CN113658554A - Pixel driving circuit, pixel driving method and display device - Google Patents

Pixel driving circuit, pixel driving method and display device Download PDF

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Publication number
CN113658554A
CN113658554A CN202110942237.1A CN202110942237A CN113658554A CN 113658554 A CN113658554 A CN 113658554A CN 202110942237 A CN202110942237 A CN 202110942237A CN 113658554 A CN113658554 A CN 113658554A
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transistor
node
voltage
control signal
pixel driving
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CN113658554B (en
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卢奕宏
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Shenzhen China Star Optoelectronics Semiconductor Display Technology Co Ltd
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Shenzhen China Star Optoelectronics Semiconductor Display Technology Co Ltd
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • 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
    • 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
    • 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
    • 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)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Control Of El Displays (AREA)
  • Electroluminescent Light Sources (AREA)

Abstract

The embodiment of the application provides a pixel driving circuit, a pixel driving method and a display device. The current scanning signal, the secondary scanning signal, the first control signal and the second control signal are sequentially applied to different transistors, and finally the current flowing through the light-emitting element is independent of the threshold voltage of the second transistor. The change of the drive current caused by the drift of the threshold voltage is avoided, the problem of uneven brightness of the display panel is solved, and the display image quality is improved.

Description

Pixel driving circuit, pixel driving method and display device
Technical Field
The present application relates to the field of electronic devices, and in particular, to a pixel driving circuit, a pixel driving method, and a display device.
Background
Compared with the conventional LCD (Liquid Crystal Display), the AMOLED (Active-matrix organic light-emitting diode) has higher contrast, faster response speed and wider viewing angle as a new generation of Display technology, is widely applied to the field of smart phones, and is continuously developed and expanded to the field of smart televisions and wearable devices.
The AMOLED display panel is internally provided with a plurality of pixels which are arranged in an array mode, and each pixel is driven by a pixel driving circuit. However, during use, the value of the threshold voltage may drift, which may cause a change in the driving current, and finally cause luminance unevenness of the AMOLED display panel, resulting in poor display and affecting image quality.
Disclosure of Invention
The embodiment of the application provides a pixel driving circuit, a pixel driving method and a display device, which can eliminate the influence of threshold voltage on current flowing through a light-emitting element, thereby improving the uniformity of display.
In a first aspect, an embodiment of the present application provides a pixel driving circuit, including a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, a storage capacitor, a light emitting element, a power supply, a first node, a second node, a third node, and a fourth node;
a grid electrode of the first transistor is connected with a current scanning signal, a source electrode of the first transistor is electrically connected with the first node, and a drain electrode of the first transistor is connected with a current data signal;
the grid electrode of the second transistor is electrically connected with the second node, the source electrode of the second transistor is electrically connected with the fourth node, and the drain electrode of the second transistor is electrically connected with the third node;
a grid electrode of the third transistor is connected with a current scanning signal, a source electrode of the third transistor is electrically connected with the third node, and a drain electrode of the third transistor is electrically connected with the second node;
the grid electrode of the fourth transistor is connected with a first control signal, the source electrode of the fourth transistor is electrically connected with the third node, and the drain electrode of the fourth transistor is electrically connected with the positive electrode of the power supply;
a grid electrode of the fifth transistor is connected with a secondary scanning signal, a source electrode of the fifth transistor is electrically connected with the fourth node, and a drain electrode of the fifth transistor is connected with a reference voltage;
a gate of the sixth transistor is connected to a second control signal, a source of the sixth transistor is electrically connected to an anode of the light emitting element, and a drain of the sixth transistor is electrically connected to the fourth node;
a grid electrode of the seventh transistor is connected with a second control signal, a source electrode of the seventh transistor is connected with a reference voltage, and a drain electrode of the seventh transistor is electrically connected with the first node;
the cathode of the light-emitting element is electrically connected with the cathode of the power supply;
the upper pole plate of the storage capacitor is electrically connected with the first node, and the lower pole plate of the storage capacitor is electrically connected with the second node.
