KR20130051149A - Organic light emitting diode display device and method of driving the same - Google Patents

Abstract

PURPOSE: An organic light emitting display device and a driving method thereof are provided to improve an MPRT(Motion Picture Response Time) property by compensating a high potential voltage in real time. CONSTITUTION: A first transistor(T1) is connected to a high potential voltage terminal, a control line and a second node. A second transistor(T2) is connected to a first node, a scan line and a data line. A fourth transistor(T4) is connected to a third node, an initialization line, and a second reference voltage line. A fifth transistor is connected to the third node, a light emission control line, and an anode electrode of a light emitting diode. A first capacitor(Cst) is connected between the first node and the second node. A second capacitor(Cm) is connected to the second node and a high potential voltage terminal. The light emitting diode is connected to a drain electrode of a fifth transistor and a low potential voltage terminal.

Description

Organic light emitting diode display and its driving method {ORGANIC LIGHT EMITTING DIODE DISPLAY DEVICE AND METHOD OF DRIVING THE SAME}

The present invention relates to an organic light emitting diode display and a driving method thereof, and more particularly, to an organic light emitting diode capable of reducing the loss of compensation of a threshold voltage and a compensation of a high potential voltage and correcting mobility of the driving transistor. A display device and a driving method thereof.

Recently, as the information society develops, the demand for the display field is increasing in various forms, and in response, various flat panel display devices, for example, liquid crystal, which have features such as thinning, light weight, and low power consumption BACKGROUND Liquid crystal display devices, plasma display panel devices, organic light emitting diode display devices, and the like have been studied.

An organic light emitting diode display device is a display device that emits light by using an organic compound that emits red (R), green (G), and blue (B) light on a transparent substrate. OLED panel and driving circuit are included.

Therefore, the organic light emitting diode display does not require a separate light source, unlike a liquid crystal display device.

As a result, there is no need for a backlight unit, so the manufacturing process is simpler than that of a liquid crystal display and the manufacturing cost can be reduced.

In addition, the organic light emitting diode display device has not only an excellent viewing angle and a contrast ratio, but also a direct current low voltage drive, a fast response speed, strong external shock, and a wide temperature range.

In particular, in an active matrix type, a voltage controlling the current applied to the pixel region is charged in a storage capacitor, and the voltage is maintained until the next frame signal is applied. It is driven to maintain the light emitting state while one screen is displayed regardless of the number of gate wirings.

Therefore, in the active matrix system, the same luminance is achieved even when a low current is applied, which has the advantage of low power consumption and large size.

FIG. 1 is a view schematically showing an equivalent circuit of a pixel region of a conventional organic light emitting diode display, and FIG. 2 is a timing diagram showing a plurality of control signals supplied to a conventional organic light emitting diode display.

As shown in FIG. 1, first to fifth transistors T1 to T5, a driving transistor Tdr, a storage capacitor Cst, and a light emitting diode Del are formed in each pixel area P of FIG. 1. .

The first to fifth transistors T1 to T5 and the driving transistor Tdr may be P-type transistors.

The source electrode and the gate electrode of the first transistor T1 are respectively connected to the data line DL and the first scan line GL, and the drain electrode of the first transistor T1 is one end of the storage capacitor Cst. It is connected to one node N1.

The first transistor T1 is turned on according to the first scan signal S1 supplied through the first scan line GL to apply the data voltage DATA to the first node N1. It serves as a switching transistor.

The source electrode and the gate electrode of the second transistor T2 are connected to the first node N1 and the light emission control wiring EL, respectively, and the drain electrode of the second transistor T2 is connected to the reference voltage wiring.

The second transistor T2 is turned on according to the emission control signal Em supplied through the emission control line EL to supply the reference voltage Vref to the first node N1. Play a role.

The source electrode and the gate electrode of the third transistor T3 are respectively connected to the second node N2 and the first scan wiring GL, which are the other ends of the storage capacitor Cst, and the drain electrode of the third transistor T3 is It is connected to the drain electrode of the driving transistor Tdr.

The source electrode and the gate electrode of the fourth transistor T4 are connected to the drain electrode and the emission control wiring EL of the driving transistor Tdr, respectively, and the drain electrode of the fourth transistor T4 is an anode of the light emitting diode Del. It is connected to the third node N3 which is an electrode.

The source electrode and the gate electrode of the fifth transistor T5 are connected to the reference voltage wiring VL and the second scan wiring SL, respectively, and the drain electrode of the fifth transistor T5 is connected to the third node N3. do.

The source electrode and the gate electrode of the driving transistor Tdr are connected to the high potential voltage ELVDD terminal and the second node N2, respectively, and the drain electrode of the driving transistor Tdr is connected to the drain electrode of the third transistor T3. Connected.

While the driving transistor Tdr is turned on, current flows to the light emitting diode Del so that the light emitting diode Del emits light.

In this case, the intensity of light emitted by the light emitting diode Del is proportional to the amount of current flowing through the light emitting diode Del, and the amount of current flowing through the light emitting diode Del is applied to the gate electrode of the driving transistor Tdr. It is proportional to the magnitude of the voltage DATA.

As a result, the organic light emitting diode display may display an image by applying different data voltages DATA to each pixel area P to display different gray levels.

The storage capacitor Cst is connected between the first node N1 and the second node N2 and maintains the data voltage DATA for one frame to maintain a constant amount of current flowing through the light emitting diode Del. And it serves to keep the gray level displayed by the light emitting diode (Del) constant.

Hereinafter, the operation of the pixel area of the conventional organic light emitting diode display as described above will be described.

