KR101763579B1 - Light emitting display device and driving method thereof - Google Patents

Abstract

The light emitting display according to the present invention includes a plurality of pixels; Each of the plurality of pixels includes a first switching element having a gate terminal connected to the second emission control line, a first terminal connected to the driving power supply, and a second terminal connected to the first node; A second switching element having a gate terminal connected to the first scanning line, a first terminal connected to the first node, and a second terminal connected to the second node; A capacitor having a first terminal connected to the second node and a second terminal connected to the third node; A third switching element having a gate terminal connected to the first scanning line, a first terminal connected to the reference power supply, and a second terminal connected to the third node; A light emitting element including an anode electrode connected to the third node, a cathode electrode connected to the base power supply, 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 the fourth node; A fourth switching element having a gate terminal connected to the second scanning 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 emission control line, a first terminal connected to the third node, and a second terminal connected to the fourth node.

Description

TECHNICAL FIELD [0001] The present invention relates to a light emitting display device,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting display, and more particularly, to a light emitting display capable of compensating for a threshold voltage of a driving transistor for driving a light emitting element to improve image quality and a driving method thereof.

In recent years, the importance of flat panel displays (LCDs) has increased with the development of multimedia. Various flat panel displays such as a liquid crystal display, a plasma display panel, a field emission display, and a light emitting display have been put into practical use. Of the flat panel displays, the light emitting display has a response speed of less than 1 ms and has a high response speed, low power consumption, and self-luminescence, so that it has no problem in viewing angle and is attracting attention as a next generation flat panel display.

2. Description of the Related Art Generally, a light emitting display device is a display device that emits light by electrically exciting a light emitting material, and is divided 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 showing a pixel structure of a general light emitting display device.

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

The switching transistor ST is switched in accordance with a scanning signal supplied to the scanning line SL to supply the driving transistor DT with the data voltage Vdata supplied to the data line DL.

The driving transistor DT is switched in accordance with 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 and stores a voltage corresponding to the data voltage Vdata supplied to the gate terminal of the driving transistor DT, And keeps the turn-on state of the transistor DT 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 and emits light by the data current idata supplied from the driving transistor DT. At this time, the data current idata flowing through the light emitting element OLED is supplied to the gate-source voltage Vgs of the driving transistor DT, the threshold voltage Vth of the driving transistor DT, and the data voltage Vdata .

The pixel of such a general light emitting display device controls the magnitude of the data current idata flowing from the driving power supply Vdd to the light emitting element OLED by switching the driving transistor DT according to the data voltage Vdata, (OLED), thereby displaying a predetermined image.

However, since the threshold voltage of the driving transistor DT included in each pixel is different from that of the conventional light emitting display device, even if the same data voltage Vdata is supplied to each pixel due to the threshold voltage deviation of the driving transistor DT The data current idata outputted from the driving transistor DT is different, and uniform image quality can not be realized. The threshold voltage deviation of the driving transistor M2 as described above can be further increased as the light emitting display device becomes larger in size, thereby causing deterioration of the image quality of the large area light emitting display device.

An object of the present invention is to provide a light emitting display device and a method of driving the same that can improve image quality by compensating a threshold voltage of a driving transistor for driving a light emitting element.

Another object of the present invention is to provide a light emitting display device and a method of driving the same that can prevent a current generated during a threshold voltage compensation of a driving transistor for driving a light emitting element from flowing to a light emitting element to improve a contrast ratio .

It is another object of the present invention to provide a light emitting display device and a method of driving the same that can improve the image quality by preventing the threshold voltage of the driving transistor for driving the light emitting element and the current change of the light emitting element according to the change of the base power supply, We will do it.

According to an aspect of the present invention, there is provided a light emitting display including a plurality of pixels formed in a pixel region defined by a data line, first and second scan lines, first and second emission control lines, Each of the plurality of pixels includes a first switching element having a gate terminal connected to the second emission control line, a first terminal connected to the driving power supply, and a second terminal connected to the 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 the second node; A capacitor having a first terminal connected to the second node and a second terminal connected to the third node; A third switching element having a gate terminal connected to the first scanning line, a first terminal connected to the reference power supply, and a second terminal connected to the third node; A light emitting element including an anode electrode connected to the third node, a cathode electrode connected to the base power supply, 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 the fourth node; A fourth switching element having a gate terminal connected to the second scanning 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 emission control line, a first terminal connected to the third node, and a second terminal connected to the fourth node.

