CN109147673B - Pixel circuit, driving method thereof and display device - Google Patents
Pixel circuit, driving method thereof and display device Download PDFInfo
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- CN109147673B CN109147673B CN201811096572.9A CN201811096572A CN109147673B CN 109147673 B CN109147673 B CN 109147673B CN 201811096572 A CN201811096572 A CN 201811096572A CN 109147673 B CN109147673 B CN 109147673B
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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
- G09G3/3233—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 with pixel circuitry controlling the current through the light-emitting element
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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]
- G09G3/3266—Details of drivers for scan electrodes
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- Computer Hardware Design (AREA)
- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- 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, and belongs to the technical field of display. The pixel circuit includes a control circuit connected to a control signal terminal, a direct current power supply terminal, and a control node, respectively, the control node being connected to the gate of the driving transistor. Because the control circuit can output the direct current power supply signal at the second potential to the control node (namely to the grid electrode of the driving transistor) under the control of the control signal end, the time length of the grid electrode of the driving transistor at the first potential can be shortened, the degree of negative deviation of the threshold voltage of the driving transistor is reduced, and the display effect of the display device is improved.
Description
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
The pixel unit generally includes an Organic Light Emitting Diode (OLED) device and a pixel circuit for driving the OLED device, and the transistor in the pixel circuit is generally a P-type transistor. Since the P-type transistor operates under a negative voltage, a threshold voltage of the P-type transistor may negatively shift, which may reduce a current flowing through the OLED device and affect a display effect of the display apparatus.
In the related art, when the current flowing through the OLED device is reduced due to a negative shift of the threshold voltage of the transistor, the current flowing through the OLED device may be compensated by using an internal compensation or external compensation method, so as to improve the display effect of the display device.
However, since the related art can compensate the current flowing through the OLED device only when the threshold voltage of the transistor is negatively shifted, its compensation capability is limited. If the threshold voltage of the transistor has a large negative offset, the current flowing through the OLED device may not be effectively compensated, and the display effect of the display device is poor.
Disclosure of Invention
The invention provides a pixel circuit, a driving method thereof and a display device, which can solve the problem of poor display effect of the display device in the related technology, and the technical scheme is as follows:
in a first aspect, a pixel circuit is provided, the pixel circuit including: the light-emitting control circuit comprises a driving transistor;
the control circuit is respectively connected with a control signal terminal, a direct current power supply terminal and a control node, the control circuit is used for responding to a control signal output by the control signal terminal and outputting a direct current power supply signal from the direct current power supply terminal to the control node, and the grid electrode of the driving transistor is connected with the control node;
the reset circuit is respectively connected with a reset signal end, an initialization signal end, the control node and the light-emitting unit, and is used for responding to a reset signal output by the reset signal end and outputting an initialization signal from the initialization signal end to the control node and the light-emitting unit;
the light-emitting control circuit is respectively connected with the control node, the direct current power end, the driving power end, the data signal end, the light-emitting control signal end and the light-emitting unit, and is used for responding to the driving power signal output by the driving power end and the control node, writing the data signal output by the data signal end into the driving transistor, and responding to the direct current power signal, the light-emitting control signal output by the light-emitting control signal end and the control node, outputting a driving signal to the light-emitting unit, and driving the light-emitting unit to emit light.
Optionally, the control circuit includes: a first transistor;
the grid electrode of the first transistor is connected with the control signal end, the first pole of the first transistor is connected with the direct current power supply end, and the second pole of the first transistor is connected with the control node.
Optionally, the light emission control circuit includes: a compensation sub-circuit, a data writing sub-circuit, a control sub-circuit and the driving transistor;
the compensation sub-circuit is respectively connected with the driving power supply end, the control node and a second pole of the driving transistor, and is used for responding to the driving power supply signal and controlling the potential of the second pole of the driving transistor to be the potential of the control node;
the data writing sub-circuit is respectively connected with the driving power supply end, the data signal end and the first pole of the driving transistor, and is used for responding to the driving power supply signal and outputting the data signal to the first pole of the driving transistor;
the control sub-circuit is respectively connected to the light-emitting control signal terminal, the dc power terminal, the first electrode of the driving transistor, the second electrode of the driving transistor, and the light-emitting unit, and the control sub-circuit is configured to respond to the dc power signal, the light-emitting control signal, and the control node, and output the driving signal to the light-emitting unit to drive the light-emitting unit to emit light.
Optionally, the compensation sub-circuit comprises a second transistor; the data write sub-circuit includes a third transistor;
a gate of the second transistor is connected to the driving power supply terminal, a first pole of the second transistor is connected to the control node, and a second pole of the second transistor is connected to the second pole of the driving transistor;
the gate of the third transistor is connected to the driving power source terminal, the first pole of the third transistor is connected to the data signal terminal, and the second pole of the third transistor is connected to the first pole of the driving transistor.
