CN107731171B - Pixel circuit, control method thereof, display substrate and display device - Google Patents
Pixel circuit, control method thereof, display substrate and display device Download PDFInfo
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- CN107731171B CN107731171B CN201711228024.2A CN201711228024A CN107731171B CN 107731171 B CN107731171 B CN 107731171B CN 201711228024 A CN201711228024 A CN 201711228024A CN 107731171 B CN107731171 B CN 107731171B
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3266—Details of drivers for scan electrodes
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- 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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Abstract
The invention discloses a pixel circuit, which comprises a first transistor, a second transistor, a third transistor, a storage capacitor and a light-emitting element, wherein the first transistor is connected with the second transistor; the pixel circuit further comprises a compensation control unit which is respectively connected with the first pole of the first transistor and the sensing line; the compensation control unit is used for accessing a third scanning signal and completing external compensation and internal compensation of the pixel circuit in an auxiliary mode according to the third scanning signal. The invention also discloses a control method of the pixel circuit, a display substrate and a display device. The pixel circuit, the control method thereof, the display substrate and the display device provided by the invention can complete external compensation and internal compensation, and can well improve the display effect through the internal and external compensation.
Description
Technical Field
The present invention relates to the field of display technologies, and in particular, to a pixel circuit, a control method thereof, a display substrate, and a display device.
Background
An Organic Light Emitting Diode (OLED) display device is a display device that emits light by injecting and recombining carriers under the driving of an electric field by using an organic light emitting material, and has the advantages of self-luminescence, wide viewing angle, high contrast, low power consumption, high reaction speed, and the like.
There are two compensation methods commonly used for OLED display at present: internal compensation and external compensation.
However, in the process of implementing the present invention, the inventors of the present invention found that at least the following problems exist in the prior art:
the internal compensation is mainly to realize Vth (threshold voltage) compensation by adding a TFT (thin film transistor) and a signal line. The method has the advantages of simple process and high compensation speed, and has the defect that only Vth can be compensated.
The external compensation is mainly to compensate the TFT characteristic parameters by an external Integrated Circuit (IC). The method has the advantages of simple pixel circuit, large compensation parameter and range and low running speed and is difficult to meet the high-frequency working condition.
Disclosure of Invention
In view of the above, an objective of the embodiments of the invention is to provide a pixel circuit capable of performing hybrid compensation, a control method thereof, a display substrate, and a display device.
In view of the above object, a first aspect of embodiments of the present invention provides a pixel circuit including a first transistor, a second transistor, a third transistor, a storage capacitor, and a light emitting element; a control electrode of the first transistor is connected with a first scanning line, a first electrode and a second electrode of the first transistor are respectively connected with a control electrode and a data line of a third transistor, a control electrode of the second transistor is connected with a second scanning line, a first electrode and a second electrode of the second transistor are respectively connected with a second electrode and a sensing line of the third transistor, a first electrode of the third transistor is connected with a first power supply end, a first end and a second end of the storage capacitor are respectively connected with a control electrode of the third transistor and a first electrode of the second transistor, and a first electrode and a second electrode of the light-emitting element are respectively connected with a second electrode and a second power supply end of the third transistor;
the pixel circuit further comprises a compensation control unit which is respectively connected with the first pole of the first transistor and the sensing line; the compensation control unit is used for accessing a third scanning signal and completing external compensation and internal compensation of the pixel circuit in an auxiliary mode according to the third scanning signal.
Optionally, the compensation control unit includes a fourth transistor, a control electrode of the fourth transistor is connected to the third scan signal, and a first electrode and a second electrode of the fourth transistor are respectively connected to the first electrode of the first transistor and the sensing line.
Optionally, the pixel circuit further includes an external compensation module, where the external compensation module is respectively connected to the data line and the sensing line, and is used to assist in completing external compensation of the pixel circuit.
Optionally, the external compensation module includes an ADC unit, a lookup table unit, a control unit, a storage unit, and a DAC unit, which are connected in sequence;
the ADC unit is used for collecting the analog signal on the sensing line and converting the analog signal into a digital signal;
the lookup table unit is used for carrying out difference comparison on the digital signal and preset lookup table data to obtain difference data;
the control unit is used for processing according to the difference data to obtain compensation data;
the storage unit is used for storing the compensation data;
and the DAC unit is used for converting the compensation data into an analog compensation signal and compensating the analog compensation signal into the data line.
