KR101581593B1 - Degradation Sensing Method of Organic Light Emitting Display - Google Patents

Abstract

A deterioration sensing method of an organic light-emitting display apparatus of the present invention comprises an initialization step, a discharge step, and a sensing step. In the initialization step, a driving thin film transistor (TFT) is turned off, and first initialized voltage which is greater than voltage of an operation point of an organic device is applied to a source node from a sensing unit so as to emit the organic device. In the discharge step, the source node is floated to decrease potential of the source node down to the voltage of the operation point, and electric charge which proportionates to the voltage of the operation point is stored in a parasitic capacitor of the organic device. Furthermore, in the sensing step, second initialization voltage which is lower than the voltage of the operation point is applied to the source node from the sensing unit in an off-state of the driving TFT so as to sense the electric charge stored in the parasitic capacitor of the organic device.

Description

[0001] The present invention relates to a method of sensing a degradation of an organic light-

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to an organic light emitting diode (OLED) display, and more particularly,

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

The organic light emitting diode (OLED) 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).

Generally, OLEDs have deterioration characteristics in which the operating point voltage (threshold voltage) of the OLED increases and the luminous efficiency decreases as the emission time elapses. Since the current accumulation value applied to the OLED of each subpixel is proportional to the gray accumulation value implemented in the corresponding subpixel, the OLED degradation degree 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, a compensation scheme for sensing the OLED deterioration and modulating video data in an external circuit based on the sensed value is known.

However, the conventional OLED display has the following problems.

First, in the conventional OLED display device, a driving current is generated by driving a driving TFT of each pixel with a constant sensing data voltage, and the anode voltage of the OLED (i.e., the source voltage of the driving TFT) And the degree of deterioration of the OLED of the corresponding pixel was determined. In such a conventional organic light emitting diode display, the change in the electrical characteristics of the driving TFT is compensated for prior to the deterioration sensing for the OLED, thereby improving the accuracy of OLED deterioration sensing. However, since the change in the electrical characteristics of the driving TFT can not be completely compensated, there is a limitation in securing the accuracy of sensing in the technology of sensing the deterioration of the OLED based on the driving current. That is, even if the degree of deterioration of the OLED is the same, if the compensation for the change in the electrical characteristics of the driving TFT is insufficient, an error will occur in the deterioration sensing value, and it is difficult to improve the accuracy of the deterioration sensing in the conventional OLED display.

Second, the sensing line can have a sensing line independent structure or a sensing line sharing structure according to 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. In this structure, the OLED can be individually operated, and the degree of deterioration of the OLED can be directly sensed. However, since the sensing line is arranged for each subpixel, the aperture ratio is reduced and the current density of the OLED is increased during driving. Therefore, in the conventional OLED display device having this structure, the deterioration rate of the OLED is increased and the lifetime is 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. In the conventional OLED display device having this structure, it is impossible to accurately sense the degree of deterioration of each OLED because the OLED can not be individually operated during the deterioration sensing (that is, the OLEDs in the unit pixel are simultaneously operated).

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 accomplish the above object, according to an embodiment of the present invention, there is provided an organic electroluminescent device including an organic element, a current control unit controlling current flowing between an input terminal of a high potential driving voltage and a source node according to a potential of a gate node, A plurality of subpixels each having a driving TFT, and a sensing unit connected to at least any one of the subpixels through a sensing line, includes an initialization step, a discharging step and a sensing step. In the initialization step, the driving TFT is turned off and a first initializing voltage higher than the operating point voltage of the organic element is applied to the source node in the sensing unit to emit the organic element. In the discharging step, the source node is floated to lower the potential of the source node to the operating point voltage, and a charge amount proportional to the operating point voltage is stored in the parasitic capacitor of the organic device. In the sensing step, the second initializing voltage lower than the operating point voltage is applied to the source node in the sensing unit while the driving TFT is turned off to sense the amount of charge stored in the parasitic capacitor of the organic device.

The sensing step senses the amount of charge stored in the parasitic capacitor of the organic device according to the current sensing method using the current integrator included in the sensing unit.

