CN111261112B - Pixel driving circuit, display panel, display device and pixel driving method - Google Patents

Pixel driving circuit, display panel, display device and pixel driving method Download PDF

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Publication number
CN111261112B
CN111261112B CN202010202349.9A CN202010202349A CN111261112B CN 111261112 B CN111261112 B CN 111261112B CN 202010202349 A CN202010202349 A CN 202010202349A CN 111261112 B CN111261112 B CN 111261112B
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node
transistor
level
switch module
module
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CN111261112A (en
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袁志东
李永谦
袁粲
李蒙
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BOE Technology Group Co Ltd
Hefei BOE Zhuoyin Technology Co Ltd
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BOE Technology Group Co Ltd
Hefei BOE Zhuoyin Technology Co Ltd
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0233—Improving the luminance or brightness uniformity across the screen
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing
    • G09G2320/046—Dealing with screen burn-in prevention or compensation of the effects thereof

Abstract

The embodiment of the application provides a pixel driving circuit, a display panel, a display device and a pixel driving method. The pixel driving circuit includes: the first end, the second end and the control end of the first switch module are respectively and electrically connected with the data signal line, the first node and the first grid signal line; the first end and the second end of the charge storage module are respectively and electrically connected with the first node and the second node; the first end, the second end and the control end of the driving module are respectively and electrically connected with the first level end, the second node and the first node; and the first end, the second end, the third end and the control end of the second switch module are respectively and electrically connected with the initialization signal line, the third node, the second node and the second grid signal line, and the third node is used as the third end of the charge storage module. The embodiment of the application realizes the compensation of the light-emitting device OLED and reduces or eliminates the problem of uneven light emission caused by the aging effect of the light-emitting device OLED.

Description

Pixel driving circuit, display panel, display device and pixel driving method
Technical Field
The present application relates to the field of display technologies, and in particular, to a pixel driving circuit, a display panel, a display device, and a pixel driving method.
Background
In the design of an Active-matrix Organic Light Emitting Diode (AMOLED) large-sized display, the brightness of the product is not only determined by a Thin Film Transistor (TFT), but also the final display effect is affected by an Organic Light Emitting Diode (OLED).
At present, the driving TFT is generally compensated by an electrical compensation method, and the influence of the threshold voltage Vth and mobility of the driving TFT on the display effect can be effectively reduced by the compensation. However, the light emitting device OLED may be aged after emitting light for a long time, resulting in non-uniform light emission.
Disclosure of Invention
The application provides a pixel driving circuit, a display panel, a display device and a pixel driving method aiming at the defects of the prior art, and aims to solve the technical problem of uneven light emission caused by the aging phenomenon of a light emitting device OLED in the prior art.
In a first aspect, an embodiment of the present application provides a pixel driving circuit, including:
the first end, the second end and the control end of the first switch module are respectively and electrically connected with the data signal line, the first node and the first grid signal line;
the first end and the second end of the charge storage module are respectively and electrically connected with the first node and the second node;
the first end, the second end and the control end of the driving module are respectively and electrically connected with the first level end, the second node and the first node; the second node is electrically connected with the first end of the light-emitting device, and the second end of the light-emitting device is electrically connected with the second level end;
and the first end, the second end, the third end and the control end of the second switch module are respectively and electrically connected with the initialization signal line, the third node, the second node and the second grid signal line, and the third node is used as the third end of the charge storage module.
In one possible implementation, the charge storage module includes:
the first pole of the first capacitor is used as the first end of the charge storage module, and the second pole of the first capacitor is electrically connected with the third node;
and the first pole of the second capacitor is electrically connected with the third node, and the second pole of the second capacitor is used as the second end of the charge storage module.
In one possible implementation, the first switch module includes:
the first transistor, the first pole, the second pole and the control pole are respectively used as a first end, a second end and a control end of the first switch module.
In one possible implementation, the driving module includes:
and the first pole, the second pole and the control pole of the second transistor are respectively used as a first end, a second end and a control end of the driving module.
In one possible implementation, the second switch module includes: a third transistor and a fourth transistor;
the first pole of the third transistor and the first pole of the fourth transistor are jointly used as the first end of the second switch module;
the second pole of the third transistor is used as the second end of the second switch module;
the second pole of the fourth transistor is used as the third end of the second switch module;
and the control electrode of the third transistor and the control electrode of the fourth transistor are jointly used as the control end of the second switch module.