In a second aspect, an embodiment of the present application provides a pixel driving method for a pixel driving circuit as described above, including:
controlling the pixel driving circuit to enter the initialization stage, so that the voltage of the first node is equal to the data voltage, and the voltage of the second node is equal to the positive voltage of the power supply;
controlling the pixel driving circuit to enter the threshold voltage compensation phase, so that the voltage of a first node is equal to the data voltage, and the voltage of a second node is equal to the sum of the reference voltage and the threshold voltage of the second transistor;
controlling the pixel driving circuit to enter the data writing phase, so that the voltage of the first node is equal to a reference voltage, and the voltage of the second node is equal to the sum of twice the reference voltage and the threshold voltage of the second transistor minus a data voltage;
and controlling the pixel driving circuit to enter the light-emitting stage, wherein the voltage of the first node is equal to the reference voltage.
In a third aspect, embodiments of the present application provide a display device including the pixel driving circuit as described above.
In an embodiment of the present invention, the second transistor is a driving transistor of a light emitting element, a gate of the second transistor is electrically connected to the second node, a source of the second transistor is electrically connected to the fourth node, and a drain of the second transistor is electrically connected to the third node. When the light emitting element emits light, the gate voltage of the second transistor is equal to the sum of twice the reference voltage and the threshold voltage of the second transistor minus the data voltage, and the source voltage of the second transistor is equal to the negative voltage of the power supply, i.e., the current I ═ k (2 × reference voltage-data voltage-negative voltage of the power supply) flowing through the light emitting element2. Threshold of second transistor eliminatedThe influence of the voltage on the current flowing through the light emitting element improves the uniformity of display.
Drawings
The technical solutions and advantages of the present application will become apparent from the following detailed description of specific embodiments of the present application when taken in conjunction with the accompanying drawings.
Fig. 1 is a schematic diagram of a pixel driving circuit in the related art.
Fig. 2 is a schematic structural diagram of a display device according to an embodiment of the present disclosure.
Fig. 3 is a schematic diagram of a pixel driving circuit according to an embodiment of the present disclosure.
Fig. 4 is a schematic diagram of a pixel driving circuit in an initialization stage according to an embodiment of the present disclosure.
Fig. 5 is a schematic diagram of a pixel driving circuit in a threshold voltage compensation phase according to an embodiment of the present disclosure.
Fig. 6 is a schematic diagram of a pixel driving circuit in a data writing stage according to an embodiment of the present disclosure.
Fig. 7 is a schematic diagram of a pixel driving circuit in a light-emitting stage according to an embodiment of the present disclosure.
Fig. 8 is a schematic diagram of a current control signal, a previous stage control signal, a first control signal, and a second control signal of a pixel driving circuit in an operating period according to an embodiment of the present invention.
Fig. 9 is a flowchart of a pixel driving method provided in an embodiment of the present application.
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. It is to be understood that the embodiments described are only a few embodiments of the present application and 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.
Organic Light Emitting Diode (OLED) Display panels have many advantages such as self-luminescence, low driving voltage, high luminous efficiency, short response time, high definition and contrast, wide viewing angle, wide temperature range, flexible Display, and large-area full color Display, and are considered as Display devices with the most potential for development. OLEDs can be classified into two major categories, namely, direct addressing and thin film transistor Matrix addressing, namely, Passive Matrix OLEDs (PMs) and Active Matrix OLEDs (AMs) according to driving methods. The AMOLED comprises a plurality of pixel units which are arranged in an array mode, the display pixels are controlled by scanning lines (gate) and data lines (data), the scanning lines receive grid control signals to control the opening and closing of the display pixels, and the data lines apply different data signals to the display pixels to enable the display pixels to display different gray scales, so that full-color picture display is achieved.