Optionally, the control sub-circuit includes: a fourth transistor and a fifth transistor;
a gate of the fourth transistor is connected to the light emission control signal terminal, a first electrode of the fourth transistor is connected to the dc power supply terminal, and a second electrode of the fourth transistor is connected to the first electrode of the driving transistor;
the grid electrode of the fifth transistor is connected with the light-emitting control signal end, the first electrode of the fifth transistor is connected with the second electrode of the driving transistor, and the second electrode of the fifth transistor is connected with the light-emitting unit.
Optionally, the light emission control circuit further includes: a capacitor;
one end of the capacitor is connected with the direct current power supply end, and the other end of the capacitor is connected with the control node.
Optionally, the reset circuit includes: a sixth transistor and a seventh transistor; gates of the sixth transistor and the seventh transistor are connected to the reset signal terminal, first poles of the sixth transistor and the seventh transistor are connected to the initialization signal terminal, a second pole of the sixth transistor is connected to the control node, and a second pole of the seventh transistor is connected to the light emitting unit.
Optionally, the transistor included in the control circuit, the transistor included in the reset circuit, and the transistor included in the light emission control circuit are all P-type transistors.
In a second aspect, there is provided a driving method of a pixel circuit, which is applied to the pixel circuit according to the first aspect, the method including:
in the control stage, the potential of a control signal output by a control signal end is a first potential, a control circuit responds to the control signal and outputs a direct-current power supply signal from a direct-current power supply end to a control node, the potential of the direct-current power supply signal is a second potential, and the grid of a driving transistor is connected with the control node;
in the initialization stage, the potential of the control signal is a second potential, the potential of the initialization signal output by the initialization signal end is a first potential, the potential of the reset signal output by the reset signal end is a first potential, and the reset circuit responds to the reset signal and outputs the initialization signal to the control node and the light-emitting unit;
a signal writing stage in which the potential of the control node is maintained at a first potential, the potential of the reset signal is a second potential, the potential of the data signal output by the data signal terminal is a second potential, the potential of the driving power signal output by the driving power terminal is a first potential, and the light emission control circuit writes the data signal into the driving transistor in response to the driving power signal and the control node;
and in the light emitting stage, the potential of the control node is kept at a first potential, the potential of the driving power supply signal is a second potential, the potential of a light emitting control signal output by the light emitting control signal end is a first potential, and the light emitting control circuit responds to the direct current power supply signal, the light emitting control signal and the control node, outputs a driving signal to the light emitting unit and drives the light emitting unit to emit light.
In a third aspect, there is provided a display device including: a plurality of pixel cells, each of the pixel cells comprising: a pixel circuit according to the first aspect and a light emitting unit connected to the pixel circuit.
The technical scheme provided by the invention has the beneficial effects that:
in summary, embodiments of the present invention provide a pixel circuit, a driving method thereof, and a display device. The pixel circuit includes a control circuit connected to a control signal terminal, a direct current power supply terminal, and a control node, respectively, the control node being connected to the gate of the driving transistor. Because the control circuit can output the direct current power supply signal at the second potential to the control node (namely to the grid electrode of the driving transistor) under the control of the control signal end, the time length of the grid electrode of the driving transistor at the first potential can be shortened, the degree of negative deviation of the threshold voltage of the driving transistor is reduced, and the display effect of the display device is improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic diagram illustrating a driving current of a driving transistor in a pixel circuit according to an embodiment of the invention varying with a gate-source voltage difference;
FIG. 2 is a diagram illustrating the threshold voltage of a driving transistor varying with time according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a pixel circuit according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of another pixel circuit according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of another pixel circuit according to an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of a pixel circuit according to yet another embodiment of the present invention;
fig. 7 is a flowchart of a driving method of a pixel circuit according to an embodiment of the present invention;
FIG. 8 is a timing diagram of signal terminals in a pixel circuit according to an embodiment of the present invention;
fig. 9 is a circuit layout diagram of a pixel circuit according to an embodiment of the present invention.
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 with reference to the accompanying drawings.
The transistors used in all embodiments of the present invention may be thin film transistors or field effect transistors or other devices having the same characteristics, and the transistors used in embodiments of the present invention are mainly switching transistors depending on the role in the circuit. Since the source and drain of the switching transistor used herein are symmetrical, the source and drain may be interchanged. In the embodiment of the present invention, the source is referred to as a first pole, and the drain is referred to as a second pole. The form of the figure provides that the middle end of the transistor is a grid, the signal input end is a source, and the signal output end is a drain. In addition, the switching transistor used in the embodiment of the present invention may include any one of a P-type switching transistor that is turned on when the gate is at a low level and turned off when the gate is at a high level and an N-type switching transistor that is turned on when the gate is at a high level and turned off when the gate is at a low level. In addition, in each embodiment of the present invention, each of the plurality of signals corresponds to a first potential and a second potential, and the first potential and the second potential represent only 2 different state quantities of the potential of the signal, and do not represent that the first potential or the second potential has a specific value throughout the text.