In one possible implementation manner, each transistor is a thin film transistor, and a control electrode of each transistor is a gate electrode of the thin film transistor;
if the first pole of the transistor is the source electrode of the thin film transistor, the second pole of the transistor is the drain electrode of the thin film transistor;
if the first pole of the transistor is the drain of the thin film transistor, the second pole of the transistor is the source of the thin film transistor.
In a second aspect, an embodiment of the present application provides a display panel including the pixel driving circuit of the first aspect.
In a third aspect, an embodiment of the present application provides a display device, including the pixel driving circuit of the first aspect or the display panel of the second aspect.
In a fourth aspect, an embodiment of the present application provides a pixel driving method applied to the pixel driving circuit of the first aspect, including:
in the first stage, the first switch module and the second switch module are both switched on when receiving a first level signal through respective control ends, the first switch module outputs a first data signal received through the first end to a first node, and the second switch module outputs an initialization signal received through the first end to a second node and a third node;
in the second stage, the first switch module and the second switch module are disconnected when receiving a second level signal through respective control ends, the level variation of the second node is a third level, and the first end of the charge storage module raises the third level along with the second end of the charge storage module, which is electrically connected with the second node; the third level is the sum of the level of the second level end and the voltage across the light-emitting device;
in a third stage, the second switch module is switched on when receiving the first level signal through the control end of the second switch module, the first switch module is kept switched off, the second switch module outputs the initialization signal to the second node and the third node, the first end of the charge storage module changes the same level variation along with the third end of the charge storage module, which is electrically connected with the third node, so that the potential of the first node electrically connected with the first end of the charge storage module is positively correlated with the cross voltage of the light-emitting device, and the driving module outputs a driving current to the light-emitting device according to the potential of the first node; the driving current is positively correlated with the voltage across the light emitting device.
In a possible implementation manner, in a first stage, when receiving a first level signal through respective control terminals, the first switch module and the second switch module are both turned on, the first switch module outputs a second data signal received through the first terminal thereof to the first node, and the second switch module outputs an initialization signal received through the first terminal thereof to the second node and the third node; the second data signal is the sum of the level of the first data signal and the threshold voltage of the second transistor of the driving module.
The technical scheme provided by the embodiment of the application has the following beneficial technical effects:
the pixel driving method of the embodiment of the application is based on the pixel driving circuit of the embodiment of the application, and in the first stage, the first switch module and the second switch module are controlled to be both switched on, the first data signal is output to the first node through the first switch module, and meanwhile the initialization signal is respectively input to the second node and the third node through the second switch module. In the second stage, the first switch module and the second switch module are controlled to be switched off, the level variation of the second node is a third level, the third level is the sum of the level of the second level end and the cross voltage of the light emitting device, because the total charge of the charge storage module is kept unchanged, the first node electrically connected with the first end of the charge storage module is correspondingly lifted to the third level under the action of the charge storage module, and meanwhile, the potential of the third node serving as the third end of the charge storage module is associated with the cross voltage of the light emitting device, so that the driving current in the subsequent third stage is associated with the cross voltage of the light emitting device conveniently. In a third stage, the second switch module is controlled to be switched on, the first switch module is controlled to be switched off, the first end of the charge storage module changes the same level variation along with the third end of the charge storage module, so that the potential of the first node is positively correlated with the cross voltage of the light emitting device, and the driving module outputs driving current to the light emitting device OLED according to the potential of the first node, so that the driving current output by the driving module is positively correlated with the cross voltage of the light emitting device. Due to the aging phenomenon after the light-emitting device OLED emits light for a long time, under the condition of the same driving current, the voltage across the light-emitting device OLED is increased, the light-emitting efficiency is reduced, and the light-emitting is not uniform. The embodiment of the application can realize that the driving current output by the driving module is positively correlated with the cross voltage of the light-emitting device, namely when the cross voltage of the light-emitting device is increased, the driving current is correspondingly increased, so that the compensation of the light-emitting device OLED is realized, and the problem of uneven light emission caused by the aging effect of the light-emitting device OLED is reduced or eliminated. The pixel driving circuit of the embodiment of the application can realize the compensation of the circuit structure of the pixel driving circuit on the aging of the OLED through the time sequence control of each signal.
