KR102203776B1 - Apparatus and method for sensing degradation of orgainc emitting diode device - Google Patents

Abstract

The present invention relates to an OLED element deterioration sensing device and method capable of sensing deterioration information of an OLED element without restriction on a pixel circuit. The deterioration sensing device is a deterioration sensing device after driving an OLED element using a driving TFT in one subpixel. , In a state in which the supply of the high-potential power is cut off by the switch, the voltage of at least the second and third nodes of the first to third nodes of the driving TFT is discharged through a current flowing from the driving TFT to the OLED element, and then, The current of the driving TFT varied according to the degradation information of the OLED element is charged in the capacitor of the reference line. The sensing unit of the data driver senses and outputs a voltage charged in the reference line.

Description

Device and method for sensing deterioration of an organic light emitting diode device {APPARATUS AND METHOD FOR SENSING DEGRADATION OF ORGAINC EMITTING DIODE DEVICE}

The present invention relates to an organic light emitting diode (OLED) display device, and in particular, to an OLED device degradation sensing device and method capable of sensing degradation information of an OLED device without restriction on a pixel circuit.

Recently, flat panel displays that display images using digital data include Liquid Crystal Display (LCD) using liquid crystal, OLED display using OLED, and Electrophoretic Display (EPD) using electrophoretic particles. ) Are representative.

Among them, the OLED display is a self-luminous device that emits light through the organic emission layer by recombination of electrons and holes, and is expected to be a next-generation display device due to its high luminance, low driving voltage, and ultra-thin film.

Each of the plurality of pixels or subpixels constituting the OLED display device includes an OLED element composed of an organic light emitting layer between an anode and a cathode, and a pixel circuit for independently driving the OLED element.

The pixel circuit includes a switching thin film transistor (TFT) that supplies a data voltage to charge the storage capacitor with a voltage corresponding to the data voltage, and controls the current according to the voltage charged in the storage capacitor to supply it to the OLED device. Including a driving TFT or the like, the OLED element generates light proportional to the current.

In the OLED display device, characteristics such as threshold voltage and mobility of the driving TFT for each pixel position are non-uniform due to process variations or the like, or a luminance non-uniform phenomenon occurs according to the deviation of deterioration of the driving TFT over the passage of driving time. To solve this problem, an external compensation method that detects and compensates for driving TFT characteristics is used.

In addition, the OLED display device has a problem in that a luminance non-uniformity occurs according to a deviation of deterioration of an OLED element over a lapse of driving time, and a lifespan is shortened due to a decrease in luminance. The deviation of deterioration of OLED elements is caused by varying the deterioration rate for each OLED element when driving for a long period of time, and if this becomes deeper, there is a problem in that image sticking occurs and the image quality deteriorates.

To solve this problem, the OLED display device uses an external compensation method that senses and compensates deterioration information of an OLED element, similar to a method of sensing and compensating the characteristics of a driving TFT.

However, in the conventional OLED device deterioration sensing method, when a plurality of subpixels constituting each pixel share a reference line, a first switching TFT for supplying a data signal to the gate node of the driving TFT in each subpixel and , Deterioration of the OLED element can be sensed only through the independent operation of the second switching TFT that supplies the current of the driving TFT reflecting the deterioration information of the OLED element to the reference line. For this reason, the conventional OLED device deterioration sensing method can be applied only to a two-scan structure in which the first and second switching TFTs of each pixel circuit are individually controlled, and a one-scan structure that simultaneously controls the first and second switching TFTs. There is a problem that cannot be applied to

The present invention was conceived to solve the above-described problems, and an object to be solved by the present invention is to provide an OLED device deterioration sensing device and method capable of sensing deterioration information of an OLED device without restriction on a pixel circuit. .

In order to solve the above problems, the method for sensing deterioration of an OLED device according to an embodiment of the present invention includes first to third steps.

The first step is to drive the OLED element using a driving TFT.

In the second step, a first node that is a control node in the driving TFT; Voltages of at least the second and third nodes among the second node connected to the OLED element and the third node to which the high potential power is supplied are discharged through the current flowing from the driving TFT to the OLED element when the high potential power is cut off. do.

In the third step, a voltage is sensed for a characteristic in which the current of the driving TFT varies according to the degradation information of the OLED element.

The first step includes an initialization step and a boosting step.

The initialization step is to supply a data voltage from a data line to a first node through a first switching TFT, a reference voltage to the second node through a second switching TFT, and supply a high potential power to a third node. , Charging the driving voltage of the driving TFT in the storage capacitor between the first and second nodes.

In the boosting step, the voltages of the first and second nodes are boosted according to the current flowing from the driving TFT to the OLED element while the first and second switching TFTs are turned off and high potential power is supplied to the third node.

The second step includes a discharging step, and the third step includes a sensing step.

In the discharging step, the first and second switching TFTs and a switch for supplying the high potential power to the high potential power line connected to the first node are turned off, according to the current flowing from the driving TFT to the OLED element. The first to third nodes discharge.

