KR102414444B1 - Organic light emitting display device and driving method of the same - Google Patents

Abstract

A method of driving an organic light emitting display device according to an embodiment of the present invention is provided. The organic light emitting diode display includes a pixel driving circuit, an anode, an organic light emitting device, and a cathode. The driving method includes applying a first scan signal to the pixel driving circuit at a first cycle, applying a second scan signal to the pixel driving circuit at a different cycle from the first cycle, and applying at least one control signal to the pixel driving circuit Including the step of authorizing. The first scan signal, the second scan signal, and the at least one control signal are applied so that the potential of the anode after the refresh operation of the pixel driving circuit and after the anode reset operation is the same.

Description

Organic light emitting display device and driving method thereof

The present invention relates to an organic light emitting display device and a driving method thereof, and more particularly, to an organic light emitting display device capable of reducing flicker and a driving method thereof.

Recently, as we enter the information age, the field of display that visually expresses electrical information signals has developed rapidly, and in response to this, various display devices with excellent performance of thinness, light weight, and low power consumption have been developed. is being developed

Specific examples of such a display device include a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), an organic light emitting display device ( Organic Light Emitting Display Device (OLED), etc. are mentioned.

Each of the plurality of pixels constituting the organic light emitting display device includes an organic light emitting device including an organic light emitting layer between an anode and a cathode, and a pixel driving circuit independently driving the organic light emitting device. The pixel driving circuit includes a switching thin film transistor (hereinafter referred to as a TFT), a driving TFT, and a capacitor. Here, the switching TFT charges the capacitor with a data voltage in response to the scan pulse, and the driving TFT controls the amount of current supplied to the organic light emitting device according to the data voltage charged in the capacitor to control the amount of light emitted from the organic light emitting device.

The organic light emitting display device is a self-emission type display device, and unlike a liquid crystal display device, it does not require a separate light source, so it can be manufactured in a lightweight and thin form. In addition, the organic light emitting display device is being studied as a next-generation display device in various fields because it is advantageous in terms of power consumption due to low voltage driving and excellent in color realization, response speed, viewing angle, and contrast ratio (CR). In addition, since the organic light emitting diode has a surface light emitting structure, it is easy to implement a flexible form.

In the organic light emitting diode display having the above advantages, differences in characteristics such as threshold voltage Vth and mobility of the driving TFT occur for each pixel due to process variation, etc., and a voltage drop of the high potential voltage VDD occurs. Accordingly, the amount of current for driving the organic light emitting diode varies, thereby causing a luminance deviation between pixels.

Alternatively, after the emission control signal is applied in the emission period in which the pixel emits light, an increase in the amount of current for driving the organic light emitting diode may be slowed due to a parasitic capacitance or a voltage fluctuation in the pixel. For this reason, a delay may occur in the organic light emitting device to emit light with sufficient luminance, and a low luminance may be recognized, which may cause a flicker phenomenon.

Accordingly, there is a demand for an organic light emitting diode display having a new structure capable of eliminating the flicker phenomenon.

The inventors of the present invention have recognized that an organic light emitting diode display may be implemented to perform anode reset or PWM (Pulse Width Modulation) driving in order to suppress a flicker phenomenon. Furthermore, in order to perform anode reset or PWM driving, an anode reset section is required in a section other than the refresh section, and it was recognized that the anode potential immediately after the anode reset section and the anode potential immediately after the refresh section were different.

Meanwhile, as is known, in charging the anode, the charge may be delayed by a storage capacitance in a pixel, an organic light emitting device capacitance, a parasitic capacitance, or the like. Accordingly, when the anode potential immediately after the anode reset driving and the anode potential immediately after the refresh are different, the anode charging time or the anode charging operation after the refresh period and after the anode reset period is different, so that a difference in luminance perceived by the eye may occur. The inventors of the present invention have recognized that such a luminance difference may be recognized as flicker, and may be a luminance difference that may occur during anode reset or PWM driving.

Accordingly, the inventors of the present invention set the potential of the anode at the time of anode reset or PWM driving in the pixel driving circuit of the organic light emitting display device to be the same as the potential of the anode immediately after the refresh period, so that the anode charging time becomes the same and the luminance perceived by the eye It was recognized that the difference could be minimized and thus flicker could be improved.

Accordingly, an object of the present invention is to provide an organic light emitting diode display capable of suppressing flicker and a driving method thereof by setting the anode potential immediately after a refresh operation and immediately after an anode reset or PWM driving to a specific voltage.

