KR20050109164A - Light emitting display - Google Patents

Abstract

In an organic EL display device, a threshold voltage of a driving transistor is connected to a first capacitor by diode-connecting a driving transistor in response to a previous selection signal and connecting a second terminal of a first capacitor having a first end connected to a gate of the driving transistor to a power supply. Save it. Next, the second terminal of the first capacitor is changed to the data voltage in response to the current selection signal. In this case, since the threshold voltage stored in the first capacitor may be changed by the kickback, the size of the first capacitor is larger than that of the second capacitor to reduce the influence of the kickback, thereby storing the threshold voltage as much as possible.

Description

Light emitting display device {LIGHT EMITTING DISPLAY}

The present invention relates to a light emitting display device, and more particularly, to an organic electroluminescence (EL) display device.

In general, an organic EL display device is a display device for electrically exciting a fluorescent organic compound to emit light, and is capable of driving an organic light emitting cell arranged in a matrix to represent an image. Such an organic light emitting cell has a diode characteristic and is called an organic light emitting diode (OLED) and has a structure of an anode electrode layer, an organic thin film, and a cathode electrode layer. In addition, holes and electrons injected through the anode electrode and the cathode electrode are combined in the organic thin film to emit light. As such, the amount of light emitted from the organic light emitting cell varies depending on the amount of electrons and holes injected, that is, the magnitude of the applied current.

The organic light emitting cell may be driven by a simple matrix method and an active matrix method using a thin film transistor (TFT). The active driving method is divided into a voltage programming method and a current programming method according to the type of a signal applied to write and maintain a voltage in a capacitor.

FIG. 1 is a pixel circuit of a voltage write type organic EL display device, and typically shows a pixel circuit connected to an m th data line Dm and an n th scan line Sn of a plurality of pixel circuits.

As shown in Fig. 1, the transistor M1 is connected to the organic EL element OLED to supply a current for emitting light. The amount of current in the transistor M1 is controlled by the data voltage applied through the switching transistor M2. At this time, a capacitor Cst for maintaining the applied voltage for a predetermined period is connected between the source and the gate of the transistor M2. The gate of the transistor M2 is connected to the scan line Sn and the source is connected to the data line Dm.

Referring to the operation of the conventional pixel circuit, when the transistor M2 is turned on by the selection signal applied to the gate of the transistor M2, the data voltage is transferred to the gate of the driving transistor M1 through the data line Dm. Is approved. In response to the data voltage applied to the gate, a current flows through the transistor M1 to the organic EL element OLED to emit light. At this time, the current flowing through the organic EL element OLED is represented by Equation 1 below.

Where I _OLED is the current flowing through the organic EL element OLED, Vgs is the voltage between the gate and the source of the transistor M1, Vth is the threshold voltage of the transistor M1, Vdata is the data voltage, and β is the transistor M1. It represents a constant value determined by the size and characteristics of.

As shown in Equation 1, according to the pixel circuit shown in FIG. 1, a current corresponding to the applied data voltage Vdata is supplied to the organic EL element OLED, and the organic EL element OLED corresponds to the supplied current. ) Will emit light.

However, such a pixel circuit of the conventional voltage writing method has a problem in that it is difficult to obtain a high gradation due to the variation in the threshold voltage Vth of the thin film transistor generated for each pixel due to the nonuniformity of the manufacturing process. For example, when driving a transistor of a pixel at 3V, a voltage must be applied to the gate of the thin film transistor at intervals of about 12 mV (= 3 V / 256) in order to express an 8 bit 256 gray level. When the variation in the threshold voltage of the thin film transistor is 100 kΩ, it is difficult to express a high gray scale.

An object of the present invention is to provide a light emitting display device capable of expressing uniform luminance by compensating for variation in threshold voltage of a driving transistor.

