KR101818462B1 - Driving circuit for organic light emitting diode display and method for driving the same - Google Patents

Abstract

There is provided a driving circuit and a driving method of an organic light emitting display device capable of compensating a threshold voltage and a mobility of a driving transistor to minimize a short afterimage and brightness unevenness that occur during panel driving. A driving circuit of an organic light emitting display device includes a gate connected to a gate line to which a gate signal is applied, A first transistor coupled to the data line and outputting the data signal according to the gate signal; A gate connected to the gate line, a source connected to a reference voltage line to which a reference voltage is applied, and a second transistor outputting the reference voltage in accordance with the gate signal; A gate connected to a control line to which a control signal is applied, a source connected to a power supply voltage line for applying a power supply voltage, and a third transistor for outputting the power supply voltage in accordance with the control signal; A first capacitor connected at one end to a drain of the first transistor and at the other end to a drain of the third transistor, the first capacitor storing the data signal; A fourth transistor connected to a drain of the second transistor, a source connected to a drain of the third transistor, and providing a current for driving the organic electroluminescent device; A second capacitor connected at one end to the drain of the third transistor and at the other end to the drain of the second transistor and providing a constant bias voltage to the gate of the fourth transistor; And an anode connected to a drain of the fourth transistor, and a cathode connected to a ground voltage line to which a ground voltage is applied.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting display,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a driving circuit and a driving method of an organic light emitting display, and more particularly, to a driving circuit and a driving method of an organic light emitting display that compensate for a threshold voltage and mobility of a driving transistor, The present invention relates to a driving circuit and a driving method of an organic light emitting display device.

It is expected that the 21st century will become an information society. Therefore, it is important to develop a high-performance flat panel display device for multimedia because it needs to obtain information easily from anywhere. In particular, development of technologies related to the development of devices for semiconductors and display devices has been regarded as important for communication and computers. One of the devices that are attracting attention as a color display device is Organic Light Emitting Diode (OLED).

The organic electroluminescent device can be classified into a passive matrix organic light emitting device (PMOLED) and an active matrix organic light emitting device (AMOLED) according to the structure. The development of AMOLED is essential.

Each of the plurality of pixels constituting the organic light emitting display includes a pixel composed of an organic light emitting layer between an anode and a cathode, and a pixel circuit independently driving each pixel. The pixel circuit mainly includes a switching transistor and a capacitor and a driving transistor. The switching transistor charges the data signal in response to the scan pulse, and the driving transistor adjusts the gradation of the pixel by adjusting the magnitude of the current supplied to the pixel according to the magnitude of the data voltage charged in the capacitor.

However, when a characteristic difference such as a threshold voltage and mobility occurs between the driving transistors formed in each pixel, the amount of current for driving the organic light emitting diode OLED changes, A brightness difference occurs between the two. Generally, the difference in the characteristics of the driving transistor generates spots or patterns on the screen, and a characteristic difference between driving transistors generated while driving the liquid crystal panel may cause a short afterimage and a long afterimage on the liquid crystal panel. In addition, when driving the liquid crystal panel, a deviation occurs between the pixels due to the resistance of the power supply voltage line to which the power supply voltage is applied, thereby causing uneven brightness of the liquid crystal panel.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a driving circuit and a driving method of an organic light emitting display device which can compensate a threshold voltage and mobility of a driving transistor to minimize a short afterimage and luminance non- .

Other objects and features of the present invention will be described in the following description of the invention and claims.

According to an aspect of the present invention, there is provided a driving circuit for an organic light emitting display device, the driving circuit for controlling an electric current supplied to an organic light emitting display, A first transistor connected to a gate line to which a gate signal is applied, a source connected to a data line to which a data signal is applied, a first transistor for outputting the data signal in accordance with the gate signal, a gate connected to the gate line, A second transistor connected to a reference voltage line to which a reference voltage is applied and outputting the reference voltage according to the gate signal, a gate connected to a control line to which a control signal is applied, and a source connected to a power supply voltage line And a third transistor connected to the first transistor and outputting the power supply voltage according to the control signal, A first capacitor for storing the data signal, a gate connected to a drain of the second transistor, and a source connected to a drain of the third transistor, the other end of the first capacitor being connected to a drain of the third transistor, A fourth transistor connected to the drain of the third transistor and connected to the drain of the second transistor, the other end of the fourth transistor being connected to the drain of the second transistor, And an anode connected to a drain of the fourth transistor, and a cathode connected to a ground voltage line to which a ground voltage is applied. The organic electroluminescent device includes a first capacitor and a second capacitor.