In the pixel driving method according to the embodiment of the application, in the second stage, the potential of the second node becomes the sum of the level of the second level end and the cross voltage of the light emitting device, the potential of the second node can be known by detection, since the level of the second level end is known, the cross voltage Voled-th of the light emitting device can be detected equivalently, and the driving current can be detected at the same time. Therefore, the pixel driving circuit of the embodiment of the present application not only realizes aging compensation of the self circuit structure to the light emitting device OLED, but also realizes external compensation by adjusting the level of the input data signal, that is, the pixel driving circuit of the embodiment of the present application can simultaneously realize internal compensation and external compensation of the light emitting device OLED.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic structural diagram of a pixel driving circuit according to an embodiment of the present disclosure;
fig. 2 is a flowchart of a pixel driving method according to an embodiment of the present disclosure;
fig. 3 is a timing diagram of a pixel driving method according to an embodiment of the present disclosure;
fig. 4 is a timing diagram of an image driving mode of a pixel driving circuit according to an embodiment of the present disclosure;
fig. 5 is a timing diagram illustrating a compensation mode of a threshold voltage Vth of a second transistor of a driving module of a pixel driving circuit according to an embodiment of the present disclosure;
fig. 6 is a timing diagram illustrating a compensation mode of mobility of a second transistor of a driving module of a pixel driving circuit according to an embodiment of the present disclosure.
Reference numerals:
1-a first switch module, 2-a charge storage module, 3-a drive module and 4-a second switch module;
DL-data signal Line, Sense Line-initialization signal Line;
a-a first node, B-a second node, C-a third node;
cst 1-first capacitor, Cst 2-second capacitor, T1-first transistor, T2-second transistor, T3-third transistor, T4-fourth transistor, OLED-light emitting device;
VDD-first level terminal, VSS-second level terminal;
g1-first and second gate signal lines G2;
g1(n) -the first gate signal line of the nth row, G2(n) -the second gate signal line of the nth row.
Detailed Description
Reference will now be made in detail to the present application, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar parts or parts having the same or similar functions throughout. In addition, if a detailed description of the known art is not necessary for illustrating the features of the present application, it is omitted. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present application and are not to be construed as limiting the present application.
It will be understood by those within the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. Further, "connected" or "coupled" as used herein may include wirelessly connected or wirelessly coupled. As used herein, the term "and/or" includes all or any element and all combinations of one or more of the associated listed items.
The inventors of the present application have conducted research and found that AMOLED is expected to replace liquid crystal as the mainstream choice of next generation displays due to its high contrast, wide viewing angle and fast response speed. At present, the driving TFT is generally compensated by an electrical compensation method, and the influence of the threshold voltage Vth and mobility of the TFT on the display effect can be effectively reduced by the compensation. However, for the light emitting device OLED, although there is a technology to electrically compensate the aging of the OLED by grabbing the voltage across the OLED-th variation, the technology is limited by the difference of the OLED itself, and the implementation is more complicated and difficult. The characteristics of the OLED are variable, and the aging period is long, so that the later-stage brightness uniformity of the product cannot be controlled, and the product brand is affected, and it is known that the OLED has an aging phenomenon after emitting light for a long time, and under the same driving current, the voltage across the OLED increases, and the light emitting efficiency decreases accordingly, and in order to eliminate the uneven light emission caused by the aging phenomenon of the EL device, a pixel driving circuit and a pixel driving method capable of eliminating the aging effect need to be invented.
The present application provides a pixel driving circuit, a display panel, a display device and a pixel driving method, which aim to solve the above technical problems in the prior art.
The following describes the technical solutions of the present application and how to solve the above technical problems with specific embodiments.
An embodiment of the present application provides a pixel driving circuit, and as shown in fig. 1, the pixel driving circuit includes: a first switching module 1, a charge storage module 2, a driving module 3 and a second switching module 4.
The first terminal, the second terminal, and the control terminal of the first switch module 1 are electrically connected to the data signal line DL, the first node a, and the first gate signal line G1, respectively.
The first and second terminals of the charge storage module 2 are electrically connected to the first and second nodes a and B, respectively.
A first end, a second end and a control end of the driving module 3 are respectively and electrically connected with a first level end VDD, a second node B and a first node A; the second node B is electrically connected to a first terminal of the light emitting device OLED, and a second terminal of the light emitting device OLED is electrically connected to a second level terminal VSS. The first end and the second end of the light emitting device OLED are respectively an anode and a cathode.
The first terminal, the second terminal, the third terminal, and the control terminal of the second switch module 4 are electrically connected to the initialization signal Line, a third node C, a second node B, and a second gate signal Line G2, respectively, and the third node C is used as the third terminal of the charge storage module 2.
In some embodiments, referring to fig. 1, the charge storage module 2 comprises: a first capacitor Cst1 and a second capacitor Cst 2. A first capacitor Cst1, having a first pole as a first terminal of the charge storage module 2 and a second pole electrically connected to the third node C; and a second capacitor Cst2, having a first pole electrically connected to the third node C and a second pole serving as a second terminal of the charge storage module 2. Optionally, the first capacitor Cst1 and the second capacitor Cst2 are both storage capacitors.