According to an aspect of the present invention, there is provided a light emitting display device including a plurality of data lines for transmitting a data voltage, a plurality of scan lines for transmitting a selection signal, and a plurality of pixel circuits respectively connected to the scan lines and the data lines. . In the pixel circuit of the present invention, a current corresponding to a voltage between a control electrode and a second main electrode flows through a first main electrode, and the second main electrode corresponds to a transistor connected to a first power source, and corresponding to a magnitude of an applied current. A light emitting device for emitting light, a first capacitor having a first end connected to the control electrode, and a second capacitor connected between a second power supply and a second end of the first capacitor and having a smaller capacitance than the first capacitor. It includes. The pixel circuit of the present invention includes: a first period in which the transistor is diode-connected and the second end of the first capacitor is electrically connected to a second power source in a state in which the first main electrode and the light emitting element are electrically cut off; In order of applying the data voltage to the second terminal of the first capacitor, the voltage is operated in the order of the second period.

According to an embodiment of the present invention, the first level selection signal is applied to the immediately preceding scan line in the first period, and the selection signal of the first level is applied to the current scan line in the second period.

According to another embodiment of the invention, the pixel circuit of the present invention, the first switching element for diode-connecting the transistor in response to the selection signal of the first level of the immediately preceding scan line, the second end of the first capacitor and the first A second switching element connected between a second power source and turned on in response to the selection signal of the first level of the immediately preceding scan line, and converting the data voltage in response to the selection signal of the first level of the current scan line; It further comprises a third switching device for transferring to the second stage of.

According to another embodiment of the present invention, the pixel circuit of the present invention further includes a fourth switching element connected between the first main electrode and the transistor, wherein the fourth switching element is turned off in the first period. And is turned on in the second period.

According to another embodiment of the present invention, the pixel circuit of the present invention further includes a fourth switching element connected between the first main electrode and the transistor, wherein the fourth switching element comprises the first period and the second period. Turned off in the period and turned on after the second period.

According to another feature of the invention, a plurality of data lines for transmitting a data voltage, a plurality of scan lines for transmitting a selection signal and a plurality of pixel circuits respectively connected to the scan line and the data line, the pixel of at least two colors A light emitting display device each having a circuit is provided. In the pixel circuit of the present invention, a current corresponding to a voltage between a control electrode and a second main electrode flows through a first main electrode, and the second main electrode corresponds to a transistor connected to a first power source, and corresponding to a magnitude of an applied current. A light emitting element for emitting light, a first switching element for diode-connecting the transistor in a first period before the selection signal from the scanning line becomes a first level, a first capacitor having a first end connected to the control electrode, and A second capacitor connected between a second power supply and a second end of the first capacitor and having a smaller capacitance than the first capacitor, a second switching connecting the second end of the first capacitor and a second power supply in the first period A device and a data voltage from the data line in response to the selection signal of the first level from the scan line in a second period of time; And a third switching device passing to.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification. When a part is connected to another part, this includes not only a directly connected part but also an electrically connected part with another element in between.

A light emitting display device according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings. In the embodiment of the present invention, an organic EL display device using electroluminescence of an organic material is described as an example of a light emitting display device.

2 schematically illustrates a light emitting display device according to an embodiment of the present invention.

As shown in FIG. 2, the light emitting display device according to the exemplary embodiment of the present invention includes a display panel 100, a scan driver 200, and a data driver 300.

The display panel 100 includes a plurality of data lines D1 to Dm extending in the column direction, a plurality of selection scan lines S1 to Sn extending in the row direction, and a plurality of pixel circuits 10. The data lines D1 to Dm transfer the data voltage representing the image to the pixel circuit 10, and the selection scan lines S1-Sn transfer the selection signal to the pixel circuit 10. The pixel circuit 10 is formed in a pixel region defined by two adjacent data lines D1 to Dm and two adjacent selection scan lines S1 to Sn.

The scan driver 200 sequentially applies a selection signal to the scan lines S1 to Sn, and the data driver 300 simultaneously applies a data voltage to the data lines D1 to Dm.

