CN109448639A - A kind of pixel-driving circuit and its driving method, display device - Google Patents

A kind of pixel-driving circuit and its driving method, display device Download PDF

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Publication number
CN109448639A
CN109448639A CN201811590699.6A CN201811590699A CN109448639A CN 109448639 A CN109448639 A CN 109448639A CN 201811590699 A CN201811590699 A CN 201811590699A CN 109448639 A CN109448639 A CN 109448639A
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China
Prior art keywords
circuit
control
compensation
terminal
driving
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CN109448639B (en
Inventor
陈沫
陈凯
韩飞
李方庆
吴旺娣
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BOE Technology Group Co Ltd
Hefei BOE Display Lighting Co Ltd
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BOE Technology Group Co Ltd
Hefei BOE Display Lighting Co Ltd
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Priority to CN201811590699.6A priority Critical patent/CN109448639B/en
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3266—Details of drivers for scan electrodes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0233—Improving the luminance or brightness uniformity across the screen

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Control Of El Displays (AREA)

Abstract

The present invention discloses a kind of pixel-driving circuit and its driving method, display device, is related to field of display technology, to solve the heterogeneity in display device due to driving circuit, leads to the non-uniform problem of the display brightness of display device.The pixel-driving circuit includes: driving circuit, accumulator, data write circuit, charge-discharge control circuit and compensation circuit, wherein charge-discharge control circuit is used under the control at the first scanning signal end and the second scanning signal end, the connection being turned on or off between the first level signal input terminal and the control terminal of driving circuit is controlled, and controls the connection being turned on or off between the second end of compensation circuit and the control terminal of driving circuit；Compensation circuit is used under the control of the control terminal of driving circuit, controls the connection being turned on or off between the first end of the compensation circuit and the second end of the compensation circuit.Pixel-driving circuit provided by the invention is for driving light-emitting component to show.

Description

Pixel driving circuit, driving method thereof and display device
Technical Field
The invention relates to the technical field of display, in particular to a pixel driving circuit, a driving method thereof and a display device.
Background
An OLED (Organic Light-Emitting Diode) display device has many advantages of self-luminescence, ultra-thinness, fast response speed, high contrast, wide viewing angle, and the like, and is a display device that is receiving much attention at present. As the size of the OLED display device gradually increases, when the large-sized OLED display device is manufactured, the manufactured driving circuit has non-uniformity in electrical parameters such as threshold voltage, mobility, and the like, and the non-uniformity is converted into a current difference and a brightness difference of the OLED display device, so that the display brightness of the display device is not uniform.
Disclosure of Invention
The invention aims to provide a pixel driving circuit, a driving method thereof and a display device, which are used for solving the problem of non-uniform display brightness of a display device caused by non-uniformity of the driving circuit in the display device.
In order to achieve the above purpose, the invention provides the following technical scheme:
a first aspect of the present invention provides a pixel drive circuit for driving a light emitting element to emit light, the pixel drive circuit comprising: the device comprises a driving circuit, an energy storage circuit, a data writing circuit, a charge and discharge control circuit and a compensation circuit; wherein,
the control end of the driving circuit is connected with the first end of the energy storage circuit, the first end of the driving circuit is connected with the first level signal input end, and the second end of the driving circuit is connected with the light-emitting element;
the second end of the energy storage circuit is connected with the second end of the driving circuit;
the data writing circuit is respectively connected with a first scanning signal end, a data signal input end and a first end of the compensation circuit and is used for controlling connection or disconnection between the data signal input end and the first end of the compensation circuit under the control of the first scanning signal end;
the charge and discharge control circuit is respectively connected with the first scanning signal end, the second scanning signal end, the first level signal input end, the second end of the compensation circuit and the control end of the driving circuit, and is used for controlling connection or disconnection between the first level signal input end and the control end of the driving circuit under the control of the first scanning signal end and the second scanning signal end, and controlling connection or disconnection between the second end of the compensation circuit and the control end of the driving circuit;
the control end of the compensation circuit is connected with the control end of the driving circuit, and the compensation circuit is used for controlling connection or disconnection between the first end of the compensation circuit and the second end of the compensation circuit under the control of the control end of the driving circuit.
Optionally, the charge and discharge control circuit includes:
the first charge-discharge electronic circuit is respectively connected with the second scanning signal end, the first level signal input end and the second end of the compensation circuit and is used for controlling connection or disconnection between the first level signal input end and the second end of the compensation circuit under the control of the second scanning signal end;
and the second charging and discharging electronic circuit is respectively connected with the first scanning signal end, the second end of the compensation circuit and the control end of the driving circuit and is used for controlling the connection between the second end of the compensation circuit and the control end of the driving circuit to be switched on or switched off under the control of the first scanning signal end.
Optionally, the first charge-discharge electronic circuit includes a first transistor, a gate of the first transistor is connected to the second scanning signal terminal, a first pole of the first transistor is connected to the first level signal input terminal, and a second pole of the first transistor is connected to the second terminal of the compensation circuit;
the second charge-discharge electronic circuit comprises a second transistor, a grid electrode of the second transistor is connected with the first scanning signal end, a first pole of the second transistor is connected with the second end of the compensation circuit, and a second pole of the second transistor is connected with the control end of the driving circuit.
Optionally, the data writing circuit includes a third transistor, the energy storage circuit includes an energy storage capacitor, the driving circuit includes a driving transistor, and the compensation circuit includes a compensation transistor; wherein,
a gate of the third transistor is connected to the first scan signal terminal, a first pole of the third transistor is connected to the data signal input terminal, and a second pole of the third transistor is connected to the first pole of the compensation transistor;
the first end of the energy storage capacitor is connected with the grid electrode of the driving transistor, and the second end of the energy storage capacitor is connected with the second pole of the driving transistor;
a first pole of the driving transistor is connected with the first level signal input end, and a second pole of the driving transistor is connected with the light-emitting element;
and the grid electrode of the compensation transistor is connected with the grid electrode of the driving transistor, and the second pole of the compensation transistor is connected with the charge and discharge control circuit.
Optionally, the pixel driving circuit further includes:
and the light-emitting control circuit is respectively connected with the light-emitting control end, the second end of the driving circuit and the second level signal input end and is used for controlling the connection between the second end of the driving circuit and the second level signal input end to be switched on or switched off under the control of the light-emitting control end.
Optionally, the light emission control circuit includes a fourth transistor, a gate of the fourth transistor is connected to the light emission control terminal, a first pole of the fourth transistor is connected to the second terminal of the driving circuit, and a second pole of the fourth transistor is connected to the second level signal input terminal.
Based on the technical solution of the pixel driving circuit, a second aspect of the invention provides a display device, which includes the pixel driving circuit.
