CN106652910A - Pixel circuit and driving method thereof, and organic light emitting display - Google Patents
Pixel circuit and driving method thereof, and organic light emitting display Download PDFInfo
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- CN106652910A CN106652910A CN201610932065.9A CN201610932065A CN106652910A CN 106652910 A CN106652910 A CN 106652910A CN 201610932065 A CN201610932065 A CN 201610932065A CN 106652910 A CN106652910 A CN 106652910A
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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
- G09G3/3233—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element
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- Control Of El Displays (AREA)
Abstract
The invention provides a pixel circuit and a driving method thereof, and an organic light emitting display. A four-terminal second thin film transistor is used as a driving transistor. The threshold voltage of the second thin film transistor is stored in the source of the second thin film transistor in advance by a third power supply. The current output later by the second thin film transistor is determined by a data voltage provided by a data line and a first power voltage provided by a first power supply, and has nothing to do with the threshold voltage of the second thin film transistor. Thus, uneven brightness caused by threshold voltage deviation is avoided. The display problem of the organic light emitting display adopting the pixel circuit and the driving method thereof caused by threshold voltage shift can be avoided, and the brightness uniformity is improved.
Description
Technical field
The present invention relates to technical field of flat panel display, more particularly to a kind of image element circuit and its driving method and organic light emission
Display.
Background technology
In recent years, with the fast development and application of information technology, radio mobile communication and information household appliances, people are to electronics
The dependency of product grows with each passing day, and more brings flourishing for various Display Techniques and display device.Wherein, panel display apparatus
Because having the advantages that to fully planarize, light, thin, power saving, and be widely used in mobile phone, TV, personal digital assistant, numeral
The various consumption electronic products such as camera, notebook computer, desk computer, become the main flow in display device.
With the development of flat panel display, the in large size and high-resolution of panel display apparatus is required increasingly
It is high.Non-crystalline silicon (a-si) material is relatively low due to its electron mobility, shows in the flat board of large scale, high-resolution, high response speed
Increasingly it is restricted when using on showing device.Low temperature polycrystalline silicon (low temperature poly-silicon, referred to as
LTPS) material and with oxide semiconductor of the indium gallium zinc oxide (IGZO) as representative due to higher electron mobility,
It is adapted to make large scale, high-resolution panel display apparatus, has therefore suffered from extensive concern and application.
OLED is using thin film transistor (TFT) (English full name Thin Film Transistor, abbreviation TFT)
Shown to control Organic Light Emitting Diode (English full name Organic Lighting Emitting Diode, abbreviation OLED)
The panel display apparatus of diagram picture, its display mode and traditional Thin Film Transistor-LCD (English full name Thin Film
Transistor liquid crystal display, abbreviation TFT-LCD) display mode difference, without the need for backlight, and, tool
Have contrast height, fast response time, it is frivolous many advantages, such as.Therefore, OLED is described as replacing thin film brilliant
The panel display apparatus of a new generation of body pipe liquid crystal display.
In order to realize large scale and high-resolution, OLED is generally partly led using low temperature polycrystalline silicon or oxide
System makees thin film transistor (TFT) (TFT), the image element circuit being made up of the thin film transistor (TFT), for controlling Organic Light Emitting Diode
It is luminous.However, finding in actual manufacture process, often there is threshold voltage shift phenomenon, partly lead using oxide in TFT devices
The TFT devices that system is made are particularly acute.As the brightness of pixel is controlled by image element circuit, the threshold voltage drift of TFT devices
Shifting can cause the brightness of pixel inconsistent.Therefore, existing OLED is difficult to show the image with uniform luminance.
Base this, how to solve existing OLED causes brightness due to thin film transistor (TFT) threshold voltage shift
The problem of lack of homogeneity, into those skilled in the art's technical problem urgently to be resolved hurrily.
The content of the invention
It is an object of the invention to provide a kind of image element circuit and its driving method and OLED, existing to solve
Some OLED cause the problem of brightness uniformity difference due to the threshold voltage shift of thin film transistor (TFT).
