CN111210773A - Pixel circuit, driving method thereof and display device - Google Patents
Pixel circuit, driving method thereof and display device Download PDFInfo
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- CN111210773A CN111210773A CN202010065638.9A CN202010065638A CN111210773A CN 111210773 A CN111210773 A CN 111210773A CN 202010065638 A CN202010065638 A CN 202010065638A CN 111210773 A CN111210773 A CN 111210773A
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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
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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
- 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
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Abstract
本申请公开了一种像素电路及其驱动方法、显示装置，像素电路包括写入子电路、初始化子电路、发光控制子电路和驱动子电路，写入子电路在第一扫描信号端的控制下，向第一节点提供数据输入端的信号，数据输入端的信号包括参考电压信号和数据电压信号；初始化子电路在第二扫描信号端的控制下向第二节点提供初始化信号端的信号；发光控制子电路在发光控制信号端的控制下向第二节点提供第一电源电压端的信号；驱动子电路在第一节点的控制下对第三节点进行初始化及电压补偿，并产生驱动发光元件发光的驱动电流。本申请消除了发光元件上次发光后残余的正电荷，实现了对液晶显示器中薄膜晶体管栅极电压的补偿，提高了显示图像的均匀性。
The present application discloses a pixel circuit, a driving method thereof, and a display device. The pixel circuit includes a writing sub-circuit, an initialization sub-circuit, a light-emitting control sub-circuit and a driving sub-circuit. The writing sub-circuit is controlled by a first scanning signal terminal, The signal of the data input terminal is provided to the first node, and the signal of the data input terminal includes a reference voltage signal and a data voltage signal; the initialization sub-circuit provides the signal of the initialization signal terminal to the second node under the control of the second scanning signal terminal; the light-emitting control sub-circuit is emitting light. Under the control of the control signal terminal, the signal of the first power supply voltage terminal is provided to the second node; the driving sub-circuit initializes and voltage compensates the third node under the control of the first node, and generates a driving current for driving the light-emitting element to emit light. The present application eliminates the residual positive charge after the light-emitting element emits light last time, realizes the compensation for the gate voltage of the thin film transistor in the liquid crystal display, and improves the uniformity of the displayed image.
Description
Technical Field
The present disclosure relates to but not limited to the field of display technologies, and in particular, to a pixel circuit, a driving method thereof, and a display device.
Background
In recent years, the AMOLED industry has been rapidly developed at home and abroad due to the excellent display effect of an Active Matrix Organic Light Emitting Diode (AMOLED) display.
The AMOLED can emit Light by a Thin Film Transistor (TFT) generating a driving current in a saturation state and driving an Organic Light Emitting Diode (OLED) to emit Light, where the luminance of the OLED is proportional to the magnitude of the driving current provided to the OLED device, so that a large driving current is required to achieve an optimal display effect, and the low temperature polysilicon can provide a high electron mobility, so that the TFT is made by selecting the low temperature polysilicon in the AMOLED display technology.
In the most basic 2T1C pixel circuit, the magnitude of the OLED driving current is related to the threshold voltage Vth of the driving TFT, but the low-temperature polysilicon process is not mature, and even with the same process parameters, the Vth of the manufactured driving TFT is greatly different, so that the Vth of the driving TFT at different positions of the array substrate is different, and further, the magnitude of the OLED driving current is different, the luminance at different positions of the array substrate is also different, and the display is not uniform.
Disclosure of Invention
The application provides a pixel circuit, a driving method thereof and a display device, which can improve the uniformity of a displayed image.
The embodiment of the application provides a pixel circuit, including: a writing sub-circuit, an initializing sub-circuit, a light emission controlling sub-circuit, a driving sub-circuit, and a light emitting element, wherein: the write-in sub-circuit is respectively connected with the data input end, the first scanning signal end and the first node, and is used for providing signals of the data input end to the first node under the control of the first scanning signal end, wherein the signals of the data input end comprise a reference voltage signal and a data voltage signal; the initialization sub-circuit is respectively connected with the initialization signal end, the second scanning signal end and the second node and is used for providing a signal of the initialization signal end for the second node under the control of the second scanning signal end; the light-emitting control sub-circuit is respectively connected with the first power supply voltage end, the light-emitting control signal end and the second node and is used for providing a signal of the first power supply voltage end for the second node under the control of the light-emitting control signal end; the driving sub-circuit is respectively connected with the initialization signal end, the first node, the second node and the third node, and is used for initializing and compensating the third node under the control of the first node and generating a driving current for driving the light-emitting element to emit light.