A data voltage is applied to the source of the first transistor, a reference voltage is applied to the source of the second transistor, and a source voltage is applied to the source of the third transistor.

When a gate ON signal is applied to the gates of the first and second transistors and a control ON signal is applied to the gate of the third transistor to turn on the first to third transistors, Is higher than the drain voltage of the second transistor.

A gate on signal is applied to the gates of the first and second transistors and a control off signal is applied to the gate of the third transistor to turn on the first and second transistors and turn off the third transistor The drain voltage of the third transistor is set to a value obtained by adding the threshold voltage of the fourth transistor to the reference voltage.

A gate connected to the gate line, a source connected to the reference voltage line, a drain connected to the drain of the fourth transistor, and a fifth transistor for inhibiting initial light emission of the organic electroluminescent device.

A gate off signal is applied to the gates of the first and second transistors and a control ON signal is applied to the gate of the third transistor so that the first and second transistors are turned off and the third transistor is turned on A current for driving the organic electroluminescent device flows through the second transistor, the fourth transistor, and the fifth transistor to the reference voltage line.

The potential of the reference voltage line and the potential of the ground voltage line connected to the cathode of the organic electroluminescent device are kept at the same potential.

The fourth transistor is a source follower.

The first to fourth transistors are formed of any one selected from a P-type transistor, an N-type transistor, an amorphous silicon (a-Si), and an oxide film.

The reference voltage is a ground voltage.

According to another aspect of the present invention, there is provided a method of driving an organic light emitting display including a plurality of control lines, a plurality of reference voltage lines, a plurality of gate lines, a plurality of data lines crossing the plurality of gate lines, And a plurality of pixels in the form of a matrix including a plurality of pixels formed in a region where the plurality of gate lines cross the plurality of data lines and a driving transistor for supplying current to each of the plurality of organic light emitting elements, An initialization step of applying a control ON signal and a gate ON signal to the plurality of control lines and the plurality of gate lines to charge a data voltage and a bias voltage to first and second capacitors connected to the driving transistor, Off signal to the control line of the driving transistor A threshold voltage compensating step of setting a threshold voltage of the driving transistor to a value obtained by adding a threshold voltage of the driving transistor to the voltage, a data writing step in which the data voltage applied through the plurality of data lines is distributed by the first and second capacitors, And a light emitting step of applying a control ON signal and a gate OFF signal to the control line and the plurality of gate lines, respectively, to turn on the driving transistor to supply a current to the organic electroluminescent device.

The bias voltage is a voltage applied to the reference voltage line.

The initialization step changes the path of the current supplied to the organic electroluminescent device to the reference voltage line to suppress the initial emission of the organic electroluminescent device.

The potential of the reference voltage line and the potential of the ground voltage line connected to the cathode of the organic electroluminescent device are kept at the same potential.

The driving transistor is a source follower.

The driving transistor is formed of any one selected from a P-type transistor, an N-type transistor, an amorphous silicon (a-Si), and an oxide film.

As described above, the driving circuit and the driving method of the organic light emitting display according to the present invention compensate for the threshold voltage and the mobility of the driving transistor, thereby providing the effect of minimizing short afterglow and luminance unevenness occurring during panel driving do.

1 is a view illustrating a driving circuit of an organic light emitting display according to an embodiment of the present invention.
2 is a timing chart of a driving circuit of an organic light emitting display according to an embodiment of the present invention.
3 is a view illustrating a driving circuit of an organic light emitting display according to another embodiment of the present invention.
4 is a timing chart of a driving circuit of an organic light emitting display according to another embodiment of the present invention.
5 illustrates a driving circuit of an organic light emitting display device according to another embodiment of the present invention.

Hereinafter, preferred embodiments of a driving circuit and a driving method of an organic light emitting display according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a view illustrating a driving circuit of an organic light emitting display according to an embodiment of the present invention.

