KR100502926B1 - Light emitting display device and display panel and driving method thereof - Google Patents

Abstract

A driving transistor for outputting a current for driving the organic electroluminescent element is formed in a pixel circuit of the organic electroluminescent display, and a source of the driving transistor is connected to a power supply voltage. The first capacitor is connected between the power supply voltage and the gate of the driving transistor, and the second capacitor is connected to the control electrode and the scan line of the driving transistor. First, in response to a low level selection signal from the scan line, the first switching element transfers the data current from the data line to the driving transistor, and the second switching element diode-connects the driving transistor in response to the selection signal. The voltage corresponding to the data current is then stored in the first capacitor. Next, the selection signal goes high and the first switching element is turned off to cut off the data current. The voltage of one end of the second capacitor is increased by the amount of level change of the selection signal, and thus the voltage of the first capacitor is changed. In addition, the driving current is output from the transistor by the voltage of the first capacitor, and the driving current is transmitted to the organic electroluminescent element in response to the light emission signal. In this way, the current flowing through the organic electroluminescent element can be controlled as a large data current.

Description

LIGHT EMITTING DISPLAY DEVICE AND DISPLAY PANEL AND DRIVING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting display device, a display panel thereof, and a driving method thereof, and more particularly, to an organic electroluminescent display device.

In general, an organic EL display device is a display device for electrically exciting a fluorescent or phosphorescent organic compound to emit light, and is capable of displaying an image by voltage driving or current writing N × M organic light emitting cells. As shown in FIG. 1, the organic light emitting cell has a structure of an anode (ITO), an organic thin film, and a cathode electrode (metal). The organic thin film has a multilayer structure including an emitting layer (EML), an electron transport layer (ETL), and a hole transport layer (HTL) to improve the emission efficiency by improving the balance between electrons and holes. It also includes a separate electron injecting layer (EIL) and a hole injecting layer (HIL).

The organic light-emitting cell may be driven by a simple matrix method and an active matrix method using a thin film transistor (TFT) or a MOSFET. In the simple matrix method, the anode and the cathode are orthogonal and the line is selected and driven, whereas the active driving method connects the thin film transistor and the capacitor to each indium tin oxide (ITO) pixel electrode to maintain the voltage by the capacitor capacitance. It is a driving method. In this case, the active driving method is divided into a voltage programming method and a current programming method according to the type of signal applied to maintain the voltage on the capacitor.

Hereinafter, an organic EL display device of a voltage and current writing method according to the prior art will be described with reference to FIGS. 2 and 3.

FIG. 2 is a pixel circuit of a conventional voltage writing method for driving an organic EL element, and typically shows one of N x M pixels. Referring to FIG. 2, a transistor M1 is connected to an 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 C1 for maintaining the applied voltage for a predetermined period is connected between the source and the gate of the transistor M1. The gate of the transistor (M2) has been the scan line (S _n) connected to, and is a data line (D _m) connected to the source side.

Referring to the operation of the pixel having such a structure, when the transistor M2 is turned on by the selection signal applied to the gate of the switching transistor M2, the data voltage from the data line D _m is applied to the gate of the transistor M1. Is approved. The capacitor (C1) a voltage (V _GS) corresponds to the transistor (M2) current (I _OLED) flows, the current (I _OLED) the organic EL element (OLED) in response to the to the charge between the gate and the source by the Emits 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, V _GS is the voltage between the source and gate of transistor M1, V _TH is the threshold voltage of transistor M1, V _DATA is the data voltage, and β is a constant. Indicates a value.

As shown in Equation 1, according to the pixel circuit shown in Fig. 2, a current corresponding to the applied data voltage is supplied to the organic EL element OELD, and the organic EL element emits light corresponding to the supplied current. At this time, the applied data voltage has a multi-level value in a predetermined range in order to express the gray scale.

However, such a conventional voltage writing pixel circuit has a problem in that it is difficult to obtain a high gradation due to variations in threshold voltage V _TH and electron mobility of the thin film transistor caused by nonuniformity in the manufacturing process. For example, when driving a thin film transistor of a pixel at 3V, a voltage must be applied to the gate of the thin film transistor at intervals of 12 mV (= 3 V / 256) 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. In addition, since the β value in Equation 1 is changed due to the deviation of mobility, it is difficult to express higher gray scales.