When the subpixels constituting one unit pixel among the subpixels share one sensing line, in the initializing step and the sensing step, the driving TFT is turned on to the gate node of the subpixel to be sensed among the unit pixels Off voltage that can be turned off.

The white gradation data voltage capable of turning on the driving TFT is applied to the gate node of the remaining subpixels of the unit pixels excluding the sensing target subpixel in the initializing step and the sensing step, The source node of the remaining sub-pixel and the sensing line are kept at the same potential to prevent the charge from moving from the source node of the remaining sub-pixel to the sensing unit.

The high-potential driving voltage is selected to have the same voltage level as the second initializing voltage.

In order to sense OLED deterioration, a constant voltage is applied from a sensing unit to a source node (anode end of an OLED) of a driving TFT in a state in which the driving TFT is off, thereby emitting light to the OLED and sensing a change in the OLED operating point. Since the present invention does not need to apply the driving current from the driving TFT to the OLED in order to sense the deterioration of the OLED, the influence of the driving TFT can be excluded and the accuracy of the sensing can be greatly increased.

FIG. 1 is a view illustrating an organic light emitting display according to an embodiment of the present invention. FIG.
2A and 2B are views showing examples of connection of a sensing line and a sub-pixel.
FIGS. 3 and 4 are diagrams showing a configuration example of a panel 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.
6 is a diagram illustrating a method for sensing a deterioration of a sensing subpixel of the present invention.
FIG. 7 is a diagram showing a control signal waveform and a potential change waveform for each section 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 initialization period, the discharge period, and the sensing period of FIG. 7, respectively.
9 is a diagram illustrating a method of perturbing sensing of the present invention for non-sensing subpixels.
FIG. 10 is a diagram showing control signal waveforms and potential change waveforms for respective sections when FIG. 9 is applied to FIG. 5;
FIGS. 11A to 11C are diagrams showing the operation of the subpixel and the sensing unit in the initialization period, the discharge period, and the sensing period, respectively, in FIG. 10;
12 is a view showing a comparison of a sensing error according to a threshold voltage deviation of a driving TFT with a conventional one.
13 is a view showing a comparison of a sensing error according to a mobility deviation of a driving TFT with a conventional one.
14 is a view showing a comparison of a sensing error according to a threshold voltage deviation of the first switch TFT with a conventional one.
15 is a view showing a comparison of a sensing error according to a mobility deviation of the first switch TFT with a conventional one.

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 examples of the configuration of the panel 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 the sub pixels P are arranged in a matrix form in each of the intersection areas . The gate lines 15 are connected to a plurality of first gate lines 15A to which a scan control signal SCAN is sequentially supplied and a plurality of first gate lines 15A to which a sensing control signal SEN is sequentially supplied And second gate lines 15B.

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 is connected to one of the data lines 14A, to one of the sensing lines 14B and to one of the first gate lines 15A, to the second gate lines 15B Or the like. Each subpixel P is electrically connected to the data line 14A in response to a scan control signal SCAN input through the first gate lines 15A to generate a data voltage for sensing from the data line 14A And can output a sensing signal through the sensing line 14B.

According to the sensing line independent structure, the sensing line 14B can be independently connected to each horizontally adjacent sub-pixel as shown in FIGS. 2A and 3B. 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.

Meanwhile, according to the sensing line sharing structure, the sensing line 14B may be connected to a plurality of subpixels constituting one unit pixel horizontally adjacent to each other as shown in FIG. 2B and FIG. 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 driver TFT, first and second switch TFTs, and a storage capacitor for external compensation. The TFTs constituting the subpixel P may be implemented as a p-type or an n-type. 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 normal driving for the display image implementation and at the sensing operation for sensing value acquisition. The sensing drive may be performed from immediately after the system power is turned on to a predetermined time before the normal drive, or may be performed in the vertical blank periods during the normal drive. Also, the sensing drive may be performed for a predetermined time immediately after the normal drive is completed, before the system 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.

Each of the sensing units SU # 1 to SU # k of the data driver IC (SDIC) may be connected to the sensing line 14B on a one-to-one basis. The number of the sensing lines 14B and the sensing units SU # 1 to #k 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.

