CN111341245A - Pixel driving circuit, display panel and terminal equipment - Google Patents
Pixel driving circuit, display panel and terminal equipment Download PDFInfo
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- CN111341245A CN111341245A CN202010293027.XA CN202010293027A CN111341245A CN 111341245 A CN111341245 A CN 111341245A CN 202010293027 A CN202010293027 A CN 202010293027A CN 111341245 A CN111341245 A CN 111341245A
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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
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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
- G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
- G09G5/36—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the display of a graphic pattern, e.g. using an all-points-addressable [APA] memory
- G09G5/39—Control of the bit-mapped memory
- G09G5/393—Arrangements for updating the contents of the bit-mapped memory
Abstract
The embodiment of the application provides a pixel driving circuit, a display panel and a terminal device, in the pixel driving circuit, a control end of a driving transistor unit is connected with an adjustable storage capacitor unit comprising an adjustable capacitor unit, and the adjustable capacitor unit can continuously adjust a stored capacitance value according to different refresh frequencies of the display panel so as to store the capacitance value corresponding to the refresh frequency. Therefore, when the refresh frequency of the display panel changes, the adjustable capacitor unit adjusts the stored capacitance value, so that the duration of the conduction of the driving transistor unit maintained by the voltage of the control end of the driving transistor unit meets the requirement of the refresh frequency, and the variable frequency display of the display panel is realized, thereby meeting the requirements of different display image qualities and improving the user experience.
Description
Technical Field
The embodiment of the application relates to the technical field of display panels, in particular to a pixel driving circuit, a display panel and a terminal device.
Background
The pixel driving of the display panel is driven by a pixel driving circuit. The pixel drive circuit modulates light emission by controlling a drive current of the light emitting element.
In the prior art, a pixel driving circuit generally includes a switching transistor, a storage capacitor and a driving transistor, wherein the storage capacitor is used for maintaining a stable voltage signal at a control terminal of the driving transistor, so that the light emitting brightness of a light emitting element is kept unchanged.
The higher the refresh frequency of the display panel is, the better the image quality display is, and the more the power consumption is, so that the refresh frequency of the display panel can be set to a low frequency when the high quality image quality is not required, and the refresh frequency of the display panel can be set to a high frequency when the high quality image quality is required, thereby achieving the balance between the image quality and the power consumption. However, the conventional pixel driving circuit can only support a display panel with a fixed frequency, and cannot meet the requirement of the display panel on the refresh frequency.
Disclosure of Invention
The embodiment of the application provides a pixel driving circuit, a display panel and a terminal device, and the pixel driving circuit can be used for realizing frequency conversion display of the display panel.
In a first aspect, an embodiment of the present application provides a pixel driving circuit, including:
a driving transistor unit driving a light emitting device, a first end of the driving transistor unit being connected to a first voltage source, a second end of the driving transistor unit being connected to a first end of the light emitting device, and a second end of the light emitting device being connected to a second voltage source;
the adjustable storage capacitor unit comprises an adjustable capacitor unit, wherein the adjustable capacitor unit is connected to the control end of the driving transistor unit so as to adjust the capacitance value stored by the adjustable capacitor unit according to different refreshing frequencies of the display panel.
Optionally, the adjustable storage capacitor unit further includes: a fixed capacitor unit;
the fixed capacitor unit is respectively connected to the first voltage source and the control end of the driving transistor unit, and is used for storing a fixed capacitance value.
Optionally, the adjustable capacitance unit includes: and the source electrode and the drain electrode of the switching device are respectively connected with the control end of the driving transistor unit, and the control end of the switching device is connected with the common voltage of the display panel.
Optionally, the switching device includes a P-type thin film transistor, and/or the driving transistor unit includes a P-type thin film transistor.
Optionally, the method further includes:
and the first end of the compensation transistor unit is connected with the control end of the driving transistor unit, and the second end of the compensation transistor unit is connected with the second end of the driving transistor unit and used for controlling the communication between the control end of the driving transistor unit and the second end of the driving transistor unit.