The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to solve the above problems, a method of driving an organic light emitting display device according to an embodiment of the present invention is provided. The organic light emitting diode display includes a pixel driving circuit, an anode, an organic light emitting device, and a cathode. The driving method includes applying a first scan signal to the pixel driving circuit at a first cycle, applying a second scan signal to the pixel driving circuit at a different cycle from the first cycle, and applying at least one control signal to the pixel driving circuit Including the step of authorizing. The first scan signal, the second scan signal, and the at least one control signal are applied so that the potential of the anode after the refresh operation of the pixel driving circuit and after the anode reset operation is the same.

According to another feature of the present invention, the refresh operation includes a section to which the first scan signal and the second scan signal are applied together, and the anode reset operation includes a section to which only the second scan signal is applied and the first scan signal is not applied. may include

According to another aspect of the present invention, the pixel driving circuit may include a first pixel driving switching device that outputs a data signal to a first node according to a second scan signal, and a second pixel control signal that is one of at least one control signal. A third pixel driving switching device including a second pixel driving switching device outputting a driving voltage to a second node according to the response, a gate to which a first scan signal is applied, and disposed between the second node and the third node, a third node a pixel driving device disposed between a first node and a second node, and a gate to which a first pixel control signal that is one of at least one control signal is applied, the first node and the fourth node including a gate connected to applying at least one control signal to the pixel driving circuit, including a fourth pixel driving switch element disposed therebetween, and a fifth pixel driving switching element outputting an initialization signal to a fourth node according to the first scan signal may include applying the first scan signal, the second scan signal, the first pixel control signal, and the second pixel control signal in the same state in the refresh operation and the anode reset operation.

According to another feature of the present invention, the potential of the fourth node in the refresh operation or immediately after the refresh operation may be the same as the potential of the fourth node after the anode reset operation.

According to another feature of the present invention, there may be a period in which the turn-on voltage is simultaneously applied to the first pixel control signal and the second scan signal in the refresh operation or immediately after the refresh operation.

According to another feature of the present invention, the first cycle may be faster than the second cycle by at least two times.

According to another feature of the present invention, the first scan signal, the second scan signal, and the at least one control signal are configured so that the potential of the anode before the organic light emitting device emits light is the same even during the duty change in PWM or the change in the refresh rate. , may be authorized.

In order to solve the above problems, an organic light emitting display device according to an exemplary embodiment is provided. An organic light emitting diode display includes a pixel driving circuit, an anode, an organic light emitting device, and a cathode. The pixel driving circuit includes: a first pixel driving switching element outputting a data signal to a first node according to a second scan signal, a second pixel driving switching element outputting a driving voltage to a second node according to the first pixel control signal; A third pixel driving switching device including a gate to which the first scan signal is applied, a third pixel driving switching device disposed between a second node and a third node, and a gate connected to the third node, disposed between the first node and the second node A fourth pixel driving switching device including a pixel driving device used as a pixel driving device, a gate to which a second pixel control signal is applied, a fourth pixel driving switching device disposed between the first node and the fourth node, and an initialization signal to the fourth node according to the first scan signal and a fifth pixel driving switching element outputting the pixel. A section to which the first scan signal and the second scan signal are applied together is a first section, a section to which only the first scan signal is applied and no second scan signal is applied is a second section, and the pixel driving circuit controls the first pixel It is configured to apply the signal and the second pixel control signal with a voltage having the same waveform to make the potential of the anode the same after the first period and the second period.

According to another feature of the present invention, the first period may include a period in which the first pixel control signal has a turn-on voltage and the first scan signal also has a turn-on voltage.

According to another feature of the present invention, the first cycle may be faster than the second cycle by at least two times.

Details of other embodiments are included in the detailed description and drawings.

According to the present invention, the flicker phenomenon can be suppressed by setting the anode potential immediately after the refresh operation and immediately after the anode reset or PWM driving to a specific voltage in the pixel driving circuit of the organic light emitting diode display.

1 is a schematic block diagram illustrating an organic light emitting diode display according to an exemplary embodiment.
2 is a schematic diagram illustrating a method of driving an organic light emitting diode display according to an exemplary embodiment.
3 is a circuit diagram illustrating one pixel driving circuit in an organic light emitting diode display according to an exemplary embodiment.
4A and 4B are waveform diagrams illustrating a signal input to the pixel driving circuit shown in FIG. 3 and a schematic output signal corresponding thereto.
5A and 5B are waveform diagrams illustrating a signal input to a conventional pixel driving circuit and a schematic output signal corresponding thereto.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings.

However, the present invention is not limited to the embodiments disclosed below, but will be embodied in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims.

Reference to a device or layer “on” another device or layer includes any intervening layer or other device directly on or in the middle of the other device or layer.

Although first, second, etc. are used to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the spirit of the present invention.

When a component is expressed in the singular, cases including the plural are included unless explicitly stated otherwise.

