KR20120069481A - Light emitting display device and driving method thereof - Google Patents

Abstract

PURPOSE: A light emitting display device and a driving method thereof are provided to improve image quality by compensating threshold voltage of a driving transistor. CONSTITUTION: A gate terminal of a first switching device(SW1) is connected to a second light emitting control line. A gate terminal of a second switching device(SW2) is connected to a first scan line. A capacitor(C) is connected between a second node and a third node. A gate terminal of a third switching device(SW3) is connected to the first scan line. A light emitting device(OLED) comprises a light emitting cell. A gate terminal of a driving transistor(DT) is connected to the second node. A gate terminal of a fourth switching device(SW4) is connected to a second scan line. A gate terminal of a fifth switching device(SW5) is connected to a first light emitting control line.

Description

LIGHT EMITTING DISPLAY DEVICE AND DRIVING METHOD THEREOF

The present invention relates to a light emitting display device, and more particularly, to a light emitting display device and a driving method thereof capable of improving image quality by compensating a threshold voltage of a driving transistor for driving a light emitting device.

Recently, the importance of flat panel displays has increased with the development of multimedia. In response to this, various flat panel displays such as a liquid crystal display, a plasma display panel, a field emission display, a light emitting display, and the like have been put to practical use. Among such flat panel displays, the light emitting display device has a high response time with a response speed of 1 ms or less, low power consumption, and no self-emission, thus having no problem in viewing angle.

In general, a light emitting display device is a display device that electrically emits light by emitting a light emitting material, and is classified into an inorganic light emitting display device and an organic light emitting display device according to its material and structure.

1 is a circuit diagram schematically illustrating a pixel structure of a general light emitting display device.

Referring to FIG. 1, a pixel of a typical light emitting display device includes a switching transistor ST, a driving transistor DT, a capacitor C, and a light emitting element OLED.

The switching transistor ST is switched according to the scan signal supplied to the scan line SL to supply the data voltage Vdata supplied to the data line DL to the driving transistor DT.

The driving transistor DT is switched according to the data voltage Vdata supplied from the switching transistor ST to control the data current idata flowing from the driving power supply Vdd to the light emitting element OLED.

The capacitor C is connected between the gate terminal of the driving transistor DT and the ground line VL to store a voltage corresponding to the data voltage Vdata supplied to the gate terminal of the driving transistor DT, and is driven by the stored voltage. The turn-on state of the transistor DT is kept constant for one frame.

The light emitting device OLED is electrically connected between the source terminal of the driving transistor DT and the ground power supply Vss to emit light by the data current idata supplied from the driving transistor DT. In this case, the data current idata flowing in the light emitting device OLED is applied to the voltage Vgs between the gate and the source of the driving transistor DT, the threshold voltage Vth of the driving transistor DT, and the data voltage Vdata. Is determined accordingly.

The pixel of the general light emitting display device controls the magnitude of the data current idata flowing from the driving power supply Vdd to the light emitting device OLED by switching the driving transistor DT according to the data voltage Vdata. By emitting the OLED, a predetermined image is displayed.

However, in the general light emitting display device, since the threshold voltages of the driving transistors DT included in each pixel are formed differently, even when the same data voltage Vdata is supplied to each pixel due to the deviation of the threshold voltages of the driving transistors DT, Since the data current idata output from the driving transistor DT is different, there is a problem that a uniform image quality cannot be realized. Since the threshold voltage deviation of the driving transistor M2 may increase as the light emitting display device becomes larger, it causes a deterioration in image quality of the large area light emitting display device.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a light emitting display device and a driving method thereof capable of improving image quality by compensating a threshold voltage of a driving transistor for driving a light emitting device.

Another object of the present invention is to provide a light emitting display device and a method of driving the same, which can improve contrast ratio by preventing a current generated when compensating a threshold voltage of a driving transistor for driving a light emitting device. .

Another object of the present invention is to provide a light emitting display device and a driving method thereof capable of improving image quality by preventing a current change of a light emitting device due to a change in a threshold voltage and a base power supply of a driving transistor for driving a light emitting device. It is a task.

According to an aspect of the present invention, there is provided a light emitting display device including a plurality of pixels formed for each pixel area defined by a data line, first and second scan lines, and first and second light emission control lines; Each of the plurality of pixels having a gate terminal connected to the second emission control line, a first terminal connected to a driving power supply, and a second terminal connected to a first node; A second switching element having a gate terminal connected to the first scan line, a first terminal connected to the first node, and a second terminal connected to a second node; A capacitor having a first terminal connected to the second node and a second terminal connected to a third node; A third switching element having a gate terminal connected to the first scan line, a first terminal connected to a reference power supply, and a second terminal connected to the third node; A light emitting device including an anode electrode connected to the third node, a cathode electrode connected to a ground power source, and a light emitting cell formed between the anode electrode and the cathode electrode; A driving transistor having a gate terminal connected to the second node, a drain terminal connected to the first node, and a source terminal connected to a fourth node; A fourth switching element having a gate terminal connected to a second scan line, a first terminal connected to the data line, and a second terminal connected to the fourth node; And a fifth switching element having a gate terminal connected to the first light emission control line, a first terminal connected to the third node, and a second terminal connected to a fourth node.

The capacitor may be initialized to a driving voltage supplied from the driving power during a period in which the first to third switching elements are turned on among the first to fifth switching elements.