Optionally, the method further includes:
and the first output end of the reset transistor unit is connected with the control end of the driving transistor unit, and the second output end of the reset transistor unit is connected with the first end of the light-emitting device and used for controlling the writing of initial voltage into the control end of the driving transistor unit and the first end of the light-emitting device.
Optionally: a data write transistor unit;
the first end of the data writing transistor unit is connected with a data line, and the second end of the data writing transistor unit is connected with the first end of the driving transistor unit and used for providing data voltage on the data line to the first end of the driving transistor unit.
Optionally, the method further includes: a first light emission control transistor unit and a second light emission control transistor unit;
the first end of the first light-emitting control transistor unit is connected with the first voltage source, the second end of the first light-emitting control transistor unit is connected with the first end of the driving transistor unit, and the first end of the first light-emitting control transistor unit is used for controlling the connection between the first voltage source and the first end of the driving transistor unit;
the first end of the second light-emitting control transistor unit is connected with the second end of the driving transistor unit, and the second end of the second light-emitting control transistor unit is connected with the first end of the light-emitting device and used for controlling the communication between the second end of the driving transistor unit and the first end of the light-emitting device.
In a second aspect, an embodiment of the present application provides a display panel including the pixel driving circuit described in any one of the first aspect of the embodiments of the present application.
In a third aspect, an embodiment of the present application provides a terminal device, which includes a processing device, a storage device, and the display panel according to the second aspect of the embodiment of the present application.
In the pixel driving circuit, the control terminal of the driving transistor unit is connected to an adjustable storage capacitor unit including an adjustable capacitor unit, and the adjustable capacitor unit can adjust a stored capacitance value according to different refresh frequencies of the display panel to store a capacitance value corresponding to the refresh frequency. Therefore, when the refresh frequency of the display panel changes, the adjustable capacitor unit adjusts the stored capacitance value, so that the duration of the conduction of the driving transistor unit maintained by the voltage of the control end of the driving transistor unit meets the requirement of the refresh frequency, and the variable frequency display of the display panel is realized, thereby meeting the requirements of different display image qualities and improving the user experience.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.
Fig. 1 is a schematic structural diagram of a pixel driving circuit according to an embodiment;
fig. 2 is a schematic structure of a pixel driving circuit according to an embodiment of the present disclosure;
fig. 3 is a schematic structure of a pixel driving circuit according to another embodiment of the present disclosure;
fig. 4 is a schematic structure of a pixel driving circuit according to another embodiment of the present disclosure;
FIG. 5 is a schematic diagram of a pixel driving circuit according to another embodiment of the present application
FIG. 6 is a driving timing diagram corresponding to the pixel driving circuit structure shown in FIG. 5;
fig. 7 is a schematic structural diagram of a display panel according to an embodiment of the present application;
fig. 8 is a schematic structural diagram of a terminal device according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, 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 some embodiments of the present application, but not all 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 transistors used in all embodiments of the present application can be transistors, thin film transistors, or field effect transistors or other devices with the same characteristics. In the embodiment of the present application, in order to distinguish two terminals of the transistor except for the control terminal, one of the poles is referred to as a first terminal, and the other pole is referred to as a second terminal.
When the transistor is a triode, the control end can be a base electrode, the first end can be a collector electrode, and the second end can be an emitter electrode; alternatively, the control terminal may be a base, the first terminal may be an emitter, and the second terminal may be a collector.
When the transistor is a thin film transistor or a field effect transistor, the control end can be a grid electrode, the first end can be a drain electrode, and the second end can be a source electrode; alternatively, the control terminal may be a gate, the first terminal may be a source, and the second terminal may be a drain.
The pixel driving of the display panel is driven by the pixel driving circuit, wherein, for the display panel, the more the number of times of refreshing the image displayed on the display panel is, the smaller the flicker of the image display is, and the higher the picture quality is. That is, the refresh frequency of the display panel is high, and the image quality display is better, but the power consumption is also high. Therefore, when high-quality image quality is not required, the refresh frequency of the display panel can be set to a low frequency, and when high-quality image quality is required, the refresh frequency of the display panel can be set to a high frequency, thereby achieving balance between image quality and power consumption.