Referring to FIG. 1, M x N unit pixels are defined on an array substrate, and each unit pixel is arranged in a matrix form.

Each unit pixel 110 includes a first transistor T11 through a fourth transistor T14 and first and second capacitors C11 and C12 and an organic light emitting diode OLED11.

The gate of the first transistor T11 is connected to the gate line GL, the source thereof is connected to the data line DL, the drain thereof is connected to the first node N11, and the data signal is outputted in accordance with the gate signal .

The source of the second transistor T12 is connected to the control line CL, the source of the second transistor T12 is connected to the power supply voltage line VDD, the drain of the second transistor T12 is connected to the second node N12, do.

The gate of the third transistor T13 is connected to the first node N11, the source is connected to the second node N12, the drain is connected to the third node N13, and the organic light emitting diode OLED11, Lt; / RTI >

The gate of the fourth transistor T14 is connected to the gate line GL, the source thereof is connected to the third node N13, and the drain thereof is connected to the reference voltage line VREF. At this time, for example, the ground voltage GND may be applied to the reference voltage line VREF.

One end of the first capacitor C11 is connected to the first node N11 and the other end is connected to the reference voltage terminal 16. [ One end of the second capacitor C12 is connected to the first node N11 and the other end is connected to the second node N12.

The anode of the organic electroluminescent device OLED11 is connected to the third node N13, and the cathode is connected to the ground voltage GND.

Here, the first to fourth transistors T11 to T14 have been described by taking a p-type transistor as an example, but they may be composed of an n-type transistor, an amorphous silicon (a-Si) and an oxide film.

The driving of the organic light emitting display according to one embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 2 is a timing diagram of a driving circuit of an organic light emitting display according to an exemplary embodiment of the present invention.

1 and 2, an organic light emitting display according to an embodiment of the present invention includes an initialization period A, a data write period B, and a light emission period C for one frame.

First, when a low level signal is applied to the control line CL and the gate line GL during the initialization period A, the second transistor T12 connected to the control line CL is turned on, The first transistor T11 connected to the gate line GL is turned on and the voltage of the second node N12 is equal to the power supply voltage VDD minus the threshold voltage Vth of the second transistor T12 Is initialized.

When a high level signal is applied to the control line CL and a low level signal is applied to the gate line GL during the data writing period B, The second transistor T12 is turned off, and the first transistor T11 connected to the gate line GL is kept turned on.

At this time, the voltage stored in the first capacitor C11 turns on the third transistor T13 and the voltage stored in the second capacitor C12 flows through the third node N13 to the source of the fourth transistor T14 And the fourth transistor T14 is turned on by the signal applied to the gate line GL so that the voltage stored in the second capacitor C12 is transferred to the reference voltage terminal Vref. At this time, the organic electroluminescent device OLED11 does not emit light.

Here, the voltage of the second node N12 is a value obtained by adding the threshold voltage of the third transistor T13 to the data voltage, and the data voltage is defined as a high level signal, for example, .

Also, the voltage of the second node N12 may be varied depending on the degree of mobility of the third transistor T13. If the mobility of the third transistor T13 is high, the voltage drop at the second node N12 quickly occurs and the mobility of the third transistor T13 is low, as in 'a' , The voltage drop at the second node N12 gradually occurs as shown by "b" in FIG.

Subsequently, for example, when a low level signal is applied to the control line CL and a high level signal is applied to the gate line GL during the light emission period C, The transistor T12 is turned on and the first transistor T11 and the fourth transistor T14 connected to the gate line GL are turned off.

The fourth transistor T14 is turned on by the voltage of the first node N11 and the power supply voltage VDD is supplied to the anode of the organic light emitting device OLED11 through the fourth transistor T14. And the organic electroluminescent device OLED11 emits light.

At this time, the voltage of the first node N11, that is, the voltage Vg applied to the gate of the fourth transistor T14, may be expressed by Equation (1).

[Equation 1]

In addition, the current I _OLED flowing through the organic light emitting diode OLED11 can be expressed by Equation (2).

