CN112802429B - Pixel driving circuit and display panel - Google Patents
Pixel driving circuit and display panel Download PDFInfo
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- CN112802429B CN112802429B CN202110269329.8A CN202110269329A CN112802429B CN 112802429 B CN112802429 B CN 112802429B CN 202110269329 A CN202110269329 A CN 202110269329A CN 112802429 B CN112802429 B CN 112802429B
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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]
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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]
- G09G3/3275—Details of drivers for data electrodes
- G09G3/3291—Details of drivers for data electrodes in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0233—Improving the luminance or brightness uniformity across the screen
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
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- Electroluminescent Light Sources (AREA)
- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
Abstract
The embodiment of the application provides a pixel driving circuit and a display panel, wherein the pixel driving circuit further comprises a compensation module; the compensation module comprises a fourth thin film transistor, a first capacitor and a second capacitor; one of the source electrode and the drain electrode of the fourth thin film transistor is electrically connected with the grid electrode of the driving thin film transistor; a first electrode plate of the first capacitor is electrically connected to the grid electrode of the driving thin film transistor, and a second electrode plate is electrically connected to one of a source electrode and a drain electrode of the driving thin film transistor; and the third polar plate of the second capacitor is electrically connected to the second polar plate, and the fourth polar plate is electrically connected to the second power supply voltage end. The pixel driving circuit and the display panel provided by the embodiment of the application can effectively compensate the threshold voltage drift of the driving thin film transistor, and further improve the display quality of the display panel applied to the pixel driving circuit.
Description
Technical Field
The application relates to the technical field of display, in particular to a pixel driving circuit and a display panel.
Background
Active Matrix/Organic Light Emitting Diode (AMOLED) display is a display technology applied to televisions and mobile devices, and has a wide application prospect in portable electronic devices sensitive to power consumption due to the characteristics of low power consumption, low cost and large size.
In the AMOLED display field, as the service life of the display panel is prolonged, the threshold voltage of the driving thin film transistor in the pixel driving circuit of the display panel is easy to drift, so that the driving current of the driving thin film transistor is changed, the brightness of the display panel is uneven, the display defect occurs, and the image quality of the display panel is further affected.
Therefore, how to improve the conventional pixel driving circuit and display panel is to solve the technical problems that the threshold voltage of the driving thin film transistor is easy to drift, so that the brightness of the display panel is uneven, the display is poor, and the image quality of the display panel is further affected.
Disclosure of Invention
The embodiment of the application provides a pixel driving circuit and a display panel, which can effectively compensate the threshold voltage drift of a driving thin film transistor, and further improve the display quality of the display panel applied to the pixel driving circuit.
The embodiment of the application provides a pixel driving circuit, which comprises an organic light-emitting device, a driving thin film transistor and a compensation module, wherein the compensation module comprises a fourth thin film transistor, a first capacitor and a second capacitor;
one of a source and a drain of the fourth thin film transistor is electrically connected to a first voltage end, and the other of the source and the drain of the fourth thin film transistor is electrically connected to a gate of the driving thin film transistor; the first capacitor comprises a first polar plate and a second polar plate which are opposite, the first polar plate is electrically connected with the grid electrode of the driving thin film transistor, and the second polar plate is electrically connected with one of a source electrode and a drain electrode of the driving thin film transistor; the second capacitor comprises a third polar plate and a fourth polar plate which are opposite, the third polar plate is electrically connected with the second polar plate, and the fourth polar plate is electrically connected with a second power supply voltage end.
Optionally, in some embodiments of the present application, the pixel driving circuit further includes a data voltage writing module, the data voltage writing module includes a second thin film transistor, one of a source and a drain of the second thin film transistor is electrically connected to a data voltage terminal, and the other of the source and the drain of the second thin film transistor is electrically connected to the gate of the driving thin film transistor and the first plate.
Optionally, in some embodiments of the present application, the pixel driving circuit further includes a reset module, and the reset module is connected to the source and the drain of the driving thin film transistor for resetting.
Optionally, in some embodiments of the present application, the reset module includes a third thin film transistor and a fifth thin film transistor, one of a source and a drain of the third thin film transistor is electrically connected to the common mode voltage terminal, and the other of the source and the drain of the third thin film transistor is electrically connected to one of a source and a drain of the driving thin film transistor; one of a source and a drain of the fifth thin film transistor is electrically connected to a reference voltage terminal, and the other of the source and the drain of the fifth thin film transistor is electrically connected to one of a source and a drain of the driving thin film transistor.