For the display panel, when the display panel works at high frequency (refresh frequency is relatively high), the pixel charging time is shortened, and the holding time required by the control end voltage of the driving transistor is also shortened; when the display panel operates at a low frequency (the refresh frequency is relatively low), the pixel charging time becomes long, and the charging time required to drive the transistor control terminal potential also increases.
However, the conventional pixel driving circuit can only support a display panel with a fixed refresh frequency, and cannot meet the demand of the display panel for the refresh frequency. For example, in the circuit shown in fig. 1, the capacitance value stored by the fixed capacitor Cst is fixed, so that the stable voltage provided by the driving transistor T1 is fixed, that is, the voltage at the control terminal of the driving transistor T1, which can be maintained by the fixed capacitor Cst, is fixed and limited, so that the display panel can only display at the fixed refresh frequency.
Therefore, the embodiment of the present application proposes a concept that: because different refresh frequencies have different requirements on the stability of the voltage at the control terminal of the driving transistor, a variable capacitor unit can be connected to the control terminal of the driving transistor, and the capacitance value stored in the variable capacitor unit is related to the refresh frequency of the display panel. Therefore, when the refresh frequency of the display panel changes, the capacitance value stored by the variable capacitor unit changes accordingly, so that the stability of the control end of the driving transistor, which can be maintained by the stored capacitance value, meets the requirement of the current refresh frequency. Therefore, the display panel can perform variable frequency display and meet different display requirements.
Fig. 2 is a schematic structure of a pixel driving circuit according to an embodiment of the present disclosure. As shown in fig. 2, the pixel driving circuit provided in the embodiment of the present application includes: a driving transistor unit 210 for driving the light emitting device D, and an adjustable storage capacitor unit 220 including an adjustable capacitor unit 221.
The first terminal of the driving transistor unit 210 is connected to a first voltage source VDD, the second terminal thereof is connected to a first terminal of the light emitting device D, and the second terminal thereof is connected to a second voltage source VSS.
The adjustable capacitor unit 221 is connected to the control terminal of the driving transistor unit 210, and is configured to continuously adjust the stored capacitance value according to different refresh frequencies of the display panel to store a capacitance value corresponding to the refresh frequency.
For the pixel driving circuit shown in fig. 2, the operation principle is as follows: when the driving transistor unit 210 and the light emitting device D are connected in series between the first voltage source VDD and the second voltage source VSS, the driving transistor unit 210 is turned on and a path is formed between the first voltage source VDD and the second voltage source VSS, the light emitting device D emits light, and when the driving transistor unit 210 is in an off state, the light emitting device D does not emit light. The display panel has different refresh frequencies, the light emitting device D emits light at different time intervals, and the light emitting device D emits light at each time interval in a negative correlation with the refresh frequency. Therefore, when the refresh frequency of the display panel is in a low frequency state, the light emitting device D emits light for a long time each time, which requires that the driving transistor unit 210 be turned on for a long time. The turn-on of the driving transistor unit 210 is controlled by the voltage at the control terminal thereof, and when the voltage at the control terminal of the driving transistor unit 210 is not enough to maintain the turn-on, the driving transistor unit 210 is turned off, and the light emitting device D stops emitting light. Therefore, it is necessary to maintain the voltage at the control terminal of the driving transistor unit 210 stable, and to turn on the driving transistor unit 210 to make the light emitting device D emit light.