In some embodiments, the writing sub-circuit, the initializing sub-circuit and the light emission control sub-circuit respectively include one or more first type transistors, the driving sub-circuit includes one or more second type transistors, and the first type transistors and the second type transistors have different channel types.
In some embodiments, the drive sub-circuit comprises: drive transistor, first electric capacity and second electric capacity, wherein: the control electrode of the driving transistor is connected with the first node, the first electrode of the driving transistor is connected with the second node, and the second electrode of the driving transistor is connected with the third node; one end of the first capacitor is connected with the first node, and the other end of the first capacitor is connected with the third node; one end of the second capacitor is connected with the initialization signal end, and the other end of the second capacitor is connected with the third node.
In some embodiments, the write subcircuit includes: a first transistor, wherein: a control electrode of the first transistor is connected to the first scan signal terminal, a first electrode of the first transistor is connected to the data input terminal, and a second electrode of the first transistor is connected to the first node.
In some embodiments, the initialization sub-circuit comprises: a second transistor, wherein: the control electrode of the second transistor is connected with the second scanning signal end, the first electrode of the second transistor is connected with the initialization signal end, and the second electrode of the second transistor is connected with the second node.
In some embodiments, the lighting control sub-circuit comprises: a third transistor, wherein: a control electrode of the third transistor is connected to the light emission control signal terminal, a first electrode of the third transistor is connected to the first power supply voltage terminal, and a second electrode of the third transistor is connected to the second node.
In some embodiments, the write subcircuit includes: a first transistor, the initialization sub-circuit comprising: a second transistor, the light emission control sub-circuit including: a third transistor, the driving sub-circuit including: drive transistor, first electric capacity and second electric capacity, wherein: a control electrode of the first transistor is connected with the first scanning signal end, a first electrode of the first transistor is connected with the data input end, and a second electrode of the first transistor is connected with the first node; a control electrode of the second transistor is connected with the second scanning signal end, a first electrode of the second transistor is connected with the initialization signal end, and a second electrode of the second transistor is connected with the second node; a control electrode of the third transistor is connected to the light emission control signal terminal, a first electrode of the third transistor is connected to the first power supply voltage terminal, and a second electrode of the third transistor is connected to the second node; the control electrode of the driving transistor is connected with the first node, the first electrode of the driving transistor is connected with the second node, and the second electrode of the driving transistor is connected with the third node; one end of the first capacitor is connected with the first node, and the other end of the first capacitor is connected with the third node; one end of the second capacitor is connected with the initialization signal end, and the other end of the second capacitor is connected with the third node.
In some embodiments, the first transistor, the second transistor, and the third transistor are all P-channel thin film transistors, and the driving transistor is an N-channel thin film transistor.
An embodiment of the present application further provides a display device, including: a pixel circuit as claimed in any one of the above.
An embodiment of the present application further provides a driving method of a pixel circuit, for driving the pixel circuit as described in any one of the above, where the pixel circuit has a plurality of scanning periods, and in one scanning period, the driving method includes: the write-in sub-circuit provides a reference voltage signal to a first node under the control of the first scanning signal terminal; the initialization sub-circuit provides an initialization signal to the second node under the control of the second scanning signal end; the driving sub-circuit initializes a third node under the control of the first node; the light-emitting control sub-circuit provides a signal of a first power supply voltage end to the second node under the control of the light-emitting control signal end, and the driving sub-circuit performs voltage compensation on the third node under the control of the first node; the data voltage signal is provided for the data input end, the write-in sub-circuit provides the data voltage signal for the first node under the control of the first scanning signal end, and the drive sub-circuit controls the voltage of the third node to jump along with the jump of the voltage of the first node; the light-emitting control sub-circuit provides a signal of a first power supply voltage end to the second node under the control of the light-emitting control signal end, and the driving sub-circuit generates a driving current for driving the light-emitting element to emit light under the control of the first node.