Optionally, in some embodiments of the present application, a voltage of the reference voltage terminal is greater than a voltage of the first voltage terminal, and the voltage of the first voltage terminal is greater than a voltage of the common mode voltage terminal; the difference value between the voltage of the first voltage end and the voltage of the common mode voltage end is larger than the threshold voltage value of the driving thin film transistor.
Optionally, in some embodiments of the present application, the pixel driving circuit further includes a light emission control module, where the light emission control module includes a sixth thin film transistor; wherein one of a source electrode and a drain electrode of the sixth thin film transistor is electrically connected to a cathode electrode of the organic light emitting device, and the other of the source electrode and the drain electrode of the sixth thin film transistor is electrically connected to one of a source electrode and a drain electrode of the driving thin film transistor.
Optionally, in some embodiments of the present application, the anode of the organic light emitting device is electrically connected to the first power voltage terminal.
Optionally, in some embodiments of the present application, the pixel driving circuit further includes a switch module, and the switch module includes a seventh thin film transistor; one of a source and a drain of the seventh thin film transistor is electrically connected to one of a source and a drain of the driving thin film transistor, and the other of the source and the drain of the seventh thin film transistor is electrically connected to the second power voltage terminal.
Optionally, in some embodiments of the present application, the first thin film transistor, the second thin film transistor, the third thin film transistor, the fourth thin film transistor, the fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are all n-type thin film transistors.
Correspondingly, an embodiment of the present application further provides a display panel, including the pixel driving circuit described in any one of the above.
According to the pixel drive circuit and the display panel, the voltage-dividing capacitor is additionally arranged on the basis of the original pixel drive circuit, so that the drive current value of the drive thin film transistor is an amount irrelevant to the threshold voltage, the threshold voltage drift of the drive thin film transistor is effectively compensated, and the display quality of the display panel applied to the pixel drive circuit is improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, 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 of a pixel driving circuit according to an embodiment of the present disclosure.
FIG. 2 is a timing diagram of different signals in a pixel driving circuit according to an embodiment of the present disclosure;
fig. 3 is a graph illustrating potential changes of a first node and a second node at different stages of a pixel driving circuit according to an embodiment of the disclosure.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The embodiment of the application provides a pixel driving circuit and a display panel. The following are detailed below. It should be noted that the following description of the embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of the present application, the term "including" means "including but not limited to". The terms first, second, third and the like are used merely as labels, and do not impose numerical requirements or an established order. Various embodiments of the invention may exist in a range of versions; it is to be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention; accordingly, the described range descriptions should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, it is contemplated that the description of a range from 1 to 6 has specifically disclosed sub-ranges such as, for example, from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within a range such as, for example, 1, 2, 3, 4, 5, and 6, as applicable regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any number (fractional or integer) recited within the indicated range.
The embodiment of the application aims at the technical problems that the threshold voltage of a driving thin film transistor is easy to drift, so that the brightness of a display panel is uneven, bad display occurs and the image quality of the display panel is further influenced in the conventional pixel driving circuit and the display panel, and the technical problems can be solved.
Fig. 1 is a schematic diagram of a pixel driving circuit according to an embodiment of the invention. Wherein the pixel driving circuit includes an organic light emitting device including: a first thin film transistor T1, a second thin film transistor T2, a third thin film transistor T3, a fourth thin film transistor T4, a fifth thin film transistor T5, a sixth thin film transistor T6, a seventh thin film transistor T7, a first capacitor Cst, a second capacitor Cc, and an organic light emitting device OLED, wherein the first thin film transistor T1 is a driving thin film transistor, a gate of the first thin film transistor T1 is electrically connected to a first node g, one of a source and a drain of the first thin film transistor T1 is electrically connected to a second node S, and the other of the source and the drain of the first thin film transistor is electrically connected to a third node D; optionally, in a preferred embodiment of the present application, the first thin film transistor T1, the second thin film transistor T2, the third thin film transistor T3, the fourth thin film transistor T4, the fifth thin film transistor T5, the sixth thin film transistor T6, and the seventh thin film transistor T7 are all n-type thin film transistors.