Each pixel unit includes a light emitting device and a pixel driving circuit for driving the light emitting device, referring to fig. 1, fig. 1 is a schematic diagram of the pixel driving circuit in the related art. The conventional AMOLED pixel driving circuit has a 2TLC structure, and includes a switching transistor T8, a driving transistor T9, and a capacitor C. The switching transistor T8 and the driving transistor T9 may control the light emitting device, the capacitor may store data, the driving current of the organic light emitting diode OLED is controlled by the driving transistor T9, and the calculation formula of the driving current is IOLED＝k(Vgs-Vth)2Wherein, IOLEDIs the drive current; k is a current amplification factor of the driving transistor T9, and is determined by the electrical characteristics of the driving transistor T9 itself; vgs is the voltage difference between the gate and source of the driving transistor T9, and Vth is the threshold voltage of the driving transistor T9. It can be seen that the drive current IOLEDIs related to the threshold voltage Vth of the driving transistor T9. However, as the device ages or changes in temperature, the threshold voltage Vth of the drive transistor may shift, resulting in the drive current IOLEDThe variation causes the brightness of the AMOLED display panel to be uneven, the display is poor and the like, and the display image quality is influenced.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a display device according to an embodiment of the present disclosure. The display device 100 may be any product or component with a display function, such as a mobile phone, a tablet computer, a television, a monitor, a notebook computer, a digital photo frame, a navigator, etc., and is not limited herein. The display device 100 includes a display driving module, which includes a plurality of pixel units, a plurality of rows of data lines, a data driver, and a plurality of rows of scan lines. The pixel units are arranged in an array, and each pixel unit is electrically connected to the corresponding data line in the row. The data driver is electrically connected to the plurality of data lines and outputs data signals to the pixel units through the data lines. The plurality of rows of scan lines are used for receiving scan signals S (e.g., S1, S2, S3 … … Sn, Sn +1), and each pixel unit is electrically connected to the corresponding scan line in the corresponding row. It should be noted that the pixel unit generally includes a red sub-pixel, a green sub-pixel, and a blue sub-pixel, i.e., an RGB three-color sub-pixel structure. In order to increase the transmittance, a white sub-pixel, namely an RGBW four-color sub-pixel structure can also be added. The number and the arrangement mode of each sub-pixel are set according to specific requirements, and for example, the sub-pixels can be arranged in a diamond type, a small yellow duck type and the like, which is not limited herein.
Each pixel unit includes a light emitting device OLED and a pixel driving circuit 1, please refer to fig. 3, and fig. 3 is a schematic diagram of a pixel driving circuit according to an embodiment of the present disclosure. The embodiment of the present application provides a pixel driving circuit 1, which includes a first transistor T1, a second transistor T2, a third transistor T3, a fourth transistor T4, a fifth transistor T5, a sixth transistor T6, a seventh transistor T7, a storage capacitor Cst, a power supply, a first node N1, a second node N2, a third node N3, and a fourth node N4, that is, the pixel driving circuit 1 in the embodiment of the present application is a 7T1C structure. Compared to the conventional 2T1C driving circuit, the first transistor T1 in the embodiment of the present application may be regarded as a switching transistor, and the second transistor T2 may be regarded as a driving transistor. The storage capacitor Cst is used for storing data, and the first transistor T1 and the second transistor T2 cooperate with each other to maintain a stable current flowing through the light emitting element OLED, so as to maintain the normal light emission of the light emitting element OLED.