Based on the technical solution of the pixel driving circuit, a third aspect of the present invention provides a driving method for a pixel driving circuit, for driving the pixel driving circuit, the driving method including: at each of the display periods, the display period,
in a charging period, a first voltage signal is input into a first level signal input end, a charging and discharging control circuit controls and conducts connection between the first level signal input end and a control end of a driving circuit under the control of a first scanning signal end and a second scanning signal end, and the first voltage signal is transmitted to the control end of the driving circuit and stored in an energy storage circuit; a data signal Vdata is input at a data signal input end, under the control of the first scanning signal end, a data writing circuit controls and conducts the connection between the data signal input end and the first end of the compensation circuit, and the data signal Vdata is transmitted to the first end of the compensation circuit; the compensation circuit is changed from the connection between the first end of the compensation circuit and the second end of the compensation circuit to the connection between the first end of the compensation circuit and the second end of the compensation circuit under the control of the control end of the drive circuit;
in a threshold compensation period, the data writing circuit continues to control and conduct the connection between the data signal input end and the first end of the compensation circuit, and transmits the data signal Vdata to the first end of the compensation circuit; under the control of the first scanning signal end and the second scanning signal end, the charge and discharge control circuit controls to disconnect the connection between the first level signal input end and the control end of the driving circuit and controls to connect the second end of the compensation circuit and the control end of the driving circuit; under the control of the control terminal of the driving circuit, the compensation circuit is changed from turning on the connection between the first terminal of the compensation circuit and the second terminal of the compensation circuit to turning off the connection between the first terminal of the compensation circuit and the second terminal of the compensation circuit, the potential of the control terminal of the driving circuit is changed into Vdata + Vth1, and Vth1 is the threshold voltage of the compensation circuit;
in the light emitting period, under the control of the first scanning signal terminal, the data writing circuit controls to disconnect the connection between the data signal input terminal and the first terminal of the compensation circuit; under the control of the first scanning signal end and the second scanning signal end, the charge and discharge control circuit controls to disconnect the connection between the second end of the compensation circuit and the control end of the drive circuit; under the control of the control end of the drive circuit, the drive circuit drives the light-emitting element to emit light.
Optionally, when the charge and discharge control circuit includes a first charge and discharge electronic circuit and a second charge and discharge electronic circuit, the step of controlling and conducting the connection between the first level signal input end and the control end of the driving circuit by the charge and discharge control circuit specifically includes:
under the control of the second scanning signal end, the first charge-discharge electronic circuit controls and conducts the connection between the first level signal input end and the second end of the compensation circuit, and under the control of the first scanning signal end, the second charge-discharge electronic circuit controls and conducts the connection between the second end of the compensation circuit and the control end of the driving circuit;
the step of the charge and discharge control circuit controlling to disconnect the connection between the first level signal input end and the control end of the driving circuit and controlling to connect the second end of the compensation circuit and the control end of the driving circuit specifically comprises:
under the control of the second scanning signal end, the first charge-discharge electronic circuit controls to disconnect the connection between the first level signal input end and the second end of the compensation circuit, and under the control of the first scanning signal end, the second charge-discharge electronic circuit controls to connect the connection between the second end of the compensation circuit and the control end of the driving circuit;
the step of the charge and discharge control circuit controlling to disconnect the connection between the second end of the compensation circuit and the control end of the driving circuit specifically comprises:
and under the control of the first scanning signal end, the second charging and discharging electronic circuit controls to disconnect the second end of the compensation circuit from the control end of the driving circuit.
Optionally, when the pixel driving circuit further includes a light emission control circuit, the driving method further includes:
in the charging period and the threshold compensation period, the light-emitting control circuit controls to conduct the connection between the second end of the drive circuit and the second level signal input end under the control of the light-emitting control end;
in the light emitting period, the light emitting control circuit controls to disconnect the second terminal of the driving circuit from the second level signal input terminal under the control of the light emitting control terminal.
The technical scheme provided by the invention is that a charging and discharging control circuit and a compensating circuit are arranged, the threshold voltage of the compensating circuit and the data signal provided by a data writing circuit are written into the control end of a driving circuit through the cooperation of the charging and discharging control circuit and the compensating circuit, and the threshold voltage of the compensating circuit is very close to the threshold voltage of the driving circuit, so that the driving current generated by the driving circuit is basically irrelevant to the threshold voltage of the driving circuit when the driving circuit drives a light-emitting element, and the problem of uneven display brightness of a display device caused by the nonuniformity of the threshold voltage of the driving circuit in the display device is well avoided.
In addition, in the technical scheme provided by the invention, only the storage function of the energy storage circuit is utilized, and the capacitor boosting circuit is not involved, so that the problem of uneven brightness caused by capacitor difference in different areas in the display device is better avoided.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 is a first basic structure diagram of a pixel driving circuit according to an embodiment of the present invention;
fig. 2 is a second basic structure diagram of a pixel driving circuit according to an embodiment of the invention;
FIG. 3 is a timing diagram of a pixel driving circuit according to an embodiment of the present invention;
fig. 4 is a first specific structural diagram of a pixel driving circuit according to an embodiment of the invention;
fig. 5 is a second specific structural diagram of a pixel driving circuit according to an embodiment of the invention;
fig. 6a to fig. 6c are diagrams illustrating the operation of the pixel driving circuit in one display period according to the embodiment of the present invention.
Reference numerals:
1-data writing circuit, 2-charge and discharge control circuit,
21-a first charge-discharge electronic circuit, 22-a second charge-discharge electronic circuit,
3-energy storage circuit, 4-light-emitting control circuit,
5-a compensation circuit, 6-a drive circuit,
t1-first transistor, T2-second transistor,
t3-third transistor, T4-fourth transistor,
t5-compensation transistor, DTFT-drive transistor,
c1-energy storage capacitor, scan 1-first scanning signal terminal,
scan 2-second Scan signal terminal, data-data signal input terminal,
vd-a first level signal input terminal, Vs-a second level signal input terminal,
EM-emission control terminal, OLED-light emitting element,
p1-charging period, P2-threshold compensation period,
p3-emission period.
Detailed Description
In order to further explain the pixel driving circuit, the driving method thereof and the display device provided by the embodiment of the invention, the following detailed description is made with reference to the accompanying drawings.
Currently, the main ways to drive an OLED display device to emit light are: the control end voltage of a drive circuit in a pixel drive circuit is changed to control the magnitude of drive current generated by the drive circuit, so as to further realize the control of the luminous brightness of a luminous element connected with the output end of the drive circuit, but as the magnitude of the drive current is not only related to the control end voltage of the drive circuit, but also related to the threshold voltage of the drive circuit, and as the size of an OLED device is gradually increased, the manufactured drive circuit has nonuniformity on electrical parameters such as threshold voltage, mobility and the like when the OLED display device is manufactured, therefore, when the OLED display device is driven to display, the nonuniformity of the drive circuit can influence the magnitude of the drive current generated by the drive circuit, so that when the same data signals are input into a plurality of drive circuits with different threshold voltages in the display device, the drive currents generated by the drive circuits with different threshold voltages in a saturation state are different, therefore, the brightness of the light-emitting elements correspondingly driven by different driving circuits is different, and the phenomenon of uneven display brightness of the OLED display device is caused.
In order to solve the above problems, the related art has improved a pixel driving circuit, a capacitance boosting circuit is introduced in the pixel driving circuit, the threshold voltage of the driving circuit is effectively extracted through the coupling effect of the capacitor in the capacitor booster circuit, thereby realizing threshold voltage compensation on the control end voltage of the drive circuit to eliminate the influence of the threshold voltage on the generated drive current, however, the improved pixel driving circuit introduces the capacitance boosting circuit, so that when the data voltage is written into the control terminal of the driving circuit, the capacitance boosting circuit is needed, in the process, a large amount of parasitic capacitance existing in the pixel driving circuit is actually ignored, and the capacitance difference of different areas can also affect the boosting result of the capacitance, so that the control end voltage of the driving circuit is different, and the brightness is not uniform.