Specifically, the pixel driving circuit further comprises a compensation module, a data voltage writing module, a reset module, a light emitting control module and a switch module;
the compensation module includes the fourth thin film transistor T4, the first capacitor Cst, and the second capacitor Cc, a gate of the fourth thin film transistor T4 is connected to a third light-emitting enable signal EM3, a drain of the fourth thin film transistor T4 is electrically connected to a first voltage terminal V1, and a source of the fourth thin film transistor T4 is electrically connected to a gate of the first thin film transistor T1; the first capacitor Cst includes a first plate and a second plate opposite to each other, the first plate is electrically connected to the gate of the first thin film transistor T1, and the second plate is electrically connected to the source of the first thin film transistor T1; the second capacitor Cc includes a third plate and a fourth plate opposite to each other, the third plate is electrically connected to the second plate, and the fourth plate is electrically connected to the second power voltage terminal OVSS.
Specifically, the Data voltage writing module includes a second thin film transistor T2, a gate of the second thin film transistor T2 is connected to a writing signal WR, a drain of the second thin film transistor T2 is electrically connected to a Data voltage terminal Data, and a source of the second thin film transistor T2 is electrically connected to the first node G.
Specifically, the reset module is connected to the source and the drain of the first thin film transistor T1 for resetting; the reset module includes a third thin film transistor T3 and a fifth thin film transistor T5, a gate of the third thin film transistor T3 is connected to the read signal RD, a drain of the third thin film transistor T3 is electrically connected to the common mode voltage terminal Vcm, and a source of the third thin film transistor T3 is electrically connected to the second node S; a gate of the fifth thin film transistor T5 is connected to the third light emission enable signal EM3, a drain of the fifth thin film transistor T5 is electrically connected to a reference voltage terminal Vref, and a source of the fifth thin film transistor T5 is electrically connected to the third node G.
Optionally, in a preferred embodiment of the present application, the voltage of the reference voltage terminal Vref is greater than the voltage of the first voltage terminal V1, and the voltage of the first voltage terminal V1 is greater than the voltage of the common mode voltage terminal Vcm; the difference between the voltage of the first voltage terminal V1 and the voltage of the common mode voltage terminal Vcm is greater than the voltage value of the threshold voltage Vth of the first thin film transistor T1.
Specifically, the light emitting control module includes a sixth thin film transistor T6; the gate of the sixth thin film transistor T6 is connected to the first light-emitting enable signal EM1, the drain is connected to the anode of the organic light-emitting device OLED, and the source is electrically connected to the third node D.
Further, an anode of the organic light emitting device OLED is electrically connected to the first power voltage terminal OVDD, and a cathode of the organic light emitting device OLED is electrically connected to a drain of the sixth thin film transistor T6.
Specifically, the switching module includes a seventh thin film transistor T7; a gate of the seventh thin film transistor T7 is connected to the second light emission enable signal EM2, a drain thereof is connected to the second node S, and a source thereof is electrically connected to the second power voltage terminal OVSS.
Optionally, in a preferred embodiment of the present application, the writing signal WR, the reading signal RD, the Data voltage Data, the first light emission enable signal EM1, the second light emission enable signal EM2, and the third light emission enable signal EM3 are all provided by an external driving chip. Specifically, the pixel driving circuit passes through a reset phase P1, a detection phase P2, a first sustain phase P3, a data voltage writing phase P4, a second sustain phase P5 and a light emitting phase P6, respectively.
When the pixel driving circuit is in the reset phase P1, the third thin film transistor T3, the fourth thin film transistor T4, and the fifth thin film transistor T5 are all in an on state, the third thin film transistor T3 resets the potential of the first node G, the fourth thin film transistor T4 resets the potential of the second node S, and the fifth thin film transistor T5 resets the potential of the third node D;
when the pixel driving circuit is in the detection phase P2, the first thin film transistor T1, the fourth thin film transistor T4 and the fifth thin film transistor T5 are in an on state, and the pixel driving circuit charges the second node S until the potential of the second node S is a first fixed value;
when the pixel driving circuit is in the first sustain phase P3, the potentials of the first node G, the second node S, and the third node D are respectively sustained;
when the pixel driving circuit is in the Data voltage writing phase P4, a Data voltage Data is written into the first node G through the second thin film transistor T2, and the first capacitor Cst and the second capacitor Cc divide the Data voltage Data into the second node S;
when the pixel driving circuit is in the second sustain phase P5, potentials of the first node G, the second node S, and the third node D are respectively sustained;
when the pixel driving circuit is in the light emitting phase P6, the sixth thin film transistor T6 and the seventh thin film transistor T7 are in an on state, and the first thin film transistor T1 drives the organic light emitting device OLED to emit light.