The pixel unit generally includes an OLED device and a driving transistor for driving the OLED device, and since the driving transistor is generally a P-type transistor which is turned on at a negative voltage, a threshold voltage Vth of the driving transistor may suddenly shift in a negative direction during an initial operation, or shift in a negative direction after a long-term operation, which may cause a reduction in current input to the OLED device, thereby causing a series of problems in the display device.
For example, when the threshold voltage Vth of the driving transistor is shifted in the negative direction, the luminance of the switched screen and the luminance of the screen before switching may not be consistent when the display device switches the screen, and a partial image of the screen before switching may remain on the switched screen in a short time, that is, the efficiency of the switched screen is slow, so that the display device may have an image sticking problem.
Fig. 1 is a schematic diagram of a variation of a driving current Ids of a driving transistor with a gate-source voltage difference Vgs according to an embodiment of the present invention. As shown in fig. 1, the horizontal axis represents the gate-source voltage difference Vgs of the driving transistor, and the vertical axis represents the driving current Ids of the driving transistor. As can be seen from fig. 1, when switching from a black screen having a grayscale value of 255 to a gray screen having a grayscale value of 48, the variation width of the drive current Ids corresponding to the gate-source voltage difference Vgs of the drive transistor whose threshold voltage Vth is shifted in the negative direction is larger than the variation width of Ids corresponding to the Vgs of the drive transistor whose threshold voltage Vth is not shifted in the negative direction. That is, when the threshold voltage Vth of the driving transistor is shifted in the negative direction, the luminance difference between two frames with different gray levels is large, and the image sticking problem may be caused.
For another example, when the threshold voltage Vth of the driving transistor is initially operated and a negative shift occurs suddenly to reduce the current input to the OLED device, the luminance of the First Frame displayed by the display device may be reduced, resulting in a poor First Frame luminance (FFR). In addition, when the threshold voltage Vth of the driving transistor is shifted in the negative direction to a serious degree, the display luminance of the entire display device may be lowered.
Referring to fig. 1, it can be seen that the driving current Ids of the driving transistor with the threshold voltage Vth negatively shifted is smaller for the same gate-source voltage difference Vgs.
For another example, when the threshold voltage Vth of the driving transistor is shifted in the negative direction, the driving current Ids of the driving transistor may be reduced, resulting in a problem of current drop.
Fig. 2 is a schematic diagram of a threshold voltage Vth of a driving transistor varying with time according to an embodiment of the present invention. As shown in fig. 2, the horizontal axis represents time, and the vertical axis represents the threshold voltage Vth of the driving transistor. As can be seen from fig. 2, the threshold voltage Vth of the driving transistor is shifted in the negative direction continuously with the change in time.
In order to solve the above-mentioned problem caused by the negative shift of the threshold voltage Vth of the driving transistor, in the related art, the current flowing through the OLED device may be compensated by signal compensation (e.g. external compensation or internal compensation), and a Pulse Width Modulation (PWM) technique is used to assist the signal compensation. The method needs to design a compensation circuit, so that the cost is high, the compensation capability of the method is limited, and the problem of characteristic attenuation of the driving transistor caused by negative deviation of the threshold voltage Vth of the driving transistor cannot be solved. Or, in the related art, a higher positive voltage may be provided to the driving transistor in advance through an external device to solve the problem of negative shift of the threshold voltage Vth of the driving transistor, but since the driving transistor may not have a large negative shift during initial operation, the structure of the driving transistor may be damaged by inputting a higher positive voltage, and the operation of the driving transistor may be unstable.
Embodiments of the present invention provide a pixel circuit, which reduces the degree of negative shift of a threshold voltage Vth of a driving transistor by outputting a positive voltage to the driving transistor in advance. That is, the Aging (Aging) process is performed on the driving transistor in advance by using the positive voltage, so that the problem of characteristic attenuation caused by negative deviation of the threshold voltage Vth can be solved, and the problem of poor display effect of the display device caused by negative deviation of the threshold voltage Vth can be solved.
Fig. 3 is a schematic structural diagram of a pixel circuit according to an embodiment of the present invention. As shown in fig. 3, the pixel circuit 00 may include: a control circuit 10, a reset circuit 20, and a light emission control circuit 30, and the light emission control circuit 30 may include a driving transistor (not shown in fig. 3).
