KR102331040B1 - Organic light emitting diode display panel and drving method thereof - Google Patents

Abstract

In an organic light emitting diode display panel according to an embodiment of the present invention, the sensing switch of the n-th sub-pixel among the sub-pixels arranged in the vertical direction of the display panel is a scan switch of the n-1 th sub-pixel that is the previous stage of the n-th sub-pixel It can be controlled by a scan pulse on the gate line connected to As described above, by using the gate line of the adjacent sub-pixel on the vertical line as a line for driving the sensing switch, the aperture ratio according to the decrease in the line can be increased.

Description

Organic light emitting diode display panel and its driving method

The present invention relates to an organic light emitting diode display panel and a driving method thereof.

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.

Because PDP has a simple structure and manufacturing process, it is attracting attention as the most advantageous display device for light, thin, and large screen. TFT LCD to which a thin film transistor (hereinafter referred to as "TFT") is applied as a switching device is the most widely used flat panel display device, but since it is a light emitting device, it has a narrow viewing angle and low response speed. In contrast, the electroluminescent device is roughly classified 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. Brightness and viewing angle are great advantages.

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.

At this time, since the current of the organic light emitting diode is greatly affected by the threshold voltage (Vth) and the mobility (k) of the driving transistor, it is necessary to accurately measure the threshold voltage (Vth) and the mobility (k) to compensate for these. the need has grown

To this end, a lot of research has been done on the internal compensation method and the external compensation method. However, in the internal compensation method, the number of elements constituting a pixel increases in order to secure compensation performance, and thus, there is a problem in securing the aperture ratio.

In addition, in the case of the external compensation method, real-time compensation is difficult, so there is a problem that the driving transistor is vulnerable to afterimage.

An embodiment of the present invention provides an organic light emitting diode display panel capable of accurately controlling a current flowing through an organic light emitting diode by detecting a threshold voltage of a driving transistor and a driving method thereof.

In addition, an embodiment of the present invention may provide an organic light emitting diode display panel capable of increasing the accuracy of compensation by detecting the mobility of a driving transistor and a driving method thereof.

In addition, the embodiment according to the present invention may provide an organic light emitting diode display panel and a driving method thereof for securing an aperture ratio by using a pixel structure in which a gate line and a sensing control line are shared between adjacent pixels.

In addition, the embodiment according to the present invention may provide an organic light emitting diode display panel capable of securing compensation performance by using an external compensation method and an internal compensation method in parallel, and a driving method thereof.

In addition, in the embodiment according to the present invention, when the threshold voltage is externally compensated and the mobility is compensated for by the internal compensation scheme, compensation for mobility, which has a great influence on the driving current deviation during real-time driving, can be performed in real time. It is also possible to provide an organic light emitting diode display panel and a driving method thereof.

In the organic light emitting diode display panel according to an embodiment of the present invention, an aperture ratio according to a reduction in lines can be increased by using a gate line of an adjacent sub-pixel on a vertical line as a line for driving a sensing switch.

The method of driving an organic light emitting diode display panel according to an embodiment of the present invention further includes a re-initialization step, so that re-initialization can be performed for each sub-pixel immediately before the compensation time, thereby increasing the accuracy of compensation.

According to the embodiment of the present invention, the current flowing through the organic light emitting diode can be accurately controlled by detecting the threshold voltage of the driving transistor, the accuracy of compensation can be improved by detecting the mobility of the driving transistor, and the gate line and sensing between adjacent pixels It is possible to provide an organic light emitting diode display panel capable of securing an aperture ratio by using a pixel structure sharing a control line and securing compensation performance by using an external compensation method and an internal compensation method in parallel, and a driving method thereof.

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 of an active matrix type.
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 of signals of sub-pixels according to a method of compensating for mobility.
6 is a waveform diagram of signals of first to third sub-pixels according to a method of compensating for mobility.
7 is a diagram illustrating signal waveforms in a method of compensating for both a threshold voltage and mobility of a driving switch.