For the circuit shown in fig. 2, the control terminal of the driving transistor unit 210 is connected to an adjustable storage capacitor unit 220, which includes an adjustable capacitor unit 221. The capacitance value stored in the adjustable capacitance unit 221 is related to the refresh frequency of the display panel, that is, the capacitance value stored in the adjustable capacitance unit 221 may change with the change of the refresh frequency of the display panel, and the capacitance value stored in the adjustable capacitance unit 221 and the refresh frequency of the display panel are in a negative correlation relationship. In this way, the problem that the light emitting duration of the light emitting device D is reduced due to the unstable control terminal voltage of the driving transistor unit 210 can be improved, thereby satisfying the requirement of the refresh frequency of the display panel. For example, when the refresh frequency is 60Hz, the capacitance value stored in the adjustable capacitor unit 221 corresponds to 60Hz, which can maintain the stability of the control terminal voltage of the driving transistor unit 210 when the refresh frequency is 60 Hz; when the refresh frequency is 50Hz, the capacitance value stored in the adjustable capacitor unit 221 corresponds to 50Hz, which can maintain the stability of the control terminal voltage of the driving transistor unit 210 when the refresh frequency is 50 Hz; when the refresh frequency is 80Hz, the capacitance value stored in the adjustable capacitor unit 221 corresponds to 80Hz, which can maintain the stability of the control terminal voltage of the driving transistor unit 210 when the refresh frequency is 80 Hz.
In this embodiment, in the pixel driving circuit, the control terminal of the driving transistor unit is connected to an adjustable storage capacitor unit including an adjustable capacitor unit, and the adjustable capacitor unit can continuously adjust the stored capacitance value according to different refresh frequencies of the display panel to store the capacitance value corresponding to the refresh frequency. Therefore, when the refresh frequency of the display panel changes, the adjustable capacitor unit adjusts the stored capacitance value, so that the duration of the conduction of the driving transistor unit maintained by the voltage of the control end of the driving transistor unit meets the requirement of the refresh frequency, and the variable frequency display of the display panel is realized, thereby meeting the requirements of different display image qualities and improving the user experience.
Fig. 3 is a schematic structure of a pixel driving circuit according to another embodiment of the present disclosure. As shown in fig. 3, based on the embodiment shown in fig. 2, the tunable storage capacitor unit 220 further includes: a fixed capacitor unit 222. The fixed capacitor unit 222 is connected between the first voltage source VDD and the control terminal of the driving transistor unit 210, and is used for storing a fixed capacitance value.
For the pixel driving circuit shown in fig. 3, the operation principle is as follows: the fixed capacitor unit 222 is added to the pixel circuit, so that when the refresh frequency of the display panel is high frequency, the fixed capacitor unit 222 stores a capacitor with a smaller capacitance value, and the driving transistor unit 210 does not need to be kept on for a long time. At this time, the capacitance value stored in the fixed capacitor unit 222 is maintained to be stable at the control terminal voltage of the driving transistor unit 210 without the capacitance value stored in the tunable capacitor unit 221. When the refresh frequency of the display panel is low, the driving transistor unit 210 needs to be turned on for a long time. At this time, the capacitance values stored in the adjustable capacitor unit 221 and the fixed capacitor unit 222 are used to maintain the voltage at the control terminal of the driving transistor unit 210 stable. Thus, the stability of the control terminal voltage of the driving transistor unit 210 is improved when the refresh frequency of the display panel is low.
It should be noted that the refresh frequency of the display panel is relatively high frequency or low frequency, the high frequency may be a specific value or a frequency range, and similarly, the low frequency may be a specific value or a frequency range, which is not limited in this application.
In some embodiments, as shown in fig. 3, the adjustable capacitor unit 221 includes a switching device 221s, a source and a drain of the switching device 221s are respectively connected to the control terminal of the driving transistor unit 210, and the control terminal of the switching device 221s is connected to the common voltage COM of the display panel.
Specifically, the voltage of the common voltage COM of the display panel is related to the refresh frequency of the display panel, and the capacitance value stored in the switching device 221s is related to the voltage of the common voltage COM, so that when the refresh frequency of the display panel is changed, the capacitance value stored in the switching device 221s is changed accordingly.
Fig. 4 is a schematic structure of a pixel driving circuit according to another embodiment of the present application. As shown in fig. 4, on the basis of any of the above embodiments, the pixel driving circuit further includes: the compensation transistor unit 230. The control terminal of the compensation transistor unit 230 is connected to the Gate line Gate, the first terminal is connected to the control terminal of the driving transistor unit 210, and the second terminal of the compensation transistor unit 230 is connected to the second terminal of the driving transistor unit 210, so as to control the connection between the control terminal of the driving transistor unit 210 and the second terminal of the driving transistor unit 210 under the control of the driving signal provided by the Gate line Gate.
