KR20160094130A - Apparatus and method for sensing degradation of orgainc emitting diode device - Google Patents

Abstract

The present invention relates to an apparatus and a method for sensing degradation information of an OLED device without restrictions on a pixel circuit. The degradation sensing apparatus according to the present invention operates an OLED device by using an operation TFT in a sub-pixel, and then discharges at least voltage of a second node and a third node among a first to third nodes of the operation TFT via current flowing from the operation TFT to the OLED device in a state in which supplying high-potential power source is blocked by a switch, and then fills a capacitor of a reference line with operation TFT current changed according to degradation information of the OLED device. A sensing unit of a data driver senses and outputs voltage filled in the reference line.

Description

TECHNICAL FIELD [0001] The present invention relates to an apparatus and a method for sensing deterioration of an organic light emitting diode (OLED)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode (OLED) display device, and more particularly, to an OLED device deterioration sensing device and method capable of sensing deterioration information of an OLED device without restriction on a pixel circuit.

2. Description of the Related Art Recently, flat panel display devices that display images using digital data include liquid crystal displays (LCDs) using liquid crystals, OLED display devices using OLEDs, electrophoretic displays (EPDs) using electrophoretic particles ).

Of these, OLED display devices are self-luminous devices that emit organic light-emitting layers by recombination of electrons and holes, and are expected to be a next-generation display device because of their high luminance, low driving voltage, and ultra thin films.

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 the anode and the cathode, and a pixel circuit independently driving the OLED element.

The pixel circuit includes a switching thin film transistor (TFT) for supplying a data voltage to the storage capacitor to charge a voltage corresponding to the data voltage, and a control circuit for controlling the current according to the voltage charged in the storage capacitor to supply the OLED element A driving TFT, and the like, and the OLED element generates light proportional to the current.

In OLED display devices, characteristics such as threshold voltage and mobility of driving TFTs are not uniform for each pixel position due to process variations or the like, or a luminance non-uniformity phenomenon occurs according to driving TFT deterioration deviation with elapsed driving time. To solve this problem, an external compensation method for detecting and compensating the characteristics of the driving TFT is used.

In addition, the OLED display device has a problem in that luminance unevenness occurs according to the deterioration of the OLED element as the driving time elapses, the luminance decreases, and the service life is shortened. The deterioration of the OLED element is caused when the degradation rate is different for each OLED element when driven for a long time. When the degradation rate is increased, an image sticking phenomenon occurs and the image quality is deteriorated.

To solve this problem, an OLED display device uses an external compensation method for sensing and compensating for degradation information of an OLED element, similar to a method of sensing and compensating for driving TFT characteristics.

However, in the conventional method of sensing degradation of an OLED element, 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 for supplying the current of the driving TFT reflecting the deterioration information of the OLED element to the reference line. Therefore, the conventional deterioration sensing method of the OLED element can be applied only to the two-scan structure in which the first and second switching TFTs of each pixel circuit are individually controlled, and the one-scan structure for simultaneously controlling the first and second switching TFTs There is a problem that it can not be applied to.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide an apparatus and method for deterioration of an OLED element capable of sensing deterioration information of an OLED element without restriction on a pixel circuit .

According to an aspect of the present invention, there is provided a method of sensing deterioration of an OLED element, including the steps of:

The first step drives the OLED element using the driving TFT.

A second node which is a control node in the driving TFT in a second step; A second node connected to the OLED element and a second node connected to the first node and a third node to which the high potential power is supplied are driven by a current flowing from the driving TFT to the OLED element in a state in which the high- do.

In the third step, the characteristic of varying the current of the driving TFT according to the deterioration information of the OLED element is sensed by the voltage.

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

The initializing step supplies the data voltage from the data line to the first node through the first switching TFT, supplies the reference voltage to the second node through the second switching TFT, supplies the reference voltage to the third node , And charges the driving voltage of the driving TFT to 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 in a state where the first and second switching TFTs are turned off and the 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 are turned on in response to the current flowing from the driving TFT to the OLED element in a state in which the switch for supplying the high potential power supply to the high potential power supply line connected to the first node is turned off The first to third nodes are discharged.