The grid electrode of the first transistor T1 is connected to the current scanning signal Sn, the source electrode is electrically connected with the first node N1, and the drain electrode is connected to the current data signal;
a gate of the second transistor T2 is electrically connected to the second node N2, a source is electrically connected to the fourth node N4, and a drain is electrically connected to the third node N3;
a gate of the third transistor T3 is connected to the current scan signal Sn, a source thereof is electrically connected to the third node N3, and a drain thereof is electrically connected to the second node N2;
the grid electrode of the fourth transistor T4 is connected with the first control signal En, the source electrode is electrically connected with the third node N3, and the drain electrode is electrically connected with the positive electrode of the power supply;
a gate of the fifth transistor T5 is connected to the secondary scan signal Sn-1, a source thereof is electrically connected to the fourth node N4, and a drain thereof is connected to a reference voltage Vref；
A gate of the sixth transistor T6 is connected to the second control signal En-1, a source thereof is electrically connected to an anode of the light emitting element OLED, and a drain thereof is electrically connected to the fourth node N4;
the gate of the seventh transistor T7 is connected to the second control signal En-1, and the source is connected to the reference voltage VrefThe drain is electrically connected with a first node N1;
the cathode of the light-emitting element OLED is electrically connected with the cathode of the power supply;
an upper plate of the storage capacitor Cst is electrically connected to the first node N1, and a lower plate of the storage capacitor Cst is electrically connected to the second node N2;
it is understood that the first node N1 is electrically connected to the source electrode of the first transistor T1, the drain electrode of the seventh transistor T7, and the upper plate of the storage capacitor Cst at the same time; the second node N2 is electrically connected to the gate of the second transistor T2, the drain of the third transistor T3, and the bottom plate of the storage capacitor Cst; the third node N3 is electrically connected to the source of the third transistor T3, the source of the fourth transistor T4 and the drain of the second transistor T2; the fourth node N4 is electrically connected to the source of the second transistor T2, the source of the fifth transistor T5, and the drain of the sixth transistor T6 at the same time.
The operation cycle of the pixel driving circuit 1 includes an initialization phase a1, a threshold voltage compensation phase a2, a data writing phase A3, and a light emission phase a 4.
It should be noted that the currents flowing through the different light emitting elements OLED are different, and different colors are displayed, so as to form a complete display screen. Therefore, the temperature of the molten metal is controlled,when one frame is displayed, the second transistor T2 electrically connected to each light emitting element OLED is in a different state. For convenience of control and management, before the current picture is displayed, the state of the second transistor T2 needs to be restored, that is, the pixel driving circuit 1 needs to be initialized. In the initialization phase A1, the voltage at the first node N1 is equal to the data voltage (V)N1＝VData) The voltage of the second node N2 is equal to the positive voltage (V) of the power supplyN2＝VDD)。
During the threshold voltage compensation phase A2, the voltage at the first node N1 is equal to the data voltage (V)N1＝VData) The voltage at the second node N2 is equal to the reference voltage VrefAnd the sum (V) of the threshold voltages of the second transistor T2N2＝Vref+Vth)。
During the data writing phase A3, the voltage of the first node N1 is equal to the reference voltage Vref(VN1＝Vref) The voltage of the second node N2 is equal to the reference voltage VrefIs subtracted by the data voltage (V) from the sum of twice the threshold voltage of the second transistor T2N2＝2Vref-VData+Vth)。
During the light-emitting period A4, the voltage of the first node N1 is equal to the reference voltage Vref(VN1＝Vref)。
When the light emitting element OLED emits light, the gate voltage Vg of the second transistor T2 is equal to the voltage of the second node N2, that is, Vg is 2Vref-VData+ Vth. The source voltage Vs of the second transistor T2 is equal to the negative voltage of the power supply, i.e., Vs equals VSS, and Vgs equals Vg — Vs equals 2Vref-VData+ Vth-VSS. I.e. the current I ═ k (Vgs-Vth) through the light-emitting element OLED2＝(2Vref-VData-VSS)2As can be seen from this, the current flowing through the light emitting element OLED is independent of the threshold voltage of the second transistor T2. The pixel driving circuit 1 according to the embodiment of the present application eliminates the influence of the threshold voltage of the second transistor T2 on the current flowing through the light emitting element OLED, thereby improving the uniformity of display.
