CN110544458B - Pixel circuit, driving method thereof and display device - Google Patents

Pixel circuit, driving method thereof and display device Download PDF

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CN110544458B
CN110544458B CN201910852504.9A CN201910852504A CN110544458B CN 110544458 B CN110544458 B CN 110544458B CN 201910852504 A CN201910852504 A CN 201910852504A CN 110544458 B CN110544458 B CN 110544458B
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transistor
driving transistor
pole
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voltage
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CN110544458A (en
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徐映嵩
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BOE Technology Group Co Ltd
Chengdu BOE Optoelectronics Technology Co Ltd
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BOE Technology Group Co Ltd
Chengdu BOE Optoelectronics 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]
    • 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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  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
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  • Control Of El Displays (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)

Abstract

The invention discloses a pixel circuit, a driving method thereof and a display device, wherein the pixel circuit comprises a driving transistor, a data writing module, a light-emitting control module, a threshold compensation module and a light-emitting device; the data writing module provides a signal of the data signal end to the second pole of the driving transistor; the threshold compensation module resets the grid of the driving transistor and compensates the threshold voltage of the driving transistor; the light-emitting control module provides a signal of a first voltage end to a first pole of the driving transistor and conducts a second pole of the driving transistor with the light-emitting device; the driving transistor is used for generating a driving current and driving the light-emitting device to emit light. The pixel circuit provided by the embodiment of the invention can compensate the threshold voltage of the driving transistor, so that the driving current for driving the light-emitting device to emit light is not influenced by the threshold voltage of the driving module. And, the voltage of the first voltage terminal may be compensated so that the driving current is not affected by the voltage of the first voltage terminal.

Description

Pixel circuit, driving method thereof and display device
Technical Field
The invention relates to the technical field of display, in particular to a pixel circuit, a driving method thereof and a display device.
Background
Organic Light Emitting Diode (OLED) panels have been widely paid attention to, and have been flexible, high in contrast, low in power consumption, and the like. The pixel circuit is the core technical content of the OLED panel, and has important research significance. Generally, the OLED in the OLED panel is driven to emit light by a current generated by a driving transistor in a pixel circuit. However, due to the limitation of the process and the increase of the use time, the threshold voltage Vth of the driving transistor may shift to different degrees, so that the OLED panel has a problem of non-uniform OLED light emission brightness. Moreover, the presence of IR Drop in the OLED panel also causes the OLED panel to generate a problem of non-uniform OLED light emission brightness.
Disclosure of Invention
The embodiment of the invention provides a pixel circuit, a driving method thereof and a display device, which are used for improving the display effect.
Accordingly, an embodiment of the present invention provides a pixel circuit, including: the device comprises a driving transistor, a data writing module, a light emitting control module, a threshold compensation module and a light emitting device;
the data writing module is configured to provide a signal of a data signal terminal to the second pole of the driving transistor in response to a signal of a scan signal terminal;
the threshold compensation module is configured to reset the gate of the driving transistor and compensate for a threshold voltage of the driving transistor in response to a signal of a reset signal terminal;
the light emitting control module is configured to provide a signal of a first voltage terminal to a first pole of the driving transistor and to conduct a second pole of the driving transistor with the light emitting device in response to a signal of a light emitting control terminal;
the driving transistor is configured to generate a driving current according to a gate voltage and a second pole voltage of the driving transistor to drive the light emitting device to emit light by the driving current.
Optionally, in this embodiment of the present invention, the threshold compensation module includes a first sub-module, a second sub-module, and a third sub-module;
the first sub-module is configured to store a voltage of a gate of the driving transistor and a second pole of the driving transistor;
the second sub-module is configured to conduct the first pole of the driving transistor and the gate of the driving transistor in response to a signal of the reset signal terminal;
the third sub-module is configured to store a voltage of the first voltage terminal and a gate of the driving transistor.
Optionally, in an embodiment of the present invention, the first sub-module includes a first capacitor, a first terminal of the first capacitor is coupled to the second pole of the driving transistor, and a second terminal of the first capacitor is coupled to the gate of the driving transistor; and/or the presence of a gas in the gas,
the third sub-module includes: and one end of the second capacitor is coupled with the first voltage end, and the second end of the second capacitor is coupled with the grid electrode of the driving transistor.
Optionally, in an embodiment of the present invention, the threshold compensation module further includes a fourth sub-module, wherein the gate of the driving transistor is coupled to the second end of the second capacitor through the fourth sub-module;
the fourth sub-module is configured to turn on the gate of the driving transistor and the second terminal of the second capacitor in response to a signal of the scan signal terminal.
Optionally, in an embodiment of the present invention, the fourth sub-module includes a fifth transistor, a gate of the fifth transistor is coupled to the scan signal terminal, a first pole of the fifth transistor is coupled to the second terminal of the second capacitor, and a second pole of the fifth transistor is coupled to the gate of the driving transistor.