And the capacitor is initialized to a driving voltage supplied from the driving power source during a period during which the first to third switching elements are turned on among the first to fifth switching elements.

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

And the second to fourth switching elements are simultaneously turned off.

And the capacitor stores a difference voltage between a gate terminal and a source terminal of the driving transistor during a period during which the fifth switching element is turned on from among the first through fifth switching elements.

The light emitting device may further include a light emitting element connected to the differential voltage output from the driving transistor that is turned on by the differential voltage stored in the capacitor during a period during which the first and fifth switching elements are turned on And emits light by a corresponding data current.

According to an aspect of the present invention, there is provided a light emitting display including a data line, first and second scan lines, a first and a second emission control lines, A pixel circuit for outputting a video signal; And a light emitting element that emits light by the data current outputted from the pixel circuit, wherein the pixel circuit includes a first scan signal supplied to the first scan line and a second scan signal supplied to the second emission control line An initialization unit for initializing a capacitor using different driving voltages and reference voltages in response to a signal; A data voltage supplied to the data line in response to the first scan signal and a second scan signal supplied to the second scan line and a sum voltage of the threshold voltage of the drive transistor and the data voltage using the reference voltage, A threshold voltage compensator for storing the voltage in a capacitor; A voltage programming unit for 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 emission control signal supplied to the first emission control line; And turning on the driving transistor in response to the program voltage stored in the capacitor in response to the first emission control signal and a second emission control signal supplied to the second emission control line, And a light emission control part for supplying a current to the light emitting element.

According to an aspect of the present invention, there is provided a method of driving a light emitting display including a data line, first and second scan lines, and first and second emission control lines, And a light emitting element which emits light by the data current outputted from the pixel circuit, wherein the first scanning signal supplied to the first scanning line and the first scanning signal supplied to the first scanning line An initialization step of initializing a capacitor using different driving voltages and reference voltages in response to a second emission control signal supplied to a second emission control line; A threshold voltage compensating step of storing in the capacitor a sum voltage of a data voltage supplied to the data line and a threshold voltage of the driving transistor in response to the first scanning signal and a second scanning signal supplied to the second scanning 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 emission control signal supplied to the first emission control line; And turning on the driving transistor in response to the program voltage stored in the capacitor in response to the first emission control signal and a second emission control signal supplied to the second emission control line, And a light emitting step of supplying a current to the light emitting element.

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 can be improved by compensating the threshold voltage of the driving transistor for driving the light emitting element.

Secondly, it is possible to prevent an undesired current, which is generated when the threshold voltage of the driving transistor DT is compensated, from flowing to the light emitting element, thereby improving the contrast ratio.

Thirdly, the image quality can be improved by preventing the change of the threshold voltage of the driving transistor and the change of the current of the light emitting element due to the change of the base voltage.

1 is a circuit diagram schematically showing a pixel structure of a general light emitting display device.
2 is a view schematically showing a light emitting display according to an embodiment of the present invention.
FIG. 3 is a view schematically showing the structure of a pixel according to the first embodiment of the present invention shown in FIG. 2. Referring to FIG.
4 is a driving waveform diagram for explaining a driving method of a light emitting display according to an embodiment of the present invention.
FIGS. 5A to 5D are diagrams showing driving states of the pixels according to the intervals shown in FIG.
FIG. 6 is a driving waveform diagram illustrating a driving method of a light emitting display according to another embodiment of the present invention. Referring to FIG.

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

2 is a view schematically showing a light emitting display according to an embodiment of the present invention.

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

The display panel 100 includes a plurality of pixels P (n) formed in pixel regions defined by m data lines DL to Dm, n scan lines S1 to Sn, and n emission control lines E1 to En, ).

Each of the plurality of pixels P is connected to the data line D1 according to a signal supplied to the first and second scan lines Si-1 and Si and the first and second emission control lines Ei and Ei + 1, The organic light emitting diode OLED emits light according to the data current corresponding to the data voltage supplied from the organic light emitting diode OLED. The first scan line Si-1 is defined as the (i-1) th scan line among the n scan lines S1 to Sn and the second scan line Si is defined as the n scan lines S1 to Sn. Th scan line. The first emission control line Ei is defined as the i-th emission control line among the n emission control lines E1 to En and the second emission control line Ei + 1 is defined as n emission control lines E1 To (i + 1) -th emission control line among the (i + 1) th emission control lines. A detailed description of each of the plurality of pixels P will be described later.