For example, referring to fig. 4, fig. 4 is a schematic diagram of a pixel driving circuit in an initialization stage according to an embodiment of the present disclosure. In the initialization phaseA1, the fifth transistor T5, the sixth transistor T6 and the seventh transistor T7 are turned off, and the first transistor T1, the third transistor T3 and the fourth transistor T4 are turned on. At this time, the first transistor T1 is turned on and the seventh transistor T7 is turned off such that the voltage of the first node N1 is equal to the data voltage VN1＝VData(ii) a The third transistor T3 and the fourth transistor T4 are turned on to make the voltage of the second node N2 equal to the positive voltage V of the power supplyN2＝VDD。
Referring to fig. 5, fig. 5 is a schematic diagram of a pixel driving circuit in a threshold voltage compensation stage according to an embodiment of the present disclosure. In the threshold voltage compensation phase a2, the diode form discharges to complete the capture of the threshold voltage of the second transistor T2. The fourth, sixth, and seventh transistors T4, T6, and T7 are turned off, and the first, third, and fifth transistors T1, T3, and T5 are turned on. At this time, the first transistor T1 is turned on and the seventh transistor T7 is turned off such that the voltage of the first node N1 is equal to the data voltage VN1＝VData(ii) a The fifth transistor T5 is turned on to access the reference voltage VrefSo that the voltage at the third node N3 is the reference voltage VrefAnd, in addition, VDD-Vref>Vth, thereby causing the second transistor T2 to be turned on, and finally causing the potential of the second node N2 to be stabilized at Vref+ Vth. It should be noted that the transistor-type discharge is controlled, so that the capture of the threshold voltage value Vth of the second transistor T2 is realized.
Referring to fig. 6, fig. 6 is a schematic diagram of a pixel driving circuit in a data writing stage according to an embodiment of the present disclosure. In the data writing phase a3, the first transistor T1, the third transistor T3, the fourth transistor T4, and the fifth transistor T5 are turned off, and the sixth transistor T6 and the seventh transistor T7 are turned on. The first transistor T1 is turned off and the seventh transistor T7 is turned on so that the potential of the first node N1 changes from the data voltage to the reference voltage Vref，VN1＝Vref. The storage capacitor Cst writes data through coupling, and the voltage at the second node N2 changes and finally stabilizes at VN2＝2Vref-VData+Vth。
Referring to fig. 7, fig. 7 shows a pixel driving circuit in a light-emitting stage according to an embodiment of the present inventionSchematic representation of (a). In the light emitting period a4, the first transistor T1, the third transistor T3, and the fifth transistor T5 are turned off, and the second transistor T2, the fourth transistor T4, the sixth transistor T6, and the seventh transistor T7 are turned on. The first transistor T1 is turned off and the seventh transistor T7 is turned on so that the potential of the first node N1 changes from the data voltage to the reference voltage Vref，VN1＝Vref. The fourth transistor T4, the second transistor T2, and the sixth transistor T6 are turned on, so that a current flows through the light emitting element OLED, and the light emitting element OLED emits light.
The first transistor T1, the second transistor T2, the third transistor T3, the fourth transistor T4, the fifth transistor T5, the sixth transistor T6, and the seventh transistor T7 are low temperature polysilicon thin film transistors, oxide semiconductor thin film transistors, or amorphous silicon thin film transistors, which is not limited herein.
Referring to fig. 8, fig. 8 is a schematic diagram illustrating a current control signal, a previous stage control signal, a first control signal and a second control signal of a pixel driving circuit in an operating cycle according to an embodiment of the present disclosure. In the initialization stage a1, the current scan signal Sn is at a high level, the first control signal En is at a high level, the secondary scan signal Sn-1 is at a low level, and the second control signal En-1 is at a low level;
in the threshold voltage compensation stage A2, the current scan signal Sn is at a high level, the first control signal En is at a low level, the secondary scan signal Sn-1 is at a low level, and the second control signal En-1 is at a low level and a high level;
in the data writing phase a3, the current control signal is at a low level, the first control signal En is at a low level, the secondary scan signal Sn-1 is at a low level, and the second control signal En-1 is at a high level;
in the lighting period A4, the current control signal is low, the first control signal En is high, the secondary scan signal Sn-1 is low, and the second control signal En-1 is high.
It should be noted that, in the data writing phase A3 and the light emitting phase a4, there is a hold phase a5, in the hold phase a5, the current scan signal Sn is at a low level, the first control signal En is at a low level, the secondary scan signal Sn-1 is at a low level, and the second control signal En-1 is at a low level, so that the voltage of each node is maintained at the level in the threshold voltage compensation phase a 2.