The scan driver 200 and / or the data driver 300 may be directly mounted on the glass substrate in the form of an integrated circuit. Alternatively, these driving units 200 and / or 300 may be formed on the glass substrate with the same layers as the layers forming channels of the selection scan lines S1 to Sm, the data lines D _{1 to} D _n , and the transistors. Alternatively, the driving units 200 and / or 300 may be formed on a substrate separate from the glass substrate, and the substrates may be electrically connected to the glass substrate. Also, a tape carrier package (TCP) and an FPC (attached to the glass substrate may be electrically connected. It may be mounted in the form of a chip in a flexible printed circuit (TAB) or tape automatic bonding (TAB).

Hereinafter, a pixel circuit according to a first exemplary embodiment of the present invention will be described in detail with reference to FIGS. 3 and 4.

3 is a diagram illustrating a pixel circuit according to a first exemplary embodiment of the present invention, and FIG. 4 is a driving timing diagram of the pixel circuit of FIG. 3.

In FIG. 3, only the furnace circuit connected to the m-th data line Dm and the n-th scan line Sn is illustrated for convenience of description. In Fig. 4, the selection signals applied to the nth scan line Sn and the (n-1) th scan line Sn-1 are represented by scan [n] and scan [n-1], respectively.

On the other hand, when the term for the scan line is defined, a scan line that transmits a selection signal for operating a transistor connected to the data line and the selection scan line so as to transfer the data voltage is referred to as a "current scan line" and transmits the selection signal immediately before the current selection signal. The scan line is referred to as the "last scan line".

As shown in FIG. 3, the pixel circuit according to the first embodiment of the present invention includes five transistors M1 to M5, a storage capacitor Cst, a threshold voltage compensation capacitor Cvth, and an organic EL element OLED. ). In FIG. 3, transistors M1 to M4 are shown as p-channel field effect transistors, and transistor M5 is shown as n-channel field effect transistors. The transistor has two main electrodes (drain electrode and source electrode) and one control electrode (gate electrode).

The transistor M1 is a driving transistor for driving the organic EL element OLED, and is connected between the power supply VDD for supplying a high level power supply voltage and the transistor M5, and according to the voltage applied to the gate, The current flowing through the organic EL element OLED is controlled through M5). The transistor M2 is connected between the gate and the drain of the transistor M1, and diodes transistor M1 are responsive to the low level select signal scan [n-1] from the immediately preceding scan line Sn-1. Connect in the form.

The first electrode A of the capacitor Cvth is connected to the gate of the driving transistor M1, and the capacitor Cst and the transistor M4 are connected between the second electrode B of the capacitor Cvth and the power supply VDD. Are connected in parallel. The transistor M4 connects the second electrode B of the capacitor Cvth to the power supply VDD in response to the low level select signal scan [n-1] from the previous scan line Sn-1. The transistor M3 is a switching transistor connected between the data line D _m and the second electrode B of the capacitor Cvth. The transistor M3 is connected to the low level select signal scan [n] from the current scan line Sn. In response, the data voltage from the data line Dm is transferred to the second electrode B of the capacitor Cvth.

The transistor M5 is connected between the drain of the transistor M1 and the anode of the organic EL element OLED, in response to the low level select signal scan [n-1] from the immediately preceding scan line Sn-1. The drain of the transistor M1 and the organic EL element OLED are electrically cut off, and the transistor M1 is disconnected from the transistor M1 in response to the high-level selection signal scan [n-1] from the immediately preceding scan line Sn-1. The current is transmitted to the organic EL element OLED.

The organic EL element OLED emits light corresponding to the input current. The voltage VSS connected to the cathode of the organic EL element OLED is a voltage having a lower level than the voltage VDD, and a ground voltage, a negative voltage, and the like may be used.

Hereinafter, an operation of the pixel circuit according to the exemplary embodiment of the present invention will be described with reference to FIG. 4.