The timing controller 200 receives input data Ri / Gi / Bi of red, green, and blue input from an external system body (not shown) or a graphic card (not shown) to drive the display panel 100 And supplies the sorted data (R / G / B) 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 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. The timing control unit 300 generates a scan control signal SCS based on a timing synchronization signal TSS such as a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable DE, and a clock DCLK, And a data control signal DCS to control the driving timings 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 signals to the plurality of scan lines S1 to Sn. That is, the scan driver 310 sequentially shifts a scan signal having an ON state for two horizontal periods, in units of one horizontal interval, to each of the plurality of scan lines S1 to Sn in sequence. 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 are overlapped for one horizontal period.

The scan driver 310 may be turned on or off in accordance with the scan control signal SCS supplied from the timing controller 200 or the first and second scan signals of the on- And sequentially supplies control signals to the plurality of emission control lines E1 to En. That is, the scan driver 310 sequentially shifts the emission control signals, which are off during the 3 horizontal periods, in units of one horizontal interval and sequentially supplies the shifted emission control signals to the plurality of 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. On the other hand, the first emission control signal has an On state corresponding to the remaining horizontal periods except for the three horizontal periods overlapped with 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 supplied from the timing controller 200, And supplies the converted data voltages to the corresponding data lines D1 to Dm during one horizontal period in which the first and second scan signals are overlapped. That is, the data driver 320 sequentially latches the alignment data R / G / B for one horizontal line sequentially supplied in response to the data control signal DCS, The gamma voltage corresponding to the alignment data R / G / B is selected as a data voltage and supplied to the corresponding data lines D1 to Dm.

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

FIG. 3 is a view schematically showing the structure of a pixel according to the first embodiment of the present invention shown in FIG. 2. Referring to FIG.

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

The pixel circuit PC includes first through fifth switching elements SW1 through 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 the driving power supply, (For example, a drain terminal). The first switching device SW1 switches according to the second emission control signal and supplies the driving voltage Vdd supplied from the driving power source to the first node n1. That is, the first switching device SW1 is turned on only when the second emission control signal is in the 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 scanning line Si-1, a first terminal (for example, a source terminal) connected to the first node n1, and a second terminal n2 (E.g., a drain terminal) connected to the first terminal (e.g. The second switching element SW2 is switched according to the first scanning signal to electrically connect the first node n1 and the second node n2 connected to the gate terminals of the driving transistor DT. That is, the second switching device SW2 is turned on only when the first scan signal is in the On state, thereby electrically connecting the gate terminal and the drain terminal of the driving transistor DT, or the first switching device SW2 And supplies the driving voltage Vdd supplied to the first node n1 through the switch SW1 to the second node n2.

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 device 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 has a gate terminal connected to the first scan line Si-1, a first terminal (for example, a source terminal) connected to the reference power source, and a second terminal connected to the third node n3 And a second terminal (for example, a drain terminal). The third switching element SW3 is switched according to the first scanning 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 on, and supplies the reference voltage Vref to the third node n3. Here, the reference voltage Vref may be 0V, a base voltage, or a DC voltage having no voltage drop (e.g., a voltage between a base low voltage and a drive voltage).

The driving transistor DT has 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 in accordance with the switching of the second switching element SW2. The driving transistor DT is switched according to the program voltage stored in the capacitor C to output the data current corresponding to the program voltage to the fourth node n4.

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

The fifth switching element SW5 has 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, (E.g., a drain terminal) connected to the second terminal. The fifth switching device SW5 is turned on only when the first emission control signal is in an ON state, thereby electrically connecting the third node n3 and the fourth node n4.

The light emitting element OLED emits light by the data current supplied from the driving transistor DT. The light emitting device 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 supply, and a light emitting cell . Here, the light emitting cell may include a hole injecting layer / a hole transporting layer / a light emitting layer / an electron transporting layer / an electron injecting layer.

In the pixel P described above, the pixel circuit PC is initialized in accordance with the switching of each of the first to fifth switching elements SW1 to SW5 according to the first and second scanning signals, the first and second emission control signals, And turns on / off the light emitting device OLED through processes such as threshold voltage compensation, voltage programming, and light emission. Accordingly, the pixel circuit PC includes an initialization section, a threshold voltage compensating section, a voltage programming section, and a light emission control section, which are operated in accordance with the switching of the first to fifth switching elements SW1 to SW5 can see.