Compared with the prior art, the pixel circuit, the driving method thereof and the display device have the advantages that the driving sub-circuit is used for initializing the third node and compensating the voltage under the control of the first node, so that residual positive charges of the light-emitting element after last light-emitting are eliminated, the gate voltage of the thin film transistor in the liquid crystal display is compensated, the influence of the threshold voltage drift of the driving transistor on the driving current of the light-emitting element is avoided, and the uniformity of displayed images and the display quality of the display panel are improved.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the application. Other advantages of the present application may be realized and attained by the instrumentalities and combinations particularly pointed out in the specification and the drawings.
Drawings
The accompanying drawings are included to provide an understanding of the present disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the examples serve to explain the principles of the disclosure and not to limit the disclosure.
Fig. 1 is a schematic structural diagram of a pixel circuit according to an embodiment of the present disclosure;
fig. 2 is an equivalent circuit diagram of a driving sub-circuit provided in an embodiment of the present application;
FIG. 3 is an equivalent circuit diagram of a write sub-circuit according to an embodiment of the present disclosure;
FIG. 4 is an equivalent circuit diagram of an initialization sub-circuit provided in an embodiment of the present application;
fig. 5 is an equivalent circuit diagram of a light emission control sub-circuit provided in an embodiment of the present application;
fig. 6 is an equivalent circuit diagram of a pixel circuit according to an embodiment of the present application;
FIG. 7 is a top view of a sub-pixel in a display substrate according to an embodiment of the present disclosure;
fig. 8 is a timing diagram illustrating an operation of a pixel circuit according to an embodiment of the present disclosure;
FIG. 9 is a signal flow diagram of the pixel circuit provided in the embodiment of FIG. 6 at stage T1;
FIG. 10 is a signal flow diagram of the pixel circuit provided in the embodiment of FIG. 6 at stage T2;
FIG. 11 is a signal flow diagram of the pixel circuit provided in the embodiment of FIG. 6 at stage T3;
FIG. 12 is a signal flow diagram of the pixel circuit provided in the embodiment of FIG. 6 at stage T4;
fig. 13 is a flowchart of a driving method of a pixel circuit according to an embodiment of the present disclosure.
Description of reference numerals:
Data-Data input; INT-initial signal input;
VDD — the first supply voltage terminal; VSS — second supply voltage terminal;
vref — reference voltage; vdata-data voltage;
N1-N3-nodes; C1-C2-capacitance; (ii) a
M1-M3, Md-transistor.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.
Unless otherwise defined, technical or scientific terms used in the disclosure of the embodiments of the present application should have the ordinary meaning as understood by those having ordinary skill in the art to which the present invention belongs. The use of "first," "second," and similar terms in the embodiments of the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that a particular element or item appears in front of the word or is detected by mistake, and that the word or item appears after the word or item and its equivalents, but does not exclude other elements or misdetections.
It will be appreciated by those skilled in the art that the transistors employed in all embodiments of the present application may be thin film transistors or field effect transistors or other devices having the same characteristics. Preferably, the thin film transistor used in the embodiment of the present application may be an oxide semiconductor transistor. Since the source and drain of the transistor used herein are symmetrical, the source and drain may be interchanged. In the embodiment of the present application, in order to distinguish two electrodes of a transistor except for a gate, one of the electrodes is referred to as a first electrode, the other electrode is referred to as a second electrode, the first electrode may be a source or a drain, and the second electrode may be a drain or a source.
Fig. 1 is a schematic structural diagram of a pixel circuit provided in an embodiment of the present application, and as shown in fig. 1, the pixel circuit provided in the embodiment of the present application includes: a writing sub-circuit, an initializing sub-circuit, a light emission controlling sub-circuit, a driving sub-circuit, and a light emitting element.
Specifically, the write-in sub-circuit is respectively connected to the Data input terminal Data, the first scan signal terminal S1 and the first node N1, and is configured to provide a signal of the Data input terminal Data to the first node N1 under the control of the first scan signal terminal S1, where the signal of the Data input terminal Data includes a reference voltage signal Vref and a Data voltage signal Vdata; the initialization sub-circuit is respectively connected with the initialization signal terminal INT, the second scan signal terminal S2 and the second node N2, and is configured to provide a signal of the initialization signal terminal INT to the second node N2 under the control of the second scan signal terminal S2; the light emitting control sub-circuit is respectively connected with the first power voltage terminal VDD, the light emitting control signal terminal S3 and the second node N2, and is configured to provide a signal of the first power voltage terminal VDD to the second node N2 under the control of the light emitting control signal terminal S3; the driving sub-circuit is respectively connected to the initialization signal terminal INT, the first node N1, the second node N2 and the third node N3, and is configured to perform initialization and voltage compensation on the third node N3 under the control of the first node N1, and generate a driving current for driving the light emitting element to emit light.