In the sensing step, at least a second switching TFT of the first and second switching TFTs is turned on, the first voltage between the third and second nodes reflecting the degradation information of the OLED element, and the second voltage between the first and second nodes. Charging the current of the driving TFT, which varies according to at least the first voltage among voltages, into the capacitor of the reference line through the second switching TFT, sensing the voltage charged in the capacitor of the reference line, and converting the sensing voltage to sensing data And outputting.

A method of sensing an OLED device according to another embodiment of the present invention includes a first initialization step, a discharge step, a second initialization step, and a sensing step.

The first initialization step is the same as the initialization step.

In the discharging stage, the second switching TFT and the switch supplying high potential power to the high potential power line connected to the first node are turned off, and the second node is discharged according to the current flowing from the driving TFT to the OLED element. do.

In the second initialization step, the second switching TFT and the switch are turned on, and the reference line and the second node are initialized to a second reference voltage different from the reference voltage in the first initialization step.

In the sensing step, the second switching TFT and the switch are turned on, and the current of the driving TFT, which varies according to the first voltage between the first and second nodes, in which the degradation information of the OLED element is reflected, is referenced through the second switching TFT. Charging the capacitor of the line, sensing a voltage charged in the capacitor of the reference line, converting the sensed voltage into sensing data, and outputting the sensing data.

An OLED device degradation sensing device according to an embodiment of the present invention includes a subpixel and a data driver.

The sub-pixel is a driving TFT for driving the OLED element, a first switching TFT for connecting the data line and the first node of the driving TFT, and a second switching for connecting the second node of the driving TFT connected to the OLED element with the reference line. It includes a TFT, a power supply line connected with a third node of the driving TFT, and a storage capacitor between the first and second nodes.

The data driver includes a data supply unit that supplies a data voltage to a data line, a reference supply unit that supplies a reference voltage to a reference line, a sensing unit that senses the voltage of the reference line, and a switch that supplies high potential power to the power line. do.

After driving the OLED element using the driving TFT, the subpixel is supplied with the voltage of at least the second and third nodes among the first to third nodes from the driving TFT in a state in which the supply of high potential power is cut off by the switch. After discharging through the current flowing through the OLED element, the current of the driving TFT varied according to the degradation information of the OLED element is charged into the capacitor of the reference line. The sensing unit of the data driver senses and outputs a voltage charged in the reference line.

The subpixels are driven in the order of an initialization step, a boosting step, a discharging step, and a sensing step, or the first initialization step, the discharging step, the second initialization step, and the sensing step described above.

The OLED device deterioration sensing device and method according to the present invention discharges all nodes of the driving TFT by cutting off the supply of high-potential power after driving the OLED device, or discharging at least one node while discharging the OLED to at least one node. The current of the driving TFT reflecting the deterioration information of the OLED element regardless of the one-scan or two-scan structure of the subpixel by allowing the deterioration information of the element to be reflected and the current of the driving TFT according to the deterioration information of the OLED element reflected in the node. By sensing the deterioration of the OLED device can be compensated.

In particular, in an OLED display to which a pixel circuit of a 1-scan structure is applied, the pixel aperture ratio can be increased compared to a pixel circuit of a 2-scan structure, so that the current density of the OLED element can be reduced, so that the deterioration rate of the OLED element can be reduced and the lifetime can be increased. .

In addition, in the OLED display to which the pixel circuit of the 2-scan structure is applied, the degree of deterioration of the OLED element is reflected in all nodes of the driving TFT, and the amount of change in the current of the driving TFT according to the deterioration information of the OLED element increases. The sensing rate can be improved.

1 is an equivalent circuit diagram showing a subpixel to which a method for sensing degradation of an OLED device according to the prior art is applied.
2 is an equivalent circuit diagram schematically showing a device for sensing degradation of an OLED device according to an embodiment of the present invention.
3 is a driving timing diagram of the device for sensing degradation of the OLED device shown in FIG. 2.
4 is a simulation waveform diagram of the deterioration sensing device of the OLED device shown in FIG. 2.
5A to 5D are diagrams showing stepwise a deterioration sensing process of the OLED device shown in FIG. 2.
6 is a graph showing the results of sensing degradation of an OLED device according to the present invention.
7 is a graph showing the tendency of deterioration of the OLED element sensed using the deterioration sensing device of the OLED element according to the present invention.
8 is a graph showing a change in a sensing value according to deterioration of an OLED element sensed using the OLED element deterioration sensing device according to the present invention.
9 is an equivalent circuit diagram schematically showing a device for sensing degradation of an OLED device according to another embodiment of the present invention.
10 to 12 are various simulation waveform diagrams for driving the deterioration sensing device of the OLED device shown in FIG. 9.
13 is a driving waveform diagram for explaining a deterioration sensing process of an OLED element according to another embodiment of the present invention using the deterioration sensing device of an OLED element shown in FIG. 9.
14A to 14D are diagrams showing stepwise a deterioration sensing process of an OLED device using the driving waveform shown in FIG. 13.
FIG. 15 is an equivalent circuit diagram illustrating an example of a configuration of one pixel using the 1-scan structure illustrated in FIG. 2.
16 is an equivalent circuit diagram illustrating an example of a configuration of one pixel using the two-scan structure shown in FIG. 9.

