KR20170021406A - Degradation Sensing Method For Emitting Device Of Organic Light Emitting Display - Google Patents

Abstract

The present invention provides a degradation sensing method for a light emitting device of an organic light emitting display (OLED) device. According to the present invention, the method comprises the following steps of: turning off a driving thin film transistor (TFT) for a first period and allowing a sensing unit to apply a reference voltage of a first level which is higher than an OLED operating point voltage to an anode end of an OLED connected to a source electrode of the driving TFT to turn on the OLED; floating the anode end of the OLED for a second period to lower a potential of the anode end of the OLED to the OLED operating point voltage and allowing the sensing unit to charge a sensing line with a reference voltage of a second level which is higher than the reference voltage of the first level; and electrically connecting the sensing line and the anode end of the OLED for a third period to allow the sensing unit to sense the voltage remaining in the sensing line at a predetermined time while discharging the reference voltage of the second level, which is charged in the sensing line, through the OLED.

Description

[0001] The present invention relates to a method for sensing degradation of a light emitting device of an organic light emitting display,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting diode (OLED) display, and more particularly, to a method of sensing degradation of a light emitting diode of an OLED display.

An active matrix type organic light emitting display device includes an organic light emitting diode (OLED), has a high response speed, and has a high luminous efficiency, luminance, and viewing angle.

The OLED, which is a light emitting device, includes an anode electrode, a cathode electrode, and organic compound layers (HIL, HTL, EML, ETL, EIL) formed therebetween. 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 display device arranges subpixels each including an OLED in a matrix form and adjusts the luminance of the subpixels according to the gradation of the video data. Each of the subpixels includes a driving TFT (Thin Film Transistor) for controlling a driving current flowing in the OLED according to a voltage (Vgs) applied between the gate electrode and the source electrode of the subpixel, and is represented by an amount of light emitted by the OLED Adjusts the gradation (luminance).

The OLED deteriorates over time of light emission. When the OLED deteriorates, the operating point voltage (threshold voltage) of the OLED increases and the luminous efficiency decreases. The current accumulation value applied to the OLED of each subpixel is proportional to the gradation accumulation value implemented in the corresponding subpixel, so that the degree of OLED degradation may vary from subpixel to subpixel. The OLED deterioration deviation between the sub-pixels causes a luminance deviation, and if it is deepened, an image sticking phenomenon may occur.

In order to compensate for the deterioration of the OLED, the conventional organic light emitting display employs a technique of sensing OLED deterioration and modulating video data in an external circuit based on the sensed value. However, the conventional OLED display has the following problems.

In the conventional OLED display device, the anode voltage of the OLED according to the driving current applied from the driving TFT (i.e., the source voltage of the driving TFT) is sensed to determine the degree of deterioration of the pixel with respect to the OLED. However, when the driving TFT is deteriorated, the electric characteristics (mobility, threshold voltage, etc.) of the driving TFT are changed and the driving current is distorted. This distortion of the driving current degrades the accuracy of the deterioration sensing value for the OLED. In the conventional organic light emitting display, deterioration sensing is performed on the OLED based on the driving current generated in the driving TFT, so it is difficult to accurately detect the OLED deterioration due to the influence on the driving TFT.

Accordingly, it is an object of the present invention to provide a deterioration sensing method of an organic light emitting display device which can improve the accuracy of sensing by excluding influences of driving TFTs in sensing deterioration of an OLED.

In order to achieve the above object, according to the present invention, there is provided a pixel to be sensed including an OLED, a driving TFT connected between the anode ends of the OLED, and a switch TFT connected to the driving TFT, The method comprising the steps of: turning off the driving TFT for a first period of time and outputting a first level reference voltage higher than the OLED operating point voltage in the sensing unit; Applying an electric field to the anode terminal of the OLED connected to the source electrode of the driving TFT to turn the OLED on; floating the anode terminal of the OLED during the second period to lower the anode terminal potential of the OLED to the OLED operating point voltage , Charging the sensing line with the reference voltage of the second level higher than the reference voltage of the first level in the sensing unit, And the OLED is connected to the anode of the OLED through the sensing line and the second level of the reference voltage charged in the sensing line is discharged through the OLED while the sensing line remains in the sensing line at a predetermined time And sensing the voltage.

In the first period, a first sensing data voltage lower than the reference voltage of the first level is applied to the gate electrode of the driving TFT to turn off the driving TFT.