In the sensing step, at least a second switching TFT among the first and second switching TFTs is turned on, and a first voltage between a third node and a second node in which deterioration information of the OLED element is reflected, and a second voltage between the first node and the second node A step of charging a capacitor of a reference line through a second switching TFT with a current of a driving TFT which varies according to at least a first voltage of the voltage, sensing a voltage charged in a capacitor of the reference line, converting the sensing voltage into sensing data And outputting.

A sensing method of an OLED element 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 step, in a state in which the second switching TFT and the switch for supplying the high potential power to the high potential power supply line connected to the first node are turned off, the second node is turned off 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 of the first initialization step.

The sensing step is performed such that the second switching TFT and the switch are turned on and the current of the driving TFT which varies in accordance with the first voltage between the first and second nodes, in which deterioration information of the OLED element is reflected, Charging a capacitor of the line, sensing the voltage charged in the capacitor of the reference line, and converting the sensing voltage into sensing data and outputting the sensing data.

An apparatus for sensing deterioration of an OLED element according to an exemplary embodiment of the present invention includes a subpixel and a data driver.

The sub-pixel includes 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 circuit for connecting the second node of the driving TFT connected to the OLED element to the reference line. A TFT, a power supply line connected to 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 the data line, a reference supply unit that supplies a reference voltage to the reference line, a sensing unit that senses the voltage of the reference line, and a switch that supplies high- do.

The subpixel drives the OLED elements using the driving TFTs and then supplies the voltages of at least the second and third nodes of the first to third nodes to the driving TFTs Discharges through the current flowing to the OLED element, and then charges the capacitor of the reference line with the current of the driving TFT which is varied in accordance with the deterioration information of the OLED element. The sensing portion of the data driver senses and outputs the voltage charged in the reference line.

The subpixel is driven in the order of the initialization step, the boosting step, the discharging step, and the sensing step described above, or in the order of the first initialization step, the discharge step, the second initialization step, and the sensing step described above.

An apparatus and method for sensing degradation of an OLED element according to the present invention includes driving an OLED element and then shutting off supply of a high potential power to discharge all nodes of the driving TFT or discharging at least one node, The deterioration information of the element is reflected and the current of the driving TFT is changed according to the deterioration information of the OLED element reflected at the node so that the current of the driving TFT in which deterioration information of the OLED element is reflected regardless of the one- So that deterioration of the OLED element can be compensated.

Particularly, in an OLED display device to which a pixel circuit of one scan structure is applied, since the pixel aperture ratio increases more than the pixel circuit of 2 scan structure, the current density of the OLED device can be reduced, and the degradation speed of the OLED device can be reduced, .

Further, in the OLED display device to which the pixel circuit of the two 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 current change of the driving TFT is increased according to the deterioration information of the OLED element, The sensing rate can be improved.

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

Before explaining the preferred embodiments of the present invention, a method of sensing deterioration of an OLED element in a pixel circuit having a two scan structure according to the prior art will be described first.

1 is an equivalent circuit diagram showing a subpixel to which a method of sensing deterioration of an OLED element 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 for independently driving an OLED element 2 scan structure.

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 turn on the data voltage Vdata from the data line DL to the drive TFT DT And the second switching TFT ST2 is turned on by the second scan signal SE of the second gate line GL2 so as to supply the reference voltage Vref to the gate node G of 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 with the driving voltage Vgs.

In the boosting step, the first and second switching TFTs ST1 and ST2 are turned off, and the driving TFT supplies a current corresponding to the driving voltage Vgs charged in the storage capacitor Cst to the OLED element, The voltages of the gate node G and the source node S of the driving TFT DT are boosted and boosted at the gate node G and source node S of the driving TFT according to the degree of deterioration of the OLED element The increase amount of the voltage is changed.