As described below, in the deterioration sensing method of the present invention, a constant voltage (that is, an initializing voltage) is applied from the sensing unit 122 to the source node of the driving TFT (i.e., the anode terminal of the OLED) And the amount of charge stored in the parasitic capacitor of the OLED is sensed to determine the change (deterioration) 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.

The deterioration sensing method of the present invention includes a current integrator in the sensing unit 122 and realizes a low current and a high speed sensing through a current sensing method, thereby greatly reducing sensing time.

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 applied. (For example, a black gradation data voltage capable of turning off a driving TFT) applied to sub pixels to be sensed and a sensing data voltage The OLED deterioration of the subpixels to be sensed can be selectively sensed.

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

The gate driving circuit 13 may generate a scan control signal based on the gate control signal GDC during the sensing operation and then supply the scan control signal to the first gate lines 15A in a row sequential manner. The gate driving circuit 13 may generate a sensing control signal based on the gate control signal GDC during the sensing operation and then supply the sensing control signal to the second gate lines 15B in a row sequential manner.

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 control signal DDC for controlling the timing and a gate control signal GDC for controlling the operation timing of the gate drive circuit 13 are generated. The timing controller 11 separates the normal driving and the sensing driving based on a predetermined reference signal (driving power enable signal, vertical synchronizing signal, data enable signal, etc.), and outputs the data control signal DDC and the gate The control signal GDC can be generated. In addition, the timing controller 11 outputs related switching control signals CON (switches SAM and HOED in FIG. 5) to operate the internal switches of the sensing units SU # 1 to # k in accordance with the normal driving and the sensing driving And a control signal).

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 calculates compensation data that can compensate for the OLED deterioration of each subpixel P on the basis of the digital sensing value SD transmitted from the data driving circuit 12 in the sensing operation, May be stored in the memory (16). The timing controller 11 can transmit digital video data (RGB) for image display to the data driving circuit 12 after modulating the compensation data stored in the memory 16 during normal driving.

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 N2, 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 present invention utilizes an OLED parasitic capacitor (Coled) for current sensing.

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 N1, a drain electrode connected to the input terminal of the high potential driving voltage EVDD, and a source electrode connected to the source node N2. The storage capacitor Cst is connected between the gate node N1 and the source node N2. The first switch TFT ST1 applies the data voltage Vdata on the data line 14A to the gate node N1 in response to the scan control signal SCAN. The first switch TFT ST1 has a gate electrode connected to the first gate line 15A, a drain electrode connected to the data line 14A, and a source electrode connected to the gate node N1. The second switch TFT (ST2) switches the current flow between the source node (N2) and the sensing line (14B) in response to the sensing control signal (SEN). The second switch TFT ST2 has a gate electrode connected to the second gate line 15B, a drain electrode connected to the sensing line 14B, and a source electrode connected to the source node N2.

Also, the sensing unit (SU # k, k is a positive integer) connected to the subpixel P may include a current integrator (CI) and a sample and hold unit (SH).

The current integrator CI integrates the current information Ipixel inputted from the subpixel P to be sensed to generate the sensing voltage Vsen. The current integrator CI applies the initialization voltage Vpre to the source node N2 through the sensing line 14B and supplies the current information Ipixel of the subpixel to be sensed through the sensing line 14B, An inverting input terminal (-) for receiving the charge charged in the OLED parasitic capacitor (Coled) of the pixel P, a non-inverting input terminal (+) for receiving the initialization voltage Vpre, and an amplifier (AMP) An integral capacitor Cfb connected between the inverting input terminal (-) and the output terminal of the amplifier AMP and a reset switch RST connected to both ends of the integrating capacitor Cfb.

The current integrator (CI) is connected to the ADC through a sample and hold section (SH). The sample-and-hold unit SH includes a sampling switch SAM for sampling a sensing voltage Vsen output from the amplifier AMP and storing the sampled voltage Vsen in the sampling capacitor Cs, a sensing voltage Vsen stored in the sampling capacitor C, And a holding switch (HOLD) for transmitting to the ADC.

