KR20160070871A - Organic light emitting diode display panel and drving method thereof - Google Patents

Abstract

The sensing switch of the n-th sub-pixel among the sub-pixels arranged in the vertical direction of the display panel of the organic light emitting diode display panel according to the embodiment of the present invention is a scan switch of the n- Lt; / RTI > can be controlled by the scan pulse on the gate line connected to the scan line. 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 line decrease can be increased.

Description

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

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

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

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

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

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

Since the current of the organic light emitting diode is greatly influenced by the threshold voltage Vth and the mobility k of the driving transistor, the threshold voltage Vth and the mobility k must be accurately measured and compensated Needs increased.

For this purpose, many researches on internal compensation and external compensation have been made. However, the internal compensation method has a problem in securing the aperture ratio by increasing the number of elements constituting the pixels in order to secure compensation performance.

In addition, in the case of the external compensation method, since it is difficult to compensate in real time, there is a problem that the afterimage of the driving transistor is weak.

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

In addition, embodiments of the present invention may provide an organic light emitting diode display panel and a method of driving the same that can improve the accuracy of compensation by detecting the mobility of the driving transistor.

Also, an embodiment of the present invention may provide an organic light emitting diode display panel and a driving method thereof that secure an aperture ratio by using a pixel structure sharing a gate line and a sensing control line between adjacent pixels.

Also, the embodiment of the present invention may provide an organic light emitting diode display panel and a driving method thereof, which can ensure compensation performance by using an external compensation method and an internal compensation method in parallel.

In the embodiment of the present invention, the compensation for the mobility can be performed in real time by applying the threshold voltage to the external compensation method and compensating for the mobility by applying the internal compensation method. And a method of driving the organic light emitting diode display panel.

The organic light emitting diode display panel according to the embodiment of the present invention can increase the aperture ratio according to the line decrease by using the gate line of the adjacent sub pixel on the vertical line as a line for driving the sensing switch.

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

The embodiment of the present invention can precisely control the current flowing through the organic light emitting diode by detecting the threshold voltage of the driving transistor, detect the mobility of the driving transistor to increase the accuracy of compensation, It is possible to provide an organic light emitting diode display panel and a driving method thereof that can secure an aperture ratio by using a pixel structure sharing a control line and can secure a compensation performance in parallel with an external compensation method and an internal compensation method.

1 is a view showing a structure of an organic light emitting diode.
2 is a circuit diagram showing one pixel equivalently in an active matrix type organic light emitting diode display.
3 is a block diagram illustrating an organic light emitting diode display device according to an embodiment of the present invention.
4 is a diagram illustrating a pixel structure according to an embodiment of the present invention.
5 is a waveform diagram of signals of sub-pixels according to a method of compensating mobility.
6 is a waveform diagram of signals of first through third sub-pixels according to a method of compensating mobility.
Fig. 7 is a diagram showing signal waveforms in a method of compensating the threshold voltage and the mobility of the drive 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 following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the size and thickness of an apparatus may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

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

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

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

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

≪ Structure of organic light emitting diode &

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

The organic light emitting diode display device may have an organic light emitting diode as shown in FIG. The organic light emitting diode may include an organic compound layer (HIL, HTL, EML, ETL, EIL) formed between an anode electrode and a cathode electrode. The organic compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer EIL). When a driving voltage is applied to the anode electrode and the cathode electrode, holes passing through the HTL and electrons passing through the ETL are transferred to the EML to form excitons, Thereby generating visible light. The organic light emitting diode display device arranges the pixels including the organic light emitting diode in a matrix form and controls the brightness of the pixels selected by the scan pulse according to the gray level of the digital video data. Such an organic light emitting diode display device is divided into a passive matrix type and an active matrix type using a TFT as a switching element. Among these, the active matrix method selects a pixel by selectively turning on the TFT as the active element and maintains the light emission of the pixel with the voltage held in the storage capacitor.

≪ Equivalent circuit diagram of active matrix type pixel &

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

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

Equation 1

Here, 'Vgs' is the difference voltage between the gate voltage Vg and the source voltage Vs of the drive switch DR, 'Vdata' is the data voltage, 'Vinit' is the initialization voltage, 'Ioled' Vth 'denotes a threshold voltage of the driving switch DR, and' k 'denotes a constant value determined by the mobility and parasitic capacitance of the driving switch DR.