When a specific value according to an embodiment of the present invention is described, the specific value is interpreted as including a range of typical errors.

Like reference numerals refer to like elements throughout.

The size and thickness of each component shown in the drawings are illustrated for convenience of description, and the present invention is not necessarily limited to the size and thickness of the illustrated component.

Each feature of the various embodiments of the present invention can be partially or wholly combined or combined with each other, technically various interlocking and driving are possible, and each of the embodiments may be independently implemented with respect to each other or implemented together in a related relationship. may be

Hereinafter, an organic light emitting diode display and a driving method thereof according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic block diagram illustrating an organic light emitting diode display according to an exemplary embodiment.

Referring to FIG. 1 , the organic light emitting diode display 100 includes a display panel 110 including a plurality of pixels P, a gate driver 130 supplying gate signals to each of the plurality of pixels P, and a plurality of pixels. It includes a data driver 140 and a gate driver 130 that supply a data signal to each of the pixels P, and a timing controller 120 that controls the data driver 140 .

The timing controller 120 processes image data RGB input from the outside to be suitable for the size and resolution of the display panel 110 , and supplies it to the data driver 140 . The timing controller 120 receives the synchronization signals SYNC input from the outside, for example, the dot clock signal DCLK, the data enable signal DE, the horizontal synchronization signal Hsync, and the vertical synchronization signal Vsync. A plurality of gate and data control signals (GCS, DCS) are generated using By supplying the generated plurality of gate and data control signals GCS and DCS to the gate driver 130 and the data driver 140 , respectively, the gate driver 130 and the data driver 140 are controlled.

The gate driver 130 supplies a gate signal to the gate line GL according to the gate control signal GCS supplied from the timing controller 120 . Here, the gate signal includes at least one scan signal and a light emission control signal. Although it is illustrated in FIG. 1 that the gate drivers 130 are spaced apart from one side of the display panel 110 , the number and arrangement positions of the gate drivers 130 are not limited thereto. That is, the gate driver 130 may be disposed on one side or both sides of the display panel 110 in a GIP (Gate In Panel) method.

The data driver 140 converts the image data RGB into a data voltage according to the data control signal DCS supplied from the timing controller 120 , and converts the converted data voltage to the pixel P through the data line DL. supply to

In the display panel 110 , the plurality of gate lines GL and the plurality of data lines DL cross each other, and each of the plurality of pixels P is connected to the gate line GL and the data line DL. Specifically, one pixel P receives the gate signal from the gate driver 130 through the gate line GL, receives the data signal from the data driver 140 through the data line DL, and supplies power. Various power sources are supplied through the line. Specifically, one pixel P receives at least one scan signal and a light emission control signal through the gate line GL, receives a data voltage or a reference voltage through the data line DL, and receives a power supply line. The high potential voltage VDD, the low potential voltage VSS, and the initialization voltage Vinit are received through the.

In addition, each of the pixels P includes an organic light emitting device and a pixel driving circuit for controlling driving of the organic light emitting device. Here, the organic light emitting device includes an anode, a cathode, and an organic light emitting layer between the anode and the cathode. The pixel driving circuit includes a switching TFT, a driving TFT, and a capacitor. Specifically, in the pixel driving circuit, the driving TFT controls the amount of light emitted by the organic light emitting device by controlling the amount of current supplied to the organic light emitting device according to the data voltage charged in the capacitor, and the switching TFT controls the amount of light emitted through the gate line GL. It receives the signal and charges the data voltage into the capacitor.

As such, the organic light emitting diode display 100 includes a driving TFT and a switching TFT in a pixel driving circuit, and an active layer constituting each of the driving TFT and the switching TFT may be made of the same material or different materials. . When each of the driving TFT and the switching TFT is formed of a TFT having different characteristics in one pixel driving circuit, the organic light emitting diode display 100 may include multiple types of TFTs.

Specifically, in the organic light emitting display device 100 including a multi-type TFT, a LTPS TFT using a low temperature poly-silicon (hereinafter referred to as LTPS) is used as a TFT using a polycrystalline semiconductor material as an active layer. do. Polysilicon material has high mobility (100 cm 2 /Vs or more), low energy consumption, and excellent reliability. can do. Alternatively, in the organic light emitting diode display 100 , it may be preferably applied as a driving TFT in the pixel P.

Also, in the organic light emitting diode display 100 including multi-type TFTs, an oxide semiconductor TFT using an oxide semiconductor material as an active layer is used. Since the oxide semiconductor material has a low off-current, it may be suitable for a switching TFT that has a short turn-on time and a long turn-off time. Oxide semiconductor TFTs have better voltage holding characteristics than LTPS TFTs.