The capacitor may store a sum voltage of a threshold voltage of the driving transistor and a data voltage supplied to the data line during a period in which the second to fourth switching elements are turned on among the first to fifth switching elements. do.

The second to fourth switching elements are turned off at the same time.

The capacitor may store a voltage difference between a gate terminal and a source terminal of the driving transistor during a period in which the fifth switching device is turned on among the first to fifth switching devices.

The light emitting device is connected to the difference voltage output from the driving transistor that is turned on by the difference voltage stored in the capacitor during a period in which the first and fifth switching devices are turned on among the first to fifth switching devices. It is characterized in that the light emission by the corresponding data current.

The light emitting display device according to the present invention for achieving the above-described technical problem is formed in the pixel region defined by the data line, the first and second scan line, the first and second light emission control line, the data current through the driving transistor A pixel circuit for outputting the; And a light emitting element emitting light by the data current output from the pixel circuit, wherein the pixel circuit includes a first scan signal supplied to the first scan line and a second light emission control supplied to the second light emission control line. An initialization unit configured to initialize the capacitor using different driving voltages and reference voltages in response to the signal; The sum voltage of the threshold voltage and the data voltage of the driving transistor is obtained by using the data voltage and the reference voltage supplied to the data line in response to the second scan signal supplied to the first scan signal and the second scan line. A threshold voltage compensator for storing in a capacitor; A voltage program unit configured to store a program voltage corresponding to a difference voltage between a gate voltage and a source voltage of the driving transistor in the capacitor in response to a first emission control signal supplied to the first emission control line; And turning on the driving transistor according to the program voltage stored in the capacitor in response to the first light emission control signal and the second light emission control signal supplied to the second light emission control line, the data corresponding to the program voltage. And a light emission controller for supplying current to the light emitting device.

According to an aspect of the present invention, a driving method of a light emitting display device is formed in a pixel area defined by a data line, a first and a second scan line, and a first and a second light emission control line, thereby driving a driving transistor. A driving method of a light emitting display device, comprising: a pixel circuit outputting a data current through a light emitting element; and a light emitting element emitting light by the data current output from the pixel circuit; An initialization step of initializing a capacitor using different driving voltages and reference voltages in response to a second emission control signal supplied to the second emission control line; A threshold voltage compensation step of storing a sum voltage of a data voltage supplied to the data line and a threshold voltage of the driving transistor in the capacitor in response to the first scan signal and the second scan signal supplied to the second scan line; A program step of storing a program voltage corresponding to a difference voltage between a gate voltage and a source voltage of the driving transistor in the capacitor in response to a first light emission control signal supplied to the first light emission control line; And turning on the driving transistor according to the program voltage stored in the capacitor in response to the first light emission control signal and the second light emission control signal supplied to the second light emission control line, the data corresponding to the program voltage. And a light emitting step of supplying a current to the light emitting device.

As described above, the light emitting display device and the driving method thereof according to the present invention have the following effects.

First, the image quality may be improved by compensating the threshold voltage of the driving transistor driving the light emitting device.

Second, the contrast ratio may be improved by preventing unwanted current generated in the threshold voltage compensation of the driving transistor DT from flowing to the light emitting device.

Third, the image quality may be improved by preventing a current change of the light emitting device due to a change in the threshold voltage and the base voltage of the driving transistor.

1 is a circuit diagram schematically illustrating a pixel structure of a general light emitting display device.
2 is a diagram schematically illustrating a light emitting display device according to an exemplary embodiment of the present invention.
3 is a diagram schematically illustrating a structure of a pixel according to the first embodiment of the present invention illustrated in FIG. 2.
4 is a driving waveform diagram illustrating a method of driving a light emitting display device according to an exemplary embodiment of the present invention.
5A through 5D are diagrams illustrating a driving state of the pixel for each section illustrated in FIG. 4.
6 is a driving waveform diagram illustrating a method of driving a light emitting display device according to another exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram schematically illustrating a light emitting display device according to an exemplary embodiment of the present invention.

Referring to FIG. 2, a light emitting display device according to an exemplary embodiment of the present invention includes a display panel 100, a timing controller 200, and a panel driver 300.

The display panel 100 includes a plurality of pixels P formed for each pixel area defined by m data lines DL to Dm, n scan lines S1 to Sn, and n emission control lines E1 to En. It is configured to include).

Each of the plurality of pixels P may have a data line D1 according to a signal supplied to each of the first and second scan lines Si-1 and Si and the first and second emission control lines Ei and Ei + 1. A predetermined color image is displayed by emitting light from the light emitting device OLED according to a data current corresponding to a data voltage supplied from the same. Here, the first scan line Si-1 is defined as the i-1th scan line among the n scan lines S1 to Sn, and the second scan line Si is n scan lines S1 to Sn. Is defined as the i th scan line. The first emission control line Ei is defined as the i th emission control line of the n emission control lines E1 to En, and the second emission control line Ei + 1 is the n emission control line E1. N) is defined as the i + 1th light emission control line. A detailed description of each of the plurality of pixels P will be described later.

The timing controller 200 may be configured to drive red, green, and blue input data (Ri / Gi / Bi) input from an external system main body (not shown) or a graphics card (not shown) to drive the display panel 100. And the aligned data R / G / B is supplied to the panel driver 300.