To solve the above problems, the present invention provides a kind of image element circuit, and the image element circuit includes：The first film crystal
Pipe, its first electrode are connected with data wire, and its second electrode is connected with primary nodal point, and its grid is connected to the first scan line；
Second thin film transistor (TFT), its first electrode are connected with the first power supply, its second electrode and Organic Light Emitting Diode
Anode connects, and its 3rd electrode is connected with secondary nodal point, and its grid is connected to primary nodal point；
3rd thin film transistor (TFT), its first electrode are connected with secondary nodal point, and its second electrode is connected with the 3rd power supply, its grid
Pole is connected to the first scan line；
4th thin film transistor (TFT), its first electrode are connected with the 3rd power supply, its second electrode and Organic Light Emitting Diode
Anode connects, and its grid is connected to the second scan line；
First electric capacity, is connected between the first power supply and primary nodal point；And
Second electric capacity, is connected between the first power supply and secondary nodal point.
Optionally, in described image element circuit, the negative electrode of the Organic Light Emitting Diode is connected with second source, described
First power supply and second source are used as the driving power supply of the Organic Light Emitting Diode；
3rd power supply is used to provide initialization voltage, and the initialization voltage is high level.
Optionally, in described image element circuit, the conducting of the first film transistor and the 3rd thin film transistor (TFT) and
End the first scanning signal control provided by the first scan line, the conducting of the 4th thin film transistor (TFT) and cut-off are by second
The current potential control of the second scanning signal control that scan line is provided, the conducting of second thin film transistor (TFT) and cut-off by primary nodal point
System.
Optionally, in described image element circuit, used as driving transistor, described second is thin for second thin film transistor (TFT)
Film transistor provides to the electric current of the Organic Light Emitting Diode data voltage that provided by data wire and the first power supply provides
The decision of first supply voltage, and it is unrelated with the threshold voltage of second thin film transistor (TFT).
Optionally, in described image element circuit, it is thin that the first film transistor to the 4th thin film transistor (TFT) is N-type
Film transistor.
Optionally, in described image element circuit, the first film transistor is indium gallium to the 4th thin film transistor (TFT)
Zinc oxide film transistor.
Accordingly, present invention also offers a kind of driving method of image element circuit, the driving method bag of the image element circuit
Include：Scan period includes first time period, second time period and the 3rd time period, wherein,
The second scanning letter that the first scanning signal provided in first time period, the first scan line and the second scan line are provided
Number it is changed into high level by low level, opens first film transistor, the 3rd thin film transistor (TFT) and the 4th thin film transistor (TFT), pass through
3rd power supply is initialized to the anode of secondary nodal point and Organic Light Emitting Diode；
In second time period, the first scanning signal that the first scan line is provided is changed into high level, the second scanning from low level
The second scanning signal that line is provided keeps low level, opens first film transistor and the is closed while three thin film transistor (TFT)s
Four thin film transistor (TFT)s, the data voltage write primary nodal point that data wire is provided；
In the 3rd time period, the first scanning signal that the first scan line is provided is changed into low level, the second scanning from high level
The second scanning signal that line is provided keeps low level, closes first film transistor, the 3rd thin film transistor (TFT) and the 4th thin film brilliant
Body pipe, the second thin film transistor (TFT) output current simultaneously drive the organic light-emitting diode.
Optionally, in the driving method of described image element circuit, in first time period, it is first that the 3rd power supply is provided
The data voltage that beginningization voltage and the data wire are provided is high level, and the voltage of the initialization voltage and data voltage
Threshold voltage of the difference equal to thin film transistor (TFT)；
In second time period, the data voltage that the data wire is provided is high level, and it is initial that the 3rd power supply is provided
Change voltage is low level；
The data voltage that the initialization voltage provided in the 3rd time period, the 3rd power supply and the data wire are provided is equal
For low level.
Optionally, in the driving method of described image element circuit, the scan period also included for the 4th time period, described
4th time period was arranged between first time period and second time period；
The second scanning letter that the first scanning signal provided in the 4th time period, the first scan line and the second scan line are provided
Number it is changed into low level by high level, closes first film transistor, the 3rd thin film transistor (TFT) and the 4th thin film transistor (TFT), stop
The anode of secondary nodal point and Organic Light Emitting Diode is initialized.
Accordingly, present invention also offers a kind of OLED, the OLED includes as above institute
The image element circuit stated.