For example, the organic light emitting diode display 100 including multi-type TFTs according to an embodiment of the present invention includes a pixel driving circuit in which the switching TFT is made of an oxide semiconductor TFT and the driving TFT is made of a LTPS TFT. However, in the organic light emitting diode display 100 of the present invention, the switching TFT is not limited to an oxide semiconductor TFT and the driving TFT is not limited to an LTPS TFT, and a multi-type TFT may be variously configured. Also, in the organic light emitting diode display 100 of the present invention, the pixel driving circuit may include one type of TFT instead of multiple types of TFTs.

In addition, the organic light emitting diode display 100 according to the embodiment of the present invention performs an anode reset driving or PWM driving to reset the potential of the anode using a scan signal in an extra frame other than the refresh frame in order to suppress the flicker phenomenon. can be done

Furthermore, the organic light emitting diode display 100 according to an embodiment of the present invention drives the anode potential immediately after the refresh operation to be the same as the potential immediately after the anode reset operation or the PWM operation, so that the anode charging time after the refresh operation or the anode reset operation Since these values are substantially the same, it is possible to minimize the occurrence of flicker due to a decrease in luminance of the organic light emitting diode. Hereinafter, it will be exemplarily described that the organic light emitting diode display 100 performs the anode reset operation, but the present invention is not limited thereto, and the organic light emitting display may operate in the same manner as the operations described below while performing the PWM operation. have.

2 is a schematic diagram illustrating a method of driving an organic light emitting diode display according to an exemplary embodiment. 2 schematically shows a refresh section S1, a first light emission section E1, an anode reset section S2, and a second light emission section E2. The refresh section S1 includes an initialization section, a sampling section, and a programming section. Also, the refresh section S1 includes the anode voltage preset section X1 after the programming section. The anode reset section S2 also includes the anode voltage preset section X2.

In the anode voltage preset period (X1, X2), according to the application of scan signals and at least one control signal, the potential of the anode after the refresh period (S1) and after the anode reset period (S2) of the pixel driving circuit may be set to be the same. have. The method of applying the scan signals and the control signal may be different depending on the type of the pixel driving circuit, for example, whether the pixel driving circuit is 6T1C, 6T2C, or 4T2C, and may be different according to a specific circuit structure. Since the potential of the anode becomes the same after the refresh period S1 and after the anode reset period S2, the anode charging time in the first light emission period E1 and the second light emission period E2 becomes the same and is recognized by the eye A difference in luminance that is generated is minimized, and thus flicker may be improved.

Hereinafter, an exemplary circuit for setting the potential of the anode to be the same after the refresh period S1 and after the anode reset period S2 in the organic light emitting diode display 100 according to an embodiment of the present invention will be described. Hereinafter, an exemplary circuit is described as having a 6T1C structure, but is not limited thereto, and the present invention is not limited thereto. It is intended to include all operations that make them the same in .

FIG. 3 is an exemplary driving circuit diagram of the pixel illustrated in FIG. 1 . Referring to FIG. 3 , a pixel includes an organic light emitting diode (OLED), six transistors, and a pixel driving circuit 200 including one capacitor to drive the organic light emitting diode (OLED).

Specifically, the pixel driving circuit 200 includes a driving transistor DT, first to fifth switching transistors T1-T5, and a storage capacitor Cst. The driving TFT DT includes a gate node that is a third node N3 connected to one node of the storage capacitor Cst, a third switching TFT T3 and a second node N2 electrically connected to the second switching TFT T2. ) including a drain node and a source node as a first node N1 electrically connected to the first switching TFT T1 and the fourth switching TFT T4.

Specifically, the drain node of the driving TFT DT is electrically connected to the high potential voltage VDD line. Accordingly, the gate node of the driving TFT DT stores the high potential voltage VDD when the third switching TFT T3 and the second switching TFT T2 are turned on.

In addition, when the first switching TFT T1 is turned on, the data voltage Vdata is supplied to the source node of the driving TFT DT, and as the third switching TFT T3 is turned on, the driving TFT DT ), the data voltage Vdata of the source node is supplied to the third node N3 which is the gate node of the driving TFT DT.

To explain this, when the third switching TFT T3 is turned on, the second node N2 that is the drain node of the driving TFT DT and the third node N3 that is the gate node of the driving TFT DT are connected. , Vgs of the driving TFT (DT) becomes Vth of the driving TFT (DT) by the diode connection method. Accordingly, when the first switching TFT T1 is turned on and the data voltage Vdata is supplied to the source node of the driving TFT DT, the voltage Vdata+Vth is supplied to the gate node of the driving TFT DT.

