CN113421525B - Pixel driving circuit, display panel, display device and driving control method - Google Patents
Pixel driving circuit, display panel, display device and driving control method Download PDFInfo
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- CN113421525B CN113421525B CN202110687852.2A CN202110687852A CN113421525B CN 113421525 B CN113421525 B CN 113421525B CN 202110687852 A CN202110687852 A CN 202110687852A CN 113421525 B CN113421525 B CN 113421525B
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
- G09G3/3258—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the voltage across the light-emitting element
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3266—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
- 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
Abstract
The application discloses a pixel driving circuit, a display panel, a display device and a driving control method. The pixel driving circuit comprises a driving transistor, a data writing transistor, a storage capacitor, a first transistor and a voltage regulating module. The voltage regulating module is used for regulating the grid voltage of the driving transistor so that the driving current of the driving transistor in a saturation state is independent of the threshold voltage of the driving transistor. The second pole of the first transistor is connected with a reference signal end, the reference signal end is used for providing a first reference signal or a second reference signal, and the potential of the first reference signal is smaller than that of the second power supply end. The pixel driving circuit can effectively compensate the threshold voltage of the driving transistor, can realize the voltage reversal of the organic light emitting diode, and realizes the light emission of the alternating current driving organic light emitting diode, thereby reducing the threshold voltage drift amount of the organic light emitting diode and prolonging the service life of the organic light emitting diode.
Description
Technical Field
The present disclosure relates to the field of organic light emitting display technologies, and in particular, to a pixel driving circuit, a display panel, a display device, and a driving control method.
Background
An Organic Light-Emitting Diode (OLED) display device has many advantages of self-luminescence, low driving voltage, high Light-Emitting efficiency, short response time, and capability of realizing flexible display and large-area full-color display. The OLED display device may be classified into two types, i.e., a Passive Matrix OLED (PMOLED) and an Active Matrix OLED (AMOLED), according to a driving method. The AMOLED has pixels arranged in an array, belongs to an active display type, has high light emitting efficiency, and is generally used as a large-sized display device with high definition. The AMOLED is a current driving device, so the pixel driving circuit of the AMOLED needs to complete the task of converting the voltage signal into the current signal. A conventional AMOLED pixel driving circuit is generally 2T1C, i.e. a structure of two transistors plus one capacitor.
The conventional 2T1C pixel driving circuit is sensitive to the threshold voltage drift of the driving transistor and the organic light emitting diode, and the current flowing through the organic light emitting diode changes greatly along with the threshold voltage drift of the driving transistor and the organic light emitting diode, which not only causes unstable light emission and uneven brightness of the organic light emitting diode, but also greatly affects the display effect of the picture.
Disclosure of Invention
In view of the above, the present invention is directed to solving, at least to some extent, one of the problems in the related art. To this end, an object of the present application is to provide a pixel driving circuit, a display panel, a display device, and a drive control method.
The embodiment of the application provides a pixel driving circuit. The pixel driving circuit includes: the device comprises a driving transistor, a data writing transistor, a storage capacitor, a voltage regulating module and a first transistor. The first electrode of the driving transistor is connected with a first power supply end, the second electrode of the driving transistor is connected with the first electrode of the organic light-emitting diode, the second electrode of the organic light-emitting diode is connected with a second power supply end, and the driving transistor is used for generating driving current according to the voltage of the grid electrode of the driving transistor so as to drive the organic light-emitting diode; the grid electrode of the data writing transistor is connected with a first control signal end, and the first pole of the data writing transistor is connected with a data signal end; the storage capacitor is connected with the grid electrode and the second pole of the driving transistor; the voltage regulating module is connected with a second control signal end, a third control signal end, a second pole of the data writing transistor, a grid of the driving transistor and the first power supply end, and is used for regulating the grid voltage of the driving transistor so that the driving current of the driving transistor in a saturation state is independent of the threshold voltage of the driving transistor; the first electrode of the first transistor is connected with the first electrode of the light emitting diode, the grid electrode of the first transistor is connected with a fourth control signal end, the second electrode of the first transistor is connected with a reference signal end, the reference signal end is used for providing a first reference signal or a second reference signal, and the potential of the first reference signal is smaller than that of the second power supply end.