The pixel circuit provided by the embodiment of the application initializes and compensates the voltage of the third node N3 under the control of the first node N1, eliminates the residual positive charge of the light-emitting element after last light-emitting, realizes the compensation of the gate voltage of the thin film transistor in the liquid crystal display, avoids the influence of the threshold voltage drift of the driving transistor on the driving current of the light-emitting element, and improves the uniformity of the displayed image and the display quality of the display panel.
In one exemplary embodiment, the writing sub-circuit, the initializing sub-circuit, and the light emission controlling sub-circuit respectively include one or more first type transistors, the driving sub-circuit includes one or more second type transistors, and the first type transistors and the second type transistors are different in channel type.
Illustratively, the first type transistor may be a P-type thin film transistor, and the second type transistor may be an N-type thin film transistor; alternatively, the first type transistor may be an N-type thin film transistor, and the second type transistor may be a P-type thin film transistor.
In an exemplary embodiment, fig. 2 is an equivalent circuit diagram of a driving sub-circuit provided in an embodiment of the present application, and as shown in fig. 2, the driving sub-circuit provided in the embodiment of the present application includes: a drive transistor Md, a first capacitor C1 and a second capacitor C2.
Specifically, the control electrode of the driving transistor Md is connected to the first node N1, the first electrode of the driving transistor Md is connected to the second node N2, and the second electrode of the driving transistor Md is connected to the third node N3; one end of the first capacitor C1 is connected to the first node N1, and the other end of the first capacitor C1 is connected to the third node N3; one end of the second capacitor C2 is connected to the initialization signal terminal INT, and the other end of the second capacitor C2 is connected to the third node N3.
One exemplary structure of the drive sub-circuit is specifically shown in fig. 2. It is easily understood by those skilled in the art that the implementation of the driving sub-circuits is not limited thereto as long as their respective functions can be realized.
In an exemplary embodiment, fig. 3 is an equivalent circuit diagram of a write sub-circuit provided in an embodiment of the present application, and as shown in fig. 3, the write sub-circuit provided in the embodiment of the present application includes: the first transistor M1.
Specifically, a control electrode of the first transistor M1 is connected to the first scan signal terminal S1, a first electrode of the first transistor M1 is connected to the Data input terminal Data, and a second electrode of the first transistor M1 is connected to the first node N1.
One exemplary structure of the write subcircuit is specifically shown in fig. 3. It is easily understood by those skilled in the art that the implementation of the write sub-circuit is not limited thereto as long as its respective functions can be realized.
In an exemplary embodiment, fig. 4 is an equivalent circuit diagram of an initialization sub-circuit provided in an embodiment of the present application, and as shown in fig. 4, the initialization sub-circuit provided in the embodiment of the present application includes: and a second transistor M2.
Specifically, a control electrode of the second transistor M2 is connected to the second scan signal terminal S2, a first electrode of the second transistor M2 is connected to the initialization signal terminal INT, and a second electrode of the second transistor M2 is connected to the second node N2.
One exemplary structure of the initialization sub-circuit is specifically shown in fig. 4. Those skilled in the art will readily appreciate that the implementation of the initialization sub-circuits is not so limited, so long as their respective functions are achieved.
In an exemplary embodiment, fig. 5 is an equivalent circuit diagram of a light emission control sub-circuit provided in an embodiment of the present application, and as shown in fig. 5, the light emission control sub-circuit provided in the embodiment of the present application includes: and a third transistor M3.
Specifically, a control electrode of the third transistor M3 is connected to the light emission control signal terminal S3, a first electrode of the third transistor M3 is connected to the first power voltage terminal VDD, and a second electrode of the third transistor M3 is connected to the second node N2.