A source node of the driving TFT DT is electrically connected to the organic light emitting diode. Specifically, the source node of the driving TFT (DT) is connected to the drain node of the fourth switching TFT (T4) and the fourth node (N4). Also, it is electrically connected to the anode of the organic light emitting diode and is connected to the source node of the first switching TFT T1 .

When the fourth switching TFT T4, the driving TFT DT, and the second switching TFT T2 are turned on, the driving TFT DT supplies the high potential voltage VDD and the driving current to the organic light emitting device to The organic light emitting device emits light.

Hereinafter, it will be described that the switching TFT and the driving TFT are n-type devices, but in various embodiments, the switching TFT and the driving TFT may be p-type devices. In these embodiments, the voltage for turning on the TFT may be a voltage supplied in a low state.

The first switching TFT T1 includes a gate node connected to the second scan signal line SCAN2, a drain node connected to the data line, and a source node connected to a first node N1 that is a source node of the driving TFT DT. . Accordingly, the first switching TFT T1 is turned on or turned off by the second scan signal SCAN2 . That is, when the second scan signal SCAN2 is supplied to the gate node of the first switching TFT T1 in a high state, the data voltage Vdata from the drain node of the first switching TFT T1 is applied to the driving TFT DT. It is supplied to the first node N1 which is the source node.

The third switching TFT T3 has a gate node connected to the first scan signal line SCAN1, a drain node of the driving TFT DT, and a drain node connected to a source node of the second switching TFT T2 and the driving TFT DT. contains a source node connected to the gate node of Also, a source node of the third switching TFT T3 is connected to a node of the storage capacitor Cst.

Accordingly, the third switching TFT T3 may be turned on or turned off by the first scan signal SCAN1 . That is, when the first scan signal SCAN1 is in a high state, the third switching TFT T3 is turned on. Accordingly, the third switching TFT T3 transfers the voltage at the second node N2 that is the drain node of the driving TFT DT to the voltage of the third node N3 that is the gate node of the driving TFT DT.

In addition, the n-th emission control signal EM[n] is supplied to the gate node of the second switching TFT T2 as a DC voltage until it changes from the high state to the low state. Accordingly, when the third switching TFT T3 is turned on, only the high potential voltage VDD is supplied to the third node N3 that is the gate node of the driving TFT DT.

The second switching TFT T2 includes a gate node connected to the nth light emission control signal EM[n] line, a drain node connected to a high potential voltage (VDD) line, and a source node connected to the drain node of the driving TFT DT. include

The second switching TFT T2 may be turned on or turned off by the n-th emission control signal EM[n]. That is, when the n-th emission control signal EM[n] is in a high state, the second switching TFT T2 is turned on, and the high potential voltage VDD is applied from the source node to the drain node of the driving TFT DT. It is supplied to the second node N2.

Subsequently, when the n-th emission control signal EM[n] is in a high state, the third switching TFT T2 supplies the high potential voltage VDD to the drain node of the driving TFT DT, and the driving TFT DT ) of the drain-source current (hereinafter referred to as Ids) flows through the organic pore-forming element. Accordingly, the driving TFT DT controls the amount of current of the organic light emitting diode by the data voltage Vdata.

The fourth switching TFT T4 has a gate node connected to the n-1 th light emission control signal EM[n-1] line, a drain node connected to a source node of the driving TFT DT, and a source electrically connected to the organic light emitting diode. contains nodes. Accordingly, the fourth switching TFT T4 may be turned on by the n-1 th emission control signal EM[n-1].

That is, when the n-1 th light emission control signal EM[n-1] is in a high state during the connection period, the fourth switching TFT T4 is turned on and the first node that is the source node of the driving TFT DT (N1) and a fourth node N4, which is a source node of the fourth switching TFT T4, are connected.

Accordingly, when the fourth switching TFT T4 is turned on by the n-1 th emission control signal EM[n-1], the voltage Vdata of the first node N1 is changed to the fourth node N4. is supplied with

During the light emitting period, when the fourth switching TFT T4 , the driving TFT DT and the second switching TFT T2 are turned on, the high potential voltage VDD is supplied to the driving TFT DT and applied to the organic light emitting device. The driving current Ids is supplied so that the organic light emitting diode emits light.

The fifth switching TFT T5 has a gate node connected to the first scan signal line SCAN1, a source node connected to the initialization voltage Vinit line, one node of the storage capacitor Cst, and a fourth node that is an anode of the organic light emitting diode. It includes a drain node connected to (N4).

Accordingly, the fifth switching TFT T5 may be turned on by the first scan signal SCAN1 . That is, when the first scan signal SCAN1 is in a high state, the fifth switching TFT T5 is turned on to supply the initialization voltage Vinit to the fourth node N4 . Accordingly, when the fifth switching TFT T5 is turned on by the first scan signal SCAN1 , the initialization voltage Vinit is supplied to the fourth node N4 , and the data voltage Vdata written in the organic light emitting diode is applied. ) is initialized.