In addition, the timing controller 200 controls the driving timing of the panel driver 300 according to a timing synchronization signal TSS input from an external system main body or a graphics card. In this case, the panel driver 300 may include a scan driver 310 and a data driver 320 which will be described later. Accordingly, the timing controller 300 may scan the scan control signal SCS based on the timing synchronization signal TSS such as the vertical synchronization signal Vsync, the horizontal synchronization signal Hsync, the data enable DE, and the clock DCLK. ) And the data control signal DCS are generated to control the driving timing of the scan driver 310 and the data driver 320.

The scan driver 310 generates a scan signal according to the scan control signal SCS provided from the timing controller 200 and sequentially supplies the scan signal to the plurality of scan lines S1 to Sn. That is, the scan driver 310 shifts a scan signal having an on state only for two horizontal sections in units of one horizontal section, and sequentially supplies the scan signal to each of the plurality of scan lines S1 to Sn. Accordingly, the first scan signal supplied to the first scan line Si-1 and the second scan signal supplied to the second scan line Si overlap each other for one horizontal period.

In addition, the scan driver 310 emits light in an off state overlapping the first and second scan signals in an on state according to the scan control signal SCS or the scan signal provided from the timing controller 200. The control signal is generated and sequentially supplied to the plurality of light emission control lines E1 to En. That is, the scan driver 310 shifts the light emission control signal having an off state only for three horizontal sections in units of one horizontal section and sequentially supplies the light emission control signals to the plurality of light emission control lines E1 to En. Accordingly, the first emission control signal supplied to the first emission control line Ei and the second emission control signal supplied to the second emission control line Ei + 1 overlap for two horizontal periods. Meanwhile, the first emission control signal has an on state corresponding to the remaining horizontal sections except for three horizontal sections overlapping the first and second scan signals in the on state.

The data driver 320 converts the alignment data R / G / B supplied from the timing controller 200 into an analog data voltage according to the data control signal DCS provided from the timing controller 200. The converted data voltage is supplied to the corresponding data lines D1 to Dm during one horizontal period where the first and second scan signals overlap. That is, the data driver 320 sequentially latches alignment data R / G / B for one horizontal line sequentially supplied in response to the data control signal DCS, and latches one of a plurality of different gamma voltages. The gamma voltage corresponding to the alignment data R / G / B is selected as the data voltage and supplied to the data lines D1 to Dm.

As described above, the light emitting display device according to an exemplary embodiment of the present invention sequentially supplies the first and second scan signals to the first and second scan lines Si-1 and Si, and simultaneously the first and second emission control lines. The first and second emission control signals are sequentially supplied to (Ei, Ei + 1), and data voltages corresponding to the input data Ri / Gi / Bi are applied during a horizontal period in which the first and second scan signals overlap. The pixels P are supplied to the pixels P through the data lines D1 to Dm. Accordingly, each pixel P displays a predetermined color image by emitting light of the light emitting device OLED according to the data current corresponding to the data voltage using the driving voltage Vdd and the reference voltage Vref.

3 is a diagram schematically illustrating a structure of a pixel according to the first embodiment of the present invention illustrated in FIG. 2.

Referring to FIG. 3, the pixel P according to the first embodiment of the present invention includes a pixel circuit PC and a light emitting device OLED.

The pixel circuit PC includes first to fifth switching elements SW1 to SW5, a capacitor C, and a driving transistor DT.

The first switching element SW1 is connected to a gate terminal connected to the second emission control line Ei + 1, a first terminal (for example, a source terminal) connected to a driving power supply, and a first node n1. A second terminal (for example, a drain terminal). The first switching device SW1 is switched according to the second light emission control signal to supply the driving voltage Vdd supplied from the driving power source to the first node n1. That is, the first switching element SW1 is turned on only when the second emission control signal is in an on state, and the driving voltage Vdd is applied to the drain terminal of the driving transistor DT connected to the first node n1. ).

The second switching element SW2 includes a gate terminal connected to the first scan line Si-1, a first terminal (eg, a source terminal) connected to the first node n1, and a second node n2. A second terminal (for example, a drain terminal) connected to the) is provided. The second switching element SW2 is switched according to the first scan signal to electrically connect the first node n1 and the second node n2 connected to the gate terminal of the driving transistor DT. That is, the second switching device SW2 is turned on only when the first scan signal is in an on state to electrically connect the gate terminal and the drain terminal of the driving transistor DT, or the first switching device ( The driving voltage Vdd supplied to the first node n1 is supplied to the second node n2 through SW1.

The capacitor C is connected or formed between the second node n2 and the third node n3 connected to the anode electrode of the light emitting element OLED. At this time, the capacitor C has a first terminal connected to the second node n1, and a second terminal connected to the third node n3. The capacitor C stores the difference voltage between the second node n1 and the third node n3 and switches the driving transistor DT using the stored voltage.

The third switching element SW3 is connected to a gate terminal connected to the first scan line Si-1, a first terminal (for example, a source terminal) connected to the reference power supply, and a third node n3. A second terminal (eg, drain terminal) is provided. The third switching device SW3 is switched according to the first scan signal to supply the reference voltage Vref supplied from the reference power source to the third node n3. That is, the third switching device SW3 is turned on only when the first scan signal is in an on state to supply the reference voltage Vref to the third node n3. Here, the reference voltage Vref may be 0V, a base voltage, or a DC voltage without a voltage drop (eg, a voltage between a base low voltage and a driving voltage).

The driving transistor DT includes a gate terminal connected to the second node n2, a drain terminal connected to the first node n1, and a source terminal connected to the fourth node n4. The driving transistor DT has a diode-type connection structure according to the electrical connection between the gate terminal and the drain terminal according to the switching of the second switching element SW2. In addition, the driving transistor DT is switched according to the program voltage stored in the capacitor C to output a data current corresponding to the program voltage to the fourth node n4.