Based on the above problems, the present invention provides a novel pixel driving circuit, which can solve the problem of non-uniform display brightness of the display device due to non-uniformity of the driving circuit in the OLED display device without introducing a capacitor boosting circuit.
Referring to fig. 1, an embodiment of the present invention provides a pixel driving circuit for driving an OLED to emit light, the pixel driving circuit including: the device comprises a driving circuit 6, an energy storage circuit 3, a data writing circuit 1, a charging and discharging control circuit 2 and a compensation circuit 5; wherein, the control end (for example, point G in fig. 1) of the driving circuit 6 is connected to the first end of the energy storage circuit 3, the first end of the driving circuit 6 is connected to the first level signal input end Vd, and the second end of the driving circuit 6 is connected to one end of the light emitting element OLED; the second end of the energy storage circuit 3 is connected with the second end of the driving circuit 6; the data writing circuit 1 is respectively connected with the first scan signal terminal scan1, the data signal input terminal data and the first terminal N1 of the compensation circuit 5, and is used for controlling to switch on or off the connection between the data signal input terminal data and the first terminal N1 of the compensation circuit 5 under the control of the first scan signal terminal scan 1; the charge and discharge control circuit 2 is respectively connected to the first scan signal terminal scan1, the second scan signal terminal scan2, the first level signal input terminal Vd, the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6, and is configured to control to turn on or off the connection between the first level signal input terminal Vd and the control terminal of the driving circuit 6 and to turn on or off the connection between the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan1 and the second scan signal terminal scan 2; the control terminal of the compensation circuit 5 is connected to the control terminal of the driving circuit 6, and the compensation circuit 5 is used for controlling to turn on or off the connection between the first terminal N1 of the compensation circuit 5 and the second terminal N2 of the compensation circuit 5 under the control of the control terminal of the driving circuit 6.
Referring to fig. 1 and fig. 3, the working process of the pixel driving circuit in one display period is as follows:
in the charging period P1, the first level signal input terminal Vd inputs a first voltage signal, and under the control of the first scan signal terminal scan1 and the second scan signal terminal scan2, the charging and discharging control circuit 2 controls to turn on the connection between the first level signal input terminal Vd and the control terminal of the driving circuit 6, transmit the first voltage signal to the control terminal of the driving circuit 6, and store the first voltage signal in the energy storage circuit 3; the data signal input terminal data inputs a data signal Vdata, and under the control of the first scan signal terminal scan1, the data writing circuit 1 controls to turn on the connection between the data signal input terminal data and the first terminal N1 of the compensation circuit 5, and transmits the data signal Vdata to the first terminal N1 of the compensation circuit 5; at this time, the control terminal of the compensation circuit 5 is connected to the first voltage signal, the first terminal N1 of the compensation circuit 5 is connected to the data signal Vdata, when the compensation circuit 5 is an N-type compensation thin film transistor, the compensation circuit 5 can satisfy the on condition Vg1-Vs1> Vth1 by setting the voltage value corresponding to the first voltage signal to be greater than the voltage value corresponding to the data signal Vdata, where Vg1 represents the gate voltage of the N-type compensation thin film transistor (i.e., the control terminal voltage of the compensation circuit 5), Vs1 represents the source voltage of the N-type compensation thin film transistor (i.e., the voltage of the first terminal N1 of the compensation circuit 5), and Vth1 is the threshold voltage of the N-type compensation thin film transistor (i.e., the threshold voltage of the compensation circuit 5), so that the N-type compensation thin film transistor is changed from the off state to the on state, i.e., the compensation circuit 5 is changed from the connection between the first terminal N1 of the compensation circuit 5 and the second terminal N2 of the compensation circuit 5 to The connection between the second terminals N2 of the compensation circuit 5. It should be noted that the first level signal input terminal Vd may be a power signal input terminal, and the first voltage signal may be a power signal.
In the threshold compensation period P2, the data writing circuit 1 continues to control and turn on the connection between the data signal input terminal data and the first terminal N1 of the compensation circuit 5, and continues to transmit the data signal Vdata to the first terminal N1 of the compensation circuit 5; under the control of the first scan signal terminal scan1 and the second scan signal terminal scan2, the charge and discharge control circuit 2 controls to disconnect the first level signal input terminal Vd from the control terminal of the driving circuit 6, stops writing the first level signal into the control terminal of the driving circuit 6, and simultaneously controls to connect the second terminal N2 of the compensation circuit 5 with the control terminal of the driving circuit 6; since the tank circuit 3 stores the first level signal, and the first end N1 of the compensation circuit 5 still receives the data signal Vdata, the compensation circuit 5 can still maintain the conducting state, i.e. the connection between the first end N1 of the compensation circuit 5 and the second end N2 of the compensation circuit 5 is conducted, at the front stage time of the threshold compensation period P2, but as the time is prolonged, the charges of the first level signal stored in the tank circuit 3 will be discharged sequentially through the charge and discharge control circuit 2, the compensation circuit 5 and the data writing circuit 1 until the compensation circuit 5 does not meet the conducting condition and is turned off, i.e. the connection between the first end N1 of the compensation circuit 5 and the second end N2 of the compensation circuit 5 is turned off, at this time, the potential of the control end of the driving circuit 6 becomes Vdata + 1, and can be maintained at Vdata + Vth1 under the action of the tank circuit 3.
In the light emission period P3, under the control of the first scan signal terminal scan1, the data write circuit 1 controls to disconnect the connection between the data signal input terminal data and the first terminal N1 of the compensation circuit 5; under the control of the first scan signal terminal scan1 and the second scan signal terminal scan2, the charge and discharge control circuit 2 continues to control to disconnect the first level signal input terminal Vd from the control terminal of the driving circuit 6, and at the same time controls to disconnect the second terminal N2 of the compensation circuit 5 from the control terminal of the driving circuit 6; under the control of the control terminal of the driving circuit 6, the driving circuit 6 drives the light emitting element OLED to emit light.
In more detail, taking the driving circuit 6 including the N-type driving tft as an example, in the light emitting period P3, the voltage of the gate of the N-type driving tft (i.e., the control terminal of the driving circuit 6) is Vdata + Vth1, and the voltage of the source of the N-type driving tft (i.e., the second terminal of the driving circuit 6) is close to the ground potential, where the voltage Vgs2 between the gate of the N-type driving tft and the source of the N-type driving tft is:
vgs2 is Vdata + Vth1, equation one
The driving current I generated when the driving circuit 6 is turned on and operates in a saturation state is:
I＝k(Vgs2-Vth2)2formula two
In the second formula, Vth2 is the threshold voltage of the driving circuit 6, i.e. the threshold voltage of the N-type driving thin film transistor.
And generating a formula into a formula II:
I＝k(Vdata+Vth1-Vth2)2formula three
In the third formula, k is a constant.
Since the compensation circuit 5 and the driving circuit 6 belong to the same pixel driving circuit and are very close to each other, when the compensation circuit 5 and the driving circuit 6 are manufactured, the difference between the two is very small, that is, the threshold voltage Vth1 of the compensation circuit 5 and the threshold voltage Vth2 of the driving circuit 6 are almost the same, and therefore, the above formula three can be simplified as the following formula:
I≈k(Vdata)2formula four
As can be seen from the formula iv, the driving current I is considered to be related to only the data signal Vdata and is not substantially affected by the threshold voltage Vth2 of the driving circuit 6, and therefore, when the same data signal is input to a plurality of driving circuits 6 having different threshold voltages in the display device, the driving currents generated in the saturation states of the driving circuits 6 having different threshold voltages are the same, and when the driving circuits 6 having different threshold voltages in the display device drive the corresponding light emitting elements OLED to emit light, the light emitting luminance of the light emitting elements OLED is the same.