Hereinafter, an organic light emitting diode display panel and a driving method thereof according to an embodiment of the present invention will be described in detail with reference to the drawings. 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 various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art 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 terms should be understood as terms including different orientations of the device during use or operation in addition to the orientation shown in the drawings. For example, if 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. As used herein, 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 electrode and the cathode electrode, 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 the organic light emitting diode display, pixels including such organic light emitting diodes are arranged in a matrix form, and the brightness of the pixels selected by a scan pulse is controlled according to the gradation of digital video data. Such an organic light emitting diode display 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 type pixel>

2 is a circuit diagram equivalently showing one pixel in an organic light emitting diode display of an active matrix type.

Referring to FIG. 2 , the pixels of the active matrix organic light emitting diode display device include an organic light emitting diode (OLED), a data line (D) and a gate line (G) crossing each other, and a scan for sequentially transferring data to the pixel A switch SW, a driving switch DR, and a storage capacitor Cst for storing and maintaining data for a predetermined time are 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 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, thereby conducting 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 is applied to the gate electrode and the storage capacitor Cst of the driving switch DR via the source electrode and the drain electrode of the scan switch SW. is authorized 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

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' denotes a threshold voltage of the driving switch DR, and 'k' denotes a constant value determined by 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 and the mobility k of the driving switch DR. Accordingly, the uniformity of the entire video image is affected by the characteristic deviation of the driving switch DR, that is, the deviation between the mobility k and the threshold voltage Vth. Meanwhile, the driving switch DR for the organic light emitting diode display may be manufactured based on amorphous silicon (s-Si) or low-temperature polycrystalline silicon (LTPS). Although the amorphous silicon driving switch has very uniform characteristics, there is a problem in stability such as threshold voltage shift. And it is difficult to directly build the driving circuit on the panel due to the low mobility. On the other hand, low-temperature polycrystalline silicon driving switches have relatively high stability and high mobility, but there is a large deviation between pixels in threshold voltage and mobility characteristics due to the irregularity of the drain boundary.

<Block diagram of organic light emitting diode display device>

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

Referring to FIG. 3 , the organic light emitting diode display according to the embodiment of the present invention may include a display panel 116 , a gate driving circuit 118 , a data driving circuit 120 , and a timing controller 124 .

The display panel 116 has an intersection region of m data lines D1 to Dm, k sensing lines S1 to Sk, and n gate lines G1 to Gn, which correspond to each other on a one-to-one basis to form m pairs. It may include m×n pixels 122 formed in . Also, the display panel 116 may include j number of sensing control lines SC1 to SCj, and in the case of the first sensing control line SC1 among the sensing control lines SC1 to SCj, the gate driving circuit 118 ) and the pixels on the first horizontal line are connected to each other, but in the case of the remaining sensing control lines SC2 to SCj, the gate lines G1 to Gn and the remaining pixels may be connected to each other.

That is, the gate line and the sensing control line between adjacent pixels may be connected to each other.

Signal wirings 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.

In addition, the gate driving circuit 118 may be controlled by the timing controller 124 to output the sensing control signal SCS to the first sensing control line SC1 , and by the sensing control signal SCS, the first horizontal A sensing switch in the pixel on the line can be controlled. In addition, sensing switches of pixels other than the pixel on the first horizontal line may be controlled by a scan pulse provided from a gate line of the gate driving circuit 118 .

As described above, since the sub-pixels on the first horizontal line positioned at the top of the display panel 116 do not have previous sub-pixels, as a control line for driving their sensing switches, the gate driving circuit 118 performs one sensing control. Since only the line SC1 may be provided, an aperture ratio according to a decrease in the number of lines may be secured.

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 measure the sensing voltage on the sensing lines S1 to Sk. Specifically, by supplying an initialization voltage using one sensing line S1 to Sk, a sensing voltage using charging and floating can be detected as the initialization voltage.

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 pixels, and this may be separately referred to as a sub-pixel.

Also, when sub-pixels connected to the first gate line G1 are referred to as sub-pixels on the first horizontal line, sub-pixels connected to the n-th gate line Gn may be referred to as sub-pixels on the n-th horizontal line. . In addition, when sub-pixels connected to the first data line D1 are referred to as sub-pixels on the first vertical line, sub-pixels connected to the m-th data line Dm may be referred to as sub-pixels on the m-th vertical line. .

Referring to FIG. 4 , the display panel 116 may include first to third sub-pixels 122n-1, 122n, and 122n+1 sequentially positioned on a vertical line. The first to third sub-pixels 122n-1, 122n, and 122n+1 may be any one of red, green, blue, and white pixels.