One exemplary structure of the emission control sub-circuit is specifically shown in fig. 5. It is easily understood by those skilled in the art that the implementation of the light emission control sub-circuit is not limited thereto as long as its respective functions can be realized.
Fig. 6 is an equivalent circuit diagram of a pixel circuit according to an embodiment of the present application, and as shown in fig. 6, a driving sub-circuit in the pixel circuit according to the embodiment of the present application includes: a driving transistor Md, a first capacitor C1 and a second capacitor C2, the write sub-circuit comprising: the first transistor M1, the initialization sub-circuit, comprises: the second transistor M2, the light emission control sub-circuit includes: and a third transistor M3.
Specifically, the control electrode of the driving transistor Md is connected to the first node N1, the first electrode of the driving transistor Md is connected to the second node N2, and the second electrode of the driving transistor Md is connected to the third node N3; one end of the first capacitor C1 is connected to the first node N1, and the other end of the first capacitor C1 is connected to the third node N3; one end of the second capacitor C2 is connected to the initialization signal terminal INT, and the other end of the second capacitor C2 is connected to the third node N3; a control electrode of the first transistor M1 is connected to the first scan signal terminal S1, a first electrode of the first transistor M1 is connected to the Data input terminal Data, and a second electrode of the first transistor M1 is connected to the first node N1; a control electrode of the second transistor M2 is connected to the second scan signal terminal S2, a first electrode of the second transistor M2 is connected to the initialization signal terminal INT, and a second electrode of the second transistor M2 is connected to the second node N2; a control electrode of the third transistor M3 is connected to the light emission control signal terminal S3, a first electrode of the third transistor M3 is connected to the first power voltage terminal VDD, and a second electrode of the third transistor M3 is connected to the second node N2; the anode of the light emitting element L is connected to the third node N3, and the cathode of the light emitting element L is connected to the second power voltage terminal VSS.
Exemplary structures of the driving sub-circuit, the writing sub-circuit, the initializing sub-circuit, and the light emission controlling sub-circuit are specifically shown in fig. 8. Those skilled in the art will readily appreciate that the implementation of each of the above sub-circuits is not limited thereto as long as their respective functions can be achieved.
In an exemplary embodiment, the light emitting element L may be an Organic Light Emitting Diode (OLED).
In an exemplary embodiment, the first transistor M1, the second transistor M2, and the third transistor M3 are all P-channel thin film transistors, and the driving transistor Md is an N-channel thin film transistor.
The pixel circuit provided by the embodiment greatly reduces the number of thin film transistors and reduces the loss in the circuit; by using the N-channel thin film transistor and the P-channel thin film transistor together, the occupied space of a pixel circuit is effectively reduced, and the resolution of a screen is improved.
In the present embodiment, the active level of the transistor is high for the transistors with different doping types, for example, for the N-type thin film transistor, and the active level is low for the P-type thin film transistor.
In this embodiment, considering that the low-temperature polysilicon thin film transistor has a small leakage current, in the embodiments of the present application, it is preferable that all transistors are low-temperature polysilicon thin film transistors, and the thin film transistors may specifically be selected from thin film transistors with a bottom gate structure or thin film transistors with a top gate structure.
In this embodiment, the first capacitor C1 and the second capacitor C2 may be a liquid crystal capacitor formed by a pixel electrode and a common electrode, or may be an equivalent capacitor formed by a liquid crystal capacitor formed by a pixel electrode and a common electrode and a storage capacitor, which is not limited in this application.
Fig. 7 is a top view of a sub-pixel in a display substrate according to an embodiment of the present disclosure, as shown in fig. 7, the display substrate includes: the semiconductor device comprises a substrate, and a semiconductor layer, a first metal layer, a second metal layer, a third metal layer and a fourth metal layer which are arranged on the substrate and are insulated from each other.
In this embodiment, the semiconductor layer includes: a plurality of active layers of transistors, the first metal layer including a light shielding layer of the driving transistor Md, a first electrode of the first capacitor C1, and a first electrode of the second capacitor C2, the second metal layer including a plurality of gate lines and gate electrodes of the plurality of transistors; the third metal layer includes a second electrode of the first capacitor C1, a second electrode of the second capacitor C2, and the fourth metal layer includes source and drain electrodes of a plurality of transistors, an initial signal line, a data line, and a power line.
