KR102374752B1 - Driving Method Of Organic Light Emitting Display - Google Patents

Abstract

The present invention provides the steps of outputting a sensing scan signal to on level, off level, and on level in each of the successive data writing period, boosting period, and sensing period, and in the data writing period, the electrical characteristics of the driving TFT An on-level first sensing data voltage is supplied to the gate electrode of the driving TFT, and an off-level second sensing data voltage according to electrical characteristics of the driving TFT is applied to the gate electrode of the driving TFT during the sensing period. supplying; supplying an initialization voltage to the source electrode of the driving TFT in the data writing period; and sensing the amount of charge accumulated in the parasitic capacitor of the OLED during the boosting period in the sensing period.

Description

Driving method of organic light emitting display device {Driving Method Of Organic Light Emitting Display}

The present invention relates to an organic light emitting diode display, and more particularly, to a method of driving an organic light emitting diode (OLED) capable of compensating for deterioration of an organic light emitting diode (hereinafter, referred to as "OLED").

OLED, which is a self-luminous device, includes an anode electrode and a cathode electrode, and an organic compound layer (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 (Electron Injection layer, EIL). When a driving voltage is applied to the anode and cathode electrodes, holes passing through the hole transport layer (HTL) and electrons passing through the electron transport layer (ETL) are moved to the light emitting layer (EML) to form excitons, and as a result, the light emitting layer (EML) is produces visible light.

The organic light emitting display device arranges pixels including OLEDs in a matrix form and adjusts the luminance of the pixels according to the gray level of video data. Each of the pixels includes a driving TFT (Thin Film Transistor) that controls the driving current flowing through the OLED according to the voltage (Vgs) applied between its gate electrode and the source electrode. (Brightness) is adjusted.

In general, OLEDs have deterioration characteristics such that the operating point voltage (threshold voltage) of the OLED increases and the luminous efficiency decreases as the emission time elapses. Since the accumulated current applied to the OLED of each pixel is proportional to the accumulated grayscale implemented in the corresponding pixel, the degree of OLED degradation as described above may vary for each pixel. The OLED deterioration deviation between these pixels causes a luminance deviation, and if this is intensified, an image sticking phenomenon may occur.

In order to compensate for OLED deterioration, various compensation methods have been proposed in which OLED deterioration is sensed and video data is modulated in an external circuit based on the sensed value. However, in the known OLED degradation compensation method, since the deviation of the electric characteristics of the driving TFT was not taken into account, the OLED degradation could not be accurately sensed, and thus compensation performance was deteriorated.

Accordingly, it is an object of the present invention to provide a driving method of an organic light emitting display device capable of increasing the accuracy and compensation performance of OLED deterioration sensing by minimizing the influence of variations in the electrical characteristics of the driving TFT on the deterioration sensing of the OLED.

In order to achieve the above object, the present invention provides a driving method of an organic light emitting display device having a plurality of pixels including a driving TFT and an OLED connected to a source electrode of the driving TFT, respectively. and outputting a sensing scan signal at an on level, an off level, and an on level in each sensing period; supplying a gate electrode of the driving TFT, and supplying an off-level second sensing data voltage according to electrical characteristics of the driving TFT to the gate electrode of the driving TFT in the sensing period, and an initialization voltage in the data writing period supplying to the source electrode of the driving TFT, and sensing the amount of charge accumulated in the parasitic capacitor of the OLED during the boosting period in the sensing period, wherein the first sensing data voltage and the second sensing data The voltage difference between the voltages has the same characteristics in all pixels.

According to the present invention, by making the gate potential change amount of the driving TFT the same in all pixels when changing from the boosting period to the sensing period, the effect of the electric characteristic deviation of the driving TFT on the deterioration sensing of the OLED is minimized, thereby improving the accuracy of the OLED deterioration sensing value and Compensation performance can be increased.