Note that, among the above three periods, the light-emission period P3 occupies most of one display period (i.e., one frame display time), and determines the light-emission luminance of the light-emitting unit OLED (i.e., pixel) in one display period; and the charging period P1 and the threshold compensation period P2 are extremely short with respect to the light emission period P3, and have less influence on the whole bright point condition of the light emitting unit OLED in one display cycle. In addition, in one display cycle, the light emitting units OLED of different rows included in the display device sequentially go through the above three periods, and enter the next display cycle after all the light emitting units OLED go through.
It can be known from the specific structure and operation process of the pixel driving circuit described above that, in the pixel driving circuit provided in the embodiment of the present invention, the charge and discharge control circuit 2 and the compensation circuit 5 are provided, and the threshold voltage of the compensation circuit 5 and the data signal provided by the data writing circuit 1 are written into the control terminal of the driving circuit 6 through the cooperative operation of the charge and discharge control circuit 2 and the compensation circuit 5, because the threshold voltage of the compensation circuit 5 and the threshold voltage of the driving circuit 6 are very close, the driving current generated by the driving circuit 6 when driving the light emitting element OLED is basically unrelated to the threshold voltage of the driving circuit 6, thereby well avoiding the problem of non-uniform display brightness of the display device caused by non-uniformity of the threshold voltage of the driving circuit 6 in the display device.
In addition, in the pixel driving circuit provided by the embodiment of the present invention, only the storage function of the energy storage circuit 3 is utilized, and the capacitor boosting circuit is not involved, so that the pixel driving circuit provided by the embodiment of the present invention avoids the problem of uneven brightness caused by the difference of capacitors in different areas of the display device.
The charging and discharging control circuit 2 provided in the above embodiments has various specific structures, as shown in fig. 4, in some embodiments, the charging and discharging control circuit 2 may specifically include:
the first charge and discharge electronic circuit 21 is respectively connected with the second scan signal terminal scan2, the first level signal input terminal Vd and the second terminal N2 of the compensation circuit 5, and is used for controlling to switch on or off the connection between the first level signal input terminal Vd and the second terminal N2 of the compensation circuit 5 under the control of the second scan signal terminal scan 2;
the second charge/discharge electronic circuit 22 is respectively connected to the first scan signal terminal scan1, the second terminal N2 of the compensation circuit 5, and the control terminal of the driving circuit 6, and is configured to control to turn on or off the connection between the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan 1.
Specifically, when the charge and discharge control circuit 2 adopts the above structure, the working process thereof specifically includes:
in the charging period P1, the first charge and discharge electronic circuit 21 controls to turn on the connection between the first level signal input terminal Vd and the second terminal N2 of the compensation circuit 5 under the control of the second scan signal terminal scan2, and the second charge and discharge electronic circuit 22 controls to turn on the connection between the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan 1.
In the threshold compensation period P2, the first charge and discharge electronic circuit 21 controls to disconnect the first level signal input terminal Vd from the second terminal N2 of the compensation circuit 5 under the control of the second scan signal terminal scan2, and the second charge and discharge electronic circuit 22 controls to connect the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan 1.
In the light emitting period P3, the first charge and discharge electronic circuit 21 continues to control to disconnect the connection between the first level signal input terminal Vd and the second terminal N2 of the compensation circuit 5 under the control of the second scan signal terminal scan2, and the second charge and discharge electronic circuit 22 controls to disconnect the connection between the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan 1.
The charge and discharge control circuit 2 is set to the above structure, so that the charge and discharge control circuit 2 can respectively control the conduction condition of the control end of the driving circuit 6 and the first level signal input end Vd, and the conduction condition of the control end of the driving circuit 6 and the second end N2 of the compensation circuit 5, and the second charge and discharge electronic circuit 22 can share the same first scanning signal end scan1 with the data writing circuit 1, so that only one second scanning signal end scan2 specially applied to the charge and discharge control circuit 2 needs to be set, and the structure of the pixel driving circuit is better simplified.
Further, with reference to fig. 4, the first charge/discharge electronic circuit 21 provided in the above embodiment may specifically include a first transistor T1, a gate of the first transistor T1 is connected to the second scan signal terminal scan2, a first pole of the first transistor T1 is connected to the first level signal input terminal Vd, and a second pole of the first transistor T1 is connected to the second terminal N2 of the compensation circuit 5; the second charge/discharge electronic circuit 22 includes a second transistor T2, a gate of the second transistor T2 is connected to the first scan signal terminal scan1, a first pole of the second transistor T2 is connected to the second terminal N2 of the compensation circuit 5, and a second pole of the second transistor T2 is connected to the control terminal of the driving circuit 6.
Specifically, when the first charge-discharge electronic circuit 21 and the second charge-discharge electronic circuit 22 adopt the above-described structure, as shown in fig. 3, the specific working processes of the first charge-discharge electronic circuit 21 and the second charge-discharge electronic circuit 22 are as follows:
in the charging period P1, the first transistor T1 is turned on under the control of the second scan signal terminal scan2, and controls to turn on the connection between the first level signal input terminal Vd and the second terminal N2 of the compensation circuit 5, and the second transistor T2 is turned on under the control of the first scan signal terminal scan1, and controls to turn on the connection between the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6.
In the threshold compensation period P2, the first transistor T1 is turned off under the control of the second scan signal terminal scan2, the connection between the first level signal input terminal Vd and the second terminal N2 of the compensation circuit 5 is controlled to be disconnected, and the second transistor T2 is turned on under the control of the first scan signal terminal scan1, the connection between the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 is controlled to be turned on.
In the light emission period P3, the first transistor T1 is turned off under the control of the second scan signal terminal scan2, and continues to control to disconnect the first level signal input terminal Vd from the second terminal N2 of the compensation circuit 5, and the second transistor T2 is turned off under the control of the first scan signal terminal scan1, and controls to disconnect the second terminal N2 of the compensation circuit 5 from the control terminal of the driving circuit 6.
In some embodiments, the data writing circuit 1 provided in the above embodiments may include the third transistor T3, the tank circuit 3 may include the tank capacitor C1, the driving circuit 6 includes the driving transistor DTFT, and the compensation circuit 5 includes the compensation transistor T5.
Specifically, the gate of the third transistor T3 is connected to the first scan signal terminal scan1, the first pole of the third transistor T3 is connected to the data signal input data, and the second pole of the third transistor T3 is connected to the first pole of the compensation transistor T5 (i.e., the first terminal N1 of the compensation circuit 5); a first terminal of the energy storage capacitor C1 is connected to the gate of the driving transistor DTFT (i.e., the control terminal of the driving circuit 6), and a second terminal of the energy storage capacitor C1 is connected to the second terminal of the driving transistor DTFT (i.e., the second terminal of the driving circuit 6); a first pole of the driving transistor DTFT (i.e., a first terminal of the driving circuit 6) is connected to the first level signal input terminal Vd, and a second pole of the driving transistor DTFT is connected to the light emitting element OLED; the gate of the compensation transistor T5 (i.e., the control terminal of the compensation circuit 5) is connected to the gate of the driving transistor DTFT, and the second pole of the compensation transistor T5 (i.e., the second terminal N2 of the compensation circuit 5) is connected to the charge and discharge control circuit 2.