On the other hand, in the pixel circuit of the current writing method, if the current source for supplying the current to the pixel circuit is uniform through the entire data line, even if the driving transistors in each pixel have non-uniform voltage-current characteristics, uniform display characteristics can be obtained.

Fig. 3 is a pixel circuit of a conventional current write method for driving an organic EL element, which representatively shows one of N × M pixels. Referring to FIG. 3, the transistor M1 is connected to the organic EL element OLED to supply current for emitting light, and the amount of current of the transistor M1 is controlled by a data current applied through the transistor M2. have.

First, when a scanning line transistor (M2, M3) by the selection signal from the (S _n) is turned on, the transistor (M1) is corresponding to the diode-connected state, and the data line (D _m) of data current (I _DATA) from The voltage is stored in capacitor C1. Next, the select signal from the scan line (S _n) is a high-level voltage and the transistor (M2, M3) is turned off, a light emission signal from the scan line (E _n) is a low-level voltage, the transistor (M4) are turned on . Then, power is supplied from the power supply voltage VDD and a current corresponding to the voltage stored in the capacitor C1 flows to the organic EL element OLED to emit light. At this time, a current flowing through the organic EL element OLED is represented by Equation 2 below.

Here, V _GS is a voltage between the source and the gate of the transistor M1, V _TH is a threshold voltage of the transistor M1, and β represents a constant value.

As shown in Equation 2, according to the conventional current pixel circuit, since the current I _OLED flowing through the organic EL element is the same as the data current I _DATA , if the write current source is uniform throughout the panel, uniform characteristics are obtained. It becomes possible. However, since the current I _OLED flowing through the organic EL element is a fine current, it is necessary to control the pixel circuit as the fine current I _DATA , so that it takes a long time to charge the data line. For example, assuming that the data line load capacitance is 30 mA, several hours are required to charge the load of the data line with a data current of several tens of thousands to several hundred mA. This is a problem that the charging time is not enough when considering the line time (line time) that is several tens of degrees.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a light emitting display device capable of compensating a threshold voltage or mobility of a transistor and sufficiently charging a data line.

In the light emitting display device according to the present invention, a plurality of pixels respectively formed in a plurality of data lines for transmitting a data current representing an image signal, a plurality of scan lines for transmitting a selection signal, and a plurality of pixels defined by the data lines and the scan lines The circuit is formed. The pixel circuit includes a light emitting element, a first transistor, first to third switching elements, and first and second storage elements. The first transistor supplies a drive current for emitting the light emitting element, and the first switching element transfers the data signal from the data line in response to the selection signal from the scan line. The first storage element stores the first voltage corresponding to the data current from the first switching element by the first level of the first control signal. The second storage element is electrically connected between the first storage element and the signal line for supplying the first control signal, and the coupling with the first storage element when the first control signal changes from the first level to the second level. The first voltage of the first storage element is changed to the second voltage through the second voltage. The second switching element diode-connects the first transistor in response to the first level of the first control signal, and the third switching element receives the driving current output from the first transistor by the second voltage in response to the second control signal. Transfer to the light emitting element.

The second switching element is preferably electrically connected between the second main electrode and the control electrode of the first transistor, or electrically connected between the data line and the control electrode of the first transistor.

According to the present invention, a first switching element for transmitting a data current from a data line in response to a selection signal from a scanning line, a transistor for outputting a driving current corresponding to the data current, between a first main electrode and a control electrode of the transistor A method of driving a light emitting display device including a pixel circuit including a first storage element that is electrically connected and a light emitting element that emits light in response to a driving current from a transistor is provided. First, the transistor is diode-connected with a control signal of the first level, and the control electrode voltage of the transistor is set as the first voltage in response to the data current from the first switching element. Next, the data current is interrupted, and the control signal is changed from the first level to the second level to be applied to the second end of the second storage element having the first end connected to the control electrode of the transistor, and the first and second storages. Coupling the device changes the control electrode voltage of the transistor to a second voltage. Then, a driving current output from the transistor is applied to the light emitting element corresponding to the second voltage.