1 is a view showing an organic light emitting display device according to an embodiment of the present invention.
2A and 2B are diagrams illustrating an example of a connection between a sensing line and a pixel;
3 is a diagram illustrating a configuration of a pixel array and a data driver IC for sensing OLED deterioration;
4 is a diagram illustrating a configuration of one pixel and a configuration of a sensing unit that senses OLED deterioration using a current sensing method.
5 is a view showing an OLED deterioration sensing timing according to an embodiment of the present invention.
6A to 6C are diagrams illustrating operating states of a pixel and a current integrator in a data writing period, a boosting period, and a sensing period of FIG. 5, respectively;
7 is a view showing an OLED deterioration sensing timing according to another embodiment of the present invention.
8 is a view showing a simulation result in which the OLED deterioration sensing deviation is eliminated by making the potential change amount of the gate node of the driving TFT the same in all pixels when changing from the boosting period to the sensing period according to the present invention;
9 is a graph showing the relationship between an OLED anode voltage and an OLED driving current is shifted according to OLED deterioration;
10 is a view showing an example of differently setting a sensing data voltage applied when sensing OLED deterioration according to a threshold voltage deviation of a driving TFT;
11 is a view showing the comparison of the OLED deterioration sensing results of the prior art and the present invention according to the threshold voltage change of the driving TFT.

Hereinafter, the technical idea of the present invention will be described in detail through examples.

1 shows an organic light emitting display device according to an embodiment of the present invention. 2A and 2B show examples of connection between a sensing line and a pixel. 3 shows a configuration of a pixel array and a data driver IC for sensing OLED degradation.

1 to 3 , an organic light emitting display device 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 , and a memory ( 16) is provided.

In the display panel 10 , a plurality of data lines and sensing lines 14A and 14B and a plurality of gate lines 15 cross each other, and pixels P are arranged in a matrix form in each crossed area.

The pixels P may include an R pixel for a red display, a W pixel for a white display, a G pixel for a green display, and a B pixel for a blue display, which are horizontally adjacent to each other as shown in FIGS. 2A and 2B . Each pixel P is connected to any one of the data lines 14A, to any one of the sensing lines 14B, and to any one of the gate lines 15 . Each pixel P is electrically connected to the data line 14A in response to a scan signal input through the gate line 15 , receives a data voltage from the data line 14A, and receives a data voltage through the sensing line 14B. Outputs a sensing signal.

The sensing line 14B may be independently connected to each horizontally adjacent pixel as shown in FIGS. 2A and 3 . In this sensing line independent structure, each of the horizontally adjacent R pixels, W pixels, G pixels, and B pixels may be connected to different sensing lines. Meanwhile, the sensing line 14B is commonly connected to at least two or more horizontally adjacent pixels as shown in FIG. 2B , thereby increasing the aperture ratio of the display panel. For example, horizontally adjacent R, W, G, and B pixels may share the same sensing line. In such a sensing line sharing structure, one sensing line may be allocated to each unit pixel (including R pixel, W pixel, G pixel, and B pixel).

Each of the pixels P receives a high potential driving voltage EVDD and a low potential driving voltage EVSS from a power generator (not shown). The pixel P of the present invention may include an OLED, a driving TFT, first and second switch TFTs, and a storage capacitor for external compensation. The TFTs constituting the pixel P may be implemented as p-type or n-type. In addition, the semiconductor layer of the TFTs constituting the pixel P may include amorphous silicon, polysilicon, or oxide.

Each of the pixels P may operate differently in a normal driving mode for displaying an input image and a sensing driving mode for sensing deterioration of the OLED.

Sensing driving is performed during a power-on sequence before normal driving starts, during vertical blank periods during normal driving, or in a power-off sequence after normal driving is terminated can be done in the process.

The normal driving 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 sensing driving may be performed by different operations of the data driving circuit 12 and the gate driving circuit 13 under the control of the timing controller 11 . The operation of deriving compensation data for compensating for the OLED deterioration deviation based on the OLED deterioration sensing result and the operation of modulating the digital video data RGB using the compensation data are performed by the timing controller 11 .

The data driving circuit 12 includes at least one data driver integrated circuit (IC) (SDIC). The data driver IC (SDIC) includes a plurality of digital-analog converters (hereinafter referred to as DACs) connected to each data line 14A, and a plurality of sensing units connected to the sensing lines 14B through sensing channels CH1 to CH6. Units (SU#1 to #6) are included.

The DAC of the data driver IC (SDIC) converts digital video data (RGB) into a data voltage for image realization according to the data timing control signal (DDC) applied from the timing controller 11 in the normal driving mode to form the data lines 14A ) is supplied to On the other hand, the DAC of the data driver IC (SDIC) has an on level first sensing data voltage and an off level according to the digital data for sensing and the data timing control signal DDC applied from the timing controller 11 in the sensing driving mode. A second sensing data voltage is generated and supplied to the data lines 14A.