In some embodiments, the voltage regulation module comprises: a coupling capacitor, a second transistor and a third transistor. The coupling capacitor is connected with the second pole of the data writing transistor and the grid electrode of the driving transistor; a first electrode of the second transistor is connected with the first power supply end, a first electrode of the second transistor is connected with a first electrode of the driving transistor, and a grid electrode of the second transistor is connected with a second control signal end; a first pole of the third transistor is connected to the gate of the driving transistor, a second pole of the third transistor is connected to the second pole of the driving transistor, and the gate of the third transistor is connected to the third control signal terminal.
In some embodiments, the voltage regulating module includes a fourth transistor, a first pole of the fourth transistor is connected to the second pole of the data writing transistor, a second pole of the third transistor is grounded, and a gate of the fourth transistor is connected to the third control signal terminal.
In some embodiments, the data writing transistor, the first transistor, the second transistor, the third transistor, and the fourth transistor are all N-channel transistors.
In some embodiments, the potential of the second reference signal is equal to the potential of the second power supply terminal.
The embodiment of the application also provides a display panel. The display panel comprises a plurality of sub-pixels arranged in an array, each sub-pixel comprises a light emitting diode and the pixel driving circuit of any one of the above embodiments, and the pixel driving circuit is configured to drive the light emitting diode.
In some embodiments, the display panel includes a gate driving circuit connected to the first control signal terminal, the second control signal terminal, the third control signal terminal, and the fourth control signal terminal of the pixel driving circuit, respectively.
In some embodiments, the gate driving circuit provides a first control signal, a second control signal, a third control signal and a fourth control signal for the pixel driving circuits in the same row through the first control signal terminal, the second control signal terminal, the third control signal terminal and the fourth control signal terminal, respectively.
The embodiment of the application also provides a display device. The display device comprises the display panel of any one of the above embodiments.
The present embodiment further provides a driving control method for controlling the pixel driving circuit according to any one of the above embodiments. The drive control method includes: in a precharge phase, providing a first level to the first control signal terminal, providing a second level to the second control signal terminal, the third control signal terminal, and the fourth control signal terminal, and providing the first reference signal to the reference signal terminal; in a threshold voltage latch phase, providing a first level to the first control signal terminal and the second control signal terminal, providing a second level to the third control signal terminal and the fourth control signal terminal, and providing the second reference signal to the reference signal terminal, so that a voltage across the storage capacitor is equal to a threshold voltage of the driving transistor; in a data writing phase, providing a first level to the second control signal terminal and the third control signal terminal, providing a second level to the first control signal terminal and the fourth control signal terminal, providing a data signal to the data signal terminal, and providing the second reference signal to the reference signal terminal; in a light emitting stage, providing a second level to the second control signal terminal, and providing a first level to the first control signal terminal, the third control signal terminal and the fourth control signal terminal; the first level is used for controlling the transistor to be switched off, and the second level is used for controlling the transistor to be switched on.
The pixel driving circuit can effectively compensate the threshold voltage of the driving transistor, can realize the voltage reversal of the organic light-emitting diode, and realizes the light emission of the alternating current driving organic light-emitting diode, thereby reducing the threshold voltage drift amount of the organic light-emitting diode and prolonging the service life of the organic light-emitting diode.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic diagram of an AMOLED pixel driving circuit in some embodiments;
FIG. 2 is a schematic diagram of a pixel driving circuit according to some embodiments of the present disclosure;
FIG. 3 is a schematic diagram of a pixel driving circuit according to some embodiments of the present disclosure;
FIG. 4 is a flow chart illustrating a driving control method of a pixel driving circuit according to some embodiments of the present disclosure;
FIG. 5 is a signal timing diagram illustrating a driving control method of a pixel driving circuit according to some embodiments of the present disclosure;
FIG. 6 is a circuit diagram of a pixel driving circuit during a period t1 according to some embodiments of the present disclosure;
FIG. 7 is a circuit diagram of a pixel driving circuit during a t2 phase of a driving control method according to some embodiments of the present application;
fig. 8 is a circuit diagram of a pixel driving circuit at the stage t3 of the driving control method according to some embodiments of the present application;
fig. 9 is a circuit diagram of a pixel driving circuit at the time of a t4 stage in the driving control method according to some embodiments of the present application;
FIG. 10 is a schematic diagram of a display panel according to some embodiments of the present application;
fig. 11 is a schematic structural diagram of a display device according to some embodiments of the present application.