First, when the selection signal scan [n-1] of the previous scan line Sn-1 becomes low in the T1 period, the transistor M2 is turned on so that the driving transistor M1 is connected in the form of a diode. Therefore, the voltage between the gate and the source of the driving transistor M1 is changed until the threshold voltage Vth of the driving transistor M1 becomes. At this time, since the source of the transistor M1 is connected to the power supply VDD, the gate of the transistor M1, that is, the voltage of the first electrode A of the capacitor Cvth becomes (VDD + Vth). Since the transistor M4 is turned on by the low level select signal scan [n-1], the second electrode B of the capacitor Cvth is connected to the power source VDD. The voltage of the two electrodes B becomes the power supply voltage VDD. Therefore, the threshold voltage Vth is stored in the capacitor Cvth. In addition, since the n-channel transistor M5 is turned off by the low level select signal scan [n-1], the current of the transistor M1 is prevented from flowing to the organic EL element OLED.

Next, when the selection signal scan [n-1) of the immediately preceding scan line Sn-1 becomes high level and the selection signal scan [n] of the current scan line Sn becomes low level in the period T2, the transistor M3. , M4 is turned on and transistors M2 and M4 are turned off. The data voltage Vdata is transferred from the data line Dm to the transistor M3. Then, the data voltage Vdata is transferred to the second electrode B of the capacitor Cvth, so that the voltage of the first electrode A of the capacitor Cvth is boosted by the difference between the data voltage Vdata and the power supply voltage VDD. do. Accordingly, the gate of the transistor M1, that is, the voltage Vg of the first electrode A of the capacitor Cvth is represented by Equation 2, and the current I _OLED flowing through the drain of the transistor M1 is represented by Equation 3 Become together. Since the transistor M5 is turned on by the high level selection signal scan [n-1], this current I _OLED is transmitted to the organic EL element OLED to emit light. In addition, since the voltage Vgs between the gate and the source of the transistor M1 is stored in the capacitors Cvth and Cst, the selection signal scan [n-1] of the previous scan line Sn-1 even after the T2 period is applied. During the high level, the transistor M1 supplies a current as shown in Equation 3 to the organic EL element OLED. That is, the capacitor Cst serves to store the data voltage together with the threshold voltage Vth compensation capacitor Cvth.

Here, Vgs represents a voltage between the gate and the source of the transistor M1, Vth represents a threshold voltage of the transistor M1, Vdata represents a data voltage, and β represents a constant value.

In Equation 3, the current I _OLED transmitted to the organic EL element OLED is determined by the power supply voltage VDD and the data voltage Vdata regardless of the threshold voltage Vth of the driving transistor M1. do. Therefore, even if the threshold voltages Vth of the driving transistors M1 of the pixel circuits 10 of the display panel 100 are different from each other, in the first embodiment, the deviation of the threshold voltage Vth is compensated by the capacitor Cvth. The current supplied to the organic EL element OLED becomes constant. That is, according to the pixel circuit illustrated in the embodiment of the present invention, it is possible to solve the luminance unbalance problem caused by the variation of the threshold voltage of the thin film transistor according to the position between each subpixel.

In general, the power voltages VDD of the plurality of pixel circuits 10 formed on the display panel are supplied by one or two power lines. Of course, depending on the structure of the panel, more than one power wiring can be used. However, since the current flowing in the driving transistor M1 flows through the power supply wiring for supplying the power supply voltage VDD and a plurality of pixel circuits are connected to one power supply wiring, a large current flows in one power supply wiring. Therefore, a large voltage drop occurs in the power line due to such a large current, and the magnitude of the power voltage VDD supplied from the power line may vary depending on the position of the pixel circuit. Referring to Equation 3, such a difference in power supply voltage VDD is a difference in current supplied to the organic EL element OLED, and thus, unevenness in luminance may occur depending on the position of the pixel circuit. Hereinafter, an embodiment in which luminance unevenness due to voltage drop in a power supply wiring can be prevented will be described with reference to FIG. 5.

