CN110459179B - Display device - Google Patents
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- CN110459179B CN110459179B CN201910815467.4A CN201910815467A CN110459179B CN 110459179 B CN110459179 B CN 110459179B CN 201910815467 A CN201910815467 A CN 201910815467A CN 110459179 B CN110459179 B CN 110459179B
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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]
- G09G3/3275—Details of drivers for data electrodes
- G09G3/3291—Details of drivers for data electrodes in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0233—Improving the luminance or brightness uniformity across the screen
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- Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
- Control Of El Displays (AREA)
Abstract
The invention provides a display device, wherein before driving a pixel to emit light, a detection circuit is adopted to detect the threshold voltage of the pixel, and in the process of driving the pixel to emit light, the threshold voltage is used for compensation operation of a driving circuit, so that the current flowing through a light-emitting device is unrelated to the threshold voltage of a driving transistor, the light-emitting brightness of each pixel can be the same, and the light-emitting brightness of a display screen is uniform.
Description
Technical Field
The invention relates to the technical field of display, in particular to a display device.
Background
In the prior art, a display screen adopts an organic material to manufacture a light-emitting device, a pixel circuit is constructed by using a thin film transistor, pixels are arranged in an array mode, and the display screen adopts a refreshing mode of scanning line by line. However, even if the driving voltages are completely the same, the light emission luminance of each pixel is not necessarily the same, thereby causing a problem of non-uniformity of the light emission luminance of the display screen.
Disclosure of Invention
In view of this, embodiments of the present invention provide a display device, which solves the technical problem of uneven display brightness of a display screen in the prior art.
For the purpose of making the objects, technical means and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
According to an aspect of the present invention, an embodiment of the present invention provides a display device including: the pixel driving circuit is used for driving pixels in the display device to emit light and comprises a driving transistor, wherein a first end of the driving transistor receives a power supply voltage; the driving chip is used for providing data signal voltage for a driving transistor in the pixel driving circuit; the input end of the detection circuit is electrically connected with the second end of the driving transistor in the pixel driving circuit, the output end of the detection circuit outputs a digital signal, and the digital signal reflects the channel current of the driving transistor; wherein the driver chip is further configured to: and receiving the digital signal output by the detection circuit, and calculating and storing the threshold voltage of the driving transistor according to the digital signal.
In an embodiment of the present invention, the driving chip includes: the judging module is used for receiving the digital signal output by the detecting circuit and judging the channel current of the driving transistor according to the digital signal; and the calculation module is used for recording the data signal voltage output by the driving chip when the channel current of the driving transistor is zero, and calculating and storing the threshold voltage of the driving transistor according to the data signal voltage.
In an embodiment of the present invention, the detection circuit includes: a first switching transistor, a first terminal of the first switching transistor being electrically connected to the second terminal of the driving transistor; a first capacitor connected in parallel with the first switching transistor; the first end of the operational amplifier is electrically connected with the first end of the first capacitor, the second end of the operational amplifier is connected with the second end of the first capacitor, and the third end of the operational amplifier receives an initialization voltage; a symmetric multiprocessor, a first end of the symmetric multiprocessor being electrically connected with the second end of the operational amplifier; and the first end of the analog-digital converter is electrically connected with the second end of the symmetric multiprocessor, the second end of the analog-digital converter is an output end, and the output end outputs the digital signal.
In an embodiment of the present invention, the display device further includes: a first controller for providing a first scan control signal to the first switching transistor and the symmetric multiprocessor; wherein the first controller is configured to perform the steps of: transmitting a first scan control signal having a first voltage amplitude to the first switching transistor so that the first switching transistor is turned on; transmitting a control signal having a second voltage magnitude to the symmetric multiprocessor such that the symmetric multiprocessor is turned off; transmitting a first scan control signal having a second voltage amplitude to the first switching transistor so that the first switching transistor is turned off; transmitting a control signal having a first voltage amplitude to the symmetric multiprocessor such that the symmetric multiprocessor is turned on; and transmitting a first scan control signal having a first voltage amplitude to the first switching transistor so that the first switching transistor is turned on; transmitting a control signal having a second voltage magnitude to the symmetric multiprocessor such that the symmetric multiprocessor is turned off.
In embodiments of the present invention, the display device includes: a plurality of pixels distributed in N rows and M rows, wherein M and N are integers greater than or equal to 2; and a multiplexer for electrically connecting the detection circuit to the second terminals of the drive transistors in the pixel drive circuits of each row of pixels in sequence.
In an embodiment of the present invention, the pixel driving circuit includes: a light emitting device; one end of the data storage module is used for receiving power supply voltage, and the other end of the data storage module is electrically connected with the control end of the driving transistor; one end of the data storage control module receives a data signal voltage, and the other end of the data storage control module is electrically connected with the control end of the driving transistor and the other end of the data storage module respectively; and one end of the initialization module is electrically connected with the second end of the driving transistor and the anode of the light-emitting device respectively, and the other end of the initialization module is electrically connected with the input end of the detection circuit.