As shown in fig. 2, a timing diagram of different signals in the pixel driving circuit according to the embodiment of the present application is provided; as shown in fig. 3, the potential variation diagrams of the first node G and the second node S at different stages of the pixel driving circuit provided in the embodiment of the present application are shown. As can be seen from fig. 2 and 3, in the pixel driving circuit, the first light-emitting enable signal EM1, the second light-emitting enable signal EM2, the third light-emitting enable signal EM3, the write signal WR, the read signal RD, and the Data voltage Data are all ac voltages, and the power positive voltage OVDD, the reference voltage Vref, the first voltage V1, and the common mode voltage Vcm are all direct voltages.
As can be seen from fig. 1, fig. 2 and fig. 3, the specific processes of the pixel driving circuit at different stages are as follows:
when the pixel driving circuit is in the reset phase P1, the first and second emission enable signals EM1 and EM2 change from a high potential to a low potential; at this time, the sixth thin film transistor T6 and the seventh thin film transistor T7 are in an off state, the sixth thin film transistor T6 disconnects the organic light emitting device OLED from the first thin film transistor T1, and the seventh thin film transistor T7 disconnects the organic light emitting device OLED from the second power voltage terminal OVSS.
Meanwhile, the read signal RD and the third emission enable signal EM3 change from a low potential to a high potential; at this time, the third thin film transistor T3, the fourth thin film transistor T4, and the fifth thin film transistor T5 are turned on, the third thin film transistor T3 resets the potential of the first node G, the fourth thin film transistor T4 resets the potential of the second node S, and the fifth thin film transistor T5 resets the potential of the third node D. At this time, the rest signals maintain the original potential, the potential of the first node G is V1, the potential of the second node S is Vcm, and the potential of the third node D is Vref.
When the pixel driving circuit is in the detection phase P2, the first light-emitting enable signal EM1 is at a low potential, the second light-emitting enable signal EM2 is at a low potential, the read signal RD changes from a high potential to a low potential, the third light-emitting enable signal EM3 is at a high potential, the Data voltage Data is at a low potential, and the write signal WR is at a low potential; at this time, the second, third, sixth, and seventh thin film transistors T2, T3, T6, and T7 are in an off state, and the fourth and fifth thin film transistors T4 and T5 are in an on state.
At this time, the gate voltage Vg of the first thin film transistor T1 is V1, and the source voltage Vs of the first thin film transistor T4 is Vcm. Under a preset condition, the voltage value of the reference voltage terminal Vref is greater than the voltage value of the first voltage terminal V1, the voltage value of the first voltage terminal V1 is greater than the voltage value of the common mode voltage terminal Vcm, and the voltage difference between the first voltage terminal V1 and the common mode voltage terminal Vcm is greater than the threshold voltage Vth value of the first thin film transistor T1.
Therefore, the voltage Vgs between the gate and the source of the first thin film transistor T1 is V1-Vcm > Vth, the first thin film transistor T1 is in the on state, and at this time, the voltage value of the reference voltage value Vref charges the source of the first thin film transistor T1 (the second node S) until the potential of the second node S is V1-Vth, and the potential of the first node G maintains V1.
When the pixel driving circuit is in the first sustain phase P3, the first emission enable signal EM1 maintains a low potential, the second emission enable signal EM2 maintains a low potential, the read signal RD maintains a low potential, the write signal WR maintains a low potential, and the third emission enable signal EM3 changes from a high potential to a low potential; at this time, the second thin film transistor T2, the third thin film transistor T3, the fourth thin film transistor T4, the fifth thin film transistor T5, the sixth thin film transistor T6, and the seventh thin film transistor T7 are in an off state, the first node G is disconnected from the first voltage V1, the third node D is disconnected from the reference voltage terminal Vref, the potential of the second node S is maintained at V1-Vth, and the first fixed value is V1-Vth; the potential of the first node G remains constant at V1.
When the pixel driving circuit is in the data voltage writing phase P4, the first emission enable signal EM1 maintains a low potential, the second emission enable signal EM2 maintains a low potential, the third emission enable signal EM3 maintains a low potential, the read signal RD maintains a low potential, and the write signal WR changes from a low potential to a high potential; at this time, the third thin film transistor T3, the fourth thin film transistor T4, the fifth thin film transistor T5, the sixth thin film transistor T6, and the seventh thin film transistor T7 maintain the off state, the second thin film transistor T2 is in the on state, the Data voltage Data is written into the first node G through the second thin film transistor T2, the write signal WR is changed from the high potential to the low potential, the thin film transistor T2 is in the off state, the Data voltage Data is disconnected from the first node G, and at this time, the potential of the first node G is the voltage value Vdata of the Data voltage terminal Data.