&Quot; (2) "

Here, the current I _OLED flowing through the organic light emitting diode OLED11 may be expressed differently depending on the values of the first and second capacitors C11 and C12. If the value of the second capacitor C12 is larger than the value of the first capacitor C11, the current I _OLED flowing through the organic light emitting diode OLED11 can be expressed as K / 2. In addition, when the value of the second capacitor C12 is smaller than the value of the first capacitor C11, the current I _OLED flowing through the organic light emitting diode OLED11 can be expressed by Equation (3).

&Quot; (3) "

Here, K is represented by 1/2 占 · Cg 占 W / L, 占 p represents the mobility of the P-type transistor, and Cg represents the gate capacitance.

2, the mobility of the third transistor T13 is compensated for in the data write period B. However, the threshold voltage Vth of the third transistor T13 is not limited to the threshold voltage Vth of the third transistor T13, There is no compensating section for the deviation of < RTI ID = 0.0 > Accordingly, when an organic light emitting display device is driven, a short afterimage due to device characteristics may be induced. Thus, the mobility of the transistor and the deviation of the threshold voltage can be caused by laser scan irregularities in the process of laser crystallization during transistor formation.

In detail, the current I _OLED flowing through the organic light emitting diode OLED11 is very sensitive to the values of the first and second capacitors C11 and C12 as shown in Equation (2). The second capacitor C12 Is larger than the value of the first capacitor C11, the current I _OLED flowing through the organic light emitting diode OLED11 is expressed as K / 2, so that the image data information is lost and the gray level can not be expressed.

When the value of the second capacitor C12 is smaller than the value of the first capacitor C11, the current I _OLED flowing through the organic light emitting diode OLED11 is equal to the power source voltage VDD, There is no compensation period for the deviation of the threshold voltage of the third transistor T13. Actually, when the organic electroluminescent display device is driven, short-term afterimage due to device characteristics and image quality unevenness in a low gradation region are generated.

In order to solve the above problems, the organic light emitting display device according to another embodiment of the present invention further includes a threshold voltage compensation period after an initialization period in one frame. A detailed description thereof will be described with reference to FIG.

3 is a view illustrating a driving circuit of an organic light emitting display according to another embodiment of the present invention.

Referring to FIG. 3, each unit pixel 210 according to another embodiment of the present invention includes a first transistor T21 to a fourth transistor T24, first and second capacitors C21 and C22, And a light emitting element OLED21.

The gate of the first transistor T21 is connected to the gate line GL to which the gate signal is applied and the gate of the first transistor T21 is connected to the data line DL to which the data signal is applied, And is turned on according to a gate signal to output a data signal.

The gate of the second transistor T22 is connected to the control line CL to which the control signal is applied, the source thereof is connected to the power source voltage VDD, the drain thereof is connected to the first node N21, And outputs the power supply voltage.

The gate of the third transistor T23 is connected to the gate line GL, the source thereof is connected to the reference voltage line VREF to which the reference voltage is applied, the drain thereof is connected to the second node N22, Thereby outputting the reference voltage.

The gate of the fourth transistor T24 is connected to the second node N22, the source of the fourth transistor T24 is connected to the first node N21, the drain of the fourth transistor T24 is connected to the anode of the organic light emitting diode OLED21, Thereby providing a current for driving the OLED 21.

One end of the first capacitor C21 is connected to the drain of the first transistor T21 and the other end is connected to the first node N21 to store the data signal.

One end of the second capacitor C22 is connected to the first node N11 and the other end is connected to the second node N22 to provide a constant bias voltage to the gate of the fourth transistor T24.

The anode of the organic electroluminescent device OLED11 is connected to the drain of the fourth transistor T24, and the cathode is connected to the ground voltage GND.

The driving of the organic light emitting display according to another embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 4 is a timing diagram of a driving circuit of an organic light emitting display according to another embodiment of the present invention.

3 and 4, an organic light emitting display according to another exemplary embodiment of the present invention includes an initialization period A ', a threshold voltage compensation period B', a data write period C ' And a light emitting section D '.

First, when a low level signal is applied to the gate line GL and the control line CL during the initialization period A ', the first and third transistors T21 and T23 connected to the gate line GL turn And the second transistor T22 connected to the control line CL is turned on.