In some embodiments, continuing to fig. 4, the pixel drive circuit further comprises: the transistor unit 240 is reset. The control terminal of the Reset transistor unit 240 is connected to the Reset control terminal Reset, the first output terminal is connected to the control terminal of the driving transistor unit 210, and the second output terminal of the Reset transistor unit 240 is connected to the first terminal of the light emitting device D, so as to control writing of the initial voltage into the control terminal of the driving transistor unit 210 and the first terminal of the light emitting device D under the control of the Reset control signal provided by the control terminal.
In some embodiments, continuing to fig. 4, the pixel drive circuit further comprises: data is written to the transistor cells 250. The control end of the Data writing transistor unit 250 is connected to the Gate line Gate, the first end is connected to the Data line Data, and the second end is connected to the first end of the driving transistor unit 210, so as to provide the Data voltage on the Data line Data to the first end of the driving transistor unit 210 under the control of the driving signal provided by the Gate line Gate.
In some embodiments, continuing to fig. 4, the pixel drive circuit further comprises: a first light emission control transistor unit 260 and a second light emission control transistor unit 270.
The control end of the first light emitting control transistor unit 260 is connected to the light emitting control line EM, the first end is connected to the first voltage source VDD, and the second end is connected to the first end of the driving transistor unit 210, for controlling the connection between the first voltage source VDD and the first end of the driving transistor unit 210 under the control of the light emitting control signal provided by the light emitting control line EM.
The second emission control transistor unit 270 has a control terminal connected to the emission control line EM, a first terminal connected to the second terminal of the driving transistor unit 210, and a second terminal connected to the first terminal of the light emitting device D, and is configured to control the connection between the second terminal of the driving transistor unit 210 and the first terminal of the light emitting device D under the control of an emission control signal provided by the emission control line EM.
The following describes the embodiments of the present application with reference to a specific example.
Fig. 5 is a schematic structure of a pixel driving circuit according to another embodiment of the present application. As shown in fig. 5, the driving Transistor unit 210 includes a P-type Thin Film Transistor (TFT), which is denoted as a driving Transistor T1; the compensation transistor unit 230 includes a P-type TFT denoted as a compensation transistor T2; the data writing transistor unit 250 includes a P-type TFT denoted as a data writing transistor T3; the reset transistor unit 240 includes two P-type TFTs, denoted as a first reset transistor T4 and a second reset transistor T7; the first and second light emission controlling transistor units 260 and 270 respectively include a P-type TFT, which is denoted as a first light emission controlling transistor T5 and a second light emission controlling transistor T6; the fixed capacitance is Cst; the switching device 221s is a P-type thin film transistor TFT, denoted as a switching transistor Tc.
As shown in fig. 5, the connection relationship of the pixel driving circuit is:
the gate of the first light emission controlling transistor T5 is connected to the light emission control line EM, the source of the first light emission controlling transistor T5 is connected to the first voltage source VDD, and the drain of the first light emission controlling transistor T5 is electrically connected to the source of the driving transistor T1.
A gate of the second light emission controlling transistor T6 is connected to the light emission control line EM, a source of the second light emission controlling transistor T6 is connected to the drain of the driving transistor T1, and a drain of the second light emission controlling transistor T6 is connected to the anode of the light emitting device D; the Light Emitting device D may be an Organic Light-Emitting Diode (OLED), for example.
The Gate of the Data writing transistor T3 is connected to the Gate line Gate, the source of the Data writing transistor T3 is connected to the Data line Data, and the drain of the Data writing transistor T3 is connected to the source of the driving transistor T1; the Data lines Data are used for supplying Data voltages.
A first terminal of the storage capacitor Cst is connected to the gate of the driving transistor T1, and a second terminal of the storage capacitor Cst is connected to the first voltage source VDD.