Referring to fig. 3, the control circuit 10 may be respectively connected to a control signal terminal a, a dc power source terminal VDD, and a control node P, and the control circuit 10 may output a dc power source signal from the dc power source terminal VDD to the control node P in response to a control signal output from the control signal terminal a. Wherein the gate of the driving transistor may be connected to the control node P.
For example, the control circuit 10 may output a dc power supply signal from the dc power supply terminal VDD to the control node P when the potential of the control signal output from the control signal terminal a is a first potential, and the potential of the dc power supply signal is a second potential. In an embodiment of the invention, the first potential may be an active potential, the second potential may be an inactive potential, and the first potential may be a low potential relative to the second potential.
In the embodiment of the present invention, since the gate of the driving transistor is connected to the control node P, the control circuit 10 can output the dc power signal at the second potential to the gate of the driving transistor under the control of the control signal (i.e. perform a positive Aging process on the driving transistor), so as to shorten the time period that the gate of the driving transistor is at the first potential, reduce the degree of negative deviation of the threshold voltage Vth of the driving transistor, and further improve the display effect of the display device. In addition, the control circuit 10 can prevent the driving transistor from operating at the first potential for a long time, and reduce the degree of negative shift of the threshold voltage Vth of the driving transistor, so that the problem of characteristic degradation of the driving transistor due to the negative shift of the threshold voltage Vth of the driving transistor is effectively solved.
The reset circuit 20 may be connected to the reset signal terminal RST, the initialization signal terminal Vint, the control node P, and the light emitting unit L, respectively, and the reset circuit 20 may output the initialization signal from the initialization signal terminal Vint to the control node P and the light emitting unit L in response to a reset signal output from the reset signal terminal RST.
For example, the reset circuit 20 may output an initialization signal from the initialization signal terminal Vint, which may have a potential of the first potential, to the control node P and the light emitting unit L when the potential of the reset signal output from the reset signal terminal RST is the first potential.
The light-emitting control circuit 30 may be respectively connected to the control node P, the dc power terminal VDD, the driving power terminal G, the data signal terminal D, the light-emitting control signal terminal EM, and the light-emitting unit L, and the light-emitting control circuit 30 may write the data signal output from the data signal terminal D into the driving transistor in response to the driving power signal output from the driving power terminal G and the control node P, and may output the driving signal to the light-emitting unit L in response to the dc power signal, the light-emitting control signal output from the light-emitting control signal terminal EM, and the control node P to drive the light-emitting unit L to emit light. Wherein, the potential of the data signal is a second potential.
The driving signal may be a driving current output by the driving transistor under the driving of a dc power signal provided by the dc power source VDD.
For example, the light emission control circuit 30 may write the data signal output from the data signal terminal D to the driving transistor under the control of the driving power signal and the control node P when the potential of the driving power signal output from the driving power terminal G is the first potential. And the light-emitting control circuit 30 may output a driving signal to the light-emitting unit L to drive the light-emitting unit L to emit light under the control of the light-emitting control signal, the control node P and the dc power signal when the potential of the light-emitting control signal output from the light-emitting control signal terminal EM is the first potential.
In summary, the embodiments of the present invention provide a pixel circuit, which includes a control circuit connected to a control signal terminal, a dc power terminal and a control node, respectively, where the control node is connected to the gate of the driving transistor. Because the control circuit can output the direct current power supply signal at the second potential to the control node (namely to the grid electrode of the driving transistor) under the control of the control signal end, the time length of the grid electrode of the driving transistor at the first potential can be shortened, the degree of negative deviation of the threshold voltage of the driving transistor is reduced, and the display effect of the display device is improved.
Fig. 4 is a schematic structural diagram of another pixel circuit according to an embodiment of the present invention, and as shown in fig. 4, the control circuit 10 may include: the first transistor M1.
The gate of the first transistor M1 may be connected to the control signal terminal a, the first pole of the first transistor M1 may be connected to the dc power source terminal VDD, and the second pole of the first transistor M1 may be connected to the control node P.
Fig. 5 is a schematic structural diagram of another pixel circuit according to an embodiment of the present invention, and as shown in fig. 5, the light-emitting control circuit 30 may include: a compensation sub-circuit 301, a data writing sub-circuit 302, a control sub-circuit 303, and a drive transistor T.
Referring to fig. 5, the compensation sub-circuit 301 may be connected to the driving power source terminal G, the control node P, and the second pole of the driving transistor T, respectively, and the compensation sub-circuit 301 may control the potential of the second pole of the driving transistor T to be the potential of the control node P in response to the driving power source signal.
For example, the compensation sub-circuit 301 may control the potential of the second pole of the driving transistor T to be the potential of the control node P when the potential of the driving power supply signal output from the driving power supply terminal G is the first potential.