In the image element circuit and its driving method and OLED that the present invention is provided, using the of four end structures
The threshold voltage of the second thin film transistor (TFT) is pre-stored within using the 3rd power supply as driving transistor by two thin film transistor (TFT)s
The source electrode of two thin film transistor (TFT)s so that the data voltage that the electric current that second thin film transistor (TFT) is subsequently exported is provided by data wire
Determine with the first supply voltage that the first power supply is provided, and it is unrelated with the threshold voltage of second thin film transistor (TFT), therefore energy
The brightness disproportionation for enough avoiding threshold voltage deviation from causing, thus, using the image element circuit and its organic light emission of driving method
Display can avoid the display problem caused by threshold voltage shift, so as to improve brightness uniformity.
Description of the drawings
Fig. 1 is the structural representation of the image element circuit of the embodiment of the present invention；
Fig. 2 is the structural representation of the second thin film transistor (TFT) of the embodiment of the present invention；
Fig. 3 is the sequential chart of the driving method of the image element circuit of the embodiment of the present invention.
Specific embodiment
Below in conjunction with the drawings and specific embodiments to a kind of image element circuit proposed by the present invention and its driving method and organic
Active display is described in further detail.According to following explanation and claims, advantages and features of the invention will be more clear
Chu.It should be noted that, accompanying drawing in the form of simplifying very much and uses non-accurately ratio, only to conveniently, lucidly
Aid in illustrating the purpose of the embodiment of the present invention.
Fig. 1 is refer to, which is the structural representation of the image element circuit of the embodiment of the present invention.As shown in figure 1, the pixel electricity
Road 20 includes：
First film transistor T1, its first electrode are connected with data wire Data, and its second electrode is connected with primary nodal point N1
Connect, its grid is connected to the first scan line Scan1；
Second thin film transistor (TFT) T2, its first electrode are connected with the first power supply ELVDD, its second electrode and organic light emission two
The anode connection of pole pipe OLED, its 3rd electrode are connected with secondary nodal point N2, and its grid is connected to primary nodal point N1；
3rd thin film transistor (TFT), its first electrode are connected with secondary nodal point N2, and its second electrode is connected with the 3rd power supply Ref
Connect, its grid is connected to the first scan line Scan1；
4th thin film transistor (TFT), its first electrode are connected with the 3rd power supply Ref, its second electrode and Organic Light Emitting Diode
The anode connection of OLED, its grid are connected to the second scan line Scan2；
First electric capacity C1, is connected between the first power supply ELVDD and primary nodal point N1；And
Second electric capacity C2, is connected between the first power supply ELVDD and secondary nodal point N2.
Specifically, the image element circuit 20 and Organic Light Emitting Diode OLED are received from outside (for example, from power supply) and are provided
The first power supply ELVDD, second source ELVSS and the 3rd power supply Ref.Wherein, the first power supply ELVDD is high potential pixel
Power supply, the second source ELVSS are low potential pixel powers, and the first power supply ELVDD and second source ELVSS is used as institute
State the driving power supply of Organic Light Emitting Diode OLED.
It should be appreciated that high potential pixel power herein is for low potential pixel power herein, i.e. described
The potential of the first power supply ELVDD is higher relative to second source ELVSS, and the potential of the second source ELVSS is relative to first
Power supply ELVDD is relatively low.
As shown in figure 1, the anode of the Organic Light Emitting Diode OLED is connected with image element circuit 20, the organic light emission two
The negative electrode of pole pipe OLED is connected with second source ELVSS, the image element circuit 20 and the first power supply ELVDD, second source ELVSS
Connect with the 3rd power supply Ref, the first power supply ELVDD is used to provide the first supply voltage VDD, the second source ELVSS
For providing second source voltage VSS, the 3rd power supply Ref is used to provide initialization voltage Vref, and the image element circuit 20 is used for
Control is fed to the driving current of the Organic Light Emitting Diode OLED.