The display panel of the light emitting display device according to the present invention includes a plurality of data lines for transmitting a data current representing an image signal, a plurality of scan lines for transmitting a selection signal, and a plurality of pixels defined by the data lines and the scan lines, respectively. A plurality of pixel circuits are formed. The pixel circuit includes a light emitting element, a first transistor, first to third switching elements, and first and second storage elements. The first transistor outputs a current for driving the light emitting element and is electrically connected to a first signal line to which the first main electrode supplies a power supply voltage. The first switching element transfers the data current from the data line to the first transistor in response to the selection signal from the scan line, and the second switching element diode-connects the first transistor in response to the first level of the first control signal. . The third switching device transfers the driving current from the transistor to the light emitting device in response to the second control signal. The first storage element is electrically connected between the control electrode of the first transistor and the first main electrode, and the second storage element is electrically connected to the control electrode of the first transistor and the second signal line supplying the first control signal. .

The display panel includes a first section in which the first transistor is diode-connected by the first control signal of the first level and the data current is transmitted to the first transistor by the selection signal, and the data current is blocked and the first control signal is A second level, the level change of the first control signal being reflected on the control electrode of the first transistor by coupling of the first and second storage elements, and the driving current being transmitted to the light emitting element by the second control signal; It is preferable to operate in the order of two sections.

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 a case where another part is connected in between. In the drawings, reference numerals of signals applied to the pixel circuits through the respective scan lines are the same as the scan lines for convenience of description.

First, an organic EL display device according to an exemplary embodiment of the present invention will be described with reference to FIG. 4. 4 is a schematic plan view of an organic EL display device F according to an embodiment of the present invention.

As shown in FIG. 4, the organic EL display device according to the exemplary embodiment of the present invention includes an organic EL display panel 10, a scan driver 20, and a data driver 30.

The organic EL display panel 10 includes a plurality of data lines D ₁ -D _M extending in a row direction, a plurality of scanning lines S ₁ -S _N , E ₁ -E _N , and a plurality of pixels extending in a column direction. Circuit 11. The data lines D ₁ -D _M transfer data current representing the image signal to the pixel circuit 11. The scan lines S ₁ -S _N transfer the selection signals to the pixel circuits 11, and the scan lines E ₁ -E _N transfer the light emission signals to the pixel circuits 11. The pixel circuit 11 is formed in a pixel region defined by two neighboring data lines and two neighboring scan lines.

The data driver 30 applies a data current to the data lines D ₁ -D _M , and the scan driver 20 applies a selection signal to the scan lines S ₁ -S _N and the scan lines E ₁ -E _N , respectively. The light emission signals are sequentially applied.

Next, the pixel circuit 11 of the organic EL display device according to the first embodiment of the present invention will be described in detail with reference to FIG. 5 is an equivalent circuit diagram of a pixel circuit according to a first embodiment of the present invention. In FIG. 5, only the pixel circuit connected to the m th data line D _m and the n th scan line S _n is illustrated for convenience of description.

As shown in Fig. 5, the pixel circuit 11 according to the first embodiment of the present invention includes an organic EL element OLED, a transistor M1, switching elements S1, S2, S3, and capacitors C1, C2. The transistor M1 is formed of a PMOS transistor.

The switching element S1 is connected between the data line D _m and the gate of the transistor M1, and the data current I _DATA from the data line D _m in response to the selection signal from the scanning line S _n . Is transferred to the transistor M1. A switching element (S2) is connected between the drain and the gate of the transistor (M1), in response to a select signal from the scan line (S _n) causes the diode-connected transistor (M1).

The transistor M1 has a source connected to the power supply voltage VDD and a drain connected to the switching element S3. The gate-source voltage of the transistor M1 is determined corresponding to the data current I _DATA , and the capacitor C1 is connected between the gate and the source of the transistor M1 to constant the gate-source voltage of the transistor M1. Maintain period. A capacitor (C2) is connected between the gate of the scanning line _(n S) and the transistor (M1) to control the gate voltage of the transistor (M1).

The switching element S3 supplies a current flowing through the transistor M1 to the organic EL element OLED in response to the light emission signal from the scanning line E _n . The organic EL element OLED is connected between the switching element S3 and the reference voltage and emits light corresponding to the amount of current flowing through the transistor M1.