The data writing sub-circuit 302 may be respectively connected to the driving power terminal G, the data signal terminal D, and the first pole of the driving transistor T, and the data writing sub-circuit 302 may output a data signal to the first pole of the driving transistor T in response to a driving power signal.
For example, the data writing sub-circuit 302 may output the data signal to the first electrode of the driving transistor T when the potential of the driving power supply signal output from the driving power supply terminal G is the first potential.
The control sub-circuit 303 may be respectively connected to the light-emitting control signal terminal EM, the dc power terminal VDD, the first pole of the driving transistor T, the second pole of the driving transistor T, and the light-emitting unit L, and the control sub-circuit 303 may output a driving signal to the light-emitting unit L in response to the dc power signal, the light-emitting control signal, and the control node P to drive the light-emitting unit L to emit light.
For example, the control sub-circuit 303 may output a driving signal to the light emitting unit L to drive the light emitting unit L to emit light under the control of the light emission control signal, the dc power signal and the control node P when the potential of the light emission control signal output from the light emission control signal terminal EM is the first potential.
Alternatively, referring to fig. 4, the compensation sub-circuit 301 may include a second transistor M2. The data write sub-circuit 302 includes a third transistor M3.
The gate of the second transistor M2 may be connected to the driving power terminal G, the first pole of the second transistor M2 may be connected to the control node P, and the second pole of the second transistor M2 may be connected to the second pole of the driving transistor T.
The gate of the third transistor M3 may be connected to the driving power terminal G, the first pole of the third transistor M3 may be connected to the data signal terminal D, and the second pole of the third transistor M3 may be connected to the first pole of the driving transistor T.
Alternatively, referring to fig. 4, the control sub-circuit 303 may include: a fourth transistor M4 and a fifth transistor M5.
The gate of the fourth transistor M4 may be connected to the emission control signal terminal EM, the first pole of the fourth transistor M4 may be connected to the dc power source terminal VDD, and the second pole of the fourth transistor M4 may be connected to the first pole of the driving transistor T.
The gate of the fifth transistor M5 may be connected to the emission control signal terminal EM, the first pole of the fifth transistor M5 may be connected to the second pole of the driving transistor T, and the second pole of the fifth transistor M5 may be connected to the light emitting cell L.
Fig. 6 is a schematic structural diagram of another pixel circuit according to an embodiment of the present invention, and as shown in fig. 6, the light-emitting control circuit 30 may further include: and a capacitor C.
One end of the capacitor C may be connected to the dc power source terminal VDD, and the other end of the capacitor C may be connected to the control node P.
The capacitor C may be used to store a data signal input to the driving transistor T.
Alternatively, referring to fig. 4 and 6, the reset circuit 20 may include: a sixth transistor M6 and a seventh transistor M7.
The gates of the sixth and seventh transistors M6 and M7 may be connected to a reset signal terminal RST, the first poles of the sixth and seventh transistors M6 and M7 may be connected to an initialization signal terminal Vint, the second pole of the sixth transistor M6 may be connected to the control node P, and the second pole of the seventh transistor M7 may be connected to the light emitting unit L. In addition, as can be seen with reference to fig. 4 and 6, the light emitting unit L may also be connected to a low-level power source terminal VSS.
Note that, in the embodiment of the present invention, the transistor included in the control circuit 10, the transistor included in the reset circuit 20, and the transistor included in the light emission control circuit 30 may all be P-type transistors. Accordingly, the first potential is low relative to the second potential.
In summary, the present invention provides a pixel circuit. The pixel circuit includes a control circuit connected to a control signal terminal, a direct current power supply terminal, and a control node, respectively, the control node being connected to the gate of the driving transistor. Because the control circuit can output the direct current power supply signal at the second potential to the control node (namely to the grid electrode of the driving transistor) under the control of the control signal end, the time length of the grid electrode of the driving transistor at the first potential can be shortened, the degree of negative deviation of the threshold voltage of the driving transistor is reduced, and the display effect of the display device is improved.
Fig. 7 is a flowchart of a driving method of a pixel circuit according to an embodiment of the present invention, where the method may be applied to the pixel circuit shown in any one of fig. 3 to 6, and as shown in fig. 7, the method may include:
In the embodiment of the present invention, before the initialization phase, in the control phase, the potential of the control signal output from the control signal terminal a is the first potential, and the control circuit 10 may output the dc power signal at the second potential to the control node P under the control of the control signal.