It can be seen that the current Ioled of the organic light emitting diode OLED is greatly affected by the threshold voltage Vth and the mobility k of the driving switch DR as shown in Equation 1. Therefore, the uniformity of the entire image is dependent on the characteristic deviation of the drive switch DR, that is, the deviation between the mobility k and the threshold voltage Vth. On the other hand, the driving switch DR for the organic light emitting diode display device can be fabricated on the basis of amorphous silicon (s-Si) or low temperature polycrystalline silicon (LTPS). Amorphous silicon-driven switches have very uniform characteristics, but have stability problems such as threshold voltage shift. And since the mobility is low, it is difficult to drive circuit directly on the panel. On the other hand, low-temperature polycrystalline silicon-driven switches have relatively high stability and high mobility, but the deviation between threshold voltage and mobility characteristics is large 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 device according to an embodiment of the present invention.

Referring to FIG. 3, the organic light emitting diode display device 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 includes a plurality of pixel regions D1 to Dm, a plurality of sensing lines S1 to Sk, and a plurality of gate lines G1 to Gn, (N) pixels 122 formed in the pixel unit 120. [ The display panel 116 may include j sensing control lines SC1 through SCj and may include a gate driving circuit 118 in the case of the first sensing control line SC1 among the sensing control lines SC1 through SCj, And the pixels on the first horizontal line are connected to each other, but in the remaining sensing control lines SC2 to SCj, the gate lines G1 to Gn and the remaining pixels can be connected to each other.

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

Signal lines for supplying the first driving power Vdd to the respective pixels 122 and signal lines for supplying the second driving power Vss may be formed on the display panel 116. [ Here, the first driving power supply Vdd and the second driving power supply Vss may be generated from the high potential driving voltage source VDD and the low potential driving voltage source VSS, respectively.

The gate drive circuit 118 generates a scan pulse SP in response to the gate control signal GDC from the timing controller 124 and sequentially supplies the scan pulse SP to the gate lines G1 to Gn.

The gate driving circuit 118 is controlled by the timing controller 124 to output a sensing control signal SCS to the first sensing control line SC1 and outputs the sensing control signal SCS to the first horizontal The sensing switches in the pixels on the line can be controlled. The sensing switches of the pixels other than the pixels on the first horizontal line may be controlled by a scan pulse supplied from the gate line of the gate driving circuit 118.

Since the sub-pixel on the first horizontal line located at the uppermost end of the display panel 116 does not have the previous sub-pixel, the gate drive circuit 118, as a control line for driving these sensing switches, Only the line SC1 can be provided, so that it is possible to secure the aperture ratio as the number of lines decreases.

The gate driving circuit 118 outputs both the scan pulse SP and the sensing control signal SCS. However, the present invention is not limited thereto, and the timing control circuit 124 may control the sensing control signal SCS It is also possible to provide a sensing switch control driver which can output a large amount of data.

The data driving circuit 120 can be controlled by the data controller DDC from the timing controller 124 and outputs the sensing voltage to the data lines D1 to Dm and the sensing voltages S1 to Sk .

Each of the data lines D1 to Dm may be connected to each of the pixels 122 to apply a data voltage to each of the pixels 122. [

Each of the sensing lines S1 to Sk may be connected to the pixel 122 to supply a sensing voltage and measure a sensing voltage on the sensing lines S1 to Sk. Specifically, by supplying the initialization voltage using one sensing line (S1 to Sk), it is possible to detect the sensing voltage using charging and floating with the initialization voltage.

The data driving circuit 120 can output or detect the data voltage and the sensing voltage. However, the present invention is not limited to this, and may include a separate driver capable of outputting or detecting the sensing voltage.

<Pixel Structure>

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

The pixel 122 described in the present invention may refer to any one of red, green, blue, and white, which may be referred to as a sub-pixel separately.

If the sub-pixels connected to the first gate line G1 are referred to as sub-pixels on the first horizontal line, the sub-pixels connected to the n-th gate line Gn may be referred to as sub-pixels on the n-th horizontal line . If the subpixels connected to the first data line D1 are referred to as subpixels on the first vertical line, the subpixels connected to the mth data line Dm may be referred to as subpixels on the mth vertical line .

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

The first sub-pixel 122n-1 includes a first scan switch SWn-1, a first drive switch DRn-1, a first sensing switch SEWn-1, an organic light emitting diode OLED, (Cst).

The first scan switch SWn-1 is controlled by a 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. And may be connected between the data line Dm and the first node N1.