The first transistor T21 is turned on to charge the first capacitor C21 and the third transistor T23 is turned on to apply a bias voltage or a reference voltage to the second capacitor C22. do. When the second transistor T22 is turned on and a voltage higher than the second node N22 is applied to the first node N21, for example, the power source voltage VDD is applied, the fourth transistor T24 is turned So that the organic electroluminescent device OLED 21 emits light initially.

Then, a low level signal is applied to the gate line GL during the threshold voltage compensation period B ', so that the first and third transistors T21 and T23 connected thereto are kept turned on, The high level signal is applied to the second transistor CL and the second transistor T22 connected thereto is turned off.

At this time, the second transistor T22 is turned off so that the first node N21 is in a floating state, the power supply voltage VDD is not applied, and the self-operation of the fourth transistor T24 is performed. The voltage of the first node N21 is set to a value VREF + | Vth | obtained by adding the threshold voltage of the fourth transistor T24 to the reference voltage. At this time, assuming that the reference voltage is, for example, 0V, the voltage of the first node N21 actually has the threshold voltage of the fourth transistor T24. Here, the organic electroluminescent device OLED11 does not emit light.

During the data write period C ', a low level signal is applied to the gate line GL so that the first and third transistors T21 and T23 remain in the turn-on state, and the control line CL is maintained at the high level A signal is applied so that the second transistor T22 also maintains a turn-off state. At this time, the data voltage of the high level signal is applied to the data line DL, and the applied data voltage is distributed by the first and second capacitors C11 and C12, Can be expressed as Equation (4).

&Quot; (4) "

Here, Vint represents a pre-charge voltage E ', at which time the precharge voltage E' may have a value between a minimum value and a maximum value of the data voltage, That is, the first node N21, which is discharged according to the mobility of the fourth transistor T24 in the first transistor T24, and the mobility deviation of the fourth transistor T24 is compensated by Equation (4) can do.

When a low level signal is applied to the control line CL and a high level signal is applied to the gate line GL during the light emission period D ' The transistor T22 is turned on and the first transistor T21 and the third transistor T23 connected to the gate line GL are turned off.

Then, the fourth transistor T24 is turned on by the voltage stored in the second capacitor C22, that is, the voltage of the second node N22, and the power supply voltage VDD is turned on through the fourth transistor T24, Is applied to the anode of the light emitting device OLED 21, and the organic electroluminescence device OLED 21 emits light. At this time, the second transistor T22 is turned on, so that the voltage of the first node N21 rises to the power supply voltage VDD. As a result, the voltage of the second node N22 rises Can be expressed as Equation (5).

&Quot; (5) "

Here, when the organic light emitting diode OLED emits light, the voltage of the first node N21 rises to the power supply voltage VDD. In order to maintain the amount of charge in the second capacitor C22, And the voltage value of the second node N22.

When the organic light emitting diode OLED 22 emits light, the difference between the source node and the gate node of the fourth transistor T24, that is, the difference between the first node N21 and the second node N22, Can be expressed.

&Quot; (6) "

Finally, the saturation current I _OLED can be expressed as Equation 7. At this time, the threshold voltage Vth of the fourth transistor T24 and the power supply voltage VDD are erased and the data voltage, A pre-charge voltage Vint, and a ratio of the first and second capacitors C21 and C22. Here, the deviation of the mobility of the fourth transistor T24 can be compensated for by? V.

&Quot; (7) "

As described above, in another embodiment of the present invention, the third transistor T23 is connected between the reference voltage line VREF and the fourth transistor T24 in order to implement the fourth transistor T24 as a source follower. And a constant bias voltage is applied to the gate of the fourth transistor T24 from the initial portion A 'to the data write portion C'.

In another exemplary embodiment of the present invention, the third transistor T23 is disposed between the reference voltage line VREF and the fourth transistor T24, and the third transistor T23 is disposed between the initialization period A 'and the threshold voltage compensation period B' 1 data can be written while the drain of the first transistor T21 of the capacitor C21 is maintained at a predetermined voltage.

In another embodiment of the present invention, a node and data writing operation connected to the drain of the first transistor T21 and one end of the first capacitor C21 may be implemented using a single data line.

 In another embodiment of the present invention, as shown in Equation (7), since the power supply voltage VDD is erased when the organic light emitting diode OLED 22 emits light and is independent of the power supply voltage VDD, drop can be compensated for.