Since the gate of the driving transistor T included in the pixel circuit is connected to the control node P, the control circuit 10 can output the dc power signal at the second potential to the gate of the driving transistor T under the control of the control signal, so as to shorten the time period that the gate of the driving transistor is at the first potential, reduce the degree of negative deviation of the threshold voltage Vth of the driving transistor, and improve the display effect of the display device. In addition, the control circuit 10 can prevent the driving transistor from operating at the first potential for a long time, and reduce the degree of negative shift of the threshold voltage Vth of the driving transistor, so that the problem of characteristic degradation of the driving transistor due to the negative shift of the threshold voltage Vth of the driving transistor is effectively solved.
In the embodiment of the present invention, in the initialization phase, the potential of the reset signal output by the reset signal terminal RST is the first potential, and the reset circuit 20 can output the initialization signal at the first potential to the control node P and the light emitting unit L under the control of the reset signal, so as to reset the control node P and the light emitting unit L.
In the embodiment of the present invention, during the signal writing phase, the P potential of the control node is maintained at the first potential, the potential of the driving power signal outputted from the driving power terminal G is at the first potential, and the light emission control circuit 30 can write the data signal at the second potential outputted from the data signal terminal D to the driving transistor T under the control of the driving power signal and the control node P.
In the embodiment of the present invention, during the light emitting period, the P potential of the control node is maintained at the first potential, the potential of the light emitting control signal output by the light emitting control signal terminal EM is the first potential, and the light emitting control circuit 30 may output the driving signal to the light emitting unit L under the control of the light emitting control signal, the control node P and the dc power signal, so as to drive the light emitting unit L to emit light.
In summary, embodiments of the present invention provide a driving method for a pixel circuit, in which a control circuit in the pixel circuit can output a dc power signal at a second potential to a control node (i.e., to a gate of a driving transistor) under the control of a control signal output by a control signal terminal before an initialization stage, so as to shorten a duration that the gate of the driving transistor is at a first potential, reduce a degree of negative shift of a threshold voltage of the driving transistor, and further improve a display effect of a display device.
Taking the pixel circuit shown in fig. 6 as an example, and taking each transistor in the pixel circuit as a P-type transistor, the first potential is a low potential relative to the second potential as an example, the driving principle of the pixel circuit provided by the embodiment of the invention is described in detail.
Fig. 8 is a timing diagram of each signal terminal in the pixel circuit according to the embodiment of the invention, as shown in fig. 8, in the control phase t1, the potential of the control signal outputted from the control signal terminal a is the first potential, the first transistor M1 is turned on, and the dc power source terminal VDD outputs the dc power signal at the second potential to the control node P through the first transistor M1. Since the gate of the driving transistor T is connected to the control node P, that is, in the control phase T1, the dc power source terminal VDD may output the dc power signal at the second potential to the gate of the driving transistor T through the first transistor M1, so as to reduce the degree of negative deviation of the threshold voltage when the driving transistor T operates at the first potential for a long time. In the control phase t1, the potential of the reset signal output from the reset signal terminal RST, the potential of the driving power signal output from the driving power terminal G, and the potential of the emission control signal output from the emission control signal terminal EM are all the second potentials, and accordingly, the second transistor M2, the third transistor M3, the fourth transistor M4, the fifth transistor M5, the sixth transistor M6, and the seventh transistor M7 are all turned off.
In the initialization period t2, the potential of the control signal outputted from the control signal terminal a jumps to the second potential, and the first transistor M1 is turned off. The potential of the initialization signal output by the initialization signal terminal Vint is a first potential, the potential of the reset signal output by the reset signal terminal RST jumps to the first potential, the sixth transistor M6 and the seventh transistor M7 are turned on, and the initialization signal terminal Vint outputs the initialization signal at the first potential to the control node P through the sixth transistor M6 to realize the reset of the control node P; the initialization signal terminal Vint outputs an initialization signal at the first potential to the light emitting cell L through the seventh transistor M7 to implement resetting of the light emitting cell L. And in the initialization period t2, the potential of the driving power signal outputted from the driving power terminal G and the potential of the emission control signal outputted from the emission control signal terminal EM are both the second potential, and accordingly, the second transistor M2, the third transistor M3, the fourth transistor M4 and the fifth transistor M5 are all turned off.
In the data writing period T3, the potential of the control node P is maintained at the first potential, and the driving transistor T is turned on. The potential of the reset signal output from the reset signal terminal RST jumps to the second potential, and the sixth transistor M6 and the seventh transistor M7 are turned off. The potential of the data signal output from the data signal terminal D is the second potential, the potential of the driving power supply signal output from the driving power supply terminal G jumps to the first potential, the second transistor M2 and the third transistor M3 are turned on, the data signal terminal D writes the data signal to the driving transistor T through the second transistor M2 and the third transistor M3, and stores the data signal and the threshold voltage of the driving transistor T in the capacitor C. And in this data writing phase t3, the potential of the emission control signal outputted from the emission control signal terminal EM is the second potential, and accordingly, both the fourth transistor M4 and the fifth transistor M5 are turned off.