In an embodiment of the present invention, the data storage module includes a second capacitor, a first end of the second capacitor is configured to receive the power supply voltage, and a second end of the second capacitor is electrically connected to the control end of the driving transistor; the data storage control module comprises a second switch transistor, wherein a first end of the second switch transistor receives the data signal voltage, and a second end of the second switch transistor is electrically connected with a control end of the driving transistor and a second end of the second capacitor respectively; the initialization module comprises a third switching transistor, wherein the first end of the third switching transistor is electrically connected with the second end of the driving transistor, and the second end of the third switching transistor is electrically connected with the input end of the detection circuit.
In an embodiment of the present invention, the display device further includes: and the scanning control line is respectively and electrically connected with the control end of the second switching transistor and the control end of the third switching transistor and is used for transmitting scanning control signals for the second switching transistor and the third switching transistor.
In an embodiment of the present invention, the scan control line includes: the first scanning control line is electrically connected with the control end of the second switching transistor and is used for transmitting a second scanning control signal to the second switching transistor; and a second scanning control line electrically connected to the control terminal of the third switching transistor, for transmitting a third scanning control signal to the third switching transistor.
In an embodiment of the present invention, the display device further includes: a second controller having one end electrically connected to the scan control line for providing the scan control signal to the scan control line, wherein the second controller is configured to perform the following steps: transmitting a scan control signal having a third voltage amplitude to the control terminal of the second switching transistor and the control terminal of the third switching transistor so that the second switching transistor and the third switching transistor are both turned on; transmitting a scan control signal having a third voltage amplitude to a control terminal of a second switching transistor and a control terminal of a third switching transistor, such that the second switching transistor and the third switching transistor are both turned on; and transmitting a scan control signal having a fourth voltage amplitude to a control terminal of the second switching transistor and a control terminal of the third switching transistor, such that the second switching transistor and the third switching transistor are both turned off.
The display device provided by the embodiment of the invention adopts the detection circuit to detect the threshold voltage of the driving transistor in one pixel circuit, and the detected threshold voltage drop is used for compensating the threshold voltage of the driving transistor in the process of driving the pixel to emit light, so that the current of each pixel is unrelated to the threshold voltage of the driving transistor in the pixel circuit, the light-emitting brightness of each pixel is the same, and the light-emitting brightness of the display screen is uniform.
Drawings
Fig. 1 is a schematic structural diagram of a display device according to an embodiment of the invention;
fig. 2 is a schematic structural diagram of a display device according to another embodiment of the present invention;
fig. 3 is a schematic structural diagram of a display device according to another embodiment of the present invention;
fig. 4 is a schematic structural diagram of a display device according to another embodiment of the present invention;
fig. 5 is a schematic structural diagram of a display device according to another embodiment of the invention;
fig. 6 is a schematic structural diagram of a display device according to another embodiment of the present invention;
fig. 7 is a driving timing diagram illustrating a driving timing of a detecting pixel in a display device according to an embodiment of the invention;
fig. 8 is a timing diagram illustrating a variation of a data signal voltage when a detection pixel is driven according to another embodiment of the invention.
Detailed Description
As described in the background art, the light-emitting luminance of each pixel in the display panel in the prior art is not uniform, so that the display luminance of the display panel is not uniform, and the inventor researches and discovers that the problem occurs because the driving thin film transistor in the pixel circuit operates in a saturation region, the channel current is equal to the light-emitting current of the light-emitting device, but the threshold voltage of each driving thin film transistor is different due to manufacturing reasons, so that the light-emitting luminance of each pixel is not uniform, and the problem of the display luminance of the display panel is not uniform.
Based on this, the invention provides a display device, before driving the pixel to emit light, the threshold voltage of the pixel is detected by a detection circuit, and in the process of driving the pixel to emit light, the threshold voltage is used for compensation operation of the driving circuit, so that the current flowing through the light-emitting device is unrelated to the threshold voltage of the driving transistor, the light-emitting brightness of each pixel can be the same, and the light-emitting brightness of the display screen is uniform.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Specifically, the present invention provides a display device, including: the pixel driving circuit is used for driving pixels in the display device to emit light and comprises a driving transistor, wherein a first end of the driving transistor receives a power supply voltage; the driving chip is used for providing data signal voltage for a driving transistor in the pixel driving circuit; the input end of the detection circuit is electrically connected with the second end of the driving transistor in the pixel driving circuit, and the output end of the detection circuit outputs a digital signal which can reflect the channel current of the driving transistor; wherein the driver chip is further configured to: and receiving the digital signal output by the detection circuit, and calculating and storing the threshold voltage of the driving transistor according to the digital signal.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a schematic structural diagram of a display device according to an embodiment of the present invention, and as shown in fig. 1, the display device includes: the pixel driving circuit 1, the driving chip 2, the data signal line and the detecting circuit 3; the pixel driving circuit 1 is used for driving a pixel in the display device to emit light, and the pixel driving circuit 1 includes a driving transistor M5, and a first terminal of the driving transistor M5 receives a power supply voltage Vdd. One end of the driving chip 2 is electrically connected to the control end of the driving transistor M5 through a Data signal line (Data line), and the driving chip 2 provides a Data signal voltage Vdata to the gate of the driving transistor M5 in the pixel driving circuit 1. The input end of the detection circuit 3 is electrically connected to the second end of the driving transistor M5, so as to electrically connect the detection circuit 3 to the pixel driving circuit 1, the output end of the detection circuit 3 is electrically connected to the first end of the driving chip 2, and the output end of the detection circuit 3 outputs a digital signal Code, where the digital signal Code can reflect the channel current of the driving transistor M5. Wherein the driving chip 2 is further configured to: the digital signal Code output by the detection circuit 3 is received, and the threshold voltage of the driving transistor M5 is calculated and stored according to the digital signal Code.