Before describing a preferred embodiment of the present invention, a method of sensing deterioration of an OLED device in a pixel circuit having a two-scan structure according to the prior art will be described.

1 is an equivalent circuit diagram showing a subpixel to which a method for sensing degradation of an OLED device according to the prior art is applied.

The subpixel SP shown in FIG. 1 includes an OLED element, first and second switching TFTs ST1 and ST2, a driving TFT DT, and a storage capacitor Cst to independently drive the OLED element. A pixel circuit of a two-scan structure is provided.

In the initialization step, the first switching TFT ST1 is turned on by the first scan signal SC of the first gate line GL1 to drive the data voltage Vdata from the data line DL. ), and the second switching TFT ST2 is turned on by the second scan signal SE of the second gate line GL2, and the reference voltage from the reference line RL ( Vref) is supplied to the source node S of the driving TFT DT, so that the storage capacitor Cst charges the difference voltage between the data voltage Vdata and the reference voltage Vref to the driving voltage Vgs.

In the boosting step, the first and second switching TFTs (ST1, ST2) are turned off, and the driving TFT supplies a current according to the driving voltage Vgs charged in the storage capacitor Cst to the OLED device to supply the OLED device. By driving, the voltage of the gate node (G) and the source node (S) of the driving TFT (DT) is boosted, and at this time, the voltage of the gate node (G) and the source node (S) of the driving TFT is boosted according to the degree of deterioration of the OLED device. The amount of increase in voltage varies.

In the writing step, only the first switching TFT (ST1) is turned on to supply the data voltage (Vdata) to the gate node (G) of the driving TFT (DT) again, and the driving TFT (DT) supplies the current to the OLED element. Thus, since the voltage of the source node S varies according to the degree of deterioration of the OLED element, the deterioration information of the OLED element is reflected in the voltage of the source node S.

In the sensing step, the first switching TFT (ST1) is turned off, the second switching TFT (ST2) is turned on, the gate node (G) of the driving TFT (DT) is floating, and the source node (S) is The reference voltage Vref from the reference line RL is supplied. At this time, the deterioration information of the OLED element reflected in the source node S is transferred to the gate node G due to the coupling effect of the storage capacitor Cst, and is transmitted to the driving TFT DT through the driving voltage Vgs of the driving TFT DT. ) Is reflected in the current. Accordingly, the current of the driving TFT (DT) reflecting the deterioration information of the OLED element is charged to the capacitance of the reference line RL through the second switching TFT (ST2) and sensed, and the deterioration information of the OLED element from the sensing voltage Can be extracted.

However, the OLED device deterioration sensing method according to the prior art can be applied only to a two-scan structure as shown in FIG. 1 because the first and second switching TFTs ST1 and ST2 must be individually controlled, and the first and second switching TFTs There is a problem that cannot be applied to a one-scan structure that simultaneously controls values.

In order to solve this, the present invention proposes an apparatus and method for sensing deterioration of an OLED device that can be applied both to a structure of a pixel circuit such as one scan or two scans.

2 is an equivalent circuit diagram schematically showing a device for sensing degradation of an OLED device according to an embodiment of the present invention.

The OLED device deterioration sensing device shown in FIG. 2 includes a subpixel SP having a 1-scan structure representing the display panel 10, a data driver 20 connected to the subpixel SP, and a data driver. A timing controller 30 connected to 20 is provided.

In the display panel 10, one sub-pixel SP is in series between a high-potential power line PH supplied with high-potential power EVDD and a low-potential power line PL supplied with low-potential power EVSS. The connected driving TFT (DT) and OLED element and the gate line (GL) are simultaneously controlled to drive the data line (DL) and the reference line (RL) to the gate node (G; first node) of the driving TFT (DT) and The driving voltage of the first and second switching TFTs ST1 and ST2 respectively connected to the source node S (second node), and the driving TFT DT connected between the gate node G and the source node S It includes a storage capacitor Cst that charges and supplies (Vgs).

The data driver 20 includes a first digital-to-analog converter (hereinafter referred to as DAC) 22, which is a data supply unit that converts input image data into a data voltage Vdata and supplies it to a data line DL, and input reference data to a reference voltage. The second DAC 24, which is a reference supply unit that converts into (Vref) and supplies it to the reference line RL, and receives the sensing voltage stored in the parasitic capacitor Cref of the reference line RL, converts it into sensing data, and outputs it. A reference voltage from an analog-to-digital converter (hereinafter referred to as ADC) 26 as a sensing unit, a first switch SW1 that supplies a high potential power supply (EVDD) to a high potential power line PH, and a second DAC 24 A second switch SW2 for supplying (Vref) to the reference line RL and a third switch SW3 for supplying the sensing voltage charged in the capacitor Cref of the reference line RL to the ADC 26. Include.