Only the first switching TFT ST1 is turned on to supply the data voltage Vdata again to the gate node G of the driving TFT DT and the driving TFT DT supplies the current to the OLED element So that the voltage of the source node S varies depending on the degree of deterioration of the OLED element, so that 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 so that the gate node G of the driving TFT DT is floated, and the source node S And the reference voltage Vref is supplied from the reference line RL. At this time, deterioration information of the OLED element reflected on the source node S is transferred to the gate node G due to the coupling effect of the storage capacitor Cst and is supplied to the driving TFT DT through the driving voltage Vgs of the driving TFT DT. Lt; / RTI > Accordingly, the current of the drive TFT DT reflecting the deterioration information of the OLED element is charged and sensed by the voltage of the reference line RL through the second switching TFT ST2, and the deterioration information of the OLED element Can be extracted.

However, the degradation sensing method of the OLED element according to the prior art can be applied only to the two-scan structure as shown in FIG. 1 since the first and second switching TFTs ST1 and ST2 must be individually controlled, and the first and second switching TFTs The present invention can not be applied to a one-scan structure in which a scan signal is simultaneously controlled.

In order to solve this problem, the present invention proposes an apparatus and method for degrading an OLED element which can be applied to a structure of a pixel circuit such as one scan or two scans.

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

The degradation sensing apparatus of the OLED element shown in FIG. 2 includes a sub-pixel SP having a one-scan structure representative of the display panel 10, a data driver 20 connected to the sub-pixel SP, And a timing controller 30 connected to the timing controller 20.

One subpixel SP in the display panel 10 is connected in series between the high potential power supply line PH to which the high potential power supply EVDD is supplied and the low potential power supply line PL to which the low potential power supply EVSS is supplied The driving TFT DT and the OLED element which are connected and the data line DL and the reference line RL which are simultaneously controlled by the gate line GL are connected to the gate node G And a source node S connected to the source and drain electrodes of the driving TFT DT and the source and drain electrodes of the driving TFT DT, And a storage capacitor Cst for charging and supplying a voltage Vgs.

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

The first and second switching TFTs ST1 and ST2 in each subpixel SP are turned off after supplying the data voltage Vdata and the reference voltage Vref to the storage capacitor Cst and are turned off to the storage capacitor Cst When the driving TFT DT drives the OLED element in accordance with the charged driving voltage Vgs, the source node S and the gate node G of the driving TFT DT are boosted. At this time, the variation amount of the voltage boosted at the voltage gate node G and the source node S is changed according to the degree of deterioration of the OLED element while the OLED element is searching for the operating point Vth, G and the source node S reflect deterioration information of the OLED element. This is because the current of the driving TFT DT changes depending on the degree of deterioration of the OLED element.

Then, when the supply of the high potential power source EVDD is cut off, the voltage of the drain node D of the driving TFT DT is discharged and converged to the voltage of the source node S, so that the deterioration of the OLED element of the source node S Information is also reflected to 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 deterioration information of the OLED element reflected in the drain node D is changed by changing the drain-source voltage Vds so that the driving TFT DT Lt; / RTI >

The current of the drive TFT DT reflecting the deterioration information of the OLED element is charged in the capacitor Cref of the reference line RL and then the data driver 20 applies the current to the capacitor Cref of the reference line RL Senses the charged voltage, and converts the sensing voltage into sensing information through the ADC 26 and outputs it. Therefore, the timing controller 30 extracts the threshold voltage change value (? Vth) of the OLED element, which is deterioration information of the OLED element, by comparing the sensing information supplied from the data driver 20 with the initial sensing information before deterioration, do. The timing controller 30 compensates for the deterioration of the OLED element by compensating for the image data to be supplied to the data driver 20 using the stored deterioration information.

FIG. 3 is a driving timing diagram of the degradation sensing device of the OLED element shown in FIG. 2, FIG. 4 is a simulation waveform diagram, and FIGS. 5a to 5d are views showing the degradation sensing process of the OLED element in stages.