In the first embodiment of the present invention, the switching elements S1, S2, S3 are shown as general switches, but the switching elements S1, S2, S3 are also preferably formed of transistors. Hereinafter, an embodiment in which the switching elements S1, S2, and S3 are implemented as PMOS transistors will be described in detail with reference to FIGS. 6 and 7.

6 is an equivalent circuit diagram of a pixel circuit according to a second exemplary embodiment of the present invention, and FIG. 7 is a driving waveform diagram for driving the pixel circuit of FIG. 6.

As shown in FIG. 6, the pixel circuit according to the second exemplary embodiment of the present invention has the transistors M2, M3, and M4 formed instead of the switching elements S1, S2, and S3 in the pixel circuit of FIG. 5. Except for this, it has the same structure as in the first embodiment. Transistors M2, M3, and M4 are formed of PMOS transistors, and scan lines S _n are connected to gates of transistors M2 and M3, and scan lines E _n are connected to gates of transistors M4.

Next, the operation of the pixel circuit of FIG. 6 will be described in detail with reference to FIG. 7. First, the scanning line is the turn-on transistor (M2, M3) by a selection signal of a low level voltage is applied through the (S _n), a transistor (M1) is the data current (I _DATA from the connecting diode and a data line (D _m) ) Flows through the transistor M1. At this time, since the relation of Equation 3 is established between the gate-source voltage V _GS of the transistor M1 and the current I _DATA flowing through the transistor M1, the gate-source voltage V _GS of the transistor M1 is established. ) Becomes as shown in equation (4).

Where β is a constant value and V _TH is the threshold voltage of transistor M1.

Here, V _G is the gate voltage of the transistor M1 and V _DD is the voltage supplied to the transistor M1 by the power supply voltage VDD.

Next, the selection signal (S _n) being that when the light emission signal (E _n) with the high level voltage to a low level voltage, the transistor (M2, M3) is turned off and transistor (M4) is turned on. Is increased by a select signal (S _n), the level rise (ΔV _S) of a selection signal (S _n) of the contact voltage of the capacitor (C2) and a scan line (S _n) When the low level voltage to a high level voltage. Therefore, the gate voltage V _G of the transistor M1 increases due to the coupling of the capacitors C1 and C2, and the increase amount ΔV _G is expressed by Equation 5.

Here, C ₁ and C ₂ are the capacitances of the capacitors C1 and C2, respectively.

Since the gate voltage V _{G of the} transistor M1 has increased by ΔV _G , the current I _OLED flowing through the transistor M1 is expressed by Equation 6 below. Since the transistor M3 is turned on by the light emission signal E _n , the current I _OLED of the transistor M1 is supplied to the organic EL element OLED to emit light.

Since the data current I _DATA from Equation 6 is given by Equation 7, the data current I _DATA can be set to a value larger than the current I _OLED flowing through the organic EL element OLED. In other words, the microcurrent flowing in the organic EL element OLED can be controlled by the large data current I _DATA , thereby ensuring the charging time of the data line.

In the second embodiment of the present invention has been driving the selection signal (S _n) to directly transistor (M2) from the scan line (S _n), the rise time of the selection signal (S _n) by the scanning line load alters transistor (M2 ) May cause a switching error. The transistor selection signals (S _n) in order to reduce the influence of the switching error of the (M2) can be buffered to be applied to the transistor (M2). Hereinafter, such an embodiment will be described in detail with reference to FIG. 8.

8 is an equivalent circuit diagram of a pixel circuit according to a third exemplary embodiment of the present invention.

As shown in Fig. 8, the pixel circuit according to the third embodiment of the present invention has the same structure as the first embodiment except for the buffer. The buffer consists of four transistors M5-M8, the transistors M5 and M7 are formed of PMOS transistors, and the transistors M6 and M8 are formed of NMOS transistors. The transistors M5 and M6 are connected in series between the power supply voltage VDD and the reference voltage, and the contacts of the transistors M5 and M6 are connected to the gates of the transistors M7 and M8. Select signals from the (m-1) th pixel circuits are input to the gates of the transistors M5 and M6. The transistors M7 and M8 are connected in series between the power supply voltage VDD and the reference voltage, and an output at the contacts of the transistors M7 and M8 is applied to the gates of the transistors M2 and M3 as selection signals.