Optionally, the pixel circuit further includes a first switch and a second switch; the first end and the second end of the first switch are respectively connected with the sensing line and the third voltage end, and the first end and the second end of the second switch are respectively connected with the sensing line and the external compensation module.
Optionally, the light emitting element is an organic light emitting diode.
In a second aspect of the embodiments of the present invention, there is provided a control method applied to the pixel circuit described in any one of the preceding items, including:
the first scanning signal and the second scanning signal are both high level, the first transistor and the second transistor are opened, and the third scanning signal controls the compensation control unit to be closed;
a control electrode of the third transistor is connected to a low-level signal on a data line through the first transistor;
the sensing line is communicated with the external compensation module, and outputs the voltage value of the light-emitting element to the external compensation module for completing the external compensation of the pixel circuit;
and/or the presence of a gas in the gas,
the control method comprises the following steps:
in a first period, the second scanning signal and the third scanning signal are at high level, the first scanning signal is at low level, the sensing line is connected with a reset signal, the second transistor and the compensation control unit are opened, the first transistor is closed, and the control electrode and the second electrode of the third transistor are both connected with the reset signal;
in a second time period, the second scan signal and the third scan signal are at a low level, the first scan signal is at a high level, the sensing line is floating, the first transistor is turned on, the data line is connected to a reference voltage signal, the control electrode of the third transistor is connected to the reference voltage signal, the second electrode of the third transistor is the reference voltage signal minus the threshold voltage of the first transistor, and the voltage between the control electrode and the second electrode of the third transistor is the threshold voltage of the first transistor;
in a third time period, the second scan signal and the third scan signal are at a low level, the first scan signal is at a high level, the sensing line is floating, the first transistor is turned on, the data line is connected to a data signal, the control electrode of the third transistor is connected to the data signal, the second electrode of the third transistor is a reference voltage signal minus a threshold voltage of the first transistor plus an incremental voltage, and the incremental voltage is a difference value between the data signal and the reference voltage signal;
in a fourth period, the first scan signal, the second scan signal, and the third scan signal are all at a low level, the sensing line is floating, the first transistor, the second transistor, the third transistor, and the compensation control unit are all turned off, a voltage required for light emission of the light emitting element is stored in the storage capacitor, and a current value, which is related only to the data signal and the reference voltage signal, is calculated according to a formula of a current value flowing into the light emitting element during light emission, thereby completing internal compensation of the pixel circuit.
In a third aspect of the embodiments of the present invention, there is provided a display substrate including the pixel circuit as described in any one of the preceding claims.
In a fourth aspect of the embodiments of the present invention, there is provided a display device, including the display substrate as described above.
As can be seen from the foregoing, in the pixel circuit and the control method thereof, the display substrate, and the display device provided in the embodiments of the present invention, by providing the first transistor, the second transistor, the third transistor, the storage capacitor, and the compensation control unit, the compensation control unit can assist in completing the external compensation and the internal compensation of the pixel circuit according to the third scan signal, so that the pixel circuit can complete both the external compensation and the internal compensation, and the display effect can be well improved through the internal and external compensation.
Drawings
FIG. 1 is a schematic structural diagram of a pixel circuit according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of another embodiment of a pixel circuit provided in the present invention;
FIG. 3 is a schematic structural diagram of a pixel circuit according to another embodiment of the present invention;
FIG. 4 is a flowchart illustrating a control method of a pixel circuit according to an embodiment of the present invention;
FIG. 5 is a schematic diagram illustrating driving timing of control signals according to an embodiment of a control method for a pixel circuit provided in the present invention;
FIG. 6 is a flow chart illustrating a method for controlling a pixel circuit according to another embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating driving timing of control signals according to another embodiment of the control method for the pixel circuit provided in the present invention;
fig. 8 is a flowchart illustrating a control method of a pixel circuit according to another embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.
It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are used for distinguishing two entities with the same name but different names or different parameters, and it should be noted that "first" and "second" are merely for convenience of description and should not be construed as limitations of the embodiments of the present invention, and they are not described in any more detail in the following embodiments.
In view of the above, according to a first aspect of the embodiments of the present invention, an embodiment of a pixel circuit capable of performing hybrid compensation is provided. Fig. 1 is a schematic structural diagram of a pixel circuit according to an embodiment of the present invention.