In another embodiment of the present invention, a threshold voltage compensation period B 'exists between the initialization period A' and the data writing period C 'as shown in FIG. 4, It is possible to minimize the short-term afterimage and unevenness in image quality in the low gradation region.

In another embodiment of the present invention, each unit pixel structure is simple, thereby improving the aperture ratio of the organic light emitting display device, thereby improving the lifetime of the organic light emitting display device, and improving the yield in manufacturing the substrate .

In addition, according to another embodiment of the present invention, the number of control signals for controlling the transistors in each unit pixel is small, so that the gate driver can be simply designed. As a result, an organic electroluminescent display having a narrow bezel Device can be implemented.

However, when the second transistor T22 is turned on in the initialization period A 'and a voltage higher than the second node N22 is applied to the first node N21, the fourth transistor T24 is turned on, There is a problem that the electroluminescent element OLED 21 emits light.

In order to solve the above problems, another embodiment of the present invention further includes a transistor for suppressing the emission of the OLED 21 in the initialization period A 'of the circuit of the organic electroluminescent device .

5 is a view illustrating a driving circuit of an organic light emitting display according to another embodiment of the present invention.

5, each unit pixel 310 according to another embodiment of the present invention includes a first transistor T31 to a fifth transistor T35, first and second capacitors C31 and C32, And an electroluminescent element OLED31.

Here, the first to fourth transistors T31 to T34 and the first and second capacitors C31 and C32 have the same structure as the other embodiments of the present invention.

In another embodiment of the present invention, a fifth transistor T35 is additionally provided in the circuit of the organic electroluminescent element to suppress the emission of the organic electroluminescent element OLED31 in the initialization period A '.

The gate of the fifth transistor T35 is connected to the gate line GL and is turned on by applying a predetermined voltage from the gate line GL. The source of the fifth transistor T35 is connected to the reference voltage line VREF, And is connected to one end of the electroluminescent element OLED31, that is, the anode.

In addition, driving the organic light emitting display according to another embodiment of the present invention is the same as driving the organic light emitting display according to another embodiment of the present invention.

However, in another embodiment of the present invention, the fifth transistor T35 is further turned on during the initialization period A 'to suppress the light emission of the organic light emitting diode OLED31.

In detail, when a low level signal is applied to the gate line GL and the control line CL during the initialization period A ', the first transistor T31 and the third transistor T31, which are connected to the gate line GL, T33 and fifth transistor T35 are turned on and the second transistor T32 connected to the control line CL is turned on.

The third transistor T33 is turned on and a low level signal is applied to the second node N32 to turn on the fourth transistor T34 so that the current I _OLED flows through the second transistor T32, The fourth transistor T34 and the fifth transistor T35 to the reference voltage line VREF. Accordingly, the voltage of the reference voltage line VREF and the ground voltage GND connected to the cathode of the organic electroluminescence device OLED31 can be maintained at the same potential of 0V. Accordingly, the current I _OLED applied to the anode of the organic light emitting diode _OLED 31 can be reduced. Therefore, the current I _OLED applied to the anode of the organic electroluminescent device _OLED 31 is reduced, and the emission of the organic electroluminescent device _OLED 31 can be suppressed.

While a great many are described in the foregoing description, it should be construed as an example of preferred embodiments rather than limiting the scope of the invention. Accordingly, the invention is not to be determined by the embodiments described, but should be determined by equivalents to the claims and the appended claims.

CL: control line GL: gate line
DL: Data line VREF: Reference voltage line
T11, T21, T31: first transistor T12, T22, T32:
T13, T23, T33: third transistor T14, T24, T34: fourth transistor
T35: fifth transistor C11, C21, C31: first capacitor
C12, C22, C32: the second capacitor
OLED 11, OLED 21, OLED 31: Organic electroluminescent device

Claims (16)