In some embodiments, referring to fig. 1, the first switch module 1 comprises: a first transistor T1; the first pole, the second pole and the control pole of the first transistor T1 are respectively used as the first end, the second end and the control end of the first switch module 1.
In some embodiments, referring to fig. 1, the driving module 3 comprises: a second transistor T2; the first pole, the second pole and the control pole of the second transistor T2 are respectively used as the first end, the second end and the control end of the driving module 3. The second transistor T2 is a driving TFT. Specifically, S, D and G correspond to the source, drain and gate of the second transistor T2, respectively.
In some embodiments, referring to fig. 1, the second switch module 4 comprises: a third transistor T3 and a fourth transistor T4. A first pole of the third transistor T3 and a first pole of the fourth transistor T4 are commonly used as a first terminal of the second switch module 4; the second pole of the third transistor T3 serves as the second terminal of the second switch module 4; a second pole of the fourth transistor T4 serves as a third terminal of the second switching module 4; a control electrode of the third transistor T3 and a control electrode of the fourth transistor T4 together serve as a control terminal of the second switch module 4.
In some embodiments, each transistor is a thin film transistor, and the control electrode of each transistor is a gate electrode of the thin film transistor; if the first pole of the transistor is the source electrode of the thin film transistor, the second pole of the transistor is the drain electrode of the thin film transistor; if the first pole of the transistor is the drain of the thin film transistor, the second pole of the transistor is the source of the thin film transistor.
Alternatively, each of the transistors may be an N-type TFT or a P-type TFT, and when each of the transistors is an N-type TFT, the pixel driving circuit is formed as shown in fig. 1.
It can be understood by those skilled in the art that the circuit connection manner shown in fig. 1 is only an example of the pixel driving circuit provided in the embodiment of the present application, and when each transistor is a P-type TFT or the first pole and the second pole of each transistor are respectively different poles of a TFT, the electrical connection manner of each element in the pixel driving circuit provided in the embodiment of the present application can be adaptively adjusted, and the adaptively adjusted electrical connection manner still belongs to the protection scope of the embodiment of the present application.
Based on the same inventive concept, embodiments of the present application provide a display panel including a pixel driving circuit of embodiments of the present application.
Based on the same inventive concept, embodiments of the present application provide a display device including the pixel driving circuit of the embodiments of the present application or the display panel of the second aspect.
Based on the same inventive concept, an embodiment of the present application provides a pixel driving method, which is applied to a pixel driving circuit of the embodiment of the present application, and as shown in fig. 2, the pixel driving method includes:
s201, in a first stage, the first switch module 1 and the second switch module 4 are both turned on when receiving the first level signal through respective control terminals, the first switch module 1 outputs the first data signal Vdata received through the first terminal thereof to the first node a, and the second switch module 4 outputs the initialization signal Vref received through the first terminal thereof to the second node B and the third node C.
S202, in a second stage, the first switch module 1 and the second switch module 4 are turned off when receiving the second level signal through their respective control terminals, the level variation of the second node B is a third level, and the first terminal of the charge storage module 2 is raised by the third level along with the charge storage module 2 and the second terminal electrically connected to the second node B; the third level is a level V of the second level terminal VSSSSAnd the sum of the voltage across Voled-th of the light emitting device OLED.
S203, a third stage, the second switch module 4 is turned on when receiving the first level signal through the control terminal thereof, the first switch module 1 keeps off, the second switch module 4 outputs the initialization signal Vref to the second node B and the third node C, the first terminal of the charge storage module 2 changes the same level variation amount along with the third terminal of the charge storage module 2 electrically connected to the third node C, so that the potential of the first node a electrically connected to the first terminal of the charge storage module 2 is positively correlated to the voltage across Voled-th of the light emitting device OLED, and the driving module 3 outputs the driving current I according to the potential of the first node aDSTo the light-emitting device OLED; drive current IDSIs positively correlated with the voltage across Voled-th of the light emitting device OLED.
The second switch module 4 is turned on when receiving the first level signal through the control end thereof, the first switch module 1 is kept turned off, and the driving current output by the driving module 3 is positively correlated with the cross voltage of the light emitting device OLED to realize the compensation of the light emitting device OLED.
Optionally, the first level signal is at a high level, and the second level signal is at a low level; or, the first level signal is at a low level, and the second level signal is at a high level.