5 is a diagram illustrating a pixel circuit according to a second exemplary embodiment of the present invention.

As shown in FIG. 5, the pixel circuit according to the second exemplary embodiment of the present invention except for the fact that the source of the transistor M4 is connected to a compensation power supply Vsus different from the power supply voltage VDD. It has the same structure as the pixel circuit of three. That is, the transistor M4 is connected between the compensation power supply Vsus and the second electrode B of the capacitor Cvth, and the low level selection signal scan [n-1 from the previous scan line Sn-1. Turn on in response to]).

Referring to FIG. 4, a detailed operation of the pixel circuit of FIG. 5 will be described.

In the T1 period, the transistors M2 and M4 are turned on by the low level selection signal scan [n-1] of the immediately preceding scan line Sn-1. At this time, since the source of the transistor M1 is connected to the power supply VDD, the voltage of the first electrode A of the capacitor Cvth becomes the voltage (VDD + Vth) as in the first embodiment. Since the second electrode B of the capacitor Cvth is connected to the compensation power supply Vsus unlike the first embodiment, the voltage of the second electrode B of the capacitor Cvth becomes a Vsus voltage. That is, the capacitor Cvth stores the voltage (VDD + Vth-Vsus) corresponding to the threshold voltage of the transistor M1, the power supply voltage VDD, and the compensation voltage VSS.

Next, in the T2 period, the transistor M3, the high level select signal scan [n-1] of the previous scan line Sn-1 and the low level select signal scan [n] of the current scan line Sn. M4 is turned on and transistors M2 and M4 are turned off. Then, the data voltage Vdata is transferred to the second electrode B of the capacitor Cvth, so that the voltage of the first electrode A of the capacitor Cvth is boosted by the difference between the data voltage Vdata and the compensation voltage Vsus. do. Accordingly, the gate of the transistor M1, that is, the voltage Vg of the first electrode A of the capacitor Cvth is represented by Equation 4, and the current I _OLED flowing through the drain of the transistor M1 is represented by Equation 5 Become together.

As can be seen from Equation 5, since the current I _OLED flowing through the organic EL element OLED is not affected by the power supply voltage VDD, the luminance due to the voltage drop in the power supply wiring for supplying the power supply voltage VDD. Deviation can be compensated. In addition, when the compensation voltage Vsus is connected to the second electrode B of the capacitor Cvth, the current path is not formed because the first electrode A of the capacitor Cvth is floating. Therefore, the current path is not formed in the power supply line supplying the compensation voltage Vsus, so that the problem of voltage drop does not occur. Therefore, since substantially the same compensation voltage Vsus is applied to all the pixel circuits, it is possible to prevent current variation due to voltage drop. As the compensation voltage Vsus, a voltage having the same level as the power supply voltage VDD may be used.

3 and 5 illustrate transistors M1 to M4 as p-channel transistors and transistors M5 as n-channel transistors. On the contrary, transistors M1 to M4 are implemented as n-channel transistors. In addition, the transistor M5 may be implemented as a p-channel transistor. The pixel structure and driving waveform in such a case can be easily known to those skilled in the art from FIGS. 3 to 5, and thus description thereof is omitted. In addition, these transistors M1 to M5 may be formed of transistors of the same channel, which will be described below with reference to FIG.

6 is a diagram illustrating a pixel circuit according to a third exemplary embodiment of the present invention.

As shown in FIG. 6, the pixel circuit according to the third exemplary embodiment of the present invention is implemented except that the transistor M5 is implemented as a p-channel transistor and the emission scan line En is connected to the gate of the transistor M5. It is the same as the pixel circuit of 5. In this case, the emission scan line En may be disposed to be paired with the selection scan line Sn in the display panel 100 of FIG. 2. Since the transistor M5 is a p-channel, the driving waveform applied to the light emitting scan line En is inverted from the selection signal scan [n-1] of the previous scanning line Sn-1 in the driving waveform of FIG. 4. Just do it.