The switch TFT includes a first switch TFT connected between a data line and a gate electrode of the drive TFT and turned on / off in response to a gate signal, and a second switch TFT connected between the source electrode of the drive TFT and the sensing line, Wherein the gate signal includes a first gate high voltage, a gate low voltage lower than the first gate high voltage, and a second gate high voltage that is higher than the first gate high voltage and lower than the first gate high voltage And a low second gate high voltage.

The gate signal is applied to the first gate high voltage in the first period, to the gate low voltage in the second period, and to the second gate high voltage in the third period.

The second gate high voltage is higher than the OLED operating point voltage and lower than the second level reference voltage.

When the non-sensing target subpixel included in one unit pixel and the sensing target subpixel share the same sensing line, in the first period, the second sensing data voltage higher than the first- Pixels to be sensed by applying a voltage to a gate electrode of a first driving TFT included in a sensing target subpixel to turn on the first driving TFT and to apply an OLED operation to an anode terminal of the first OLED included in the non- And applying the reference voltage of the first level higher than the point voltage to turn on the first OLED. And further comprising the step of floating the anode stage of the first OLED to boost the anode stage potential of the first OLED to a level higher than the reference level of the first level in the second period. And electrically disconnecting the sensing line and the anode terminal of the first OLED during the third period.

In the present invention, a reference voltage is applied to the anode terminal of the OLED while the driving TFT is turned off to emit light to the OLED. In this state, the anode terminal of the OLED is floated to set the operating point voltage of the OLED to the anode terminal of the OLED. Then, a discharge path is formed between the sensing line and the OLED to sense the voltage change of the sensing line according to the change of the operating point of the OLED. Thus, the present invention can improve the accuracy of sensing by excluding the influence of the driving TFT in sensing the deterioration of the OLED.

Furthermore, according to the present invention, a sensing line shared structure (a structure in which a subpixel to be sensed and a subpixel to be non-sensing share the same sensing line) and a scan structure (the first and second switch TFTs in one subpixel are the same gate signal ) Can be employed to increase the aperture ratio of the display panel.

In addition, even if the sensing line sharing structure is employed, the sensing data voltage applied to the subpixel to be sensed and the sensing data voltage applied to the non-sensing subpixel are different from each other, The OLED degradation of the subpixels to be sensed can be selectively sensed.

FIG. 1 is a view illustrating an organic light emitting display according to an embodiment of the present invention. FIG.
FIGS. 2A and 2B are views showing examples of connection of a sensing line and a sub-pixel. FIG.
Figs. 3 and 4 are views showing an example of a configuration of a pixel array and a data driver IC; Fig.
5 is a view showing an example of a configuration of a subpixel and a sensing unit to which the degradation sensing method of the present invention is applied.
FIG. 6 is a diagram showing a method of detecting a deterioration of a subpixel to be sensed according to the present invention; FIG.
FIG. 7 is a graph showing control signal waveforms and potential change waveforms for each section before and after deterioration when FIG. 6 is applied to FIG. 5;
8A to 8C are diagrams showing the operation of the subpixel and the sensing unit in the first period, the second period, and the third period of FIG. 7, respectively.
FIG. 9 is a diagram illustrating a method of excluding the perturbation sensing of the present invention for non-sensing target subpixels; FIG.
FIG. 10 is a graph showing control signal waveforms and potential change waveforms for each section before and after deterioration when FIG. 9 is applied to FIG. 5;
11A to 11C are diagrams showing the operation of a subpixel and a sensing unit in each of the first period, the second period, and the third period in FIG. 10;
12 is a view showing a sensing value according to deterioration of an OLED when the present invention is applied.
13 is a diagram showing a difference in sensing value according to a sensing time.

First, a configuration of an OLED display to which the degradation sensing method of the present invention is applied will be described with reference to FIGS. 1 to 5. FIG.

FIG. 1 shows an organic light emitting display according to an embodiment of the present invention. 2A and 2B show an example of connection of a sensing line and a subpixel. 3 and 4 show an example of the configuration of the pixel array and the data driver IC.

1 to 4, an OLED display according to an exemplary embodiment of the present invention includes a display panel 10, a timing controller 11, a data driving circuit 12, a gate driving circuit 13, 16).

A plurality of data lines and sensing lines 14A and 14B and a plurality of gate lines 15 are intersected with each other in the display panel 10 and subpixels P are arranged in a matrix form for each of the intersection areas Thereby constituting a pixel array.