The display device provided by the embodiment of the invention adopts the detection circuit 3 and the driving chip 2 to detect the threshold voltage of the driving transistor M5 in one pixel circuit under the cooperation, and the detected threshold voltage is used for compensating the threshold voltage of the driving transistor M5 in the process of driving the pixel to emit light, so that the current of the pixel is unrelated to the threshold voltage of the driving transistor M5 in the pixel circuit, the light-emitting brightness of each pixel is the same, and the light-emitting brightness of the display screen is uniform.
In an embodiment of the invention, as shown in fig. 2, the driving chip 2 includes a determining module 21 and a calculating module 22. The determining module 21 is configured to receive the digital signal Code output by the detecting circuit 3, and determine a channel current of the driving transistor M5 according to the digital signal Code. The calculating module 22 is used for recording the data signal voltage Vdata output by the driving chip 2 when the channel current of the driving transistor M5 is zero, and calculating and storing the threshold voltage of the driving transistor M5 according to the data signal voltage Vdata. When the two adjacent digital signal codes in the detection circuit 3 received by the judgment module 21 are close to or the same as each other, it is determined that the channel current of the driving transistor M5 is zero, and then the calculation module 22 records the value of the data signal voltage Vdata corresponding to the last digital signal Code in the two adjacent digital signal codes according to the information that the channel current transmitted by the driving transistor M5 is zero. When the channel current in the driving transistor M5 is zero, that is, the difference between the gate voltage of the driving transistor M5 (i.e., the data signal voltage Vdata) and the voltage of the first terminal of the driving transistor M5 (i.e., the power voltage Vdd) and the threshold voltage Vth of the driving transistor M5 is zero, that is, Vdata-Vdd-Vth is equal to 0, so that the threshold voltage Vth of the driving transistor M5 can be calculated as Vdata-Vdd.
In an embodiment of the invention, as shown in fig. 3, the detection circuit 3 includes a first switch transistor M1, a first capacitor C1, an operational amplifier OA, a symmetric multiprocessor SMP, and an analog-to-digital converter ADC. Wherein a first terminal of the first switching transistor M1 is electrically connected with a second terminal of the driving transistor M5 in the driving pixel circuit. The first capacitor C1 is connected in parallel with the first switch transistor M1. A first terminal of the operational amplifier OA is electrically connected to the first terminal of the first switching transistor M1 and the first terminal of the first capacitor C1, respectively, a second terminal of the operational amplifier OA is electrically connected to the second terminal of the first switching transistor M1 and the second terminal of the first capacitor C1, respectively, and a third terminal of the operational amplifier OA receives the initialization voltage. A first terminal of the symmetric multiprocessor SMP is electrically connected to a second terminal of the operational amplifier OA. The first end of the analog-digital converter ADC is electrically connected with the second end of the symmetric multiprocessor SMP, and the second end of the analog-digital converter ADC is an output end and used for outputting a digital signal Code. When the data signal voltage Vdata provided by the driving chip 2 to the gate of the driving transistor M5 sequentially changes (e.g. rises or falls), the operational amplifier OA and the first capacitor C1 form an integrator, and the integrator integrates the voltage at the second terminal of the driving transistor M5 once every time the data signal voltage Vdata changes, i.e. the input voltage of the integrator. After a number of changes of the data signal, the output voltage of the integrator (i.e. the voltage at the third terminal of the operational amplifier OA) is proportional to the time integral of the input voltage of the integrator. And the output voltage of the integrator is converted into a data signal through the symmetric multiprocessor SMP and the analog-digital converter ADC. Then, the digital signal Code is transmitted to the driving chip 2, and when the digital signal Code values of two adjacent samples are equal or close to each other, the driving chip 2 can determine that the channel current of the driving transistor M5 is zero at this time, and can calculate the threshold voltage of the driving transistor M5.