In the pixel circuits of FIGS. 3, 5, and 6, when the low level selection signal scan [n] is applied to the current scan line Sn to boost the voltage of the first electrode A of the capacitor Cvth, If current is supplied from the transistor M1 to the organic EL element OLED, the boosting may not be performed properly. Therefore, even in this period, the transistor M1 and the organic EL element OLED can be electrically cut off, and this embodiment will be described with reference to FIG.

7 is a driving waveform diagram of a pixel circuit according to a fourth exemplary embodiment of the present invention, and the driving waveform of FIG. 7 is applied to the pixel circuit of FIG. 6. In FIG. 7, a light emission signal applied to the light emission scan line En is illustrated by emit [n].

As shown in FIG. 7, in the fourth embodiment of the present invention, except that the high level light emission signal emit [n] is applied to the light emission scan line En in the periods T1 and T2. same. That is, in the T1 and T2 periods, the transistor M5 is turned off by the high level light emission signal emit [n] to electrically disconnect the transistor M1 and the organic EL element OLED. After the T2 period, the light emission signal emit [n] becomes low and the transistor M5 is turned on. Accordingly, a current is supplied from the transistor M1 to the organic EL element OLED to emit light.

In the pixel circuits according to the first to fourth embodiments of the present invention described above, after the voltage corresponding to the threshold voltage of the driving transistor M1 is stored in the capacitor Cvth, the threshold of the driving transistor M1 is stored using the voltage. Compensate for voltage. However, the transistors M2 and M4 are turned on according to the low level selection signal scan [n-1] to store the threshold voltage Cvth in the capacitor Cvth, and the selection signal scan [n-1] Kickback may occur due to the parasitic capacitance of transistors M2 and M4 when going to high level. As shown in FIG. 8, after kickback, the voltages of the first and second electrodes A and B of the capacitor Cvth rise, and then the data voltage Vdata when the select signal scan [n] goes low. Decreases again with boosting).

However, since the capacitor Cst is connected in parallel to the transistor M4 connected to the second electrode B of the capacitor Cvth, the voltage of the second electrode B of the capacitor Cvth is not greatly changed by the kickback. Do not. On the other hand, unlike the second electrode B, the first electrode A of the capacitor Cvth does not have a separate capacitor connected thereto, so a large voltage change occurs due to the kickback. Therefore, assuming that the voltage Vth1 is stored in the capacitor Cvth when the selection signal scan [n-1] is at the low level as shown in FIG. 8, the voltage of the capacitor Cvth is smaller than the voltage Vth1 by kickback. It becomes a voltage. As a result, when the actual data voltage Vdata is applied, the voltage stored in the capacitor Cvth becomes a Vth2 voltage smaller than the Vth1 voltage as shown in FIG. 8. Therefore, in order for the capacitor Cvth to compensate the threshold voltage normally, the voltage Vth2 should be approximated to the voltage Vth1.

9 is a graph measuring the relationship between the voltage Vth1 and the voltage Vth2 while changing the size of the capacitor Cvth while the size of the capacitor Cst is fixed at 2 pF. 9, it can be seen that there is a large difference between the voltage Vth1 and the voltage Vth2 in the region where the size of the capacitor Cvth is smaller than the size of the capacitor Cst, that is, 2pF. It can be seen that the voltage Vth2 approximates the voltage Vth1 while going to an area larger than the size of Cst). Therefore, the influence of the kickback may be reduced by setting the capacitance of the capacitor Cvth above the capacitance of the capacitor Cst in the pixel circuit of FIGS. 3, 5, and 6.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the present invention, the luminance uniformity of the light emitting display device can be improved by compensating for the deviation of the threshold voltage of the driving transistor included in the pixel circuit and the difference in voltage drop between the pixels. In addition, by setting the size of the threshold voltage compensation capacitor larger than the data storage capacitor, it is possible to reduce the influence of the kickback to maintain the maximum threshold voltage.