Referring to the operation of the buffer, when the selection signal input to the gates of the transistors M5 and M6 is the high level voltage, the transistor M6 is turned on so that the signal of the low level voltage is supplied by the reference voltage to the gates of the transistors M7 and M8. Is entered. The transistor M7 is turned on by the signal of the low level voltage, and the signal of the high level voltage is applied to the gates of the transistors M2 and M3 as the selection signal by the power supply voltage VDD. When the selection signal input to the gates of the transistors M5 and M6 is a low level voltage, the transistor M5 is turned on so that a high level voltage signal is input to the gates of the transistors M7 and M8 by the power supply voltage VDD. . The transistor M8 is turned on by the signal of the high level voltage, and the signal of the low level voltage is applied to the gates of the transistors M2 and M3 as the selection signal by the reference voltage. By using such a buffer, the rise times of the selection signals in all the pixels are the same, thereby reducing the influence of the switching error of the transistor M2.

In the third embodiment of the present invention, a buffer is formed using four transistors. However, the present invention is not limited thereto, and other types of buffers may be used.

In the first to third embodiments of the present invention, a separate scan line E _n transmitting the light emission signal E _n is used to control the driving of the switching element S3 or the transistor M4. At this time, to control the driving of the switching element (S3) or a transistor (M4) to the selection signal (S _n) from without using a separate scan line (E _n) scan lines (S _n), and, with respect to this aspect This will be described in detail with reference to FIGS. 9 and 10.

9 is an equivalent circuit diagram of a pixel circuit according to a fourth exemplary embodiment of the present invention, and FIG. 10 is a driving waveform diagram for driving the pixel circuit of FIG. 9.

As shown in FIG. 9, the pixel circuit according to the fourth embodiment of the present invention has the same structure as the pixel circuit of FIG. 6 except for the absence of the scan line E _n and the type and connection relationship of the transistor M4. . In detail, the transistor M4 is formed of the NMOS transistor M4, and the scan line S _n is connected to the gate of the transistor M4 instead of the scan line E _n . The transistor (M4) when the voltage is at a high level selection signals (S _n) as shown in Fig. 10 is turned on is transmitted to the current (I _OLED) is an organic EL element (OLED) of the transistor (M1).

When the transistor M4 is implemented as an NMOS transistor as described above, an aperture ratio of the pixel can be increased because a separate wiring for transmitting the light emission signal is not required.

In the first to fourth embodiments of the present invention, the transistor M3 is connected between the drain and the gate of the transistor M1 in order to diode-connect the transistor M1. Alternatively, the transistor M3 may be connected between the drain of the transistor M1 and the data line D _m , which will be described in detail with reference to FIGS. 11 and 12.

11 and 12 are equivalent circuit diagrams of pixel circuits according to fifth and sixth embodiments of the present invention, respectively.

As shown in FIG. 11, the pixel circuit according to the fifth embodiment of the present invention has the same structure as the pixel circuit of FIG. 6 except for the connection relationship between the transistors M3. In detail, the transistor M3 is connected between the data line D _m and the drain of the transistor M1, and the pixel circuit can be driven using the driving waveform of FIG. 7. Scanning line when the low-level voltage selection signal (S _n) from the (S _n), the transistor (M2, M3) is turned on at the same time because the gate and drain of the transistor (M1) are connected to each other. That is, similar to the pixel circuit of Figure 6, the selection signal (S _n), the transistor (M1) when the low-level voltage is diode-connected.

As in the pixel circuit of FIG. 6, when the transistor M3 is connected between the gate and the drain of the transistor M1, the gate voltage of the transistor M1 may be affected when the transistor M3 is turned off. However, when the transistor M3 is connected to the data line D _m as in the fifth embodiment of the present invention, when the transistor M3 is turned off, the gate voltage of the transistor M1 is reduced. Can be.

Next, referring to FIG. 12, the pixel circuit of FIG. 9 is the pixel circuit of FIG. 9 except that the transistor M3 is connected between the data line D _m and the drain of the transistor M1. Has the same structure as

And it may be connected only to the gate of the first to sixth embodiments in the scan line (S _n) of the transistors (M2, M3), but is connected to both the gate and contrast scan line (S _n) of the transistors (M2) of the present invention . Hereinafter, such an embodiment will be described in detail with reference to FIGS. 13 to 16.