Since the first capacitor Cst and the second capacitor Cc have capacitive reactance when passing through the alternating current, according to the principle of capacitive voltage division, the voltage across the capacitors is inversely proportional to the capacitance during the series connection of the first capacitor Cst and the second capacitor Cc. Therefore, the potential of the first node G is V1 during the first sustain phase P3, the potential of the first node G is Vdata during the data voltage writing phase P4, and the potential variation Δ Vg thereof is Vdata-V1; according to the principle of capacitive voltage division, the potential variation Δ Vs/Δ Vg of the second node S is Cst/(Cst + Cc), and the potential variation Δ Vs of the second node S is (Vdata-V1) × Cst/(Cst + Cc); since the potential of the second node S is V1-Vth in the first sustain phase P3, the potential of the first node G is Vdata in the data voltage writing phase P4, the potential of the second node S is (Vdata-V1) × Cst/(Cst + Cc) + V1-Vth, and the gate-source voltage of the first thin film transistor T1 is:
Vgs＝Vdata-(Vdata-V1)*Cst/(Cst+Cc)-V1+Vth。
when the pixel driving circuit is in the second sustain phase P5, the first emission enable signal EM1 is maintained at a low potential, the second emission enable signal EM2 is maintained at a low potential, the third emission enable signal EM3 is maintained at a low potential, the read signal RD is maintained at a low potential, and the write signal WR is maintained at a low potential; at this time, the second thin film transistor T2, the third thin film transistor T3, the fourth thin film transistor T4, the fifth thin film transistor T5, the sixth thin film transistor T6, and the seventh thin film transistor T7 maintain the off state, the potential of the first node G maintains Vdata, and the potential of the second node S maintains (Vdata-V1) ((Vdata-Cc) + V1-Vth).
When the pixel driving circuit is in the light-emitting period P6, the first light-emitting enable signal EM1 changes from a low potential to a high potential, the second light-emitting enable signal EM2 changes from a low potential to a high potential, the third light-emitting enable signal EM3 maintains a low potential, the read signal RD maintains a low potential, and the write signal WR maintains a low potential; at this time, the second, third, fourth, and fifth thin film transistors T2, T3, T4, and T5 maintain an off state, and the sixth and seventh thin film transistors T6 and T7 are in an on state. Meanwhile, the gate-source voltage Vgs of the first thin film transistor T1 is:
Vdata-(Vdata-V1)*Cst/(Cst+Cc)-V1+Vth；
at this time, the first thin film transistor T1 is in an on state, and the first thin film transistor T1 drives the organic light emitting device OLED to emit light.
According to the known calculation formula 1 for calculating the driving current, I isOLED＝K*(Vgs-Vth)2(ii) a Wherein, IOLEDK is a current amplification factor of the first thin film transistor T1 (driving thin film transistor) determined by electrical characteristics of the first thin film transistor T1 itself, Vgs is a voltage difference between a gate and a source of the first thin film transistor T1, and Vth is a threshold voltage of the first thin film transistor T1. It can be seen that the driving current IOLED of the organic light emitting device OLED is related to the threshold voltage Vth of the driving thin film transistor. The threshold voltage Vth of the driving thin film transistor is easy to shift, so that the driving current I is causedOLEDThe brightness of the OLED display panel is easily uneven due to the change, the display is poor, and the image quality is affected.
In the embodiment of the present application, since the voltage Vgs between the gate and the source of the first thin film transistor T1 is Vdata- (Vdata-V1) × Cst/(Cst + Cc) -V1+ Vth, the driving current of the embodiment of the present application is obtained by substituting the above formula 1:
IOLED＝K*(Vgs-Vth)2＝K*(Vdata-(Vdata-V1)*Cst/(Cst+Cc)-V1+Vth-Vth)2＝
K*(Vdata-(Vdata-V1)*Cst/(Cst+Cc)-V1)2。
therefore, the driving current I of the embodiment of the present applicationOLEDIs a quantity independent of the threshold voltage Vth of the driving TFT, and thus can compensate for voltage variation therewithThe influence of (c).
The embodiment of the application also provides a display panel, and the display panel comprises the pixel driving circuit in the embodiment.