The pixel driving method according to the embodiment of the present application is based on the pixel driving circuit according to the embodiment of the present application, and in the first stage, the first switch module 1 and the second switch module 4 are controlled to be both turned on, the first data signal Vdata is output to the first node a through the first switch module 1, and the initialization signal Vref is respectively input to the second node B and the first node a through the second switch module 4And (4) three nodes C. In the second stage, the first switch module 1 and the second switch module 4 are both controlled to be turned off, the final potential of the second node B is changed to a third level, and the third level is the sum of the level of the second level terminal VSS and the voltage across Voled-th of the light emitting device OLED. The level variation of the second node B is a third level, since the total charge of the charge storage module 2 remains unchanged, the first end of the charge storage module 2, i.e. the first node a, is also correspondingly raised to the third level under the action of the charge storage module 2, and meanwhile, the potential of the third node C, which is the third end of the charge storage module 2, is associated with the voltage-across th of the light emitting device OLED, so that the driving current I at the third stage is facilitatedDSAn association is made with the voltage across Voled-th of the light emitting device OLED. In a third phase, the second switch module 4 is controlled to be switched on, the first switch module 1 is switched off, the first end of the charge storage module 2 changes the same level variation along with the third end of the charge storage module 2, so that the potential of the first node a is positively correlated with the cross voltage of the light emitting device OLED, and the driving module 3 outputs a driving current I according to the potential of the first node aDSTo the light-emitting device OLED, so that the drive current I output by the drive module 3DSThe voltage across Voled-th of the light emitting device OLED is also positively correlated.
The same driving current I is caused due to the aging phenomenon after the long-term luminescence of the light-emitting device OLEDDSIn this case, the voltage across the light emitting device OLED increases, and the light emitting efficiency decreases accordingly, resulting in non-uniform light emission. The pixel driving circuit and the pixel driving method in the embodiment of the application can realize the driving current I output by the driving module 3DSIs positively correlated with the voltage across Voled-th of the light emitting device OLED, i.e. when the voltage across Voled-th of the light emitting device OLED increases, the driving current IDSAnd correspondingly increased, thereby realizing the compensation of the light-emitting device OLED and reducing or eliminating the problem of uneven light emission caused by the aging effect of the light-emitting device OLED. The pixel driving circuit of the embodiment of the application can realize the compensation of the circuit structure of the pixel driving circuit on the aging of the light emitting device OLED through the time sequence control of each signal.
In some embodiments, in the second phase, that is, in step S201, the first switch module 1 and the second switch module 4 are both turned on when receiving the first level signal through their respective control terminals, the first switch module 1 outputs the second data signal received through its first terminal to the first node a, and the second switch module 4 outputs the initialization signal Vref received through its first terminal to the second node B and the third node C; the second data signal is a sum of a level of the first data signal Vdata and a threshold voltage Vth of the second transistor T2 of the driving module 3.
In the pixel driving method of the embodiment of the application, in the second stage, the potential of the second node B will become the sum of the level of the second level terminal and the voltage Voled-th of the light emitting device OLED, and the potential of the second node B can be known by detecting, since the level V of the second level terminal VSS is knownSSSo that the voltage across the OLED can be detected and the driving current I can be detectedDSAt a drive current IDSAnd the threshold voltage Vth of the second transistor T2 of the driving module 3 can be obtained under the known condition of the cross voltage Voled-th, and based on the structure of the pixel driving circuit of the embodiment of the present application, the threshold voltage Vth of the second transistor T2 can be offset after the level of the first data signal Vdata is increased by the threshold voltage Vth, thereby further realizing the compensation of the light emitting device OLED. Therefore, the pixel driving circuit of the embodiment of the present application not only realizes aging compensation of the self circuit structure to the light emitting device OLED, but also realizes external compensation by adjusting the level of the input data signal, that is, the pixel driving circuit and the pixel driving method of the embodiment of the present application can realize internal compensation and external compensation of the light emitting device OLED at the same time.
The following describes a pixel driving method provided in an embodiment of the present application, taking a case where each transistor is an N-type TFT as an example, with reference to a timing chart of each control of the pixel driving circuit shown in fig. 1 and the pixel driving method shown in fig. 3.
Referring to fig. 3, the first gate signal Line G1(n) of the nth row and the second gate signal Line G2(n) of the nth row in the figure may be switched between a first level (corresponding to a high level VGH) and a second level (corresponding to a low level VGL), respectively, the data signal Line DL for outputting the first data signal Vdata, and the initialization signal Line Sense Line for outputting the initialization signal Vref. Meanwhile, reference numerals 1, 2, and 3 in the drawings correspond to the first stage, the second stage, and the third stage, respectively.