The fourth switching element SW4 is connected to a gate terminal connected to the second scan line Si, a first terminal (for example, a source terminal) connected to the data line D1, and a fourth node n4. A second terminal (for example, a drain terminal). The fourth switching device SW4 is switched according to the second scan signal to supply the data voltage supplied to the data line D1 to the fourth node n4. That is, the fourth switching device SW4 is turned on only when the second scan signal is in an on state to supply a data voltage to the fourth node n4.

The fifth switching element SW5 includes a gate terminal connected to the first emission control line Ei, a first terminal (for example, a source terminal) connected to the third node n3, and a fourth node n4. It is provided with the 2nd terminal (for example, drain terminal) connected to the. The fifth switching element SW5 is turned on only when the first emission control signal is in an on state to electrically connect the third node n3 and the fourth node n4.

The light emitting device OLED emits light by the data current supplied from the driving transistor DT. To this end, the light emitting element OLED includes an anode electrode (or a pixel electrode) connected to the third node n3, a cathode electrode (or a reflective electrode) connected to the base power source, and a light emitting cell formed between the anode electrode and the cathode electrode. It is configured to include. The light emitting cell may include a hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer.

In the above-described pixel P, the pixel circuit PC is initialized according to switching of each of the first to fifth switching elements SW1 to SW5 according to the first and second scan signals and the first and second emission control signals. The light emitting device OLED is turned on / off through processes such as threshold voltage compensation, voltage program, and light emission. Accordingly, the pixel circuit PC includes an initializer, a threshold voltage compensator, a voltage program unit, and a light emission controller that operate according to the switching of the first to fifth switching elements SW1 to SW5 described above. can see.

The initialization unit supplies the driving voltage Vdd to the drain terminal of the driving transistor DT in accordance with the second emission control signal in the on state, and drives the driving transistor DT in accordance with the first scanning signal in the on state. By electrically connecting the gate terminal and the drain terminal thereof to supply the driving voltage Vdd to the first terminal of the capacitor C, and to supply the reference voltage Vref to the second terminal of the capacitor C. ) And the capacitor C are initialized to the driving voltage Vdd using the reference voltage Vref. That is, the initialization unit may include the first to third switching devices SW1, which are turned on according to the first scan signal and the second emission control signal, which are in an on state, among the first to fifth switching devices SW1 to SW5. The capacitor C is initialized to the driving voltage Vdd using only SW2 and SW3.

The threshold voltage compensator capacitors the threshold voltage of the data voltage and the driving transistor DT by using the data voltage and the reference voltage Vref supplied to the data line Dl according to the first and second scan signals in the on state. Store in (C). That is, the threshold voltage compensator blocks the driving voltage Vdd supplied to the drain terminal of the driving transistor DT according to the second emission control signal in the on state, and the second scan signal in the on state. After supplying the data voltage to the source terminal of the driving transistor DT, and supplying the reference voltage (Vref) to the second terminal of the capacitor (C) in accordance with the first scan signal of the on (On) state, the driving transistor The threshold of the driving transistor DT is supplied to the capacitor C by electrically connecting the gate terminal and the drain terminal of the DT to supply the data voltage and the threshold voltage to the first terminal of the capacitor C through the driving transistor DT. Stores voltage and data voltage. As a result, the threshold voltage compensator may include the second to fourth switching devices SW2, which are turned on in response to the first and second scan signals in an on state among the first to fifth switching devices SW1 to SW5. The data voltage and the threshold voltage of the driving transistor DT are stored in the capacitor C by using the SW3 and SW4.

The voltage program unit stores the program voltage corresponding to the difference voltage between the gate voltage and the source voltage of the driving transistor DT in the capacitor C according to the first emission control signal in the on state. That is, the voltage program unit cuts off the driving voltage Vdd supplied to the drain terminal of the driving transistor DT according to the second emission control signal in the on state and at the same time the first emission control signal in the on state. The reference voltage supplied to the second terminal of the capacitor C according to the first scan signal of the on state and cut off the electrical connection between the source terminal of the driving transistor DT and the data line Vref) is cut off and the electrical connection between the gate terminal and the drain terminal of the driving transistor DT is cut off, and the gate terminal of the driving transistor DT is electrically connected to the first terminal of the capacitor C. The gate terminal of the driving transistor DT by electrically connecting the source terminal of the driving transistor DT to the second terminal of the capacitor C and the light emitting element OLED according to the first light emission control signal in the on state. Source terminal The program voltage corresponding to the voltage difference is stored in the capacitor (C). In this case, the program voltage becomes a sum voltage of the data voltage and the threshold voltage of the driving transistor DT. As a result, the voltage program unit may use the driving transistor DT using only the fifth switching element SW5 that is turned on according to the first light emission control signal of the on state among the first to fifth switching elements SW1 to SW5. The program voltage corresponding to the difference voltage between the gate terminal and the source terminal of the () is stored in the capacitor (C).