In each subpixel SP, the first and second switching TFTs ST1 and ST2 supply the data voltage Vdata and the reference voltage Vref to the storage capacitor Cst, and then turn off, and the storage capacitor Cst. When the driving TFT DT drives the OLED element according to the charged driving voltage Vgs, the source node S and the gate node G of the driving TFT DT are boosted. At this time, as the OLED element goes to the operating point (Vth), the amount of change in the voltage boosted by the voltage gate node (G) and the source node (S) varies depending on the degree of deterioration of the OLED element. G) and the source node (S) reflect the degradation information of the OLED device. This is because the current of the driving TFT (DT) changes according to the degree of deterioration of the OLED element.

Then, when the supply of high potential power (EVDD) is cut off, the voltage of the drain node D of the driving TFT DT is discharged and converges to the voltage of the source node S, so that the OLED element of the source node S is deteriorated. The information is also reflected in the drain node D (third node).

Subsequently, when the first and second switching TFTs ST1 and ST2 supply the data voltage Vdata and the reference voltage Vref to the gate node G and the source node S of the driving TFT DT again, the driving TFT The gate-source node voltage (Vgs) of is the same before/after deterioration of the OLED element, while the deterioration information of the OLED element reflected in the drain node (D) is the driving TFT (DT) by changing the drain-source voltage (Vds). ) Is reflected in the current.

Accordingly, the current of the driving TFT (DT) reflecting the degradation information of the OLED element is charged in the capacitor Cref of the reference line RL, and then the data driver 20 is applied to the capacitor Cref of the reference line RL. The charged voltage is sensed, and the sensed voltage is converted into sensing information through the ADC 26 and output. Accordingly, the timing controller 30 extracts the threshold voltage change value (?Vth) of the OLED element, which is the deterioration information of the OLED element by comparing the sensing information supplied from the data driver 20 with the initial sensing information before deterioration, and stores it in the memory. do. In addition, the timing controller 30 compensates for and outputs image data to be supplied to the data driver 20 by using the stored degradation information, thereby compensating for the degradation of the OLED device.

3 is a driving timing diagram of the deterioration sensing device of the OLED element shown in FIG. 2, FIG. 4 is a simulation waveform diagram, and FIGS. 5A to 5D are diagrams showing stepwise deterioration sensing processes of the OLED element.

3 to 5D, the deterioration sensing process of the OLED device includes an initialization step (FIG. 5A ), a boosting step (FIG. 5B ), a discharge step (FIG. 5C ), and a sensing step (FIG. 5D ).

In the initialization step shown in FIG. 5A, the first and second switching TFTs ST1 and ST2 are turned on by the gate-on voltage of the scan signal SC shown in FIGS. 3 and 4 to generate the data line DL. The data voltage Vdata and the reference voltage Vref of the reference line RL are supplied to the gate node G and the source node S of the driving TFT DT, respectively. Accordingly, the storage capacitor Cst charges the difference voltage between the data voltage Vdata and the reference voltage Vref with the driving voltage Vgs of the driving TFT DT. At this time, the first switch SW1 is turned on by the gate-on voltage of the control signal shown in FIGS. 3 and 4 to supply the high potential power EVDD to the high potential power line PH.

In the boosting step shown in FIG. 5B, the first and second switching TFTs ST1 and ST2 are turned off by the gate-off voltage of the scan signal SC shown in FIGS. 3 and 4, and the driving TFT DT ) Drives the OLED device by supplying a current according to the driving voltage Vgs charged in the storage capacitor Cst to the OLED device. Accordingly, the voltages of the gate node G and the source node S of the driving TFT DT are boosted while maintaining the gate-source driving voltage Vgs by coupling of the storage capacitor Cst. At this time, since the current flowing from the driving TFT (DT) to the OLED device varies depending on the degree of deterioration of the OLED device, the amount of change in voltage boosted at the gate node (G) and the source node (S) of the driving TFT (DT), that is, an increase amount. As it varies depending on the degree of deterioration of the OLED element, the deterioration information of the OLED element is reflected in the voltages of the gate node G and the source node S of the driving TFT DT. In this boosting step, the first switch SW1 is turned on by the gate-on voltage of the control signal shown in FIGS. 3 and 4 to supply the high potential power EVDD to the high potential power line PH.

In the discharging step shown in FIG. 5C, the first switch SW1 is turned off by the gate-off voltage of the control signal shown in FIGS. 3 and 4 to provide a high potential power supply (EVDD) to the high potential power line PH. Is cut off, and the first and second switching TFTs ST1 and ST2 maintain a turn-off state by the gate-off voltage of the scan signal SC. Accordingly, as shown in FIGS. 3 and 4, the gate node G and the source node S maintain the driving voltage Vgs between the gate and the source due to the coupling of the storage capacitor Cst. It is discharged according to the current, and the drain node D is also discharged, thereby converging to the voltage of the source node S. As a result, deterioration information of the OLED element of the source node S is reflected in the voltage of the drain node D.