Also, the initialization voltage Vinit may be related to a voltage stored in the storage capacitor Cst together with the voltage supplied to the third node N3 .

Specifically, the storage capacitor Cst stores a voltage applied to the gate node of the driving TFT DT. Here, one node of the storage capacitor Cst is connected to the third node N3 which is the gate node of the driving TFT DT, and the other node is connected to the fourth node N4 electrically connected to the anode of the organic light emitting diode. do.

That is, the storage capacitor Cst is electrically connected to the third node N3 and the fourth node N4 and is the difference between the voltage supplied to the gate node of the driving TFT DT and the voltage supplied to the anode of the organic light emitting diode. save the

Specifically, as the first switching TFT T1 and the third switching TFT T3 are turned on to one node of the storage capacitor Cst, Vdata+Vth is applied to the other node, and the fifth switching TFT T3 is turned on. As T5 is turned on, the initialization voltage Vinit is applied. Accordingly, the voltage charged in the storage capacitor Cst becomes Vdata+Vth-Vinit.

In the anode voltage preset period, the n-1 th emission control signal EM[n-1] may be in a high state, and the second scan signal SCAN2 may be in a high state. Accordingly, as the first switching TFT T1 and the fourth switching TFT T1 are turned on, the first node N1 and the fourth node N4 apply a specific voltage through the data line Vdata line. is supplied, and the anode potential is preset to a specific voltage.

4A and 4B are waveform diagrams illustrating a signal input to the pixel driving circuit shown in FIG. 3 and a schematic output signal corresponding thereto. For convenience of description, it will be described later with reference to FIGS. 2 and 3 .

4A is a waveform diagram illustrating schematic input/output signals of a pixel driving circuit driven according to a driving method of an organic light emitting diode display according to an exemplary embodiment. Referring to FIG. 4A , schematically illustrating input/output signals of a pixel driving circuit operating at a refresh rate of 60 Hz and an anode reset rate of 120 Hz is illustrated. The scan signals SCAN1 and SCAN2 are applied in a high state in the refresh period S1 , and the emission control signals EM1 and EM2 are applied in a low state in a part of the refresh period S1 . A third node N3 that is a gate node of the driving TFT, a first node N1 that is a source node of the driving TFT, a second node N2 that is a drain node of the driving TFT, and Vgs are shown. According to an embodiment of the present invention, a specific voltage V1 is supplied to the first node N1 in the anode preset period X1 at the end of the refresh period S1, and the anode reset period S2 or the anode voltage preset The same specific voltage V1 is also supplied to the first node N1 in the section X2. Accordingly, the first node N1 has the same voltage V1 immediately before the light emission periods E1 and E2, and Vgs(Vgs) becomes the same, so that the anode charging time and the amount of current of the organic light emitting device are equal to the light emission period E1 , E2), so that the occurrence of flicker can be suppressed. Furthermore, in various embodiments, specific voltages V2 and V3 are supplied to the second and third nodes N2 and N3 in the anode preset period X1, and the anode reset period S2 or the anode voltage preset period X2 ), the specific voltages V2 and V3 may be supplied to the second and third nodes N2 and N3.

FIG. 4B is an enlarged view of the refresh period S1 and the anode reset period S2 of FIG. 4A . The refresh section includes an initialization section, a sampling section, a programming section, and an anode voltage preset section X1. In addition, a connection section and a light emitting section are also shown.

The refresh period may be set to approximately one horizontal period (1H), and data is written to pixels arranged in one horizontal line of the pixel array during the refresh period. Specifically, during the refresh period, the threshold voltage Vth of the driving TFT DT of the pixel driving circuit 200 is sampled, and the data voltage Vdata is compensated for by the threshold voltage Vth. Accordingly, the data voltage Vdata is compensated and written in the pixel so that the amount of current of the organic light emitting diode can be determined regardless of the threshold voltage Vth.

Referring to FIG. 4B , the data voltage Vdata is written to each pixel arranged in one horizontal line through an initialization period, a sampling period, a programming period, an anode voltage preset period, a connection period, and a light emission period, and each pixel emits light. . Each of the initialization period, sampling period, programming period, anode voltage preset period, connection period, and light emission period described below may be variously changed according to embodiments. Hereinafter, it is described that each of the input signals is input at a specific timing, but the present invention is not limited thereto. are intended to be included in the scope.

First, the first scan signal SCAN1 rises to a high state at the moment the initialization period starts, and the second scan signal SCAN2 maintains a low state. At the same time, the n-1 th emission control signal EM[n-1] also maintains a low state, and the n-th emission control signal EM[n] is polled from a high state during the initialization period to become a low state.