Please continue to refer to Fig. 1, the image element circuit 20 is a kind of 4T2C types circuit structure, including 4 transistors and 2 it is electric
Hold.Wherein, first film transistor T1, the 3rd thin film transistor (TFT) T3 and the 4th thin film transistor (TFT) T4 are traditional three ends knot
Structure, three ends of three end structure are respectively first electrode, second electrode and grid.Second thin film transistor (TFT) T2 is tied for four ends
Structure, four ends of four end structure are respectively first electrode, second electrode, grid and coordination electrode.In first film transistor
In the thin film transistor (TFT) T4 of T1 to the 4th, first electrode and second electrode are different electrodes.For example, when first electrode is arranged to
During source electrode, second electrode is arranged to drain electrode.
Wherein, first film transistor T1 can select P-type TFT to the 4th thin film transistor (TFT) T4, also may be used
To select N-type TFT.Known, P-type TFT is turned on when signal is low level bit, and N-type thin film is brilliant
Body pipe is turned on when signal is high level position.Therefore, as long as by the transistor types of selection with electric conduction non-colinear position being
Can.
In the present embodiment, first film transistor T1 is N-type TFT to the 4th thin film transistor (TFT) T4.
Preferably, first film transistor T1 is indium gallium zinc oxide film crystal to the 4th thin film transistor (TFT) T4
Pipe (IGZO TFT).
Please continue to refer to Fig. 1, the conducting and cut-off of first film transistor T1 and the 3rd thin film transistor (TFT) T3 are by first
The first scanning signal control that scan line Scan1 is provided, write of first scanning signal for control data signal, the 4th
The second scanning signal control that the conducting and cut-off of thin film transistor (TFT) T4 is provided by the second scan line Scan2, described second sweeps
Retouch signal for control Organic Light Emitting Diode OLED anode voltage initialization, the conducting of the second thin film transistor (TFT) T2 and cut
Only by the control of Electric potentials of primary nodal point N1.
When the first scan line Scan1 provide the first scanning signal transit to high level when, first film transistor T1 and
3rd thin film transistor (TFT) T3 is turned on, and the data signal that data wire Data is provided writes primary nodal point via first film transistor T1
N1, while initialization voltage Vref that the 3rd power supply Ref is provided is applied to secondary nodal point N2 via the 3rd thin film transistor (TFT) T3.
When the second scanning signal that the second scan line Scan2 is provided transits to high level, the 4th thin film transistor (TFT) T4 is equal
Conducting, initialization voltage Vref that the 3rd power supply Ref is provided are applied to the organic light emission two via the 4th thin film transistor (TFT) T4
The anode of pole pipe OLED.
In the present embodiment, driving transistors of the second thin film transistor (TFT) T2 as pixel, corresponding to the electricity of primary nodal point N1
The driving current of the Organic Light Emitting Diode OLED is arrived in position to control offer, and the Organic Light Emitting Diode OLED is according to described
Driving current sends the light of corresponding brightness, so as to display image.
When the current potential of primary nodal point N1 is high level, the second thin film transistor (TFT) T2 conductings, the second thin film transistor (TFT) T2 are defeated
The driving current for going out along the first power supply ELVDD Jing the second thin film transistor (TFT) T2 and Organic Light Emitting Diode OLED path stream to the
Two power supply ELVSS, cause Organic Light Emitting Diode OLED to light luminous.
Fig. 2 is refer to, which is the structural representation of the second thin film transistor (TFT) of the embodiment of the present invention.As shown in Fig. 2 second
Grid 11 that thin film transistor (TFT) T2 includes being sequentially formed on substrate 10, gate insulator 12, raceway groove 13, source electrode 14, drain electrode 15
With coordination electrode 16, base of second thin film transistor (TFT) in traditional three end structures (i.e. grid 11, source electrode 14 and drain electrode 15)
Coordination electrode 16 is additionally arranged on plinth.As the second thin film transistor (TFT) T2 employs four end structures, therefore substantially increase electronics and move
Shifting rate.It is additionally, since between the coordination electrode 16 and source electrode 14, drain electrode 15 no any overlapping, therefore will not produces and post
The problems such as raw electric capacity.
In the present embodiment, the image element circuit 20 has threshold voltage compensation function, being capable of effective compensation driving transistor
Threshold voltage variation, cause brightness disproportionation phenomenon so as to avoid the threshold voltage shift of driving transistor.