Detailed Description
Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative and are only for the purpose of explaining the present application and are not to be construed as limiting the present application.
In the description of the present application, it is to be understood that the terms "first", "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present application, "a plurality" means two or more unless specifically defined otherwise.
In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
The following disclosure provides many different embodiments or examples for implementing different features of the application. In order to simplify the disclosure of the present application, specific example components and arrangements are described below. Of course, they are merely examples and are not intended to limit the present application. Moreover, the present application may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative and are only for the purpose of explaining the present application and are not to be construed as limiting the present application.
The AMOLED is a current driving device, so the pixel driving circuit of the AMOLED needs to complete the task of converting the voltage signal into the current signal. The conventional AMOLED pixel driving circuit is usually 2T1C, as shown in fig. 1, that is, a structure of adding a capacitor to two transistors converts voltage into current, when the AMOLED displays, a Scan signal Scan controls a first P-type transistor S-TFT to be turned on, a data signal Vdata enters a gate electrode of a second P-type thin film transistor DTFT and a capacitor Cst through the S-TFT, and then the S-TFT is turned on.
The conventional 2T1C pixel driving circuit is sensitive to the threshold voltage shift of the driving transistor and the organic light emitting diode, and the current flowing through the organic light emitting diode varies greatly along with the threshold voltage shift of the driving transistor and the organic light emitting diode, so that the light emission of the organic light emitting diode is unstable, the brightness is non-uniform, and the display effect of the picture is greatly influenced. In addition, since the organic light emitting diode is driven by direct current for a long time, the life of the organic light emitting diode also has a certain influence.
In view of the above, referring to fig. 2, the present embodiment provides a pixel driving circuit 10. The pixel drive circuit 10 includes: the driving circuit comprises a driving transistor T2, a data writing transistor T1, a storage capacitor C2, a voltage regulating module 11 and a first transistor T4.
A first electrode of the driving transistor T2 is connected to the first power source terminal VDD, a second electrode of the driving transistor T2 is connected to a first electrode of the organic light emitting diode L1, and a second electrode of the organic light emitting diode L1 is connected to the second power source terminal VSS. The driving transistor T2 is used to generate a driving current according to a voltage of the gate of the driving transistor T2 to drive the organic light emitting diode L1.
The gate of the data writing transistor T1 is connected to the first control signal terminal Scan1, and the first pole of the data writing transistor T1 is connected to the data signal terminal data.
The storage capacitor C2 connects the gate and the second pole of the driving transistor T2.
The voltage regulating module 11 is connected to the second control signal terminal EM, the third control signal terminal Scan2, the second pole of the data writing transistor T1, the gate of the driving transistor T2, and the first power supply terminal VDD. The voltage regulating module 11 is configured to regulate the gate voltage V1 of the driving transistor T2, so that the driving current of the driving transistor T2 in a saturation state is independent of the threshold voltage (Vth) of the driving transistor T2, and the threshold voltage compensation of the driving transistor T2 and the organic light emitting diode L1 is implemented, so that the current flowing through the organic light emitting diode L1 becomes independent of the threshold voltage (Vth) of the driving transistor T2, and the organic light emitting diode L1 is stable in light emission and uniform in brightness, thereby improving the display effect of the OLED display device.