As shown in Fig. 2, during the first time t1, the high level first scan signal S1 is applied, the low level second scan signal S2 and the low level light emission control signal Em Are applied respectively.

Accordingly, the fifth transistor T5 is turned on and initializes the third node N3 to the reference voltage Vref. At this time, the second transistor T2 and the fourth transistor T4 are turned on.

Here, the voltage difference between the third node N3 and the ground GND may be equal to or less than the threshold voltage Vth of the light emitting diode Del. As a result, a current through the light emitting diode Del is generated during the first time t1. Does not flow.

During the second time t2, the first scan signal S1 is applied while changing from the high level to the low level, the second scan signal S2 of the low level is applied, and the emission control signal Em is at the low level. It is applied while changing from high level to.

As a result, the first transistor T1 and the third transistor T3 are turned on and are turned on using the off delay time of the fourth transistor T4 and the second node N2 and the third node N3. Is initialized to the reference voltage Vref. In this case, since the fifth transistor T5 maintains a turn-on state, the third node N3 maintains the reference voltage Vref.

Therefore, since the voltage of the third node N3 maintains the reference voltage Vref, a non-light emitting state in which no current flows through the light emitting diode Del is maintained even during the second time t2.

During the third time t3, the low level first scan signal S1, the low level second scan signal S2, and the high level emission control signal Em are applied.

Therefore, the threshold voltage Vth of the driving transistor Tdr is stored in the storage capacitor Cst. In this case, the fourth transistor T4 maintains a turn-off state and the third node N3 maintains a reference voltage Vref.

During the fourth time t4, the emission control signal Em is applied while changing from the high level to the low level, and the first scan signal S1 and the second scan signal S2 change from the low level to the high level. Is approved.

As a result, the second transistor T2 and the fourth transistor T4 are turned on, and the first transistor T1, the third transistor T3, and the fifth transistor T5 are turned off. (Turn-Off), the light emitting diode Del emits light for one frame.

The pixel region of the organic light emitting diode display device is driven while compensating the threshold voltage Vth and the high potential voltage VDD of the driving transistor Tdr through repetition of the first to fourth times t1 to t4.

In this case, the current I _OLED flowing through the light emitting diode Del is defined as in Equation 1.

[Equation 1]

Here, k is a proportional constant that is determined by the structure and physical characteristics of the driving transistor Tdr, and the mobility of the driving transistor Tdr and the channel width W and channel length of the driving transistor Tdr. It can be determined by the ratio (W / L) of (L).

That is, the current I _OLED flowing through the light emitting diode Del in the pixel region of the conventional organic light emitting diode display device is independent of the variation of the threshold voltage Vth and the high potential voltage VDD of the driving transistor Tdr. It may be determined by the data voltage DATA and the reference voltage Vref.

However, there is a problem in that the high potential voltage VDD is not compensated for when the organic light emitting diode display having the pixel structure performs 3D co-emission.

Thus, the current I _OLED flowing through the light emitting diode Del is defined as in Equation 2.

&Quot; (2) "

Therefore, when the organic light emitting diode display having the conventional pixel structure performs 3D co-emission driving, the high potential voltage VDD is increased due to the deviation between the _{sensing high} potential voltage VDD _sensing and the emission high potential voltage VDD _emission . Not compensated.

Here, the sensing high potential voltage VDD _sensing is a voltage reflecting a sensing error occurring when sensing the threshold voltage Vth of the driving transistor Tdr, and the light emitting high potential voltage VDD _emission is a value of the light emitting diode Del. The voltage supplied at the time of light emission.

That is, since a sensing error occurs during sensing of the threshold voltage Vth of the driving transistor Tdr, the sensing high potential voltage VDD _sensing is different from the light _{emission high} potential voltage VDD _emission . The deviation between the VDD _sensing and the light _{emission high} potential voltage affects the light emission of the light emitting diode Del.

In addition, as the threshold voltage sensing and data writing are simultaneously performed during the third time t3, there is a problem in that a compensation time is insufficient due to a lack of sensing time during high-speed driving.

The present invention is to solve the above problems, an organic light emitting diode display and a driving method thereof capable of correcting the mobility of the driving transistor by reducing the compensation of the threshold voltage and the compensation of the high potential voltage of the driving transistor The purpose is to provide.

An organic light emitting diode display for achieving the above object includes a scan wiring and a data wiring formed to cross each other; A first transistor connected to the high potential voltage terminal and the control wiring and the second node; A second transistor connected to a first node, the scan wiring and the data wiring; A third transistor connected to the first node, an initialization line, and a first reference voltage line; A fourth transistor connected to a third node, the initialization line, and the second reference voltage line; A fifth transistor connected to the third node, an emission control wiring, and an anode electrode of the light emitting diode; A first capacitor coupled between the first node and the second node; A second capacitor connected to the high potential voltage terminal and the second node; And a light emitting diode connected to the drain electrode and the low potential voltage terminal of the fifth transistor, wherein the first node to the third node are nodes connected to the gate electrode, the source electrode, and the drain electrode of the driving transistor, respectively. It is done.

The third transistor may be turned on according to an initialization signal supplied through the initialization line to initialize the first node to a first reference voltage.

The first reference voltage may be higher than a threshold voltage of the driving transistor.

In addition, the second reference voltage supplied through the second reference voltage line is preferably lower than the threshold voltage of the light emitting diode.

Meanwhile, the capacitance Cst of the first capacitor and the capacitance Cm of the second capacitor may be values satisfying Cst / (Cst + Cm) = 0.2.

