KR20190040849A - Organic light emitting display device and driving method of the same - Google Patents

Abstract

According to one embodiment of the present invention, provided is a driving method of an organic light emitting display device. The organic light emitting display device includes a pixel driving circuit, an anode, an organic light emitting device, and a cathode. The driving method comprises the following steps: applying a first scan signal to the pixel driving circuit in a first period; applying a second scan signal to the pixel driving circuit in a 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 so that the potential of the anode after a refresh operation of the pixel driving circuit and the potential of the anode after the anode reset operation are the same.

Description

Technical Field [0001] The present invention relates to an organic light emitting diode (OLED) display device,

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

Recently, as the information age has come to the age of information, a display field for visually expressing electrical information signals has been rapidly developed. In response to this, various display devices having excellent performance in thinning, light weighting, Is being developed.

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

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

The organic light emitting display device is a self-emission type display device, unlike a liquid crystal display device, a separate light source is not required, and thus it can be manufactured in a light and thin shape. In addition, the organic light emitting display device is not only advantageous in terms of power consumption by low voltage driving, but also has excellent hue, response speed, viewing angle, and contrast ratio (CR), and has been studied as a next generation display device in various fields. Further, since the organic light emitting element has a surface light emitting structure, it is easy to realize a flexible form.

In the OLED display device having the above advantages, a characteristic difference such as a threshold voltage (Vth) and a mobility of a driving TFT is generated for each pixel due to a process variation or the like, and a voltage drop of the high potential voltage (VDD) And the amount of current for driving the organic light emitting diode is changed, so that a luminance deviation occurs between the pixels.

Alternatively, after the light emission control signal is applied in the light emission period in which the pixels emit light, the rate at which the amount of current driving the organic light emitting element increases due to the parasitic capacitance in the pixel or the voltage fluctuation inside the pixel may be slowed down. As a result, a delay occurs in the organic light emitting element to emit light at a sufficient luminance, and a low luminance is recognized, resulting in a flicker phenomenon.

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

The inventors of the present invention have recognized that an organic light emitting display can be implemented to perform an anode reset or PWM (Pulse Width Modulation) driving to suppress the flicker phenomenon. Further, in order to perform the anode reset or the PWM driving, an anode reset period is required in a period outside the refresh period, and the anode potential immediately after the anode reset period and the anode potential immediately after the refresh period become different.

On the other hand, as is known, in charge of the anode, the charge can be delayed by the storage capacitance in the pixel, the organic light emitting element capacitance, parasitic capacitance, or the like. Thus, when the anode potential immediately after the anode reset driving and the anode potential immediately after the refresh are different from each other, the anode charging time or the anode charging operation after the refresh interval and the anode reset interval are changed, and a luminance difference perceived by the eye may occur. The inventors of the present invention have recognized that this luminance difference can be perceived as a flicker and is a luminance difference that can occur during an anode reset or PWM driving.

Thus, the inventors of the present invention have found that, by making the potential of the anode and the potential of the anode immediately after the refresh interval equal during the anode reset or PWM driving in the pixel driving circuit of the organic light emitting display, the anode charging time becomes the same, The difference is minimized and thus the flicker can be improved.

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

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

According to an aspect of the present invention, there is provided a method of driving an organic light emitting diode display. The organic light emitting display includes a pixel driving circuit and an anode, an organic light emitting element, and a cathode. The driving method includes the steps of applying a first scan signal to the pixel driving circuit at a first period, applying a second scanning signal to the pixel driving circuit at a 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 at least one control signal are applied so that the potential of the anode after the refresh operation of the pixel drive circuit and the anode after the anode reset operation are the same.

According to another aspect of the present invention, the refresh operation includes a period in which the first scan signal and the second scan signal are applied together, and the anode reset operation includes a period in which only the second scan signal is applied and the first scan signal is not applied .