Referring to fig. 9, fig. 9 is a flowchart illustrating a pixel driving method according to an embodiment of the present disclosure. A pixel driving method, comprising:
101. controlling the pixel driving circuit to enter an initialization stage, so that the voltage of the first node is equal to the data voltage, and the voltage of the second node is equal to the positive voltage of the power supply;
102. controlling the pixel driving circuit to enter a threshold voltage compensation stage, so that the voltage of a first node is equal to the data voltage, and the voltage of a second node is equal to the sum of the reference voltage and the threshold voltage of the second transistor;
103. controlling the pixel driving circuit to enter a data writing stage, so that the voltage of the first node is equal to a reference voltage, and the voltage of the second node is equal to the sum of twice the reference voltage and the threshold voltage of the second transistor minus the data voltage;
104. and controlling the pixel driving circuit to enter a light-emitting stage, wherein the voltage of the first node is equal to the reference voltage.
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, the pixel driving method and the display device provided in the embodiments of the present application are described above, and specific examples are applied herein to explain the principles and embodiments of the present application, and the description of the embodiments above 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 (10)

1. A pixel driving circuit comprises a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, a storage capacitor, a light-emitting element, a power supply, a first node, a second node, a third node and a fourth node;
a grid electrode of the first transistor is connected with a current scanning signal, a source electrode of the first transistor is electrically connected with the first node, and a drain electrode of the first transistor is connected with a current data signal;
the grid electrode of the second transistor is electrically connected with the second node, the source electrode of the second transistor is electrically connected with the fourth node, and the drain electrode of the second transistor is electrically connected with the third node;
a grid electrode of the third transistor is connected with a current scanning signal, a source electrode of the third transistor is electrically connected with the third node, and a drain electrode of the third transistor is electrically connected with the second node;
the grid electrode of the fourth transistor is connected with a first control signal, the source electrode of the fourth transistor is electrically connected with the third node, and the drain electrode of the fourth transistor is electrically connected with the positive electrode of the power supply;
a grid electrode of the fifth transistor is connected with a secondary scanning signal, a source electrode of the fifth transistor is electrically connected with the fourth node, and a drain electrode of the fifth transistor is connected with a reference voltage;
a gate of the sixth transistor is connected to a second control signal, a source of the sixth transistor is electrically connected to an anode of the light emitting element, and a drain of the sixth transistor is electrically connected to the fourth node;
a grid electrode of the seventh transistor is connected with a second control signal, a source electrode of the seventh transistor is connected with a reference voltage, and a drain electrode of the seventh transistor is electrically connected with the first node;
the cathode of the light-emitting element is electrically connected with the cathode of the power supply;
the upper pole plate of the storage capacitor is electrically connected with the first node, and the lower pole plate of the storage capacitor is electrically connected with the second node.
2. The pixel driving circuit according to claim 1, wherein the operation cycle of the pixel driving circuit includes an initialization phase in which the voltage at the first node is equal to a data voltage, a voltage at the second node is equal to a positive voltage of the power supply, a threshold voltage compensation phase, a data writing phase, and a light emitting phase;
in the threshold voltage compensation phase, the first node voltage is equal to a data voltage, and the second node voltage is equal to the sum of a reference voltage and the threshold voltage of the second transistor;
in the data writing phase, the voltage of the first node is equal to a reference voltage, and the voltage of the second node is equal to the sum of twice the reference voltage and the threshold voltage of the second transistor minus a data voltage;
in the light emitting phase, the voltage of the first node is equal to a reference voltage.