The initialization section 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 supplies the driving transistor DT in accordance with the first scanning signal in the On state, The driving voltage Vdd is supplied to the first terminal of the capacitor C and the reference voltage Vref is supplied to the second terminal of the capacitor C by electrically connecting the gate terminal and the drain terminal of the capacitor C, And the reference voltage Vref to initialize the capacitor C to the driving voltage Vdd. That is, the initializing unit may include first to third switching elements SW1 to SW5, which are turned on according to the first scan signal of the On state and the second light emission control signal of the first to fifth switching elements SW1 to SW5, SW2, and SW3 to initialize the capacitor C to the driving voltage Vdd.

The threshold voltage compensating unit compensates the data voltage and the threshold voltage of the driving transistor DT by using the data voltage supplied to the data line D1 and the reference voltage Vref in accordance with the first and second scanning signals in the On state, (C). That is, the threshold voltage compensation unit blocks the driving voltage Vdd supplied to the drain terminal of the driving transistor DT in accordance with the second emission control signal of the On state, Supplies the reference voltage Vref to the second terminal of the capacitor C in accordance with the first scan signal in the on state after supplying the data voltage to the source terminal of the drive transistor DT according to the first scan signal, The gate terminal of the driving transistor DT is electrically connected to the drain terminal of the driving transistor DT and the data voltage and the threshold voltage are supplied to the first terminal of the capacitor C through the driving transistor DT, It stores the voltage and the data voltage. As a result, the threshold voltage compensating unit includes the second to fourth switching elements SW2, SW4 turned on according to the first and second scanning signals of the On state among the first to fifth switching elements SW1 to SW5, SW3 and SW4 to store the data voltage and the threshold voltage of the driving transistor DT in the capacitor C. [

The voltage programming 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 in accordance with the first emission control signal in the On state. That is, the voltage programming unit blocks the driving voltage Vdd supplied to the drain terminal of the driving transistor DT in accordance with the second emission control signal of the On state, And the data line D1 is disconnected from the source terminal of the driving transistor DT according to the first scan signal of the on state and the reference voltage The gate terminal of the driving transistor DT is electrically connected to the first terminal of the capacitor C and the gate terminal of the driving transistor DT is electrically connected to the first terminal of the capacitor C, 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 in accordance with the first emission control signal in the ON state, Source terminal The program voltage corresponding to the voltage difference is stored in the capacitor (C). At this time, the program voltage becomes the sum of the data voltage and the threshold voltage of the driving transistor DT. As a result, the voltage programming unit uses only the fifth switching element SW5 turned on according to the first emission control signal of the On state among the first to fifth switching elements SW1 to SW5, In the capacitor C, the program voltage corresponding to the difference voltage between the gate terminal and the source terminal of the capacitor C.

The emission control unit turns on the driving transistor DT according to the program voltage stored in the capacitor C in response to the first and second emission control signals in the on state, (OLED) to emit the light emitting element OLED. That is, the light emission control section interrupts the electrical connection between the source terminal of the driving transistor DT and the data line D1 in accordance with the second scanning signal of the On state, The reference voltage Vref supplied to the second terminal of the capacitor C is cut off and the gate terminal of the driving transistor DT is electrically disconnected from the drain terminal of the driving transistor DT, (Vdd) to the drain terminal of the driving transistor (DT) in accordance with the second emission control signal in the On state, and in the 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 in accordance with the first emission control signal so that the driving transistor DT is turned on in accordance with 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 control unit turns on the first and fifth switching elements SW1, SW2 according to the first and second emission control signals of the On state among the first to fifth switching elements SW1 to SW5, SW5 to turn on the driving transistor DT according to the program voltage stored in the capacitor C to supply the data current corresponding to the program voltage to the light emitting element OLED to emit the light emitting element OLED. At this time, the data current supplied from the driving transistor DT to the light emitting element 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, Vth denotes the threshold voltage of the driving transistor And Vdata represents the data voltage.

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

FIG. 4 is a driving waveform diagram for explaining a method of driving a light emitting display according to an embodiment of the present invention, and FIGS. 5A to 5D are diagrams illustrating driving states of pixels according to intervals shown in FIG.

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

A method of driving a light emitting display according to an exemplary embodiment of the present invention includes driving a pixel P through an initializing period T1, a threshold voltage compensating period T2, a voltage programming period T3, and a light emitting period T4, .