The Gate of the compensation control transistor T2 is connected to the Gate line Gate, the drain of the compensation control transistor T2 is connected to the Gate of the driving transistor T1, and the source of the compensation control transistor T2 is connected to the drain of the driving transistor T1.
The gate of the first Reset transistor T4 is connected to the Reset control terminal Reset, the source of the first Reset transistor T4 is connected to the initial voltage Vref, and the drain of the first Reset transistor T4 is connected to the gate of the driving transistor T1.
The gate of the second Reset transistor T7 is connected to the Reset control terminal Reset, the source of the second Reset transistor T7 is connected to the initial voltage Vref, and the drain of the second Reset transistor T7 is connected to the anode of the light emitting device D.
The switching transistor Tc has a gate connected to the common voltage COM, and has a source and a drain both connected to the gate of the driving transistor T1.
For the pixel driving circuit shown in fig. 5, the working principle corresponding to different refresh frequencies is as follows:
the switch transistor Tc is a silicon-based p-type thin film transistor, when the grid electrode of the switch transistor Tc is at low voltage, an inversion layer is formed on the surface of an active layer p-Si of the switch transistor Tc, the active layer p-Si can be regarded as an electrode plate, and a parallel plate capacitor Ctft is formed between the active layer p-Si and the control end; when the gate of the switching transistor Tc is at a high voltage, the active layer p-Si of the switching transistor Tc is an intrinsic semiconductor layer, the active layer p-Si can be regarded as a dielectric layer, and the active layer p-Si and the control terminal cannot form a capacitor. And the size of the capacitance Ctft formed by the active layer p-Si and the grid electrode is in negative correlation with the grid voltage, namely the smaller the grid voltage is, the larger the capacitance is.
Therefore, the embodiment of the present application uses the switching transistor Tc as a storage capacitor at a low frequency.
The gate of the switching transistor Tc is electrically connected to the common voltage COM, and when the display panel operates in a high frequency band, the common voltage COM is a high voltage signal Vgh, and at this time, the switching transistor Tc is turned off, and the switching transistor Tc cannot store a capacitance. Therefore, when the display panel operates in a high frequency band, only the fixed capacitor Cst is provided, and thus, the storage capacitor corresponding to the gate of the driving transistor T1 is small, which satisfies the requirement for a capacitor at a high frequency.
When the display panel works at a low frequency band, the common voltage COM is a low voltage signal Vgl, the switching transistor Tc is turned on, and the active layer p-Si of the switching transistor Tc and the gate form a parallel plate capacitor Ctft, at this time, the storage capacitor corresponding to the gate of the driving transistor T1 is the sum of Ctft and Cst, that is, the storage capacitor corresponding to the gate of the driving transistor T1 is large, so that the requirement of the capacitor at the low frequency can be met. And, the lower the operating frequency of the display panel, the larger the parallel plate capacitance Ctft.
Fig. 6 is a driving timing diagram corresponding to the pixel driving circuit structure shown in fig. 5. As shown in fig. 6, the common voltage COM is under the voltage condition corresponding to different refresh frequencies according to the requirement of the display frequency.
The driving timing includes three stages, in the first stage (Reset stage), the Reset control signal provided by the Reset control terminal Reset jumps from a high potential to a low potential, the first Reset transistor T4 and the second Reset transistor T7 are turned on, the driving transistor T1, the compensation transistor T2, the data writing transistor T3, the first emission control transistor T5, the second emission control transistor T6, and the switching transistor Tc are turned off, the initial voltage Vref is written in the anode of the light emitting device D and the gate of the driving transistor T1, the voltages at the anode of the light emitting device D and the gate of the driving transistor T1 are Reset, and the driving transistor T1 is turned off.
In the second phase (compensation phase), the first reset transistor T4, the second reset transistor T7, the first light-emitting control transistor T5 and the second light-emitting control transistor T6 are turned off, the Gate line voltage provided by the Gate line Gate jumps from a high potential to a low potential, at this time, the compensation transistor T2 and the Data write transistor T3 are turned on, the Data voltage is input to the source of the driving transistor T1, the voltage difference between the Gate and the source of the driving transistor T1 turns on the driving transistor T1 to charge the fixed capacitor Cst, and at the same time, if the voltage difference between the Gate and the source of the switching transistor Tc can turn on the switching transistor Tc, the switching transistor Tc is turned on and charged until the driving transistor T1 is turned off.