In a further embodiment of the present invention, the display device further comprises a first controller 7, as shown in fig. 6, one end of the first controller 7 is electrically connected to the control terminal of the first switching transistor M1 and the control terminal of the symmetric multiprocessor SMP, respectively, for providing control signals for the first switching transistor M1 and the symmetric multiprocessor SMP, wherein the first controller 7 is configured to perform the following steps:
step S101: transmitting a control signal having a first voltage magnitude to the first switching transistor M1 such that the first switching transistor M1 is turned on; a control signal having a second voltage magnitude is transmitted to the symmetric multiprocessor SMP such that the symmetric multiprocessor SMP is turned off.
In step S101, the first switching transistor M1 is turned on, the operational amplifier OA functions as a voltage follower, the voltages output from the third terminal of the operational amplifier OA are all initialization voltages, the initialization voltages are transmitted to the second terminal of the driving transistor M5, the pixel cannot be driven to emit light because the initialization voltages are low enough, the current in the driving transistor M5 is constant, the current in the driving transistor M5 flows into the voltage follower, and the sampling is not performed because the symmetric multiprocessor SMP is turned off.
Step S102: transmitting a signal having a second voltage magnitude to the first switching transistor M1 such that the first switching transistor M1 is turned off; transmitting a control signal having a first voltage magnitude to the symmetric multiprocessor SMP such that the symmetric multiprocessor SMP is turned on.
In step S102, the first switching transistor M1 is turned off, the operational amplifier OA and the first capacitor C1 form an integrator, and the integrator integrates the voltage at the second terminal of the driving transistor M5, i.e., the input voltage of the integrator, every time the data signal voltage Vdata changes. After a number of changes of the data signal, the output voltage of the integrator (i.e. the voltage at the third terminal of the operational amplifier OA) is proportional to the time integral of the input voltage of the integrator. And the symmetric multiprocessor SMP is turned on to start sampling the output voltage of the integrator, and the output voltage of the integrator is converted into a data signal through the symmetric multiprocessor SMP and the analog-digital converter ADC. Then, the digital signal Code is transmitted to the driving chip 2, and when the digital signal codes of two adjacent samples are equal or close to each other, the driving chip 2 can determine that the channel current of the driving transistor M5 is zero at this time, and can calculate the threshold voltage of the driving transistor M5.
Step S103: transmitting a signal having a first voltage magnitude to the first switching transistor M1 such that the first switching transistor M1 is turned on; a control signal having a second voltage magnitude is transmitted to the symmetric multiprocessor SMP such that the symmetric multiprocessor SMP is turned off.
In step S103, the first switching transistor M1 is turned on, the operational amplifier OA functions as a voltage follower, the current in the driving transistor M5 is constant, the current in the driving transistor M5 flows into the voltage follower, and the symmetrical multiprocessor SMP is turned off, so that no sampling is performed.
In an embodiment of the present invention, as shown in fig. 4, the pixel driving circuit 1 includes: a data storage module 4, a data storage control module 5 and an initialization module 6. One end of the data storage module 4 is used for receiving a power supply voltage Vdd, and the other end of the data storage module 4 is electrically connected with the control end of the driving transistor M5; the data storage module 4 is used for storing a data signal voltage Vdata. One end of the data storage control module 5 receives the data signal voltage Vdata, and the other end of the data storage control module 5 is electrically connected with the control end of the driving transistor M5 and the other end of the data storage module 4 respectively; the data storage control module 5 is used for controlling whether the data signal voltage Vdata is stored in the data storage module 4 and transmitted to the control terminal of the driving transistor M5. One end of the initialization module 6 is electrically connected to the second end of the driving transistor M5, and the other end of the initialization module 6 is electrically connected to the first end of the detection circuit 3; the initialization module 6 is used to initialize the anode voltage of the light emitting device and the voltage of the second terminal of the driving transistor M5.
In a further embodiment of the present invention, as shown in fig. 4, the data storage module 4 includes a second capacitor C2, a first terminal of the second capacitor C2 is for receiving the power voltage Vdd, and a second terminal of the second capacitor C2 is electrically connected to the control terminal of the driving transistor M5. The data storage control module 5 includes a second switching transistor M2, a first terminal of the second switching transistor M2 receives the data signal voltage Vdata, and a second terminal of the second switching transistor M2 is electrically connected to the control terminal of the driving transistor M5 and the second terminal of the second capacitor C2, respectively. The initialization module 6 includes a third switching transistor M3, a first terminal of the third switching transistor M3 is electrically connected to the second terminal of the driving transistor M5, and a second terminal of the third switching transistor M3 is electrically connected to the input terminal of the detection circuit 3. The pixel driving circuit 1 in the embodiment of the present invention has a circuit structure of 3T1C, and can complete three different operation stages of pixel light emission, namely, an initialization stage, a data storage stage, and a light emission stage, with a minimum number of switching transistors.
In an embodiment of the invention, the display device further includes a scan control line electrically connected to the control terminal of the second switching transistor M2 and the control terminal of the third switching transistor M3, respectively, the scan control line being used for transmitting scan control signals to the second switching transistor M2 and the third switching transistor M3. Under the control of the scan control signal, the second switching transistor M2 and the third switching transistor M3 are turned on or off, so that the pixel driving circuit 1 is in different operation stages. And the second switching transistor M2 and the third switching transistor M3 share one scanning control line, so that the number of signal lines of the pixel circuit is reduced, the parasitic capacitance of the data signal line is reduced, and the wiring space is improved.
