KR100555310B1 - Electro-luminescence display and its driving method - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electro-luminescence display device and a driving method thereof capable of preventing deterioration of a thin film transistor for driving an electro-luminescence cell and compensating a threshold voltage to prevent image degradation.

An electroluminescent display device according to an embodiment of the present invention is an electroluminescence cell connected between a supply voltage source and a base voltage source, and is connected between the electro-luminescence cell and the base voltage source and is connected to the electro-luminescence display device. A driving thin film transistor for controlling a current from the supply voltage source via the luminescence cell, a storage capacitor connected between the gate terminal of the driving thin film transistor and the base voltage source, and a supply voltage supplied from a data line. A first pass for supplying a reverse bias voltage to the driving thin film transistor, a second pass for compensating a threshold voltage of the driving thin film transistor and supplying the data voltage supplied from the data line to the storage capacitor; The ball via the electro-luminescence cell Such that the amount of current flowing through the control by the ground voltage source from the voltage source is characterized in that a third path for supplying the compensated data voltage on the storage capacitor to the driving thin film transistor.

Description

Electro-Luminescence Display Apparatus and Driving Method             

1 is a schematic view of a conventional electro-luminescence display.

FIG. 2 is a diagram illustrating the pixel cell of FIG. 1 in detail; FIG.

3A and 3B show amorphous silicon showing an atomic arrangement.

4 illustrates a pixel cell of another conventional electro-luminescence display.

FIG. 5 is a driving waveform diagram for driving the pixel cell shown in FIG. 4; FIG.

6 illustrates a pixel cell of an electro-luminescence display according to an exemplary embodiment of the present invention.

FIG. 7 is a driving waveform diagram for driving the pixel cell shown in FIG. 6;

FIG. 8 is a diagram illustrating a driving state of a pixel cell by driving waveforms in a section P1 illustrated in FIG. 7.

FIG. 9 is a diagram illustrating a driving state of a pixel cell by driving waveforms in a P2 section shown in FIG. 7;

FIG. 10 is a view illustrating a driving state of a pixel cell by driving waveforms in a period P3 shown in FIG. 7;

FIG. 11 is a view illustrating a driving state of a pixel cell by driving waveforms in a period P4 shown in FIG. 7;

FIG. 12 is a diagram illustrating a driving state of a pixel cell by driving waveforms in a section P5 illustrated in FIG. 7.

<Description of Symbols for Main Parts of Drawings>

20: electroluminescent panel 22: gate driver

24: data driver 26: gamma voltage generator

28, 58, 128: pixel cells 30, 60: cell driver

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent display device, and more particularly to an electroluminescence display that prevents deterioration of a thin film transistor for driving an electroluminescent cell and compensates a threshold voltage to prevent image degradation. A display device and a driving method thereof.

Recently, various flat panel display devices that can reduce weight and volume, which are disadvantages of cathode ray tubes, have emerged. Such flat panel displays include a liquid crystal display, a field emission display, a plasma display panel, and an electro-luminescence (hereinafter, EL). And a display device.

Among them, an EL display device is a self-luminous element that emits a phosphor by recombination of electrons and holes, and is classified roughly into an inorganic EL using an inorganic compound and an organic EL using an organic compound as the phosphor. Such EL display devices have many advantages such as low voltage driving, self-luminous, thin film type, wide viewing angle, fast response speed, and high contrast, and are expected to be the next generation display devices.

The organic EL element is usually composed of an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, and a hole injection layer stacked between a cathode and an anode. In such an organic EL device, when a predetermined voltage is applied between the anode and the cathode, electrons generated from the cathode move to the light emitting layer through the electron injection layer and the electron transport layer, and holes generated from the anode pass through the hole injection layer and the hole transport layer. Move toward the light emitting layer. Accordingly, the light emitting layer emits light by recombination of electrons and holes supplied from the electron transporting layer and the hole transporting layer.