In the light emitting period T4, the potential of the dc power signal is the second potential, the potential of the control node P is maintained at the first potential, and the driving transistor T is turned on. The potential of the driving power signal outputted from the driving power signal terminal G jumps to the second potential, and the second transistor M2 and the third transistor M3 are turned off. The potential of the light emission control signal outputted from the light emission control signal terminal EM is the first potential, the fourth transistor M4 and the fifth transistor M5 are turned on, the dc power supply terminal VDD inputs the dc power signal to the driving transistor T through the fourth transistor M4, and the driving transistor T outputs the driving current to the light emitting unit L through the fifth transistor M5 under the driving of the dc power signal, thereby driving the light emitting unit L to emit light.
Note that, in the embodiment of the present invention, the transistor included in the control circuit 10, the transistor included in the reset circuit 20, and the transistor included in the light emission control circuit 30 may all be P-type transistors. Accordingly, the first potential is low relative to the second potential.
In summary, embodiments of the present invention provide a driving method for a pixel circuit, in which a control circuit in the pixel circuit can output a dc power signal at a second potential to a control node (i.e., to a gate of a driving transistor) under the control of a control signal output by a control signal terminal before an initialization stage, so as to shorten a duration that the gate of the driving transistor is at a first potential, reduce a degree of negative shift of a threshold voltage of the driving transistor, and further improve a display effect of a display device.
In addition, an embodiment of the present invention further provides a display device, where the display device may include: a plurality of pixel units, each pixel unit may include: a pixel circuit as shown in any one of fig. 3 to 6, and a light emitting unit L connected to the pixel circuit. The display device may be: the display device comprises any product or component with a display function, such as a micro LED display substrate, a liquid crystal panel, electronic paper, an AMOLED panel, a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, a navigator and the like.
Fig. 9 is a circuit layout diagram of a pixel circuit according to an embodiment of the present invention. As can be seen from fig. 9, two sections of gate metal traces 1 and 2, which are not overlapped with the orthographic projection of the active layer ACT, and a source-drain metal trace 3 for connecting the two sections of gate metal traces are disposed in the pixel circuit, the source-drain metal trace 3 and the two sections of gate metal traces 1 and 2 are connected by vias 4 and 5 to form a gate of the first transistor M1, and the gate of the first transistor M1 may be connected to the control signal terminal a. Through setting the two sections of grid metal wires 1 and 2 which are not overlapped with the orthographic projection of the active layer ACT and the source drain metal layer wire 5 which is connected with the two grid metal layers 1 and 2, the phenomenon that when only one grid metal wire is arranged, another transistor is formed at the orthographic projection overlapping position of the grid metal wire and the active layer ACT can be avoided, and then the mixing of other signals can be avoided, and the working stability of the pixel circuit is ensured.
In addition, a formation structure of transistors (second to fifth transistors and a driving transistor) included in the light emission control circuit and transistors (sixth and seventh transistors) included in the reset circuit is also shown in fig. 9. The formation of the other transistors in the embodiments of the present invention is not described in detail.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the pixel circuit and the display device described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (9)
1. A pixel circuit, comprising: the light-emitting control circuit comprises a driving transistor;
the control circuit is respectively connected with a control signal terminal, a direct current power supply terminal and a control node, the control circuit is used for responding to a control signal output by the control signal terminal and outputting a direct current power supply signal from the direct current power supply terminal to the control node, and the grid electrode of the driving transistor is connected with the control node;
the reset circuit is respectively connected with a reset signal end, an initialization signal end, the control node and the light-emitting unit, and is used for responding to a reset signal output by the reset signal end and outputting an initialization signal from the initialization signal end to the control node and the light-emitting unit;
the light-emitting control circuit is respectively connected with the control node, the direct-current power supply end, the driving power supply end, the data signal end, the light-emitting control signal end and the light-emitting unit, and is used for responding to a driving power supply signal output by the driving power supply end and the control node, writing the data signal output by the data signal end into the driving transistor, and responding to the direct-current power supply signal, a light-emitting control signal output by the light-emitting control signal end and the control node, outputting a driving signal to the light-emitting unit, and driving the light-emitting unit to emit light;
wherein the light emission control circuit includes: and one end of the capacitor is connected with the direct current power supply end, and the other end of the capacitor is connected with the control node.
2. The pixel circuit according to claim 1, wherein the control circuit comprises: a first transistor;
the grid electrode of the first transistor is connected with the control signal end, the first pole of the first transistor is connected with the direct current power supply end, and the second pole of the first transistor is connected with the control node.