The electric characteristic value of the driving TFT is reflected to each of the on-level first sensing data voltage and the off-level second sensing data voltage to increase accuracy in sensing OLED deterioration. The electrical characteristic value of the driving TFT may be obtained through the sensing of deterioration of the driving TFT, which is performed separately from the sensing of deterioration of the OLED of the present invention. Deterioration sensing of the driving TFT may be performed prior to sensing deterioration of the OLED of the present invention. The electrical characteristic value of the driving TFT includes a threshold voltage value of the driving TFT and an electron mobility value of the driving TFT.

In the sensing driving mode, each of the sensing units SU#1 to #6 of the data driver IC SDIC provides current information of the sensing target pixel P (the OLED parasitic capacitor of the sensing target pixel P in response to the driving current). The amount of charge accumulated in the Each of the sensing units SU#1 to #6 may be implemented including a current integrator. The data driver IC (SDIC) may further include an analog-to-digital converter (hereinafter, ADC) connected to output terminals of the sensing units SU#1 to #6. The data driver IC (SDIC) digitally processes the OLED deterioration sensing value and transmits it to the timing controller 11 .

The gate driving circuit 13 generates a scan signal for image display based on the gate control signal GDC in the normal driving mode, and then generates the gate lines in a row-sequential manner (L#1, L#2, ...). (15) is supplied sequentially. The gate driving circuit 13 generates a scan signal for sensing based on the gate control signal GDC in the sensing driving mode, and then connects the gate lines (L#1, L#2, ...) to the gate lines (L#1, L#2, ...) 15) sequentially. The sensing scan signal may have two on-pulse sections, unlike the image display scan signal. That is, the sensing scan signal may have an on-pulse period in each of the data writing period Twrt and the sensing period Tsen as shown in FIGS. 5 and 6 .

The timing controller 11 operates the data driving circuit 12 based on timing signals such as a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a dot clock signal DCLK, and a data enable signal DE. A data control signal DDC for controlling timing and a gate control signal GDC for controlling an operation timing of the gate driving circuit 13 are generated. The timing controller 11 distinguishes between a normal driving mode and a sensing driving mode based on a predetermined reference signal (a driving power enable signal, a vertical sync signal, a data enable signal, etc.), and a data control signal (DDC) according to each driving mode. ) and the gate control signal GDC. In addition, the timing controller 11 controls the related switching to operate the internal switches (RST, SAM, HOLD in FIG. 4 ) of each of the sensing units SU#1 to #6 according to the normal driving mode and the sensing driving mode. Signals CON may be further generated.

In the sensing driving mode, the timing controller 11 includes first sensing digital data for realizing an on-level first sensing data voltage and second sensing digital data for realizing an off-level second sensing data voltage. may be generated and transmitted to the data driving circuit 12 . In order to reflect the electrical characteristics of the driving TFT in each of the on-level first sensing data voltage and the off-level second sensing data voltage for sensing OLED deterioration, the timing controller 11 is configured to be performed separately from sensing deterioration of the OLED. The digital data for the first sensing and the digit for the second sensing may be corrected with reference to the electrical characteristic value of the driving TFT obtained in advance through the sensing of deterioration of the driving TFT.

Accordingly, the on-level first sensing data voltage for sensing OLED deterioration may be supplied to pixels having different electrical characteristics of the driving TFT at different values. Furthermore, the off-level second sensing data voltage for sensing OLED deterioration is also supplied as different values to pixels having different electrical characteristics of the driving TFT, so that the voltage difference between the first sensing data voltage and the second sensing data voltage may be the same in all pixels. In this way, it is possible to maximally suppress the distortion of the sensing value of OLED deterioration due to the deviation in the electrical characteristics of the driving TFT between pixels. This will be described later with reference to FIG. 6 .

The timing controller 11 detects the OLED deterioration of each pixel P based on the digital sensing value SD transmitted from the data driving circuit 12 in the sensing driving mode, and compensates for the deterioration deviation between the pixels P. Possible compensation data may be stored in the memory 16 .