The first driving switch DRn-1 is a transistor that adjusts 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 gate-source thereof, 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 first sensing switch SEWn-1 is a transistor for controlling the threshold voltage of the first driving switch DRn-1 through the initializing and sensing line Sk of the second node N2. May be 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 thereof may be connected to the second driving power source Vss.

The storage capacitor Cst may be connected between the first and second nodes N1 and N2, that is, between the gate and source terminals of the first drive switch DRn-1.

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

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

The second driving switch DRn is a transistor for adjusting a current flowing in the organic light emitting diode OLED by a voltage between a first node N1 and a second node N2 which are gate-source of the second driving switch DRn, 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 second sensing switch SEWn is a transistor for controlling the threshold voltage of the second driving switch DRn through the initializing and sensing line Sk to the second node N2. May be 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 drive switch DRn + 1, a third sensing switch SEWn + 1, an organic light emitting diode OLED, (Cst).

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 And may be connected between the data line Dm and the first node N1.

The third driving switch DRn + 1 is a transistor for adjusting a current flowing in the organic light emitting diode OLED by a voltage between a first node N1 and a second node N2, which are gate-source thereof, 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 third sensing switch SEWn + 1 is a transistor for controlling the threshold voltage of the third driving switch DRn + 1 through the initializing and sensing line Sk of the second node N2. 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 can be connected to the gate line Gn-1 of the previous sub-pixel 122n-1. The scan switches SWn-1 and nn of the previous sub-pixel 122n-1 and the sense switches SWn-1 and 122n-1 of the previous sub-pixel 122n-1 are turned on by the scan pulse on the gate line Gn- 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 due to the line decrease can be increased.

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 + The first to third nodes N1 to N3 of the first to ninth nodes N7 to N9 may be referred to as seventh to ninth nodes N7 to N9.

<External Compensation Method of Threshold Voltage>

The data signal for compensating the threshold voltage is applied to the gate terminal of the driving switch DR in the sub pixel 122. [ The voltage on the second node N2 in the floating state is raised by the current flowing in the drive switch DR and the current flowing in the drive switch DR is supplied to the gate terminal of the drive switch DR, The flow is stopped when the voltage between the gate and the source of the driving transistor becomes the threshold voltage Vth of the driving switch DR. At this time, the voltage on the second node N2 is detected through the sensing line Sk and compared with the input data signal, the voltage Vg (= Vdata) -Vs (N2 node voltage) The voltage Vth can be detected. In this way, the threshold voltage can be compensated using the external compensation method, and the threshold voltage using the external compensation method can be performed in the initial driving step of the organic light emitting diode display device.

<Mobility compensation method>

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

The mobility described below can be compensated by the internal compensation scheme. Such an internal compensation scheme can be performed in real time in the driving stage of the organic light emitting diode display device.

Referring to FIG. 5, since the scan pulse SP of high logic is supplied to all the scan switches SW in the initialization period Tin, all the sub-pixels 122, The first and second nodes N1 and N2, which are the gate and source terminals of the drive switch DR, are initialized, respectively. The second node N2 which is the source terminal of the second drive switch DRn in the nth sub-pixel 122n is connected to the first scan switch SWn-1 of the (n-1) th sub-pixel 122n-1 The first node N1 which is the gate terminal of the second driving switch DRn of the nth sub-pixel 122n is initialized again when the scan pulse SP of the high logic is supplied, The data voltage for image display on the data line Dm is written and written while being turned on so that the voltage of the second node N2 rises according to the current capability of the second driving switch DRn, And the mobility (k) is compensated.

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

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

&Lt; First Time Zone (T1) >

The scan pulse SP of high logic is supplied to all the gate lines Gn-1, Gn and Gn + 1 during the first time period T1 so that all of the scan switches SWn-1, SWn, SWn + 1 and all The sensing switches SEWn-1, SEWn and SEWn + 1 are turned on to initialize the first and second nodes N1 and N2 which are the gate and source nodes of all the drive switches DRn-1, DRn and DRn + 1 .

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.

&Lt; Second time zone (T2) >

1 and the second sub-pixel 122n by a scan pulse SP of high logic applied on the first scan switch SWn-1 during the second time period T2. 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, 122n may be reinitialized by the initializing voltage on the sensing line Sk as the second sensing switch SEWn is turned on.