An active matrix EL display device using such an organic EL element has an EL panel having pixels 28 arranged in regions defined by intersections of a gate line GL and a data line DL, as shown in FIG. 20, the gate driver 22 for driving the gate lines GL of the EL panel 20, the data driver 24 for driving the data lines DL of the EL panel 20, and the data driver. A gamma voltage generator 26 for supplying a plurality of gamma voltages to the 24 is provided.

The gate driver 22 sequentially drives the gate lines GL by supplying scan pulses to the gate lines GL.

The data driver 24 converts the digital data signal input from the outside into an analog data signal by using the gamma voltage from the gamma voltage generator 26. The data driver 24 supplies the analog data signal to the data lines DL every time a scan pulse is supplied.

Each of the pixels 28 receives a data signal from the data line DL when a scan pulse is supplied to the gate line GL, and generates light corresponding to the data signal.

To this end, each of the pixels 28 includes an EL cell OEL having an anode connected to a supply voltage source VDD and a cathode connected to the EL cell OEL as shown in FIG. 2, and a gate line GL. And a cell driver 30 connected to the data line DL and the ground voltage source VSS to drive the EL cell OEL.

The cell driver 30 includes a switching thin film transistor T1 in which a gate terminal is connected to the gate line GL, a source terminal is connected to the data line DL, and a drain terminal is connected to the first node N1, and the first A driving thin film transistor T2 in which a gate terminal is connected to the node N1, a drain terminal is connected to the base voltage source VSS, and a source terminal is connected to the EL cell EL, the base voltage source VSS and the first node ( A storage capacitor Cst connected between N1) is provided.

The switching thin film transistor T1 is turned on when a scan pulse is supplied to the gate line GL, and supplies the data signal supplied to the data line DL to the first node N1. The data signal supplied to the first node N1 is charged to the storage capacitor Cst and supplied to the gate terminal of the driving thin film transistor T2.

The driving thin film transistor T2 controls the amount of light emitted from the EL cell OEL by controlling the amount of current I supplied from the supply voltage source VDD via the EL cell OEL in response to the data signal supplied to the gate terminal. Done. In addition, even when the switching thin film transistor T1 is turned off, the driving thin film transistor T2 is kept on by the data signal charged in the storage capacitor Cst, and the EL is supplied until the data signal of the next frame is supplied. The amount of current I supplied from the supply voltage source VDD can be controlled via the cell OEL.

Here, the amount of current I flowing into the EL cell OEL may be expressed as in Equation (1).

Here, W represents the width of the driving thin film transistor T2, and L represents the length of the driving thin film transistor T2. In addition, Cox represents a capacitor value formed by an insulating film forming one layer when the driving thin film transistor T2 is manufactured. In addition, Vg2 represents the voltage Vth of the data signal input to the gate terminal of the driving thin film transistor T2, and Vth represents the threshold voltage Vth of the driving thin film transistor T2.

In Equation 1, W, L, Cox, and Vg2 may be kept constant regardless of the passage of time.

However, there is a problem in that the constant voltage of positive polarity (+) is supplied to the gate terminal of the driving thin film transistor T2 and the driving thin film transistor T2 is deteriorated due to the current driving. Due to the deterioration of the driving thin film transistor T2, the threshold voltage Vth of the driving thin film transistor T2 increases with time. As such, when the threshold voltage Vth of the driving thin film transistor T2 is increased, the amount of current flowing through the EL cell OEL cannot be precisely controlled (actually, the amount of current is decreased), so that the luminance is reduced and a desired image is obtained. There is a problem that is not displayed.

The conventional EL display device for compensating the threshold voltage Vth of the driving thin film transistor and preventing the degradation of the image quality of the EL cell OEL has a supply voltage source VDD and a ground voltage source VSS as shown in FIG. 3. Cell driver 60 connected between the EL cell OEL and the supply voltage source VDD and the EL cell OEL to control the current flowing from the supply voltage source VDD to the EL cell OEL. Equipped.