According to another aspect of the present invention, a pixel driving circuit includes: a first pixel driving switching element for outputting a data signal to a first node in accordance with a second scanning signal; A second pixel driving switching element for outputting a driving voltage to a second node, a gate to which a first scan signal is applied, a third pixel driving switching element disposed between the second node and the third node, And a gate to which a first pixel control signal, which is one of the at least one control signal, is applied, and the gate of the first node and the fourth node And a fifth pixel drive switching element for outputting an initialization signal to a fourth node according to the first scan signal, The method comprising: applying a predetermined driving circuit, the first scan signal, the second scan signal, the first pixel control signal and the second pixel control signal from the refresh operation and the anode reset operation may include a step of applying the same.

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

According to still another aspect of the present invention, there may be a period during 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 aspect of the present invention, the first period may be at least two times faster than the second period.

According to another aspect of the present invention, the first scan signal, the second scan signal, and the at least one control signal are set so that the potential of the anode before the organic light emitting element emits light is the same even when the duty variation or the refresh rate fluctuation in the PWM .

According to an aspect of the present invention, there is provided an organic light emitting diode display. The organic light emitting display includes a pixel driving circuit, an anode, an organic light emitting element, and a cathode. The pixel driving circuit includes a first pixel driving switching element for outputting the data signal to the first node according to the second scan signal, a second pixel driving switching element for outputting the driving voltage to the second node according to the first pixel control signal, A third pixel drive switching element disposed between the second node and the third node, and a gate coupled to the third node, wherein the third pixel drive switching element is disposed between the first node and the second node, A fourth pixel drive switching element disposed between the first node and the fourth node and including a gate to which the second pixel control signal is applied, and a fourth pixel drive switching element arranged between the first node and the fourth node, And a fifth pixel drive switching element for outputting the fifth pixel drive switching element. The first period of the first scan signal and the second scan signal are the first period and the second period of the second period when the first scan signal is applied and the second scan signal is not applied, Signal and the second pixel control signal are applied with a voltage of the same waveform so that the potential of the anode after the first section is equal to that of the anode after the second section.

According to another aspect of the present invention, the first pixel control signal may have a turn-on voltage, and the first scan signal may have a turn-on voltage.

According to another aspect of the present invention, the first period may be at least two times faster than the second period.

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

The present invention has 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 or PWM drive to a specific voltage in the pixel drive circuit of the organic light emitting diode display.

FIG. 1 is a schematic block diagram for explaining an organic light emitting display according to an embodiment of the present invention. Referring to FIG.
2 is a schematic view illustrating a method of driving an organic light emitting display according to an embodiment of the present invention.
3 is a circuit diagram showing one pixel driving circuit in an OLED display according to an embodiment of the present invention.
4A and 4B are waveform diagrams illustrating signals input to the pixel driving circuit shown in FIG. 3 and schematic output signals thereof.
5A and 5B are waveform diagrams showing a signal input to a conventional pixel driving circuit and a schematic output signal according to the signal.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings.

It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

An element or layer is referred to as being another element or layer " on ", including both intervening layers or other elements directly on or in between.

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

Where an element is expressed in its singular form, it includes the case where plural elements are included unless explicitly stated.

When a specific numerical value according to an embodiment of the present invention is described, the specific numeric value is interpreted to include a range of usual error.

Like reference numerals refer to like elements throughout the specification.

The sizes and thicknesses of the individual components shown in the figures are shown for convenience of explanation and the present invention is not necessarily limited to the size and thickness of the components shown.

It is to be understood that each of the features of the various embodiments of the present invention may be combined or combined with each other, partially or wholly, technically various interlocking and driving, and that the embodiments may be practiced independently of each other, It is possible.

Hereinafter, an OLED display and a driving method thereof according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram for explaining an organic light emitting display according to an embodiment of the present invention. Referring to FIG.

1, an OLED display 100 includes a display panel 110 including a plurality of pixels P, a gate driver 130 for supplying a gate signal to each of the plurality of pixels P, A data driver 140 for supplying a data signal to each of the pixels P and a timing controller 120 for controlling the gate driver 130 and the data driver 140.