As shown in fig. 3, the voltage regulating module 11 specifically includes: a coupling capacitor C1, a second transistor T6, and a third transistor T5. The coupling capacitor C1 connects the second pole of the data writing transistor T1 and the gate of the driving transistor T2. A first electrode of the second transistor T6 is connected to the first power terminal VDD, a second electrode of the second transistor T6 is connected to the first electrode of the driving transistor, and a gate electrode of the second transistor T6 is connected to the second control signal terminal EM. A first pole of the third transistor T5 is connected to the gate electrode of the driving transistor T2, a second pole of the third transistor T5 is connected to the first pole of the driving transistor T2, and a gate electrode of the third transistor T5 is connected to the third control signal terminal Scan2.
The voltage regulating module 11 further includes a fourth transistor T3, a first pole of the fourth transistor T3 is connected to a second pole of the data writing transistor T1, a second pole of the fourth transistor T3 is grounded, and a gate of the fourth transistor T3 is connected to the third control signal terminal Scan2.
The pixel driving circuit adjusts the gate voltage V1 of the driving transistor T2 connected with the storage capacitor C2 through the voltage adjusting module 11, so that the driving current of the driving transistor T2 in the pixel driving circuit in a saturated state is independent of the threshold voltage Vth of the driving transistor T2, and therefore the threshold voltage Vth of the driving transistor T2 cannot influence the current flowing through the organic light emitting diode L1, the consistency of the driving current I is better guaranteed, and the luminance uniformity of the pixel driving circuit driving the organic light emitting diode L1 to emit light is good.
A first pole of the first transistor T4 is connected to a first pole of the light emitting diode, a gate of the first transistor T4 is connected to the fourth control signal terminal Scan3, a second pole of the first transistor is connected to a reference signal terminal REF, the reference signal terminal REF is used for providing a first reference signal or a second reference signal, a potential of the first reference signal is less than a potential of the second power terminal VSS, and the second power terminal VSS is a ground terminal. By arranging the first transistor T4 and enabling the potential of the first reference signal to be smaller than that of the second power supply terminal VSS, for example, the potential of the second power supply terminal VSS can be 0V, the potential of the first reference signal can be smaller than 0 and is a negative value, and each frame of display picture of the OLED display device is provided with anode voltage reverse setting time, so that the OLED L1 is driven by alternating current to emit light, the OLED L1 is not driven by direct current for a long time, the threshold voltage drift amount of the OLED L1 can be reduced, and the service life of the OLED L1 is prolonged.
After the Organic Light Emitting Diode (OLED) has elapsed a certain period of inversion time, a second reference signal may be input at the reference signal terminal REF, the potential of the second reference signal being equal to the potential of the second power source terminal VSS. That is, the potential of the second reference signal is 0V.
It should be noted that the data writing transistor T1, the first transistor T4, the second transistor T6, the third transistor T5, and the fourth transistor T3 are all N-channel transistors. The N-channel transistor may be turned on by a high level signal and turned off by a low level signal. In the pixel driving circuit of the present application, the data writing transistor T1, the first transistor T4, the second transistor T6, the third transistor T5, and the fourth transistor T3 are switching transistors for opening or closing a circuit connection.
The pixel driving circuit can effectively compensate the threshold voltage of the driving transistor, can realize the voltage reversal of the light emitting diode, and realizes the light emitting of the alternating current driving organic light emitting diode, thereby reducing the threshold voltage drift amount of the organic light emitting diode and prolonging the service life of the organic light emitting diode.
The structure of the pixel driving circuit is introduced, and now, a driving control method for controlling the pixel driving circuit is introduced to realize that each frame of display picture of the OLED display device is provided with an anode voltage inversion time, so that alternating current drive of the Organic Light Emitting Diode (OLED) is realized, the Organic Light Emitting Diode (OLED) is not driven by direct current for a long time, the drift amount of the threshold voltage of the Organic Light Emitting Diode (OLED) can be reduced, and the service life of the Organic Light Emitting Diode (OLED) is prolonged.