The cell driver 60 is a switch thin film transistor SW connected between the N-th gate line GLn and the data line DL, and a drive connected between the supply voltage source VDD and the EL cell OEL. Diode type formed in the form of a mirror so as to have the same characteristics as the driving thin film transistor T2 by being connected between the thin film transistor M2, the switching thin film transistor SW and the driving thin film transistor M2. Storage connected between the voltage source VDD and the first node N1 to which the mirror thin film transistor M1, the gate terminal of the diode-type mirror thin film transistor M1, and the gate terminal of the driving thin film transistor M2 are connected. The capacitor Cst, the first switch S1 connected between the N-th gate line GLn-1 and the diode-type mirror thin film transistor T1, the driving thin film transistor M2 and the EL cell ( The second switch S2 connected between the OEL and the N-th Soon as the gate terminal connected to line byte (GLn) and as well as having a third switch (S3) connected between the second switch (S2) and the EL cell (OEL).

In another conventional EL display device as described above, when the scan pulse is supplied to the N-th gate line GLn-1 as in the P1 section shown in FIG. 4, the first switch S1 is turned on. As a result, an initialization voltage Vinit lower than the base voltage VSS is supplied to the cathode terminal of the diode-type mirror thin film transistor M1. This initialization voltage Vinit is supplied on the first node N1. At this time, the data line DL is supplied with a voltage higher than the voltage VDD supplied from the supply voltage source VDD.

Then, as in the P2 period, when the scan pulse in the high state is supplied to the N-th gate line GLn-1, the cathode electrode of the diode-type mirror thin film transistor M1 is in a floating state. Accordingly, the cathode of the diode mirror thin film transistor M1 has a voltage smaller than the anode voltage by the threshold voltage Vth of the diode mirror thin film transistor M1.

Subsequently, when the negative scan pulse is supplied to the N-th gate line GLn as in the P3 section, the diode-type mirror thin film transistor M1 is turned on while the voltage of the cathode electrode is changed to the data signal Vdata. Has a voltage smaller than the threshold voltage Vth of the diode-type mirror thin film transistor M1. Therefore, the voltage on the first node N1 becomes the sum of the voltage Vdata of the data signal and the threshold voltage Vth of the diode-type mirror thin film transistor M1. Therefore, the voltage Vgs between the gate terminal and the source terminal of the driving thin film transistor M2 is always the sum of the voltage Vdata + Vth of the data signal Vdata and the threshold voltage Vth of the diode-type mirror thin film transistor M1. ) Is applied.

The other conventional EL display device as described above compensates the threshold voltage Vth of the driving thin film transistor M2 by using the threshold voltage Vth of the diode-type mirror thin film transistor M1. It is possible to prevent the deterioration in image quality due to the increase of the threshold voltage Vth.

However, this conventional EL display device has a threshold between the driving thin film transistor M2 and the diode mirror thin film transistor M1 when the diode mirror thin film transistor M1 is deteriorated to increase the threshold voltage Vth. The voltage will be different. Accordingly, another conventional EL display device has a problem in that a desired image cannot be displayed because the increased threshold voltage of the diode-type mirror thin film transistor M1 is compensated for the data voltage.

Further, in the other conventional EL display device, the driving thin film transistor M2 is supplied to the driving thin film transistor M2 at all times because the data voltage Vth + Vdata compensated for the threshold voltage of the diode-type mirror thin film transistor M1 is always supplied. There is a problem in that the threshold voltage Vth is increased to deteriorate and the luminance is decreased to display a desired image.

Accordingly, an object of the present invention is to provide an electro-luminescence display device and a method of driving the same, which can prevent deterioration of a thin film transistor for driving an electro-luminescence cell and compensate for a threshold voltage to prevent image degradation. It is.

It is also an object of the present invention to provide an electro-luminescence display device and a driving method thereof which improve the uniformity of the image quality and remove the afterimage.