Referring to FIGS. 3 to 5D, the degradation sensing process of the OLED element includes an initialization step (FIG. 5A), a boosting step (FIG. 5B), a discharging step (FIG. 5C), and a sensing step (FIG.

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 FIG. 3 and FIG. 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. Thus, the storage capacitor Cst charges the difference voltage between the data voltage Vdata and the reference voltage Vref with the drive voltage Vgs of the drive 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 supply EVDD to the high potential power supply 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, Supplies a current according to the driving voltage Vgs charged in the storage capacitor Cst to the OLED element to drive the OLED element. 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 the coupling of the storage capacitor Cst. At this time, the current flowing from the driving TFT DT to the OLED element changes according to the degree of deterioration of the OLED element. Therefore, the amount of change in the voltage boosted at the gate node G and the source node S of the driving TFT DT, The deterioration information of the OLED element is reflected to 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 supply EVDD to the high potential power supply line PH.

5C, the first switch SW1 is turned off by the gate-off voltage of the control signal shown in FIG. 3 and FIG. 4 to turn on the high potential power supply EVDD to the high potential power supply line PH, And the first and second switching TFTs ST1 and ST2 maintain the turn-off state by the gate-off voltage of the scan signal SC. 3 and 4, the gate node G and the source node S maintain the gate-source drive voltage Vgs by coupling of the storage capacitor Cst, The drain node D is discharged and converged to the voltage of the source node S, as shown in FIG. As a result, deterioration information of the OLED element of the source node S is reflected to 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 turn on the data voltage Vdata, And the reference voltage Vref to the gate node G and the source node S of the driving TFT DT. Thus, 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 while the voltage of the drain node D Deterioration information of the OLED element reflected in the voltage changes deterioration information of the OLED element to the current of the driving TFT DT by changing the drain-source voltage Vds. The current of the driving TFT DT reflecting the deterioration information of the OLED element is charged with the voltage to the capacitor Cref of the reference line RL through the second switching TFT ST2.

As a result, in the sensing step, the voltage charged in the capacitor Cre of the reference line RL increases according to the current of the driving TFT DT as shown in Figs. 3 and 4, so that the voltage of the reference line RL also gradually increases . At this time, the magnitude of the voltage charged by the capacitor Cref, that is, the voltage slope and the voltage increase amount, which increase on the reference line RL, varies depending on the current of the driving TFT DT reflecting the deterioration information of the OLED element. The data driver 20 can sense the voltage charged in the capacitor Cref of the reference line RL at a desired point in the sensing step and output the sensing information reflecting the deterioration information of the OLED element.

As described above, the degradation sensing apparatus for an OLED element according to the present invention can sense deterioration information of an OLED element even in a pixel circuit of one scan structure. Accordingly, in the OLED display device to which the pixel circuit of one scan structure is applied, since the pixel aperture ratio increases more than the pixel circuit of the two scan structure, the current density of the OLED device can be reduced, have.

FIG. 6 is a graph illustrating a result of sensing the degree of deterioration of an OLED element using an apparatus for sensing deterioration of an OLED element according to the present invention. When the sensing voltage Vsen changes according to a change in a threshold voltage Vth due to deterioration of the OLED element, It can be seen that it changes.

FIG. 7 shows the degradation tendency of the OLED element sensed using the degradation sensing device of the OLED element according to the present invention. The anode voltage Vanode of the OLED element, that is, the driving TFT DT The amount of change of the voltage at the source node before and after deterioration is increased.

8 shows a sensing voltage Vsen according to the data voltage Vdata using the degradation sensing device of the OLED element according to the present invention. The sensing voltage Vsen varies depending on the data voltage Vdata, Vdata) changes with the degree of deterioration of the OLED element.