When the data writing circuit 1 adopts the above structure, the specific working process is as follows:
in the charging period P1 and the threshold compensation period P2, the third transistor T3 is turned on under the control of the first scan signal terminal scan1, controlling to turn on the connection between the data signal input terminal data and the first pole of the compensation transistor T5; in the light emission period P3, the third transistor T3 is turned off under the control of the first scan signal terminal scan1, controlling the disconnection between the data signal input terminal data and the first pole of the compensation transistor T5.
When the energy storage capacitor C1 is adopted by the energy storage circuit 3, the energy storage capacitor C1 can maintain the gate potential of the driving transistor DTFT, that is, store the first voltage signal in the charging period P1, make the gate potential of the driving transistor DTFT the voltage value corresponding to the first voltage signal, store the data signal and the threshold voltage of the compensation transistor T5 in the threshold compensation period P2 and the light emitting period P3, and make the gate potential of the driving transistor DTFT Vdata + Vth 1.
In some embodiments, as shown in fig. 2, the pixel driving circuit provided in the above embodiments further includes:
and the light emission control circuit 4 is respectively connected with the light emission control terminal EM, the second terminal of the driving circuit 6 and the second level signal input terminal Vs, and is configured to control to turn on or off the connection between the second terminal of the driving circuit 6 and the second level signal input terminal Vs under the control of the light emission control terminal EM.
As shown in fig. 3, the specific operation process of the light-emitting control unit includes:
in the charging period P1 and the threshold compensation period P2, the emission control circuit 4 controls to turn on the connection between the second terminal of the driving circuit 6 and the second level signal input terminal Vs under the control of the emission control terminal EM.
In the light emission period P3, the light emission control circuit 4 controls to disconnect the connection between the second terminal of the drive circuit 6 and the second level signal input terminal Vs under the control of the light emission control terminal EM.
It should be noted that the second level signal input terminal Vs can be selected as a power supply cathode, the second level electrical signal inputted thereto can be selected as a ground level signal GND, and the other end of the light emitting element OLED driven by the pixel driving circuit can also be connected to the second level signal input terminal Vs.
The light emission control circuit 4 incorporated in the pixel driving circuit can short-circuit the light emitting element OLED during the charging period P1 and the threshold compensation period P2, so that the pixel driving circuit can drive the light emitting element OLED to emit light only during the light emission period P3, and does not drive the light emitting element OLED to emit light during neither the charging period P1 nor the threshold compensation period P2, thereby ensuring the display effect of the display device.
Further, as shown in fig. 5, the light emitting control circuit 4 may specifically include a fourth transistor T4, a gate of the fourth transistor T4 is connected to the light emitting control terminal EM, a first pole of the fourth transistor T4 is connected to the second terminal of the driving circuit 6, and a second pole of the fourth transistor T4 is connected to the second level signal input terminal Vs.
Specifically, when the light emission control circuit 4 includes the fourth transistor T4, the specific operation process thereof includes:
in the charging period P1 and the threshold compensation period P2, the fourth transistor T4 is turned on under the control of the emission control terminal EM, thereby controlling to turn on the connection between the second terminal of the driving circuit 6 and the second level signal input terminal Vs.
In the light emission period P3, the fourth transistor T4 is turned off under the control of the light emission control terminal EM, thereby controlling to disconnect the second terminal of the driving circuit 6 from the second level signal input terminal Vs.
It is to be noted that the specific types of the first transistor T1, the second transistor T2, the third transistor T3, the fourth transistor T4, the compensation transistor T5 and the driving transistor DTFT employed in the above embodiments may be selected according to actual needs, and may be, for example, an N-type thin film transistor or a P-type thin film transistor. In the embodiment of the present invention, an N-type thin film transistor is taken as an example for description, wherein a first pole of each transistor may be selected as a drain electrode, and a second pole of each transistor may be selected as a source electrode, or a first pole of each transistor may be selected as a source electrode, and a second pole of each transistor may be selected as a drain electrode.
In order to more clearly illustrate the operation of the pixel driving circuit provided in the above embodiments, a specific embodiment is given below.
As shown in fig. 5, when the charge/discharge control circuit 2 in the pixel driving circuit includes a first transistor T1 and a second transistor T2, the data writing circuit 1 includes a third transistor T3, the light emission control circuit 4 includes a fourth transistor T4, the energy storage circuit 3 includes an energy storage capacitor C1, the compensation circuit 5 includes a compensation transistor T5, and the driving circuit 6 includes a driving transistor DTFT, the specific operation process of the pixel driving circuit is as follows:
in the charging period P1, as shown in fig. 6a, the first level signal input terminal Vd inputs the first voltage signal, the second transistor T2 is turned on under the control of the first scan signal terminal scan1, the first transistor T1 is turned on under the control of the second scan signal terminal scan2, thereby controlling the connection between the first level signal input terminal Vd and the gate of the driving transistor DTFT to be turned on, the first voltage signal is transmitted to the gate of the driving transistor DTFT and stored in the energy storage capacitor C1; the data signal input terminal data inputs the data signal Vdata, and the third transistor T3 is turned on under the control of the first scan signal terminal scan1, thereby controlling to turn on the connection between the data signal input terminal data and the first pole of the compensation transistor T5, and transmitting the data signal Vdata to the first pole of the compensation transistor T5; at this time, the gate of the compensation transistor T5 is connected to the first voltage signal, the first electrode of the compensation transistor T5 is connected to the data signal Vdata, and when the compensation transistor T5 is an N-type thin film transistor, the voltage value corresponding to the first voltage signal is set to be greater than the voltage value corresponding to the data signal Vdata, so that the compensation transistor T5 can satisfy the on-condition Vg1-Vs1> Vth1, and the compensation transistor T5 is changed from the off-state to the on-state. In this charging period P1, the fourth transistor T4 is turned on under the control of the emission control terminal EM, thereby controlling the connection between the second pole of the turn-on driving transistor DTFT and the second level signal input terminal Vs to short-circuit the light emitting element OLED.
During the threshold compensation period P2, as shown in fig. 6b, the third transistor T3 continues to be turned on, thereby continuing to control and turn on the connection between the data signal input terminal data and the first pole of the compensation transistor T5, and continuing to transmit the data signal Vdata to the first pole of the compensation transistor T5; the second transistor T2 is turned on under the control of the first scan signal terminal scan1, and the first transistor T1 is turned off under the control of the second scan signal terminal scan2, thereby controlling to disconnect the connection between the first level signal input terminal Vd and the gate electrode of the driving transistor DTFT, stop writing the first level signal to the gate electrode of the driving transistor DTFT, and simultaneously control to turn on the connection between the second pole of the compensation transistor T5 and the gate electrode of the driving transistor DTFT; since the energy storage capacitor C1 stores the first level signal and the first pole of the compensation transistor T5 is switched into the data signal Vdata, the compensation transistor T5 can still maintain the on state in the front period of the threshold compensation period P2, but as the time goes on, the charge of the first level signal stored in the energy storage capacitor C1 is discharged through the second transistor T2, the compensation transistor T5 and the third transistor T3 in sequence until the compensation transistor T5 is turned off without meeting the on condition, at this time, the potential of the gate of the driving transistor DTFT becomes Vdata + Vth1 and can be kept at Vdata + Vth1 under the action of the energy storage capacitor C1. In the threshold compensation period P2, the fourth transistor T4 is turned on under the control of the emission control terminal EM, thereby controlling the connection between the second pole of the turn-on driving transistor DTFT and the second level signal input terminal Vs to short-circuit the light emitting element OLED.