The fourth transistor may be connected to the third node, the initialization line, and the low potential voltage terminal.

A method of driving an organic light emitting diode display according to a first embodiment of the present invention for achieving the above object includes a first to fifth transistor, a first and a second capacitor, a driving transistor and a light emitting diode. A method of driving an organic light emitting diode display, wherein the first node is connected to a first node while the third transistor and the fourth transistor are turned on by an initialization signal and the fifth transistor is turned on by an emission control signal. A first step of initializing to a reference voltage; A second step of sensing a threshold voltage of the driving transistor while the third transistor and the fourth transistor are turned off and the fifth transistor is turned on; Storing a data voltage in the first capacitor while the second transistor is turned on by a scan signal; While the first transistor is turned on by a control signal, supplying a high potential voltage to a second node to boost a voltage across the first node above a threshold voltage of the driving transistor; And a fifth step in which the light emitting diode emits light while the first transistor and the driving transistor are turned on and the fifth transistor is turned on by the light emission control signal.

Here, during the first step, the voltage applied to the second node may decrease as the threshold voltage of the driving transistor is sensed.

The first reference voltage may be higher than a threshold voltage of the driving transistor.

In addition, a second reference voltage may be supplied while the fourth transistor is turned on.

The second reference voltage is preferably lower than the threshold voltage of the light emitting diode.

Meanwhile, the voltage change amount α according to the first sensing error occurring during the first step and the voltage change amount β according to the second sensing error occurring during the second step may satisfy α = 4β.

In addition, the capacitance Cst of the first capacitor and the capacitance Cm of the second capacitor are preferably values satisfying Cst / (Cst + Cm) = 0.2.

In addition, a low potential voltage may be supplied while the fourth transistor is turned on.

According to another aspect of the present invention, there is provided a method of driving an organic light emitting diode display device including first to fifth transistors, first and second capacitors, a driving transistor, and a light emitting diode. A method of driving an organic light emitting diode display, wherein the first node is connected to a first node while the third transistor and the fourth transistor are turned on by an initialization signal and the fifth transistor is turned on by an emission control signal. A first step of initializing to a reference voltage; A second step of sensing a threshold voltage of the driving transistor while the third transistor and the fourth transistor are turned off and the fifth transistor is turned on; While the first transistor is turned on by a control signal, supplying a high potential voltage to a second node to boost a voltage across the first node above a threshold voltage of the driving transistor; A fifth step of causing the light emitting diode to emit light while the first transistor and the driving transistor are turned on and the fifth transistor is turned on by the light emission control signal; And a sixth step of sensing the mobility of the driving transistor between the second step and the fourth step.

As described above, in the organic light emitting diode display and the driving method thereof according to the present invention, the mobility of the driving transistor is corrected by reducing the compensation of the threshold voltage of the driving transistor and the loss of the compensation of the high potential voltage. It is possible to effectively reduce the luminance deviation caused by.

In addition, the frame holding may be improved by compensating the high potential voltage in real time, and the motion picture response time (MPRT) characteristics may be improved.

1 is a view schematically showing an equivalent circuit of a pixel area of a conventional organic light emitting diode display.
2 is a timing diagram illustrating a plurality of control signals supplied to a conventional organic light emitting diode display.
3 is a schematic view of an organic light emitting diode display according to the present invention.
FIG. 4 is a diagram schematically showing an equivalent circuit of a pixel region of an organic light emitting diode display according to a first embodiment of the present invention.
FIG. 5 is a timing diagram illustrating a plurality of control signals supplied to the organic light emitting diode display according to the first embodiment of the present invention, voltage changes of the first and second nodes, and current changes of the current flowing through the light emitting diodes. .
FIG. 6 schematically illustrates an equivalent circuit of a pixel area of an organic light emitting diode display according to a second exemplary embodiment of the present invention.
FIG. 7 is a timing diagram illustrating a plurality of control signals supplied to an organic light emitting diode display according to a third exemplary embodiment of the present invention, voltage changes of first and second nodes, and current changes of current flowing through the light emitting diodes. .
FIG. 8 is a diagram referred to describe threshold voltage compensation characteristics of a driving transistor in a pixel area of an organic light emitting diode display according to a first exemplary embodiment of the present invention.
FIG. 9 is a diagram referred to describe mobility compensation characteristics of a driving transistor in a pixel area of an organic light emitting diode display according to a first exemplary embodiment of the present invention.
FIG. 10 is a diagram referred to for describing a high potential voltage compensation characteristic in a pixel area of an organic light emitting diode display according to a first exemplary embodiment of the present invention.
FIG. 11 is a diagram illustrating a current deviation according to data voltages in a pixel area of the organic light emitting diode display device according to the first and second embodiments of the present invention.
FIG. 12 is a diagram illustrating a current deviation according to a data voltage in a pixel area of an organic light emitting diode display according to a third exemplary embodiment of the present invention.

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

3 is a view schematically showing an organic light emitting diode display according to the present invention, and FIG. 4 is a view schematically showing an equivalent circuit of a pixel region of the organic light emitting diode display according to the first embodiment of the present invention. .

3 and 4, the organic light emitting diode display 100 according to the present invention includes a display panel 110, a source driver 120, a scan driver 130, and a source driver for displaying an image. The timing controller 140 may control driving timing of the 120 and the scan driver 130, respectively.

The display panel 110 includes a plurality of scan lines GL1 to GLm and a plurality of data lines DL1 to DLn and a plurality of light emission control lines EL1 to ELm that cross each other to define a plurality of pixel regions P. ) May be included.