The subpixels P may include horizontally adjacent R subpixels for red display, W subpixel for white display, G subpixel for green display, and B subpixel for blue display, which are horizontally adjacent to each other as shown in FIGS. 2A and 2B have. Each subpixel P may be connected to any one of the data lines 14A, to one of the sensing lines 14B, and to one of the gate lines 15. Each subpixel P may be electrically connected to the data line 14A and the sensing line 14B in accordance with the gate signal SCAN supplied from the gate line 15. [

The sensing line 14B may have a sensing line independent structure as shown in FIGS. 2A and 3 or a sensing line sharing structure as shown in FIGS. 2B and 4, depending on the connection structure.

According to the sensing line independent structure, a plurality of sub-pixels arranged on the same horizontal line can be connected one-to-one to different sensing lines. For example, R pixels, W pixels, G pixels, and B pixels that are horizontally adjacent to each other may be connected to different sensing lines on a one-to-one basis.

In this structure, the OLED can be individually operated, and the degree of deterioration of the OLED can be directly sensed. However, since the number of sensing lines is large, the current density of the OLED is increased to compensate for the decrease in the aperture ratio. Therefore, in the case of this structure, the degradation rate of the OLED increases and the lifetime thereof may be reduced.

According to the sensing line sharing structure, the layout unit pixels on the same horizontal line are connected to the different sensing lines on a one-to-one basis, and the sub pixels constituting the same unit pixel can share the same sensing line. For example, an R pixel, a W pixel, a G pixel, and a B pixel that are adjacent to each other horizontally and form a unit pixel may share the same sensing line. The sensing line sharing structure in which the sensing lines 14B are assigned to each unit pixel is easier to secure the aperture ratio of the display panel than the sensing line independent structure.

Each of the subpixels P is supplied with a high potential drive voltage EVDD and a low potential drive voltage EVSS from a power supply not shown. The subpixel P of the present invention may include an OLED, a driving TFT, first and second switch TFTs, and a storage capacitor so as to comply with an external compensation scheme. The external compensation method is a technique of sensing the electrical characteristics of an organic light emitting diode (OLED) provided in the pixels and correcting input video data according to the sensed value. The TFTs constituting the subpixel P may be implemented as a p-type, an n-type, or a hybrid type in which a p-type and an n-type are mixed. In addition, the semiconductor layer of the TFTs constituting the subpixel P may include amorphous silicon, polysilicon, or an oxide.

Each of the subpixels P may operate differently at the time of the normal driving for the display image implementation and at the sensing operation for obtaining the deterioration sensing value. The sensing operation may be performed in the vertical blank period during the image display operation, or in the power-on sequence period before the image display is started, or in the power-off sequence period after the image display is finished. The vertical blanking period is a period during which no image data is written, and is arranged between vertically active intervals in which image data for one frame is written. The power-on sequence period means a period from when the driving power is turned on until an image is displayed. The power-off sequence period means a period from the end of image display until the drive power is turned off.

Sensing driving means driving for sensing deterioration of the OLED. As will be described later, since the OLED deterioration sensing value of the present invention is not affected by the electrical characteristic deviation of the driving TFT, the sensing driving of the present invention can proceed regardless of the compensation for the electrical characteristic deviation of the driving TFT. In the prior art, the OLED degradation sensing is performed after the electric characteristic deviation of the driving TFT is compensated. However, since the present invention does not have such a limitation, the sensing timing setting is more free.

Sensing operation may be performed by one operation of the data driving circuit 12 and the gate driving circuit 13 under the control of the timing controller 11. [ The operation of deriving the compensation data for the deterioration compensation based on the sensing result and the operation of modulating the digital video data using the compensation data are performed in the timing controller 11. [

The data driving circuit 12 includes at least one data driver IC (Integrated Circuit) (SDIC). The data driver IC (SDIC) includes a plurality of digital-to-analog converters (hereinafter referred to as DACs) 121 connected to each data line 14A, a plurality of sensing units 122 connected to the sensing lines 14B, A mux portion 123 for selectively connecting the sensing units 122 to an analog-to-digital converter (ADC), and a selection control signal is generated to sequentially turn on the switches SS1 to SSk of the mux portion 123 And a shift register 124 which is turned on.