The pixel circuit includes a first transistor T1, a second transistor T2, a third transistor T3, a storage capacitor C1, and a light emitting element 10; a control electrode of the first transistor T1 is connected to a first SCAN line SCAN1, a first electrode and a second electrode of the first transistor T1 are connected to a control electrode and a DATA line DATA of a third transistor T3, respectively, a control electrode of the second transistor T2 is connected to a second SCAN line SCAN2, a first electrode and a second electrode of the second transistor T2 are connected to a second electrode and a SENSE line SENSE of the third transistor T3, respectively, a first electrode of the third transistor T3 is connected to a first power source terminal OVDD, a first end and a second end of the storage capacitor C1 are connected to a control electrode of the third transistor T3 and a first electrode of the second transistor T2, respectively, and a first electrode and a second electrode of the light emitting device 10 are connected to a second electrode and a second power source terminal OVSS of the third transistor T3, respectively;
the pixel circuit further includes a compensation control unit 20, the compensation control unit 20 being respectively connected to the first pole of the first transistor T1 and the sensing line SENSE; the compensation control unit 20 is configured to access a third scan signal EN, and assist to complete external compensation and internal compensation of the pixel circuit according to the third scan signal EN.
As can be seen from the foregoing embodiments, in the pixel circuit provided in the embodiments of the present invention, by providing the first transistor, the second transistor, the third transistor, the storage capacitor, and the compensation control unit, the compensation control unit can assist in completing external compensation and internal compensation of the pixel circuit according to the third scan signal, so that the pixel circuit can complete both external compensation and internal compensation, and the display effect can be well improved through the internal and external compensation.
The embodiment of the invention also provides another embodiment of the pixel circuit. Fig. 2 is a schematic structural diagram of another embodiment of the pixel circuit according to the present invention.
The pixel circuit includes a first transistor T1, a second transistor T2, a third transistor T3, a storage capacitor C1, and a light emitting element 10; a control electrode of the first transistor T1 is connected to a first SCAN line SCAN1, a first electrode and a second electrode of the first transistor T1 are connected to a control electrode and a DATA line DATA of a third transistor T3, respectively, a control electrode of the second transistor T2 is connected to a second SCAN line SCAN2, a first electrode and a second electrode of the second transistor T2 are connected to a second electrode and a SENSE line SENSE of the third transistor T3, respectively, a first electrode of the third transistor T3 is connected to a first power source terminal OVDD, a first end and a second end of the storage capacitor C1 are connected to a control electrode of the third transistor T3 and a first electrode of the second transistor T2, respectively, and a first electrode and a second electrode of the light emitting device 10 are connected to a second electrode and a second power source terminal OVSS of the third transistor T3, respectively; optionally, the light emitting element 10 is an organic light emitting diode OLED.
The pixel circuit further includes a compensation control unit 20, the compensation control unit 20 being respectively connected to the first pole of the first transistor T1 and the sensing line SENSE; preferably, the compensation control unit 20 includes a fourth transistor T4, a control electrode of the fourth transistor T4 is connected to the third scan signal EN, and a first electrode and a second electrode of the fourth transistor T4 are respectively connected to a first electrode of the first transistor T1 and the sensing line SENSE; the compensation control unit 20 is configured to access a third scan signal EN, and assist to complete external compensation and internal compensation of the pixel circuit according to the third scan signal EN.
As can be seen from the foregoing embodiments, in the pixel circuit provided in the embodiments of the present invention, the first transistor, the second transistor, the third transistor, the storage capacitor, and the fourth transistor are arranged to form a hybrid compensation pixel driving circuit, and the fourth transistor can assist in completing external compensation and internal compensation of the pixel circuit according to the third scan signal, so that the pixel circuit can complete both external compensation and internal compensation, and the display effect can be well improved through the internal and external compensation.
It should be noted that, when the overall uniformity of each transistor (optionally TFT) is better, the pixel circuit provided by the embodiment of the present invention can also be changed into a classic 3TIC (3 TFTs and one capacitor) external compensation pixel circuit by controlling the timing.
The embodiment of the invention also provides another embodiment of the pixel circuit. Fig. 3 is a schematic structural diagram of a pixel circuit according to another embodiment of the present invention.