In a further embodiment of the present invention, the scan control line includes: a first scanning control line and a second scanning control line. The first scan control line is electrically connected to the control terminal of the second switching transistor M2, and is used for transmitting a second scan control signal S2 to the second switching transistor M2, and the second switching transistor M2 is turned on or off by the second scan control signal S2, so that whether the data signal voltage Vdata is transmitted to the control terminal of the driving transistor M5 and the first terminal of the second capacitor C2 is determined. The second scan control line is electrically connected to a control terminal of the third switching transistor M3 for transmitting a third scan control signal S3 to the third switching transistor M3, and the third switching transistor M3 is turned on or off by the third scan control signal S3, so that whether the initialization voltage is transmitted to the second terminal of the driving transistor M5 and the anode of the light emitting device.
In another further embodiment of the present invention, as shown in fig. 6, the display device further includes: a second controller 8, one end of the second controller 8 being electrically connected to the scan control line for providing a scan control signal to the scan control line, wherein the second controller 8 is configured to perform the following steps:
step S201: the scan control signal having the third voltage magnitude is transmitted to the control terminal of the second switching transistor M2 and the control terminal of the third switching transistor M3 such that the second switching transistor M2 and the third switching transistor M3 are both turned on.
Step S202: the scan control signal having the third voltage magnitude is transmitted to the control terminal of the second switching transistor M2 and the control terminal of the third switching transistor M3 such that the second switching transistor M2 and the third switching transistor M3 are both turned on.
Step S203: the scan control signal having the fourth voltage magnitude is transmitted to the control terminal of the second switching transistor M2 and the control terminal of the third switching transistor M3 such that the second switching transistor M2 and the third switching transistor M3 are both turned off.
In an embodiment of the invention, as shown in fig. 5, the display device includes a plurality of pixels distributed in N rows and M columns, where M and N are integers greater than or equal to 2; and a multiplexer 9, the multiplexer 9 being adapted to electrically connect the detection circuit 3 to the second terminals of the driving transistors M5 in the pixel driving circuit 1 of each row of pixels in turn. For example, when scanning the pixels in the first row, each pixel in the first row has a corresponding pixel driving circuit 1, and when detecting the threshold voltage of the driving transistor M5 in each pixel driving circuit 1, the multiplexer 9 is used to electrically connect the detecting circuit 3 with the pixel driving circuit 1 of each row of pixels in the first row in turn, so that the display device uses one detecting circuit 3 to connect the threshold voltage of the driving transistor M5 of the pixel driving circuit 1 of all the pixels in the display device, thereby reducing the number of detecting circuits 3 in the display device.
In an embodiment of the present invention, the multiplexer 9 and the detection circuit 3 may be disposed in a driving board (abbreviated as TCON) of the display panel, that is, the driving board and the driving chip 2 are disposed in the same driving board of the display panel.
In order to better understand the image display device, the operation of the display device will be described in detail with reference to more specific embodiments.
As shown in fig. 5, the display device includes a pixel driving circuit 1, a second controller 8, a driving chip 2, a multiplexer 9, a detecting circuit 3, and a first control controller. When scanning the m-th row of pixels of the display device, the pixel driving circuit 1 of the m-th row and n-th column of pixels is as shown in fig. 5.
Wherein, the pixel driving circuit 1 includes: a second switching transistor M2, a third switching transistor M3, a light emitting device, a driving transistor M5, and a second capacitor C2. A first terminal of the second switching transistor M2 receives the data signal voltage Vdata, and a second terminal of the second switching transistor M2 is electrically connected to the control terminal of the driving transistor M5 and the second terminal of the second capacitor C2, respectively. A first terminal of the third switching transistor M3 is electrically connected to the second terminal of the driving transistor M5, and a second terminal of the third switching transistor M3 is electrically connected to one terminal of the multiplexer 9. The second controller 8 is electrically connected to the control terminal of the second switching transistor M2 and the control terminal of the third switching transistor M3, and the second controller 8 provides the second scan control signal S2 to the control terminal of the second switching transistor M2 and provides the third scan control signal S3 to the control terminal of the third switching transistor M3.
The detection circuit 3 comprises a first switch transistor M1, a first capacitor C1, an operational amplifier OA, a symmetric multiprocessor SMP, and an analog-to-digital converter ADC. Wherein a first terminal of the first switching transistor M1 is electrically connected to the other terminal of the multiplexer 9. The first capacitor C1 is connected in parallel with the first switch transistor M1. A first terminal of the operational amplifier OA is electrically connected to the first terminal of the first switching transistor M1 and the first terminal of the first capacitor C1, respectively, a second terminal of the operational amplifier OA is electrically connected to the second terminal of the first switching transistor M1 and the second terminal of the first capacitor C1, respectively, and a third terminal of the operational amplifier OA receives the initialization voltage. A first terminal of the symmetric multiprocessor SMP is electrically connected to a second terminal of the operational amplifier OA. The first end of the analog-digital converter ADC is electrically connected with the second end of the symmetric multiprocessor SMP, and the second end of the analog-digital converter ADC is an output end and used for outputting a digital signal Code. The first controller 7 is electrically connected to the control terminal of the first switching transistor M1.