The timing controller 120 processes image data RGB inputted from outside according to the size and the resolution of the display panel 110 and supplies the data to the data driver 140. The timing controller 120 outputs the synchronizing signals SYNC input from the outside, for example, a dot clock signal DCLK, a data enable signal DE, a horizontal synchronizing signal Hsync, and a vertical synchronizing signal Vsync To generate a plurality of gate and data control signals (GCS, DCS). And controls the gate driver 130 and the data driver 140 by supplying the generated gate and data control signals GCS and DCS to the gate driver 130 and the data driver 140, respectively.

The gate driver 130 supplies a gate signal to the gate line GL in accordance with 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. In FIG. 1, the gate driver 130 is shown as being disposed on one side of the display panel 110, but the number and arrangement 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) manner.

The data driver 140 converts the image data RGB into data voltages according to the data control signal DCS supplied from the timing controller 120 and supplies the converted data voltages to the pixels P through the data lines DL. .

A plurality of gate lines GL and a plurality of data lines DL are intersected with each other in the display panel 110 and each of the plurality of pixels P is connected to a gate line GL and a data line DL. Specifically, one pixel P receives a gate signal from the gate driver 130 through the gate line GL, receives a data signal from the data driver 140 through the data line DL, 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 a gate line GL, receives a data voltage or a reference voltage via a data line DL, And receives the high potential voltage VDD, the low potential voltage VSS, and the initialization voltage Vinit.

Each of the pixels P includes an organic light emitting element and a pixel driving circuit for controlling driving of the organic light emitting element. Here, the organic light emitting element comprises 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 to be supplied to the organic light emitting element according to the data voltage charged in the capacitor, thereby adjusting the amount of light emitted from the organic light emitting element, and the switching TFT is connected to the scan Signal to charge the data voltage to the capacitor.

As described above, the organic light emitting diode display 100 includes the driving TFT and the switching TFT in the pixel driving circuit, and the active layer constituting each of the driving TFT and the switching TFT may be composed of the same material or may be composed of different materials . In the case where each of the driving TFT and the switching TFT is composed of TFTs having different characteristics in one pixel driving circuit, the organic light emitting display 100 may include a multi-type TFT.

Specifically, in the organic light emitting diode display 100 including a multi-type TFT, an LTPS TFT using low temperature poly-silicon (hereinafter referred to as LTPS) is used as a TFT having a polycrystalline semiconductor material as an active layer do. Since the polysilicon material has high mobility (100 cm 2 / Vs or more), low energy consumption power and excellent reliability, the polysilicon material is applied to the gate driver 130 and / or the multiplexer (MUX) for driving the display element TFTs can do. Or as a driving TFT in the pixel P in the organic light emitting diode display 100.

In the organic light emitting diode display 100 including a multi-type TFT, 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 which has a short turn-on time and a long turn-off time. The oxide semiconductor TFT has a better voltage hold characteristic than the LTPS TFT.

Illustratively, the organic light emitting diode display 100 including the multi-type TFT according to the embodiment of the present invention includes a pixel driving circuit in which the switching TFT is composed of an oxide semiconductor TFT and the driving TFT is composed of an LTPS TFT. However, in the organic light emitting diode display device 100 of the present invention, the switching TFT is not limited to the oxide semiconductor TFT and the driving TFT is not limited to the LTPS TFT, and the multi-type TFT may be variously configured. In the organic light emitting diode display 100 according to the present invention, the pixel drive circuit may include a TFT of one type without including a multi-type TFT.

In addition, the organic light emitting diode display 100 according to the embodiment of the present invention includes an anode reset driving or a PWM driving for resetting the potential of the anode using a scan signal in an extra frame in addition to the refresh frame in order to suppress the flicker phenomenon Can be performed.