In the third phase (light-emitting phase), the first reset transistor T4, the second reset transistor T7, the compensation transistor T2 and the data write transistor T3 are turned off, the voltage of the light-emitting control line EM jumps from a high potential to a low potential, and at this time, the first light-emitting control transistor T5 and the second light-emitting control transistor T6 are turned on, so that the source voltage of the driving transistor T1 changes, the driving transistor T1 is turned back on, the current supplied from the voltage source VDD flows through the light-emitting device D through the first light-emitting control transistor T5, the driving transistor T1 and the second light-emitting control transistor T6, and the light-emitting device D emits light. If the refresh frequency of the display panel is high frequency, the voltage of the gate of the driving transistor T1 is maintained by the capacitor stored in the fixed capacitor Cst; if the refresh frequency of the display panel is low, the voltage of the gate of the driving transistor T1 is commonly maintained by the fixed capacitor Cst and the capacitor stored by the switching transistor Tc, so that the gate voltage of the driving transistor T1 can be kept stable for a long time, and the driving transistor T1 is turned on for a long time, so that the light emitting device D can stably emit light.
Note that, in the pixel driver circuit of the present application, some or all of the elements may be replaced with another element or a combination of a plurality of elements as long as the function of the element can be achieved.
Fig. 7 is a schematic structural diagram of a display panel according to an embodiment of the present application, where the display panel includes a pixel driving circuit according to any embodiment of the present application. The pixel driving circuit includes a Gate line voltage input terminal Gate and a Data voltage input terminal Data. The display panel further includes: a scan driving circuit 710, a data driving circuit 720, a plurality of scan lines (S1, S2, S3, S4 … …), and a plurality of data lines (D1, D2, D3, D4 … …). The port of the scan driving circuit 710 is electrically connected to a plurality of scan lines, the Gate line voltage input terminal Gate of the pixel driving circuit 720 is electrically connected to one scan line, and the Data voltage input terminal of the pixel driving circuit is electrically connected to one Data line.
It should be noted that the Data voltage input terminal Data and the Gate line voltage input terminal Gate of the pixel circuit for driving one sub-pixel are only schematically shown in the figure, and the ports of the pixel circuits for driving the other sub-pixels are similar to the sub-pixel and are not shown one by one here.
The display panel provided by the embodiment of the application has the same beneficial effects as the pixel driving circuit provided by any embodiment of the application.
Fig. 8 is a schematic structural diagram of a terminal Device according to an embodiment of the present disclosure, as shown in fig. 8, the terminal Device may include, but is not limited to, a mobile terminal such as a mobile phone, a notebook computer, a digital broadcast receiver, a Personal Digital Assistant (PDA), a tablet computer (PAD), a Portable Multimedia Player (PMP), a vehicle-mounted terminal (e.g., a car navigation terminal), and a fixed terminal such as a digital TV, a desktop computer, and the like. The terminal device shown in fig. 8 is only an example, and should not bring any limitation to the functions and the scope of use of the embodiments of the present disclosure.
As shown in fig. 8, the terminal device may include a processing means (e.g., a central processing unit, a graphics processor, etc.) 801 which can perform various appropriate actions and processes according to a program stored in a Read Only Memory (ROM) 802 or a program loaded from a storage means 808 into a Random Access Memory (RAM) 803. In the RAM803, various programs and data necessary for the operation of the terminal device are also stored. The processing apparatus 801, the ROM802, and the RAM803 are connected to each other by a bus 804. An input/output (I/O) interface 805 is also connected to bus 804.