Referring to fig. 4, the present application further provides a driving control method for controlling the pixel driving circuit 10, the driving control method includes:
s12: in the precharge phase, a first level is supplied to the first control signal terminal Scan1, a second level is supplied to the second control signal terminal EM, the third control signal terminal Scan2, and the fourth control signal terminal Scan3, and a first reference signal is supplied to the reference signal terminal REF;
s14: in the threshold voltage latch phase, a first level is provided to the first control signal terminal Scan1 and the second control signal terminal EM, a second level is provided to the third control signal terminal Scan2 and the fourth control signal terminal Scan3, and a second reference signal is provided to the reference signal terminal REF, so that the voltage across the storage capacitor C2 is equal to the threshold voltage of the driving transistor T2;
s16: in the data write phase, a first level is supplied to the second control signal terminal EM and the third control signal terminal Scan2, a second level is supplied to the first control signal terminal Scan1 and the fourth control signal terminal Scan3, a data signal is supplied to the data signal terminal, and a second reference signal is supplied to the reference signal terminal REF;
s18: in the light emitting phase, a second level is provided to the second control signal terminal EM, and a first level is provided to the first control signal terminal Scan1, the third control signal terminal Scan2 and the fourth control signal terminal Scan 3;
the first level is used for controlling the transistor to be switched off, and the second level is used for controlling the transistor to be switched on.
Specifically, referring to fig. 5, the working phase of the pixel driving circuit in each frame of the display screen is sequentially divided into four timings t1, t2, t3, and t4. It should be noted that the signal at the reference signal terminal REF is a first reference signal during the period t1, where the first reference signal may be a negative voltage REF, and is maintained as a second reference signal during the period t2 to t4, where the second reference signal may be a voltage of 0V. When the signals of the second control signal terminal EM, the first control signal terminal Scan1, the third control signal terminal Scan2 and the fourth control signal terminal Scan3 are at the second level, the corresponding transistors may be controlled to be turned on. When the signals of the second control signal terminal EM, the first control signal terminal Scan1, the third control signal terminal Scan2 and the fourth control signal terminal Scan3 are at the first level, the corresponding transistors may be controlled to be turned off.
In an example of the present application, the switching transistor of the pixel drive circuit is an N-channel transistor, the first level is a low level, and the second level is a high level.
It should be noted that, when the switching transistor of the pixel driving circuit is a P-channel transistor, the first level may also be a high level, and the second level may also be a low level, and those skilled in the art may also design the type of each switching transistor in the pixel driving circuit according to actual needs, and accordingly, the potentials of the first level and the second level may be changed as needed.
Referring to fig. 5 and 6, during the pre-charge period t1 (or referred to as an inversion period), a first level is provided to the first control signal terminal Scan1, a second level is provided to the second control signal terminal EM, the third control signal terminal Scan2 and the fourth control signal terminal Scan3, and a first reference signal (a negative voltage REF) is provided to the reference signal terminal REF. At this time, the first level is low, for example, the first level is 0V or a negative voltage, and the data writing transistor T1 controlled by the first control signal terminal Scan1 correspondingly may be controlled to be turned off. The second level is a high level, for example, a voltage greater than 0V, and may control the second transistor T6 controlled by the second control signal terminal EM to be turned on, the fourth transistor T3 and the third transistor T5 controlled by the third control signal terminal Scan2 to be turned on, and the first transistor T4 controlled by the fourth control signal terminal Scan3 to be turned on, where the turning on is an on state.
Specifically, as shown in fig. 6, when the fourth transistor T3, the first transistor T4, the third transistor T5, and the second transistor T6 are turned on and the data writing transistor T1 is turned off, VC =0, vb = vdd, va = ref is known, and when the Vref voltage (which is a negative voltage) is much lower than the pixel cathode voltage VSS (0V), the voltage inversion of the organic light emitting diode is realized, and the voltage at the point B is precharged. Therefore, the pixel driving circuit can realize the voltage inversion of the organic light emitting diode at the stage t1, and can realize that the organic light emitting diode needs to be driven to emit light by alternating current before the next frame of display picture is carried out, thereby reducing the threshold voltage drift amount of the organic light emitting diode and prolonging the service life of the organic light emitting diode.