Further, the organic light emitting diode display 100 according to the embodiment of the present invention drives the anode potential immediately after the refresh operation to be the same as the anode reset operation or the potential immediately after the PWM operation, so that the anode charging time after the refresh operation or after the anode reset operation The occurrence of flicker due to the lowering of the luminance of the organic light emitting element can be minimized. Hereinafter, the OLED display 100 will be described as performing the anode reset operation, but the present invention is not limited thereto. The OLED display may operate in the same manner as the operations described below while performing the PWM operation. have.

2 is a schematic view illustrating a method of driving an organic light emitting display according to an embodiment of the present invention. 2 schematically shows the refresh period S1, the first emission period E1, the anode reset period S2 and the second emission period E2. The refresh period S1 includes an initialization period, a sampling period, and a programming period. In addition, the refresh interval S1 includes the anode voltage preset interval X1 after the programming interval. The anode reset period S2 also includes an anode voltage preset period X2.

In the anode voltage preset periods X1 and X2, the potentials of the anode after the refresh period S1 and the anode reset period S2 after the refresh period of the pixel driving circuit are set to be equal to each other according to the application of the scan signals and at least one control signal have. The application methods of the scan signals and the control signals may differ depending on the type of the pixel driving circuit, for example, whether the pixel driving circuit is 6T1C, 6T2C, 4T2C, or the like, and may be different depending on a specific circuit structure. The potential of the anode is equal after the refresh period S1 and after the anode reset period S2 so that the anode charging time in the first emission period E1 and the anode charging period E2 are the same, So that the flicker can be improved.

An exemplary circuit for setting the anode potential after the refresh interval S1 and the anode reset interval S2 in the organic light emitting diode display 100 according to an embodiment of the present invention is described below. In the following, the exemplary circuit is described as having a 6T1C structure, but without being limited thereto, the present invention can be applied to other structures such as 6T3C and 4T3C in which the potential of the anode changes after the refresh interval S1 and after the anode reset interval S2 To be the same in the first embodiment.

3 is an exemplary driving circuit diagram of the pixel shown in Fig. Referring to FIG. 3, the pixel includes a pixel driving circuit 200 that includes an organic light emitting diode (OLED), six transistors, and 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 to T5, and a storage capacitor Cst. The driving TFT DT includes a gate node which is a third node N3 connected to one node of the storage capacitor Cst and a second node N2 electrically connected to the third switching TFT T3 and the second switching TFT T2 ) And a source node which is 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. Thus, 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.

The data voltage Vdata is supplied to the source node of the driving TFT DT while the first switching TFT Tl is turned on and the driving TFT DT is turned on as the third switching TFT T3 is turned on. The data voltage Vdata of the source node of the driving TFT DT is supplied to the third node N3 which is the gate node of the driving TFT DT.

When the third switching TFT T3 is turned on, the second node N2, which is the drain node of the driving TFT DT, and the third node N3, which 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. Therefore, 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 gate node of the driving TFT DT is supplied with the voltage Vdata + Vth.

The source node of the driving TFT DT is electrically connected to the organic light emitting element. 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. Further, it is electrically connected to the anode of the organic light emitting element 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 element Thereby causing the organic light emitting element to emit light.

Hereinafter, the switching TFT and the driving TFT are described as an n-type device, 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 Tl includes a gate node connected to the second scan signal SCAN2 line, a drain node connected to the data line, and a source node connected to the first node N1 which is the source node of the driving TFT DT . Thus, the first switching TFT Tl is turned on or 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 gate of the driver TFT DT And is supplied to the first node N1 which is the source node.

The third switching TFT T3 includes a gate node connected to the first scan signal SCAN1 line, a drain node connected to the source node of the second switching TFT T2 and a drain node connected to the drive TFT DT, And a source node connected to the gate node. Further, the source node of the third switching TFT T3 is connected to one node of the storage capacitor Cst.

Thus, the third switching TFT T3 may be turned on or 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. Thus, the third switching TFT T3 transfers the voltage at the second node N2, which is the drain node of the driving TFT DT, to the voltage at the third node N3, which is the gate node of the driving TFT DT.