Accordingly, during the initialization period, the third switching TFT T3 and the fifth switching TFT T5 are turned on, and the first switching TFT T1 and the fourth switching TFT T4 are turned off. Also, the second switching TFT T2 is turned on only during a period in which the n-th emission control signal EM[n] is in a high state, and is turned on while the n-th emission control signal EM[n] is converted to a low state. turns off

Accordingly, the initialization voltage Vinit is supplied to the fourth node N4 through the fifth switching TFT T5 , and the high potential voltage VDD is switched to the third switching while the second switching TFT T2 is turned on. It is supplied to the third node N3 through the TFT T3. That is, as the initialization voltage Vinit is supplied to the fourth node N4 that is the source node of the driving TFT DT, the data voltage Vdata written in the organic light emitting diode is initialized, and the gate of the driving TFT DT is initialized. A high potential voltage VDD is supplied to the node.

During the sampling period, the first scan signal SCAN1 is maintained in a low state and the second scan signal SCAN2 rises to a high state. During the sampling period, both the n-th emission control signal EM[n] and the n-1 th emission control signal EM[n-1] are maintained in a low state.

Subsequently, in the programming period, the first scan signal SCAN1 rises to a high state, and the second scan signal SCAN2 maintains a high state. During the programming period, both the n-th emission control signal EM[n] and the n-1th emission control signal EM[n-1] are maintained in a low state. The programming period of the refresh operation includes a period in which the first scan signal SCAN1 and the second scan signal SCAN2 are applied together.

Subsequently, before the anode voltage preset period X1, the first scan signal SCAN1 is pulled to a low state, the second scan signal SCAN2 is maintained in a high state, and the nth light emission control signal EM[n] is It rises to a high state, and the n-1 th emission control signal EM[n-1] is maintained in a low state.

Accordingly, the first switching TFT T1 and the fourth switching TFT T4 are turned on, and a specific voltage is applied to the first node N1 and the fourth node N4 in the anode voltage preset period X1. It may be supplied through the line Vdata.

During the connection period, the first scan signal SCAN1 and the second scan signal SCAN2 are maintained in a low state. The n-1 th emission control signal EM[n-1] is maintained in a high state, and the n-th emission control signal EM[n] is maintained in a low state. Accordingly, only the fourth switching TFT T4 is turned on during the connection period, and the first switching TFT T1 , the second switching TFT T2 , the third switching TFT T3 and the fifth switching TFT T5 are all turned on. is turned off Accordingly, the fourth switching TFT T4 is turned on so that the first node N1 and the first node N4 are electrically connected, and the first node N1 and the fourth node N4 have the same voltage. maintain.

During the emission period, the first scan signal SCAN1 and the second scan signal SCAN2 are maintained in a low state. At the moment the emission period starts, the n-th emission control signal EM[n] rises and maintains a high state during the emission period. In addition, the n-1 th emission control signal EM[n-1] also maintains a high state. Accordingly, during the light emission period, the first switching TFT ( T1 ), the third switching TFT ( T3 ), and the fifth switching TFT ( T5 ) are turned off, and the second switching TFT ( T2 ) and the fourth switching TFT ( T4 ) are turned on comes on In addition, the driving TFT DT is also turned on to form a path through which a driving current can flow from the high potential voltage VDD line to the organic light emitting diode. That is, Ioled flows to the organic light emitting diode through the driving TFT (DT), the second switching TFT ( T2 ), and the fourth switching TFT ( T4 ) turned on during the light emitting period.

Next, the anode voltage preset section X2 of the anode reset section will be described. In the anode voltage preset period X2, as in the anode voltage preset period X1, the first scan signal SCAN1 is in a low state, and the second scan signal SCAN2 rises and maintains a high state, and the nth light emission The control signal EM[n] is maintained in a high state, and the n-1th emission control signal EM[n-1] is maintained in a low state.

The first switching TFT ( T1 ) and the fourth switching TFT ( T4 ) are turned on, and the anode voltage preset period ( X1 ) at the first node ( N1 ) and the fourth node ( N4 ) in the anode voltage preset period ( X2 ) A voltage equal to the voltage at may be supplied through the data line Vdata. Accordingly, there is an effect that the flicker phenomenon can be suppressed by setting the anode potential immediately after the refresh operation and immediately after the anode reset to a specific voltage.

In various embodiments, the first scan signal, the second scan signal, and the at least one light emission control signal are equally applied even when the potential of the anode before the organic light emitting device emits light during duty change in PWM or change in refresh rate It may be implemented as much as possible. In this case, even if the refresh rate and the anode reset rate fluctuate at the same time, the flicker phenomenon can be suppressed.