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

FIG. 6 shows a method of sensing a deterioration of the present invention for a sensing subpixel. FIG. 7 shows the control signal waveform and the potential change waveform for each section when FIG. 6 is applied to FIG. 8A to 8C show the operation of the subpixel and the sensing unit in the initialization period, the discharge period, and the sensing period of FIG. 7, respectively.

Referring to FIGS. 6 and 7, a deterioration sensing method for a sensing subpixel of the present invention includes an initializing step S10 in an initialization period Tini, a discharging step S20 in a discharging period Tdis, And a sensing step S30 performed in a sensing period Tsen.

In the initialization period Tint, the first switch TFT ST1 is turned on in accordance with the scan control signal SCAN of the on level so that the data voltage for sensing (hereinafter referred to as " Data voltage V_black ') (for example, 0.5 V) to the gate node N1 of the driving TFT DT. The second switch TFT ST2 is turned on in response to the on-level sensing control signal SEN to be supplied with a first initializing voltage V_HIGH higher than the OLED operating point voltage For example, 7 V) is applied.

In the initialization period Tint, due to the turning on of the reset switch RST, the amplifier AMP operates as a unit gain buffer having a gain of 1 and is connected to the input terminals (+, -) and output terminal of the amplifier AMP, The line 14B is all initialized to the first initializing voltage V_HIGH.

In this initialization step S10, the driving TFT DT is turned off and a first initializing voltage V_HIGH (V) higher than the OLED operating point voltage is applied to the source node N2 of the driving TFT DT in the sensing unit SU ) To turn on the OLED. As a result, the current flowing through the OLED causes the OLED to emit light, and the parasitic capacitor of the OLED begins to charge.

The first switch TFT ST1 is turned off according to the scan control signal SCAN of the off level in the discharge period Tdis and the second switch TFT ST2 is turned on in accordance with the off level sensing control signal SEN Off. As a result, the source node N2 of the driving TFT DT is floated and the potential of the source node N2 is lowered from the first initializing voltage V_HIGH to the operating point voltage of the OLED. The operating point voltage V of the OLED varies depending on the degree of deterioration of the OLED (the operating point voltage V_OP2 after deterioration is higher than the operating point voltage V_OP1 before deterioration), and thus the parasitic capacitor Coled of the OLED, (Q = CV) The amount of charge (Q = CV, C is the parasitic capacitance) proportional to the operating point voltage of the OLED is stored in the parasitic capacitor (Coled) of the OLED.

During the discharge period Tdis, a second initializing voltage V_LOW lower than the operating point voltage of the OLED is applied to the non-inverting input terminal (+) of the amplifier AMP. The second initializing voltage V_LOW may be selected to be the same voltage level as the high potential driving voltage EVDD (for example, 4 V) so that smooth sensing can be performed.

In the discharge period Tdis, the amplifier AMP continues to operate as a unit gain buffer, and the potentials of the input terminals (+, -) and the output terminal of the amplifier AMP are maintained at the first The second initializing voltage V_LOW is maintained during the remaining period of the discharge period Tdis after the initialization voltage V_HIGH is maintained.

In this discharging step S20, the amount of charge proportional to the operating point voltage of the OLED is stored in the parasitic capacitor (Coled) of the OLED while the driving TFT (DT) is turned off as shown in FIG. 8B.

The first switch TFT ST1 is turned on in accordance with the scan control signal SCAN of the on level in the sensing period Tsen and the second switch TFT ST2 is turned on according to the on level control signal SEN, do. The black gradation data voltage V_black is applied again to the gate node N1 of the driving TFT DT through the first switch TFT ST1 to turn off the driving TFT DT to sense the deterioration of the OLED And the influence of the driving TFT is excluded. The amplifier AMP operates as a current integrator CI due to the turning off of the reset switch RST. The charge stored in the parasitic capacitor (Coled) of the OLED is stored in the integrated capacitor (Cfb) of the current integrator (CI) through the second switch TFT (ST2).