The pixel circuit includes a first transistor T1, a second transistor T2, a third transistor T3, a storage capacitor C1, and a light emitting element 10; a control electrode of the first transistor T1 is connected to a first SCAN line SCAN1, a first electrode and a second electrode of the first transistor T1 are connected to a control electrode and a DATA line DATA of a third transistor T3, respectively, a control electrode of the second transistor T2 is connected to a second SCAN line SCAN2, a first electrode and a second electrode of the second transistor T2 are connected to a second electrode and a SENSE line SENSE of the third transistor T3, respectively, a first electrode of the third transistor T3 is connected to a first power source terminal OVDD, a first end and a second end of the storage capacitor C1 are connected to a control electrode of the third transistor T3 and a first electrode of the second transistor T2, respectively, and a first electrode and a second electrode of the light emitting device 10 are connected to a second electrode and a second power source terminal OVSS of the third transistor T3, respectively; wherein a first node G is formed at the control electrode of the third transistor T3, and a second node S is formed at the second electrode of the third transistor T3; optionally, the light emitting element 10 is an organic light emitting diode OLED, so that the pixel circuit can be applied to an OLED display device, thereby completing internal compensation and external compensation of each pixel in the OLED display device; wherein the equivalent capacitance C2 is the equivalent capacitance of the organic light emitting diode OLED; optionally, the first power supply terminal OVDD is connected to a high-level signal, and the second power supply terminal OVSS is connected to a low-level signal.
The pixel circuit further includes a compensation control unit 20, the compensation control unit 20 being respectively connected to the first pole of the first transistor T1 and the sensing line SENSE; preferably, the compensation control unit 20 includes a fourth transistor T4, a control electrode of the fourth transistor T4 is connected to the third scan signal EN, and a first electrode and a second electrode of the fourth transistor T4 are respectively connected to a first electrode of the first transistor T1 and the sensing line SENSE; the compensation control unit 20 is configured to access a third scanning signal EN, and assist to complete external compensation and internal compensation of the pixel circuit according to the third scanning signal EN;
the pixel circuit further comprises an external compensation module 30, wherein the external compensation module 30 is respectively connected to the DATA line DATA and the sensing line SENSE, and is used for assisting in completing external compensation of the pixel circuit.
Optionally, the external compensation module 30 includes an ADC unit 301, a lookup table unit 302, a control unit 303, a storage unit 304, and a DAC unit 305, which are connected in sequence;
the ADC unit 301 is configured to acquire an analog signal on the sensing line SENSE and convert the analog signal into a digital signal;
the lookup table unit 302 is configured to compare the digital signal with preset lookup table data to obtain difference data;
the control unit 303 is configured to obtain compensation data according to the difference data processing;
the storage unit 304 is configured to store the compensation data;
the DAC unit 305 is configured to convert the compensation DATA into an analog compensation signal and compensate the analog compensation signal into the DATA line DATA.
It should be noted that the circuit structure of the external compensation module 30 may be various, and only one of the typical circuits is shown in the present embodiment, and those skilled in the art can easily modify it into other circuit structures, and the functions implemented by these modifications are substantially similar to those implemented by the circuit in the present embodiment, so these modifications should also be included in the protection scope of the present invention.
Optionally, the pixel circuit further includes a first switch S1 and a second switch S2; a first terminal and a second terminal of the first switch S1 are respectively connected to the sensing line SENSE and a third voltage terminal Vreset, and a first terminal and a second terminal of the second switch S2 are respectively connected to the sensing line SENSE and the external compensation module 30; so that the pixel circuit can be controlled to be connected to the external compensation circuit or the third voltage terminal Vreset by the switching control of the first switch S1 and the second switch S2. Preferably, the third voltage terminal Vreset is connected to a reset signal, and is used for performing potential reset on the first node G and the second node S in the pixel circuit; optionally, a reset signal for turning on the third voltage terminal Vreset is 0V.
As can be seen from the foregoing embodiments, in the pixel circuit provided in the embodiments of the present invention, the first transistor, the second transistor, the third transistor, the storage capacitor, and the fourth transistor are arranged to form a hybrid compensation pixel driving circuit, and the fourth transistor can assist in completing external compensation and internal compensation of the pixel circuit according to the third scan signal, so that the pixel circuit can complete external compensation and internal compensation through the external compensation module, and the display effect can be well improved through the internal and external compensation.
It should be noted that, when the overall uniformity of each transistor (optionally TFT) is better, the pixel circuit provided by the embodiment of the present invention can also be changed into a classic 3TIC (3 TFTs and one capacitor) external compensation pixel circuit by controlling the timing.
It should be noted that the transistors in the above embodiments are independently selected from one of a polysilicon thin film transistor, an amorphous silicon thin film transistor, an oxide thin film transistor, and an organic thin film transistor. The "control electrode" referred to in this embodiment may specifically refer to a gate or a base of a transistor, the "first electrode" may specifically refer to a source or an emitter of the transistor, and the corresponding "second electrode" may specifically refer to a drain or a collector of the transistor. Of course, those skilled in the art will appreciate that the "first pole" and "second pole" are interchangeable.