5A and 5B are waveform diagrams illustrating a signal input to a conventional pixel driving circuit and a schematic output signal corresponding thereto. 5A and 5B are the same as FIGS. 4A and 4B except that the anode voltage preset period X1 does not exist in the refresh period. However, since the anode voltage preset period X1 does not exist in the refresh period, referring to FIG. 5A , the anode potential at the end of the refresh period or the start of the first light emission period at the first node N1 is the anode The anode potential at the end of the reset section (X) or the second light emitting section differs by D1, so that there is a difference in the anode charging times in the first and second light emitting sections, and there is a difference in Vgs by D4, so that flicker is recognized. can Furthermore, a difference by D2 and D3 may occur in the second and third nodes N2 and N3 as well.

Although the embodiments of the present invention have been described in more detail with reference to the accompanying drawings, the present invention is not necessarily limited to these embodiments, and various modifications may be made within the scope without departing from the technical spirit of the present invention. . Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

100: organic light emitting display device
110: display panel
120: timing controller
130: gate driver
140: data driver
200: pixel driving circuit

Claims (10)

A method of driving an organic light emitting display device including a pixel driving circuit and an anode, an organic light emitting device, and a cathode, the method comprising:
applying a first scan signal to the pixel driving circuit in a first cycle;
applying a second scan signal to the pixel driving circuit in a second period different from the first period; and
applying at least one control signal to the pixel driving circuit;
The first scan signal, the second scan signal, and the at least one control signal are applied such that the potential of the anode after the refresh operation of the pixel driving circuit and after the anode reset operation is the same. Way. According to claim 1,
The refresh operation includes a section in which the first scan signal and the second scan signal are applied together,
and the anode reset operation includes a section to which only the second scan signal is applied and the first scan signal is not applied. 3. The method of claim 2,
The pixel driving circuit comprises:
a first pixel driving switching device for outputting a data signal to a first node according to the second scan signal;
a second pixel driving switching device for outputting a driving voltage to a second node according to a second pixel control signal that is one of the at least one control signal;
a third pixel driving switching device including a gate to which the first scan signal is applied and disposed between the second node and a third node;
a pixel driving device including a gate connected to the third node and disposed between the first node and the second node;
a fourth pixel driving switch element including a gate to which a first pixel control signal, which is one of the at least one control signal, is applied, and disposed between the first node and the fourth node; and
a fifth pixel driving switching device outputting an initialization signal to the fourth node according to the first scan signal;
The applying of at least one control signal to the pixel driving circuit may include the first scan signal, the second scan signal, the first pixel control signal, and the second pixel control signal in the refresh operation and the anode reset operation. A driving method of an organic light emitting display device comprising the step of applying in the same state. 4. The method of claim 3,
and a potential of the fourth node in the refresh operation or immediately after the refresh operation is the same as a potential of the fourth node after the anode reset operation. 4. The method of claim 3,
A period in which a turn-on voltage is simultaneously applied to the first pixel control signal and the second scan signal in the refresh operation or immediately after the refresh operation exists. According to claim 1,
and the first cycle is at least twice faster than the second cycle. According to claim 1,
The first scan signal, the second scan signal, and the at least one control signal are applied so that the potential of the anode before the organic light emitting device emits light is the same even during a duty change in PWM or a change in a refresh rate, A method of driving an organic light emitting diode display. It includes a pixel driving circuit, an anode, an organic light emitting device, and a cathode,
The pixel driving circuit comprises:
a first pixel driving switching device for outputting a data signal to a first node according to a second scan signal;
a second pixel driving switching device for outputting a driving voltage to a second node according to a second pixel control signal;
a third pixel driving switching device including a gate to which a first scan signal is applied and disposed between the second node and a third node;
a pixel driving device including a gate connected to the third node and disposed between the first node and the second node;
a fourth pixel driving switching device including a gate to which a first pixel control signal is applied and disposed between the first node and a fourth node; and
a fifth pixel driving switching element outputting an initialization signal to the fourth node according to the first scan signal;
A section to which the first scan signal and the second scan signal are applied together is a first section,
A section in which only the second scan signal is applied and the first scan signal is not applied is a second section,
and the pixel driving circuit is configured to equalize the potential of the anode after the first period and the second period. 9. The method of claim 8,
The first period includes a period in which the first pixel control signal has a turn-on voltage and the second scan signal also has a turn-on voltage. 9. The method of claim 8,
applying the first scan signal to the pixel driving circuit in a first period in the first period;
applying the second scan signal to the pixel driving circuit in a second period in the second section;
and the first cycle is at least two times faster than the second cycle.

Images