Optionally, in an embodiment of the present invention, the second sub-module includes a first transistor, a gate of the first transistor is coupled to the reset signal terminal, a first pole of the first transistor is coupled to the first pole of the driving transistor, and a second pole of the first transistor is coupled to the gate of the driving transistor.
Optionally, in an embodiment of the present invention, the data writing module includes a second transistor, a gate of the second transistor is coupled to the scan signal terminal, a first pole of the second transistor is coupled to the data signal terminal, and a second pole of the second transistor is coupled to the second pole of the driving transistor.
Optionally, in an embodiment of the present invention, the light emitting control module includes a third transistor and a fourth transistor;
a gate of the third transistor is coupled to the light emitting control terminal, a first pole of the third transistor is coupled to the second pole of the driving transistor, and the second pole of the third transistor is coupled to the first pole of the light emitting device;
a gate of the fourth transistor is coupled to the light emission control terminal, a first pole of the fourth transistor is coupled to the first voltage terminal, and a second pole of the fourth transistor is coupled to the first pole of the driving transistor.
Correspondingly, an embodiment of the present invention further provides a display device provided in an embodiment of the present invention, where the display device includes the pixel circuit.
Correspondingly, an embodiment of the present invention further provides a driving method of the pixel circuit provided in the embodiment of the present invention, including:
the data writing module responds to the signal of the scanning signal end and provides the signal of the data signal end to the second pole of the driving transistor in the initialization stage; the threshold compensation module responds to a signal of the reset signal end to reset the grid electrode of the driving transistor; the light-emitting control module responds to a signal of the light-emitting control terminal, provides a signal of the first voltage terminal to a first pole of the driving transistor, and conducts a second pole of the driving transistor and the light-emitting device;
a threshold compensation stage, wherein the data writing module responds to the signal of the scanning signal end and provides the signal of the data signal end to the second pole of the driving transistor; the threshold compensation module compensates the threshold voltage of the driving transistor;
a data writing stage, wherein the data writing module responds to the signal of the scanning signal end and provides the signal of the data signal end to the second pole of the driving transistor;
a light emitting stage, wherein the light emitting control module responds to a signal of the light emitting control terminal, provides a signal of the first voltage terminal to a first pole of the driving transistor, and conducts a second pole of the driving transistor with the light emitting device; the driving transistor generates a driving current according to a gate voltage and a second pole voltage of the driving transistor to drive the light emitting device to emit light by the driving current.
The invention has the following beneficial effects:
the pixel circuit, the driving method thereof and the display device provided by the embodiment of the invention comprise a driving transistor, a data writing module, a light emitting control module, a threshold compensation module and a light emitting device; the data writing module is configured to provide a signal of the data signal terminal to the second pole of the driving transistor in response to a signal of the scan signal terminal; the threshold compensation module is configured to reset the gate of the driving transistor and compensate for a threshold voltage of the driving transistor in response to a signal of the reset signal terminal; the light emitting control module is configured to provide a signal of a first voltage terminal to a first pole of the driving transistor and to conduct a second pole of the driving transistor with the light emitting device in response to a signal of the light emitting control terminal; the driving transistor is configured to generate a driving current according to a gate voltage and a second diode voltage of the driving transistor to drive the light emitting device to emit light by the driving current. Therefore, the pixel circuit provided by the embodiment of the invention can compensate the threshold voltage of the driving transistor through the mutual matching of the module and the element, so that the driving current for driving the light-emitting device to emit light is not influenced by the threshold voltage of the driving module, and the problem of uneven light-emitting brightness caused by uneven threshold voltage is solved. In addition, the voltage of the first voltage end can be compensated through the mutual matching of the module and the element, so that the driving current is not influenced by the voltage of the first voltage end, and the problem of uneven light emitting brightness caused by the IR Drop of the first voltage end can be solved.
Drawings
Fig. 1 is a schematic structural diagram of a pixel circuit according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of another pixel circuit according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of another pixel circuit according to an embodiment of the present invention;
FIG. 4 is a signal timing diagram of the pixel circuit shown in FIG. 3;
fig. 5 is a schematic structural diagram of another pixel circuit according to an embodiment of the present invention;
FIG. 6 is a timing diagram of signals in the pixel circuit shown in FIG. 5;
fig. 7 is a flowchart of a driving method of a pixel circuit according to an embodiment of the invention;
fig. 8 is a schematic structural diagram of a display device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, specific embodiments of a pixel circuit, a driving method thereof and a display device according to an embodiment of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the preferred embodiments described below are only for illustrating and explaining the present invention and are not to be used for limiting the present invention. And the embodiments and features of the embodiments may be combined with each other without conflict.