The light emission controller turns on the driving transistor DT according to the program voltage stored in the capacitor C in response to the first and second light emission control signals in the on state, thereby emitting a data current corresponding to the program voltage. The light emitting element OLED is made to emit light by supplying it to the OLED. That is, the light emission controller cuts off the electrical connection between the source terminal of the driving transistor DT and the data line Dl according to the second scan signal in the on state, and applies the first scan signal in the on state. Accordingly, the reference voltage Vref supplied to the second terminal of the capacitor C is cut off, and the electrical connection between the gate terminal and the drain terminal of the driving transistor DT is cut off, thereby closing the gate terminal of the driving transistor DT. (C) is electrically connected to the first terminal and supplies a driving voltage (Vdd) to the drain terminal of the driving transistor (DT) in accordance with the second light emission control signal of the on (On) state, The source terminal of the driving transistor DT is electrically connected to the second terminal of the capacitor C and the light emitting element OLED according to the first light emission control signal, thereby driving the driving transistor DT according to the program voltage stored in the capacitor C. Turn on Supplying a data current corresponding to the program voltage to the light emitting element (OLED) to emit a light-emitting device (OLED). As a result, the light emission controller may control the first and fifth switching devices SW1, which are turned on according to the first and second light emission control signals that are in an on state among the first to fifth switching devices SW1 to SW5. The driving transistor DT is turned on according to the program voltage stored in the capacitor C using only SW5 to supply a data current corresponding to the program voltage to the light emitting device OLED to emit light. In this case, the data current supplied from the driving transistor DT to the light emitting device OLED is determined only by the data voltage as shown in Equation 1 below.

In Equation 1, idata denotes the output current of the driving transistor, K denotes the gain factor of the driving transistor, Vgs denotes the gate-source voltage of the driving transistor, and Vth denotes the threshold voltage of the driving transistor. Vdata represents the data voltage.

Therefore, the light emitting display device according to an exemplary embodiment of the present invention can improve image quality defects due to the deviation of the threshold voltage of the driving transistor DT for each pixel P.

4 is a driving waveform diagram illustrating a method of driving a light emitting display device according to an exemplary embodiment of the present invention, and FIGS. 5A to 5D are diagrams illustrating a driving state of a pixel for each section illustrated in FIG. 4.

A driving method of a light emitting display device according to an exemplary embodiment of the present invention will be described with reference to FIG. 4 with FIGS. 5A to 5D.

First, a driving method of a light emitting display device according to an exemplary embodiment of the present invention includes each pixel P through an initialization period T1, a threshold voltage compensation period T2, a voltage program period T3, and an emission period T4. To drive.

As shown in FIG. 4 and FIG. 5A, in the initialization period T1, the first scan signal SSi-1 and the second emission control line in the on state supplied to the first scan line Si-1 are provided. The capacitor C is initialized to the driving voltage Vdd in response to the second emission control signal ECSi + 1 in the on state supplied to (Ei + 1). That is, in the initialization period T1, the first scan signal SSi-1 and the second emission control signal ECSi + 1 are turned on among the first to fifth switching elements SW1 to SW5. The capacitor C is initialized to the driving voltage Vdd using only the first to third switching elements SW1, SW2, and SW3 that are turned on.

Specifically, in the initialization period T1, the first switching device SW1 is turned on in response to the second emission control signal ECSi + 1 in the on state supplied to the second emission control line Ei + 1. The driving voltage Vdd is supplied to the first node n1, that is, the drain terminal of the driving transistor DT by turning on. At the same time, in the initialization period T1, the second and third switching devices SW2 and SW3 are connected in response to the first scan signal SSi-1 in the on state supplied to the first scan line Si-1. By turning on, the driving voltage Vdd is supplied to the second node n2, that is, the first terminal of the capacitor C, through the gate terminal and the drain terminal of the driving transistor DT, and at the same time, the reference voltage Vref is provided. The third node n3, that is, the second terminal of the capacitor C is supplied. Accordingly, the voltage Vc of the capacitor C corresponds to the voltage Vn2 of the second node n2 supplied with the driving voltage Vdd and the voltage V3 of the third node n3 supplied with the reference voltage Vref. Is initialized to the driving voltage Vdd by Vn3). During the initialization period T1, the light emitting device OLED is turned off by the reference voltage Vref supplied to the anode electrode through the third switching device SW3.

Subsequently, as illustrated in FIGS. 4 and 5B, in the threshold voltage compensation period T2, the first and second scans of the on state supplied to the first and second scan lines Si-1 and Si are provided. The data voltage Vdata and the threshold voltage Vth of the driving transistor DT are supplied to the capacitor C in response to the signals SSi-1 and SSi. That is, in the threshold voltage compensation period T2, the second to fourth switching elements that are turned on according to the first and second scan signals of the on state among the first to fifth switching elements SW1 to SW5. The data voltage Vdata and the threshold voltage Vth of the driving transistor DT are stored in the capacitor C by using the SW2, SW3, and SW4.

Specifically, in the threshold voltage compensation period T2, the first switching device SW1 is applied in response to the second emission control signal ECSi + 1 in an off state supplied to the second emission control line Ei + 1. The third node is turned off and the fourth switching element SW4 is turned on according to the second scan signal SSi in the on state supplied to the second scan line Si. (n3), that is, the data voltage Vdata is supplied to the source terminal of the driving transistor DT. At the same time, in the threshold voltage compensation period T2, the second switching element (On) is turned on by the first scan signal SSi-1 in the on state supplied to the first scan line Si-1. The gate terminal and the drain terminal of the driving transistor DT are electrically connected through the SW2 to connect the data voltage Vdata and the threshold voltage Vth of the driving transistor DT to the second node n2, that is, the capacitor C. The third node n3, i.e., the capacitor (3) through the third switching element SW3, which is turned on by the first scan signal SSi-1 of the on state while being supplied to the first terminal of The reference voltage Vref is supplied to the second terminal of C). Accordingly, the voltage Vc of the capacitor C is the voltage Vn2 and the reference voltage Vref of the second node n2 to which the data voltage Vdata and the threshold voltage Vth of the driving transistor DT are supplied. The sum voltage Vdata + Vth of the data voltage Vdata and the threshold voltage Vth of the driving transistor DT is stored by the supplied voltage Vn3 of the third node n3. During the threshold voltage compensation period T2, the light emitting device OLED is turned off by the reference voltage Vref supplied to the anode electrode through the third switching device SW3. The threshold voltage compensation period T2 is maintained until the second scan signal SSi in the off state is supplied to the second scan line Si.