Referring to fig. 5 and 7, in the threshold voltage latch phase T2, a first level is provided to the first control signal terminal Scan1 and the second control signal terminal EM, a second level is provided to the third control signal terminal Scan2 and the fourth control signal terminal Scan3, and a second reference signal (as can be seen from the foregoing, the potential of the second reference signal can be 0V) is provided to the reference signal terminal REF, so that the voltage across the storage capacitor C2 is equal to the threshold voltage Vth of the driving transistor T2.
Specifically, as shown in fig. 7, at this time, the data writing transistor T1 is continuously controlled to be turned off, and the second transistor T6 is controlled to be turned off, and since the voltage of the reference signal terminal REF changes, it becomes controlled by the potential 0V of the second reference signal that the voltage of the reference signal terminal REF outputs 0V, that is, the voltage at the a point becomes 0V, and va =0V. The B-point charge is discharged through the driving transistor T2, and finally VB = Vth, and the threshold voltage (Vth) of the driving transistor T2 is locked. While the voltage at point C remains 0V, i.e., VC =0, the coupling capacitance C1 writes the voltage difference of Vth.
Referring to fig. 5 and 8, in the data writing phase t3, a first level is provided to the second control signal terminal EM and the third control signal terminal Scan2, a second level is provided to the first control signal terminal Scan1 and the fourth control signal terminal Scan3, a data signal Vdata is provided to the data signal terminal data, and a second reference signal (as can be seen from the foregoing, the potential of the second reference signal is 0V) is provided to the reference signal terminal REF.
Specifically, as shown in fig. 8, the second transistor T6 is turned off when the first level is supplied to the second control signal terminal EM. When the first level is supplied to the third control signal terminal Scan2, the fourth transistor T3 and the third transistor T5 are both turned off, and VA is maintained at 0v, the data signal is written through the data writing transistor T1, VC = Vdata, and VB = Vth + Vdata due to the capacitive coupling effect of the coupling capacitor C1. Meanwhile, VA =0V since the point a maintains a voltage of 0V. The voltage difference across the capacitor C2 is VB-VA = Vth + Vdata, and can be maintained until the next frame signal arrives.
The capacitive coupling is also called electric field coupling or electrostatic coupling, and is a coupling mode generated due to the existence of distributed capacitance. Coupling refers to the process by which a signal passes from a first stage to a second stage.
Referring to fig. 5 and 9, next, in the light emitting period t4, the second level is provided to the second control signal terminal EM, and the first level is provided to the first control signal terminal Scan1, the third control signal terminal Scan2 and the fourth control signal terminal Scan3.
Note that, in the light-emitting period t4, the organic light-emitting diode in the pixel driving circuit is in a light-emitting state, and in the first three periods t1 to t3, the organic light-emitting diode is not in a light-emitting state.
Specifically, as shown in fig. 9, at this time, the data writing transistor T1, the fourth transistor T3, the first transistor T4, and the third transistor T5 are turned off, the driving transistor T2 and the second transistor T6 are turned on, and the voltage signal VDD inputted from the first power source terminal supplies power to the organic light emitting diode through the driving transistor T2, thereby controlling the organic light emitting diode to emit light.
Here, the current flowing into the organic light emitting diode at this time is explained as follows.
From the above findings, the current flowing through the organic light emitting diode is as follows (where μ n, cox are intrinsic constants of the TFT device). In the above stage, the voltage difference between the two ends of the capacitor C2 is VB-VA = Vth + Vdata, and therefore,
from this, the current I DS The organic light emitting diode is not influenced by the voltage at the point A and the threshold voltage Vth of the driving transistor T2, and is only related to the data signal Vdata provided by the data signal terminal data, so that the compensation of the threshold voltage Vth of the driving transistor can be realized, the current flowing through the organic light emitting diode is unrelated to the threshold voltage of the driving transistor, and the light emitting of the organic light emitting diode is stable and the brightness is uniform.