In the sensing step shown in FIG. 5D, the first and second switching TFTs ST1 and ST2 are turned on by the gate-on voltage of the scan signal SC shown in FIGS. 3 and 4 to generate the data voltage Vdata. And the reference voltage Vref to the gate node G and the source node S of the driving TFT DT. Accordingly, the voltage of the gate node (G) of the driving TFT (DT) and the voltage of the source node (S) become the same as before the deterioration of the OLED element, and the deterioration information of the OLED element disappears, whereas the voltage of the drain node (D) is Deterioration information of the OLED element reflected in the voltage is reflected in the current of the driving TFT DT by changing the drain-source voltage Vds. The current of the driving TFT DT reflecting the degradation information of the OLED element is charged with a voltage in the capacitor Cref of the reference line RL through the second switching TFT ST2.

Accordingly, in the sensing step, the voltage of the reference line RL gradually increases as the voltage charged by the capacitor Cref of the reference line RL increases according to the current of the driving TFT DT as shown in FIGS. 3 and 4. . At this time, the magnitude of the voltage to be charged by the capacitor Cref, that is, the voltage slope and the voltage increase amount increasing on the reference line RL are changed according to the current of the driving TFT DT reflecting the degradation information of the OLED element. The data driver 20 senses and outputs the voltage charged in the capacitor Cref of the reference line RL at a desired point in the sensing step, thereby outputting sensing information reflecting the degradation information of the OLED device.

As described above, the OLED device deterioration sensing device according to the present invention can sense deterioration information of the OLED element even in a one-scan pixel circuit. Accordingly, in the OLED display to which the 1-scan structure pixel circuit is applied, the pixel aperture ratio is increased compared to the 2-scan structure pixel circuit, so that the current density of the OLED device can be reduced, so the deterioration rate of the OLED device can be reduced and the lifetime can be increased. have.

6 shows the result of sensing the degree of deterioration of the OLED element using the OLED element deterioration sensing device according to the present invention, and the sensing voltage Vsen is changed according to the change in the threshold voltage Vth due to the deterioration of the OLED element. You can see it's changing.

7 is a graph showing the tendency of degradation of the OLED element sensed using the OLED element deterioration sensing device according to the present invention. According to the current Ioled of the OLED element, the anode voltage of the OLED element (Vanode), that is, the driving TFT (DT ), it can be seen that the amount of change before/after the deterioration of the voltage of the source node increased.

FIG. 8 shows a sensing voltage Vsen according to a data voltage Vdata by using the deterioration sensing device of an OLED device according to the present invention. The sensing voltage Vsen varies depending on the data voltage Vdata, but the corresponding data voltage ( It can be seen that the sensing voltage Vsen for Vdata) changes according to the degree of deterioration of the OLED device.

9 is an equivalent circuit diagram schematically showing an OLED device degradation sensing device according to another embodiment of the present invention.

The OLED device deterioration sensing device illustrated in FIG. 9 is different from the one-scan structure illustrated in FIG. 2 in that the subpixel SP has a two-scan structure compared to the OLED device deterioration sensing device illustrated in FIG. 2. Therefore, the description will be made mainly on differences from the deterioration sensing device shown in FIG. 2, and descriptions of the same components will be omitted.

In the subpixel SP shown in FIG. 9, the first and second switching TFTs ST1 and ST2 are individually driven by different gate lines GL1 and GL2.

10 to 13, the width of the first scan pulse SC of the first gate line GL1 controlling the first switching TFT ST1 in the initialization step and the second switching TFT The widths of the second scan pulse SE of the second gate line GL2 controlling ST1 may be set differently.

For example, as shown in FIG. 10, the width of the second half of the second scan pulse SE is greater than the width of the first scan pulse SC in the initialization step, or the first scan pulse SC in the initialization step as shown in FIG. The width of the front half of the second scan pulse SE is larger than the width, or the width of the front and rear half of the second scan pulse SE is larger than the width of the first scan pulse SC in the initialization step as shown in FIG. The source node S of the driving TFT DT through the second switching TFT ST2 than the period in which the data voltage Vdata is supplied to the gate node G of the driving TFT DT through the 1 switching TFT ST1. The period during which the reference voltage Vref is supplied to the device may increase, but the storage capacitor Cst drives the difference voltage between the data voltage Vdata and the reference voltage Vref in this initialization step, similar to the one scan structure. It is charged with the driving voltage (Vgs) of DT).

In addition, driving in the remaining boosting step, discharging step, and sensing step in the subpixel SP having the two-scan structure may be the same as the sub-pixel SP having the one-scan structure described above.

In the sensing steps shown in FIGS. 10 to 12, the first and second switching TFTs ST1 and ST2 are simultaneously turned on by the first and second scan pulses SC and SE having the same pulse width, so that the driving TFT The drain-source voltage Vds changes according to the deterioration information of the OLED element reflected in the drain node D excluding the gate node G and the source node S of (DT), so that the first and second switching TFTs ( Even if ST1 and ST2 are turned on at the same time, the deterioration information of the OLED element can be reflected in the current of the driving TFT DT.