The DAC of the data driver IC (SDIC) converts the digital video data (RGB) into the image display data voltage in accordance with the data timing control signal (DDC) applied from the timing controller 11 during normal driving, . On the other hand, the DAC of the data driver IC (SDIC) can generate the sensing data voltage in accordance with the data timing control signal (DDC) applied from the timing controller 11 during the sensing operation and supply it to the data lines 14A. The sensing data voltage is applied to the gate node of the driving TFT at the time of driving the sensing TFT. The sensing data voltage includes a first sensing data voltage commonly applied to the sub pixels to be sensed and a second sensing data There is a voltage. The data voltage for the first sensing is set to be lower than the reference voltage so that the driving TFT can be turned off so that the influence of the driving TFT is not reflected in the OLED deterioration sensing value. The data voltage for the second sensing is set to be higher than the reference voltage so that the driving TFT can be turned on so that the OLED deterioration sensing value for the non-sensing target subpixel can not be transmitted to the sensing line 14B. This will be described in detail below with reference to concrete examples.

Each sensing unit 122 of the data driver IC (SDIC) is connected to the sensing line 14B. The number of the sensing lines 14B and the sensing units SU in the sensing line shared structure shown in FIG. 4 is reduced compared to the sensing line independent structure shown in FIG. Although the present invention may take a sensing line independent structure, it is more preferable to take a sensing line shared structure in order to reduce the circuit design area and increase the aperture ratio. Further, the present invention can control the first and second switch TFTs in a subpixel simultaneously using one gate signal (SCAN), thereby reducing the number of gate lines and further increasing the aperture ratio.

As will be described later, in the deterioration sensing method of the present invention, a constant voltage (i.e., a reference voltage) is applied from the sensing unit 122 to the source node of the driving TFT (i.e., the anode terminal of the OLED) In this state, the anode terminal of the OLED is floated to set the voltage (threshold voltage) corresponding to the operating point of the OLED to the anode terminal of the OLED. Then, the operating point voltage of the OLED is sensed through the sensing line 14B. Thus, the present invention can improve the accuracy of sensing by excluding the influence of the driving TFT in sensing the deterioration of the OLED.

The deterioration sensing method of the present invention can control the OLED deterioration of a desired subpixel precisely even if a sensing line shared structure is employed. (For example, a black gradation data voltage capable of turning off the driving TFT) applied to the subpixels to be sensed and a sensing data voltage (for example, a driving TFT The OLED anode potential of the subpixel to be sensed is lowered to the OLED operating point voltage and the OLED anode potential of the non-sensing subpixel is boosted to a level much higher than the OLED operating point voltage Voltage. In this state, the present invention is characterized in that the gate signal applied to the sensing line (14B) connecting switch TFT (hereinafter, the second switch TFT in the embodiment) of the subpixel to be sensed that shares the sensing line (14B) To electrically connect only the subpixel to be sensed to the sensing line 14B and to block the electrical connection between the unselected subpixel and the sensing line 14B. By doing so, the present invention can selectively sense only the OLED deterioration of the subpixels to be sensed. To this end, the voltage level of the gate signal must be higher than the OLED operating point voltage of the subpixel to be sensed so that only the switching TFT of the sensing line 14B included in the subpixel to be sensed can be turned on, Must be lower than the OLED boosting voltage of the subpixel.

Each sensing unit 122 of the data driver IC SDIC charges the reference voltage to the line capacitor LCa of the sensing line 14B and when the discharge path is formed between the sensing line 14B and the OLED, And senses the voltage change of the sensing line 14B according to the change. A first period for initializing the voltage between the gate and the source of the driving TFT, a second period for detecting the operating point voltage of the OLED by emitting the OLED, a third period for sensing the operating point voltage of the OLED, The reference voltage can be supplied to the sensing line 14B at the first level in the first period and at the second level higher than the first level in the second and third periods, respectively. When the reference voltage is increased in the second and third periods, the discharging operation can be performed smoothly, thereby improving the sensing resolution and sensing sensitivity and improving the sensing accuracy.

The ADC of the data driver IC (SDIC) converts the sensing voltage input through the mux 123 into a digital sensing value SD and transmits the digital sensing value SD to the timing controller 11.

The gate driving circuit 13 may generate the gate signal SCAN based on the gate timing control signal GDC during the sensing operation and then supply the gate signal SCAN to the gate lines 15 in a row sequential manner. The gate signal SCAN has a first gate high voltage of a first level, a gate low voltage of a second level lower than the first level, and a gate low voltage of a second level lower than the first level so that only the subpixel to be sensed is selectively sensed under the sensing line shared structure And a second gate high voltage of a third level higher than the second level. The gate drive circuit 13 outputs the gate signal SCAN of the first gate high voltage in the first period, the gate signal SCAN of the gate low voltage in the second period, The gate signal SCAN of high voltage can be outputted.