The timing controller 11 modulates digital video data RGB for realizing an input image with reference to compensation data stored in the memory 16 in the normal driving mode, and then transmits the modulated digital video data RGB to the data driving circuit 12 .

The present invention adopts a current sensing method to sense OLED degradation in the sensing driving mode, thereby realizing low current and high speed sensing to reduce sensing time and increase sensing accuracy. As a part of this current sensing method, according to the present invention, at least one sensing unit is installed in the data driving circuit, and the amount of charge accumulated in the parasitic capacitor of the OLED of the sensing target pixel is sensed by the sensing unit.

4 shows a configuration of one pixel and a configuration of a sensing unit that senses OLED deterioration using a current sensing method.

Referring to FIG. 4 , each pixel P may include an OLED, a driving thin film transistor (DT), a storage capacitor Cst, a first switch TFT ST1, and a second switch TFT ST2. can

The OLED has an anode electrode connected to the source electrode of the driving TFT (DT) through the second node N2, a cathode electrode connected to the input terminal of the low potential driving voltage EVSS, and located between the anode electrode and the cathode electrode. an organic compound layer. A parasitic capacitor (Coled) is generated in the OLED by the anode electrode, the cathode electrode, and a plurality of insulating films present between them. The capacitance of the OLED parasitic capacitor Coled is several pF, which is very small compared to several hundred to several thousand pF, which is a parasitic capacitance existing in the sensing line 14B. The present invention uses an OLED parasitic capacitor (Coled) for current sensing.

The driving TFT DT controls the driving current input to the OLED according to the gate-source voltage Vgs. The driving TFT DT includes a gate electrode connected to the first node N1 , a drain electrode connected to the input terminal of the high potential driving voltage EVDD, and a source electrode connected to the second node N2 . The storage capacitor Cst is connected between the first node N1 and the second node N2 , that is, the driving TFT DT is connected between the gate electrode and the source electrode. The first switch TFT ST1 applies the data voltage Vdata on the data line 14A to the first node N1 in response to the scan signal SCAN. The first switch TFT ST1 includes 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 first node N1 . The second switch TFT ST2 switches a current flow between the second node N2 and the sensing line 14B in response to the scan signal SCAN. The second switch TFT ST2 includes 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 second node N2 .

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

The current integrator CI integrates the current information Ipixel flowing from the pixel to generate the sensing voltage Vsen. The current integrator CI is connected to the sensing line 14B through the sensing channel CH and accumulated in the current information Ipixel of the pixel from the sensing line 14B, that is, the OLED parasitic capacitor Coled of the pixel P The amplifier (AMP) including the inverting input terminal (-) that receives the charged charge, the non-inverting input terminal (+) that receives the initialization voltage (Vpre), and the output terminal, and the inverting input terminal (-) of the amplifier (AMP) and an integrating capacitor Cfb and a reset switch RST connected in parallel between the and the output terminal.

The current integrator (CI) is connected to the ADC through the sample & hold section (SH). The sample & hold unit SH samples the sensing voltage Vsen output from the amplifier AMP and stores the sampling switch SAM, which is stored in the sampling capacitor Cs, and the sensing voltage Vsen stored in the sampling capacitor Cs. It contains a holding switch (HOLD) to pass to the ADC.

The capacitance of the integrating capacitor Cfb is as small as a few hundredths compared to the parasitic capacitance existing in the sensing line 14B, so the current sensing method of the present invention requires a time required to draw in a current to a detectable level in general voltage sensing. significantly shorter than the method. In addition, unlike the parasitic capacitor of the sensing line 14B, the integration capacitor Cfb does not change a stored value according to a display load, so that an accurate sensed value can be obtained. As described above, according to the present invention, the sensing time can be greatly reduced by realizing low current and high speed sensing through the current sensing method using the current integrator (CI).

5 shows an OLED deterioration sensing timing according to an embodiment of the present invention. 6A to 6C show operating states of the pixel and the current integrator in the data writing period, boosting period, and sensing period of FIG. 5, respectively. And, FIG. 7 is a comparative example with respect to FIG. 5, in which an on-level first sensing data voltage is set according to the electrical characteristics of the driving TFT, but an off-level second sensing data voltage is correlated with the electrical characteristics of the driving TFT Shows the case where it is constant without FIG. 8 shows simulation results in which the OLED deterioration sensing deviation is eliminated by making the potential change amount of the gate node of the driving TFT the same in all pixels when changing from the boosting period to the sensing period according to the present invention.