In order to achieve the above object, an electro-luminescence display device according to an embodiment of the present invention, an electro-luminescence cell connected between a supply voltage source and a base voltage source, the electro-luminescence cell and the base voltage source A driving thin film transistor connected between and controlling a current from the supply voltage source via the electro-luminescence cell, a storage capacitor connected between a gate terminal of the driving thin film transistor and the base voltage source, and A first pass for supplying a reverse bias voltage to the driving thin film transistor using a supply voltage supplied from a line, and compensating a threshold voltage of the driving thin film transistor to the data voltage supplied from the data line to the storage capacitor. Second pass to supply and the electro-lumines And a third pass for supplying the compensated data voltage of the storage capacitor to the driving thin film transistor so that the amount of current flowing from the supply voltage source to the base voltage source is controlled via a sense cell.

The electro-luminescence display is configured to initialize the voltage stored in the storage capacitor to a voltage lower than the voltage supplied from the supply voltage source before the data voltage compensated by the second pass is stored in the storage capacitor. And a fourth pass and a fifth pass for stabilizing the compensated data voltage before the compensation data voltage stored in the storage capacitor by the third pass is supplied to the driving thin film transistor. .

The electro-luminescence display further includes first to fourth control signal supply lines for supplying first to fourth switching control signals for forming the first to fifth passes.

In the electroluminescent display, the first pass is connected between the data line and the second input terminal of the driving thin film transistor and is supplied to the data line in response to the first switching control signal. Is connected between a first thin film transistor for supplying a second input terminal of the driving thin film transistor, a first input terminal of the driving thin film transistor and the electro-luminescence cell, and responds to the second switching control signal. And a second thin film transistor for supplying a voltage from the supply voltage source via the electro-luminescence cell to the first input terminal of the driving thin film transistor.

In the electro-luminescence display, the second pass is connected between the first thin film transistor and the first input terminal and the gate terminal of the driving thin film transistor, and the driving is performed in response to the third switching control signal. And a third thin film transistor such that the thin film transistor is in the form of a diode.

In the electroluminescent display, the third pass is connected between the second thin film transistor, the second input terminal of the driving thin film transistor, and the base voltage source, and drives the driving in response to the fourth switching control signal. And a fourth thin film transistor for connecting the second input terminal of the thin film transistor to the base voltage source.

In the electro-luminescence display, the four paths include the first thin film transistor, the second thin film transistor, and the third thin film transistor that are turned on by each of the first to third switching control signals. Characterized in that.

In the electro-luminescence display, the fifth pass is the first thin film transistor turned on by the first switching control signal and the second turned off by the second to fourth switching control signals. And a fourth thin film transistor.

In the second pass of the electro-luminescence display, the threshold is reduced until the initialization voltage stored in the storage capacitor in the fourth pass is equal to the sum of the data voltage and the threshold voltage supplied to the data line. Voltage is compensated for the data voltage.

A method of driving an electro-luminescence display device according to an embodiment of the present invention is connected between an electro-luminescence cell connected between a supply voltage source and a base voltage source, and between the electro-luminescence cell and the base voltage source. An electroluminescent device having a driving thin film transistor for controlling a current from the supply voltage source via the electro-luminescent cell, and a storage capacitor connected between the gate terminal of the driving thin film transistor and the base voltage source. A driving method of a sense display device, comprising: a first step of supplying a reverse bias voltage to the driving thin film transistor using a supply voltage supplied from a data line; and the driving thin film transistor to a data voltage supplied from the data line. Compensating the threshold voltage of the storage capacitor And a third step of supplying the compensated data voltage of the storage capacitor to the driving thin film transistor so that the amount of current flowing from the supply voltage source to the base voltage source is controlled via the electro-luminescence cell. Characterized in that it comprises a.