Subsequently, as shown in FIGS. 4 and 5C, in the voltage program section T3, the gate voltage of the driving transistor DT in response to the first emission control signal ECSi supplied to the first emission control line Ei. The program voltage corresponding to the difference voltage Vgs between Vn2 and the source voltage Vn3 is stored in the capacitor C. That is, in the voltage program section T3, driving is performed using only the fifth switching device SW5 which is turned on according to the first emission control signal of the on state among the first to fifth switching devices SW1 to SW5. The program voltage corresponding to the difference voltage Vgs between the gate terminal and the source terminal of the transistor DT is stored in the capacitor C.

In detail, in the voltage program section T3, turns in accordance with the first and second scan signals SSi-1 and SSi in an off state supplied to the first and second scan lines Si-1 and Si. The first terminal of the capacitor C is connected to the gate terminal of the driving transistor DT through the second to fourth switching elements SW2, SW3, and SW4 that are turned off, and the second terminal of the capacitor C is connected. It is connected to the anode electrode of the light emitting element OLED. At the same time, in the voltage program section T3, the fifth switching element SW5 is turned on according to the first emission control signal ECSi in the on state supplied to the first emission control line Ei, thereby turning on the capacitor ( The second terminal of C) and the source terminal of the driving transistor DT are connected. Accordingly, the voltage Vc of the capacitor C stores the program voltage corresponding to the difference voltage Vgs between the gate terminal and the source terminal of the driving transistor DT in the capacitor C. As a result, during the voltage program period T3, the capacitor C maintains the sum voltage Vdata + Vth of the threshold voltage Vth of the driving transistor DT stored during the voltage compensation period T2.

Subsequently, as shown in FIGS. 4 and 5D, in the emission period T4, the first and second emission control in an on state supplied to the first and second emission control lines Ei and Ei + 1. The driving transistor DT is turned on according to the program voltage stored in the capacitor C in response to the signals ECSi and ECSi + 1 to supply the data current idata corresponding to the program voltage to the light emitting device OLED. . That is, in the emission period T4, the first and second turned-on signals are turned on in response to the first and second emission control signals ECSi and ECSi + 1 in the on state among the first to fifth switching elements SW1 to SW5. The driving transistor DT is turned on according to the program voltage stored in the capacitor C using only the fifth switching elements SW1 and SW5 to supply the data current idata corresponding to the program voltage to the light emitting device OLED. The light emitting element OLED is caused to emit light.

In detail, in the emission period T4, the source terminal of the driving transistor DT and the data line D1 are electrically connected to each other according to the second scan signal SSi in the off state supplied to the second scan line Si. Block access At the same time, in the emission period T4, the reference voltage is supplied to the second terminal of the capacitor C according to the first scan signal SSi-1 in the off state supplied to the first scan line Si-1. The gate terminal of the driving transistor DT is electrically connected to the first terminal of the capacitor C by blocking (Vref) and interrupting electrical connection between the gate terminal and the drain terminal of the driving transistor DT. At the same time, in the light emission period T4, a driving voltage is applied to the drain terminal of the driving transistor DT according to the second light emission control signal ECSi + 1 in the on state supplied to the second light emission control line Ei + 1. The source terminal of the driving transistor DT is connected to the second terminal of the capacitor C according to the first emission control signal ECSi in the on state supplied to the first emission control line Ei while supplying Vdd. The terminal is electrically connected to the anode electrode of the light emitting element OLED. Accordingly, during the light emission period T4, the capacitor C turns on the driving transistor DT according to the stored program voltage, and the turned-on driving transistor DT is driven as shown in Equation 1 above. The data current idata corresponding to the program voltage is supplied to the light emitting device OLED by using Vdd. Therefore, the light emitting device OLED emits light by the data current idata supplied from the driving transistor DT to display a predetermined color image. Here, the light emitting device OLED continues to emit light until the initialization section T1 of the next frame.

The light emitting display device and the driving method thereof according to the embodiment of the present invention described above can improve image quality by compensating the threshold voltage of the driving transistor DT for driving the light emitting device OLED.

In addition, the present invention may improve the contrast ratio by preventing unwanted current generated in the threshold voltage compensation of the driving transistor DT driving the light emitting device OLED from flowing into the light emitting device OLED. That is, the present invention instantaneously during the initialization section T1 and the voltage compensation section T2 by supplying the reference voltage Vref to the anode electrode of the light emitting device OLED during the initialization section T1 and the voltage compensation section T2. The contrast ratio may be improved by preventing the current glitch generated from the generated current flowing through the light emitting device OLED.

In addition, since the current change of the light emitting device OLED according to the threshold voltage change of the driving transistor DT is small and the current change of the light emitting device OLED according to the change of the base voltage Vss is small, the image quality may be improved. Can be.