One end of the driving chip 2 receives the digital signal Code, and the other end provides a data signal to the control end of the driving transistor M5 through a data signal line.
Fig. 7 shows timing diagrams of the first scan control signal S1 controlled by the first controller 7, the second scan control signal S2 and the third scan control signal S3 controlled by the second controller 8, and the symmetric multiprocessor SMP.
The second switching transistor M2 and the third switching transistor M3 in the pixel driving circuit 1 are both PMOS transistors (i.e., turned on at low level), the first switching transistor M1 in the detection circuit 3 is NMOS transistor (i.e., turned on at high level), and the symmetric multiprocessor SMP in the detection circuit 3 is also turned on at high level.
In conjunction with fig. 6 and 7, when scanning the pixels of the mth row of the display device, the acquisition phase of the threshold voltage of the driving transistor M5 in the pixel driving circuit 1 of the pixel of the mth row and the nth column includes the following three phases:
stage T1:
at the stage T1, the first controller 7 outputs the first scan control signal S1 with a high level, and the first switch transistor M1 in the detection circuit 3 is turned on. The first controller 7 supplies a low-level control signal to the symmetric multiprocessor SMP, and the symmetric multiprocessor SMP is turned off. The second controller 8 outputs the second scan control signal S2 and the third scan control signal S3 at low levels, and the second switching transistor M2 and the third switching transistor M3 in the pixel driving circuit 1 are both turned on.
The data signal voltage Vdata having a low potential is transmitted to the control terminal of the driving transistor M5, and the initialization voltage is transmitted to the third terminal of the driving transistor M5 and the anode of the light emitting device, at this time, since the initialization voltage is low enough, it is ensured that the driving transistor M5 is turned off, i.e., Vdata-Vdd < Vth, at this time, the channel current of the driving transistor M5 is constant current and the light emitting device does not emit light.
Since the first switch transistor M1 is turned on, the first switch transistor M1 and the operational amplifier OA in the detection circuit 3 together form a voltage follower, and therefore Vout output from the second terminal of the voltage follower is always Vref. And the symmetric multiprocessor SMP is turned off, the voltage output by the second terminal of the operational amplifier OA is not used by the analog-to-digital converter ADC.
The light emitting device does not emit light at the T1 stage.
Stage T2:
at the stage T2, the first controller 7 outputs the first scan control signal S1 with a low level, and the first switch transistor M1 in the detection circuit 3 is turned off. The first controller 7 provides a control signal with a certain varying frequency to the symmetric multiprocessor SMP. The second controller 8 outputs the second scan control signal S2 and the third scan control signal S3 at low levels, and the second switching transistor M2 and the third switching transistor M3 in the pixel driving circuit 1 are both turned on. At the same time, the driving chip 2 gradually raises the data signal voltage Vdata output to the control terminal of the driving transistor M5, as shown in fig. 8.
Since the first switch transistor M1 in the detection circuit 3 is turned off, the operational amplifier OA and the first capacitor C1 together form an integrator, and the voltage at the second terminal of the driving transistor M5 and the voltage at the first terminal of the operational amplifier OA change once each time the data signal voltage Vdata rises, and the voltage at the first terminal of the operational amplifier OA (i.e., Vdata-Vdd-Vth) changes over time because the data signal voltage Vdata changes over time, the integrator integrates the voltage at the first terminal of the operational amplifier OA, the voltage output by the second terminal (i.e., the output terminal) of the operational amplifier OA is proportional to the time integral of the voltage at the first terminal of the operational amplifier OA, and the time change of Vout is shown in fig. 8. Every time the data signal voltage Vdata rises once, the symmetric multiprocessor SMP and the analog-digital converter ADC cooperate to sample the voltage Vout output from the output terminal of the operational amplifier OA once, and then the analog-digital converter ADC converts Vout into a digital signal Code and transmits the digital signal Code to the driver chip 2.
The driving chip 2 compares the received digital signal codes, and when the digital signal codes received by two adjacent samples are equal or close to each other, the channel current in the pixel driving circuit 1 is determined to be zero, that is, Vdata-Vdd-Vth is 0, and the data signal voltage Vdata sampled this time is recorded. And calculates the threshold voltage of the driving transistor M5, i.e., Vth — Vdd.
At the T2 stage, the voltage at the second terminal of the driving transistor M5 is zero at the end of the T2 stage, and is smaller than zero until then, so that the light emitting device does not emit light at T2.