In the light emission period P3, as shown in fig. 6c, the third transistor T3 is turned off under the control of the first scan signal terminal scan1, thereby controlling to disconnect the connection between the data signal input terminal data and the first pole of the compensation transistor T5; the second transistor T2 is turned off under the control of the first scan signal terminal scan1, and the first transistor T1 is turned off under the control of the second scan signal terminal scan2, thereby continuing to control to disconnect the first level signal input terminal Vd from the gate of the driving transistor DTFT and simultaneously controlling to disconnect the second pole of the compensating transistor T5 from the gate of the driving transistor DTFT; under the control of the gate of the driving transistor DTFT, the driving transistor DTFT is turned on to drive the light emitting element OLED to emit light. In the light emission period P3, the fourth transistor T4 is turned off under the control of the light emission control terminal EM, thereby controlling to disconnect the second pole of the driving transistor DTFT from the second level signal input terminal Vs.
The embodiment of the invention also provides a display device which comprises the pixel driving circuit provided by the embodiment.
Because the pixel driving circuit provided by the above embodiment is provided with the charge and discharge control circuit 2 and the compensation circuit 5, the threshold voltage of the compensation circuit 5 and the data signal provided by the data writing circuit 1 are written into the control end of the driving circuit 6 through the cooperation of the charge and discharge control circuit 2 and the compensation circuit 5, so that when the driving circuit 6 drives the light emitting element OLED, the generated driving current is basically irrelevant to the threshold voltage of the driving circuit 6, thereby well avoiding the problem of uneven display brightness of the display device caused by the non-uniformity of the threshold voltage of the driving circuit 6 in the display device; therefore, the display device provided by the embodiment of the invention can realize better display effect when comprising the pixel driving circuit.
An embodiment of the present invention further provides a driving method for a pixel driving circuit, which is used to drive the pixel driving circuit provided in the foregoing embodiment, and the driving method includes: at each of the display periods, the display period,
in the charging period P1, the first level signal input terminal Vd inputs a first voltage signal, and under the control of the first scan signal terminal scan1 and the second scan signal terminal scan2, the charging and discharging control circuit 2 controls to turn on the connection between the first level signal input terminal Vd and the control terminal of the driving circuit 6, transmit the first voltage signal to the control terminal of the driving circuit 6, and store the first voltage signal in the energy storage circuit 3; the data signal input terminal data inputs a data signal Vdata, and under the control of the first scan signal terminal scan1, the data writing circuit 1 controls to turn on the connection between the data signal input terminal data and the first terminal N1 of the compensation circuit 5, and transmits the data signal Vdata to the first terminal N1 of the compensation circuit 5; under the control of the control terminal of the driving circuit 6, the compensation circuit 5 is changed from the connection between the first terminal N1 of the compensation circuit 5 and the second terminal N2 of the compensation circuit 5 to the connection between the first terminal N1 of the compensation circuit and the second terminal N2 of the compensation circuit 5;
in the threshold compensation period P2, the data writing circuit 1 continues to control and turn on the connection between the data signal input terminal data and the first terminal N1 of the compensation circuit 5, and transmits the data signal Vdata to the first terminal N1 of the compensation circuit; under the control of the first scan signal terminal scan1 and the second scan signal terminal scan2, the charge and discharge control circuit 2 controls to disconnect the first level signal input terminal Vd from the control terminal of the driving circuit 6, and controls to connect the second terminal N2 of the conduction compensation circuit with the control terminal of the driving circuit 6; under the control of the control terminal of the driving circuit 6, the compensation circuit 5 is changed from the connection between the first terminal N1 of the on compensation circuit 5 and the second terminal N2 of the compensation circuit 5 to the connection between the first terminal N1 of the off compensation circuit 5 and the second terminal N2 of the compensation circuit, the potential of the control terminal of the driving circuit 6 is changed to Vdata + Vth1, and Vth1 is the threshold voltage of the compensation circuit 5;
in the light emission period P3, under the control of the first scan signal terminal scan1, the data write circuit 1 controls to disconnect the connection between the data signal input terminal data and the first terminal N1 of the compensation circuit; under the control of the first scan signal terminal scan1 and the second scan signal terminal scan2, the charge and discharge control circuit 2 controls to disconnect the second terminal N2 of the compensation circuit from the control terminal of the driving circuit 6; under the control of the control terminal of the driving circuit 6, the driving circuit 6 drives the light emitting element OLED to emit light.
Specifically, the pixel driving circuit includes a plurality of display periods, and the driving method of the pixel driving circuit includes, in each of the display periods:
in the charging period P1, the first level signal input terminal Vd inputs a first voltage signal, and under the control of the first scan signal terminal scan1 and the second scan signal terminal scan2, the charging and discharging control circuit 2 controls to turn on the connection between the first level signal input terminal Vd and the control terminal of the driving circuit 6, transmit the first voltage signal to the control terminal of the driving circuit 6, and store the first voltage signal in the energy storage circuit 3; the data signal input terminal data inputs a data signal Vdata, and under the control of the first scan signal terminal scan1, the data writing circuit 1 controls to turn on the connection between the data signal input terminal data and the first terminal N1 of the compensation circuit 5, and transmits the data signal Vdata to the first terminal N1 of the compensation circuit 5; at this time, the control terminal of the compensation circuit 5 is connected to the first voltage signal, the first terminal N1 of the compensation circuit 5 is connected to the data signal Vdata, when the compensation circuit 5 is an N-type compensation thin film transistor, the compensation circuit 5 can satisfy the on condition Vg1-Vs1> Vth1 by setting the voltage value corresponding to the first voltage signal to be greater than the voltage value corresponding to the data signal Vdata, where Vg1 represents the gate voltage of the N-type compensation thin film transistor (i.e., the control terminal voltage of the compensation circuit 5), Vs1 represents the source voltage of the N-type compensation thin film transistor (i.e., the voltage of the first terminal N1 of the compensation circuit 5), and Vth1 is the threshold voltage of the N-type compensation thin film transistor (i.e., the threshold voltage of the compensation circuit 5), so that the N-type compensation thin film transistor is changed from the off state to the on state, i.e., the compensation circuit 5 is changed from the connection between the first terminal N1 of the compensation circuit 5 and the second terminal N2 of the compensation circuit 5 to The connection between the second terminals N2 of the compensation circuit 5. It should be noted that the first level signal input terminal Vd may be a power signal input terminal, and the first voltage signal may be a power signal.