Referring to FIG. 5 , the sensing processor for sensing OLED deterioration according to the present invention may include a data write period Twrt, a boosting period Tbst, and a sensing period Tsen that are continuously made. The sensing processor may further include a sampling period Tsam following the sensing period Tsen. The sensing processor will be described with reference to FIGS. 6A to 6C .

5 and 6A, the amplifier AMP operates as a unit gain buffer having a gain of 1 due to the turn-on of the reset switch RST in the data writing period Twrt, so that the input terminals of the amplifier AMP ( +, -), the output terminal, and the sensing line 14B are all initialized to the initialization voltage Vpre. In the data writing period Twrt, the on-level first sensing data voltage Vdata1 is applied to the data line 14A through the DAC of the data driver IC SDIC. The on-level first sensing data voltage Vdata1 is set within a high enough voltage range to turn on the driving TFT DT.

The first sensing data voltage Vdata1 on the data line 14A is applied to the first node N1 via the first switch TFT ST1 turned on according to the on-level sensing scan signal SCAN, and , the initialization voltage Vpre on the sensing line 14B is applied to the second node N2 via the second switch TFT ST2 turned on according to the on-level sensing scan signal SCAN. Accordingly, the source-drain current Ids corresponding to the potential difference {(Vdata1)-Vpre} between the first node N1 and the second node N2 flows through the driving TFT DT, that is, the OLED driving current. At this time, since the amplifier AMP continues to operate as a unit gain buffer, the initialization voltage Vpre is outputted from the output terminal of the amplifier AMP during the data writing period Twrt.

5 and 6B , in the boosting period Tbst, the first and second switch TFTs ST1 and ST2 are turned off according to the off-level sensing scan signal SCAN. Accordingly, the potential of the second node N2, that is, the anode voltage Vanode of the OLED, rises to the operating point voltage of the OLED by the source-drain current Ids of the driving TFT DT. The operating point voltage (Vanode) of the OLED increases in proportion to the degree of degradation of the OLED, and at this time, the amount of charge accumulated in the parasitic capacitor (Coled) of the OLED also increases in proportion to the degree of degradation (Q=Coled*Vanode). Meanwhile, since the amplifier AMP continues to operate as a unit gain buffer during the boosting period Tbst, the initialization voltage Vpre is output from the output terminal of the amplifier AMP even during the boosting period Tbst.

5 and 6C , in the sensing period Tsen, the first and second switch TFTs ST1 and ST2 are turned on according to the on-level sensing scan signal SCAN, and the reset switch RST is turned on. turns off The charge charged in the OLED parasitic capacitor Coled is stored in the integrating capacitor Cfb of the current integrator CI through the second switch TFT ST2, and an integration operation for sensing OLED deterioration is performed. At this time, the off-level second sensing data voltage Vdata2 is applied to the data line 14A through the DAC of the data driver IC SDIC, and the driving TFT DT is applied through the first switch TFT ST1. By turning off by the off-level second sensing data voltage Vdata2, the OLED deterioration sensing value is prevented from being distorted by the driving current flowing through the driving TFT DT. The off-level second sensing data voltage Vdata2 is set within a voltage range sufficiently low enough to turn off the driving TFT DT.

In the sensing period Tsen, the potential difference between both ends of the integrating capacitor Cfb by the charge flowing into the inverting input terminal (-) of the amplifier AMP increases as the sensing time elapses, that is, as the accumulated current Ipixel increases. However, due to the characteristics of the amplifier (AMP), the inverting input terminal (-) and the non-inverting input terminal (+) are shorted through the virtual ground and the potential difference between each other is 0, so in the sensing period (2), the inverting input terminal ( The potential of -) is maintained as the initialization voltage Vpre regardless of an increase in the potential difference of the integrating capacitor Cfb. Instead, the output terminal potential of the amplifier AMP is lowered in response to the potential difference between the both ends of the integrating capacitor Cfb. According to this principle, the electric charge flowing in through the sensing line 14B in the sensing period 2 is output as the sensing voltage Vsen which is an integral value through the integrating capacitor Cfb. In this case, the sensing voltage Vsen is the initialization voltage Vpre ) can be output as a lower value. This is due to the input/output characteristics of the current integrator (CI).