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

The OLED element degradation sensing apparatus shown in FIG. 9 differs from the OLED element degradation sensing apparatus shown in FIG. 2 in that a sub-pixel SP has a two-scan structure, Therefore, differences from the degradation sensing apparatus shown in FIG. 2 will be mainly described, and description 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 the different gate lines GL1 and GL2.

The width of the first scan pulse SC of the first gate line GL1 controlling the first switching TFT ST1 in the initializing step and the width of the first scan pulse SC of the second switching TFT The widths of the second scan pulse SE of the second gate line GL2 controlling the first scan line ST1 may be set to be different from each other.

For example, as shown in FIG. 10, when the width of the second half of the second scan pulse SE is larger than the width of the first scan pulse SC in the initialization step, The width of the first 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. 12, The source node S of the driving TFT DT through the second switching TFT ST2 is longer than the period during which the data voltage Vdata is supplied to the gate node G of the driving TFT DT via the first switching TFT ST1, The storage capacitor Cst supplies the difference voltage between the data voltage Vdata and the reference voltage Vref in the initializing step to the driving TFTs DT at a driving voltage Vgs.

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

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, Source voltage Vds is changed according to deterioration information of the OLED element reflected in the drain node D excluding the gate node G and the source node S of the first and second switching TFTs DT, ST1 and ST2 are simultaneously turned on, deterioration information of the OLED element can be reflected in the current of the driving TFT DT.

Alternatively, in the sensing step shown in FIGS. 10 to 12, only the second scan pulse SE is supplied and the first scan pulse SC is not supplied, so that the first switching TFT ST1 is turned off , The second switching TFT ST2 is turned on so that the gate node G of the driving TFT DT is floated and the source node S is supplied with the reference voltage Vref from the reference line RL . Accordingly, the voltage of the source node S is reduced to the reference voltage Vref which is lower than the voltage reduced by the discharge in the previous discharging step. At this time, deterioration information of the OLED element reflected on the source node S is transferred to the gate node G due to coupling of the storage capacitor Cst to change the driving voltage Vgs of the driving TFT DT, Is reflected in the current of the driving TFT DT by reflecting the voltage at the node D and the source node S and changing the drain-source voltage Vds. That is, in the two-scan structure, the deterioration information of the OLED element is reflected on all the nodes G, S, and 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 is increased to increase the sensing voltage, the sensing rate for the deterioration information of the OLED element can be improved.

FIG. 13 is a driving waveform diagram for explaining an OLED element degradation sensing process according to another embodiment of the present invention using the OLED element degradation sensing apparatus shown in FIG. 9, and FIGS. 14A to 14D are cross- And the OLED element degradation sensing process using waveforms.

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

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. And 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 supply EVDD to the high potential power supply line PH, and the second switch SW2 are turned on by the gate-on voltage of the second control signal to supply the first reference voltage Vref1 to the reference line RL.

14B, the first switching TFT ST1 is maintained in the turn-on state by the gate-on voltage of the first scan signal SC shown in Fig. 13, and the second scan signal SE is turned on by the gate- The second switching TFT ST2 is turned off by the gate-off voltage of the first switch SW1, 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 supplies a current corresponding to the driving voltage Vgs charged in the storage capacitor Cst to the OLED element to drive the OLED element. The gate node G of the driving TFT DT maintains the data voltage Vdata supplied through the first switching TFT ST1 while the drain node D of the floating 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 is reduced to the threshold voltage Vth of the OLED element. The deterioration information of the OLED element is reflected to the source node S by changing the voltage of the source node S according to the variation of the threshold voltage Vth which is deterioration information of the OLED element, Is also reflected in the gate-source voltage (Vgs = Vdata-OLED_Vth), so that the gate-source voltage Vgs of the driving TFT DT varies depending on the deterioration 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, 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, the reference line RL is supplied with the second reference voltage Vref2 <Vref1 different from the first reference voltage Vref1 in the first initialization step, and the second reference voltage Vref2 <Vref1 is supplied to the reference line RL through the second switching TFT ST2. The voltage of the source node S decreases to the second reference voltage Vref2 and is secondly initialized. At this time, the voltage of the floating gate node G is reduced 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, deterioration information of the OLED element reflected on the source node S is transmitted to the gate node G, so that deterioration information of the OLED element is reflected on 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 the turn-off state by the gate-off voltage of the first scan signal SC shown in FIG. 13, The second switching TFT ST2 maintains the turn-on state by the gate-on voltage of the first switch SW1, the first switch SW1 maintains the turn-on state by the gate-on voltage of the first control signal, (SW2) is turned off by the gate-off voltage of the second control signal.