The method of driving the electro-luminescence display device includes a fourth step of initializing a voltage stored in the storage capacitor to a voltage lower than a voltage supplied from the supply voltage source before the compensated data voltage is stored in the storage capacitor. And stabilizing the compensated data voltage before the compensation data voltage stored in the storage capacitor is supplied to the driving thin film transistor.

In the method of driving the electro-luminescence display device, the driving thin film transistor may be a diode type thin film transistor in the second and third steps.

In the method of driving the electro-luminescence display device, in the second step, the initialization voltage stored in the storage capacitor in the fourth step decreases until the sum of the data voltage and the threshold voltage supplied to the data line. As a result, the threshold voltage is compensated for by the data voltage.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 6 to 12.

Referring to FIG. 6, each of the pixel cells 128 of the electroluminescent display according to an exemplary embodiment of the present invention may include first to fourth control signal lines SGL1 to SGL4, a supply voltage source VDD, and a base voltage source. A driving thin film transistor connected between the EL cell OEL connected between the VSS and the EL cell OEL and the base voltage source VSS to control the amount of current flowing through the EL cell OEL; TFT), the first TFT T1 connected between the data line DL and the second input terminal of the driver TFT DT, the EL cell OEL, and the driver TFT DT. Of the second TFT (T2) connected between the first input terminals of the third TFT (T3) and the driving TFT (DT) connected between the first input terminal and the gate terminal of the driving TFT (DT). A fourth TFT (T4) connected between the second input terminal and the ground voltage source (VSS), a fourth TFT (T4) and a ground voltage source (VSS) connected between the gate terminal of the driving TFT (DT). The storage capacitor (Cst) The rain.

The anode terminal of the EL cell OEL is connected to the supply voltage source VDD, and the cathode terminal is connected to the first input terminal of the second TFT T2.

The source terminal of the first TFT (T1) is connected to the data line, the drain terminal is connected to the first node (N1) between the second input terminal of the driving TFT (DT) and the fourth TFT (T4), and the gate The terminal is connected to the first control signal line SGL1. The first TFT T1 applies the data voltage VD supplied from the data line DL in response to the first control signal from the first control signal line SGL1 to the second input terminal of the driving TFT DT. To feed.

The first input terminal of the second TFT T2 is connected to the cathode terminal of the EL cell OEL, the second input terminal is connected to the first input terminal of the driving TFT DT, and the gate terminal is second controlled. It is connected to the signal line SGL2. This second TFT T2 connects the cathode terminal of the EL cell OEL to the first input terminal of the driving TFT DT in accordance with the second control signal from the second control signal line SGL2.

The first input terminal of the third TFT (T3) is connected to the second node (N2) between the second input terminal of the second TFT (T2) and the first input terminal of the driving TFT (DT), and the second input The terminal is connected to the gate terminal of the driving TFT DT, and the gate terminal is connected to the third control signal line SGL3. The third TFT T3 connects the first input terminal and the gate terminal of the driving TFT DT according to the third control signal supplied from the third control signal line SGL3 to connect the driving TFT DT. It is intended to be a diode-type TFT.

The first input terminal of the fourth TFT T4 is connected to the first node N1, the second input terminal is connected to the base voltage source VSS, and the gate terminal is connected to the fourth control signal line SGL4. . The fourth TFT T4 connects the second input terminal of the driving TFT DT to the ground voltage source VSS in accordance with the fourth control signal supplied from the fourth control signal line SGL.

The storage capacitor Cst stores a voltage obtained by adding the data voltage VD supplied from the data line DL and the threshold voltage Vth of the driving TFT DT, and drives the driving TFT DT by the stored data voltage. Is maintained in the on state of the driving TFT DT until the data voltage of the next frame is supplied.