The first sub-pixel 122n-1 includes a first scan switch SWn-1, a first driving switch DRn-1, a first sensing switch SEWn-1, an organic light emitting diode (OLED), and a storage capacitor. (Cst) may be included.

The first scan switch SWn-1 is controlled by the scan pulse SP on the first scan line Gn-1 and supplies data on the data line Dm to the first sub-pixel 122n-1. This transistor may be connected between the data line Dm and the first node N1.

The first driving switch DRn-1 is a transistor that controls the current flowing through the organic light emitting diode OLED by the voltage between the first node N1 and the second node N2, which is its gate-source, The gate terminal may be connected to the first node N1 , 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 first sensing switch SEWn-1 is a transistor that initializes the second node N2 and controls the threshold voltage of the first driving switch DRn-1 to be detected through the sensing line Sk. It is controlled by the scan pulse SP on the gate line Gn-2 of the sub-pixel 122n-2 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 first driving switch DRn-1.

The second sub-pixel 122n may include a second scan switch SWn, a second driving switch DRn, a second sensing switch SEWn, an organic light emitting diode OLED, and a storage capacitor Cst. .

The second scan switch SWn is a transistor controlled by the scan pulse SP on the second scan line Gn and supplies data on the data line Dm to the second sub-pixel 122n. It may be connected between (Dm) and the first node (N1).

The second driving switch DRn is a transistor that controls the current flowing through the organic light emitting diode OLED by the voltage between the first node N1 and the second node N2, which are its gate-source, and has a gate terminal. 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 second sensing switch SEWn is a transistor that initializes the second node N2 and controls the threshold voltage of the second driving switch DRn through the sensing line Sk to be detected. It is controlled by the scan pulse SP on the gate line Gn-1 of the pixel 122n-1 and may be connected between the second and third nodes N2 and N3.

The third sub-pixel 122n+1 includes a third scan switch SWn+1, a third driving switch DRn+1, a third sensing switch SEWn+1, an organic light emitting diode (OLED), and a storage capacitor. (Cst) may be included.

The third scan switch SWn+1 is controlled by the scan pulse SP on the third scan line Gn+1 and supplies data on the data line Dm to the third sub-pixel 122n+1. This transistor may be connected between the data line Dm and the first node N1.

The third driving switch DRn+1 is a transistor that regulates the current flowing through the organic light emitting diode OLED by the voltage between the first node N1 and the second node N2, which is its gate-source, The gate terminal may be connected to the first node N1 , 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 third sensing switch SEWn+1 is a transistor that controls the second node N2 to detect the threshold voltage of the third driving switch DRn+1 through the initialization and sensing line Sk. It may be controlled by the scan pulse SP on the gate line Gn of the previous sub-pixel 122n on the line and may be connected between the second and third nodes N2 and N3.

As described above, the sensing switch SEWn of the n-th sub-pixel 122n on the vertical line may be connected to the gate line Gn-1 of the previous sub-pixel 122n-1. Thus, by the scan pulse on the gate line Gn-1 of the previous sub-pixel 122n-1, the scan switch SWn-1 of the previous sub-pixel 122n-1 and the sensing switch (SWn-1) of the n-th sub-pixel 122n SEWn) can be driven together. As described above, by using the gate line G of the adjacent sub-pixel 122 on the vertical line as the sensing line SC for driving the sensing switch SEW, the aperture ratio according to the line reduction can be increased.

Meanwhile, in FIG. 4 , the first to third nodes N1 to N3 of the second sub-pixel 122n may be referred to as fourth to sixth nodes N4 to N6 , and the third sub-pixel 122n+1 The first to third nodes N1 to N3 of may be referred to as seventh to ninth nodes N7 to N9.

<External compensation method of threshold voltage>

When the threshold voltage is externally compensated, a data signal for compensating the threshold voltage is applied to the gate terminal of the driving switch DR in the sub-pixel 122 . And the voltage on the second node N2 in the floating state rises by the current flowing in the driving switch DR, and the current flowing in the driving switch DR is the gate terminal and the source terminal of the driving switch DR. When the voltage between them becomes the threshold voltage Vth of the driving switch DR, the flow is stopped. At this time, when the voltage on the second node N2 is detected through the sensing line Sk and compared with the input data signal, the threshold of the driving switch DR is Vg(=Vdata)-Vs(N2 node voltage)=Vth. The voltage Vth can be detected. As described above, the threshold voltage may be compensated using an external compensation method, and the threshold voltage using the external compensation method may be performed in the initial driving stage of the organic light emitting diode display device.