In the threshold compensation period P2, the data writing circuit 1 continues to control and turn on the connection between the data signal input terminal data and the first terminal N1 of the compensation circuit 5, and continues to transmit the data signal Vdata to the first terminal N1 of the compensation circuit 5; under the control of the first scan signal terminal scan1 and the second scan signal terminal scan2, the charge and discharge control circuit 2 controls to disconnect the first level signal input terminal Vd from the control terminal of the driving circuit 6, stops writing the first level signal into the control terminal of the driving circuit 6, and simultaneously controls to connect the second terminal N2 of the compensation circuit 5 with the control terminal of the driving circuit 6; since the tank circuit 3 stores the first level signal and the second terminal of the compensation circuit 5 is still connected to the data signal Vdata, in the previous period of the threshold compensation period P2, the compensation circuit 5 can still maintain the on state, i.e. the connection between the first terminal N1 of the compensation circuit 5 and the second terminal N2 of the compensation circuit 5 is turned on, but as time goes on, the charges of the first level signal stored in the tank circuit 3 will be discharged through the charge and discharge control circuit 2, the compensation circuit 5 and the data writing circuit 1 in sequence until the compensation circuit 5 is turned off without meeting the on condition, i.e. the connection between the first terminal N1 of the compensation circuit 5 and the second terminal N2 of the compensation circuit 5 is turned off, at this time, the potential of the control terminal of the driving circuit 6 becomes Vdata + Vth1, and can be kept at Vdata + Vth1 under the action of the tank circuit 3.
In the light emission period P3, under the control of the first scan signal terminal scan1, the data write circuit 1 controls to disconnect the connection between the data signal input terminal data and the first terminal N1 of the compensation circuit 5; under the control of the first scan signal terminal scan1 and the second scan signal terminal scan2, the charge and discharge control circuit 2 continues to control to disconnect the first level signal input terminal Vd from the control terminal of the driving circuit 6, and at the same time controls to disconnect the second terminal N2 of the compensation circuit 5 from the control terminal of the driving circuit 6; under the control of the control terminal of the driving circuit 6, the driving circuit 6 drives the light emitting element OLED to emit light.
In the driving method of the pixel driving circuit provided by the embodiment of the invention, the charge-discharge control circuit 2 and the compensation circuit 5 are controlled to work cooperatively, the threshold voltage of the compensation circuit 5 and the data signal provided by the data writing circuit 1 are written into the control end of the driving circuit 6, and as the threshold voltage of the compensation circuit 5 is very close to the threshold voltage of the driving circuit 6, the driving current generated by the driving circuit 6 when the driving circuit 6 drives the light-emitting element OLED is basically irrelevant to the threshold voltage of the driving circuit 6, so that the problem of uneven display brightness of the display device caused by the non-uniformity of the threshold voltage of the driving circuit 6 in the display device is well avoided.
In addition, in the driving method of the pixel driving circuit provided by the embodiment of the present invention, only the storage function of the energy storage circuit 3 is utilized, and the capacitor boosting circuit is not involved, so that the driving method of the pixel driving circuit provided by the embodiment of the present invention avoids the problem of uneven brightness in different areas of the display device due to the difference of capacitors.
In some embodiments, when the charge and discharge control circuit 2 includes the first charge and discharge electronic circuit 21 and the second charge and discharge electronic circuit 22, the step of the charge and discharge control circuit 2 controlling to turn on the connection between the first level signal input terminal Vd and the control terminal of the driving circuit 6 specifically includes: the first charge and discharge electronic circuit 21 controls to turn on the connection between the first level signal input terminal Vd and the second terminal N2 of the compensation circuit under the control of the second scan signal terminal scan2, and the second charge and discharge electronic circuit 22 controls to turn on the connection between the second terminal N2 of the compensation circuit and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan 1.
When the charge and discharge control circuit 2 includes the first charge and discharge electronic circuit 21 and the second charge and discharge electronic circuit 22, the step of the charge and discharge control circuit 2 controlling to disconnect the connection between the first level signal input terminal Vd and the control terminal of the driving circuit 6 and controlling to connect the second terminal N2 of the compensation circuit and the control terminal of the driving circuit 6 specifically includes: the first charge and discharge electronic circuit 21 controls to disconnect the connection between the first level signal input terminal Vd and the second terminal N2 of the compensation circuit under the control of the second scan signal terminal scan2, and the second charge and discharge electronic circuit 22 controls to connect the second terminal N2 of the compensation circuit and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan 1.
When the charge and discharge control circuit 2 includes the first charge and discharge electronic circuit 21 and the second charge and discharge electronic circuit 22, the step of the charge and discharge control circuit 2 controlling to disconnect the connection between the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 specifically includes: the second charge and discharge electronic circuit 22 controls to disconnect the connection between the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan 1.
Specifically, when the charge and discharge control circuit 2 includes the first charge and discharge electronic circuit 21 and the second charge and discharge electronic circuit 22, the specific working process of the charge and discharge control circuit 2 includes:
in the charging period P1, the first charge and discharge electronic circuit 21 controls to turn on the connection between the first level signal input terminal Vd and the second terminal N2 of the compensation circuit 5 under the control of the second scan signal terminal scan2, and the second charge and discharge electronic circuit 22 controls to turn on the connection between the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan 1.
In the threshold compensation period P2, the first charge and discharge electronic circuit 21 controls to disconnect the first level signal input terminal Vd from the second terminal N2 of the compensation circuit 5 under the control of the second scan signal terminal scan2, and the second charge and discharge electronic circuit 22 controls to connect the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan 1.
In the light emitting period P3, the first charge and discharge electronic circuit 21 continues to control to disconnect the connection between the first level signal input terminal Vd and the second terminal N2 of the compensation circuit 5 under the control of the second scan signal terminal scan2, and the second charge and discharge electronic circuit 22 controls to disconnect the connection between the second terminal N2 of the compensation circuit 5 and the control terminal of the driving circuit 6 under the control of the first scan signal terminal scan 1.
In some embodiments, when the pixel driving circuit further includes the light emission control circuit 4, the driving method provided by the above embodiments further includes:
in the charging period P1 and the threshold compensation period P2, the emission control circuit 4 controls to turn on the connection between the second terminal of the driving circuit 6 and the second level signal input terminal Vs under the control of the emission control terminal EM;
in the light emission period P3, the light emission control circuit 4 controls to disconnect the connection between the second terminal of the drive circuit 6 and the second level signal input terminal Vs under the control of the light emission control terminal EM.
The driving method provided by the above embodiment can short-circuit the light emitting element OLED during the charging period P1 and the threshold compensation period P2 when the light emission control unit is introduced into the pixel driving circuit, so that the pixel driving circuit can drive the light emitting element OLED to emit light only during the light emitting period P3, and the light emitting element OLED is not driven to emit light during the charging period P1 and the threshold compensation period P2, thereby better ensuring the display effect of the display device.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in this disclosure is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "under" another element, it can be "directly on" or "under" the other element or intervening elements may be present.
In the foregoing description of embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims (10)

1. A pixel driving circuit for driving a light emitting element to emit light, comprising: the device comprises a driving circuit, an energy storage circuit, a data writing circuit, a charge and discharge control circuit and a compensation circuit; wherein,
the control end of the driving circuit is connected with the first end of the energy storage circuit, the first end of the driving circuit is connected with the first level signal input end, and the second end of the driving circuit is connected with the light-emitting element;
the second end of the energy storage circuit is connected with the second end of the driving circuit;
the data writing circuit is respectively connected with a first scanning signal end, a data signal input end and a first end of the compensation circuit and is used for controlling connection or disconnection between the data signal input end and the first end of the compensation circuit under the control of the first scanning signal end;
the charge and discharge control circuit is respectively connected with the first scanning signal end, the second scanning signal end, the first level signal input end, the second end of the compensation circuit and the control end of the driving circuit, and is used for controlling connection or disconnection between the first level signal input end and the control end of the driving circuit under the control of the first scanning signal end and the second scanning signal end, and controlling connection or disconnection between the second end of the compensation circuit and the control end of the driving circuit;
the control end of the compensation circuit is connected with the control end of the driving circuit, and the compensation circuit is used for controlling connection or disconnection between the first end of the compensation circuit and the second end of the compensation circuit under the control of the control end of the driving circuit.