An embodiment of the present invention provides a pixel circuit, as shown in fig. 1, including a driving transistor M0, a data writing module 101, a light emitting control module 102, a threshold compensation module 103, and a light emitting device 104; the Data writing module 101 is configured to supply a signal of the Data signal terminal Data to the second pole of the driving transistor in response to a signal of the scan signal terminal Gate; the threshold compensation module 103 is configured to Reset the gate of the driving transistor M0 and compensate for the threshold voltage of the driving transistor M0 in response to a signal of the Reset signal terminal Reset; the light emission control module 102 is configured to provide a signal of a first voltage terminal VDD to a first pole of the driving transistor M0 and to turn on a second pole of the driving transistor M0 with the light emitting device 104 in response to a signal of the light emission control terminal EM; the driving transistor M0 is configured to generate a driving current according to the gate voltage and the second pole voltage of the driving transistor M0 to drive the light emitting device 104 to emit light by the driving current.
The pixel circuit provided by the embodiment of the invention comprises a driving transistor, a data writing module, a light-emitting control module, a threshold compensation module and a light-emitting device; the data writing module is configured to provide a signal of the data signal terminal to the second pole of the driving transistor in response to a signal of the scan signal terminal; the threshold compensation module is configured to reset the gate of the driving transistor and compensate for a threshold voltage of the driving transistor in response to a signal of the reset signal terminal; the light emitting control module is configured to provide a signal of a first voltage terminal to a first pole of the driving transistor and to conduct a second pole of the driving transistor with the light emitting device in response to a signal of the light emitting control terminal; the driving transistor is configured to generate a driving current according to a gate voltage and a second diode voltage of the driving transistor to drive the light emitting device to emit light by the driving current. Therefore, the pixel circuit provided by the embodiment of the invention can compensate the threshold voltage of the driving transistor through the mutual matching of the module and the element, so that the driving current for driving the light-emitting device to emit light is not influenced by the threshold voltage of the driving module, and the problem of uneven light-emitting brightness caused by uneven threshold voltage is solved. In addition, the voltage of the first voltage end can be compensated through the mutual matching of the module and the element, so that the driving current is not influenced by the voltage of the first voltage end, and the problem of uneven light emitting brightness caused by the IR Drop of the first voltage end can be solved.
The present invention will be described in detail with reference to specific examples. It should be noted that the present embodiment is intended to better explain the present invention, but not to limit the present invention.
The first embodiment,
In practical implementation, in the pixel circuit provided in the embodiment of the present invention, as shown in fig. 2, the threshold compensation module 103 includes a first sub-module 1031, a second sub-module 1032 and a third sub-module 1033; the first sub-module 1031 is configured to store the voltage of the gate G of the driving transistor M0 and the second pole D of the driving transistor M0; the second sub-module 1032 is configured to conduct the first pole S of the driving transistor M0 with the gate G of the driving transistor in response to the signal of the Reset signal terminal Reset; the third sub-module 1033 is configured to store the voltage of the first voltage terminal VDD and the gate G of the driving transistor M0.
In specific implementation, in the pixel circuit provided in the embodiment of the invention, as shown in fig. 3, the first sub-module 1031 includes a first capacitor C1, a first terminal of the first capacitor C1 is coupled to the second pole D of the driving transistor M0, and a second terminal of the first capacitor C1 is coupled to the gate G of the driving transistor M0.
In specific implementation, in the pixel circuit provided in the embodiment of the invention, as shown in fig. 3, the second sub-module 1032 includes a first transistor M1, a gate of the first transistor M1 is coupled to the Reset signal terminal Reset, a first pole of the first transistor M1 is coupled to the first pole S of the driving transistor M0, and a second pole of the first transistor M1 is coupled to the gate G of the driving transistor M0.
In practical implementation, in the pixel circuit provided in the embodiment of the present invention, as shown in fig. 3, the third sub-module 1033 includes: one end of the second capacitor C2, one end of the second capacitor C2 are coupled to the first voltage terminal VDD, and a second end of the second capacitor C2 is coupled to the gate G of the driving transistor M0.
In a specific implementation, as shown in fig. 3, the Data writing module 101 includes a second transistor M2, a Gate of the second transistor M2 is coupled to the Gate of the scan signal terminal Gate, a first pole of the second transistor M2 is coupled to the Data signal terminal Data, and a second pole of the second transistor M2 is coupled to the second pole D of the driving transistor M0.