The timing controller 11 controls the operation of the data driving circuit 12 based on timing signals such as a vertical synchronizing signal Vsync, a horizontal synchronizing signal Hsync, a dot clock signal DCLK and a data enable signal DE A data timing control signal DDC for controlling the timing and a gate timing control signal GDC for controlling the operation timing of the gate driving circuit 13 are generated. The timing controller 11 separates the normal drive and the sensing drive based on a predetermined reference signal (drive power enable signal, vertical sync signal, data enable signal, etc.), and generates a data timing control signal DDC It is possible to generate the gate timing control signal GDC. In addition, the timing controller 11 may further generate associated switching control signals (CON, FIG. 5, SAM, PRE) to operate the internal switches of each sensing units 122 for normal driving and sensing driving .

The timing controller 11 can transmit the digital data corresponding to the sensing data voltage to the data driving circuit 12 during sensing driving.

The timing controller 11 updates the digital sensing value SD transmitted from the data driving circuit 12 in the sensing operation to the memory 16 and compares the updated digital sensing value SD with a predetermined initial sensing value . Here, the initial sensing value is set at the product shipping stage and corresponds to the operating point voltage before the OLED is deteriorated. The timing controller 11 reads out the deterioration compensation value from a preset compensation value table (look-up table) using the difference between the updated digital sensing value SD and the initial sensing value as a read address. Then, the timing controller 11 modulates the digital video data RGB for image display based on the readout deterioration compensation value, and transmits the modulated data to the data driving circuit 12 at the time of normal operation.

FIG. 5 shows an example of a configuration of the sub-pixel P and the sensing unit 122 to which the degradation sensing method of the present invention is applied. It should be noted that the technical idea of the present invention is not limited to the exemplary structure of the sub-pixel P and the sensing unit 122, since Fig. 5 is merely an example.

5, each subpixel P includes an OLED, a driving TFT (Thin Film Transistor) DT, a storage capacitor Cst, a first switch TFT ST1, and a second switch TFT ST2 can do.

The OLED includes an anode electrode connected to the source node Ns, a cathode electrode connected to the input terminal of the low potential driving voltage EVSS, and an organic compound layer positioned between the anode electrode and the cathode electrode. A parasitic capacitor (Coled) is generated in the OLED by the anode electrode, the cathode electrode, and a plurality of insulating films existing therebetween. The capacitance of this OLED parasitic capacitor (Coled) is a few pF, which is very small compared to the parasitic capacitance existing in the sensing line 14B, which is several hundred to several thousand pF.

The driving TFT DT controls the amount of current input to the OLED according to the gate-source voltage Vgs. The driving TFT DT has a gate electrode connected to the gate node Ng, a drain electrode connected to the input terminal of the high potential driving voltage EVDD, and a source electrode connected to the source node Ns. The storage capacitor Cst is connected between the gate node Ng and the source node Ns. The first switch TFT (ST1) applies a data voltage (Vdata) on the data line (14A) to the gate node (Ng) in response to the gate signal (SCAN). The first switch TFT ST1 has a gate electrode connected to the gate line 15, a drain electrode connected to the data line 14A, and a source electrode connected to the gate node Ng. The second switch TFT (ST2) switches the current flow between the source node (Ns) and the sensing line (14B) in response to the gate signal (SCAN). The second switch TFT ST2 has a gate electrode connected to the gate line 15, a drain electrode connected to the sensing line 14B, and a source electrode connected to the source node Ns.

The sensing unit 122 connected to such a subpixel P may include a reference voltage control switch SW1, a sampling switch SW2, and a sample and hold unit S / H. The reference voltage control switch SW1 switches the electrical connection between the input terminal of the reference voltage Vref and the sensing line 14B in accordance with the reference voltage control signal PRE. The sampling switch SW2 switches the electrical connection between the sensing line 14B and the sample and hold portion S / H in accordance with the sampling control signal SAM.

The reference voltage control switch SW1 is turned on for the first period and the second period, and is turned off in the third period after applying the reference voltage to the sensing line 14B. The sampling switch SW2 is turned on at a specific point in the third period to electrically connect the sensing line 14B to the sample and hold section S / H.

As will be described later, when the discharge path is formed between the OLED and the sensing line 14B for the sensing operation, the discharge speed of the reference voltage charged in the line capacitor LCa of the sensing line 14B depends on the operating point voltage of the OLED . That is, the voltage magnitude remaining in the line capacitor LCa varies depending on the degree of deterioration of the OLED. While the sampling switch SW2 is turned on at a specific point in the third period, the sample and hold unit S / H samples and holds the voltage remaining in the line capacitor LCa of the sensing line 14B as a sensing voltage ADC.