In contrast, in the sensing step shown in FIGS. 10 to 12, by supplying only the second scan pulse SE and not supplying the first scan pulse SC, the first switching TFT ST1 is turned off. , The second switching TFT (ST2) is turned on, the gate node (G) of the driving TFT (DT) is floating, and the source node (S) is supplied with a reference voltage (Vref) from the reference line (RL). I can. Accordingly, the voltage of the source node S is reduced to a lower reference voltage Vref than the voltage reduced by the discharge in the previous discharge step. At this time, the deterioration information of the OLED element reflected in the source node S is transferred to the gate node G due to the coupling effect of the storage capacitor Cst to change the driving voltage Vgs of the driving TFT DT and drain the drain. It is reflected in the node D and the source node S and reflected in the current of the driving TFT DT by changing the drain-source voltage Vds. That is, in the two-scan structure of the surf pixel (SP), deterioration information of the OLED element is reflected in all the nodes (G, S, D) of the driving TFT to change the current of the driving TFT DT. Accordingly, since the amount of current change according to the degree of deterioration of the OLED element increases and the sensing voltage increases, the sensing rate for deterioration information of the OLED element can be improved.

13 is a driving waveform diagram for explaining an OLED device degradation sensing process according to another embodiment of the present invention using the OLED device degradation sensing device illustrated in FIG. 9, and FIGS. 14A to 14D are driving shown in FIG. These are diagrams showing step by step an OLED device degradation sensing process using waveforms.

13 to 14D, the deterioration sensing process of the OLED device includes a first initialization step (FIG. 14A ), a discharge step (FIG. 14B ), a second initialization step (FIG. 14C ), and a sensing step (FIG. 14D ). .

In the first initialization step shown in FIG. 14A, the first and second switching TFTs ST1 and ST2 are turned on by the gate-on voltages of the first and second scan signals SC and SE shown in FIG. 13. As a result, the storage capacitor Cst charges the difference voltage between the data voltage Vdata and the first reference voltage Vref1 with the driving voltage Vgs of the driving TFT DT. At this time, the first switch SW1 is turned on by the gate-on voltage of the first control signal shown in FIG. 13 to supply the high potential power EVDD to the high potential power line PH, and the second switch ( SW2 is turned on by the gate-on voltage of the second control signal to supply the first reference voltage Vref1 to the reference line RL.

In the discharging step shown in FIG. 14B, the first switching TFT ST1 maintains a turn-on state by the gate-on voltage of the first scan signal SC shown in FIG. 13, and the second scan signal SE The second switching TFT ST2 is turned off by the gate-off voltage of, and the first and second switches SW1 and SW2 are also turned off by the gate-off voltage of the corresponding control signal.

The driving TFT DT drives the OLED device by supplying a current according to the driving voltage Vgs charged in the storage capacitor Cst to the OLED device. Accordingly, the gate node (G) of the driving TFT (DT) maintains the data voltage (Vdata) supplied through the first switching TFT (ST1), while the floating drain node (D) and the source node (S) The voltage is discharged along the current flowing from the driving TFT DT to the OLED element, and the source node S decreases to the threshold voltage Vth of the OLED element. Therefore, the voltage of the source node S is also changed according to the variation of the threshold voltage Vth, which is the degradation information of the OLED device, so that the degradation information of the OLED device is reflected in the source node S. As a result, the driving TFT DT It is also reflected in the gate-source voltage (Vgs = Vdata-OLED_Vth), and the gate-source voltage Vgs of the driving TFT DT varies according to the degradation information of the OLED element.

In the second initialization step shown in FIG. 14C, the first switching TFT ST1 is turned off by the gate-off voltage of the first scan signal SC shown in FIG. 13, and the second scan signal SE is The second switching TFT ST2 is turned on by the gate-on voltage, and the first and second switches SW1 and SW2 are also turned on by the gate-on voltage of the corresponding control signal.

At this time, a second reference voltage Vref2 <Vref1 different from the first reference voltage Vref1 is supplied to the reference line RL in the first initialization step, and the driving TFT DT is applied through the second switching TFT ST2. The voltage of the source node S decreases to the second reference voltage Vref2 and is second initialized. At this time, the voltage of the floating gate node G decreases while maintaining the gate-source voltage Vgs together with the source node S according to the coupling of the storage capacitor Cst. At this time, the deterioration information of the OLED element reflected in the source node S is transferred to the gate node G, so that the deterioration information of the OLED element is reflected in the gate-source voltage Vgs. At this time, the first switch SW1 is turned on to hold the voltage of the drain node D of the driving TFT DT as the high potential power supply EVDD.

In the sensing step shown in FIG. 14D, the first switching TFT ST1 maintains a turn-off state by the gate-off voltage of the first scan signal SC shown in FIG. 13, and the second scan signal SE The second switching TFT ST2 maintains a turn-on state by the gate-on voltage of, and the first switch SW1 maintains a turn-on state by the gate-on voltage of the first control signal, and the second switch (SW2) is turned off by the gate-off voltage of the second control signal.

The voltage (Vgs) between the gate and source changes according to the deterioration information of the OLED element reflected in the gate node (G) and the source node (S) of the driving TFT (DT). Is reflected. The current of the driving TFT DT reflecting the degradation information of the OLED element is charged in the capacitor Cref of the reference line RL through the second switching TFT ST2.