Accordingly, present invention also offers a kind of driving method of image element circuit.Incorporated by reference to reference to Fig. 1 and Fig. 2, the picture
The driving method of plain circuit includes：
Scan period includes first time period t1, second time period t2 and the 3rd time period t 3, wherein,
The first scanning signal provided in first time period t1, the first scan line Scan1 and the second scan line Scan2 are provided
The second scanning signal be changed into high level by low level, open first film transistor T1, the 3rd thin film transistor (TFT) T3 and the
Four thin film transistor (TFT) T4, are carried out initially to the anode of secondary nodal point N2 and Organic Light Emitting Diode OLED by the 3rd power supply Ref
Change；
In second time period t2, the first scanning signal that the first scan line Scan1 is provided is changed into high level from low level, the
The second scanning signal that two scan lines Scan2 are provided keeps low level, opens first film transistor T1 and the 3rd film crystal
The 4th thin film transistor (TFT) T4 is closed while pipe T3, the data voltage Vdata write primary nodal point N1 that data wire Dm is provided；
In the 3rd time period t 3, the first scanning signal that the first scan line Scan1 is provided is changed into low level from high level, the
The second scanning signal that two scan lines Scan2 are provided keeps low level, closes first film transistor T1, the 3rd thin film transistor (TFT)
T3 and the 4th thin film transistor (TFT) T4, the second thin film transistor (TFT) T2 output currents simultaneously drive the Organic Light Emitting Diode OLED to send out
Light.
Specifically, in first time period t1, as the first scanning signal that the first scan line Scan1 is provided is become by low level
For high level, it is changed into leading from cut-off by first film transistor T1 and the 3rd thin film transistor (TFT) T3 of the control of the first scanning signal
It is logical, simultaneously because the second scanning signal that the second scan line Scan2 is provided is changed into high level from low level, by the second scanning signal
4th thin film transistor (TFT) T4 of control is also changed into conducting from cut-off.Therefore, the initialization voltage Vref Jing that the 3rd power supply Ref is provided
Secondary nodal point N2 is applied to by the 3rd thin film transistor (TFT) T3, at the same time, the initialization voltage Vref Jing that the 3rd power supply Ref is provided
The anode of Organic Light Emitting Diode OLED is applied to by the 4th thin film transistor (TFT) T4.
First time period t1 is initialization time section, during this period using the 3rd power supply Ref to Organic Light Emitting Diode
The anode of OLED is initialized.After initialization, the anode voltage of the Organic Light Emitting Diode OLED is initialization voltage
Vref。
In the process, as initialization voltage Vref is applied to secondary nodal point N2, therefore the electricity of secondary nodal point N2 simultaneously
Pressure is equal to initialization voltage Vref.As the data voltage Vdata that data wire Dm is provided is write via first film transistor T1
Primary nodal point N1, therefore the voltage (i.e. the grid voltage of the second thin film transistor (TFT) T2) of primary nodal point N1 is equal to Vdata.
In first time period t1, initialization voltage Vref and data voltage Vdata are high level, and described first
The voltage difference of beginningization voltage Vref and data voltage Vdata is equal to the threshold voltage vt h of thin film transistor (TFT).Now, the second thin film
Transistor T2 opens (i.e. in the conduction state), and the threshold voltage vt h of thin film transistor (TFT) is stored in the second thin film transistor (TFT) T2's
Source electrode.
In second time period t2, as the first scanning signal that the first scan line Scan1 is provided is changed into high electricity from low level
Flat, first film transistor T1 and the 3rd thin film transistor (TFT) T3 controlled by the first scanning signal is changed into conducting from cut-off, while
As the second scanning signal that the second scan line Scan2 is provided remains low level, the 4th by the control of the second scanning signal is thin
Film transistor T4 keeps cut-off state.
Now, initialization voltage Vref that the 3rd power supply Ref is provided is continued on through and is applied to the by the 3rd thin film transistor (TFT) T3
Two node N2, initialization voltage Vref that at the same time the 3rd power supply Ref is provided cannot apply via the 4th thin film transistor (TFT) T4
To the anode of Organic Light Emitting Diode OLED.
Second time period t2 is data write phase, and the data voltage Vdata that data wire Dm is provided during this period is via the
One thin film transistor (TFT) T1 writes primary nodal point N1, thus data voltage Vdata is stored in storage capacitance C1.