< How to compensate for mobility>

5 is a waveform diagram of signals of sub-pixels according to a method of compensating for mobility.

Mobility, which will be described below, may be compensated for using an internal compensation method. This internal compensation method may be performed in real time in the driving stage of the organic light emitting diode display.

Referring to FIG. 5 , if the n-th sub-pixel 122n is described as a reference, high logic scan pulses SP are supplied to all the scan switches SW in the initialization period Tin, so all the sub-pixels 122 The first and second nodes N1 and N2, which are gate and source terminals of the driving switch DR of , are initialized, respectively. Thereafter, in the n-th sub-pixel 122n, the second node N2, which is the source terminal of the second driving switch DRn, is connected to the first scan switch SWn-1 of the n-th sub-pixel 122n-1. When the high logic scan pulse SP is supplied, the first node N1 is initialized once again and is the gate terminal of the second driving switch DRn of the n-th sub-pixel 122n. The data voltage for image display on the data line Dm is written by turning on, and the voltage on the second node N2 is increased according to the current capability of the second driving switch DRn while being written. As the degree changes, the mobility (k) is compensated.

6 is a waveform diagram of signals of first to third sub-pixels according to a method of compensating for mobility.

A method of compensating for mobility of the first to third sub-pixels 122n-1, 122n, and 122n+1 on a vertical line of the display panel 116 will be described with reference to FIG. 6 .

<First time period (T1)>

During the first time period T1, a high logic scan pulse SP is supplied to all the gate lines Gn-1, Gn, and Gn+1, so that all the scan switches SWn-1, SWn, SWn+1 and all the scan switches SWn-1, SWn, SWn+1 and all When the sensing switches SEWn-1, SEWn, and SEWn+1 are turned on, the first and second nodes N1 and N2 that are gate and source nodes of all the driving switches DRn-1, DRn, and DRn+1 are initialized. .

At this time, the first node N1 is initialized by the voltage on the data line Dm, and the second node N2 is initialized by the voltage on the sensing line Sk.

<Second time period (T2)>

During the second time period T2, the first scan switch SWn-1 and the second sub-pixel 122n are formed by the high logic scan pulse SP applied to the first scan switch SWn-1. The second sensing switch SEWn may be turned on. The first node N1 of the first sub-pixel 122n-1 is re-initialized by the data voltage on the data line Dm as the first scan switch SWn-1 is turned on, and the second sub-pixel ( The second node N2 on 122n may be re-initialized by the initialization voltage on the sensing line Sk as the second sensing switch SEWn is turned on.

Also, when a data signal (expressed as a high logic signal in the drawing) for displaying an image changed from a voltage for re-initialization is received on the data line Dm, the first node N1 of the first sub-pixel 122n-1 ) increases, and the voltage of the second node N2 of the first sub-pixel 122n-1 in a floating state also increases the first driving switch DRn-1 of the first sub-pixel 122n-1. ) rises by the current flowing through it. In this case, the amount of increase in the voltage on the second node N2 of the first sub-pixel 122n-1 depends on the characteristics of the first driving switch DRn-1 and the mobility of the first driving switch DRn-1. may vary depending on

<Third time period (T3)>

After the second time period T2, the first sub-pixel 122n-1 may enter the emission period, and during the third time period T3, a high logic scan pulse (SWn) applied on the second scan switch SWn SP) may turn on the second scan switch SWn and the third sensing switch SEWn+1 on the third sub-pixel 122n+1. The first node N1 of the second sub-pixel 122n is re-initialized by the data voltage on the data line Dm as the second scan switch SWn is turned on, and the third sub-pixel 122n+1 The second node N2 of the phase may be re-initialized by the initialization voltage on the sensing line Sk as the third sensing switch SEWn+1 is turned on.