Taking the pixel circuit provided in the embodiment of the present application that the switching transistors M1-M3 are all P-type thin film transistors, and the driving transistor Md is an N-type thin film transistor as an example, the operation process of a pixel circuit unit in a frame period is specifically described with reference to the pixel circuit unit shown in fig. 6 and the operation timing diagram shown in fig. 8. As shown in fig. 6, the pixel circuit provided in the embodiment of the present application includes 4 transistor units (M1 to M3, Md), 2 capacitor units (C1, C2), and 4 power supply terminals (VDD, VSS, Data, and INT), wherein the first power supply voltage terminal VDD continuously supplies a high-level signal, and the second power supply voltage terminal VSS continuously supplies a low-level signal. The working process comprises the following steps:
in the first phase T1, the first scan signal S1 and the second scan signal S2 are both at low level, the emission control signal S3 is at high level, the reference voltage Vref is input to the Data input terminal Data, and the negative signal Vsus is input to the initial signal terminal INT. As shown in fig. 9, the first transistor M1 is turned on under the control of the first scan signal S1, the second transistor M2 is turned on under the control of the second scan signal S2, and the third transistor M3 is turned off under the control of the light emission control signal S3. The reference voltage Vref provided by the Data input terminal Data is applied to the gate of the driving transistor Md and one end of the first capacitor C1 through the first transistor M1, so that the driving transistor Md is turned on. At this time, for the driving transistor Md, the negative signal Vsus provided by the initial signal terminal INT is applied to one terminal of the second capacitor C2 and is applied to the first pole of the driving transistor Md through the second transistor M2, and the voltage of the first pole of the driving transistor Md is Vsus at this time. In this embodiment, the first pole of the driving transistor Md is the drain, and the second pole of the driving transistor Md is the source. Thus, the negative signal Vsus provided from the initialization signal terminal INT is applied to the second electrode of the driving transistor Md through the driving transistor Md, and the positive charges remaining at the anode electrode after the last light emission of the light emitting element L are eliminated.
In the second stage T2, the first scan signal S1 and the emission control signal S3 are both at a low level, the second scan signal S2 is at a high level, and the Data input terminal Data maintains the input reference voltage Vref, so that the driving transistor Md is maintained in a conductive state. As shown in fig. 10, the first transistor M1 maintains an on state under the control of the first scan signal S1, the second transistor M2 is turned off under the control of the second scan signal S2, and the third transistor M3 is turned on under the control of the light emission control signal S3. When the second pole voltage of the driving transistor Md rises to Vref-Vth, the driving transistor Md is turned off. In this embodiment, a weak current flows through the light emitting element L before the second-pole voltage of the driving transistor Md rises to Vref-Vth, but the current is not enough to make the light emitting element L emit light.
In the third stage T3, the first scan signal S1 is at a low level, the second scan signal S2 and the emission control signal S3 are both at a high level, and the Data voltage Vdata is input to the Data input terminal Data. As shown in fig. 11, the first transistor M1 maintains an on state under the control of the first scan signal S1, the second transistor M2 is turned off under the control of the second scan signal S2, and the third transistor M3 is turned off under the control of the light emission control signal S3.
The gate voltage of the drive transistor Md jumps from Vref to Vdata, i.e., the amount △ of the gate voltage jump of the drive transistor Md is Vdata-Vref, and correspondingly, of the drive transistor MdThe voltage of the second pole also jumps. Since the first capacitor C1 and the second capacitor C2 are connected in series, the jump amount of the voltage of the second pole of the driving transistor Md is based on the principle of series circuit capacitance voltage division
The voltage of the second pole of the driving transistor Md is
In the fourth stage T4, the first and second scan signals S1 and S2 are at a high level, and the emission control signal S3 is at a low level. As shown in fig. 12, the third transistor M3 is turned on under the control of the light emission control signal S3, the first transistor M1 is turned off under the control of the first scan signal S1, and the second transistor M2 is turned off under the control of the second scan signal S2. The second pole voltage of the driving transistor Md is Voled, and the gate voltage of the driving transistor is:
at this time, the gate-source voltage of the drive transistor Md
Since the gate-source voltage VGS of the driving transistor Md is greater than Vth, the driving transistor Md is turned on. At this time, the third transistor M3, the driving transistor Md, and the light emitting element L are in one serial path, and the light emitting element L starts emitting light. The current flowing through the light emitting element L is:
where μ is the carrier mobility of the drive transistor Md, Cox is the capacitance of the drive transistor Md, W is the channel width of the drive transistor Md, L is the channel length of the drive transistor Md, and VGS is the voltage difference between the gate and source of the drive transistor Md.