In addition, a plurality of initialization wires IL and a plurality of control wires CTL for supplying a control signal for controlling each pixel area P may be formed to be spaced apart in parallel with the plurality of scan wires GL1 to GLm. Can be.

Since each pixel area P has the same configuration, hereinafter, for convenience, a plurality of scan wires GL1 to GLm are referred to as scan wires GL, and the first to nth data wires DL1 to DLn are referred to as data wires DL. ), A plurality of light emission control wirings EL1 to ELm will be described as light emission control wirings EL.

Meanwhile, in each pixel area P, first to fifth transistors T1 to T5, a driving transistor Tdr, a first capacitor Cst, a second capacitor Cm, and a light emitting diode Del may be formed. have.

Here, the first to fifth transistors T1 to T5 and the driving transistor Tdr may be P-type transistors as shown, but are not limited thereto, and an N-type transistor may be applied.

The source electrode and the gate electrode of the first transistor T1 are connected to the high potential voltage ELVDD terminal and the control wiring CTL, respectively, and the drain electrode of the first transistor T1 is the source electrode of the driving transistor Tdr. It is connected to the second node N2.

The first transistor T1 is turned on according to the control signal Ctrl supplied through the control wiring CTL to supply the high potential voltage ELVDD to the second node N2.

The source electrode and the gate electrode of the second transistor T2 are respectively connected to the first node N1 and the scan wiring GL, which are one end of the storage capacitor Cst, and the drain electrode of the second transistor T2 is connected to the data wiring. Connected to (DL).

The second transistor T2 is turned on according to the scan signal S1 supplied through the scan line GL to supply the data voltage Vdata to the first node N1. do.

The source electrode and the gate electrode of the third transistor T3 are connected to the first node N1 and the initialization line IL, respectively, and the drain electrode of the third transistor T3 is connected to the first reference voltage line VL1. do.

The third transistor T3 is turned on according to the initialization signal Init supplied through the initialization line IL to supply the first reference voltage Vref_1 to the first node N1. Play a role.

The source electrode and the gate electrode of the fourth transistor T4 are connected to the third node N3, which is the drain electrode of the driving transistor Tdr, and the initialization wiring IL, respectively. 2 is connected to the reference voltage wiring (VL2).

The fourth transistor T4 is turned on according to the initialization signal Init supplied through the initialization line IL, and is the second reference voltage Vref_2 as the drain electrode of the fourth transistor T4. To supply.

Therefore, when the fourth transistor T4 is turned on, the current flowing to the light emitting diode Del is reduced.

Here, the second reference voltage Vref_2 may be a voltage lower than the threshold voltage Vth of the light emitting diode Del.

The source electrode and the gate electrode of the fifth transistor T5 are respectively connected to the third node N3 and the light emission control wiring EL, and the drain electrode of the fifth transistor T5 is connected to the anode electrode of the light emitting diode Del. Connected.

The fifth transistor T5 is turned on according to the emission control signal Em supplied through the emission control line EL to control the emission timing of the light emitting diode Del.

The source electrode and the gate electrode of the driving transistor Tdr are connected to the second node N2 and the first node N1, respectively, and the drain electrode of the driving transistor Tdr is connected to the third node N3.

The driving transistor Tdr controls the amount of current flowing through the light emitting diode Del, and the amount of current flowing through the light emitting diode Del is controlled by the data voltage Vdata applied to the gate electrode of the driving transistor Tdr. Proportional to size.

That is, the organic light emitting diode display may display an image by applying different data voltages to each pixel region P to display different gray levels.

The first capacitor Cst is connected between the first node N1 and the second node N2 and stores the voltage difference between the first node N1 and the second node N2.

The first capacitor Cst maintains a data voltage for one frame to maintain a constant amount of current flowing through the light emitting diode Del, and to maintain a constant gray level displayed by the light emitting diode Del. It may be a storage capacitor.

The second capacitor Cm is connected between the high potential voltage ELVDD terminal and the second node N2 and stores a voltage difference between the source electrode and the drain electrode of the first transistor T1.

The anode electrode of the light emitting diode Del is connected with the drain electrode of the fifth transistor T5, and the cathode electrode is connected with the low potential voltage ELVSS terminal.

The data driver 120 may include at least one driver IC (not shown) for supplying a data signal to the display panel 110.

The data driver 120 generates a data signal using the converted image signal R / G / B and the plurality of data control signals received from the timing controller 140, and converts the generated data signal into a data line DL. Supply to the display panel 110 through.

The timing controller 140 controls a plurality of video signals and a plurality of control signals such as a vertical synchronization signal VSY, a horizontal synchronization signal HSY, a data enable signal DE, and the like from a system such as a graphics card through an interface. Can be delivered.

In addition, the timing controller 140 may generate a plurality of data signals and supply the same to each driver IC of the data driver 120.

The scan driver 130 may generate a scan signal using the control signal received from the timing controller 140, and control the scan driver 130 to supply the generated scan signal to the display panel 110 through the scan line GL.

Hereinafter, the operation of the pixel area of the organic light emitting diode display as described above will be described.

FIG. 5 is a timing diagram illustrating a plurality of control signals supplied to the organic light emitting diode display according to the first embodiment of the present invention, voltage changes of the first and second nodes, and current changes of the current flowing through the light emitting diodes. .

As shown in Fig. 5, during the first time t1, the low level initialization signal Init and the high level control signal Ctrl are applied, and the low level light emission control signal Em and the high level are applied. Scan signals S1 may be applied.