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

Specifically, in the initialization period T1, the first switching device SW1 is turned on according to the second emission control signal ECSi + 1, which is supplied to the second emission control line Ei + 1, And supplies the driving voltage Vdd to the drain terminal of the first node n1, that is, the driving transistor DT. At the same time, in the initialization period T1, the second and third switching elements SW2 and SW3 are turned on according to the first scan signal SSi-1, which is supplied to the first scan line Si-1, 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 the reference voltage Vref is supplied to the first terminal To the third node n3, that is, the second terminal of the capacitor C. [ The voltage Vc of the capacitor C becomes higher than the voltage Vn2 of the second node n2 to which the driving voltage Vdd is supplied and the voltage Vn2 of the third node n3 to which the reference voltage Vref is supplied Vn3 to the driving voltage Vdd. 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.

4 and 5B, in the threshold voltage compensation period T2, the first and second scan lines Si and Si are turned on, which are supplied to the first and second scan lines Si-1 and Si, The data voltage Vdata supplied to the data line D1 and the threshold voltage Vth of the driving transistor DT are stored in 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 SW1 to SW5 turned on according to the first and second scanning signals of the On state, The data voltage Vdata and the threshold voltage Vth of the driving transistor DT are stored in the capacitor C using the switches SW2, SW3 and SW4.

Specifically, in the threshold voltage compensation period T2, the first switching device SW1 is turned on in accordance with the second emission control signal ECSi + 1 in the off state supplied to the second emission control line Ei + 1 The fourth switching element SW4 is turned on according to the second scan signal SSi which is turned on and supplied to the second scan line Si, (n3), that is, 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 of the On state supplied to the first scan line Si- The gate terminal and the drain terminal of the driving transistor DT are electrically connected to each other through the second node n2, that is, the capacitor C, by electrically connecting the data voltage Vdata and the threshold voltage Vth of the driving transistor DT, And the third node n3, that is, the capacitor (n3), through the third switching element SW3, which is on by the first scanning signal SSi-1 in the On state, C to the second terminal of the second switch SW1. The voltage Vc of the capacitor C is set to the voltage Vn2 of the second node n2 to which the data voltage Vdata and the threshold voltage Vth of the driving transistor DT are supplied and the reference voltage Vref, (Vdata + Vth) of the data voltage (Vdata) and the threshold voltage (Vth) of the driving transistor (DT) by the voltage (Vn3) of the third node (n3) supplied. 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 supplied to the second scan line Si is supplied to the off state.

4 and 5C, in the voltage programming period T3, in response to the first emission control signal ECSi supplied to the first emission control line Ei, the gate voltage of the driving transistor DT The program voltage corresponding to the difference voltage Vgs between the source voltage Vn2 and the source voltage Vn3 is stored in the capacitor C. That is, in the voltage programming period T3, only the fifth switching element SW5 turned on according to the first emission control signal of the On state among the first to fifth switching elements SW1 to SW5 is driven 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.

Specifically, in the voltage programming period T3, the first and second scan signals SSi-1 and SSi, which are 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 through fourth switching elements SW2, SW3 and SW4 which are turned off and the second terminal of the capacitor C is connected And is connected to the anode electrode of the light emitting element OLED. At the same time, in the voltage programming period T3, the fifth switching device SW5 is turned on according to the first emission control signal ECSi which is supplied to the first emission control line Ei, C to the source terminal of the driving transistor DT. 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 programming 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.

4 and 5D, in the light emission period T4, the first and second light emission control lines E1 and Ei + 1, which are supplied to the first and second emission control lines Ei and Ei + 1, In response to the signals ECSi and ECSi + 1, the driving transistor DT is turned on in accordance with the program voltage stored in the capacitor C to supply the data current idata corresponding to the program voltage to the light emitting element OLED . That is, in the light emission period T4, the first and second switching elements SW1 to SW5 are turned on according to the first and second emission control signals ECSi and ECSi + 1, respectively, 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 element OLED Thereby causing the light emitting element OLED to emit light.