1 is a diagram showing a pixel circuit of an organic EL display device of a voltage writing method according to the prior art.

2 schematically illustrates a light emitting display device according to an embodiment of the present invention.

3 is a diagram illustrating a pixel circuit according to a first exemplary embodiment of the present invention.

4 is a driving timing diagram of the pixel circuit of FIG. 3.

5 is a diagram illustrating a pixel circuit according to a second exemplary embodiment of the present invention.

6 is a diagram illustrating a pixel circuit according to a third exemplary embodiment of the present invention.

7 is a driving waveform diagram of a pixel circuit according to a fourth exemplary embodiment of the present invention.

FIG. 8 is a diagram illustrating a voltage change between both ends of a threshold voltage compensation capacitor due to kickback.

9 is a view showing the effect of the kickback according to the size between the threshold voltage compensation capacitor and the storage capacitor.

Claims (10)

A light emitting display device comprising: a plurality of data lines for transmitting a data voltage, a plurality of scanning lines for transmitting a selection signal, and a plurality of pixel circuits connected to the scanning lines and the data lines, respectively. The pixel circuit, A current corresponding to a voltage between the control electrode and the second main electrode flows through the first main electrode, wherein the second main electrode is connected to a first power source; A light emitting device for emitting light corresponding to the magnitude of the applied current, A first capacitor having a first end connected to the control electrode, and A second capacitor connected between a second power supply and a second end of the first capacitor, the second capacitor having a smaller capacitance than the first capacitor, A first period in which the transistor is diode-connected and the second end of the first capacitor is electrically connected to a second power source in a state in which the first main electrode and the light emitting element are electrically disconnected, and the second of the first capacitor A light emitting display device that operates in order of a second period of applying a data voltage to the terminal. The method of claim 1, In the first period, a selection signal of a first level is applied to the immediately preceding scan line, And a selection signal of the first level is applied to the current scan line in the second period. The method of claim 2, A first switching element diode-connecting the transistor in response to a selection signal of a first level of the immediately preceding scan line, A second switching element connected between the second end of the first capacitor and the second power supply and turned on in response to a selection signal of the first level of the immediately preceding scan line; and And a third switching element configured to transfer the data voltage to the second end of the first capacitor in response to the selection signal of the first level of the current scan line. The method of claim 3, The pixel circuit further includes a fourth switching element connected between the first main electrode and the transistor, The fourth switching element is turned off in the first period and is turned on in the second period. The method of claim 3, The pixel circuit further includes a fourth switching element connected between the first main electrode and the transistor, The fourth switching element is turned off in the first and second periods and is turned on after the second period. A light emitting display device comprising: a plurality of data lines for transmitting a data voltage, a plurality of scanning lines for transmitting a selection signal, and a plurality of pixel circuits connected to the scanning lines and the data lines, respectively. The pixel circuit, A current corresponding to a voltage between the control electrode and the second main electrode flows through the first main electrode, wherein the second main electrode is connected to a first power source; A light emitting device for emitting light corresponding to the magnitude of the applied current, A first switching element for diode-connecting the transistor in a first period before the selection signal from the scan line becomes a first level; A first capacitor having a first end connected to the control electrode, A second capacitor connected between a second power supply and a second end of the first capacitor and having a smaller capacitance than the first capacitor, A second switching element connecting the second end of the first capacitor and a second power source in the first period, and And a third switching element configured to transfer a data voltage from the data line to the second electrode of the first capacitor in response to the selection signal of the first level from the scan line in a second period. The method of claim 6, And the first period is a period in which the selection signal of the first level is applied to a scan line immediately before the pixel circuit. The method of claim 7, wherein And the first and second switching elements are turned on in response to a selection signal of the first level of the immediately preceding scan line. The method of claim 6, The pixel circuit further comprises a fourth switching element connected between the transistor and the light emitting element and turned off in the first period. The method of claim 6, The pixel circuit further includes a fourth switching element connected between the transistor and the light emitting element and turned off in the first and second periods.