As can be seen from the above formula, the current Ids flowing through the light emitting element L is independent of the threshold voltage Vth of the driving switching tube Md and independent of the first power supply voltage VDD and the second power supply voltage VSS, and therefore, the influence of the threshold voltage Vth of the driving transistor Md on the current flowing through the light emitting element L and the influence of the first power supply voltage VDD and the second power supply voltage VSS on the current flowing through the light emitting element can be eliminated, and uniformity and uniform display of luminance can be ensured.
Based on the working time sequence, the pixel circuit realizes the compensation of the grid voltage of the thin film transistor in the liquid crystal display, and improves the stability of the pixel circuit and the display quality of the display panel.
Based on the same inventive concept, some embodiments of the present invention further provide a driving method of a pixel circuit, which is applied to the pixel circuit provided in the foregoing embodiments, and the pixel circuit includes: fig. 13 is a flowchart of a driving method of a pixel circuit according to an embodiment of the present disclosure, and as shown in fig. 13, the driving method specifically includes the following steps:
In this step, the third node is initialized under the control of the first node by the driving sub-circuit, and the residual positive charges of the anode after the last light emission of the light emitting element are eliminated.
In the step, a reference voltage signal is provided for the data input end, so that the first node keeps the reference voltage Vref of the previous stage unchanged, the second node writes in the voltage VDD of the first power voltage end, and when the third node is charged to Vref-Vth, the driving transistor is turned off, thereby realizing the compensation of the threshold voltage of the driving transistor and further improving the uniformity of the displayed image.
In this step, the voltage step variable △ of the first node is Vdata-Vref, Vdata is a data voltage, and the voltage step variable of the third node is
In step 400, the light-emitting control sub-circuit provides a signal of the first power voltage terminal to the second node under the control of the light-emitting control signal terminal, and the driving sub-circuit generates a driving current for driving the light-emitting element to emit light under the control of the first node.
In this step, the driving current generated is:
where μ is the carrier mobility of the drive transistor Md, Cox is the capacitance of the drive transistor Md, W is the channel width of the drive transistor Md, L is the channel length of the drive transistor Md, and VGS is the voltage difference between the gate and source of the drive transistor Md.
The driving method of the pixel circuit provided by the embodiment eliminates the residual positive charges of the light emitting element after the light emitting element emits light last time, realizes the compensation of the gate voltage of the thin film transistor in the liquid crystal display, eliminates the influence of the first power voltage and the second power voltage on the current flowing through the light emitting element, and improves the uniformity of the displayed image and the display quality of the display panel.
Based on the same inventive concept, embodiments of the present application further provide a display device, which includes the pixel circuit provided in the above embodiments.
The following points need to be explained:
the drawings of the embodiments of the present application relate only to the structures related to the embodiments of the present application, and other structures may refer to general designs.
Without conflict, features of embodiments of the present invention, that is, embodiments, may be combined with each other to arrive at new embodiments.
Although the embodiments of the present invention have been described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A pixel circuit, comprising: a writing sub-circuit, an initializing sub-circuit, a light emission controlling sub-circuit, a driving sub-circuit, and a light emitting element, wherein:
the write-in sub-circuit is respectively connected with the data input end, the first scanning signal end and the first node, and is used for providing signals of the data input end to the first node under the control of the first scanning signal end, wherein the signals of the data input end comprise a reference voltage signal and a data voltage signal;
the initialization sub-circuit is respectively connected with the initialization signal end, the second scanning signal end and the second node and is used for providing a signal of the initialization signal end for the second node under the control of the second scanning signal end;
the light-emitting control sub-circuit is respectively connected with the first power supply voltage end, the light-emitting control signal end and the second node and is used for providing a signal of the first power supply voltage end for the second node under the control of the light-emitting control signal end;
the driving sub-circuit is respectively connected with the initialization signal end, the first node, the second node and the third node, and is used for initializing and compensating the third node under the control of the first node and generating a driving current for driving the light-emitting element to emit light.