Also, the nth emission control signal EM [n] is supplied to the gate node of the second switching TFT T2 with a DC voltage until the nth emission control signal EM [n] is changed from a high state to a low state. Thus, when the third switching TFT T3 is in the turn-on state, only the high potential voltage VDD is supplied to the third node N3 which is the gate node of the driving TFT DT.

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

The second switching TFT T2 may be turned on or turned off by the nth emission control signal EM [n]. That is, when the nth 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 supplied from the source node to the drain node of the driving TFT DT And supplies it to the second node N2.

Then, when the n-th emission control signal EM [n] is in the high state, the third switching TFT T2 supplies the high potential voltage VDD to the drain node of the driving TFT DT, (Hereinafter referred to as " Ids " Therefore, the driving TFT DT regulates the amount of current of the organic light emitting element by the data voltage Vdata.

The fourth switching TFT T4 includes a gate node connected to the n-1th emission control signal EM [n-1] line, a drain node connected to the source node of the driving TFT DT, and a source electrically connected to the organic light- Node. Thus, the fourth switching TFT T4 can be turned on by the (n-1) -th emission control signal EM [n-1].

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

Thus, 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 becomes the fourth node N4, .

When the fourth switching TFT T4, the driving TFT DT and the second switching TFT T2 are turned on during the light emission period, the high-potential voltage VDD is supplied to the driving TFT DT, The driving current Ids is supplied and the organic light emitting element emits light.

The fifth switching TFT T5 includes a gate node connected to the first scan signal SCAN1, a source node connected to the initialization voltage Vinit and one node of the storage capacitor Cst, And a drain node coupled to node N4.

Thus, 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 the high state, the fifth switching TFT T5 is turned on and supplies the initializing voltage Vinit to the fourth node N4. Accordingly, when the fifth switching TFT T5 is turned on by the first scan signal SCAN1, the initializing voltage Vinit is supplied to the fourth node N4, and the data voltage Vdata Is initialized.

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

Specifically, the storage capacitor Cst stores the voltage applied to the gate node of the driving TFT DT. 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 which is electrically connected to the anode of the organic light- do.

That is, the storage capacitor Cst is electrically connected to the third node N3 and the fourth node N4, so that 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 element / RTI >

Specifically, one node of the storage capacitor Cst is supplied with Vdata + Vth as the first switching TFT (T1) and the third switching TFT (T3) are turned on, and the other node is connected to the fifth switching TFT As the transistor T5 is turned on, the initializing voltage Vinit is applied. Therefore, 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 the high state and the second scan signal SCAN2 may be in the high state. Accordingly, the first node N1 and the fourth node N4 can supply a specific voltage through the data line (Vdata) line as the first switching TFT (T1) and the fourth switching TFT (T1) are turned on 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 according to the signal. Will be described later with reference to Figs. 2 and 3 for convenience of explanation.

4A is a waveform diagram illustrating a schematic input / output signal of a pixel driving circuit driven according to an OLED display driving method according to an exemplary embodiment of the present invention. Referring to FIG. 4A, there is shown a schematic input / output signal of a pixel driving circuit operating at an exemplary refresh rate of 60 Hz and an anode reset rate of 120 Hz. The scan signals SCAN1 and SCAN2 are applied in a high state in the refresh period S1 and the light emission control signals EM1 and EM2 are applied in a low state in a part of the refresh period S1. A third node N3 which is a gate node of the driving TFT, a first node N1 which is a source node of the driving TFT, a second node N2 which is a drain node of the driving TFT, and Vgs. 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 interval 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 same voltage V1 and the same voltage Vgs (Vgs) are applied to the first node N1 immediately before the emission periods E1 and E2, and the anode charging time and the current amount of the organic light- , 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 in FIG. 4A. The refresh interval includes an initialization interval, a sampling interval, a programming interval, and an anode voltage preset interval X1. The connection section and the light emitting section are also shown.