Hereinafter, a method of sensing deterioration of an OLED display according to an exemplary embodiment of the present invention will be described in detail with reference to an exemplary configuration of the OLED display.

[Deterioration Sensing Method for Subpixel to be Sensed]

FIG. 6 shows a method of perturbation sensing of the present invention for a subpixel to be sensed. FIG. 7 shows the control signal waveform and the potential change waveform for each section before and after deterioration when FIG. 6 is applied to FIG. 8A to 8C show the operation of the subpixel and the sensing unit in the first period, the second period, and the third period, respectively, in Fig.

Referring to FIGS. 6 and 7, the degradation sensing method of the present invention for a subpixel to be sensed includes an initialization step S10 in a first period Tint, an operation point setting step S20 in a second period Tbst, , And a sensing step S30 in the third period Tsen. During the sensing operation, the data driving circuit 12 supplies the data lines 14A with a first sensing data voltage (for example, a black gradation data voltage, 0.5V) capable of turning off the driving TFT DT.

As shown in FIG. 8A, in the first period Tint, the gate signal SCAN having the first gate high voltage VGH1 of the first level (24V) is applied to the first and second switches The TFTs ST1 and ST2 are turned on. In the first period Tint, the reference voltage control switch SW1 is turned on and the sampling switch SW2 is turned off.

The first sensing data voltage (black gradation data voltage, 0.5V) which can turn off the driving TFT DT is applied to the gate line of the driving TFT DT included in the sub pixel to be sensed in the data line 14A (Ng). The reference voltage Vref of the first level (LV1, 9V) higher than the OLED operating point voltage is applied to the source node Ns of the driving TFT DT through the sensing line 14B.

As a result, in the first period Tint, the driving TFT DT is turned off, and the OLED of the subpixel to be sensed is turned on.

The first and second switch TFTs ST1 and ST2 turn on according to the gate signal SCAN having the gate-low voltage VGL of the second level (-6V) in the second period Tbst as shown in Fig. 8B, Off. At this time, the reference voltage control switch SW1 is turned on and the sampling switch SW2 is turned off.

Accordingly, the anode terminal (source node Ns of the driving TFT) of the OLED is floated in the second period Tbst. The OLED emits light by the current supplied to the OLED by the reference voltage (Vref) of the first level (LV1, 9V) stored in the anode terminal. The voltage at the anode end of the OLED (the source node voltage of the driving TFT) is lowered from the reference voltage Vref at the first level (LV1, 9V) to the operating point voltage of the OLED by the current flowing through the OLED. At this time, the voltage of the OLED operating point depends on the degree of deterioration of the OLED. For example, the OLED operating point voltage may be 8 V before OLED degradation, while 8.5 after OLED degradation. And the gate node Ng of the driving TFT also floats in the second period Tbst. Since the gate node Ng of the driving TFT is coupled to the anode terminal of the OLED via the storage capacitor Cst, the potential of the gate node Ng is also decreased in proportion to the potential change of the anode terminal of the OLED. For example, when the potential of the anode terminal of the OLED changes from 9V to 8V, the potential of the gate node Ng of the driving TFT may also change from 0.5V to -0.5V, and the potential of the anode terminal of the OLED is 9V The potential of the gate node Ng of the driving TFT may also change from 0.5 V to 0 V. [

On the other hand, in the second period Tbst, the reference voltage Vref of the second level (LV2, 14V) higher than the first level (LV1, 9V) is charged in the sensing line 14B.

The first and second switch TFTs ST1 and ST2 are turned off according to the gate signal SCAN having the second gate high voltage VGH2 of the third level 11V in the third period Tsen, Turn on. Then, the reference voltage control switch SW1 is turned off, and the sampling switch SW2 is turned on at a specific point in time (sampling point).