In addition, when a data signal (represented by a high logic signal in the drawing) for image display which is varied from the voltage for re-initialization is input to the data line Dm, the first node N1 The voltage of the second node N2 of the first sub-pixel 122n-1 in the floating state is also increased by the first drive switch DRn-1 of the first sub-pixel 122n-1 ). The amount of increase of the voltage on the second node N2 of the first sub-pixel 122n-1 is determined by the characteristics of the first driving switch DRn-1, the mobility of the first driving switch DRn- &Lt; / RTI &gt;

&Lt; Third time zone (T3) >

The first sub-pixel 122n-1 after the second time period T2 can enter the light emission period and the scan pulse of the high logic applied on the second scan switch SWn during the third time period T3 The third sensing switch SEWn + 1 on the second scan switch SWn and the third sub-pixel 122n + 1 may be turned on by the second scan switch SP. 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 node N1 of the third sub pixel 122n + The second node N2 on the sensing line Sk can be reinitialized by the initializing voltage on the sensing line Sk as the third sensing switch SEWn + 1 is turned on.

Further, when a data signal (represented by a high logic signal in the drawing) fluctuates from the voltage for re-initialization on the data line Dm, the voltage of the first node N1 of the second sub-pixel 122n rises , The voltage of the second node N2 of the second sub-pixel 122n in the floating state also rises by the current flowing in the second driving switch DRn of the second sub-pixel 122n. At this time, the amount of increase of the voltage on the second node N2 of the second sub-pixel 122n may be changed according to the degree of movement of the second drive switch DRn.

&Lt; Fourth time zone (T4) >

The third sub pixel 122n + 1 during the fourth time period T4 may operate in the same manner as the second sub pixel 122n during the third time period T3 described above.

The mobility of the drive switch DR of all the sub-pixels 122 can be compensated according to the mobility compensation method described above. Referring to Equation 2, in the case of the drive switch DR having a large mobility k, the voltage on the second node N2 rises quickly, so that the voltage Vgs between the gate and the source of the drive switch DR is small Loses.

Equation 2

That is, in Equation (2), the mobility k and the voltage Vgs between the gate and the source of the drive switch DR are in inverse proportion to the mobility k of the current Ioled flowing in the drive switch DR Can be reduced.

<Threshold Voltage and Mobility Compensation Method>

Fig. 7 is a diagram showing signal waveforms in a method of compensating the threshold voltage and the mobility of the drive switch.

Referring to FIG. 7, the threshold voltage and the mobility of the driving switch DR of all the sub-pixels 122 can be compensated by the internal compensation scheme.

&Lt; First Time Zone (T1) >

The scan pulse SP of high logic is supplied to all the gate lines Gn-1, Gn and Gn + 1 during the first time period T1 so that all of the scan switches SWn-1, SWn, SWn + 1 and all The sensing switches SEWn-1, SEWn and SEWn + 1 are turned on to initialize the first and second nodes N1 and N2 which are the gate and source nodes of all the drive switches DRn-1, DRn and DRn + 1 .

In this manner, the gate and source terminals N1 and N2 of the driving transistor DR of all the sub-pixels 122 for increasing the accuracy of compensation can be initialized at one time.

&Lt; Second time zone (T2) >

1 and the second sub-pixel 122n by a scan pulse SP of high logic applied on the first scan switch SWn-1 during the second time period T2. The second sensing switch SEWn may be turned on. The first data voltage for compensating the 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 can be reinitialized by the initializing voltage on the sensing line Sk as the second sensing switch SEWn is turned on.

In addition, when a first data signal (represented by a high logic signal in the figure) fluctuates on the data line Dm, the voltage of the first node N1 of the first sub-pixel 122n-1 rises, the voltage of the second node N2 of the first sub-pixel 122n-1 in the floating state also rises by the current flowing in the first driving switch DRn-1 of the first sub-pixel 122n-1 . At this time, the voltage on the second node N2 of the first sub-pixel 122n-1 may be increased by Vg-Vth by the threshold voltage Vth of the first driving switch DRn-1. This process continues until almost no current flows through the first drive switch DRn-1, and the operation ends when the first drive switch DRn-1 is turned off. The threshold voltage Vth of the first drive 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 be varied according to the threshold voltage Vth of the first driving switch DRn-1. For example, when the threshold voltage Vth of the first drive switch DRn-1 is large, the increase amount of the voltage on the second node N2 is small. Since the amount of rise of the voltage on the second node N2 is small, the voltage Vgs between the gate and the source terminal of the first drive switch DRn-1 becomes large. Therefore, when the threshold voltage Vth of the first drive switch DRn-1 is large according to Equation (2), the voltage Vgs between the gate and the source terminal of the first drive switch DRn-1 becomes large, The increase amount of each of these is differentiated by Equation 2, so that the influence of the current Ioled flowing through the drive switch DR on the threshold voltage Vth can be compensated.