In the sampling period Tsam of FIG. 5 , the sensing voltage Vsen is stored in the sampling capacitor Cs via the sampling switch SAM. In the sampling period Tsam, when the holding switch HOLD is turned on, the sensing voltage Vsen stored in the sampling capacitor Cs is input to the ADC via the holding switch HOLD. The sensed voltage Vsen is converted into a digital sensed value SD by the ADC and then transmitted to the timing controller 11 . Then, the timing controller 11 applies the digital sensed value SD to the pre-stored compensation algorithm to derive compensation data for compensating for the OLED deterioration deviation along with the deviation. The compensation algorithm may be implemented as a lookup table or operation logic.

Meanwhile, a method of preventing the electric characteristic deviation of the driving TFT (DT) from affecting the OLED deterioration sensing value will be described in more detail. 5 and 7 , it is assumed that the first pixel PXL1 and the second pixel PXL2 have different electrical characteristic values of the TFT DT and the same OLED degradation values.

In the present invention, the on level applied during the data writing period Twrt to compensate for the current capability of the driving TFT DT so that the electric characteristic deviation of the driving TFT DT between pixels does not affect the OLED deterioration sensing value. An electrical characteristic value of the driving TFT DT is reflected in the first sensing data voltage Vdata1. As a result, the first sensing data voltage Vdata1 may be different by ΔV in the first pixel PXL1 and the second pixel PXL2 having different electrical characteristic values of the driving TFT DT. Accordingly, the amount of charge accumulated in the parasitic capacitor Coled of the OLED in the boosting period Tbst is not affected by the deviation of the electrical characteristics of the driving TFT DT. However, when changing from the boosting period Tbst to the sensing period Tsen, the amount of change in the gate potential of the driving TFT DT (that is, the amount of change in the potential VN1 of the first node) (ΔVN1) is not the same in all pixels. Otherwise, as shown in FIG. 7 , the source potential of the driving TFT DT coupled through the storage capacitor Cst (ie, the potential VN2 of the second node) is the amount of change in the gate potential of the driving TFT DT between pixels (ΔVN1) is affected by the difference, and accordingly, a deviation is induced in the OLED deterioration sensing value (Vsen). 7 shows that the on-level first sensing data voltage Vdata1 is set differently by ΔV in the first pixel PXL1 and the second pixel PXL2 in consideration of the electrical characteristics of the driving TFT DT, and at the same time , when the off-level second sensing data voltage Vdata2 is the same in the first pixel PXL1 and the second pixel PXL2 regardless of the electrical characteristics of the driving TFT DT, the OLED deterioration sensing value It shows that (Vsen) is distorted due to variations in the electrical characteristics of the driving TFT (DT).

Accordingly, the present invention corrects the first sensing digital data in consideration of the electrical characteristics of the driving TFT DT so that the on-level first sensing data voltage Vdata1 as shown in FIGS. 6 and 8 is converted into the first pixel PXL1. and the second pixel PXL2 are set differently by ΔV. In the present invention, the second sensing data voltage Vdata2 of the off-level is also the first pixel PXL1 and the second pixel PXL2 by correcting the digital data for the second sensing in consideration of the electrical characteristics of the driving TFT DT. is different from each other by ΔV, and the voltage difference ΔVdata between the first sensing data voltage Vdata1 and the second sensing data voltage Vdata2 is the same in all pixels. Through this, in the present invention, when changing from the boosting period Tbst to the sensing period Tsen, the amount of change in the gate potential of the driving TFT DT (that is, the amount of change in the potential VN1 of the first node) (ΔVN1) in all pixels By doing the same, distortion of the OLED deterioration sensing value Vsen due to a deviation in the electrical characteristics of the driving TFT DT can be suppressed as much as possible.

9 shows that a graph between an OLED operating point voltage and an OLED driving current is shifted according to OLED deterioration. Referring to FIG. 9 , it can be seen that the OLED operating point voltage Vanode corresponding to the same OLED driving current Ioled is increased after deterioration compared to before deterioration.

10 shows an example of differently setting the sensing data voltage applied when sensing OLED deterioration according to the threshold voltage deviation of the driving TFT. And, FIG. 11 compares and shows the OLED deterioration sensing results of the prior art and the present invention according to the change in the threshold voltage of the driving TFT.