In addition, the first transistor T1, the second transistor T2, the third transistor T3, and the fourth transistor T4 in the above embodiments are all N-type transistors, which is a preferred solution that is convenient to implement in this embodiment, and does not limit the technical solution of the present invention. It should be understood by those skilled in the art that the type (N-type or P-type) of each transistor and the polarities of the output voltages of each power source terminal and the control signal line are simply changed to implement the same on or off operation for each transistor as in the present embodiment, and all of them belong to the protection scope of the present application. The specific cases are not illustrated here.
In view of the above object, according to a second aspect of the embodiments of the present invention, there is provided an embodiment of a control method for a pixel circuit that can perform hybrid compensation. Fig. 4 is a schematic flow chart of a control method of a pixel circuit according to an embodiment of the present invention.
With reference to fig. 3 and 5, the control method of the pixel circuit is applied to the pixel circuit according to any of the foregoing embodiments, and includes:
step 401: the first and second SCAN signals SCAN1 and SCAN2 are both high, the first and second transistors T1 and T2 are turned on, the third transistor T3 is turned off, and the third SCAN signal EN controls the compensation control unit 20 (the fourth transistor T4 in one embodiment) to be turned off;
step 402: the control electrode (first node G) of the third transistor T3 is connected to the low level signal (which may be 0V) on the DATA line DATA through the first transistor T1, and the signal of the control electrode (first node G) of the third transistor T3 is stable and does not interfere with the potential of the second electrode (second node S) of the third transistor T3;
step 403: the sensing line SENSE is communicated with the external compensation module 30, and the sensed voltage value of the light emitting element 10 is output to the external compensation module 30 through the second transistor T2 for completing the external compensation of the pixel circuit.
Alternatively, referring to fig. 3, the sensing line SENSE is communicated with the external compensation module 30 by closing the second switch S2 and opening the first switch S1. Optionally, the sensing line SENSE is connected to the ADC unit 301 of the external compensation module 30, the lookup table unit 302 performs difference comparison between the acquired signal and preset lookup table data, and then performs modification processing on the data line signal through the control unit 303, the storage unit 304 and the DAC unit 305, so as to ensure that the display brightness is consistent.
In this way, the sensing line SENSE is used to obtain the sensing voltage value after the light emitting element 10 is aged and decayed, and then the difference comparison is performed through the lookup table in the external compensation module 30 to obtain the aging information of the light emitting element 10. On the basis of the aging information of the different light emitting elements 10, the data line signal to be input is corrected, thereby ensuring the display luminance to be consistent and completing the external compensation of the pixel circuit.
The embodiment of the invention also provides another embodiment of a control method of the pixel circuit capable of completing hybrid compensation. Fig. 6 is a schematic flow chart of a control method of a pixel circuit according to another embodiment of the present invention.
With reference to fig. 3 and fig. 7, the control method of the pixel circuit is applied to the pixel circuit according to any of the foregoing embodiments, and the control method includes:
step 501: at the first time period T1, which can also be understood as a reset phase or a reset phase, the second SCAN signal SCAN2 and the third SCAN signal EN are at a high level, the first SCAN signal SCAN1 is at a low level, the sensing line SENSE is connected to a reset signal Vreset (which can be realized by closing the first switch S1 and opening the second switch S2), the second transistor T2 and the compensation control unit 20 are opened (optionally, the fourth transistor T4 is opened), the first transistor T1 is closed, the control electrode and the second electrode of the third transistor T3 are connected to the reset signal Vreset, the reset signal Vreset is at a low level (which can be 0V), that is, the first node G and the second node S are both set low to the reset signal Vreset; it can be seen that the potential at the point G and the point S in this period can be ensured to be consistent by the design of the second transistor T2 and the compensation control unit 20, which facilitates the compensation calculation.
Step 502: during the second period t2, which can also be understood as a compensation phase, the second SCAN signal SCAN2 and the third SCAN signal EN are low, the first SCAN signal SCAN1 is high, the SENSE line SENSE floats empty (which can be achieved by opening the first switch S1 and the second switch S2), the first transistor T1 is turned on, the DATA line DATA is connected to a reference voltage signal (i.e., Vdata-Vref), a control electrode of the third transistor T3 is connected to the reference voltage signal Vref (i.e. the potential VG at the first node G is Vref), the second pole of the third transistor T3 is the reference voltage signal minus the threshold voltage of the first transistor T1, that is, the potential VS of the second node S is Vref-Vth _ T1, and the voltage between the control electrode and the second electrode of the third transistor T3 is the threshold voltage Vth _ T1 of the first transistor T1, that is, VGS is VG-VS is Vth _ T1.