&Lt; Third time zone (T3) >

1 and the second sub-pixel 122n by the scan pulse SP of high logic applied on the first scan switch SWn-1 during the third time period T3, The second sensing switch SEWn is turned on and the second data voltage (represented by the voltage of the voltage High logic higher than the first data voltage in the drawing as the image data) as the data voltage for image display on the data line Dm Is transmitted on the first node N1, and the current starts to flow again in the first drive switch DRn-1. Thus, the voltage of the second node N2 rises. In this case, the threshold voltage Vth of the first drive switch DRn-1 is compensated as in the second time period T2, but mobility compensation can be performed by shortening the third time period T3. The rising voltage of the second node N2 varies depending on the mobility k of the driving switch DRn-1. However, as described in Equation 2, The voltage Vgs between the sources becomes inversely proportional so that the influence on the mobility k of the current Ioled flowing in the drive switch DR can be reduced.

The above-described method of compensating the threshold voltage and the mobility can be equally explained in the remaining sub-pixels.

On the other hand, after the third period T3, the voltage on the second node N2 charged by the drain-source driving current IDS of the first driving switch DRn-1 is lower than the threshold voltage Vd of the organic light emitting diode OLED The organic light emitting diode OLED can emit light by the compensated driving current Ioled. When the voltage on the second node N2 rises due to the driving current Ioled and the first scan switch SWn-1 is turned off, the first scan switch SWn- The voltage on the node N1 also rises. And the charge voltage corresponding to the voltage across the storage capacitor Cst, that is, the potential difference on the first and second nodes N1 and N2, so that a constant drive current Ioled flows through the organic light emitting diode OLED for one frame The brightness of the pixel can be maintained for one frame.

The threshold voltage (Vth) and mobility (k) compensation of the above-described drive switch DR can be summarized as follows.

The first and second nodes N1 and N2 which are the gate and source terminals of the drive switch 122 of all the sub-pixels can be initialized as a first step. In the second step, a first data voltage for threshold voltage compensation is applied on the first node N1, and the voltage on the second node N2 in the floating state rises due to the current flowing in the drive switch DR. 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 drive switch DR and the voltage of the second node N2 is smaller than the threshold voltage of the drive switch DR And rises until the voltage becomes Vth. When the difference between the first data voltage on the first node N1 which is the gate terminal of the drive switch DR and the voltage of the second node N2 becomes the threshold voltage Vth of the drive switch DR, The current flowing in the driving transistor DR is stopped and the driving switch DR is turned off. Therefore, the time required to compensate the threshold voltage Vth of the drive switch DR by performing the second step may be at least the time required to stop the current flowing in the drive switch DR. Meanwhile, since the first data voltage is a data voltage for threshold voltage compensation, the first data voltage may be set to a voltage at which the organic light emitting diode OLED is not turned on. At the same time, the second node N2, which is the source terminal of the drive switch DR of the adjacent sub-pixel, is reinitialized.

In the third step, when the second data voltage, which is a data voltage for displaying an image, is applied on the first node N1, the voltage on the first node N1 rises, The voltage on the second node N2 rises. At this time, the degree of increase of the voltage on the second node N2 varies depending on the current capability of the drive switch DR, that is, the mobility K. When the scan switch SW is turned off in the fourth step, the first node N1 is in a floating state. When the voltage of the second node N2 rises, The voltage of the first node N1 also rises by the amount of rise of the node N2 so that the voltage between the gate and source terminals of the drive switch DR is kept constant and the mobility k of the drive switch DR during one frame The organic light emitting diode OLED can emit light while maintaining a 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 So that the uniformity of the entire image can be improved.

In addition, it is possible to compensate the organic light emitting diode display panel by an external compensation method for sensing the threshold voltage (Vth) and the mobility (k) of the drive switch DR and applying the compensated image data, In addition, by compensating in real time during driving of the organic light emitting diode display panel by using the internal compensation method, it is possible to compensate for changes in characteristics of the organic light emitting diode (OLED) Can be improved. Further, the control signal for controlling the sensing switch of the sub-pixel is a scan pulse of the gate line of another adjacent sub-pixel on the vertical line, thereby ensuring a high aperture ratio and reducing the cost due to the reduction in the number of lines.