The first phase, which is an initial read data signal phase:
in the first stage, the first gate signal Line G1 and the second gate signal Line G2 are controlled to output a first level (corresponding to a high level VGH), the first transistor T1, the third transistor T3 and the fourth transistor T4 are all turned on, the first data signal Vdata is written by the first transistor T1, the initialization signal Vref is written by the third transistor T3 and the fourth transistor T4 to the third node C and the fourth node D through the initialization signal Line Sense Line, and the level V of the first level terminal VDD is controlled to output a first level (corresponding to a high level VGH)DDAt a high level, the light emitting device OLED does not emit light at this time, a voltage difference across the second capacitor Cst2 is 0, and a voltage difference across the first capacitor Cst1 is a difference Vgs between a gate (corresponding to a G point) voltage and a source (corresponding to an S point) voltage of the second transistor T2, where Vgs is represented by formula (1):
Vgs＝Vdata-Vref (1)
the second stage is a stage of extracting the over-voltage Voled-th:
the first gate signal line G1 and the second gate signal line G2 are controlled to output a second level (corresponding to a low level VGL), the S-point potential is the potential of the second node B, the S-point potential of the second transistor T2 is also charged by the first level terminal VDD, the first transistor T1, the third transistor T3 and the fourth transistor T4 are all turned off, and the Vgs is kept unchanged because the total charge Q of the first capacitor Cst1 and the second capacitor Cst2 is kept unchanged. In the second stage, the potential at the point S, i.e., the level change amount of the second node B, is a third level, which is the level V of the second level terminal VSSSSAnd the sum of the voltage across Voled-th of the light-emitting device OLED, i.e. VSS+ Voled-th, the G-point and S-point raise the third level at the same time, and finally the G-point potential is as shown in equation (2):
VG＝Vdata-Vref+Vss+Voled-th (2)
analyzing the potential of the third node C, the potential of the third node C is shown in formula (3):
VC＝vref+(Cst1/(Cst1+Cst2))(Voled-th+Vss) (3)
in equation (3), Cst1 is the capacitance of the first capacitor Cst1, and Cst2 is the capacitance of the second capacitor Cst 2.
The third stage is a reset stage:
the first gate signal line G1 is controlled to output a second level (corresponding to a low level VGL), the second gate signal line G2 outputs a first level (corresponding to a high level VGH), the third transistor T3 and the fourth transistor T4 are turned on, the first transistor T1 is turned off, the potential of the third node C is reset to the initialization signal Vref, the first transistor T1 is turned off and the potential of the G-point of the second transistor T2 is changed along with the potential of the third node C due to the conservation of the charge of the first capacitor Cst 1. The initialization signal Line outputs Vref, and the potential variation value of the third node C can be obtained by equation (3), and is shown in equation (4):
△VC＝-(Cst1/Cst1+Cst2)(Voled-th+Vss) (4)
adding the formula (2) and the formula (4) to obtain the final G terminal potential of the second transistor T2, wherein the G terminal potential of the second transistor T2 is shown in the formula (5):
VG＝Vdata+(Cst2/(Cst1+Cst2))Voled-th+Vss) (5)
the value of the final OLED emission input Vgs is then as shown in equation (6):
VGS＝Vdata+(Cst2/Cst1+Cst2)(Voled-th+Vss)-vref (6)
the Vdata and V of Vgs of the final second transistor T2 can be obtained by observing equation (6)SSVref and Voled-th, in practice, VSSThe difference is very small, typically 0V, Vref is also given to 0V, let a be Cst2/Cst1+ Cst2, and equation (6) is simplified to obtain equation (7) as follows:
VGS＝Vdata+aVoled-th (7)
i of the second transistor T2DSAs shown in equation (8):
IDS＝k(Vdata+aVoled-th-Vth)2 (8)
observe equation (8), k is a positive value, drive current IDSVoltage V across OLEDoled-thPositive correlation, i.e. when the voltage V is exceededoled-thAt the time of increase, the drive current IDSAnd the size of the light emitting device OLED is increased, so that the compensation of the light emitting device OLED is realized, and the problem of uneven light emission caused by the aging effect of the light emitting device OLED is reduced or eliminated.