13 and 15 are equivalent circuit diagrams of the pixel circuits according to the seventh and eighth embodiments of the present invention, respectively, and FIGS. 14 and 16 are driving waveform diagrams for driving the pixel circuits of FIGS. 13 and 15, respectively.

As shown in FIG. 13, the pixel circuit according to the seventh embodiment of the present invention has the same structure as the pixel circuit of FIG. 6 except for a connection relationship between the transistor M3 and the capacitor C2. In detail, the gate of the transistor M3 is connected to a separate scan line B _n , and the capacitor C2 is connected between the gate of the transistor M1 and the scan line B _n .

Referring to FIG. 14, the scan line (B _n) boost signal (B _n) from the selection signal (S _n) that after by the high level voltage to a low level voltage and a selection signal (S _n) prior to the low-level voltage Becomes a high level voltage. Then, after the transistor M2 is completely turned off, the voltage at the contact point of the capacitor C2 and the scan line B _n increases by the level rising width ΔV _S of the boost signal B _n . Therefore, the gate voltage V _G of the transistor M1 is increased by the increase amount ΔV _G of Equation 5 by coupling the capacitors C1 and C2, so that the current I _OLED shown in Equation 7 is induced. It is supplied to the EL element OLED. Since the rest of the operation of the pixel circuit of FIG. 13 is the same as that of the pixel circuit of FIG. 6, a detailed description thereof will be omitted.

In this way, according to the seventh embodiment of the present invention scan line (S _n) is so connected to only the gate of the transistor (M2) the load of the scan line (S _n) decreases, the rise time of the selection signal (S _n) in the former panel I can make it constant. In addition, since the gate node of the transistor M2 is boosted after the transistor M2 is completely turned off, the influence of the switching error of the transistor M2 may be reduced.

Next, referring to FIG. 15, in the pixel circuit according to the eighth embodiment of the present invention, the scan line E _n is removed from the pixel circuit of FIG. 13, and the gate of the transistor M4 is connected to the scan line B _n . The transistor M4 is formed of a transistor of a type opposite to that of the transistor M3, that is, an NMOS transistor.

As shown in FIG. 16, in the driving waveform for driving the pixel circuit of FIG. 15, the light emission signal E _n is removed from the driving waveform of FIG. 14. When the boost signal B _n becomes a high level voltage and the gate voltage of the transistor M2 is boosted, the transistor M4 is turned on. Therefore, the gate voltage of the transistor M2 is boosted, and the current I _OLED output from the transistor M1 is supplied to the organic EL element OLED to emit light.

In the second to eighth embodiments of the present invention, the transistors M1-M3 are formed of PMOS transistors, but the transistors M1-M3 may be formed of NMOS transistors. Hereinafter, such an embodiment will be described with reference to FIGS. 17 to 26.

17, 19, 21, 22, 23, and 25 are equivalent circuit diagrams of pixel circuits according to the ninth to fourteenth embodiments of the present invention, respectively, and FIGS. 18, 20, 24, and 26 are respectively. 17 and 19 are driving waveform diagrams for driving the pixel circuits of FIGS. 17, 19, 23, and 25, respectively.

Referring to FIG. 17, in the pixel circuit according to the ninth embodiment of the present invention, all of the transistors M1-M4 are implemented as NMOS transistors, and the connection structure thereof is symmetrical with the pixel circuit of FIG. 6. If described in detail, the transistor (M2) is connected between the gate of the data line (D _m) and the transistor (M1) and is a scan line (S _n) connected to its gate. The transistor (M3) is connected between the drain and the gate of the transistor (M1) and is a scan line (S _n) connected to its gate. The transistor M1 has a source connected to a reference voltage and a drain connected to the organic EL element OLED. The capacitor C1 is connected between the gate and the source of the transistor M1, and the organic EL element OLED is connected between the transistor M4 and the power supply voltage VDD. The scan line E _n is connected to the gate of the transistor M4.