The display panel may be a mobile phone, a computer, a television, an intelligent wearable display device, and the like, which is not particularly limited in this embodiment.
To sum up, the pixel driving circuit and the display panel provided in the embodiment of the present application add a second capacitor on the basis of the original pixel driving circuit, so that the driving current value of the driving thin film transistor is an amount unrelated to the threshold voltage, thereby effectively compensating the threshold voltage drift of the driving thin film transistor, and further improving the display quality of the display panel applied to the pixel driving circuit.
In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
The pixel driving circuit and the display panel provided by the embodiments of the present application are described in detail above, and the principles and embodiments of the present application are described herein by applying specific examples, and the description of the embodiments is only used to help understand the method and the core idea of the present application; meanwhile, for those skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.
Claims (8)
1. A pixel driving circuit comprises an organic light emitting device and a driving thin film transistor, and is characterized by further comprising a compensation module and a reset module, wherein the reset module is connected to a source electrode and a drain electrode of the driving thin film transistor for resetting;
the compensation module includes:
one of a source and a drain of the fourth thin film transistor is electrically connected to the first voltage terminal, and the other of the source and the drain of the fourth thin film transistor is electrically connected to the gate of the driving thin film transistor;
a first capacitor including a first electrode plate and a second electrode plate opposite to each other, the first electrode plate being electrically connected to the gate of the driving thin film transistor, and the second electrode plate being electrically connected to one of a source and a drain of the driving thin film transistor; and
the second capacitor comprises a third polar plate and a fourth polar plate which are opposite, the third polar plate is electrically connected with the second polar plate, and the fourth polar plate is electrically connected with a second power supply voltage end;
the reset module includes:
a third thin film transistor and a fifth thin film transistor, wherein one of a source and a drain of the third thin film transistor is electrically connected to a common mode voltage terminal, and the other of the source and the drain of the third thin film transistor is electrically connected to one of a source and a drain of the driving thin film transistor; one of a source and a drain of the fifth thin film transistor is electrically connected to a reference voltage terminal, and the other of the source and the drain of the fifth thin film transistor is electrically connected to one of a source and a drain of the driving thin film transistor.
2. The pixel driving circuit according to claim 1, further comprising a data voltage writing module, wherein the data voltage writing module comprises a second thin film transistor, one of a source and a drain of the second thin film transistor is electrically connected to a data voltage terminal, and the other of the source and the drain of the second thin film transistor is electrically connected to the gate of the driving thin film transistor and the first plate.
3. The pixel driving circuit according to claim 2, wherein the voltage of the reference voltage terminal is greater than the voltage of the first voltage terminal, and the voltage of the first voltage terminal is greater than the voltage of the common mode voltage terminal; the difference value between the voltage of the first voltage end and the voltage of the common mode voltage end is larger than the threshold voltage value of the driving thin film transistor.
4. The pixel driving circuit according to claim 3, further comprising a light emission control module including a sixth thin film transistor; wherein one of a source electrode and a drain electrode of the sixth thin film transistor is electrically connected to a cathode electrode of the organic light emitting device, and the other of the source electrode and the drain electrode of the sixth thin film transistor is electrically connected to one of a source electrode and a drain electrode of the driving thin film transistor.
5. The pixel driving circuit according to claim 4, wherein the anode of the organic light emitting device is electrically connected to a first power voltage terminal.
6. The pixel driving circuit according to claim 5, further comprising a switch module, wherein the switch module comprises a seventh thin film transistor; one of a source and a drain of the seventh thin film transistor is electrically connected to one of a source and a drain of the driving thin film transistor, and the other of the source and the drain of the seventh thin film transistor is electrically connected to the second power voltage terminal.
7. The pixel driving circuit according to claim 6, wherein the driving thin film transistor, the second thin film transistor, the third thin film transistor, the fourth thin film transistor, the fifth thin film transistor, the sixth thin film transistor, and the seventh thin film transistor are all n-type thin film transistors.
8. A display panel comprising the pixel driving circuit according to any one of claims 1 to 7.
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| CN205282057U (en) * | 2016-01-04 | 2016-06-01 | 京东方科技集团股份有限公司 | Pixel drive circuit, display panel and display device |
| CN106652912B (en) * | 2016-12-13 | 2020-05-19 | 上海天马有机发光显示技术有限公司 | Organic light-emitting pixel driving circuit, driving method and organic light-emitting display panel |
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