A driving circuit of an organic light emitting display device for controlling a current supplied to an organic electroluminescent device,
A first transistor having a gate connected to a gate line to which a gate signal is applied, a source connected to a data line to which a data signal is applied, and outputting the data signal according to the gate signal;
A gate connected to the gate line, a source connected to a reference voltage line to which a reference voltage is applied, and a second transistor outputting the reference voltage in accordance with the gate signal;
A gate connected to a control line to which a control signal is applied, a source connected to a power supply voltage line for applying a power supply voltage, and a third transistor for outputting the power supply voltage in accordance with the control signal;
A first capacitor connected at one end to a drain of the first transistor and at the other end to a drain of the third transistor, the first capacitor storing the data signal;
A fourth transistor connected to a drain of the second transistor, a source connected to a drain of the third transistor, and providing a current for driving the organic electroluminescent device;
A second capacitor connected at one end to the drain of the third transistor and at the other end to the drain of the second transistor and providing a constant bias voltage to the gate of the fourth transistor; And
An anode connected to a drain of the fourth transistor, and a cathode connected to a ground voltage line to which a ground voltage is applied, and an organic electroluminescent device. The method according to claim 1,
Wherein a data voltage is applied to a source of the first transistor, a reference voltage is applied to a source of the second transistor, and a source voltage is applied to a source of the third transistor. The method according to claim 1,
When a gate ON signal is applied to the gates of the first and second transistors and a control ON signal is applied to the gate of the third transistor to turn on the first to third transistors, Is higher than the drain voltage of the second transistor. The method according to claim 1,
A gate on signal is applied to the gates of the first and second transistors and a control off signal is applied to the gate of the third transistor to turn on the first and second transistors and turn off the third transistor Wherein a drain voltage of the third transistor is set to a reference voltage plus a threshold voltage of the fourth transistor. The method according to claim 1,
A gate connected to the gate line, a source connected to the reference voltage line, a drain connected to a drain of the fourth transistor, and a fifth transistor for suppressing initial light emission of the organic electroluminescent device And a driving circuit for driving the organic light emitting display. 6. The method of claim 5,
A gate off signal is applied to the gates of the first and second transistors and a control ON signal is applied to the gate of the third transistor so that the first and second transistors are turned off and the third transistor is turned on Wherein a current for driving the organic electroluminescent device passes through the second transistor, the fourth transistor, and the fifth transistor to the reference voltage line. The method according to claim 6,
Wherein the potential of the reference voltage line and the potential of the ground voltage line connected to the cathode of the organic electroluminescent device are kept at the same potential. The method according to claim 1,
And the fourth transistor is a source follower. The method according to claim 1,
Wherein the first to fourth transistors are formed of a P-type transistor, an N-type transistor, an a-Si, and an oxide. The method according to claim 1,
Wherein the reference voltage is a ground voltage. A plurality of gate lines, a plurality of data lines formed to intersect the plurality of gate lines, a plurality of data lines formed in a region where the plurality of gate lines and the plurality of data lines cross each other, An organic light emitting display including a plurality of pixels in a matrix form including a driving transistor for supplying a current to an organic electroluminescent device,
An initialization step of applying a control ON signal and a gate ON signal to the plurality of control lines and the plurality of gate lines to charge the data voltage and the bias voltage to the first and second capacitors connected to the driving transistor;
A threshold voltage compensating step of applying a control off signal to the plurality of control lines to set a source voltage of the driving transistor to a reference voltage plus a threshold voltage of the driving transistor;
A data writing step in which the data voltage applied through the plurality of data lines is distributed by the first and second capacitors; And
And a light emitting step of applying a control ON signal and a gate OFF signal to the plurality of control lines and the plurality of gate lines to turn on the driving transistor to supply a current to the organic electroluminescent device A method of driving an organic electroluminescent display device. 12. The method of claim 11,
Wherein the bias voltage is a voltage applied to the reference voltage line. 12. The method of claim 11,
Wherein the initialization step changes the path of the current supplied to the organic electroluminescent device to the reference voltage line to suppress the initial light emission of the organic electroluminescent device. 14. The method of claim 13,
Wherein a potential of the reference voltage line and a potential of a ground voltage line connected to the cathode of the organic electroluminescent device are maintained at the same potential. 12. The method of claim 11,
Wherein the driving transistor is a source follower. ≪ Desc / Clms Page number 20 > 12. The method of claim 11,
Wherein the driving transistor is formed of any one selected from the group consisting of a P-type transistor, an N-type transistor, an amorphous silicon (a-Si), and an oxide film.

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