And the transistor (M2, M3, M4) is because the NMOS transistor, the pixel circuit selection signal (S _n) and the light emission signal (E _n) for driving in Fig. 17 as shown in Fig. 18 is a signal shown in Fig. 7 (S _n , E _n ) has the inverted form. The detailed operation of the pixel circuit of FIG. 17 can be easily made from the description of the second embodiment, and thus description thereof is omitted.

Next, referring to FIG. 19, in the pixel circuit according to the tenth embodiment of the present invention, transistors M1-M3 are implemented as NMOS transistors, and transistor M4 is implemented as PMOS transistors. Symmetric to the circuit. Since the transistors M2 and M3 are NMOS transistors and the transistor M4 is a PMOS transistor, the selection signal S _n for driving the transistors M2-M4 as shown in FIG. 20 is the selection signal S of FIG. 10. _n ) has an inverted form.

Next, referring to FIG. 21, in the pixel circuit according to the eleventh exemplary embodiment, the transistors M1-M4 are formed as NMOS transistors in the pixel circuit of FIG. 11. 22, in the pixel circuit according to the twelfth embodiment of the present invention, transistors M1-M3 are formed of NMOS transistors and transistors M4 are formed of PMOS transistors in the pixel circuit of FIG. 12.

Referring to FIG. 23, in the pixel circuit according to the thirteenth embodiment, transistors M1 to M4 are formed as NMOS transistors in the pixel circuit of FIG. 13. Drive waveform _{(S n, B n, E} n) for also driving the pixel circuit of Figure 23 as indicated at 24 has an inverted form with respect to the drive waveform _{(S n, B n, E} n) of FIG. 14 .

Referring to FIG. 25, the pixel circuit according to the fourteenth exemplary embodiment of the present invention forms transistors M1-M3 as NMOS transistors and transistors M4 as PMOS transistors in the pixel circuit of FIG. 15. As shown in Figure 26, the driving waveform for driving the pixel circuit of FIG. 25 (S _n, B _n) has an inverted form with respect to the drive waveform (S _n, B _n) of FIG.

The embodiments in which the transistors M1-M3 are formed of NMOS transistors have been briefly described with reference to FIGS. 17 through 26. The pixel circuits and their operation shown in FIGS. 17 to 26 are easily understood from the description of the embodiment formed of the PMOS transistor, and thus detailed description thereof will be omitted.

In the embodiment of the present invention, only the case in which the transistors M1-M3 are formed of PMOS or NMOS transistors has been described. However, the present invention is not limited thereto, but a combination of PMOS and NMOS transistors or other switching having the same or similar functions. An element can also be used.

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.

As described above, according to the present invention, the current flowing through the organic EL element can be controlled as a large data current, so that the data line can be sufficiently charged for one line time. In addition, the current flowing through the organic EL element is compensated for variations in threshold voltage or mobility of the transistor, and a high resolution and large area light emitting display device can be realized.

1 is a conceptual diagram of an organic electroluminescent device.

2 is an equivalent circuit diagram of a pixel circuit of a conventional voltage driving method.

3 is an equivalent circuit diagram of a pixel circuit of a conventional current write method.

4 is a schematic plan view of an organic EL display device according to an embodiment of the present invention.

5, 6, 8, 9, 11, 12, 13, 15, 17, 19, 21, 22, 23 and 25 are the first to the first embodiments of the present invention, respectively. 14 is an equivalent circuit diagram of a pixel circuit according to an exemplary embodiment.

7, 10, 14, 16, 18, 20, 24, and 26 are pixels of FIGS. 6, 9, 13, 15, 17, 19, 23, and 25, respectively. It is a drive waveform diagram for driving a circuit.

Claims (20)