Specifically, in the light emission period T4, the source terminal of the driving transistor DT and the gate of the data line D1 are electrically connected to the second scan line Si in accordance with the second scan signal SSi, Thereby blocking the connection. At the same time, in the light emission period T4, the reference voltage Vs 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- The gate terminal of the driving transistor DT is electrically disconnected from the drain terminal and the gate terminal of the driving transistor DT is electrically connected to the first terminal of the capacitor C. At the same time, according to the second emission control signal ECSi + 1 of the ON state supplied to the second emission control line Ei + 1 in the emission period T4, The source terminal of the driving transistor DT is supplied to the second emission control line Ei of the capacitor C in accordance with the first emission control signal ECSi of the ON state supplied to the first emission control line Ei, Terminal and 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 in accordance with the stored program voltage, and the turned-on driving transistor DT, as shown in Equation 1, (Idata) corresponding to the program voltage to the light emitting element OLED by using the data voltage Vdd. Accordingly, the light emitting device OLED emits light (On) 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 period T1 of the next frame.

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

In addition, the present invention can prevent undesired currents generated during the threshold voltage compensation of the driving transistor DT driving the light emitting device OLED from flowing to the light emitting device OLED, thereby improving the contrast ratio. That is, the present invention supplies the reference voltage Vref to the anode electrode of the light emitting device OLED during the initialization period T1 and the voltage compensation period T2, thereby instantaneously supplying the reference voltage Vref during the initialization period T1 and the voltage compensation period T2. The generated current can prevent a current glitch phenomenon that flows in the light emitting device OLED, thereby improving the contrast ratio.

The present invention is characterized in that the current change of the light emitting device OLED due to the threshold voltage change of the driving transistor DT is small and the current change of the light emitting device OLED due to the base voltage Vss is small, .

Meanwhile, in the light emitting display device and the driving method thereof according to the embodiment of the present invention, a scan signal having an ON state for two horizontal periods is shifted in units of one horizontal interval, and the plurality of scan lines S1 to Sn The scanning signal SSi-1 supplied to the previous single scan line Si-1 of each pixel P is used.

However, in the light emitting display device and the driving method thereof according to another embodiment of the present invention, one scanning line is added for each pixel P, and as shown in FIG. 6, The first scan signal SS1 having an ON state for two horizontal periods is supplied to the first scan line SS1 and the first scan signal SS1 is shifted from the first scan signal SS1 to the second scan line among the two scan lines, And supplies a second scan signal SS2 having an ON state overlapping the scan signal SS1 for one horizontal period. Accordingly, the light emitting display according to another embodiment of the present invention and the driving method thereof may further include the threshold voltage compensation period T2 and the light emission period T3 (T3) using the first and second scan signals SS1 and SS2, And supplies the first and second scan signals SSi and SSi + 1 in the Off state to the first and second scan lines during the period between the scan signal ) Of the parasitic capacitor can be minimized.

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 controller
300: panel driver 310: scan driver
320:

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;
Wherein each of the plurality of pixels comprises:
A first switching element having a gate terminal connected to the second emission control line, a first terminal connected to the driving power supply, and a second terminal connected to the 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 the second node;
A capacitor having a first terminal connected to the second node and a second terminal connected to the third node;
A third switching element having a gate terminal connected to the first scanning line, a first terminal connected to the reference power supply, and a second terminal connected to the third node;
A light emitting element including an anode electrode connected to the third node, a cathode electrode connected to the base power supply, 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 the fourth node;
A fourth switching element having a gate terminal connected to the second scanning 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 emission control line, a first terminal connected to the third node, and a second terminal connected to the fourth node,
And the difference voltage between the gate terminal and the source terminal of the driving transistor is stored during a period in which only the fifth switching element is turned on. The method according to claim 1,
Wherein the capacitor is initialized to a driving voltage supplied from the driving power source during a period during which the first to third switching elements are turned on among the first to fifth switching elements. . The method according to claim 1,
Wherein the capacitor stores a sum voltage of a threshold voltage of the driving transistor and a data voltage supplied to the data line during a period during which the second to fourth switching elements are turned on among the first to fifth switching elements . The method of claim 3,
And the second to fourth switching elements are simultaneously turned off. delete The method according to claim 1,
The light emitting device may further include a light emitting element connected to the differential voltage output from the driving transistor that is turned on by the differential voltage stored in the capacitor during a period during which the first and fifth switching elements are turned on And emits light by a corresponding data current. delete delete delete delete delete A pixel circuit which is formed in a pixel region defined by a data line, first and second scan lines, first and second emission control lines and outputs a data current through a driving transistor, And a light emitting element which emits light,
The pixel circuit includes:
A first switching element having a gate terminal connected to the second emission control line, a first terminal connected to the driving power supply, and a second terminal connected to the 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 the second node;
A capacitor having a first terminal connected to the second node and a second terminal connected to the third node;
A third switching element having a gate terminal connected to the first scanning line, a first terminal connected to the reference power supply, and a second terminal connected to the third node;
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 the fourth node;
A fourth switching element having a gate terminal connected to the second scanning 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 emission control line, a first terminal connected to the third node, and a second terminal connected to the fourth node, ,
An initialization step of initializing the 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 compensating step of storing in the capacitor a sum voltage of a data voltage supplied to the data line and a threshold voltage of the driving transistor in response to the first scanning signal and a second scanning signal supplied to the second scanning 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 emission control signal supplied to the first emission control line; And
In response to the first emission control signal and a second emission control signal supplied to the second emission control line, the drive transistor is turned on in accordance with the program voltage stored in the capacitor to turn on the data current And a light emission step of supplying light to the light emitting element,
Wherein during the programming step, only the fifth switching element is turned on to store a difference voltage between a gate terminal and a source terminal of the driving transistor. 13. The method of claim 12,
In the initialization step,
Supplying the driving voltage to the drain terminal of the driving transistor in response to the second emission control signal; And
A gate terminal of the driving transistor is electrically connected to a drain terminal of the driving transistor in response to the first scanning signal to supply the driving voltage to the first terminal of the capacitor and the reference voltage to the second terminal of the capacitor, And the driving voltage is reset to the driving voltage. 13. The method of claim 12,
Wherein the step of compensating the threshold voltage comprises:
Interrupting the driving voltage supplied to the drain terminal of the driving transistor in response to the second emission control signal and supplying the data voltage to the source terminal of the driving transistor in response to the second scanning signal; And
Wherein 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 drive transistor are electrically connected to each other, And supplying a sum voltage of the threshold voltage of the transistor and the data voltage. 15. The method of claim 14,
Wherein the program step comprises:
In response to the second emission control signal, the driving voltage supplied to the drain terminal of the driving transistor is cut off and the source terminal of the driving transistor is electrically disconnected from the data line in response to the second scanning signal ;
The reference voltage supplied to the second terminal of the capacitor is cut off in response to the first scan signal and the gate terminal of the drive transistor is electrically disconnected from the drain terminal, To the first terminal of the first terminal; And
Wherein the source terminal of the driving transistor is electrically connected to the second terminal of the capacitor and the light emitting element in response to the first emission control signal. 15. The method of claim 14,
Wherein the light emitting step supplies the driving voltage to the drain terminal of the driving transistor in response to the second emission control signal and controls the source terminal of the driving transistor to the second terminal of the capacitor in response to the first emission control signal And the light emitting element is electrically connected to the light emitting element. 13. The method of claim 12,
In the initialization step,
Supplying a driving voltage to a drain terminal of the driving transistor by turning on a first switching element in response to the second emission control signal;
Supplying a driving voltage to the first terminal of the capacitor by electrically connecting a gate terminal and a drain terminal of the driving transistor by turning on a second switching element in response to the first scanning signal; And
And turning on the third switching element in response to the first scan signal to supply the reference voltage to the second terminal of the capacitor. 18. The method of claim 17,
Wherein the step of compensating the threshold voltage comprises:
Turning off the first switching device according to the second emission control signal;
Turning on a fourth switching element according to the second scan signal to supply the data voltage to a source terminal of the driving transistor;
A gate terminal and a drain terminal of the driving transistor are electrically connected to each other through the second switching element turned on by the first scanning signal so that a sum voltage of the data voltage and a threshold voltage of the driving transistor is supplied to the first To a terminal; And
And supplying the reference voltage to the second terminal of the capacitor through the third switching device turned on by the first scan signal. 19. The method of claim 18,
And the second to fourth switching elements are simultaneously turned off. 19. The method of claim 18,
Wherein the program step comprises:
The gate terminal of the driving transistor and the first terminal of the capacitor are connected through the second to fourth switching elements turned off according to the first and second scanning signals, Electrically connecting the second terminal to the light emitting element; And
And turning on the fifth switching element according to the first emission control signal to connect the second terminal of the capacitor and the source terminal of the driving transistor. 21. The method of claim 20,
The light-
Turning on the first switching element according to the second emission control signal to supply the driving voltage to the drain terminal of the driving transistor; And
And outputting the data current corresponding to the program voltage through the driving transistor turned on according to the program voltage stored in the capacitor to the light emitting element to cause the light emitting element to emit light A method of driving a display device.

Images