The second gate high voltage VGH2 of the third level 11V is higher than the OLED operating point voltage and lower than the reference voltage Vref of the second level LV2 and 14V so that a smooth discharge operation can be performed. A first sensing data voltage (a black gradation data voltage, for example, 0.5 V) is applied to the gate node Ng of the driving TFT DT in the third period Tsen so as to turn off the driving TFT DT Thereby preventing the driving TFT DT from affecting the OLED sensing value. In the third period Tsen, the sensing line 14B is electrically disconnected from the reference voltage Vref input terminal and electrically connected to the anode terminal of the OLED through the second switch TFT ST2. Accordingly, the reference voltage Vref of the second level (LV2, 14V) charged in the sensing line 14B is discharged through the OLED and sensing is performed. By this discharge, the anode potential of the OLED rises from the OLED operating point voltage. (Vgs, 11V-8V = 3V) between the gate and the source of the second switch TFT (ST2) is relatively large in the case where the OLED operating point voltage is low before degradation, the amount of current discharged through the second switch TFT (That is, the discharge rate is relatively fast). On the other hand, since the voltage (Vgs, 11V-8.5V = 2.5V) between the gate and source of the second switch TFT (ST2) is relatively small when the OLED operating point voltage is high, the second switch TFT (That is, the discharge rate is relatively slow) compared with that before the deterioration. The voltage remaining in the sensing line 14B changes due to the difference in the discharge speed depending on the degree of deterioration. Therefore, when the sampling switch SW2 is turned on at a specific point in time (sampling time), the residual voltage of the sensing line 14B is sensed, and the sensed value is compared with the initial value before deterioration.

[Deterioration Sensing Exclusion Method for Non-Sensing Sub-Pixel]

FIG. 9 shows a method of excluding the deterioration sensing of the present invention for non-sensing subject subpixels. FIG. 10 shows control signal waveforms and potential change waveforms for each section before and after deterioration when FIG. 9 is applied to FIG. 11A to 11C show the operation of the subpixel and the sensing unit in each of the first period, the second period, and the third period in FIG.

In the deterioration sensing method for the subpixel to be sensed, the OLED deterioration is sensed while discharging the reference voltage Vref charged in the sensing line 14B through the OLED. In the sensing line shared structure, subpixels that should not be sensed can also be emitted by the reference voltage Vref and sensed together. However, the present invention uses a gate signal (SCAN) applied to the second gate high voltage (VGH2) of the third level (11V) in the third period (Tsen) so that the sub pixel of the non-sensing object affects the OLED degradation sensing value Effectively eliminating the influence and increasing the accuracy of the sensing. This will be described in detail below.

9 and 10, the degradation sensing method for a non-sensing target subpixel of the present invention includes an initializing step S10 in a first period Tint, a boosting step S20 in a second period Tbst, , And a sensing exclusion step (S30) in the third period (Tsen). During the sensing operation, the data driving circuit 12 supplies the data lines 14A with a second sensing data voltage (for example, white gradation data voltage, 16V) capable of turning on the driving TFT DT.

As shown in FIG. 11A, in the first period Tint, the gate signal SCAN having the first gate high voltage VGH1 of the first level 24V is applied to the first and second switch TFTs of the non- (ST1, ST2) are turned on. In the first period Tint, the reference voltage control switch SW1 is turned on and the sampling switch SW2 is turned off.

The second sensing data voltage 16V capable of turning on the driving TFT DT is applied to the gate node Ng of the driving TFT DT included in the unselected subpixel in the data line 14A . The reference voltage Vref of the first level (LV1, 9V) higher than the OLED operating point voltage is applied to the source node Ns of the driving TFT DT through the sensing line 14B.

As a result, the driving TFT DT and the OLEDs included in the non-sensing subpixel are turned on in the first period Tint.

The first and second switch TFTs ST1 and ST2 turn on according to the gate signal SCAN having the gate-low voltage VGL of the second level (-6V) in the second period Tbst as shown in Fig. 11B, Off. At this time, the reference voltage control switch SW1 is turned on and the sampling switch SW2 is turned off.

In this second period Tbst, the gate node Ng of the driving TFT DT is electrically disconnected from the data line 14A, and the source node Ns of the driving TFT DT is connected to the sensing line 14B are disconnected from each other. The driving TFT DT generates the driving current by the gate-source voltage Vgs set in the first period Tint. The anode potential of the OLED (that is, the source node Ns potential of the driving TFT DT) is boosted (boosted at 9V to 14V, for example) by this driving current and is also supplied through the storage capacitor Cst The potential at the gate node Ng of the driving TFT DT coupled to the node Ns is also boosted (boosted to, for example, 18V at 16V).

On the other hand, in the second period Tbst, the reference voltage Vref of the second level (LV2, 14V) higher than the first level (LV1, 9V) is charged in the sensing line 14B.

The first and second switch TFTs ST1 and ST2 are turned off according to the gate signal SCAN having the second gate high voltage VGH2 of the third level 11V in the third period Tsen, Off. Then, the reference voltage control switch SW1 is turned off, and although not shown, the sampling switch SW2 is turned on at a specific point in time (sampling point).