2. The pixel driving circuit according to claim 1, wherein the charge and discharge control circuit comprises:
the first charge-discharge electronic circuit is respectively connected with the second scanning signal end, the first level signal input end and the second end of the compensation circuit and is used for controlling connection or disconnection between the first level signal input end and the second end of the compensation circuit under the control of the second scanning signal end;
and the second charging and discharging electronic circuit is respectively connected with the first scanning signal end, the second end of the compensation circuit and the control end of the driving circuit and is used for controlling the connection between the second end of the compensation circuit and the control end of the driving circuit to be switched on or switched off under the control of the first scanning signal end.
3. The pixel driving circuit according to claim 2,
the first charge-discharge electronic circuit comprises a first transistor, the grid electrode of the first transistor is connected with the second scanning signal end, the first pole of the first transistor is connected with the first level signal input end, and the second pole of the first transistor is connected with the second end of the compensation circuit;
the second charge-discharge electronic circuit comprises a second transistor, a grid electrode of the second transistor is connected with the first scanning signal end, a first pole of the second transistor is connected with the second end of the compensation circuit, and a second pole of the second transistor is connected with the control end of the driving circuit.
4. The pixel driving circuit according to any one of claims 1 to 3, wherein the data writing circuit comprises a third transistor, the tank circuit comprises a tank capacitor, the driving circuit comprises a driving transistor, and the compensation circuit comprises a compensation transistor; wherein,
a gate of the third transistor is connected to the first scan signal terminal, a first pole of the third transistor is connected to the data signal input terminal, and a second pole of the third transistor is connected to the first pole of the compensation transistor;
the first end of the energy storage capacitor is connected with the grid electrode of the driving transistor, and the second end of the energy storage capacitor is connected with the second pole of the driving transistor;
a first pole of the driving transistor is connected with the first level signal input end, and a second pole of the driving transistor is connected with the light-emitting element;
and the grid electrode of the compensation transistor is connected with the grid electrode of the driving transistor, and the second pole of the compensation transistor is connected with the charge and discharge control circuit.
5. The pixel driving circuit according to any one of claims 1 to 3, further comprising:
and the light-emitting control circuit is respectively connected with the light-emitting control end, the second end of the driving circuit and the second level signal input end and is used for controlling the connection between the second end of the driving circuit and the second level signal input end to be switched on or switched off under the control of the light-emitting control end.
6. The pixel driving circuit according to claim 5, wherein the light emission control circuit comprises a fourth transistor, a gate of the fourth transistor is connected to the light emission control terminal, a first pole of the fourth transistor is connected to the second terminal of the driving circuit, and a second pole of the fourth transistor is connected to the second level signal input terminal.
7. A display device comprising the pixel drive circuit according to any one of claims 1 to 6.
8. A driving method of a pixel driving circuit for driving the pixel driving circuit according to any one of claims 1 to 6, the driving method comprising: at each of the display periods, the display period,
in a charging period, a first voltage signal is input into a first level signal input end, a charging and discharging control circuit controls and conducts connection between the first level signal input end and a control end of a driving circuit under the control of a first scanning signal end and a second scanning signal end, and the first voltage signal is transmitted to the control end of the driving circuit and stored in an energy storage circuit; a data signal Vdata is input at a data signal input end, under the control of the first scanning signal end, a data writing circuit controls and conducts the connection between the data signal input end and the first end of the compensation circuit, and the data signal Vdata is transmitted to the first end of the compensation circuit; the compensation circuit is changed from the connection between the first end of the compensation circuit and the second end of the compensation circuit to the connection between the first end of the compensation circuit and the second end of the compensation circuit under the control of the control end of the drive circuit;
in a threshold compensation period, the data writing circuit continues to control and conduct the connection between the data signal input end and the first end of the compensation circuit, and transmits the data signal Vdata to the first end of the compensation circuit; under the control of the first scanning signal end and the second scanning signal end, the charge and discharge control circuit controls to disconnect the connection between the first level signal input end and the control end of the driving circuit and controls to connect the second end of the compensation circuit and the control end of the driving circuit; under the control of the control terminal of the driving circuit, the compensation circuit is changed from turning on the connection between the first terminal of the compensation circuit and the second terminal of the compensation circuit to turning off the connection between the first terminal of the compensation circuit and the second terminal of the compensation circuit, the potential of the control terminal of the driving circuit is changed into Vdata + Vth1, and Vth1 is the threshold voltage of the compensation circuit;
in the light emitting period, under the control of the first scanning signal terminal, the data writing circuit controls to disconnect the connection between the data signal input terminal and the first terminal of the compensation circuit; under the control of the first scanning signal end and the second scanning signal end, the charge and discharge control circuit controls to disconnect the connection between the second end of the compensation circuit and the control end of the drive circuit; under the control of the control end of the drive circuit, the drive circuit drives the light-emitting element to emit light.
9. The driving method of the pixel driving circuit according to claim 8, wherein when the charge and discharge control circuit includes a first charge and discharge electronic circuit and a second charge and discharge electronic circuit, the step of controlling the connection between the first level signal input terminal and the control terminal of the driving circuit by the charge and discharge control circuit specifically includes:
under the control of the second scanning signal end, the first charge-discharge electronic circuit controls and conducts the connection between the first level signal input end and the second end of the compensation circuit, and under the control of the first scanning signal end, the second charge-discharge electronic circuit controls and conducts the connection between the second end of the compensation circuit and the control end of the driving circuit;
the step of the charge and discharge control circuit controlling to disconnect the connection between the first level signal input end and the control end of the driving circuit and controlling to connect the second end of the compensation circuit and the control end of the driving circuit specifically comprises:
under the control of the second scanning signal end, the first charge-discharge electronic circuit controls to disconnect the connection between the first level signal input end and the second end of the compensation circuit, and under the control of the first scanning signal end, the second charge-discharge electronic circuit controls to connect the connection between the second end of the compensation circuit and the control end of the driving circuit;
the step of the charge and discharge control circuit controlling to disconnect the connection between the second end of the compensation circuit and the control end of the driving circuit specifically comprises:
and under the control of the first scanning signal end, the second charging and discharging electronic circuit controls to disconnect the second end of the compensation circuit from the control end of the driving circuit.
10. The method for driving the pixel drive circuit according to claim 8 or 9, wherein when the pixel drive circuit further includes a light emission control circuit, the method further includes:
in the charging period and the threshold compensation period, the light-emitting control circuit controls and conducts the connection between the second end of the drive circuit and the second level signal input end under the control of the light-emitting control end;
in the light emitting period, the light emitting control circuit controls to disconnect the second terminal of the driving circuit from the second level signal input terminal under the control of the light emitting control terminal.
CN201811590699.6A 2018-12-25 2018-12-25 Pixel driving circuit, driving method thereof and display device Active CN109448639B (en)

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