Accordingly, the third transistor T3 is turned on so that the first node N1, which is the gate electrode of the driving transistor Tdr, is initialized to the first reference voltage Vref_1, and the driving transistor Tdr. The threshold voltage Vth of the driving transistor Tdr is sensed at the second node N2, which is a source electrode of.

The fourth transistor T4 is turned on to supply the second reference voltage Vref_2 to the drain electrode of the fourth transistor T4.

The second reference voltage Vref_2 applied to the drain electrode of the fourth transistor T4 may be a voltage lower than the threshold voltage Vth of the light emitting diode Del. (Vref_2 <Vth)

In addition, the fifth transistor T5 is turned on to connect the drain electrode of the driving transistor Tdr and the anode electrode of the light emitting diode Del.

At this time, the first transistor T1 and the second transistor T2 are turned off.

In more detail, since the first node N1 is initialized to the first reference voltage Vref_1 during the first time t1, the voltage difference Vgs between the gate electrode and the source electrode of the driving transistor Tdr is changed to the driving transistor. It becomes larger than the threshold voltage Vth of Tdr. (Vref_1> Vth)

Accordingly, the driving transistor Tdr is turned on until the voltage difference Vgs between the gate electrode and the source electrode reaches the threshold voltage Vth of the driving transistor Tdr, thereby driving the second node N2. As a result, the voltage V _N2 is lowered to 'Vref_1-Vth' which is a voltage difference between the first reference voltage Vref_1 and the threshold voltage Vth of the driving transistor Tdr.

Meanwhile, at the second node N2, a first sensing error may occur due to the channel resistance of the driving transistor Tdr during the first time t1, and the voltage V _N2 applied to the second node N2 at that time may occur. ) May be 'Vref_1-Vth + α' which is a voltage difference 'α' according to the first sensing error to 'Vref_1-Vth' which is a voltage difference between the reference voltage REF and the threshold voltage Vth.

The mobility of the driving transistor Tdr may be affected by the channel resistance of the driving transistor Tdr. For example, as the channel resistance of the driving transistor Tdr increases, the driving transistor Tdr is increased. ) Mobility can be lowered.

However, as the channel resistance of the driving transistor Tdr is increased, the voltage change amount α according to the first sensing error also increases, so that the mobility of the driving transistor Tdr is determined by the voltage change amount according to the first sensing error ( It can be said that it is affected by α).

Therefore, in the organic light emitting diode display 100 according to the present invention, the voltage change amount? According to the first sensing error according to the channel resistance of the driving transistor Tdr is sensed during the first time t1 and thus the second node is sensed. By controlling the voltage V _N2 to be 'Vref_1-Vth + α', the mobility of the driving transistor Tdr may be compensated for using the voltage V _N2 .

The voltage V _N1 applied to the first node N1 is the first reference voltage Vref_1 and the voltage V _N2 applied to the second node _N2 becomes 'Vref_1-Vth + α'.

On the other hand, when the driving transistor Tdr and the fourth transistor T4 are turned on at the same time during the first time t1, the second node N2 is moved toward the second reference voltage line VL2. A current path is formed so that the current I _OLED flowing through the light emitting diode Del is reduced.

During the second time t2, the high level initialization signal Init and the high level control signal Ctrl are applied, and the low level light emission control signal Em and the high level scan signal S1 are respectively applied. Can be applied.

As a result, as the third transistor T3 is turned off, the first node N1 is in a floating state, and the threshold voltage of the driving transistor Tdr is applied at the second node N2. Vth) is sensed.

At this time, the fifth transistor T5 is in a turn-on state, and the first transistor T1, the second transistor T2, and the fourth transistor T4 are in a turn-off state. to be.

Since the first node N1 floats during the second time t2, the first node N1 and the second node N2 are coupled by the first capacitor Cst to be coupled to the first node N1. The voltage V _N1 applied to the node N1 and the voltage V _N2 applied to the second node _N2 are gradually lowered.

Accordingly, a second sensing error may occur during the second time t2, and as a result, the voltage V _N2 applied to the second node N2 is equal to the threshold voltage of the first reference voltage Vref_1 and the driving transistor Tdr. It may be 'Vref_1-Vth-β' lowered by the voltage change amount β according to the second sensing error to the voltage difference of Vth.

The voltage V _N1 applied to the first node N1 is lowered to 'Vref_1-α-β' by reflecting the voltage change amount (−α−β) at the second node N2.

In this case, the degree of mobility correction of the driving transistor Tdr may be controlled by adjusting a time ratio between the first time t1 and the second time t2.

On the other hand, since the voltage applied to the third node N3 is maintained to be lower than the threshold voltage Vth of the light emitting diode Del, the non-light-emitting that no current flows through the light emitting diode Del during the second time t2. It becomes a state.

During the third time t3, the high level initialization signal Init and the high level control signal Ctrl are applied, and the high level emission control signal Em and the low level scan signal S1 are respectively applied. Can be applied.

Therefore, while the second transistor T2 is turned on, the second transistor T2 supplies the data voltage Vdata to the first node N1.

Here, the first transistor T1 and the third to fifth transistors T3 to T5 are in a turn-off state.

During the third time t3, the voltage V _N1 applied to the first node N1 is lowered to the data voltage Vdata, where the voltage change amount of the first node N1 is 'Vref_1-α-β-Vdata' Becomes

In addition, the voltage V _N2 applied to the second node N2 is reflected by the voltage change amount Vref_1-α-β-Vdata of the first node N1 by the first capacitor Cst, and thus 'Vref_1-Vth-'. β-C '(Vref_1-α-β-Vdata)'.