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

Referring to FIG. 4B, a 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 interval, a connection interval and a light emission interval, . The duration of each of the initialization period, the sampling period, the programming period, the anode voltage preset period, the connection period, and the light emission period described below may be variously changed according to the embodiment. Hereinafter, it is described that each of the input signals is input at a specific timing. However, the present invention is not limited thereto, and if the condition that the anode voltage or the voltage at the first node N1 is maintained just before the light emitting period is satisfied, Are intended to be included in the scope.

First, at the start of the initialization period, the first scan signal SCAN1 rises to a high state 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 the low state and the n th emission control signal EM [n] is polled in the high state during the initialization period,

Thus, 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. The second switching TFT T2 is turned on only during a period in which the nth emission control signal EM [n] is in the high state and is turned on while the nth emission control signal EM [n] Off.

Thus, the initializing voltage Vinit is supplied to the fourth node N4 through the fifth switching TFT T5, and the high-potential voltage VDD is supplied to the third node N4 while the second switching TFT T2 is turned on. And is supplied to the third node N3 through the TFT T3. That is, the initialization voltage Vinit is supplied to the fourth node N4, which is the source node of the driving TFT DT, so that the data voltage Vdata written in the organic light emitting element is initialized, The node is supplied with the high-potential voltage (VDD).

During the sampling period, the first scan signal SCAN1 is kept in the low state and the second scan signal SCAN2 is rising in the high state. The nth emission control signal EM [n] and the (n-1) th emission control signal EM [n-1] are all kept in the low state during the sampling period.

Then, in the programming period, the first scan signal SCAN1 is raised to a high state and the second scan signal SCAN2 is maintained at a high state. The nth emission control signal EM [n] and the (n-1) th emission control signal EM [n-1] are all kept in the low state during the programming period. 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.

Then, the first scan signal SCAN1 is pulled to a low state before the anode voltage preset period X1, the second scan signal SCAN2 is kept in a high state, and the nth emission control signal EM [n] And the (n-1) -th emission control signal EM [n-1] is held in a low state.

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, Line Vdata.

During the connection period, the first scan signal SCAN1 and the second scan signal SCAN2 are held in a low state. The n-th emission control signal EM [n-1] is maintained in the high state and the nth emission control signal EM [n] is maintained in the low state. During the connection period, only the fourth switching TFT T4 is turned on, and the first, second, third, and fifth switching TFTs T1, T2, T3, Off. Thus, the fourth switching TFT T4 is turned on to electrically connect the first node N1 and the first node N4, and the first node N1 and the fourth node N4 have the same voltage maintain.

During the light emission period, the first scan signal SCAN1 and the second scan signal SCAN2 are held in a low state. The nth emission control signal EM [n] is increased and maintained in the high state during the light emission period. Further, the (n-1) -th emission control signal EM [n-1] also maintains a high state. During the light emission period, the first, third and fifth switching TFTs T3, T5 are turned off, and the second and fourth switching TFTs T4, Is turned on. The drive TFT DT is also turned on to form a path through which the drive current can flow from the high potential voltage (VDD) line to the organic light emitting element. That is, Ioled flows to the organic light emitting element 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 period X2 of the anode reset period will be described. In the anode voltage preset period X2, the first scan signal SCAN1 is in a low state and the second scan signal SCAN2 is held in a high state in the same manner as in the anode voltage preset period X1, The control signal EM [n] is kept in the high state and the (n-1) -th emission control signal EM [n-1] is held in the low state.

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

In various embodiments, the first scan signal, the second scan signal, and the at least one emission control signal are the same when the potential of the anode before the organic light emitting element emits changes during duty variation or refresh rate variation in PWM . In this case, the flicker phenomenon can be suppressed even if the refresh rate and the anode reset rate change at the same time.