The gate-source voltage Vgs changes according to the deterioration information of the OLED element reflected at the gate node G and the source node S of the driving TFT DT and the deterioration information of the OLED element Is reflected. The current of the driving TFT DT reflecting the deterioration 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 charged in the capacitor (Cref) of the reference line RL increases according to the current of the driving TFT DT as shown in Fig. 13, so that the voltage of the reference line RL also gradually increases. At this time, the magnitude of the voltage charged by the capacitor Cref, that is, the voltage slope and the voltage increase amount, which increase on the reference line RL, varies depending on the current of the driving TFT DT reflecting the deterioration information of the OLED element. The third switch SW3 is turned on at a desired point in the sensing step to sense the voltage charged in the capacitor Cref of the reference line RL and output the sensed voltage to the ADC so that the ADC outputs the sensing information reflecting the deterioration information of the OLED element Can be output to the timing controller.

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

FIG. 15 is an equivalent circuit diagram illustrating the construction of one pixel using the one-scan structure shown in FIG. 2, and FIG. 16 is an equivalent circuit diagram showing an example of the structure of one pixel using the two- 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, GL2, and share one reference line RL. Alternatively, the R / W / B / G subpixels may be connected to different reference lines, not shown. The 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 connected to the B / G subpixel And supplies a high potential voltage (EVDD). And the first switch SW1 shown in Fig. 2 and Fig. 9 are individually connected to the high potential power supply lines PH1 and PH2.

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

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

As described above, the apparatus and method for deterioration of an OLED element according to the present invention include driving the OLED element and interrupting the supply of the high-potential power, discharging all the nodes of the driving TFT, And the current of the driving TFT is changed according to the deterioration information of the OLED element reflected at the node so that the current of the driving TFT, which reflects deterioration information of the OLED element, is sensed regardless of the one-scan or two- Can be compensated for.

Particularly, in an OLED display device to which a pixel circuit of one scan structure is applied, since the pixel aperture ratio increases more than the pixel circuit of 2 scan structure, the current density of the OLED device can be reduced, and the degradation speed of the OLED device can be reduced, .

Further, in the OLED display device to which the pixel circuit of the two 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 current change of the driving TFT is increased according to the deterioration information of the OLED element, The sensing rate can be improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of illustration, Can be carried out within a range. Accordingly, such modifications are deemed to be within the scope of the present invention, and the scope of the present invention should be determined by the following claims.