In specific implementation, in the pixel circuit provided in the embodiment of the invention, as shown in fig. 3, the light emission control module 102 includes a third transistor M3 and a fourth transistor M4; a gate of the third transistor M3 is coupled to the light emission control terminal EM, a first pole of the third transistor M3 is coupled to the second pole D of the driving transistor M0, and a second pole of the third transistor M3 is coupled to the first pole of the light emitting device 104; the gate of the fourth transistor M4 is coupled to the emission control EM terminal, the first pole of the fourth transistor M4 is coupled to the first voltage terminal VDD, and the second pole of the fourth transistor M4 is coupled to the first pole S of the driving transistor M0.
In a specific implementation, as shown in fig. 2, in the pixel circuit provided in the embodiment of the invention, a first terminal of the light emitting device 104 is coupled to the light emitting control module 102, and a second terminal of the light emitting device 104 is coupled to the second voltage terminal VSS. Also, in particular implementations, the light emitting device 104 may be: at least one of Organic Light Emitting Diodes (OLED) and Quantum Dot Light Emitting Diodes (QLED). For example, when the light emitting device 104 is an OLED, the anode of the OLED is a first end of the light emitting device 104, and the cathode is a second end of the light emitting device 104.
Generally, when the voltage difference between the two ends of the light emitting device is larger than the turn-on voltage value of the turn-on voltage of the light emitting device, the light emitting device can emit light. In a specific implementation, in the pixel circuit provided in the embodiment of the invention, as shown in fig. 3, the voltage value Vdata of the Data signal terminal Data, the voltage value VSS of the second voltage terminal VSS, and the turn-on voltage value Voled of the light emitting device 104 satisfy the following relation: 2Voled + Vss > Vdata > Voled + Vss.
In a specific implementation, in the pixel circuit provided in the embodiment of the present invention, the transistors are all illustrated as P-type transistors, and the design principle of the pixel circuit is the same as that of the present invention when the transistors are N-type transistors, which also belongs to the protection scope of the present invention.
The specific structure of each circuit in the pixel circuit provided in the embodiment of the present invention is merely illustrated, and in the implementation, the specific structure of each circuit is not limited to the structure provided in the embodiment of the present invention, and may be other structures known to those skilled in the art, and is not limited herein.
Specifically, in the pixel circuit provided in the embodiment of the present invention, each Transistor may be a Thin Film Transistor (TFT) or a Metal Oxide semiconductor field effect Transistor (MOS), which is not limited herein. Depending on the type of each transistor and the signal of the gate of each transistor, the first electrode of each transistor may be a source and the second electrode may be a drain, or the first electrode of each transistor may be a drain and the second electrode may be a source, which is not particularly limited herein.
The operation of the pixel circuit provided by the embodiment of the present invention is described below with reference to a circuit timing diagram. In the following description, 1 represents a high level, and 0 represents a low level. It should be noted that 1 and 0 are logic levels, which are only used to better explain the specific operation of the embodiment of the present invention, and not specific voltage values.
Taking the pixel circuit shown in fig. 3 as an example, a timing chart corresponding to an input signal is shown in fig. 4. The timing diagram of the signals shown in fig. 4 includes: an initialization phase T1, a threshold compensation phase T2, a data writing phase T3, and a light emission phase T4. The voltage of the signal of the first voltage terminal VDD is VDD, and the voltage of the signal of the second voltage terminal VSS is VSS.
In the initialization stage T1, EM is 1, Gate is 1, Reset is 1;
since Gate is 1, the second transistor M2 is turned on, and the voltage Vref of the signal of the Data signal terminal Data is supplied to the second pole D of the driving transistor M0. Since EM is equal to 1, the third transistor M3 and the fourth transistor M4 are turned on, the turned-on fourth transistor M4 provides the signal of the first voltage terminal VDD to the first pole S of the driving transistor M0, and the voltage of the first pole S of the driving transistor M0 is VDD. The turned-on third transistor M3 supplies a signal of the second electrode D of the driving transistor M0 to the first electrode of the light emitting device 104, and the first electrode of the light emitting device 104 is initialized. Since Reset is equal to 1, the first transistor M1 is turned on, the voltage Vdd of the first electrode S of the driving transistor M0 is supplied to the gate G of the driving transistor M0, and the voltage of the signal at the gate G of the driving transistor M0 is Vdd. The first capacitor C1 stores the voltage of the gate G of the driving transistor M0 and the second pole D of the driving transistor M0; the second capacitor C2 stores the voltage of the first voltage terminal VDD and the gate G of the driving transistor M0.
A threshold compensation stage T2, where EM is 0, Gate is 1, and Reset is 1;
since EM is 0, the third transistor M3 and the fourth transistor M4 are turned off. Since Gate is 1, the second transistor M2 is turned on, the voltage Vdata of the signal of the Data signal terminal Data is supplied to the second pole D of the driving transistor M0, and the voltage of the second pole D of the driving transistor M0 is changed from Vref to Vdata. When Reset is 1, the first transistor M1 is turned on, the first electrode S of the driving transistor M0 is turned on with the gate G, the driving transistor M0 forms a diode structure, the gate voltage of the driving transistor M0 is discharged, and when the gate voltage of the driving transistor M0 is changed to Vdata + Vth, the driving transistor M0 is turned off. Where Vth is the threshold voltage of the drive transistor M0. The first capacitor C1 stores the voltage between the gate G of the driving transistor M0 and the second pole D of the driving transistor M0, and the second capacitor C2 stores the voltage between the first voltage terminal VDD and the gate G of the driving transistor M0.