In this case, C 'is defined as in Equation 3, and Cst and Cm represent the capacitance of the first capacitor and the capacitance of the second capacitor, respectively.

&Quot; (3) &quot;

That is, since the voltage V _N2 applied to the second node N2 is changed according to the capacitance holding characteristic of the first capacitor Cst and the amount of voltage change is reflected at the ratio of C ′, the data voltage Vdata. To minimize the loss, it is necessary to design the capacity of the first capacitor Cst sufficiently large.

During the fourth time t4, the high level initialization signal Init and the low level control signal Ctrl are applied, and the high level emission control signal Em and the high level scan signal S1 are respectively applied. Can be applied.

As a result, the high potential voltage ELVDD is supplied to the second node N2 while the first transistor T1 is turned on.

Here, the second to fifth transistors T2 to T5 are in a turn-off state, and the driving transistor Tdr is in a turn-on state.

The voltage V _N2 applied to the second node N2 during the fourth time t4 becomes the high potential voltage ELVDD.

In addition, the threshold voltage Vth information and the high potential voltage ELVDD information of the driving transistor Tdr of the second node N2 are coupled to the first node through a coupling action of the second capacitor Cm. Is passed to (N1).

That is, the voltage V _N1 applied to the first node N1 is the amount of voltage change ELVDD- {Vref_1-Vth-β-C '(Vref_1-α) applied to the second node N1 by a coupling action. -[beta] -Vdata)}) becomes' Vdata + [ELVDD- {Vref_1-Vth-β-C '(Vref_1-α-β-Vdata)}]'.

During the fifth time t5, the high level initialization signal Init and the low level control signal Ctrl are applied, and the low level light emission control signal Em and the high level scan signal S1 are respectively applied. Can be applied.

As a result, while the fifth transistor T5 and the driving transistor Tdr are turned on, current flows to the light emitting diode Del, thereby making it a light emitting state.

Here, the second to fourth transistors T2 to T5 are in a turn-off state, and the first transistor T1 and the driving transistor Tdr are in a turn-on state.

The voltage V _N1 applied to the first node N1 during the fifth time t5 is 'Vdata + [ELVDD- {Vref_1-Vth-β-C' (Vref_1-α-β-Vdata)}], and The voltage across the two nodes N1 maintains the high potential voltage ELVDD.

The current I _OLED flowing through the light emitting diode Del may be defined as shown in Equation 4.

&Quot; (4) &quot;

Here, k is a proportional constant that is determined by the structure and physical characteristics of the driving transistor Tdr, and includes the mobility of the driving transistor Tdr and the channel width W of the driving transistor Tdr. It can be determined by the ratio (W / L) of the channel length (L).

In addition, C 'is defined by Equation 3 and the size of C' may be set to 0.2 by adjusting the capacitance of the first capacitor Cst and the capacitance of the second capacitor Cm.

In addition, α is the amount of change in voltage according to the first sensing error, β is the amount of change in voltage according to the second sensing error, α = 4β can be set if the first time t1 and the second time t2 is properly adjusted. have.

Substituting α = 4β in Equation 4 and deleting βC ′ * (α + β) and substituting C ′ = 0.2, Equation 5 may be defined.

[Equation 5]

As a result, the current I _OLED flowing through the light emitting diode Del during the fifth time t5 is independent of the threshold voltage Vth of the driving transistor Tdr, and the data voltage DATA and the first reference voltage Vref_1. Can be determined by.

On the other hand, in the case where the organic light emitting diode display is driving 3D co- _emission , the high potential voltage VDD is not compensated due to the deviation between the _{sensing high} potential voltage VDD _sensing and the light _{emission high} potential voltage VDD _emission . The current I _OLED flowing through the diode Del has a problem of being affected by the high potential voltage VDD as shown in Equation 2.

However, in the pixel area of the organic light emitting diode display according to the first embodiment of the present invention, a first capacitor Cst is formed at the first node N1 and the second node N1 to couple the first node N1 to a couple. Due to the coupling action, the high potential voltage ELVDD _sensing when sensing the threshold voltage Vth of the driving transistor Tdr and the ELVDD _emission when emitting light can reduce the deviation.

As a result, in the pixel area of the organic light emitting diode display according to the first exemplary embodiment of the present invention, the high potential voltage ELVDD may be compensated for when 3D simultaneous emission driving is performed.

In addition, since the voltage variation α according to the first sensing error due to the channel resistance of the driving transistor Tdr is also removed, the mobility of the driving transistor Tdr can be compensated.

In addition, the organic light emitting diode display according to the first embodiment of the present invention corrects the threshold voltage Vth, the high potential voltage ELVDD of the driving transistor Tdr, and corrects the mobility of the driving transistor Tdr. Therefore, the luminance variation due to the nonuniformity of the transistor can be effectively reduced.

In addition, the high potential voltage ELVDD may be compensated in real time to improve frame holding and motion picture response time (MPRT) characteristics.

FIG. 6 schematically illustrates an equivalent circuit of a pixel area of an organic light emitting diode display according to a second exemplary embodiment of the present invention. Since some configurations in the second embodiment of the present invention are substantially the same as the first embodiment of the present invention, the following description will focus on differences from the first embodiment of the present invention.

As shown in FIG. 6, the source electrode and the gate electrode of the fourth transistor T4 according to the second embodiment of the present invention are respectively the third node N3 and the initialization wiring (drain electrode) of the driving transistor Tdr. IL), and the drain electrode of the fourth transistor T4 is connected to the low potential voltage ELVSS terminal.

