1.

Also, during the fourth time period T4, for example, when the previous data is 20 grayscale and the current data is 0 grayscale, the data voltage during the previous data may be any one of Vref+Vth1+3V to Vref+Vth1+5V. It can have a voltage value. In addition, the current data refers to the updated lookup table 330 of Table 3, and refers to the data voltage corresponding to the 0 to 3 gray scale in Table 1, which is any one of a voltage of 0V or more and Vref+Vth1+0.3V. voltage can be output. Even if the data voltage is any one of the voltages above 0V and less than Vref+Vth1+0.3V, since the threshold voltage Vth of the current driving switch DR is changed to the second threshold voltage Vth2, the table Even if any one of a voltage of 0V or more and less than Vref+Vth1+0.3V, which is a data voltage corresponding to 0 to 3 grayscales in phase 1, is output, 0 grayscale can be expressed.

On the other hand, preferably, the grayscale values of A, B, C, D, E, and F in Table 2 are 1 to 3 grayscales among 0 to 3 grayscales. In this case, any one of the voltages of Vref+Vth1 or more and Vref+Vth1+0.3V, which is the current data voltage, from any one of the voltages below Vref+Vth1+3V and Vref+Vth1+5V, which are 20 grayscales, which are previous data. Since it can vary with one voltage, a swing width smaller than the swing width with the current data voltage corresponding to 0 gray is possible, so that the charging characteristic can be improved.

- 5th time period

[Table 5]

Also, by sensing the threshold voltage Vth of the driving switch DR on the display panel 116 during the fifth time period T5 , the third threshold voltage Vth3 which is information of the threshold voltage Vth of the driving switch DR ), a compensated data voltage can be generated as shown in Table 4. In this case, all of the third threshold voltage Vth3 due to deterioration of the driving switch DR may be reflected in the data voltage according to the compensation of the data voltage. Accordingly, in the lookup table, the grayscale values of A, B, C, D, E, and F are changed back to grayscale 0 and may be as shown in Table 2 (however, any grayscale value of X may be different).

Meanwhile, as shown in FIG. 11 , the threshold voltage Vth may be periodically sensed. In addition, 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 the threshold voltage Vth at least once.

On the other hand, based on the sensed threshold voltage Vth, when the display device 100 is powered on, for a certain time after the power is off, or at a specific time while the display device 100 is driven, Sensing the threshold voltage (Vth) for updating the lookup table 330 may be performed periodically, sensing the threshold voltage (Vth) for compensating image data, and sensing the threshold voltage (Vth) for updating the lookup table 330 . can be made by the method described with reference to FIGS. 6 to 8 .

Meanwhile, the previous data and the current data may be data applied to 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 next gate line of the previous gate line Gn-1. It may be a data signal applied to the pixel corresponding to (Gn). As described above, by performing overdriving for each line and updating the lookup table 330 based on the threshold voltage Vth of the driving switch DR, the swing width of the data voltage that can be changed for each line is reduced. Charging characteristics can be improved.

In addition, 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 charging characteristics due to the load of the display panel 116 .

As described above, according to the increase of the threshold voltage Vth of the driving switch DR, the previous data of the grayscale value greater than 0 and the overdriven grayscale corresponding to the current data of the zero grayscale on the lookup table 330 are increased. Compensation data according to a data voltage that fluctuates to a driving gradation and corresponds to the data signal of the increased overdriving gradation is equal to or less than the sum voltage of the reference voltage and the increased threshold voltage, more preferably, the sensed threshold voltage Vth The data voltage corresponding to the data signal of the increased overdriving grayscale is higher than the data voltage corresponding to the zero grayscale before generating , and lower than the voltage of the sum of the reference voltage and the increased threshold voltage It is greater than the sum voltage of the reference voltage Vref and the threshold voltage Vth1 before rising and is less than the sum voltage of the reference voltage Vref and the rising threshold voltage Vth2, thereby reducing the swing width of the previous and current data voltages. can do.