A data writing phase T3, where EM is 0, Gate is 1, and Reset is 0;
since EM is 0, the third transistor M3 and the fourth transistor M4 are turned off. Since Reset is 0, the first transistor M1 is turned off. Since Gate 1 turns on the second transistor M2, the voltage Vref of the Data signal terminal Data signal is supplied to the second pole D of the driving transistor M0, the voltage of the second pole D of the driving transistor M0 is changed from Vdata to Vref, and the signal of the Gate G of the driving transistor M0 is changed from Vdata + Vth to Vref
Figure BDA0002197263560000091
The first capacitor C1 stores the voltage between the gate G of the driving transistor M0 and the second pole D of the driving transistor M0, and the second capacitor C2 stores the voltage between the first voltage terminal VDD and the gate G of the driving transistor M0.
A light-emitting period T4, where EM is 1, EM is 0, Gate is 0, and Reset is 0;
since Reset is 0, the first transistor M1 is turned off. Since Gate is 0, the second transistor M2 is turned off. Since EM is 1, the third transistor M3 and the fourth transistor M4 are turned on. The voltage of the second pole D of the driving transistor M0 changes from Vref to Voled + Vss. The turned-on fourth transistor M4 provides the signal of the first voltage terminal VDD to the first pole S of the driving transistor M0, and the turned-on third transistor M3 turns on the second pole D of the driving transistor M0 with the light emitting device 104. Voltage value V of signal driving gate G of transistor M0GThe change is as follows:
Figure BDA0002197263560000092
therefore, the voltage difference V between the gate G and the second pole D of the driving transistor M0 can be obtainedGDComprises the following steps:
Figure BDA0002197263560000101
the driving current I for driving the light emitting device to emit light by the driving transistor M0 is:
Figure BDA0002197263560000102
wherein the content of the first and second substances,
Figure BDA0002197263560000103
μnrepresenting the mobility of the drive transistor DT, CoxIs the capacitance of the gate oxide layer in unit area,
Figure BDA0002197263560000104
to drive a crystalThe width-to-length ratio of the transistor DT, which is relatively stable in the same structure, can be calculated as a constant.
It can be known from the above formula that the driving current I outputted by the driving transistor M0 is not affected by the threshold voltage Vth of the driving transistor M0 and the voltage drop of the first voltage source VDD, so that the problems of the threshold voltage shift and the voltage drop of the first voltage source VDD caused by the process and long-time operation of the driving transistor M0 are improved, and the display effect is improved.
Further, it can be known from the above formula that the Data signal terminal Data only needs to supply the appropriate voltage Vdata, that is, the driving current I is not affected by the on-voltage value Voled of the light emitting device 104. Further, when the light emitting device 104 is aged to cause the on voltage value thereof to change, the driving current of the driving transistor M0 driving the light emitting device 104 to emit light can be prevented from being affected by the aging degree of the light emitting device by adjusting the voltage Vdata of the Data voltage terminal Data.
Example II,
Fig. 5 is a schematic structural diagram of a pixel circuit according to an embodiment of the present invention, which is a modification of the first embodiment. Only the differences between the present embodiment and the first embodiment will be described below, and the descriptions of the same parts are omitted here.
In specific implementation, in the pixel circuit provided in the embodiment of the present invention, the threshold compensation module 103 further includes a fourth sub-module, wherein a gate of the driving transistor is coupled to the second end of the second capacitor through the fourth sub-module; the fourth sub-module is configured to turn on the gate of the driving transistor and the second terminal of the second capacitor in response to a signal of the scan signal terminal.
In practical implementation, in the pixel circuit provided in the embodiment of the invention, the fourth sub-module includes a fifth transistor M5, a Gate of the fifth transistor M5 is coupled to the scan signal terminal Gate, a first pole of the fifth transistor M5 is coupled to the second terminal of the second capacitor C2, and a second pole of the fifth transistor M5 is coupled to the Gate of the driving transistor M0.
The operation of the pixel circuit provided by the embodiment of the present invention is described below with reference to a circuit timing diagram. In the following description, 1 represents a high level, and 0 represents a low level. It should be noted that 1 and 0 are logic levels, which are only used to better explain the specific operation of the embodiment of the present invention, and not specific voltage values.