In the third period T3, it can also be understood as a DATA writing phase, the second SCAN signal SCAN2 and the third SCAN signal EN are at a low level, the first SCAN signal SCAN1 is at a high level, the sensing line SENSE is floating (which can be realized by opening the first switch S1 and the second switch S2), the first transistor T1 is turned on, the DATA line DATA is connected to a DATA signal Vdata ' (to be written to a gray scale voltage value), i.e., Vdata ═ Vdata ', the control electrode of the third transistor T3 is connected to the DATA signal Vdata ', i.e., VG ═ Vdata ', the second electrode of the third transistor T3 is a difference between the reference voltage signal and the threshold voltage Vth _ T1 of the first transistor T1 plus an incremental voltage △ V, i.e., Vref-Vth _ T1+ △ V, and the incremental voltage △ V is a difference between the DATA signal Vdata ' and the reference voltage signal Vref.
It should be noted that, when VG is Vdata', the incremental voltage △ V is calculated by the following formula in order to make the third transistor T3 open more sufficiently to raise the potential at the second node S:
therefore, VGS = VG-VS = Vdata ' - { Vref-Vth _ T1+ α (Vdata ' -Vref) } (1- α) (Vdata ' -Vref)
Where C1 is a storage capacitor and C2 is an equivalent capacitor of the light-emitting element 10.
Step 504: in the fourth period T4, which can also be understood as a light emitting period, the first SCAN signal SCAN1, the second SCAN signal SCAN2 and the third SCAN signal EN are all at a low level, the sensing line SENSE is floated (which can be realized by opening the first switch S1 and the second switch S2), the first transistor T1, the second transistor T2, the third transistor T3 and the compensation control unit 20 are all turned off, a voltage required for the light emitting element 10 to emit light is stored in the storage capacitor C1, and a current value is calculated according to a formula of a current value flowing into the light emitting element 10 during the light emitting process, the current value being related to only the data signal Vdata' and the reference voltage signal Vref, thereby completing the internal compensation of the pixel circuit.
Specifically, the method comprises the following steps: the calculation formula of the current value flowing into the light emitting element 10 during light emission is as follows:
I＝1/2·Cox·u·(w/l)(VGS-Vth)2。
since VGS = VG-VS = Vdata ' - { Vref-Vth _ T1+ α (Vdata ' -Vref) } (1- α) (Vdata ' -Vref)
Therefore, I is 1/2. Cox. u. (w/l) (VGS-Vth)2 
=1/2·K(Vdata'-Vref)2(let Cox and u be stable).
The current value formula I of the current flowing from the light emitting stage after the modification process to the light emitting element 10 is 1/2 · K (Vdata' -Vref)2It can be seen that the magnitude of the I value is only related to Vdata' -Vref, so that Vth _ T1 can be effectively compensated.
It should be noted that, when the overall uniformity of the oxide TFT is better as the process level of the oxide TFT is improved, the pixel circuit in the embodiment of the present invention may be changed into a classic 3TIC external compensation pixel circuit by controlling the timing of the third scan signal EN to be a low level.
The embodiment of the invention also provides a control method of the pixel circuit capable of completing the hybrid compensation. Fig. 8 is a schematic flow chart of a control method of a pixel circuit according to another embodiment of the present invention.