Stage T3:
at the stage T3, the first controller 7 outputs the first scan control signal S1 with a high level, and the first switch transistor M1 in the detection circuit 3 is turned on. The first controller 7 provides a high level to the symmetric multiprocessor SMP, which is turned on. The second controller 8 outputs the second scan control signal S2 and the third scan control signal S3 at a high level, and both the second switching transistor M2 and the third switching transistor M3 in the pixel driving circuit 1 are turned off.
Since the first switching transistor M1 and the second switching transistor M2 are both off and the first switching transistor M1 is on, the voltage at the second terminal of the driving transistor M5, i.e., the anode voltage of the display device, is an initialization voltage, and the initialization voltage is sufficiently low, so that the light emitting device does not emit light.
Since the first switch transistor M1 is turned on, the first switch transistor M1 and the operational amplifier OA in the detection circuit 3 together form a voltage follower, and therefore Vout output from the second terminal of the voltage follower is always Vref. And the symmetric multiprocessor SMP is turned off, the voltage output by the second terminal of the operational amplifier OA is not used by the analog-to-digital converter ADC.
The light emitting device does not emit light at the T3 stage.
Through the above stages T1, T2, and T3, the threshold voltage of the driving transistor M5 in the pixel driving circuit 1 for driving a pixel can be obtained, and in the subsequent stage of driving the light emitting device to emit light, the threshold voltage can be used for the display compensation operation of the pixel, so that the current of the light emitting device is independent of the threshold voltage of the driving transistor M5, and therefore, the light emitting luminance of each pixel can be uniform, and the uniformity of the light emitting luminance of the display screen can be increased. The light emitting device does not emit light during the whole process of detecting the threshold voltage of the driving transistor M5, so the process of detecting the threshold voltage of the driving transistor M5 does not affect the light emission of the display panel.
It should be understood that the switching transistors provided in the above embodiments of the present invention, for example, the second switching transistor M2 and the third switching transistor M3 are both PMOS transistors, and the third voltage amplitude is a low level voltage value and the fourth voltage amplitude is a high level voltage value. Similarly, those skilled in the art may also divide the plurality of switching transistors in the pixel driving circuit 1 into PMOS transistors and NMOS transistors, and the voltage amplitude applied to the corresponding transistors varies with the kind of crystal light, for example, in the same pixel driving circuit 1, if the second switching transistor M2 is a PMOS transistor, the third voltage amplitude applied to the second switching transistor M2 is a low-level voltage value; if the third switching transistor M3 is an NMOS transistor, the third voltage amplitude applied to the third switching transistor M3 is a high level voltage. Therefore, the present invention does not limit the kinds of the switching transistors in the pixel driving circuit 1 and the magnitudes of the signal voltages applied to the respective switching transistors.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the invention, so that any modifications, equivalents and the like included in the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (8)
1. A display device characterized by comprising:
the pixel driving circuit is used for driving pixels in the display device to emit light and comprises a driving transistor, wherein a first end of the driving transistor receives a power supply voltage;
the driving chip is used for providing data signal voltage for a driving transistor in the pixel driving circuit; and the number of the first and second groups,
the input end of the detection circuit is electrically connected with the second end of the driving transistor in the pixel driving circuit, the output end of the detection circuit outputs a digital signal, and the digital signal reflects the channel current of the driving transistor;
wherein the driver chip is further configured to: receiving the digital signal output by the detection circuit, and calculating and storing the threshold voltage of the driving transistor according to the digital signal;
wherein, the detection circuit includes:
a first switching transistor, a first terminal of the first switching transistor being electrically connected to the second terminal of the driving transistor;
a first capacitor connected in parallel with the first switching transistor;
the first end of the operational amplifier is electrically connected with the first end of the first capacitor, the second end of the operational amplifier is connected with the second end of the first capacitor, and the third end of the operational amplifier receives an initialization voltage;
a symmetric multiprocessor, a first end of the symmetric multiprocessor being electrically connected to a second end of the operational amplifier;
a first end of the analog-to-digital converter is electrically connected with a second end of the symmetric multiprocessor, the second end of the analog-to-digital converter is an output end, and the output end outputs the digital signal; and the number of the first and second groups,
a first controller for providing a first scan control signal to the first switching transistor and the symmetric multiprocessor, wherein the first controller provides a control signal with a certain variation frequency to the symmetric multiprocessor; wherein the first controller is configured to perform the steps of:
transmitting a first scan control signal having a first voltage amplitude to the first switching transistor so that the first switching transistor is turned on; transmitting a control signal having a second voltage magnitude to the symmetric multiprocessor such that the symmetric multiprocessor is turned off;
transmitting a first scan control signal having a second voltage amplitude to the first switching transistor so that the first switching transistor is turned off; transmitting a control signal with a first voltage amplitude to the symmetric multiprocessor to enable the symmetric multiprocessor to be conducted, so that each time the data signal voltage is raised, the voltage output by the output end of the operational amplifier is sampled once through the symmetric multiprocessor and the analog-digital converter; and the number of the first and second groups,
transmitting a first scan control signal having a first voltage amplitude to the first switching transistor so that the first switching transistor is turned on; transmitting a control signal having a second voltage magnitude to the symmetric multiprocessor such that the symmetric multiprocessor is turned off.