Also, when a data signal (expressed as a high logic signal in the drawing) changed from a voltage for re-initialization is received on the data line Dm, the voltage of the first node N1 of the second sub-pixel 122n rises and , the voltage of the second node N2 of the second sub-pixel 122n in the floating state also increases by the current flowing through the second driving switch DRn of the second sub-pixel 122n. In this case, the amount of increase of the voltage on the second node N2 of the second sub-pixel 122n may vary according to the mobility of the second driving switch DRn.

<4th time period (T4)>

During the fourth time period T4 , the third sub-pixel 122n+1 may operate in the same manner as that of the second sub-pixel 122n during the aforementioned third time period T3 .

According to the aforementioned mobility compensation scheme, the mobility of the driving switches DR of all sub-pixels 122 may be compensated. Referring to Equation 2, in the case of the driving switch DR having a large mobility k, the voltage on the second node N2 rises quickly and the voltage Vgs between the gate and the source of the driving switch DR is small. lose

Equation 2

That is, in Equation 2, the mobility k and the voltage Vgs between the gate and the source of the driving switch DR are in inverse proportion to the mobility k of the current Ioled flowing through the driving switch DR. can reduce the impact on

<Threshold voltage and mobility compensation method>

7 is a diagram illustrating signal waveforms in a method of compensating for both a threshold voltage and mobility of a driving switch.

Referring to FIG. 7 , the threshold voltage and mobility of the driving switches DR of all sub-pixels 122 may be compensated for together using the internal compensation method.

<First time period (T1)>

During the first time period T1, a high logic scan pulse SP is supplied to all the gate lines Gn-1, Gn, and Gn+1, so that all the scan switches SWn-1, SWn, SWn+1 and all the scan switches SWn-1, SWn, SWn+1 and all When the sensing switches SEWn-1, SEWn, and SEWn+1 are turned on, the first and second nodes N1 and N2 that are gate and source nodes of all the driving switches DRn-1, DRn, and DRn+1 are initialized. .

As described above, the gate and source terminals N1 and N2 of the driving transistors DR of all sub-pixels 122 may be initialized at once to increase the accuracy of compensation.

<Second time period (T2)>

During the second time period T2, the first scan switch SWn-1 and the second sub-pixel 122n are formed by the high logic scan pulse SP applied to the first scan switch SWn-1. The second sensing switch SEWn may be turned on. A first data voltage for compensating a threshold voltage on the data line Dm is applied to the first node N1 of the first sub-pixel 122n-1 as the first scan switch SWn-1 is turned on; The second node N2 on the second sub-pixel 122n may be re-initialized by the initialization voltage on the sensing line Sk as the second sensing switch SEWn is turned on.

Also, when a changed first data signal (represented as a high logic signal in the drawing) is input on the data line Dm, the voltage of the first node N1 of the first sub-pixel 122n-1 increases and floats. The voltage of the second node N2 of the first sub-pixel 122n-1 in the (floating) state also increases by the current flowing through the first driving switch DRn-1 of the first sub-pixel 122n-1. . In this case, the voltage on the second node N2 of the first sub-pixel 122n-1 may increase by Vg-Vth by the threshold voltage Vth of the first driving switch DRn-1. And this process is continued until little current flows in the first driving switch DRn-1, and the operation is finished when the first driving switch DRn-1 is turned off. And the threshold voltage Vth of the first driving switch DRn-1 is stored in the storage capacitor Cst. In this case, the voltage on the second node N2 of the first sub-pixel 122n-1 may vary according to the threshold voltage Vth of the first driving switch DRn-1. For example, when the threshold voltage Vth of the first driving switch DRn-1 is large, the amount of increase of the voltage on the second node N2 is small. In addition, since the amount of increase of the voltage on the second node N2 is small, the voltage Vgs between the gate and the source terminal of the first driving switch DRn-1 becomes large. Therefore, according to Equation 2, when the threshold voltage Vth of the first driving switch DRn-1 is large, the voltage Vgs between the gate and the source terminal of the first driving switch DRn-1 is also large. Since the respective increments are differentiated by Equation 2, the influence of the current Ioled flowing through the driving switch DR on the threshold voltage Vth can be compensated.