The second gate high voltage VGH2 of the third level (11V) applied to the gate electrode of the first switch TFT (ST1) in the third period Tsen is the same as the second gate high voltage VGH2 of the drive TFT boosted in the second period Tbst Is lower than the gate potential (18V), that is, the source potential (18V) of the first switch TFT (ST1). The gate-source voltage Vgs of the first switch TFT (ST1) is -7V, which is lower than the threshold voltage of the first switch TFT (ST1), so that the first switch TFT (ST1) is turned off.

The second gate high voltage VGH2 of the third level (11V) applied to the gate electrode of the second switch TFT (ST2) in the third period Tsen is the OLED anode potential boosted in the second period Tbst 14V, that is, lower than the source potential (14V) of the second switch TFT (ST2). The gate-source voltage Vgs of the second switch TFT (ST2) is -3V, which is lower than the threshold voltage of the second switch TFT (ST2), so that the second switch TFT (ST2) is turned off.

When the second switch TFT (ST2) is turned off in the third period Tsen, the electrical connection between the sensing line 14B and the OLED anode terminal of the non-sensing subpixel is continuously interrupted. Accordingly, a discharge path between the sensing line 14B and the OLED anode terminal of the non-sensing subpixel is not formed. As a result, the second level LV2, which is charged in the sensing line 14B in the second period Tbst, The reference voltage Vref of 14V is not changed by the non-sensing target subpixel during the third period Tsen. By doing so, the present invention can selectively sense only the OLED deterioration of the subpixels to be sensed.

FIG. 12 is a simulation result showing a sensing value according to deterioration of an OLED when the present invention is applied, and FIG. 13 is a graph showing a difference in sensing value according to a sensing time.

Referring to FIG. 12, it can be seen that as the deterioration of the OLED increases, the sensing value Vsen increases. In addition, when applying the present invention, the sensing resolution may be increased by increasing the sensing time (corresponding to the length of Tsen in FIGS. 7 and 10) as shown in FIG.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or 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.

10: Display panel 11: Timing controller
12: data driving circuit 13: gate driving circuit
14A: Data line 14B: Sensing line
15: gate line

Claims (6)

An OLED, a driving TFT connected between the anode ends of the OLED, a switch TFT connected to the driving TFT, and a sensing unit connected to the sensing target sub-pixel through a sensing line. In a deterioration sensing method for a light emitting device,
Turning on the OLED by applying a reference voltage of a first level higher than the OLED operating point voltage to the anode terminal of the OLED connected to the source electrode of the driving TFT in the sensing unit during the first period ;
Wherein the OLED includes a plurality of OLEDs, each of the plurality of OLEDs including a plurality of OLEDs, each of the plurality of OLEDs including a plurality of OLEDs, ; And
The sensing line is electrically connected to the anode terminal of the OLED during the third period to discharge the second level reference voltage charged in the sensing line through the OLED, And sensing a remaining voltage of the organic light emitting display device. The method according to claim 1,
And applying a first sensing data voltage lower than the reference voltage of the first level to the gate electrode of the driving TFT in the first period to turn off the driving TFT. The method according to claim 1,
The switch TFT includes a first switch TFT connected between a data line and a gate electrode of the drive TFT and turned on / off in response to a gate signal, and a second switch TFT connected between the source electrode of the drive TFT and the sensing line, And a second switch TFT which is turned on / off,
Wherein the gate signal comprises a first gate high voltage, a gate low voltage lower than the first gate high voltage, and a second gate high voltage higher than the gate low voltage and lower than the first gate high voltage to a three voltage level A method of sensing deterioration of a light emitting device of an organic light emitting display device. The method of claim 3,
Wherein the gate signal comprises:
Wherein the first gate high voltage is applied to the first gate high voltage in the first period, the gate low voltage is applied in the second period, and the second gate high voltage is applied in the third period, Deterioration Sensing Method for. The method of claim 3,
Wherein the second gate high voltage is higher than the OLED operating point voltage and lower than the reference voltage of the second level. The method according to claim 1,
If the non-sensing target subpixel included in one unit pixel and the sensing target subpixel share the same sensing line,
In the first period, a second sensing data voltage higher than the first level reference voltage is applied to the gate electrode of the first driving TFT included in the non-sensing target subpixel to turn on the first driving TFT And turning on the first OLED by applying the reference voltage of the first level higher than the OLED operating point voltage to the anode terminal of the first OLED included in the non-sensing subpixel through the sensing line ,
Further comprising the step of floating the anode end of the first OLED to boost the anode potential of the first OLED to a level higher than the reference voltage of the first level in the second period,
And electrically disconnecting the sensing line and the anode terminal of the first OLED during the third period.

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