Meanwhile, the drive control method can control the pixel drive circuit to realize the reverse arrangement of the voltage of the organic light emitting diode at the t1 stage, can realize that the organic light emitting diode is subjected to alternating current drive before each frame of pixel display, does not continuously perform direct current drive on the organic light emitting diode all the time, can effectively reduce the drift amount of the threshold voltage of the organic light emitting diode, and prolongs the service life of the organic light emitting diode.
It can be understood that, when the driving transistor T2 is always used to drive the organic light emitting diode with dc, the drift amount of the threshold voltage of the organic light emitting diode increases with the time of dc driving, so that the ac driving time of T1 time is increased in the dc driving process, which can effectively reduce the drift amount of the threshold voltage of the light emitting diode.
Referring to fig. 10, the present application further provides a display panel 100. The display panel 100 includes a plurality of sub-pixels arranged in an array, each sub-pixel includes a light emitting diode L1 and the pixel driving circuit 10 described above, and the pixel driving circuit 10 is configured to drive the light emitting diode L1.
The display panel 100 includes a gate driving circuit 20, and the gate driving circuit 20 is respectively connected to a first control signal terminal Scan1, a second control signal terminal EM, a third control signal terminal Scan2, and a fourth control signal terminal Scan3 of the pixel driving circuit 10.
The gate driving circuit 20 provides the first control signal, the second control signal, the third control signal and the fourth control signal to the pixel driving circuits 10 in the same row through the first control signal terminal Scan1, the second control signal terminal EM, the third control signal terminal Scan2 and the fourth control signal terminal Scan3, respectively. Specifically, the first control signal provided by the first control signal terminal Scan1 may control the data writing transistor T1 to be turned on or off; the second control signal provided by the second control signal terminal EM may control the second transistor T6 to be turned on or off; the third control signal provided by the third control signal terminal Scan2 may control the third transistor T5 and the fourth transistor T3 to be turned on or off; the third control signal provided by the fourth control signal terminal Scan3 can control the first transistor T4 to be turned on or off.
The pixel driving circuit 10 of the display panel 100 of the present application can compensate for the threshold voltage of the driving transistor, so that the current flowing through the organic light emitting diode becomes independent of the threshold voltage of the driving transistor, the light emission of the organic light emitting diode is stable, the brightness is uniform, the voltage inversion of the light emitting diode can be realized, and the light emission of the alternating current driving light emitting diode L1 is realized, thereby reducing the threshold voltage drift amount of the light emitting diode L1, and improving the service life of the light emitting diode L1 in the display panel 100.
Referring to fig. 11, the present application further provides a display device 200. The display device 200 comprises the display panel 100 described above. The display device 200 of the present application can compensate the threshold voltage of the driving transistor through the pixel driving circuit, so that the current flowing through the organic light emitting diode becomes irrelevant to the threshold voltage of the driving transistor, the light emission of the organic light emitting diode is stable, the brightness is uniform, the voltage inversion of the light emitting diode can be realized, the light emission of the alternating current driving light emitting diode is realized, the threshold voltage drift amount of the light emitting diode is reduced, and the service life of the light emitting diode in the display device 200 is prolonged.