The potential difference between the both ends of the integrating capacitor Cfb is increased by the charge flowing into the inverting input terminal (-) of the amplifier AMP in the sensing period Tsen as the sensing time elapses, that is, the accumulated amount of current Ipixel increases. Since the inverting input terminal (-) and the non-inverting input terminal (+) are short-circuited through the virtual ground due to the characteristics of the amplifier AMP and the potential difference between them is zero, the inverting input terminal -) is maintained at the reference voltage Vpre regardless of the increase in the potential difference of the integrating capacitor Cfb. Instead, the output terminal potential of the amplifier AMP is lowered corresponding to the potential difference between both ends of the integral capacitor Cfb. In this case, the electric charge flowing through the sensing line 14B in the sensing period Tsen is changed into the sensing voltage Vsen, which is an integral value, through the integrating capacitor Cfb. In this case, the sensing voltage Vsen becomes the second initializing voltage V_LOW). This is due to the input / output characteristics of the current integrator (CI).

In this sensing step S30, as shown in FIG. 8C, the charge stored in the parasitic capacitor (Coled) of the OLED is sensed through a current sensing method using a current integrator (CI) to obtain a sensing voltage Vsen as an integral value.

The capacitance of the integrating capacitor Cfb included in the sensing unit SU of the present invention is as small as a hundredth of the parasitic capacitance existing in the sensing line 14B, There is a possible advantage.

On the other hand, the amount of charge charged in the OLED parasitic capacitor (Coled) is proportional to the OLED operating point voltage. That is, as OLED degradation increases, the OLED operating point voltage increases and the amount of charge charged in the OLED parasitic capacitor (Coled) also increases. On the other hand, the sensing voltage Vsen output from the current integrator CI may be inversely proportional to the OLED operating point voltage due to the input / output characteristics of the current integrator CI. That is, as the OLED degradation increases, the sensing voltage Vsen output from the current integrator CI can be reduced.

FIG. 9 shows a method of detecting a deterioration of a non-sensing subpixel according to the present invention. FIG. 10 shows the control signal waveform and the potential change waveform for each section when FIG. 9 is applied to FIG. 11A to 11C show the operation of the subpixel and the sensing unit in each of the initialization period, the discharge period, and the sensing period in FIG.

In the deterioration sensing method for the subpixel to be sensed, the OLED is emitted using the initialization voltage. In the sensing line shared structure, the subpixels that should not be sensed due to the initialization voltage may also emit light and be sensed together. However, in the present invention, the charge is shifted from the source node of the drive TFT to the sensing unit 122 by turning on the driver TFT in the unselected subpixels and keeping the source node of the driver TFT and the sensing line 14B at the equal potential It is possible to effectively prevent influence by the sub-pixels to be non-sensed. This will be described in detail below.

9 and 10, a deterioration sensing method for a non-sensing subpixel according to the present invention includes an initializing step S10 in an initialization period Tini, a discharging step S20 in a discharging period Tdis, And a sensing step S30 in a sensing period Tsen.

In the initialization period Tint, the first switch TFT ST1 is turned on in accordance with the scan control signal SCAN of the on level so that the data voltage for sensing (hereinafter, (For example, 9V) to the gate node N1 of the driving TFT DT. The second switch TFT ST2 is turned on in response to the on-level sensing control signal SEN to be supplied with a first initializing voltage V_HIGH higher than the OLED operating point voltage For example, 7 V) is applied.

In this initialization step S10, the driving TFT DT is turned on as shown in FIG. 11A, and a first initializing voltage (a second initializing voltage) is applied to the source node N2 of the driving TFT DT in the sensing unit SU V_HIGH) to turn on the OLED. As a result, the current flowing through the OLED causes the OLED to emit light.

The first switch TFT ST1 is turned off according to the scan control signal SCAN of the off level in the discharge period Tdis and the second switch TFT ST2 is turned on in accordance with the off level sensing control signal SEN Off. At this time, since the driving TFT DT is turned on, the potential of the source node N2 of the driving TFT DT is lowered from the first initializing voltage V_HIGH to the high potential driving voltage EVDD (for example, 4V).