Taking the pixel circuit shown in fig. 5 as an example, a timing chart corresponding to an input signal is shown in fig. 6. The timing diagram of signals shown in fig. 6 includes: an initialization phase T1, a threshold compensation phase T2, a data writing phase T3, a buffering phase T3', and a light emitting phase T4. The voltage of the signal of the first voltage terminal VDD is VDD, and the voltage of the signal of the second voltage terminal VSS is VSS.
In the initialization stage T1, EM is 1, Gate is 1, Reset is 1;
since Gate is 1, the second transistor M2 and the fifth transistor M5 are turned on. The turned-on second transistor M2 supplies the voltage Vref of the signal of the Data signal terminal Data to the second pole D of the driving transistor M0. The fifth transistor M5 connects the second terminal of the second capacitor C2 to the gate of the driving transistor M0. Since EM is equal to 1, the third transistor M3 and the fourth transistor M4 are turned on, the turned-on fourth transistor M4 provides the signal of the first voltage terminal VDD to the first pole S of the driving transistor M0, and the voltage of the first pole S of the driving transistor M0 is VDD. The turned-on third transistor M3 supplies a signal of the second electrode D of the driving transistor M0 to the first electrode of the light emitting device 104, and the first electrode of the light emitting device 104 is initialized. Since Reset is equal to 1, the first transistor M1 is turned on, the voltage Vdd of the first electrode S of the driving transistor M0 is supplied to the gate G of the driving transistor M0, and the voltage of the signal at the gate G of the driving transistor M0 is Vdd. The first capacitor C1 stores the voltage of the gate G of the driving transistor M0 and the second pole D of the driving transistor M0; the second capacitor C2 stores the voltage of the first voltage terminal VDD and the gate G of the driving transistor M0.
A threshold compensation stage T2, where EM is 0, Gate is 1, and Reset is 1;
since EM is 0, the third transistor M3 and the fourth transistor M4 are turned off. Since the Gate is 1, the second transistor M2 and the fifth transistor M5 are turned on, and the turned-on second transistor M2 supplies the voltage Vref of the signal of the Data signal terminal Data to the second pole D of the driving transistor M0. The turned-on fifth transistor M5 turns on the second terminal of the second capacitor C2 and the gate G of the driving transistor M0. Since Reset is 1, the first transistor M1 is turned on, the first electrode S of the driving transistor M0 is turned on with the gate G, the driving transistor M0 forms a diode structure, the gate voltage of the driving transistor M0 is discharged, when the gate voltage of the driving transistor M0 changes from Vdd to Vref + Vth, the driving transistor M0 is turned off, and Vdd-Vref > Vth. Where Vth is the threshold voltage of the drive transistor M0. The first capacitor C1 stores the voltage between the gate G of the driving transistor M0 and the second pole D of the driving transistor M0, and the second capacitor C2 stores the voltage between the first voltage terminal VDD and the gate G of the driving transistor M0.
A data writing phase T3, where EM is 0, Gate is 1, and Reset is 0;
since EM is 0, the third transistor M3 and the fourth transistor M4 are turned off. Since Reset is 0, the first transistor M1 is turned off. Since Gate is 1, the second transistor M2 and the fifth transistor M5 are turned on, the voltage Vdata of the signal at the Data signal terminal Data is supplied to the second pole D of the driving transistor M0, the voltage of the second pole D of the driving transistor M0 is changed from Vref to Vdata, and the signal at the Gate G of the driving transistor M0 is changed from Vref + Vth to Vdata
Figure BDA0002197263560000121
The first capacitor C1 stores the voltage between the gate G of the driving transistor M0 and the second pole D of the driving transistor M0, and the second capacitor C2 stores the voltage between the first voltage terminal VDD and the gate G of the driving transistor M0. Due to the assurance of VGD>Vth, therefore V needs to be guaranteedG-VD>Vth, thereby making it possible to
Figure BDA0002197263560000122
Eventually make Vref>Vdata. Wherein, VGVoltage value, V, of signal representing gate G of driving transistor M0DRepresenting the voltage level of the signal driving the second pole D of the transistor M0.
A buffering period T3', EM ═ 0, Gate ═ 0, Reset ═ 0;
since EM is 0, the third transistor M3 and the fourth transistor M4 are turned off. Since Gate is 0, the second transistor M2 and the fifth transistor M5 are turned off. Since Reset ═0, the first transistor M1 is turned off. At this time, the voltage across the first capacitor C1 is the same as the voltage of the gate G and the second pole D of the driving transistor M0 during the data writing period T3, i.e. the voltage across the first capacitor C1 is the same as the voltage across the gate G and the second pole D of the driving transistor M0 during the data writing period T3
Figure BDA0002197263560000123
The first capacitor C1 stores the voltage between the gate G of the driving transistor M0 and the second pole D of the driving transistor M0, and the second capacitor C2 stores the voltage between the first voltage terminal VDD and the first pole of the fifth transistor M5.