3. The pixel circuit according to claim 1, wherein the light emission control circuit further comprises: a compensation sub-circuit, a data writing sub-circuit, a control sub-circuit and the driving transistor;
the compensation sub-circuit is respectively connected with the driving power supply end, the control node and a second pole of the driving transistor, and is used for responding to the driving power supply signal and controlling the potential of the second pole of the driving transistor to be the potential of the control node;
the data writing sub-circuit is respectively connected with the driving power supply end, the data signal end and the first pole of the driving transistor, and is used for responding to the driving power supply signal and outputting the data signal to the first pole of the driving transistor;
the control sub-circuit is respectively connected to the light-emitting control signal terminal, the dc power terminal, the first electrode of the driving transistor, the second electrode of the driving transistor, and the light-emitting unit, and the control sub-circuit is configured to respond to the dc power signal, the light-emitting control signal, and the control node, and output the driving signal to the light-emitting unit to drive the light-emitting unit to emit light.
4. The pixel circuit according to claim 3, wherein the compensation sub-circuit comprises a second transistor; the data write sub-circuit includes a third transistor;
a gate of the second transistor is connected to the driving power supply terminal, a first pole of the second transistor is connected to the control node, and a second pole of the second transistor is connected to the second pole of the driving transistor;
the gate of the third transistor is connected to the driving power source terminal, the first pole of the third transistor is connected to the data signal terminal, and the second pole of the third transistor is connected to the first pole of the driving transistor.
5. The pixel circuit of claim 3, wherein the control sub-circuit comprises: a fourth transistor and a fifth transistor;
a gate of the fourth transistor is connected to the light emission control signal terminal, a first electrode of the fourth transistor is connected to the dc power supply terminal, and a second electrode of the fourth transistor is connected to the first electrode of the driving transistor;
the grid electrode of the fifth transistor is connected with the light-emitting control signal end, the first electrode of the fifth transistor is connected with the second electrode of the driving transistor, and the second electrode of the fifth transistor is connected with the light-emitting unit.
6. The pixel circuit according to any one of claims 1 to 5, wherein the reset circuit comprises: a sixth transistor and a seventh transistor;
gates of the sixth transistor and the seventh transistor are connected to the reset signal terminal, first poles of the sixth transistor and the seventh transistor are connected to the initialization signal terminal, a second pole of the sixth transistor is connected to the control node, and a second pole of the seventh transistor is connected to the light emitting unit.
7. The pixel circuit according to any of claims 1 to 5,
the transistors included in the control circuit, the transistors included in the reset circuit and the transistors included in the light-emitting control circuit are all P-type transistors.
8. A driving method of a pixel circuit, applied to the pixel circuit according to any one of claims 1 to 7, the method comprising:
in the control stage, the potential of a control signal output by a control signal end is a first potential, a control circuit responds to the control signal and outputs a direct-current power supply signal from a direct-current power supply end to a control node, the potential of the direct-current power supply signal is a second potential, and the grid of a driving transistor is connected with the control node;
in the initialization stage, the potential of the control signal is a second potential, the potential of the initialization signal output by the initialization signal end is a first potential, the potential of the reset signal output by the reset signal end is a first potential, and the reset circuit responds to the reset signal and outputs the initialization signal to the control node and the light-emitting unit;
a signal writing stage in which the potential of the control node is maintained at a first potential, the potential of the reset signal is a second potential, the potential of the data signal output by the data signal terminal is a second potential, the potential of the driving power signal output by the driving power terminal is a first potential, and the light emission control circuit writes the data signal into the driving transistor in response to the driving power signal and the control node;
and in the light emitting stage, the potential of the control node is kept at a first potential, the potential of the driving power supply signal is a second potential, the potential of a light emitting control signal output by the light emitting control signal end is a first potential, and the light emitting control circuit responds to the direct current power supply signal, the light emitting control signal and the control node, outputs a driving signal to the light emitting unit and drives the light emitting unit to emit light.
9. A display device, characterized in that the display device comprises: a plurality of pixel cells, each of the pixel cells comprising: a pixel circuit as claimed in any one of claims 1 to 7, and a light emitting unit connected to the pixel circuit.
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| KR101859474B1 (en) * | 2011-09-05 | 2018-05-23 | 엘지디스플레이 주식회사 | Pixel circuit of organic light emitting diode display device |
| KR102016614B1 (en) * | 2013-12-03 | 2019-09-02 | 삼성디스플레이 주식회사 | Organic light emitting display device and method for driving the same |
| US10431142B2 (en) * | 2016-11-14 | 2019-10-01 | Int Tech Co., Ltd. | Pixel circuit and electroluminescent display comprising the pixel circuit |
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| CN107464526B (en) * | 2017-09-28 | 2020-02-18 | 京东方科技集团股份有限公司 | Pixel compensation circuit, driving method thereof and display device |
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