Meanwhile, in the above-described light emitting display device and a driving method thereof, a plurality of scan lines S1 to Sn are sequentially shifted by shifting a scan signal having an on state for two horizontal sections by one horizontal section. ), The scan signal SSi-1 supplied to the previous scan line Si-1 of each pixel P is described.

However, in the light emitting display device and the driving method thereof according to another embodiment of the present invention, one scan line is added to each pixel P, and as shown in FIG. 6, the first scan of two separated scan lines The line is supplied with a first scan signal SS1 having an on state for two horizontal sections, and the second scan line is shifted by one horizontal section from the first scan signal SS1 to a second scan line of the two scan lines. The second scan signal SS2 having an on state overlapped with the scan signal SS1 for one horizontal period is supplied. Accordingly, the light emitting display device and the driving method thereof according to another exemplary embodiment of the present invention use the above-described first and second scan signals SS1 and SS2 to perform the above-described threshold voltage compensation period T2 and emission period T3. The first and second scan signals SSi and SSi + 1 in the off state are supplied to the first and second scan lines during the period between the first and second scan lines to compensate for the threshold voltage of the driving transistor DT. You can certainly minimize the effects of the parasitic capacitor.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

100: display panel 200: timing control unit
300: panel driver 310: scan driver
320: data driver

Claims (21)