A light-emitting period T4, where EM is 1, EM is 0, Gate is 0, and Reset is 0;
since Reset is 0, the first transistor M1 is turned off. Since Gate is 0, the second transistor M2 and the fifth transistor M5 are turned off. Since EM is 1, the third transistor M3 and the fourth transistor M4 are turned on. The voltage of the second pole D of the driving transistor M0 is changed from Vdata to Voled + Vss. The turned-on fourth transistor M4 provides the signal of the first voltage terminal VDD to the first pole S of the driving transistor M0, and the turned-on third transistor M3 turns on the second pole D of the driving transistor M0 with the light emitting device 104. The voltage difference V between the gate G and the second pole D of the driving transistor M0GDComprises the following steps:
Figure BDA0002197263560000131
the driving current I for driving the light emitting device to emit light by the driving transistor M0 is:
Figure BDA0002197263560000132
wherein the content of the first and second substances,
Figure BDA0002197263560000133
μnrepresenting the mobility of the drive transistor DT, CoxIs the capacitance of the gate oxide layer in unit area,
Figure BDA0002197263560000134
these values are relatively stable in the same structure for the aspect ratio of the driving transistor DT and can be calculated as constants.
It can be known from the above formula that the driving current I outputted by the driving transistor M0 is not affected by the threshold voltage Vth of the driving transistor M0 and the voltage drop of the first voltage source VDD, so that the problems of the threshold voltage shift and the voltage drop of the first voltage source VDD caused by the process and long-time operation of the driving transistor M0 are improved, and the display effect is improved.
Based on the same inventive concept, the embodiment of the present invention further provides a driving method of a pixel circuit provided by the embodiment of the present invention, as shown in fig. 7, the method includes steps 701 to 704;
step 701, in an initialization stage, the data writing module responds to a signal of the scanning signal end and provides a signal of the data signal end to the second pole of the driving transistor; the threshold compensation module responds to a signal of the reset signal end and resets the grid of the driving transistor; the light-emitting control module responds to a signal of the light-emitting control terminal, provides a signal of a first voltage terminal to a first pole of the driving transistor, and conducts a second pole of the driving transistor with the light-emitting device;
step 702, in the threshold compensation stage, the data writing module responds to the signal of the scanning signal end and provides the signal of the data signal end to the second pole of the driving transistor; the threshold compensation module compensates the threshold voltage of the driving transistor;
step 703, in the data writing phase, the data writing module responds to the signal of the scanning signal terminal and provides the signal of the data signal terminal to the second pole of the driving transistor;
step 704, in a light emitting stage, the light emitting control module provides a signal of the first voltage end to the first pole of the driving transistor in response to the signal of the light emitting control end, and turns on the second pole of the driving transistor and the light emitting device; the driving transistor generates a driving current according to the gate voltage and the second pole voltage of the driving transistor to drive the light emitting device to emit light by the driving current.
Based on the same inventive concept, the embodiment of the invention further provides a display device, which comprises the pixel circuit provided by the embodiment of the invention. The implementation of the display device can refer to the above embodiments of the pixel circuit, and repeated descriptions are omitted.
In specific implementation, the display device provided in the embodiment of the present invention may be a full-screen mobile phone as shown in fig. 8. Of course, the display device provided in the embodiment of the present invention may also be: any product or component with a display function, such as a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, a navigator and the like. Other essential components of the display device are understood by those skilled in the art, and are not described herein or should not be construed as limiting the invention.
The pixel circuit, the driving method thereof and the display device provided by the embodiment of the invention comprise a driving transistor, a data writing module, a light emitting control module, a threshold compensation module and a light emitting device; the data writing module is configured to provide a signal of the data signal terminal to the second pole of the driving transistor in response to a signal of the scan signal terminal; the threshold compensation module is configured to reset the gate of the driving transistor and compensate for a threshold voltage of the driving transistor in response to a signal of the reset signal terminal; the light emitting control module is configured to provide a signal of a first voltage terminal to a first pole of the driving transistor and to conduct a second pole of the driving transistor with the light emitting device in response to a signal of the light emitting control terminal; the driving transistor is configured to generate a driving current according to a gate voltage and a second diode voltage of the driving transistor to drive the light emitting device to emit light by the driving current. Therefore, the pixel circuit provided by the embodiment of the invention can compensate the threshold voltage of the driving transistor through the mutual matching of the module and the element, so that the driving current for driving the light-emitting device to emit light is not influenced by the threshold voltage of the driving module, and the problem of uneven light-emitting brightness caused by uneven threshold voltage is solved. In addition, the voltage of the first voltage end can be compensated through the mutual matching of the module and the element, so that the driving current is not influenced by the voltage of the first voltage end, and the problem of uneven light emitting brightness caused by the IR Drop of the first voltage end can be solved.