The control method of the pixel circuit comprises an external compensation step which is performed firstly and an internal compensation step which is performed later, and specifically comprises the following steps:
step 60: the external compensation specifically comprises:
step 601: the first scanning signal and the second scanning signal are both high level, the first transistor and the second transistor are opened, and the third scanning signal controls the compensation control unit to be closed;
step 602: a control electrode of the third transistor is connected to a low-level signal on a data line through the first transistor;
step 603: the sensing line is communicated with the external compensation module, and outputs the voltage value of the light-emitting element to the external compensation module for completing the external compensation of the pixel circuit;
step 70: the internal compensation specifically comprises:
step 701: in a first period, the second scanning signal and the third scanning signal are at high level, the first scanning signal is at low level, the sensing line is connected with a reset signal, the second transistor and the compensation control unit are opened, the first transistor is closed, and the control electrode and the second electrode of the third transistor are both connected with the reset signal;
step 702: in a second time period, the second scan signal and the third scan signal are at a low level, the first scan signal is at a high level, the sensing line is floating, the first transistor is turned on, the data line is connected to a reference voltage signal, the control electrode of the third transistor is connected to the reference voltage signal, the second electrode of the third transistor is the reference voltage signal minus the threshold voltage of the first transistor, and the voltage between the control electrode and the second electrode of the third transistor is the threshold voltage of the first transistor;
step 703: in a third time period, the second scan signal and the third scan signal are at a low level, the first scan signal is at a high level, the sensing line is floating, the first transistor is turned on, the data line is connected to a data signal, the control electrode of the third transistor is connected to the data signal, the second electrode of the third transistor is a reference voltage signal minus a threshold voltage of the first transistor plus an incremental voltage, and the incremental voltage is a difference value between the data signal and the reference voltage signal;
step 704: in a fourth period, the first scan signal, the second scan signal, and the third scan signal are all at a low level, the sensing line is floating, the first transistor, the second transistor, the third transistor, and the compensation control unit are all turned off, a voltage required for light emission of the light emitting element is stored in the storage capacitor, and a current value, which is related only to the data signal and the reference voltage signal, is calculated according to a formula of a current value flowing into the light emitting element during light emission, thereby completing internal compensation of the pixel circuit.
As can be seen from the foregoing, in the control method of the pixel circuit provided in the embodiment of the present invention, by matching the pixel circuit provided with the first transistor, the second transistor, the third transistor, the storage capacitor, and the compensation control unit, the compensation control unit can assist in completing the external compensation and the internal compensation of the pixel circuit according to the third scan signal, so that the control method of the pixel circuit can complete both the external compensation and the internal compensation, and the display effect can be well improved through the internal and external compensation.
It should be noted that, although the order of the internal compensation and the external compensation is defined in the present embodiment, this does not mean that the external compensation of the internal compensation must be performed in such an order, and in some cases, the order of performing the internal compensation and the external compensation may be reversed. Moreover, the internal compensation and the external compensation may be performed in different pixel compensation periods respectively, or may be performed sequentially in the same pixel compensation period, which are reasonable choices for those skilled in the art, and any implementation manner is not applied to limit the protection scope of the present invention.
In view of the above object, according to a third aspect of the embodiments of the present invention, there is provided an embodiment of a display substrate that can perform hybrid compensation.
The display substrate comprises the pixel circuit as described in any one of the previous embodiments.
As can be seen from the foregoing, in the display substrate provided in the embodiment of the present invention, the first transistor, the second transistor, the third transistor, the storage capacitor, and the compensation control unit are disposed in the pixel circuit, and the compensation control unit can assist in completing the external compensation and the internal compensation of the pixel circuit according to the third scan signal, so that the display substrate can complete both the external compensation and the internal compensation, and the display effect can be well improved through the internal and external compensation.
Preferably, the display substrate is an OLED (organic light emitting diode) display substrate, so that the pixel circuits in the display substrate can better realize internal compensation and external compensation.
In view of the above object, a fourth aspect of the embodiments of the present invention provides an embodiment of a display device that can perform hybrid compensation.
The display device comprises the display substrate.
The display device in this embodiment may be: any product or component with a display function, such as electronic paper, a mobile phone, a tablet computer, a television, a notebook computer, a digital photo frame, a navigator and the like.
As can be seen from the foregoing, in the display device according to the embodiment of the present invention, the first transistor, the second transistor, the third transistor, the storage capacitor, and the compensation control unit are disposed in the pixel circuit, and the compensation control unit can assist in completing the external compensation and the internal compensation of the pixel circuit according to the third scan signal, so that the display device can complete both the external compensation and the internal compensation, and the display effect can be well improved through the internal and external compensation.
Preferably, the display device is an OLED (organic light emitting diode) display device, so that the pixel circuit in the display device can better realize internal compensation and external compensation.