Accordingly, in the sensing step, the voltage of the reference line RL gradually increases as the voltage charged by the capacitor Cref of the reference line RL increases according to the current of the driving TFT DT, as shown in FIG. 13. At this time, the magnitude of the voltage to be charged by the capacitor Cref, that is, the voltage slope and the voltage increase amount increasing on the reference line RL are changed according to the current of the driving TFT DT reflecting the degradation information of the OLED element. The third switch (SW3) is turned on at a desired point in the sensing step, senses the voltage charged in the capacitor (Cref) of the reference line (RL) and outputs it to the ADC, so that the ADC provides sensing information reflecting the degradation information of the OLED device. Can be output to the timing controller.

As described above, the OLED device deterioration sensing device and method according to the present invention can be applied to a pixel circuit of a two-scan structure to compensate for deterioration of the OLED element by sensing the current of the driving TFT reflecting the deterioration information of the OLED element.

FIG. 15 is an equivalent circuit diagram showing an example of a configuration of one pixel using a one-scan structure shown in FIG. 2, and FIG. 16 is an equivalent circuit diagram showing an example of a configuration of one pixel using a two-scan structure illustrated in FIG. 9 to be.

One pixel shown in FIGS. 15 and 16 includes R/W/B/G subpixels. The R/W/B/G subpixels are connected to the data lines DL1 to DL4, respectively, and share one gate line GL as shown in FIG. 15, or a pair of gate lines GL1 and GL1 as shown in FIG. GL2) and one reference line RL. In contrast, the R/W/B/G subpixels are not shown, but may be connected to different reference lines, respectively. A pair of data lines DL1 and DL2 are arranged side by side between the R/W subpixels, and the other pair of data lines DL3 and DL4 are arranged side by side between the B/G subpixels.

One high potential power line PH1 disposed on the left side of the R subpixel is commonly connected to the R/W subpixels, and the other high potential power line PH2 disposed on the right side of the G subpixel is a B/G subpixel. It is commonly connected to and supplies a high potential voltage (EVDD). The first switch SW1 shown in FIGS. 2 and 9 is individually connected to the high potential power lines PH1 and PH2.

Each of the R/W/B/G subpixels includes an OLED device, first and second switching TFTs (ST1, ST2), a driving TFT (DT), and a storage capacitor (Cst) to independently drive the OLED device. And a pixel circuit to perform.

Since the second switching TFT (ST2) of each of the R/W/B/G subpixels shares one reference line (RL), deterioration information on the OLED element of each of the R/W/B/G subpixels May be sensed through the shared reference line RL at different times. For example, when sensing the characteristic of any one of the R/W/B/G subpixels, the subpixel is driven by supplying a sufficient sensing data voltage so that the OLED element can be turned on. , The black data voltage is supplied to the remaining subpixels that are not sensed, or the low potential voltage EVSS is applied high to turn it off.

As described above, in the OLED element deterioration sensing device and method according to the present invention, the OLED element deterioration information is transmitted to at least one node while discharging all the nodes of the driving TFT by cutting off the supply of high-potential power after driving the OLED element. OLED device by sensing the current of the driving TFT reflecting the degradation information of the OLED device, regardless of the 1-scan or 2-scan structure of the subpixel by changing the current of the driving TFT according to the degradation information of the OLED device reflected in the node. Can compensate for the deterioration of

In particular, in an OLED display to which a pixel circuit of a 1-scan structure is applied, the pixel aperture ratio is increased compared to a pixel circuit of a 2-scan structure, so that the current density of the OLED device can be reduced, so that the deterioration rate of the OLED device can be reduced, thereby increasing the lifetime. .

In addition, in the OLED display to which the pixel circuit of the 2-scan structure is applied, the degree of deterioration of the OLED element is reflected in all nodes of the driving TFT, and the amount of change in the current of the driving TFT according to the deterioration information of the OLED element increases. The sensing rate can be improved.

Although shown and described as specific embodiments to illustrate the technical idea of the present invention, the present invention is not limited to the same configuration and operation as the specific embodiment as described above, and various modifications do not depart from the technical idea of the present invention. It can be implemented within a range. Therefore, such modifications should be regarded as belonging to the scope of the present invention, and the scope of the present invention should be determined by the claims to be described later.

10: display panel 20: data driver
30: timing controller 22, 24: DAC
26: ADC

Claims (8)