3. The pixel driving circuit according to claim 2, wherein in the initialization phase, the fifth transistor, the sixth transistor, and the seventh transistor are turned off, and the first transistor, the third transistor, and the fourth transistor are turned on;
in the threshold voltage compensation phase, the fourth transistor, the sixth transistor and the seventh transistor are turned off, and the first transistor, the third transistor and the fifth transistor are turned on;
in the data writing phase, the first transistor, the third transistor, the fourth transistor and the fifth transistor are turned off, and the sixth transistor and the seventh transistor are turned on;
in the light emitting stage, the first transistor, the third transistor, and the fifth transistor are turned off, and the second transistor, the fourth transistor, the sixth transistor, and the seventh transistor are turned on.
4. The pixel driving circuit according to claim 3, wherein in the initialization phase, the current scan signal is at a high level, the first control signal is at a high level, the sub-scan signal is at a low level, and the second control signal is at a low level;
in the threshold voltage compensation stage, the current scanning signal is at a high level, the first control signal is at a low level, the secondary scanning signal is at a low level, and the second control signal is at a low level and a high level;
in the data writing stage, the current control signal is at a low level, the first control signal is at a low level, the secondary scanning signal is at a low level, and the second control signal is at a high level;
in the light emitting stage, the current control signal is at a low level, the first control signal is at a high level, the secondary scanning signal is at a low level, and the second control signal is at a high level.
5. The pixel driving circuit according to any one of claims 1 to 4, wherein the first transistor, the second transistor, the third transistor, the fourth transistor, the fifth transistor, the sixth transistor, and the seventh transistor are low-temperature polysilicon thin film transistors, oxide semiconductor thin film transistors, or amorphous silicon thin film transistors.
6. A pixel driving method for the pixel driving circuit according to any one of claims 1 to 5, comprising:
controlling the pixel driving circuit to enter the initialization stage, so that the voltage of the first node is equal to the data voltage, and the voltage of the second node is equal to the positive voltage of the power supply;
controlling the pixel driving circuit to enter the threshold voltage compensation phase, so that the voltage of a first node is equal to the data voltage, and the voltage of a second node is equal to the sum of the reference voltage and the threshold voltage of the second transistor;
controlling the pixel driving circuit to enter the data writing phase, so that the voltage of the first node is equal to a reference voltage, and the voltage of the second node is equal to the sum of twice the reference voltage and the threshold voltage of the second transistor minus a data voltage;
and controlling the pixel driving circuit to enter the light-emitting stage, wherein the voltage of the first node is equal to the reference voltage.
7. The pixel driving method according to claim 6,
in the initialization stage, the fifth transistor, the sixth transistor and the seventh transistor are turned off, and the first transistor, the third transistor and the fourth transistor are turned on;
in the threshold voltage compensation phase, the fourth transistor, the sixth transistor and the seventh transistor are turned off, and the first transistor, the third transistor and the fifth transistor are turned on;
in the data writing phase, the first transistor, the third transistor, the fourth transistor and the fifth transistor are turned off, and the sixth transistor and the seventh transistor are turned on;
in the light emitting stage, the first transistor, the third transistor, and the fifth transistor are turned off, and the second transistor, the fourth transistor, the sixth transistor, and the seventh transistor are turned on.
8. The pixel driving method according to claim 7, wherein in the initialization stage, the current scan signal is at a high level, the first control signal is at a high level, the sub-scan signal is at a low level, and the second control signal is at a low level;
in the threshold voltage compensation stage, the current scanning signal is at a high level, the first control signal is at a low level, the secondary scanning signal is at a high level, and the second control signal is at a low level;
in the data writing stage, the current control signal is at a low level, the first control signal is at a low level, the secondary scanning signal is at a low level, and the second control signal is at a high level;
in the light emitting stage, the current control signal is at a low level, the first control signal is at a high level, the secondary scanning signal is at a low level, and the second control signal is at a high level.
9. The pixel driving method according to any one of claims 6 to 8, wherein controlling the pixel driving circuit to enter the data writing phase comprises:
performing a grabbing operation on a threshold voltage of the second transistor.
10. A display device comprising the pixel drive circuit according to any one of claims 1 to 5.
CN202110942237.1A 2021-08-17 2021-08-17 Pixel driving circuit, pixel driving method and display device Active CN113658554B (en)

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