During the discharge period Tdis, a second initializing voltage V_LOW lower than the operating point voltage of the OLED is applied to the non-inverting input terminal (+) of the amplifier AMP. The second initialization voltage V_LOW may be selected to be the same voltage level (e.g., 4V) as the high potential drive voltage EVDD so that undesired sensing is not performed.

In this discharging step S20, the potential of the source node N2 of the driving TFT DT is lowered to the high potential driving voltage EVDD while the driving TFT DT is turned on as shown in Fig. 11B, and the sensing unit SU The potential of the sensing line 14B is lowered from the first initializing voltage V_HIGH to the second initializing voltage V_LOW, that is, the high potential driving voltage EVDD.

The first switch TFT ST1 is turned on in accordance with the scan control signal SCAN of the on level in the sensing period Tsen and the second switch TFT ST2 is turned on according to the on level control signal SEN, do. The white gradation data voltage V_white is again applied to the gate node N1 of the driving TFT DT through the first switch TFT ST1 to turn on the driving TFT DT to turn on the driving TFT DT. The potential of the source node N2 is maintained at the high potential driving voltage EVDD. At this time, since the source node N2 of the driving TFT DT is at the same potential as the sensing line 14B, the charge is prevented from moving from the source node N2 of the driving TFT DT to the sensing unit SU .

In this sensing step S30, the source node N2 of the driving TFT DT and the sensing line 14B are kept at the same potential and the charge is moved from the source node N2 to the sensing unit SU as shown in Fig. Thereby preventing the source potential of the sub-pixel to be non-sensed from affecting the deterioration sensing value for the sub-pixel to be sensed.

12 and 13 show a comparison of the sensing error according to the electrical characteristic deviation of the driving TFT with the conventional one. Figs. 14 and 15 show a comparison of the sensing error according to the electrical characteristic deviation of the first switch TFT with the conventional one.

In order to sense OLED deterioration, a constant voltage is applied from a sensing unit to a source node (anode end of an OLED) of a driving TFT in a state in which the driving TFT is off, thereby emitting light to the OLED and sensing a change in the OLED operating point. Since the present invention does not need to apply the driving current from the driving TFT to the OLED in order to sense the OLED deterioration, the threshold voltage deviation of the driving TFT, the drift deviation of the driving TFT, The threshold voltage deviation of the first switch TFT and the mobility deviation of the first switch TFT are freed. Therefore, the present invention has a great effect in improving the sensing error.

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 (5)

An organic element, a plurality of sub-pixels each having a driving TFT connected to the organic element through the source node to control a current flowing between an input terminal and a source node of the high-potential driving voltage according to the potential of the gate node, A method of sensing a deterioration of an organic light emitting display including a sensing unit connected to at least one of subpixels,
An initialization step of turning off the driving TFT and applying a first initialization voltage higher than an operating point voltage of the organic element to the source node in the sensing unit to emit the organic element;
A discharging step of floating the source node to lower the potential of the source node to the operating point voltage and storing a charge proportional to the operating point voltage in the parasitic capacitor of the organic device; And
And a sensing step of sensing the amount of charge stored in the parasitic capacitor of the organic device by applying a second initialization voltage lower than the operating point voltage to the source node in the sensing unit while the driving TFT is turned off A method of sensing deterioration of an organic light emitting display device. The method according to claim 1,
Wherein the sensing step senses the amount of charge stored in the parasitic capacitor of the organic device according to a current sensing scheme using the current integrator included in the sensing unit. The method according to claim 1,
When subpixels constituting one unit pixel among the subpixels share one sensing line,
And a black gradation data voltage capable of turning off the driving TFT is applied to a gate node of a subpixel to be sensed among the unit pixels in the initialization step and the sensing step . The method of claim 3,
Applying a white gradation data voltage capable of turning on the driving TFT to a gate node of the remaining subpixels of the unit pixels excluding the sensing target subpixel in the initializing step and the sensing step;
Wherein the source node of the remaining sub-pixel and the sensing line are kept at the same potential so that charge is prevented from moving from the source node of the remaining sub-pixel to the sensing unit in the sensing step. Sensing method. The method according to claim 1,
Wherein the high-potential driving voltage is selected to be the same voltage level as the second initialization voltage.

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