2. The display device according to claim 1, wherein the driving chip comprises:
the judging module is used for receiving the digital signal output by the detecting circuit and judging the channel current of the driving transistor according to the digital signal; and the number of the first and second groups,
and the calculating module is used for recording the data signal voltage output by the driving chip when the channel current of the driving transistor is zero, and calculating and storing the threshold voltage of the driving transistor according to the data signal voltage.
3. The display device according to claim 1, wherein the display device comprises: a plurality of pixels distributed in N rows and M rows, wherein M and N are integers greater than or equal to 2; and the number of the first and second groups,
and the multiplexer is used for sequentially electrically communicating the detection circuit with the second ends of the driving transistors in the pixel driving circuits of the pixels in each row of pixels.
4. The display device according to claim 1, wherein the pixel drive circuit comprises:
a light emitting device;
one end of the data storage module is used for receiving power supply voltage, and the other end of the data storage module is electrically connected with the control end of the driving transistor;
one end of the data storage control module receives a data signal voltage, and the other end of the data storage control module is electrically connected with the control end of the driving transistor and the other end of the data storage module respectively; and the number of the first and second groups,
and one end of the initialization module is electrically connected with the second end of the driving transistor and the anode of the light-emitting device respectively, and the other end of the initialization module is electrically connected with the input end of the detection circuit.
5. The display device according to claim 4,
the data storage module comprises a second capacitor, wherein a first end of the second capacitor is used for receiving the power supply voltage, and a second end of the second capacitor is electrically connected with the control end of the driving transistor;
the data storage control module comprises a second switch transistor, wherein a first end of the second switch transistor receives the data signal voltage, and a second end of the second switch transistor is electrically connected with a control end of the driving transistor and a second end of the second capacitor respectively;
the initialization module comprises a third switching transistor, wherein the first end of the third switching transistor is electrically connected with the second end of the driving transistor, and the second end of the third switching transistor is electrically connected with the input end of the detection circuit.
6. The display device according to claim 5, further comprising:
and the scanning control line is respectively and electrically connected with the control end of the second switching transistor and the control end of the third switching transistor and is used for transmitting scanning control signals for the second switching transistor and the third switching transistor.
7. The display device according to claim 6, wherein the scan control line comprises:
the first scanning control line is electrically connected with the control end of the second switching transistor and is used for transmitting a second scanning control signal to the second switching transistor; and the number of the first and second groups,
and the second scanning control line is electrically connected with the control end of the third switching transistor and is used for transmitting a third scanning control signal to the third switching transistor.
8. The display device according to claim 6, further comprising:
a second controller having one end electrically connected to the scan control line for providing the scan control signal to the scan control line, wherein the second controller is configured to perform the following steps:
transmitting a scan control signal having a third voltage amplitude to the control terminal of the second switching transistor and the control terminal of the third switching transistor so that the second switching transistor and the third switching transistor are both turned on;
transmitting a scan control signal having a third voltage amplitude to a control terminal of a second switching transistor and a control terminal of a third switching transistor, such that the second switching transistor and the third switching transistor are both turned on; and the number of the first and second groups,
transmitting a scan control signal having a fourth voltage amplitude to a control terminal of a second switching transistor and a control terminal of the third switching transistor such that the second switching transistor and the third switching transistor are both turned off.
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| CN114067722A (en) * | 2020-08-06 | 2022-02-18 | 深圳市柔宇科技股份有限公司 | Pixel driving circuit, display panel and pixel driving method |
| CN112542138A (en) * | 2020-12-25 | 2021-03-23 | 深圳市华星光电半导体显示技术有限公司 | Pixel driving circuit and display device |
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| KR102056784B1 (en) * | 2013-08-30 | 2020-01-22 | 엘지디스플레이 주식회사 | Organic light emitting display device |
| KR101597037B1 (en) * | 2014-06-26 | 2016-02-24 | 엘지디스플레이 주식회사 | Organic Light Emitting Display For Compensating Electrical Characteristics Deviation Of Driving Element |
| KR101529005B1 (en) * | 2014-06-27 | 2015-06-16 | 엘지디스플레이 주식회사 | Organic Light Emitting Display For Sensing Electrical Characteristics Of Driving Element |
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| US10283051B2 (en) * | 2017-09-06 | 2019-05-07 | Shenzhen China Star Optoelectronics Semiconductor Display Technology Co., Ltd. | OLED pixel driving circuit and OLED display device |
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| CN108877685B (en) * | 2018-07-20 | 2020-05-05 | 深圳市华星光电半导体显示技术有限公司 | OLED pixel driving circuit and OLED display device |
| CN109935182B (en) * | 2018-07-27 | 2020-07-17 | 京东方科技集团股份有限公司 | Pixel current detection circuit, method and display device |
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