2. The pixel circuit according to claim 1, wherein the writing sub-circuit, the initializing sub-circuit, and the light emission control sub-circuit respectively comprise one or more transistors of a first type, the driving sub-circuit comprises one or more transistors of a second type, and the transistors of the first type and the second type have different channel types.
3. The pixel circuit of claim 1, wherein the drive sub-circuit comprises: drive transistor, first electric capacity and second electric capacity, wherein:
the control electrode of the driving transistor is connected with the first node, the first electrode of the driving transistor is connected with the second node, and the second electrode of the driving transistor is connected with the third node;
one end of the first capacitor is connected with the first node, and the other end of the first capacitor is connected with the third node;
one end of the second capacitor is connected with the initialization signal end, and the other end of the second capacitor is connected with the third node.
4. The pixel circuit of claim 1, wherein the write sub-circuit comprises: a first transistor, wherein: a control electrode of the first transistor is connected to the first scan signal terminal, a first electrode of the first transistor is connected to the data input terminal, and a second electrode of the first transistor is connected to the first node.
5. The pixel circuit of claim 1, wherein the initialization sub-circuit comprises: a second transistor, wherein: the control electrode of the second transistor is connected with the second scanning signal end, the first electrode of the second transistor is connected with the initialization signal end, and the second electrode of the second transistor is connected with the second node.
6. The pixel circuit of claim 1, wherein the light emission control sub-circuit comprises: a third transistor, wherein: a control electrode of the third transistor is connected to the light emission control signal terminal, a first electrode of the third transistor is connected to the first power supply voltage terminal, and a second electrode of the third transistor is connected to the second node.
7. The pixel circuit of claim 1, wherein the drive sub-circuit comprises: a drive transistor, a first capacitance, and a second capacitance, the write sub-circuit comprising: a first transistor, the initialization sub-circuit comprising: a second transistor, the light emission control sub-circuit including: a third transistor, wherein:
the control electrode of the driving transistor is connected with the first node, the first electrode of the driving transistor is connected with the second node, and the second electrode of the driving transistor is connected with the third node;
one end of the first capacitor is connected with the first node, and the other end of the first capacitor is connected with the third node;
one end of the second capacitor is connected with the initialization signal end, and the other end of the second capacitor is connected with the third node;
a control electrode of the first transistor is connected with the first scanning signal end, a first electrode of the first transistor is connected with the data input end, and a second electrode of the first transistor is connected with the first node;
a control electrode of the second transistor is connected with the second scanning signal end, a first electrode of the second transistor is connected with the initialization signal end, and a second electrode of the second transistor is connected with the second node;
a control electrode of the third transistor is connected to the light emission control signal terminal, a first electrode of the third transistor is connected to the first power supply voltage terminal, and a second electrode of the third transistor is connected to the second node.
8. The pixel circuit according to claim 7, wherein the first transistor, the second transistor, and the third transistor are each a P-channel thin film transistor, and wherein the driving transistor is an N-channel thin film transistor.
9. A display device, comprising: a pixel circuit as claimed in any one of claims 1-8.
10. A driving method for driving the pixel circuit according to any one of claims 1 to 8, the pixel circuit having a plurality of scanning periods, the driving method comprising, during one scanning period:
the write-in sub-circuit provides a reference voltage signal to a first node under the control of the first scanning signal terminal; the initialization sub-circuit provides an initialization signal to the second node under the control of the second scanning signal end; the driving sub-circuit initializes a third node under the control of the first node;
the light-emitting control sub-circuit provides a signal of a first power supply voltage end to the second node under the control of the light-emitting control signal end, and the driving sub-circuit performs voltage compensation on the third node under the control of the first node;
the data voltage signal is provided for the data input end, the write-in sub-circuit provides the data voltage signal for the first node under the control of the first scanning signal end, and the drive sub-circuit controls the voltage of the third node to jump along with the jump of the voltage of the first node;
the light-emitting control sub-circuit provides a signal of a first power supply voltage end to the second node under the control of the light-emitting control signal end, and the driving sub-circuit generates a driving current for driving the light-emitting element to emit light under the control of the first node.
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Application publication date: 20200529 |