As described above, the first and second TFTs T1 and T2 form a first pass for supplying a reverse bias voltage to the driving TFT DT using the supply voltage VDD supplied from the data line DL. . In addition, the first and third TFTs T1 and T3 compensate the threshold voltage Vth of the driving TFT DT to the data voltage VD supplied from the data line DL and supply the same to the storage capacitor Cst. A second pass is formed. Further, the second and fourth TFTs T2 and T4 are compensated of the storage capacitor Cst such that the amount of current I flowing from the supply voltage source VDD to the base voltage source VSS is controlled via the EL cell OEL. A third pass for supplying the data voltage VD + Vth to the driving TFT DT is formed. In addition, the first to third TFTs T1, T2, and T3 store the voltage stored in the storage capacitor Cst before the data voltage VD + Vth compensated by the second pass is stored in the storage capacitor Cst. A fourth pass is formed to initialize to a voltage lower than the voltage supplied from the supply voltage source VDD. Then, the first TFT T1 has the compensated data voltage VD + Vth before the compensation data voltage VD + Vth stored in the storage capacitor Cst is supplied to the driving TFT DT by a third pass. To form a fifth pass for stabilization.

Specifically, the EL display device and the driving method thereof according to the embodiment of the present invention will be described with reference to FIGS. 7 and 6 as follows. First, the driving capacitor DT is applied to the storage capacitor Cst by switching the first and fourth TFTs T1 to T4 until the data voltage VD of the next frame is supplied. A voltage (~ VD) smaller than the data voltage (VD) for maintaining the on state is stored.

In the section P1 of FIG. 7, a control signal in a high state is supplied to the first and second control signal lines SGL1 and SGL2, and a control signal in a low state is supplied to the third and fourth control signal lines SGL3 and SGL4. do. Accordingly, since the first and second TFTs T1 and T2 of the pixel cell 128 are turned on, the supply voltage VDD supplied to the data line DL is determined as shown in FIG. 8. The supply voltage (~ VDD) supplied to the first node N1 connected to the second input terminal of the driving TFT DT via T1 and voltage-dropped by the EL cell OEL from the supply voltage source VDD. Is supplied to the first input terminal of the driving TFT DT. At this time, the gate terminal of the driving TFT DT is connected to the storage capacitor Cst. Accordingly, in the P1 section, the reverse bias voltage is supplied to the driving TFT DT by the voltage Vgs between the gate terminal and the source terminal of the driving TFT DT. Therefore, the driving TFT DT recovers the movement of the threshold voltage Vth by the reverse bias voltage. That is, the voltage stress applied to the driving TFT DT is eliminated by supplying the reverse bias voltage to the driving TFT DT.

Then, in the P2 section, the first and second control signals supplied to the first and second control signal lines SGL1 and SGL2 remain high and the third of the third is high on the third control signal line SGL3. While the control signal is supplied, the fourth control signal supplied to the fourth control signal line SGL4 is kept low. Accordingly, the first and second TFTs T1 and T2 are maintained in an ON state as shown in FIG. 9 while the third TFT T3 is supplied from the third control signal line SGL3. 3 Turned on by the control signal. For this reason, the driving TFT DT becomes a diode-type TFT due to the turn-on of the first to third TFTs T1, T2, and T3. Accordingly, the voltage supplied from the supply voltage source VDD is stored in the anode electrode of the diode-type driving TFT DT, that is, the storage capacitor Cst.

In the P2 section, the storage capacitor receives a voltage (~ VDD) supplied by dropping the voltage from the supply voltage source VDD by the threshold voltage Vth of the diode driving TFT DT via the diode driving TFT DT. By storing in (Cst) it is initialized the voltage of the storage capacitor (Cst).