A first step of driving an organic light emitting diode (hereinafter, OLED) device using a driving thin film transistor (hereinafter, referred to as TFT), and
Voltages of at least the second and third nodes among a first node that is a control node in the driving TFT, a second node connected to the OLED element, and a third node to which a high potential power is supplied, the high potential power supply is A second step of discharging through a current flowing from the driving TFT to the OLED element in a blocked state; and
And a third step of sensing a characteristic in which the current of the driving TFT varies as a voltage according to the degradation information of the OLED device. The method according to claim 1,
The first step
A data voltage from a data line is supplied to the first node through a first switching TFT, a reference voltage is supplied to the second node through a second switching TFT, and the high potential power is supplied to the third node. , An initialization step of charging a driving voltage of the driving TFT in a storage capacitor between the first and second nodes,
When the first and second switching TFTs are turned off and the high potential power is supplied to the third node, the voltages of the first and second nodes are boosted according to the current flowing from the driving TFT to the OLED element. OLED device degradation sensing method comprising the step of. The method according to claim 2,
The second step
In a state in which a switch for supplying the high potential power to the first and second switching TFTs and the high potential power line connected to the first node is turned off, according to the current flowing from the driving TFT to the OLED element Including the step of discharging the first to third nodes,
The third step
At least the second switching TFT of the first and second switching TFTs is turned on, the first voltage between the third and second nodes reflecting the degradation information of the OLED element, and between the first and second nodes Charging a current of the driving TFT, which varies according to at least a first voltage among second voltages, into a capacitor of the reference line through the second switching TFT;
Sensing the voltage charged in the capacitor of the reference line, converting the sensing voltage into sensing data, and outputting the sensing data. The method according to claim 1,
In the first step, a data voltage from a data line is supplied to the first node through a first switching TFT, a reference voltage is supplied to the second node through a second switching TFT, and the high potential power is supplied to the first node. An initialization step of charging a driving voltage of the driving TFT in a storage capacitor between the first and second nodes by supplying it to three nodes,
The second step is a current flowing from the driving TFT to the OLED element in a state in which a switch for supplying the high potential power to the second switching TFT and the high potential power line connected to the first node is turned off. And discharging by the second node according to,
The third step
The second switching TFT and the switch are turned on, and the current of the driving TFT, which is varied according to the first voltage between the first and second nodes, in which the degradation information of the OLED element is reflected, is transmitted through the second switching TFT. Charging the capacitor of the reference line, and
Sensing a voltage charged in the capacitor of the reference line, converting the sensing voltage into sensing data, and outputting the converted voltage,
Between the second and third steps, the second switching TFT and the switch are turned on, and the step of initializing the reference line and the second node to a second reference voltage different from the reference voltage of the initialization step is added. Deterioration sensing method of an OLED device including as A driving TFT for driving an OLED element, a first switching TFT for connecting a data line and a first node of the driving TFT, and a second switching for connecting a second node of the driving TFT connected to the OLED element with a reference line A subpixel including a TFT, a power line connected to a third node of the driving TFT, and a storage capacitor between the first and second nodes,
A data supply unit for supplying a data voltage to the data line, a reference supply unit for supplying a reference voltage to the reference line, a sensing unit for sensing the voltage of the reference line, and a switch for supplying high potential power to the power line. Contains a data driver containing,
After driving the OLED element using the driving TFT, the subpixel is at least the second and third nodes among the first to third nodes in a state in which the supply of the high potential power is cut off by the switch. After discharging the voltage of the driving TFT through the current flowing from the driving TFT to the OLED element, the current of the driving TFT, which has been varied according to the deterioration information of the OLED element, is charged into the capacitor of the reference line to sense the data driver. An OLED device degradation sensing device that additionally senses and outputs a voltage charged in the reference line. The method of claim 5,
The subpixel is
In the initialization step, the data voltage is supplied to the first node through the first switching TFT, the reference voltage is supplied to the second node through the second switching TFT, and the high potential power is supplied to the third node. Supplying to, charging the driving voltage of the driving TFT in the storage capacitor between the first and second nodes,
In the boosting step, the first and second nodes according to the current flowing from the driving TFT to the OLED element while the first and second switching TFTs are turned off and the high potential power is supplied to the third node. The voltage of is boosted,
In the discharging step, in a state in which the first and second switching TFTs and the switch are turned off, the first to third nodes are discharged according to a current flowing from the driving TFT to the OLED element,
In the sensing step, at least the second switching TFT of the first and second switching TFTs is turned on, and a first voltage between the third and second nodes reflecting deterioration information of the OLED element, and the first and An OLED device degradation sensing device for charging a current of the driving TFT, which is varied according to at least a first voltage among second voltages between second nodes, into a capacitor of the reference line through the second switching TFT. The method of claim 6,
The first and second switching TFTs are connected to one gate line or are connected to two gate lines, respectively. The method of claim 5,
The subpixel is
In a first initialization step, the data voltage is supplied to the first node through the first switching TFT, the reference voltage is supplied to the second node through a second switching TFT, and the high potential power is supplied to the first node. 3 supplying the node to charge the driving voltage of the driving TFT in the storage capacitor between the first and second nodes,
In the discharging step, in a state in which the second switching TFT and the switch are turned off, the second node discharges according to a current flowing from the driving TFT to the OLED element,
In the second initialization step, the second switching TFT and the switch are turned on, and the reference line and the second node are initialized to a second reference voltage different from the reference voltage in the first initialization step,
In the sensing step, the second switching TFT and the switch are turned on, and the second switching of the current of the driving TFT that is varied according to the first voltage between the first and second nodes reflecting the degradation information of the OLED element An OLED device degradation sensing device that charges a capacitor of the reference line through a TFT.

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