Generally, the following devices may be connected to the I/O interface 805: input devices 806 including, for example, a touch screen, touch pad, keyboard, mouse, camera, microphone, accelerometer, gyroscope, etc.; a Display panel 807 including, for example, a Liquid Crystal Display (LCD), an Organic Light Emitting Display (OLED), and the like; storage 808 including, for example, magnetic tape, hard disk, etc.; and a communication device 809. The communication means 809 may allow the terminal device to perform wireless or wired communication with other devices to exchange data.
For the present application, the RAM803 stores the corresponding relationship between the different refresh frequencies of the display panel 807 and the common voltage COM, and when the refresh frequency of the display panel 807 of the terminal device changes, the processing device 801 acquires the corresponding relationship between the refresh frequency stored in the RAM803 and the common voltage COM according to the refresh frequency of the current display panel 807, and obtains the value of the common voltage COM, thereby enabling the display panel 807 to implement variable frequency display.
It should be noted that although fig. 8 shows a terminal device having various means, it is to be understood that not all of the means shown are required to be implemented or provided. More or fewer devices may alternatively be implemented or provided.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.
Claims (10)
1. A pixel driving circuit, comprising:
a driving transistor unit driving a light emitting device, a first end of the driving transistor unit being connected to a first voltage source, a second end of the driving transistor unit being connected to a first end of the light emitting device, and a second end of the light emitting device being connected to a second voltage source;
the adjustable storage capacitor unit comprises an adjustable capacitor unit, wherein the adjustable capacitor unit is connected to the control end of the driving transistor unit so as to adjust the capacitance value stored by the adjustable capacitor unit according to different refreshing frequencies of the display panel.
2. The circuit of claim 1, wherein the tunable storage capacitor unit further comprises: a fixed capacitor unit;
the fixed capacitor unit is respectively connected to the first voltage source and the control end of the driving transistor unit, and is used for storing a fixed capacitance value.
3. The circuit of claim 1, wherein the adjustable capacitance unit comprises: and the source electrode and the drain electrode of the switching device are respectively connected with the control end of the driving transistor unit, and the control end of the switching device is connected with the common voltage of the display panel.
4. The circuit of claim 3, wherein the switching device comprises a P-type thin film transistor, and/or wherein the driving transistor unit comprises a P-type thin film transistor.
5. The circuit of any of claims 1-4, further comprising:
and the first end of the compensation transistor unit is connected with the control end of the driving transistor unit, and the second end of the compensation transistor unit is connected with the second end of the driving transistor unit and used for controlling the communication between the control end of the driving transistor unit and the second end of the driving transistor unit.
6. The circuit of claim 5, further comprising:
and the first output end of the reset transistor unit is connected with the control end of the driving transistor unit, and the second output end of the reset transistor unit is connected with the first end of the light-emitting device and used for controlling the writing of initial voltage into the control end of the driving transistor unit and the first end of the light-emitting device.
7. The circuit of claim 6, further comprising: a data write transistor unit;
the first end of the data writing transistor unit is connected with a data line, and the second end of the data writing transistor unit is connected with the first end of the driving transistor unit and used for providing data voltage on the data line to the first end of the driving transistor unit.
8. The circuit of claim 7, further comprising: a first light emission control transistor unit and a second light emission control transistor unit;
the first end of the first light-emitting control transistor unit is connected with the first voltage source, the second end of the first light-emitting control transistor unit is connected with the first end of the driving transistor unit, and the first end of the first light-emitting control transistor unit is used for controlling the connection between the first voltage source and the first end of the driving transistor unit;
the first end of the second light-emitting control transistor unit is connected with the second end of the driving transistor unit, and the second end of the second light-emitting control transistor unit is connected with the first end of the light-emitting device and used for controlling the communication between the second end of the driving transistor unit and the first end of the light-emitting device.
9. A display panel comprising the pixel drive circuit according to any one of claims 1 to 8.
10. A terminal device characterized by comprising processing means, storage means, and the display panel of claim 9.
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| CN202010293027.XA CN111341245B (en) | 2020-04-15 | 2020-04-15 | Pixel driving circuit, display panel and terminal equipment |
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| CN202010293027.XA CN111341245B (en) | 2020-04-15 | 2020-04-15 | Pixel driving circuit, display panel and terminal equipment |
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