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 (OLED) element using a driving thin film transistor (hereinafter, referred to as TFT)
Wherein a voltage of at least the second and third nodes among a first node which is a control node in the driving TFT, a second node which is connected to the OLED element and a third node to which high potential power is supplied, A second step of discharging through a current flowing from the driving TFT to the OLED element in a cutoff state,
And a third step of sensing, by voltage, a characteristic of varying the current of the driving TFT according to deterioration information of the OLED element. The method according to claim 1,
The first step
Supplying a data voltage from the data line to the first node through the first switching TFT, supplying a reference voltage to the second node through the second switching TFT, supplying the high potential power to the third node An initializing step of charging a driving voltage of the driving TFT to a storage capacitor between the first and second nodes,
Wherein the first and second switching TFTs are turned off and the voltage of the first and second nodes is boosted according to a current flowing from the driving TFT to the OLED element in a state where the high potential power is supplied to the third node, RTI ID = 0.0 &gt; of: &lt; / RTI &gt; The method of claim 2,
The second step
Wherein the first and second switching TFTs are turned on in response to a current flowing from the driving TFT to the OLED element in a state that the switch for supplying the high potential power supply to the high potential power supply line connected to the first node is turned off And discharging the first to third nodes,
In the third 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 the second node in which deterioration information of the OLED element is reflected and a second voltage between the first and second nodes, Charging the capacitor of the reference line through the second switching TFT with a current of the driving TFT which varies according to at least a first voltage of the second voltage,
Sensing a voltage charged in a capacitor of the reference line, and converting the sensing voltage into sensing data and outputting the sensed data. The method according to claim 1,
Wherein the first step supplies the data voltage from the data line to the first node through the first switching TFT and supplies the reference voltage to the second node through the second switching TFT, And an initializing step of supplying a driving voltage of the driving TFT to the storage capacitor between the first node and the second node,
Wherein the second step includes a step of controlling the current flowing from the driving TFT to the OLED element in a state in which the switch for supplying the high potential power to the high potential power supply line connected to the first node is turned off, And discharging the second node in accordance with the control signal,
In the third step,
The second switching TFT and the switch are turned on and the current of the driving TFT, which varies according to a first voltage between the first and second nodes, in which deterioration information of the OLED element is reflected, Charging the capacitor of the reference line,
Sensing the voltage charged in the capacitor of the reference line, converting the sensing voltage into sensing data, and outputting the sensing data,
Between the second and third steps, the step of initializing the second switching TFT and the switch is turned on and the reference line and the second node are initialized to a second reference voltage different from the reference voltage of the initialization step Of the OLED element. A first switching TFT for connecting the data line and the first node of the driving TFT, and a second switching circuit for connecting the second node of the driving TFT connected to the OLED element to the reference line, A TFT, a power supply line connected to a third node of the driving TFT, a subpixel including a storage capacitor between the first and second nodes,
A reference supply unit for supplying a reference voltage to the reference line; a sensing unit for sensing a voltage of the reference line; a switch for supplying a high potential power to the power line; Comprising a data driver,
Wherein the sub-pixel drives the OLED element by using the driving TFT, and in a state in which the supply of the high-potential power is cut off by the switch, at least the second and third nodes Discharging the current of the driving TFT by the current flowing from the driving TFT to the OLED element and then charging the capacitor of the reference line with the current of the driving TFT which is varied in accordance with the deterioration information of the OLED element, And the OLED element senses and outputs the voltage charged in the reference line. The method of claim 5,
The sub-
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 To charge the driving voltage of the driving TFT to the storage capacitor between the first and second nodes,
In the boosting step, the first and second switching TFTs are turned off, and the high-potential power is supplied to the third node. In accordance with the current flowing from the driving TFT to the OLED element, Lt; / RTI &gt; is boosted,
In the discharging step, the first and second switching TFTs and the first to third nodes are discharged in accordance with the current flowing from the driving TFT to the OLED element in a state in which the switch is turned off,
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, in which deterioration information of the OLED element is reflected, And charges the capacitor of the reference line through the second switching TFT, the current of the driving TFT being variable according to at least a first voltage of a second voltage between the second nodes. The method of claim 6,
Wherein the first and second switching TFTs are connected to one gate line or connected to two gate lines, respectively. The method of claim 5,
The sub-
In the 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 the second switching TFT, and the high- Supplying a driving voltage of the driving TFT to the storage capacitor between the first node and the second node,
In the discharging step, the second switching TFT and the second node discharge according to a current flowing from the driving TFT to the OLED element in a state in which the switch is turned off,
In the second initialization step, the second switching TFT and the switch are turned on, initializing the reference line and the second node to a second reference voltage different from the reference voltage of the first initialization step,
The second switching TFT and the switch are turned on and the current of the driving TFT, which is varied in accordance with the first voltage between the first and second nodes, in which deterioration information of the OLED element is reflected, And charges the capacitor of the reference line through the TFT.

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