A light emitting display in which a plurality of data lines for transmitting a data current representing an image signal, a plurality of scanning lines for transmitting a selection signal, and a plurality of pixel circuits respectively formed in the plurality of pixels defined by the data lines and the scanning lines are formed. In the apparatus, The pixel circuit, A light emitting device for emitting light in response to the applied current, A first transistor supplying a driving current for emitting the light emitting element, A first switching element transferring a data signal from the data line in response to a selection signal from the scan line; A second switching element for diode-connecting the first transistor in response to a first level of a first control signal, A first storage element for storing a first voltage corresponding to the data current from the first switching element by a first level of the first control signal, Coupling with the first storage element between the first storage element and a signal line for supplying the first control signal and when the first control signal changes from the first level to a second level A second storage element for changing the first voltage of the first storage element into a second voltage through A third switching device for transmitting the driving current output from the first transistor by the second voltage to the light emitting device in response to a second control signal; A light emitting display device comprising a. The method of claim 1, The first storage element is electrically connected between the first main electrode and the control electrode of the first transistor, and the second storage element is electrically connected between the control electrode and the signal line of the first transistor. . The method of claim 1, The second switching element is electrically connected between the second main electrode and the control electrode of the first transistor. The method of claim 1, And the second switching element is electrically connected between the data line and the control electrode of the first transistor. The method of claim 1, The signal line is the scan line, and the first control signal is the selection signal. The method of claim 5, And the second control signal is the selection signal, and the third switching element is responsive to a disable level of the selection signal. The method of claim 1, The signal line for supplying the first control signal is a signal line separate from the scan line, and the first control signal is a light emitting display that becomes the second level from the first level after the selection signal becomes the disable level. Device. The method of claim 7, wherein And the second control signal is the first control signal and the third switching element is responsive to a second level of the second control signal. The method according to claim 6 or 8, And the second switching element is a transistor of a first conductivity type, and the third switching element is a transistor of a second conductivity type. The method of claim 1, The first to third switching elements and the first transistor are transistors of the same conductivity type. The method of claim 1, The pixel circuit further includes a buffer for buffering the selection signal and then transferring the selection signal to the first switching element. A first switching element transferring a data current from the data line in response to a selection signal from the scan line, a transistor outputting a drive current, a first storage element electrically connected between the first main electrode and the control electrode of the transistor; And a method of driving a light emitting display device having a pixel circuit including a light emitting element emitting light in response to a driving current from the transistor. Diode-connecting the transistor with a first level control signal and setting the control electrode voltage of the transistor as the first voltage in response to the data current from the first switching element, Blocking the data current, applying a control signal of a second level to a second end of a second storage element having a first end connected to a control electrode of the transistor, and coupling the first and second storage elements Changing the control electrode voltage of the transistor to a second voltage; and Applying a driving current output from the transistor to the light emitting element corresponding to the second voltage; Method of driving a light emitting display device comprising a. The method of claim 12, And the control signal is the same signal as the selection signal. The method of claim 12, And the control signal becomes the second level after the selection signal becomes the disable level. The method of claim 12, And the pixel circuit further comprises a second switching element configured to transfer a driving current from the transistor to the light emitting element in response to the control signal of the second level. A light emitting display in which a plurality of data lines for transmitting a data current representing an image signal, a plurality of scanning lines for transmitting a selection signal, and a plurality of pixel circuits respectively formed in the plurality of pixels defined by the data lines and the scanning lines are formed. In the display panel of the device, The pixel circuit, A light emitting device for emitting light in response to the applied current, A first transistor for outputting a current for driving a light emitting element and electrically connected to a first signal line to which a first main electrode supplies a power voltage; A first switching element transferring a data current from the data line to the first transistor in response to a selection signal from the scan line; A second switching element diode-connecting the first transistor in response to a first level of a first control signal, A third switching element transferring a driving current from the transistor to the light emitting element in response to a second control signal; A first storage element electrically connected between the control electrode and the first main electrode of the first transistor, and A second storage element electrically connected between a control electrode of the first transistor and a second signal line supplying the first control signal A display panel of the light emitting display device comprising a. The method of claim 16, A first period in which the first transistor is diode-connected by the first control signal of the first level and the data current is transferred to the first transistor by the selection signal, and The data current is cut off and the first control signal becomes a second level so that the level change of the first control signal is reflected on the control electrode of the first transistor by coupling of the first and second storage elements, A second section in which the driving current is transmitted to the light emitting device by the second control signal A display panel of a light emitting display device that operates in order. The method of claim 17, The second signal line is the scan line, and the first control signal is the selection signal. The method of claim 17, And the second signal line is a signal line separate from the scan line, and the first control signal is set to the second level after the selection signal becomes the disable level. The method of claim 17, And wherein the second control signal is the same signal as the first control signal, the second switching element is a transistor of a first conductivity type and the third switching element is a transistor of a second conductivity type.