Referring to FIG. 10 , a first pixel P1 having a threshold voltage variation ΔΦ of the driving TFT of −1V, a second pixel P2 of 0V, and a third pixel P1 of +1V are shown in the display panel 10 . In the present invention, the on-level first sensing data voltage Vdata1 is set differently for each pixel P1, P2, and P3 based on the threshold voltage change amount ΔΦ of the driving TFT, An off-level second sensing data voltage Vdata2 is set differently for each pixel P1 , P2 , and P3 based on the threshold voltage variation ΔΦ of the driving TFT. In particular, in the present invention, the voltage difference (ΔVdata, for example, 5.5V) between the first sensing data voltage Vdata1 and the second sensing data voltage Vdata1 is the same in all pixels P1, P2, and P3. By setting the data voltages so as to be possible, the amount of change in the gate potential of the driving TFT when changing from the boosting period to the sensing period is the same in all pixels P1, P2, and P3, so that the OLED deterioration sensing value is distorted by the threshold voltage deviation of the driving TFT. can be prevented from becoming

For example, in the present invention, a first sensing data voltage Vdata1 of 6V and a second sensing data voltage Vdata2 of 0.5V are applied to the first pixel P1, and 7V is applied to the second pixel P2. of the first sensing data voltage Vdata1 and the second sensing data voltage Vdata2 of 1.5V are applied, and the first sensing data voltage Vdata1 of 8V and the second sensing data voltage Vdata2 of 2.5V are applied to the third pixel P3. 2 By applying the sensing data voltage Vdata2, the influence of the threshold voltage deviation of the driving TFT on the OLED deterioration sensing value can be minimized.

If the gate potential change amount of the driving TFT is not the same in all pixels P1, P2, and P3 when changing from the boosting period to the sensing period as shown in FIG. The value Vsen is distorted. On the other hand, in the present invention, when changing from the boosting period to the sensing period, the amount of change in the gate potential of the driving TFT is the same in all pixels P1, P2, and P3, so that the electric characteristic deviation of the driving TFT as shown in (B) of FIG. 11 . It is possible to improve the accuracy of the OLED deterioration sensing value (Vsen) and to improve the compensation performance by minimizing the effect of ? on the deterioration sensing of the OLED.

Those skilled in the art from the above description will be able to see that various changes and modifications are possible without departing from the technical spirit of the present invention. Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

10: display panel 11: timing controller
12: data driving circuit 13: gate driving circuit
14A: data line 14B: sensing line
15: gate line SU: sensing unit

Claims (4)

In the driving method of an organic light emitting display device having a plurality of pixels each including a driving TFT and an OLED connected to a source electrode of the driving TFT,
outputting a scanning signal for sensing at an on level, an off level, and an on level in each of the consecutive data writing period, the boosting period, and the sensing period;
In the data writing period, an on-level first sensing data voltage according to the electrical characteristics of the driving TFT is supplied to the gate electrode of the driving TFT, and in the sensing period, an off-level second sensing data voltage according to the electrical characteristics of the driving TFT is supplied in the sensing period. supplying a sensing data voltage to a gate electrode of the driving TFT; and
supplying an initialization voltage to the source electrode of the driving TFT in the data writing period, and sensing the amount of charge accumulated in the parasitic capacitor of the OLED during the boosting period in the sensing period,
A voltage difference between the first sensing data voltage and the second sensing data voltage is the same in all pixels. The method of claim 1,
The first sensing data voltage is supplied to pixels having different electrical characteristics of the driving TFT at different values;
The second sensing data voltage is supplied as different values to pixels having different electrical characteristics of the driving TFT. The method of claim 1,
When changing from the boosting period to the sensing period, the amount of change in the gate potential of the driving TFT is the same in all pixels. The method of claim 1,
In the data writing period, the gate-source voltage of the driving TFT is initialized according to a preset driving current by the first sensing data voltage and the initialization voltage;
The operating point voltage of the OLED is stored in the parasitic capacitor of the OLED by the driving current applied to the OLED in the boosting period,
In the sensing period, the driving current is cut off by the second sensing data voltage, and the amount of charge accumulated in the parasitic capacitor of the OLED is sensed in a state in which the driving current is cut off.

Images