Meanwhile, the pixel driving circuit of the embodiment of the application can still capture the threshold voltage Vth of the second transistor T2 through an external compensation method, and cancel the threshold voltage Vth by adding the value of the first data signal Vdata to the second data signal Vdata + Vthdata2As shown in formula (9):
Vdata2＝Vdata+Vth (9)
substituting equation (9) for equation (8) yields equation (10) as follows:
IDS＝k(Vdata2+aVoled-th)2 (10)
looking at equation (10), when the second data signal Vdata2Vdata + Vth cancels the threshold voltage Vth of the second transistor T2, further driving the current IDSVoltage V across OLEDoled-thThereby realizing the compensation of the light emitting device OLED. Therefore, the pixel driving circuit of the embodiment of the application not only realizes aging compensation of the self circuit structure to the light emitting device OLED, but also can realize external compensation by adjusting the level of the input data signal, namely, can realize internal compensation and external compensation of the light emitting device OLED at the same time.
Referring to fig. 4, when the pixel driving circuit applied to the embodiment of the present application performs the image driving mode, the first gate signal line G1(n) of the nth row and the second gate signal line G2(n) of the nth row are both controlled to output the first level (corresponding to the high level VGH).
Referring to fig. 5, when the pixel driving circuit applied to the embodiment of the present application performs the compensation mode for the threshold voltage Vth of the second transistor T2, the first gate signal line G1(n) of the nth row and the second gate signal line G2(n) of the nth row are both controlled to output the first level (corresponding to the high level VGH), and the output time of the first level of the compensation mode for the threshold voltage Vth is longer than that of the first level of the image driving mode.
Referring to fig. 6, when the pixel driving circuit applied to the embodiment of the present application performs the compensation mode of the mobility of the second transistor T2, the first gate signal line G1(n) of the nth row is controlled to sequentially output the first level (corresponding to the high level VGH), the second level (corresponding to the high level VGL), and the first level (corresponding to the high level VGH), and at this stage, the second gate signal line G2(n) of the nth row is kept to output the first level (corresponding to the high level VGH).
By applying the embodiment of the application, at least the following beneficial effects can be realized:
(1) the pixel driving circuit and the pixel driving method can achieve positive correlation between driving current output by the driving module and the cross voltage of the light emitting device OLED, namely when the cross voltage of the light emitting device OLED is increased, the driving current is correspondingly increased, so that compensation of the light emitting device OLED is achieved, and the problem of uneven light emission caused by the aging effect of the light emitting device OLED is reduced or eliminated. The pixel driving circuit of the embodiment of the application can realize the compensation of the circuit structure of the pixel driving circuit on the aging of the OLED through the time sequence control of each signal.
(2) The pixel driving circuit and the pixel driving method of the embodiment of the application not only realize aging compensation of the self circuit structure to the light emitting device OLED, but also realize external compensation by adjusting the level of the input data signal, namely realize internal compensation and external compensation of the light emitting device OLED at the same time.
(3) The pixel driving circuit of the embodiment of the application can also realize image driving, compensation of the threshold voltage Vth of the second transistor T2 and compensation of the mobility of the second transistor T2 through time sequence control, can realize switching among various modes through time sequence control of various control signals, realizes multiple functions, enables the pixel driving circuit to emit light uniformly, and improves the display effect.
Those of skill in the art will appreciate that the various operations, methods, steps in the processes, acts, or solutions discussed in this application can be interchanged, modified, combined, or eliminated. Further, other steps, measures, or schemes in various operations, methods, or flows that have been discussed in this application can be alternated, altered, rearranged, broken down, combined, or deleted. Further, steps, measures, schemes in the prior art having various operations, methods, procedures disclosed in the present application may also be alternated, modified, rearranged, decomposed, combined, or deleted.
In the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a particular orientation, be constructed in a particular orientation, and be operated, and thus should not be construed as limiting the present application.
The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless otherwise specified.
In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.
In the description herein, particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.
It should be understood that, although the steps in the flowcharts of the figures are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and may be performed in other orders unless explicitly stated herein. Moreover, at least a portion of the steps in the flow chart of the figure may include multiple sub-steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, which are not necessarily performed in sequence, but may be performed alternately or alternately with other steps or at least a portion of the sub-steps or stages of other steps.
The foregoing is only a partial embodiment of the present application, and it should be noted that, for those skilled in the art, several modifications and decorations can be made without departing from the principle of the present application, and these modifications and decorations should also be regarded as the protection scope of the present application.