A plurality of pixels formed for each pixel region defined by the data line, the first and second scan lines, and the first and second emission control lines;
Each of the plurality of pixels,
A first switching element having a gate terminal connected to the second light emission control line, a first terminal connected to a driving power supply, and a second terminal connected to a first node;
A second switching element having a gate terminal connected to the first scan line, a first terminal connected to the first node, and a second terminal connected to a second node;
A capacitor having a first terminal connected to the second node and a second terminal connected to a third node;
A third switching element having a gate terminal connected to the first scan line, a first terminal connected to a reference power supply, and a second terminal connected to the third node;
A light emitting device including an anode electrode connected to the third node, a cathode electrode connected to a ground power source, and a light emitting cell formed between the anode electrode and the cathode electrode;
A driving transistor having a gate terminal connected to the second node, a drain terminal connected to the first node, and a source terminal connected to a fourth node;
A fourth switching element having a gate terminal connected to a second scan line, a first terminal connected to the data line, and a second terminal connected to the fourth node; And
And a fifth switching element having a gate terminal connected to the first light emission control line, a first terminal connected to the third node, and a second terminal connected to a fourth node. Device. The method of claim 1,
The capacitor is initialized to a driving voltage supplied from the driving power during a period in which the first to third switching elements are turned on among the first to fifth switching elements. . The method of claim 1,
The capacitor may store a sum voltage of a threshold voltage of the driving transistor and a data voltage supplied to the data line during a period in which the second to fourth switching elements are turned on among the first to fifth switching elements. Light emitting display device. The method of claim 3, wherein
And the second to fourth switching elements are turned off at the same time. The method of claim 1,
And the capacitor stores a voltage difference between a gate terminal and a source terminal of the driving transistor during a period in which the fifth switching device is turned on among the first to fifth switching devices. The method of claim 5, wherein
The light emitting device is connected to the difference voltage output from the driving transistor that is turned on by the difference voltage stored in the capacitor during a period in which the first and fifth switching devices are turned on among the first to fifth switching devices. The light emitting display device, characterized in that to emit light by a corresponding data current. A pixel circuit formed in a pixel region defined by a data line, first and second scan lines, and first and second light emission control lines to output a data current through a driving transistor; And
A light emitting element emitting light by the data current output from the pixel circuit,
The pixel circuit,
An initialization unit configured to initialize a capacitor using different driving voltages and reference voltages in response to a first scan signal supplied to the first scan line and a second emission control signal supplied to the second emission control line;
The sum voltage of the threshold voltage and the data voltage of the driving transistor is obtained by using the data voltage and the reference voltage supplied to the data line in response to the second scan signal supplied to the first scan signal and the second scan line. A threshold voltage compensator for storing in a capacitor;
A voltage program unit configured to store a program voltage corresponding to a difference voltage between a gate voltage and a source voltage of the driving transistor in the capacitor in response to a first emission control signal supplied to the first emission control line; And
The data current corresponding to the program voltage by turning on the driving transistor according to the program voltage stored in the capacitor in response to the first emission control signal and the second emission control signal supplied to the second emission control line. And a light emission controller for supplying the light to the light emitting elements. The method of claim 7, wherein
The initialization unit,
Supplying the driving voltage to a drain terminal of the driving transistor in response to the second emission control signal;
The gate terminal and the drain terminal of the driving transistor are electrically connected to each other according to the first scan signal to supply the driving voltage to the first terminal of the capacitor, and at the same time to supply the reference voltage to the second terminal of the capacitor. And reset the voltage to the driving voltage. The method of claim 7, wherein
The threshold voltage compensator,
Cut off the driving voltage supplied to the drain terminal of the driving transistor in response to the second emission control signal, and supply the data voltage to the source terminal of the driving transistor in response to the second scan signal;
The reference voltage is supplied to the second terminal of the capacitor in response to the first scan signal, and the gate terminal and the drain terminal of the driving transistor are electrically connected to each other to drive the first terminal of the capacitor through the driving transistor. The sum of the threshold voltage of the transistor and the data voltage is supplied to the light emitting display device. The method of claim 7, wherein
The program unit,
Blocking the driving voltage supplied to the drain terminal of the driving transistor in response to the second light emission control signal and blocking electrical connection between the source terminal of the driving transistor and the data line in response to the second scanning signal. and,
Blocking the reference voltage supplied to the second terminal of the capacitor in response to the first scan signal, and simultaneously disconnecting the gate terminal and the drain terminal of the driving transistor to electrically connect the gate terminal of the driving transistor to the capacitor. Is electrically connected to the first terminal of
And a source terminal of the driving transistor is electrically connected to a second terminal of the capacitor and the light emitting element in response to the first light emission control signal. 11. The method of claim 10,
The light emission controller supplies the driving voltage to a drain terminal of the driving transistor in response to the second light emission control signal, and connects a source terminal of the driving transistor to a second terminal of the capacitor in response to the first light emission control signal. And a light emitting device electrically connected to the light emitting element. A pixel circuit formed in a pixel region defined by a data line, a first and a second scan line, and a first and a second emission control line to output a data current through a driving transistor, and to the data current output from the pixel circuit. A driving method of a light emitting display device including a light emitting element that emits light by
An initialization step of initializing a capacitor using different driving voltages and reference voltages in response to a first scan signal supplied to the first scan line and a second emission control signal supplied to the second emission control line;
A threshold voltage compensation step of storing a sum voltage of a data voltage supplied to the data line and a threshold voltage of the driving transistor in the capacitor in response to the first scan signal and the second scan signal supplied to the second scan line;
A program step of storing a program voltage corresponding to a difference voltage between a gate voltage and a source voltage of the driving transistor in the capacitor in response to a first light emission control signal supplied to the first light emission control line; And
The data current corresponding to the program voltage by turning on the driving transistor according to the program voltage stored in the capacitor in response to the first emission control signal and the second emission control signal supplied to the second emission control line. And a light emitting step of supplying the light to the light emitting element. The method of claim 12,
The initialization step,
Supplying the driving voltage to a drain terminal of the driving transistor in response to the second emission control signal; And
The gate terminal and the drain terminal of the driving transistor are electrically connected to each other according to the first scan signal to supply the driving voltage to the first terminal of the capacitor, and to supply the reference voltage to the second terminal of the capacitor. And initializing to the driving voltage. The method of claim 12,
The threshold voltage compensation step,
Blocking the driving voltage supplied to the drain terminal of the driving transistor in response to the second emission control signal and simultaneously supplying the data voltage to the source terminal of the driving transistor in response to the second scan signal; And
The reference voltage is supplied to the second terminal of the capacitor in response to the first scan signal, and the gate terminal and the drain terminal of the driving transistor are electrically connected to each other to drive the first terminal of the capacitor through the driving transistor. And a sum voltage of a threshold voltage of the transistor and the data voltage is supplied. 15. The method of claim 14,
The program step,
Blocking the driving voltage supplied to the drain terminal of the driving transistor in response to the second light emission control signal and blocking electrical connection between the source terminal of the driving transistor and the data line in response to the second scanning signal. Making;
Blocking the reference voltage supplied to the second terminal of the capacitor in response to the first scan signal, and simultaneously disconnecting the gate terminal and the drain terminal of the driving transistor to electrically connect the gate terminal of the driving transistor to the capacitor. Electrically connecting to a first terminal of; And
And a source terminal of the driving transistor is electrically connected to a second terminal of the capacitor and the light emitting element in response to the first light emission control signal. 15. The method of claim 14,
In the light emitting step, the driving voltage is supplied to the drain terminal of the driving transistor in response to the second emission control signal, and the source terminal of the driving transistor is connected to the second terminal of the capacitor in response to the first emission control signal. And electrically connected to the light emitting element. The method of claim 12,
The initialization step,
Turning on a first switching element in response to the second light emission control signal to supply the driving voltage to a drain terminal of the driving transistor;
Turning on a second switching element in response to the first scan signal to electrically connect a gate terminal and a drain terminal of the driving transistor to supply the driving voltage to the first terminal of the capacitor; And
And turning on a third switching element in response to the first scan signal to supply the reference voltage to a second terminal of the capacitor. The method of claim 17,
The threshold voltage compensation step,
Turning off the first switching device according to the second emission control signal;
Supplying the data voltage to a source terminal of the driving transistor by turning on a fourth switching device according to the second scan signal;
The gate terminal and the drain terminal of the driving transistor are electrically connected to each other through the second switching element turned on by the first scan signal, thereby converting the sum voltage of the data voltage and the threshold voltage of the driving transistor into a first voltage of the capacitor. Supplying a terminal; And
And supplying the reference voltage to the second terminal of the capacitor through the third switching element turned on by the first scan signal. The method of claim 18,
And the second to fourth switching elements are turned off at the same time. The method of claim 18,
The program step,
The gate terminal of the driving transistor and the first terminal of the capacitor are connected to each other through the second to fourth switching elements turned off according to the first and second scan signals. Electrically connecting a second terminal to the light emitting element; And
And turning on a fifth switching element according to the first light emission control signal to connect a second terminal of the capacitor and a source terminal of the driving transistor. 21. The method of claim 20,
The light emitting step,
Supplying the driving voltage to a drain terminal of the driving transistor by turning on the first switching element according to the second emission control signal; And
And emitting the light emitting device by outputting the data current corresponding to the program voltage to the light emitting device through the driving transistor turned on according to the program voltage stored in the capacitor. Method of driving the display device.

Images