Further, by replacing the control line of the sensing switch SEW between the sub-pixels arranged 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, When compensating the drive switch DR of the sub-pixels on the horizontal line, the sub-pixels on the next horizontal line can be initialized again to improve the accuracy of compensation.

In addition, the re-initialization is performed immediately before the compensation time for each sub-pixel, thereby improving the accuracy of compensation.

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

116 Display panel
118 gate drive circuit
120 data driving circuit
122 pixels
122n-1 &lt; / RTI &gt; first sub-pixel
122n second sub pixel
122n + 1 &lt; / RTI &gt; third sub-pixel
124 Timing controller

Claims (7)

A first scan switch controlled by a scan pulse on a n-th gate line of the plurality of gate lines (n is a natural number of 2 or more) -1 and connected between the data line and the first node; A first drive switch controlled by a voltage on the first node and connected between a first power supply terminal and a second node; A first sensing switch connected between the second node and a sensing line; A first sub-pixel comprising a first organic light emitting diode connected between the second node and a second power supply terminal; And
A second scan switch controlled by a scan pulse on an n-th gate line of the plurality of gate lines and connected between a data line and a fourth node; A second drive switch controlled by a voltage on the fourth node and connected between the first power supply terminal and a fifth node; A second sensing switch connected between the fifth node and the sensing line; And a second sub-pixel including a second organic light emitting diode connected between the fifth node and the second power supply terminal,
And the second sensing switch is controlled by a scan pulse of the (n-1) th gate line. The method according to claim 1,
The organic light emitting diode display panel may further include a sensing control line,
When n is 2
Wherein the first sensing switch comprises:
Wherein the organic light emitting diode display panel is controlled by a sensing control signal on the sensing control line. The method according to claim 1,
And the first and second sub-pixels are sequentially arranged in the vertical direction of the display panel. A method of driving an organic light emitting diode display panel according to claim 1,
In the initialization step,
The first and second scan switches are operated by a first scan pulse on the (n-1) th and (n) -th gate lines so that the first and fourth nodes are initialized by a first initializing voltage on the data line,
And the second sensing switch is operated by a scan pulse on the (n-1) th gate line to initialize the fifth node by a second initializing voltage on the sensing line. 5. The method of claim 4,
The driving method of the organic light emitting diode display panel further includes a threshold voltage compensation step and a re-initialization step,
In the threshold voltage compensation step,
The first scan switch is operated by a second scan pulse on the (n-1) th gate line to supply a first data voltage for threshold voltage compensation on the data line on the first node, Compensating the threshold voltage of the first drive switch by increasing the voltage on the second node floating until the difference in voltage on the two nodes becomes the threshold voltage of the first drive switch,
In the re-initialization step,
Wherein the second sensing switch is operated by the second scan pulse and the fifth node is reinitialized by the second initialization voltage on the sensing line. 5. The method of claim 4,
The driving method of the organic light emitting diode display panel may further include a mobility compensation step and a re-initialization step,
In the mobility compensation step,
The first scan switch operates by a second scan pulse on the (n-1) th gate line to supply a second data voltage for image display on the data line to the first node, The voltage of the second node is raised to compensate the mobility of the first drive switch,
In the re-initialization step,
Wherein the second sensing switch is operated by the second scan pulse and the fifth node is reinitialized by the second initialization voltage on the sensing line. 5. The method of claim 4,
The driving method of the organic light emitting diode display panel may further include a threshold voltage and mobility compensation step and a re-initialization step,
Wherein the step of compensating the threshold voltage and mobility comprises:
A first step of operating the first scan switch and floating the second node according to a second scan pulse on the (n-1) th gate line;
Supplying a first data voltage for a threshold voltage compensation on the data line on a first node and floating the first data voltage until a difference in voltage on the first and second nodes becomes a threshold voltage of the first drive switch, A second step of increasing a voltage on the second node to compensate a threshold voltage of the first driving switch; And
And a third step of supplying a second data voltage for video display on the data line to the first node to compensate for the mobility of the second drive switch,
In the re-initialization step,
Wherein the second sensing switch is operated by the second scan pulse and the fifth node is reinitialized by the second initialization voltage on the sensing line.

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