Claims (10)

1. A pixel driving circuit, comprising:
the first end, the second end and the control end of the first switch module are respectively and electrically connected with the data signal line, the first node and the first grid signal line;
a first end and a second end of the charge storage module are respectively and electrically connected with the first node and the second node;
the first end, the second end and the control end of the driving module are respectively and electrically connected with the first level end, the second node and the first node; the second node is electrically connected with a first end of the light-emitting device, and a second end of the light-emitting device is electrically connected with a second level end;
the first end, the second end, the third end and the control end of the second switch module are respectively and electrically connected with the initialization signal line, the third node, the second node and the second grid signal line, and the third node is used as the third end of the charge storage module;
in a first stage, when the first switch module and the second switch module receive a first level signal through respective control terminals and are turned on, the first terminal of the charge storage module receives a first data signal, and the second terminal and the third terminal of the charge storage module receive an initialization signal; in a second stage, when the first switch module and the second switch module receive a second level signal through respective control terminals and are disconnected, the first end of the charge storage module rises to a third level along with the second end of the charge storage module; in a third phase, the second switch module receives a first level signal through a control end thereof, and when the first switch module is kept disconnected, the first end of the charge storage module changes the same level change amount along with the third end of the charge storage module, so that the potential of the first node electrically connected with the first end of the charge storage module is positively correlated with the voltage across the light-emitting device; the third level is a sum of a level of the second level terminal and a cross voltage of the light emitting device.
2. The pixel driving circuit according to claim 1, wherein the charge storage module comprises:
the first pole of the first capacitor is used as the first end of the charge storage module, and the second pole of the first capacitor is electrically connected with the third node;
and the first pole of the second capacitor is electrically connected with the third node, and the second pole of the second capacitor is used as the second end of the charge storage module.
3. The pixel driving circuit according to claim 1, wherein the first switching module comprises:
and the first electrode, the second electrode and the control electrode of the first transistor are respectively used as a first end, a second end and a control end of the first switch module.
4. The pixel driving circuit according to claim 1, wherein the driving module comprises:
and the first pole, the second pole and the control pole of the second transistor are respectively used as the first end, the second end and the control end of the driving module.
5. The pixel driving circuit according to claim 1, wherein the second switching module comprises: a third transistor and a fourth transistor;
a first pole of the third transistor and a first pole of the fourth transistor are used together as a first end of the second switch module;
a second pole of the third transistor is used as a second end of the second switch module;
a second pole of the fourth transistor is used as a third end of the second switch module;
and the control electrode of the third transistor and the control electrode of the fourth transistor are jointly used as the control end of the second switch module.
6. The pixel driving circuit according to any one of claims 3 to 5, wherein each transistor is a thin film transistor, and a control electrode of each transistor is a gate electrode of the thin film transistor;
if the first pole of the transistor is the source electrode of the thin film transistor, the second pole of the transistor is the drain electrode of the thin film transistor;
and if the first pole of the transistor is the drain electrode of the thin film transistor, the second pole of the transistor is the source electrode of the thin film transistor.
7. A display panel comprising the pixel drive circuit according to any one of claims 1 to 6.
8. A display device comprising the pixel driving circuit according to any one of claims 1 to 6 or the display panel according to claim 7.
9. A pixel driving method applied to the pixel driving circuit according to any one of claims 1 to 6, comprising:
in the first stage, the first switch module and the second switch module are both turned on when receiving a first level signal through respective control terminals, the first switch module outputs a first data signal received through a first terminal thereof to the first node, and the second switch module outputs an initialization signal received through the first terminal thereof to a second node and a third node;
in a second stage, the first switch module and the second switch module are disconnected when receiving a second level signal through respective control ends, the level variation of the second node is a third level, and the first end of the charge storage module raises the third level along with a second end of the charge storage module electrically connected with the second node; the third level is the sum of the level of the second level end and the voltage across the light-emitting device;
a third stage in which the second switch module is turned on when receiving a first level signal through a control terminal thereof, the first switch module is kept off, the second switch module outputs the initialization signal to a second node and a third node, a first terminal of the charge storage module changes by the same level change amount as a third terminal to which the charge storage module is electrically connected changes so that a potential of the first node to which the first terminal of the charge storage module is electrically connected positively correlates with a voltage across the light emitting device, and the driving module outputs a driving current to the light emitting device according to the potential of the first node; the driving current is positively correlated with the voltage across the light emitting device.
10. The pixel driving method according to claim 9, further comprising:
in a first stage, the first switch module and the second switch module are both turned on when receiving a first level signal through respective control terminals, the first switch module outputs a second data signal received through a first terminal thereof to the first node, and the second switch module outputs an initialization signal received through the first terminal thereof to a second node and a third node; the second data signal is the sum of the level of the first data signal and the threshold voltage of the second transistor of the driving module.
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