In the present invention, the terms "first", "second", "third", and "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. The term "plurality" means two or more unless expressly limited otherwise.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A pixel circuit includes a first transistor, a second transistor, a third transistor, a storage capacitor, and a light emitting element; a control electrode of the first transistor is connected with a first scanning line, a first electrode and a second electrode of the first transistor are respectively connected with a control electrode and a data line of a third transistor, a control electrode of the second transistor is connected with a second scanning line, a first electrode and a second electrode of the second transistor are respectively connected with a second electrode and a sensing line of the third transistor, a first electrode of the third transistor is connected with a first power supply end, a first end and a second end of the storage capacitor are respectively connected with a control electrode of the third transistor and a first electrode of the second transistor, and a first electrode and a second electrode of the light-emitting element are respectively connected with a second electrode and a second power supply end of the third transistor;
the pixel circuit further comprises a compensation control unit, wherein the compensation control unit is respectively connected with the first pole of the first transistor and the sensing line; the compensation control unit is used for accessing a third scanning signal and completing external compensation and internal compensation of the pixel circuit in an auxiliary mode according to the third scanning signal; the third scanning signal controls the compensation control unit to be switched on in a first period of internal compensation, and controls the compensation control unit to be switched off in other periods of internal compensation and external compensation;
the compensation control unit comprises a fourth transistor, a control electrode of the fourth transistor is connected to the third scanning signal, and a first electrode and a second electrode of the fourth transistor are respectively connected with a first electrode of the first transistor and the sensing line.
2. The pixel circuit according to claim 1, further comprising an external compensation module, wherein the external compensation module is respectively connected to the data line and the sensing line, and is configured to assist in performing external compensation of the pixel circuit.
3. The pixel circuit according to claim 2, wherein the external compensation module comprises an ADC unit, a lookup table unit, a control unit, a storage unit and a DAC unit connected in sequence;
the ADC unit is used for collecting the analog signal on the sensing line and converting the analog signal into a digital signal;
the lookup table unit is used for carrying out difference comparison on the digital signal and preset lookup table data to obtain difference data;
the control unit is used for processing according to the difference data to obtain compensation data;
the storage unit is used for storing the compensation data;
and the DAC unit is used for converting the compensation data into an analog compensation signal and compensating the analog compensation signal into the data line.
4. The pixel circuit according to claim 2, further comprising a first switch and a second switch; the first end and the second end of the first switch are respectively connected with the sensing line and the third voltage end, and the first end and the second end of the second switch are respectively connected with the sensing line and the external compensation module.
5. The pixel circuit according to claim 1, wherein the light emitting element is an organic light emitting diode.
6. A control method applied to the pixel circuit according to any one of claims 1 to 5, wherein the control method comprises:
the first scanning signal and the second scanning signal are both high level, the first transistor and the second transistor are opened, and the third scanning signal controls the compensation control unit to be closed;
a control electrode of the third transistor is connected to a low-level signal on a data line through the first transistor;
the sensing line is communicated with the external compensation module, and outputs the voltage value of the light-emitting element to the external compensation module for completing the external compensation of the pixel circuit;
and/or the presence of a gas in the gas,
the control method comprises the following steps:
in a first period, the second scanning signal and the third scanning signal are at high level, the first scanning signal is at low level, the sensing line is connected with a reset signal, the second transistor and the compensation control unit are opened, the first transistor is closed, and the control electrode and the second electrode of the third transistor are both connected with the reset signal;
in a second time period, the second scan signal and the third scan signal are at a low level, the first scan signal is at a high level, the sensing line is floating, the first transistor is turned on, the data line is connected to a reference voltage signal, the control electrode of the third transistor is connected to the reference voltage signal, the second electrode of the third transistor is the reference voltage signal minus the threshold voltage of the first transistor, and the voltage between the control electrode and the second electrode of the third transistor is the threshold voltage of the first transistor;
in a third time period, the second scan signal and the third scan signal are at a low level, the first scan signal is at a high level, the sensing line is floating, the first transistor is turned on, the data line is connected to a data signal, the control electrode of the third transistor is connected to the data signal, the second electrode of the third transistor is a reference voltage signal minus a threshold voltage of the first transistor plus an incremental voltage, and the incremental voltage is a difference value between the data signal and the reference voltage signal;
in a fourth period, the first scan signal, the second scan signal, and the third scan signal are all at a low level, the sensing line is floating, the first transistor, the second transistor, the third transistor, and the compensation control unit are all turned off, a voltage required for light emission of the light emitting element is stored in the storage capacitor, and a current value, which is related only to the data signal and the reference voltage signal, is calculated according to a formula of a current value flowing into the light emitting element during light emission, thereby completing internal compensation of the pixel circuit.
7. A display substrate comprising the pixel circuit according to any one of claims 1 to 5.
8. A display device comprising the display substrate according to claim 7.
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