The fourth transistor T4 is turned on according to the initialization signal Init supplied through the initialization line IL, and the low potential voltage ELVSS is a drain electrode of the fourth transistor T4. This supply serves to reduce the current flowing to the light emitting diode (Del).

The low potential voltage ELVSS may be a voltage lower than the threshold voltage Vth of the light emitting diode Del.

That is, the voltage supplied to the drain electrode of the fourth transistor T4 may be lower than the threshold voltage Vth of the light emitting diode Del in order to reduce the current flowing to the light emitting diode Del. Instead of supplying (Vref_2), the potential voltage ELVSS is supplied.

Therefore, in the second embodiment of the present invention, the second reference voltage wiring (VL2 of FIG. 4) may be removed by connecting the drain electrode of the fourth transistor T4 to the low potential voltage ELVSS terminal.

The organic light emitting diode display according to the second embodiment of the present invention may also be driven according to the timing diagram according to the first embodiment of the present invention.

FIG. 7 is a timing diagram illustrating a plurality of control signals supplied to an organic light emitting diode display according to a third exemplary embodiment of the present invention, voltage changes of first and second nodes, and current changes of current flowing through the light emitting diodes. . Since some timings in the third embodiment of the present invention are substantially the same as the timings in the first embodiment of the present invention, the following description will focus on differences from the first embodiment of the present invention.

As shown in Fig. 7, during the sixth time t6, the high level initialization signal Init and the high level control signal Ctrl are applied, respectively, and the scan signal S1 goes from the high level to the low level. The light emission control signal Em may be applied while changing from a low level to a high level.

In the timing diagram of the third embodiment of the present invention, the mobility sensing period is added by changing the timing of applying the scan signal S1 (a predetermined time earlier).

Since the sensing currents are different for each of the data voltages Vdata corresponding to the gray scales implemented in each pixel area, when driving according to the timing diagram of the first embodiment of the present invention, the threshold voltages of the driving transistors Tdr are the same to all the gray scales. Vth) and the high potential voltage ELVDD cannot be compensated for.

Accordingly, in the timing diagram of the third exemplary embodiment of the present invention, the scan signal S1 changes from a high level to a low level, and at the same time, the emission control signal Em changes in mobility from a low level to a high level. 6 hours (t6) is added.

As a result, the mobility correction effect of the driving transistor Tdr of the driving transistor Tdr according to the data voltage Vdata may be improved.

The threshold voltage Vth and the high potential voltage ELVDD of the driving transistor Tdr may be compensated to the same degree for all gray levels.

The organic light emitting diode display according to the first and second embodiments of the present invention may be driven according to the timing diagram according to the third embodiment of the present invention.

FIG. 8 is a diagram for explaining threshold voltage compensation characteristics of a driving transistor in a pixel area of an organic light emitting diode display according to a first exemplary embodiment of the present invention, and FIG. 9 is an organic diagram according to the first exemplary embodiment of the present invention. 10 is a diagram illustrating a mobility compensation characteristic of a driving transistor in a pixel region of a light emitting diode display, and FIG. 10 is a high potential voltage compensation characteristic in a pixel region of an organic light emitting diode display according to a first embodiment of the present invention. It is a drawing referred to to explain.

In FIG. 8, the left figure shows threshold voltage compensation characteristics of a driving transistor in a pixel area of a conventional organic light emitting diode display, and the right figure shows a pixel area of an organic light emitting diode display according to a first embodiment of the present invention. Threshold voltage compensation characteristics of the driving transistor are shown.

As shown in FIG. 8, the threshold voltage compensation characteristic of the driving transistor in the pixel region of the organic light emitting diode display according to the first exemplary embodiment of the present invention has a threshold voltage (Vth) over several gray levels (31 to 255). It can be seen that the error of% is reduced.

For example, Error Vth (%) may vary from 1 to 9 in the pixel region of a conventional organic light emitting diode display, whereas Error Vth in the pixel region of the organic light emitting diode display according to the first embodiment of the present invention. (%) Is mostly 1 to 3.

9, the left figure shows the mobility compensation characteristics of the driving transistor in the pixel region of the conventional organic light emitting diode display, and the right figure shows the pixel region of the organic light emitting diode display according to the first embodiment of the present invention. The mobility compensation characteristics of the driving transistors are shown.

As shown in FIG. 9, the mobility compensation characteristic of the driving transistor in the pixel area of the organic light emitting diode display according to the first embodiment of the present invention is more mobility than the prior art. It can be seen that the error of% is reduced.

For example, the error mobility (%) is varied from 1 to 9 in the pixel area of the conventional organic light emitting diode display device below the gray level 127, whereas the organic light emitting diode display device according to the first embodiment of the present invention is Error mobility (%) is mostly 1 ~ 3 in the pixel area of.

In FIG. 10, the left figure shows the high potential voltage compensation characteristic in the pixel region of the conventional organic light emitting diode display, and the right figure shows the high potential in the pixel region of the organic light emitting diode display according to the first embodiment of the present invention. Voltage compensation characteristics.

As shown in FIG. 10, in the pixel area of the organic light emitting diode display according to the first exemplary embodiment of the present invention, the high potential voltage compensation characteristic has a high potential of It can be seen that the error (%) is reduced.

For example, when the high potential voltage ELVDD is 11 or more, the error VDD (%) varies from 1 to 9 in the pixel region of the conventional organic light emitting diode display, whereas the organic light emitting diode according to the first embodiment of the present invention In the pixel region of the LED display device, the error VDD (%) is mostly 1.