<Third time period (T3)>

During the third time period T3, the first scan switch SWn-1 and the second sub-pixel 122n are formed by the high logic scan pulse SP applied to the first scan switch SWn-1. The second sensing switch SEWn is turned on, and as a data voltage for displaying an image on the data line Dm, the second data voltage (represented as a voltage of a high logic voltage higher than the first data voltage in the drawing as image data) is The current is transferred to the first node N1 , and the current starts flowing through the first driving switch DRn-1 again. Thus, the voltage of the second node N2 increases. In this case, the threshold voltage Vth of the first driving switch DRn-1 is compensated as in the second time period T2, but mobility compensation may be performed by shortening the third time period T3. At this time, the rising voltage of the second node N2 varies depending on the mobility k of the driving switch DRn-1, but as described in Equation 2, the mobility k and the gate and Since the voltage Vgs between the sources is inversely proportional, the influence of the current Ioled flowing through the driving switch DR on the mobility k may be reduced.

The above-described method of compensating for the threshold voltage and mobility may be equally described for the remaining sub-pixels.

Meanwhile, after the third period T3 , the voltage on the second node N2 charged by the driving current IDS between the drain and the source of the first driving switch DRn-1 becomes the threshold voltage of the organic light emitting diode OLED. As an abnormality, the organic light emitting diode OLED may emit light by the compensated driving current Ioled. In addition, the voltage on the second node N2 is increased by the driving current Ioled, and at the same time, the first scan switch SWn-1 is turned off due to the coupling action of the storage capacitor Cst. The voltage on the node N1 also rises. In addition, since the voltage across the storage capacitor Cst, that is, the charging voltage equal to the potential difference between the first and second nodes N1 and N2 is maintained, a constant driving current Ioled flows through the organic light emitting diode OLED during one frame. Therefore, the brightness of the pixel can be maintained for one frame.

A step-by-step summary of the threshold voltage Vth and mobility k compensation of the driving switch DR is as follows.

As a first step, the first and second nodes N1 and N2 that are gate and source terminals of the driving switches 122 of all sub-pixels may be initialized. As a second step, a first data voltage for threshold voltage compensation is applied to the first node N1 , and the voltage on the floating second node N2 is increased by a current flowing through the driving switch DR. At this time, the difference between the first data voltage on the first node N1 where the voltage on the second node N2 is the gate terminal of the driving switch DR and the voltage on the second node N2 is the threshold of the driving switch DR. It rises until the voltage (Vth) is reached. And when the difference between the first data voltage on the first node N1 that is the gate terminal of the driving switch DR and the voltage of the second node N2 becomes the threshold voltage Vth of the driving switch DR, the driving switch The driving switch DR is turned off while the current flowing through DR is stopped. Therefore, the time required to compensate the threshold voltage Vth of the driving switch DR by performing the second step may be at least a time required until the current flowing through the driving switch DR stops. Meanwhile, since the first data voltage is a data voltage for threshold voltage compensation, the first data voltage may be set to a voltage that does not turn on the organic light emitting diode (OLED). In addition, the second node N2, which is the source terminal of the driving switch DR of the adjacent sub-pixel, is re-initialized.

As a third step, when a second data voltage, which is a data voltage for image display, is applied to the first node N1 , the voltage on the first node N1 rises, and the voltage on the first node N1 rises and is floated by the current flowing through the driving switch DR. The voltage on the second node N2 rises. At this time, the degree of increase of the voltage on the second node N2 varies according to the current capability of the driving switch DR, that is, the mobility K. In addition, when the scan switch SW is turned off in the fourth step, the first node N1 is in a floating state, and when the voltage of the second node N2 is increased, the second node N1 is coupled according to the coupling phenomenon of the storage capacitor Cst The voltage of the first node N1 is also increased by the amount of the node N2 rising, so that the voltage between the gate and the source terminal of the driving switch DR is kept constant, so that the mobility k of the driving switch DR during one frame ) as a compensated constant current flows, the organic light emitting diode (OLED) can emit light while maintaining uniform luminance.

Since the current Ioled of the organic light emitting diode OLED is greatly affected by the threshold voltage Vth and the mobility k of the driving switch DR, the characteristics of the driving switch DR are compensated through the above-described compensation method. Thus, the uniformity of the entire video image can be improved.