Subsequently, in the P3 section, the first and second control signals supplied to the first and third control signal lines SGL1 and SGL3 remain high and the second control of the second control signal line SGL2 is low. The signal is supplied and the fourth control signal supplied to the fourth control signal line SGL4 is kept low. Accordingly, the first and third TFTs T1 and T3 are kept in the on state as shown in FIG. 10 and the second TFT T2 is turned off. Therefore, the voltage VDD supplied to the anode electrode of the diode-type driving TFT DT, that is, the storage capacitor Cst, is cut off from the power supply source VDD, and the data line (V1) is passed through the first TFT T1. The data voltage VD from DL is supplied to the cathode of the diode-type driving TFT DT. Accordingly, the voltage stored in the storage capacitor Cst by being turned on by the voltage dropping by the diode-type driving TFT DT and being stored in the storage capacitor Cst (~ VDD). (~ VDD) decreases until the voltage (VD + Vth) is added to the data voltage VD and the threshold voltage Vth of the diode-type driving TFT DT.

In the P3 section, the data voltage VD + Vth compensated for the threshold voltage Cst of the driving TFT DT is stored in the storage capacitor Cst.

Then, in the P4 section, the first control signal supplied to the first control signal line SGL1 is kept high while the second to fourth control signal lines SGL2, SGL3, and SGL4 are low. To the fourth control signal is supplied. Accordingly, the first TFT T1 is kept in the on state as shown in FIG. 11 while the second to fourth TFTs T2, T3, and T4 are turned off. Thus, as the third TFT T3 is turned off, the diode-type driving TFT DT is connected to the driving TFT DT in the form of a diode. Therefore, the compensated data voltage VD + Vth stored in the storage capacitor Cst supplied to the gate terminal of the driving TFT DT is stabilized.

Finally, the first and third control signals in the low state are supplied to the first and third control signal lines SGL1 and SGL3 in the P5 section, and the high and the first and third control signal lines SGL2 and SGL4 are supplied to the second and fourth control signal lines SGL2 and SGL4. The second and fourth control signals are supplied. Accordingly, the first and third TFTs T1 and T3 are turned off as shown in Fig. 12, and the second and fourth TFTs T2 and T4 are turned on. Thus, as the second and fourth TFTs T2 and T4 are turned on, the voltage VD + Vth stored in the storage capacitor Cst is supplied to the gate terminal of the driving TFT DT. The driving TFT DT is turned on by the data voltage VD + Vth compensated from the storage capacitor Cst supplied to the gate terminal, thereby supplying the supply voltage via the EL cell OEL and the second TFT T2. The current I supplied from the VDD is controlled to flow to the base voltage source VSS via the fourth TFT T4. At this time, the driving TFT DT controls the amount of current I flowing through the EL cell OEL by the data voltage VD + Vth whose threshold voltage Vth is compensated.

In the P5 section, the EL cell is turned on using the data voltage VD + Vth in which the threshold voltage Vth of the driving TFT DT stored in the storage capacitor Cst is compensated. By controlling the amount of current I flowing through the OEL, a decrease in luminance due to the threshold voltage Vth of the driving TFT DT is compensated for, thereby displaying a desired image.

As described above, the EL display device and the driving method thereof according to the embodiment of the present invention can display the desired image by repeating the P1 to P5 sections as described above.

As described above, the electro-luminescence display device and the driving method thereof according to the embodiment of the present invention provide a reverse bias voltage to the driving thin film transistor to prevent deterioration of the driving thin film transistor and at the same time the driving thin film transistor. By controlling the amount of current flowing through the electro-luminescence cell by compensating the threshold voltage of the data voltage to the data voltage, a desired image can be displayed by preventing a decrease in luminance.

In addition, the electro-luminescence display device and its driving method according to an embodiment of the present invention can improve the uniformity of the image quality by preventing the reduction of the brightness and improve the image quality by removing afterimages.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (13)