The above examples only express several embodiments of the present application, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the present application. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A pixel driving circuit, comprising:
the driving transistor, the first pole of the driving transistor is connected with the first power end, the second pole of the driving transistor is connected with the first pole of the organic light emitting diode, the second pole of the organic light emitting diode is connected with the second power end, and the driving transistor is used for generating driving current according to the voltage of the grid electrode of the driving transistor so as to drive the organic light emitting diode;
the grid electrode of the data writing transistor is connected with a first control signal end, and the first pole of the data writing transistor is connected with a data signal end;
a storage capacitor connected to the gate and the second pole of the driving transistor;
the voltage regulating module is connected with a second control signal end, a third control signal end, a second pole of the data writing transistor, a grid of the driving transistor and the first power supply end, and is used for regulating the grid voltage of the driving transistor so that the driving current of the driving transistor in a saturation state is independent of the threshold voltage of the driving transistor;
a first transistor, a first pole of the first transistor is connected with a first pole of the light emitting diode, a gate of the first transistor is connected with a fourth control signal terminal, a second pole of the first transistor is connected with a reference signal terminal, the reference signal terminal is used for providing a first reference signal in a pre-charging stage of the pixel driving circuit and providing a second reference signal in a threshold voltage latching stage and a data writing stage, and the potential of the first reference signal is smaller than that of the second power supply terminal.
2. The pixel driving circuit according to claim 1, wherein the voltage regulating module comprises:
a coupling capacitor connecting the second pole of the data writing transistor and the gate of the driving transistor;
a first electrode of the second transistor is connected with the first power supply end, a second electrode of the second transistor is connected with the first electrode of the driving transistor, and a grid electrode of the second transistor is connected with a second control signal end;
and a third transistor, wherein a first electrode of the third transistor is connected to the gate electrode of the driving transistor, a second electrode of the third transistor is connected to the second electrode of the driving transistor, and a gate electrode of the third transistor is connected to the third control signal terminal.
3. The pixel driving circuit according to claim 2, wherein the voltage regulating module comprises a fourth transistor, a first pole of the fourth transistor is connected to a second pole of the data writing transistor, a second pole of the fourth transistor is connected to ground, and a gate of the fourth transistor is connected to the third control signal terminal.
4. The pixel driving circuit according to claim 3, wherein the data writing transistor, the first transistor, the second transistor, the third transistor, and the fourth transistor are all N-channel transistors.
5. The pixel driving circuit according to claim 1, wherein a potential of the second reference signal is equal to a potential of the second power source terminal.
6. A display panel comprising a plurality of sub-pixels arranged in an array, each of the sub-pixels comprising a light emitting diode and the pixel driving circuit of any one of claims 1 to 5, the pixel driving circuit being configured to drive the light emitting diode.
7. The display panel according to claim 6, wherein the display panel comprises a gate driving circuit, and the gate driving circuit is connected to the first control signal terminal, the second control signal terminal, the third control signal terminal, and the fourth control signal terminal of the pixel driving circuit, respectively.
8. The display panel according to claim 7, wherein the gate driving circuit provides the first control signal, the second control signal, the third control signal and the fourth control signal to the pixel driving circuits in the same row through the first control signal terminal, the second control signal terminal, the third control signal terminal and the fourth control signal terminal, respectively.
9. A display device characterized by comprising the display panel according to any one of claims 6 to 8.
10. A drive control method for controlling the pixel drive circuit according to any one of claims 1 to 5, characterized by comprising:
in a precharge phase, providing a first level to the first control signal terminal, providing a second level to the second control signal terminal, the third control signal terminal, and the fourth control signal terminal, and providing the first reference signal to the reference signal terminal;
in a threshold voltage latch phase, providing a first level to the first control signal terminal and the second control signal terminal, providing a second level to the third control signal terminal and the fourth control signal terminal, and providing the second reference signal to the reference signal terminal, so that a voltage across the storage capacitor is equal to a threshold voltage of the driving transistor;
in a data writing phase, providing a first level to the second control signal terminal and the third control signal terminal, providing a second level to the first control signal terminal and the fourth control signal terminal, providing a data signal to the data signal terminal, and providing the second reference signal to the reference signal terminal;
in a light emitting stage, providing a second level to the second control signal terminal, and providing a first level to the first control signal terminal, the third control signal terminal and the fourth control signal terminal;
the first level is used for controlling the transistor to be switched off, and the second level is used for controlling the transistor to be switched on.
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