Claims (5)

1. A pixel circuit is characterized by comprising a driving transistor, a data writing module, a light emitting control module, a threshold compensation module and a light emitting device;
the data writing module is configured to provide a signal of a data signal terminal to the second pole of the driving transistor in response to a signal of a scan signal terminal;
the threshold compensation module is configured to reset the gate of the driving transistor and compensate for a threshold voltage of the driving transistor in response to a signal of a reset signal terminal;
the light emitting control module is configured to provide a signal of a first voltage terminal to a first pole of the driving transistor and to conduct a second pole of the driving transistor with the light emitting device in response to a signal of a light emitting control terminal;
the driving transistor is configured to generate a driving current according to a gate voltage and a second pole voltage of the driving transistor to drive the light emitting device to emit light by the driving current;
the threshold compensation module comprises a first sub-module, a second sub-module, a third sub-module and a fourth sub-module; the first sub-module is configured to store a voltage of a gate of the driving transistor and a second pole of the driving transistor; the second sub-module is configured to conduct the first pole of the driving transistor and the gate of the driving transistor in response to a signal of the reset signal terminal; the third sub-module is configured to store a voltage of the first voltage terminal and a gate of the driving transistor;
the first sub-module comprises a first capacitor, wherein a first end of the first capacitor is coupled with the second pole of the driving transistor, and a second end of the first capacitor is coupled with the grid electrode of the driving transistor;
the second sub-module comprises a first transistor, a grid electrode of the first transistor is coupled with the reset signal end, a first pole of the first transistor is coupled with a first pole of the driving transistor, and a second pole of the first transistor is coupled with the grid electrode of the driving transistor;
the third sub-module includes: a second capacitor, wherein one end of the second capacitor is coupled to the first voltage end, and a second end of the second capacitor is coupled to the gate of the driving transistor;
the grid electrode of the driving transistor is coupled with the second end of the second capacitor through the fourth submodule; the fourth sub-module is configured to conduct the gate of the driving transistor and the second end of the second capacitor in response to a signal of the scan signal end; the fourth sub-module comprises a fifth transistor, a gate of the fifth transistor is coupled to the scan signal terminal, a first pole of the fifth transistor is coupled to the second terminal of the second capacitor, and a second pole of the fifth transistor is coupled to the gate of the driving transistor;
the driving transistor is configured to initialize a grid electrode, a first pole and a second pole thereof in an initialization stage;
the fifth transistor is further configured to block the second terminal of the second capacitor from the gate of the driving transistor during a buffering phase and a light emitting phase.
2. The pixel circuit according to claim 1, wherein the data writing module comprises a second transistor, a gate of the second transistor is coupled to the scan signal terminal, a first pole of the second transistor is coupled to the data signal terminal, and a second pole of the second transistor is coupled to the second pole of the driving transistor.
3. The pixel circuit according to claim 1, wherein the light emission control module includes a third transistor and a fourth transistor;
a gate of the third transistor is coupled to the light emitting control terminal, a first pole of the third transistor is coupled to the second pole of the driving transistor, and the second pole of the third transistor is coupled to the first pole of the light emitting device;
a gate of the fourth transistor is coupled to the light emission control terminal, a first pole of the fourth transistor is coupled to the first voltage terminal, and a second pole of the fourth transistor is coupled to the first pole of the driving transistor.
4. A display device comprising the pixel circuit according to any one of claims 1 to 3.
5. A driving method using the pixel circuit according to any one of claims 1 to 3, comprising:
the data writing module responds to the signal of the scanning signal end and provides the signal of the data signal end to the second pole of the driving transistor in the initialization stage; the threshold compensation module responds to a signal of the reset signal end to reset the grid electrode of the driving transistor; the light-emitting control module responds to a signal of the light-emitting control terminal, provides a signal of the first voltage terminal to a first pole of the driving transistor, and conducts a second pole of the driving transistor and the light-emitting device;
a threshold compensation stage, wherein the data writing module responds to the signal of the scanning signal end and provides the signal of the data signal end to the second pole of the driving transistor; the threshold compensation module compensates the threshold voltage of the driving transistor;
a data writing stage, wherein the data writing module responds to the signal of the scanning signal end and provides the signal of the data signal end to the second pole of the driving transistor;
a light emitting stage, wherein the light emitting control module responds to a signal of the light emitting control terminal, provides a signal of the first voltage terminal to a first pole of the driving transistor, and conducts a second pole of the driving transistor with the light emitting device; the driving transistor generates a driving current according to a gate voltage and a second pole voltage of the driving transistor to drive the light emitting device to emit light by the driving current.
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