An electroluminescent cell connected between the supply voltage source and the base voltage source, A driving thin film transistor connected between the electro-luminescence cell and the base voltage source to control a current from the supply voltage source via the electro-luminescence cell; A storage capacitor connected between the gate terminal of the driving thin film transistor and the base voltage source; A first pass for supplying a reverse bias voltage to the driving thin film transistor using a supply voltage supplied from a data line, A second pass for compensating a threshold voltage of the driving thin film transistor and supplying the data voltage supplied from the data line to the storage capacitor; And a third pass for supplying the compensated data voltage of the storage capacitor to the driving thin film transistor so that the amount of current flowing from the supply voltage source to the base voltage source is controlled via the electro-luminescence cell. Electro-luminescence display. The method of claim 1, A fourth pass for initializing the voltage stored in the storage capacitor to a voltage lower than the voltage supplied from the supply voltage source before the data voltage compensated by the second pass is stored in the storage capacitor; And a fifth pass for stabilizing the compensated data voltage before the compensation data voltage stored in the storage capacitor by the third pass is supplied to the driving thin film transistor. Display. The method of claim 2, And first to fourth control signal supply lines for supplying first to fourth switching control signals for forming the first to fifth passes. The method of claim 3, wherein The first pass is, A supply voltage supplied between the data line and the second input terminal of the driving thin film transistor and supplied to the data line in response to the first switching control signal to supply the second input terminal of the driving thin film transistor. A first thin film transistor, The voltage from the supply voltage source connected between the first input terminal of the driving thin film transistor and the electro-luminescence cell and via the electro-luminescence cell in response to the second switching control signal; And a second thin film transistor supplied to the first input terminal of the thin film transistor for use. The method of claim 4, wherein The second pass, The first thin film transistor, And a third thin film transistor connected between the first input terminal and the gate terminal of the driving thin film transistor and allowing the driving thin film transistor to be in the form of a diode in response to the third switching control signal. Luminescence display. The method of claim 5, wherein The third pass, The second thin film transistor, And a fourth thin film transistor connected between the second input terminal of the driving thin film transistor and the base voltage source and connecting the second input terminal of the driving thin film transistor to the base voltage source in response to the fourth switching control signal. And an electroluminescent display device. The method of claim 6, The four passes, And the first thin film transistor, the second thin film transistor, and the third thin film transistor which are turned on by each of the first to third switching control signals. The method of claim 7, wherein The fifth pass is, The first thin film transistor turned on by the first switching control signal; And the second to fourth thin film transistors which are turned off by the second to fourth switching control signals. The method of claim 8, In the second pass, the threshold voltage is compensated to the data voltage by decreasing until the initialization voltage stored in the storage capacitor is equal to the sum of the data voltage and the threshold voltage supplied to the data line in the fourth pass. An electroluminescent display device characterized by the above-mentioned. An electro-luminescence cell connected between a supply voltage source and a base voltage source, and a current from the supply voltage source connected between the electro-luminescence cell and the base voltage source to control the current through the electro-luminescence cell; A driving method of an electro-luminescence display device comprising: a driving thin film transistor; and a storage capacitor connected between a gate terminal of the driving thin film transistor and the base voltage source. A first step of supplying a reverse bias voltage to the driving thin film transistor using a supply voltage supplied from a data line; A second step of compensating the threshold voltage of the driving thin film transistor to the data capacitor supplied from the data line and supplying the threshold voltage to the storage capacitor; And supplying the compensated data voltage of the storage capacitor to the driving thin film transistor such that the amount of current flowing from the supply voltage source to the base voltage source is controlled via the electro-luminescence cell. A method of driving an electroluminescent display. The method of claim 10, A fourth step of initializing the voltage stored in the storage capacitor to a voltage lower than the voltage supplied from the supply voltage source before the compensated data voltage is stored in the storage capacitor; And stabilizing the compensated data voltage before the compensation data voltage stored in the storage capacitor is supplied to the driving thin film transistor. The method of claim 11, And the driving thin film transistors are diode-type thin film transistors in the second and third steps. The method of claim 11, In the second step, the threshold voltage is compensated for the data voltage by decreasing until the initialization voltage stored in the storage capacitor is equal to the sum of the data voltage and the threshold voltage supplied to the data line in the fourth step. A method of driving an electroluminescent display device, characterized by the above-mentioned.

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