5A and 5B are waveform diagrams showing a signal input to a conventional pixel driving circuit and a schematic output signal according to the signal. 5A and 5B are the same as FIGS. 4A and 4B except that there is no node voltage preset interval X1 in the refresh interval. 5A, since the node voltage preset period X1 does not exist in the refresh period, the anode potential at the end of the refresh period or the start of the first light emitting period in the first node N1 is equal to the node potential The anode potential at the end of the reset period X or the second light emission period differs by D1 to cause a difference in the anode charging time in the first and second light emission periods and a difference in Vgs and D4 in the second light emission periods, . Furthermore, the second and third nodes N2 and N3 may be different by D2 and D3.

Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, it is to be understood that the present invention is not limited to those embodiments and various changes and modifications may be made without departing from the scope of the present invention. . Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. Therefore, it should be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

100: organic light emitting display
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 including a pixel driving circuit and an anode, an organic light emitting element, and a cathode,
Applying a first scan signal to the pixel driving circuit in a first period;
Applying a second scan signal to the pixel driving circuit at a period different from the first period; And
Applying at least one control signal to the pixel driving circuit,
Wherein the first scan signal, the second scan signal, and the at least one control signal are applied to the organic light emitting display device so that the potential of the anode after the refresh operation of the pixel drive circuit and the anode after the anode reset operation are the same. Way. The method according to claim 1,
Wherein the refresh operation includes a period during which the first scan signal and the second scan signal are applied together,
Wherein the anode reset operation includes a period during 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 comprising:
A first pixel drive switching element for outputting a data signal to a first node according to the second scan signal,
A second pixel drive switching element for outputting a drive voltage to a second node in accordance with a second pixel control signal which is one of the at least one control signal,
A third pixel drive switching element including a gate to which the first scan signal is applied, the third pixel drive switching element being disposed between the second node and the third node,
A pixel driving element including a gate connected to the third node and disposed between the first node and the second node,
A fourth pixel drive 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 which is disposed between the first node and the fourth node,
And a fifth pixel drive switching element for outputting an initialization signal to the fourth node according to the first scan signal,
Wherein the step of applying at least one control signal to the pixel driving circuit comprises the steps of: during the refresh operation and the anode reset operation, applying the first scan signal, the second scan signal, the first pixel control signal, And applying the same to the organic light emitting display device. The method of claim 3,
Wherein the potential of the fourth node in the refresh operation or immediately after the refresh operation is equal to the potential of the fourth node after the anode reset operation. The method of claim 3,
Wherein the first pixel control signal and the second scan signal are simultaneously applied with a turn-on voltage in the refresh operation or immediately after the refresh operation. The method according to claim 1,
Wherein the first period is at least two times faster than the second period. The method according to claim 1,
Wherein 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 element emits is the same even during the duty variation or the refresh rate fluctuation in the PWM, A method of driving an organic light emitting display device. A pixel driving circuit, an anode, an organic light emitting element, and a cathode,
The pixel driving circuit comprising:
A first pixel drive switching element for outputting a data signal to a first node according to a second scan signal,
A second pixel driving switching element for outputting a driving voltage to a second node according to a second pixel control signal,
A third pixel drive switching element including a gate to which a first scan signal is applied, the third pixel drive switching element being disposed between the second node and the third node,
A pixel driving element including a gate connected to the third node and disposed between the first node and the second node,
A fourth pixel drive switching element including a gate to which a first pixel control signal is applied, the fourth pixel drive switching element being disposed between the first node and the fourth node,
And a fifth pixel drive switching element for outputting an initialization signal to the fourth node according to the first scan signal,
The first scan signal and the second scan signal are applied together in a first period,
A second period in which only the second scan signal is applied and the first scan signal is not applied is a second period,
And the pixel driving circuit is configured to make the potential of the anode equal after the first section and the second section. 9. The method of claim 8,
Wherein the first pixel control signal has a turn-on voltage and the second scan signal has a turn-on voltage. 9. The method of claim 8,
Wherein the first period is at least twice as fast as the second period.

Images