In the detailed description of the present invention described above, although it has been described with reference to preferred embodiments of the present invention, those skilled in the art or those having ordinary knowledge in the technical field of the present invention described in the claims to be described later It will be understood that various modifications and variations of the present invention can be made without departing from the spirit and scope of the present invention. Accordingly, 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
116 display panel
122 pixels
118 gate driving circuit
120 data driving circuit
123 system board
124 timing controller
130 compensation circuit
131 sensing circuit
132 analog-to-digital converter
133 Reference voltage generator
134 Memory on the compensation circuit
135 control
Memory on 310 Timing Controller
330 lookup table
350 Threshold voltage fluctuation detection unit
360 lookup table update

Claims (11)

a display panel including a driving switch for controlling a current flowing through the organic light emitting diode;
a timing controller having a lookup table including overdrive grayscales corresponding to grayscales of previous and current data signals; and
a data driving circuit for outputting a data voltage corresponding to the overdriven grayscale data signal to the driving switch;
the overdriven grayscale is set based on a threshold voltage of the driving switch;
The timing controller detects a variation amount of the threshold voltage, and updates the lookup table based on the detected variation amount of the threshold voltage. According to claim 1,
The timing controller is
a memory for storing the previous data;
a data selection output unit for outputting any one of the current data or data having the overdriven grayscale from the lookup table according to whether overdriving is performed;
a threshold voltage variation detecting unit for detecting a variation in the threshold voltage from the threshold voltage of the driving switch; and
The organic light emitting diode display device further comprising a lookup table updater for updating the lookup table based on the variation amount of the threshold voltage. 3. The method of claim 2,
The lookup table update unit,
An organic light emitting diode display for updating an overdrive grayscale corresponding to previous data having a grayscale value greater than zero and current data having a grayscale value of zero. 4. The method of claim 3,
The lookup table update unit,
The organic light emitting diode display device for increasing the overdriven grayscale corresponding to the previous data of the grayscale value greater than 0 and the current data of the zero grayscale according to the increase of the threshold voltage. 5. The method of claim 4,
The display panel is
a scan switch for providing a data signal on a data line to a gate terminal of the driving switch in response to a scan pulse on the gate line;
A sensing switch for supplying a reference voltage on a sensing line to a source terminal of the driving switch in response to a sensing control signal,
As the threshold voltage rises, the previous data of the grayscale value greater than 0 and the overdrive grayscale corresponding to the current data of the zero grayscale on the lookup table change to an increased overdriving grayscale;
The data voltage corresponding to the data signal of the increased overdriving grayscale is equal to or less than a sum voltage of the reference voltage and the increased threshold voltage. An organic light emitting diode, a driving switch controlling the current flowing through the organic light emitting diode, a scan switch providing a data signal on a data line to a gate terminal of the driving switch in response to a scan pulse on the gate line, and sensing in response to a sensing control signal a display panel including a sensing switch for supplying a reference voltage on a line to a source terminal of the driving switch;
a timing controller having a lookup table including overdrive grayscales corresponding to grayscales of previous and current data signals; and
a data driving circuit for outputting a data voltage corresponding to the overdriven grayscale data signal to the driving switch;
The overdriven gray level is set based on the sensed threshold voltage of the driving switch;
The timing controller detects a variation amount of the threshold voltage, and updates the lookup table based on the detected variation amount of the threshold voltage. 7. The method of claim 6,
Gate and source terminals of the driving switch are initialized by turning on the scan switch and the sensing switch,
The voltage of the source terminal of the driving switch is increased by the floating of the sensing line until the potential difference between the gate and the source terminal of the driving switch becomes the threshold voltage of the driving switch,
An organic light emitting diode display device for storing a threshold voltage of the driving switch by detecting a source terminal voltage of the driving switch. 8. The method of claim 7,
a threshold voltage variation detection unit configured to detect a variation in the threshold voltage from the stored threshold voltage of the driving switch; and
The organic light emitting diode display device further comprising a lookup table updater for updating the lookup table based on the variation amount of the threshold voltage. 9. The method of claim 8,
The lookup table update unit,
An organic light emitting diode display for updating an overdrive grayscale corresponding to previous data having a grayscale value greater than zero and current data having a grayscale value of zero. 9. The method of claim 8,
As the threshold voltage rises, the overdrive grayscale corresponding to the previous data having a grayscale value greater than 0 and the current data having a grayscale value of 0 on the lookup table change to an increased overdriving grayscale;
The data voltage corresponding to the data signal of the increased overdriving grayscale is equal to or less than a sum voltage of the reference voltage and the increased threshold voltage. 11. The method of claim 10,
A data voltage corresponding to the data signal of the increased overdriving grayscale is greater than a sum voltage of the reference voltage and a threshold voltage before rising, and is less than or equal to a sum voltage of the reference voltage and the increased threshold voltage.

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