FIG. 11 is a diagram illustrating a current deviation according to data voltages in a pixel area of an organic light emitting diode display device according to first and second embodiments of the present invention, and FIG. 12 is a diagram illustrating an organic variation according to a third embodiment of the present invention. FIG. 5 is a diagram illustrating current deviation according to data voltage in a pixel area of a light emitting diode display.

As shown in FIG. 11, as the data voltage Vdata decreases in the pixel region of the organic light emitting diode display according to the first and second exemplary embodiments of the present invention, the reference current Ref and mobility are increased. It can be seen that the current deviation of the current (I _OLED ) at 15% increases.

For example, when the data voltage Vdata is 2, the current deviation between the reference current Ref and the current I _OLED when the mobility is 15% is about 300n.

As shown in FIG. 12, the reference current Ref and the mobility are 15% as the data voltage Vdata decreases in the pixel region of the organic light emitting diode display according to the third exemplary embodiment of the present invention. The current deviation of the current I _OLED at the time increases.

However, in the third embodiment of the present invention, when the data voltage Vdata is 2, the current deviation of the current I _OLED when the reference current Ref and the mobility is 15% is about 150n. .

That is, in the third embodiment of the present invention, the current deviation of the current I _OLED is reduced compared to the first and second embodiments.

The embodiments of the present invention as described above are merely illustrative, and those skilled in the art can make modifications without departing from the gist of the present invention. Accordingly, the protection scope of the present invention includes modifications of the present invention within the scope of the appended claims and equivalents thereof.

100: organic light emitting diode display 110: display panel
120: source driver 130: scan driver
140: timing controller
Tdr: driving transistor Del: light emitting diode

Claims (15)

Scan wiring and data wiring formed to cross each other;
A first transistor connected to the high potential voltage terminal and the control wiring and the second node;
A second transistor connected to a first node, the scan wiring and the data wiring;
A third transistor connected to the first node, an initialization line, and a first reference voltage line;
A fourth transistor connected to a third node, the initialization line, and the second reference voltage line;
A fifth transistor connected to the third node, an emission control wiring, and an anode electrode of the light emitting diode;
A first capacitor coupled between the first node and the second node;
A second capacitor connected to the high potential voltage terminal and the second node;
A light emitting diode connected to the drain electrode and the low potential voltage terminal of the fifth transistor,
And the first node to the third node are nodes connected to a gate electrode, a source electrode, and a drain electrode of the driving transistor, respectively.
The method of claim 1,
The third transistor,
And turn on the first signal to initialize the first node to the first reference voltage according to the initialization signal supplied through the initialization wiring.
The method of claim 2,
And the first reference voltage is higher than a threshold voltage of the driving transistor.
The method of claim 1,
And a second reference voltage supplied through the second reference voltage wire is lower than a threshold voltage of the light emitting diode.
The method of claim 1,
The capacitance Cst of the first capacitor and the capacitance Cm of the second capacitor are values satisfying Cst / (Cst + Cm) = 0.2.
The method of claim 1,
The fourth transistor,
And the third node, the initialization line, and the low potential voltage terminal.
A driving method of an organic light emitting diode display device comprising first to fifth transistors, first and second capacitors, a driving transistor, and a light emitting diode,
A first step of initializing a first node to a first reference voltage while the third transistor and the fourth transistor are turned on by an initialization signal and the fifth transistor is turned on by an emission control signal;
A second step of sensing a threshold voltage of the driving transistor while the third transistor and the fourth transistor are turned off and the fifth transistor is turned on;
Storing a data voltage in the first capacitor while the second transistor is turned on by a scan signal;
While the first transistor is turned on by a control signal, supplying a high potential voltage to a second node to boost a voltage across the first node above a threshold voltage of the driving transistor;
A fifth step in which the light emitting diode emits light while the first transistor and the driving transistor are turned on and the fifth transistor is turned on by the light emission control signal
Method of driving an organic light emitting diode display device comprising a.
The method of claim 7, wherein
During the first step,
And a voltage applied to the second node decreases as the threshold voltage of the driving transistor is sensed.
The method of claim 7, wherein
And the first reference voltage is higher than a threshold voltage of the driving transistor.
The method of claim 7, wherein
And a second reference voltage is supplied while the fourth transistor is turned on.
The method of claim 10,
And the second reference voltage is lower than a threshold voltage of the light emitting diode.
The method of claim 7, wherein
The amount of change in voltage (α) according to the first sensing error occurring during the first step and the amount of change in voltage (β) according to the second sensing error occurring during the second step satisfy α = 4β. Method of driving a diode display device.
The method of claim 7, wherein
The capacitance Cst of the first capacitor and the capacitance Cm of the second capacitor are values satisfying Cst / (Cst + Cm) = 0.2.
The method of claim 7, wherein
A low potential voltage is supplied while the fourth transistor is turned on.
A driving method of an organic light emitting diode display device comprising first to fifth transistors, first and second capacitors, a driving transistor, and a light emitting diode,
A first step of initializing a first node to a first reference voltage while the third transistor and the fourth transistor are turned on by an initialization signal and the fifth transistor is turned on by an emission control signal;
A second step of sensing a threshold voltage of the driving transistor while the third transistor and the fourth transistor are turned off and the fifth transistor is turned on;
While the first transistor is turned on by a control signal, supplying a high potential voltage to a second node to boost a voltage across the first node above a threshold voltage of the driving transistor;
A fifth step of causing the light emitting diode to emit light while the first transistor and the driving transistor are turned on and the fifth transistor is turned on by the light emission control signal;
A sixth step of sensing mobility of the driving transistor between the second step and the fourth step
Method of driving an organic light emitting diode display device comprising a.

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