In addition, the organic light emitting diode display panel is compensated by an external compensation method that senses the threshold voltage Vth and the mobility k of the driving switch DR and applies the compensated image data to increase the accuracy of compensation. Instead, by using an internal compensation method to compensate in real time while the organic light emitting diode display panel is being driven, it compensates for changes in the characteristics of the organic light emitting diode (OLED) and the transistor serving as a switch according to changes in the external environment and temperature inside the panel. can improve the quality of In addition, the control signal for controlling the sensing switch of the sub-pixel becomes a scan pulse of the gate line of another adjacent sub-pixel on the vertical line, thereby securing a high aperture ratio and reducing the cost due to a reduction in the number of lines.

In addition, by replacing the control line of the sensing switch SEW between the sub-pixels disposed on the vertical line of the display panel 116 with the gate line controlling the scan switch SW disposed in the sub-pixel of the previous stage, one When the driving switch DR of the sub-pixels on the horizontal line is compensated, the accuracy of compensation may be increased by initializing the sub-pixels on the next horizontal line once again.

Also, by performing re-initialization for each sub-pixel immediately before the compensation time, it is possible to increase the accuracy of compensation.

In the detailed description of the present invention described above, it has been described with reference to preferred embodiments of the present invention, but 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.

116 display panel
118 gate drive circuit
120 data drive circuit
122 pixels
122n-1 first sub-pixel
122n second sub-pixel
122n+1 third sub-pixel
124 timing controller

Claims (7)

delete delete delete a first scan switch controlled by a scan pulse on an n (n is a natural number greater than or equal to 2)-1th gate line among the plurality of gate lines and connected between the data line and the first node; a first driving switch controlled by the voltage on the first node and connected between a first power terminal and a second node; a first sensing switch connected between the second node and a sensing line; and a first sub-pixel including a first organic light emitting diode connected between the second node and a second power terminal; and
a second scan switch controlled by a scan pulse on an nth gate line among the plurality of gate lines and connected between a data line and a fourth node; a second driving switch controlled by a voltage on the fourth node and connected between the first power terminal and a fifth node; a second sensing switch connected between the fifth node and the sensing line and controlled by a scan pulse of the n-1 th gate line; and a second sub-pixel formed of a second organic light emitting diode connected between the fifth node and the second power terminal. including,
In the initialization step,
The scan pulses on the n-1 th and n th gate lines are both high logic,
The first and second scan switches are operated by the scan pulses on the n-1 th and n th gate lines so that the first and fourth nodes are initialized by the first initialization voltage on the data line;
The second sensing switch is operated by a scan pulse on the n-1 th gate line, so that the fifth node is initialized by a second initialization voltage on the sensing line;
In the re-initialization step,
a scan pulse on the n-1 th gate line is logic high, and a scan pulse on the n th gate line is logic low;
A method of driving an organic light emitting diode display panel in which the second sensing switch is operated by the second scan pulse on the n-1 th gate line, and the fifth node is reinitialized by the second initialization voltage on the sensing line. 5. The method of claim 4,
The compensation step is a threshold voltage compensation step,
In the threshold voltage compensation step,
The first scan switch is operated by a scan pulse on the n−1th gate line to supply a first data voltage for compensating a threshold voltage on the data line to the first node, and the first and second nodes A method of driving an organic light emitting diode display panel for compensating for the threshold voltage of the first driving switch by increasing the voltage on the floating second node until the difference in phase voltage becomes the threshold voltage of the first driving switch . 5. The method of claim 4,
The compensation step is a mobility compensation step,
In the mobility compensation step,
The first scan switch is operated by a scan pulse on the n−1th gate line to supply a second data voltage for displaying an image on the data line to the first node, and the floating second A method of driving an organic light emitting diode display panel for compensating for mobility of the first driving switch by increasing a voltage of a node. 5. The method of claim 4,
The compensation step is a threshold voltage and mobility compensation step,
The threshold voltage and mobility compensation step,
a first step of operating the first scan switch according to a scan pulse on the n-1 th gate line and floating the second node;
supplying a first data voltage for compensating a threshold voltage on the data line to a first node, and floating until a difference between voltages on the first and second nodes becomes a threshold voltage of the first driving switch a second step of compensating for a threshold voltage of the first driving switch by increasing the voltage on the second node; and
and a third step of compensating for mobility of the first driving switch by supplying a second data voltage for displaying an image on the data line to the first node.

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