Now, the voltage of primary nodal point N1 is equal to data voltage Vdata, and the voltage of secondary nodal point N2 is equal to initialization voltage
Vref.As the data voltage Vdata is high level in second time period t2, initialization voltage Vref is in the second time
Section t2 is low level, therefore the second thin film transistor (TFT) T2 is although in the conduction state, but ON state current will compared with first time period t1
It is little.
In the 3rd time period t 3, as the first scanning signal that the first scan line Scan1 is provided is changed into low electricity from high level
Flat, first film transistor T1 and the 3rd thin film transistor (TFT) T3 controlled by the first scanning signal is changed into cut-off from conducting, while
As the second scanning signal that the second scan line Scan2 is provided keeps low level, by the 4th thin film that the second scanning signal is controlled
Transistor T4 keeps cut-off state.
Now, the data voltage Vdata that initialization voltage Vref and the data wire that the 3rd power supply is provided is provided
It is low level.As the voltage of primary nodal point N1 is still high level, thus the second thin film transistor (TFT) T2 conductings, the second thin film crystalline substance
Body pipe T2 output currents simultaneously drive the Organic Light Emitting Diode OLED to light.
3rd time period t 3 is glow phase, and now the source voltage of the second thin film transistor (TFT) T2 is VDD+ | Vth |, second
Voltage of the grid voltage of thin film transistor (TFT) T2 equal to primary nodal point N1, i.e. Vdata, therefore, the grid of the second thin film transistor (TFT) T2
The computing formula of source voltage Vgs (voltage difference between the grid and source electrode of i.e. described second thin film transistor (TFT) T2) is：
Vgs=(VDD+ | Vth |)-Vdata formula 1；
And the computing formula for flowing through the electric current Ion of the Organic Light Emitting Diode OLED is：
Ion=K × (Vgs- | Vth |)2Formula 2；
Wherein, K be the electron mobility of transistor, breadth length ratio, the product of unit-area capacitance three.
Can be obtained according to formula 1 and formula 2：
Ion=K × (VDD-Vdata)2Formula 3；
Knowable to expression formula based on formula 3, electric current Ion and the data voltage of the Organic Light Emitting Diode OLED are flow through
The the first supply voltage VDD and constant K that Vdata and the first power supply ELVDD is provided is relevant, with second source ELVSS offers
All it doesn't matter for the threshold voltage vt h of second source voltage VSS and the second thin film transistor (TFT) T2.Therefore, even if the second thin film
There is deviation in the threshold voltage vt h of transistor T2, will not also the electric current Ion for flowing through the Organic Light Emitting Diode OLED be caused
Affect.Therefore, the compensation of threshold voltage can be realized using the image element circuit 20 and its driving method, it is to avoid because of threshold voltage
Deviation and cause brightness disproportionation phenomenon.
Please continue to refer to Fig. 1 and Fig. 2, the scan period also includes the 4th time period t 4, and the 4th time period t 4 is arranged at
Between first time period t1 and second time period t2.In the 4th time period t 4, the first scanning letter that the first scan line Scan1 is provided
Number and the second scanning signal for providing of the second scan line Scan2 be changed into low level by high level, close first film transistor
T1, the 3rd thin film transistor (TFT) T3 and the 4th thin film transistor (TFT) T4, stop to secondary nodal point N2's and Organic Light Emitting Diode OLED
Anode is initialized.
Initialization voltage Vref and data voltage Vdata are low level in the 4th time period t 4, therefore second thin
Film transistor T2 opens (i.e. in the conduction state)
Repeat the course of work of first time period t1, the 4th time period t 4, second time period t2 and the 3rd time period t 3, it is complete
Into image display function.
In the driving method of the image element circuit that the present embodiment is provided, initialization time section is first passed through by threshold voltage vt h
The source electrode of driving transistor (i.e. the second thin film transistor (TFT) T2) is stored in, afterwards using the gate source voltage difference of driving transistor by threshold
Threshold voltage Vth offsets, so as to reach compensation purpose.
Accordingly, present invention also offers a kind of active matrix/organic light emitting display, the active matrix organic light-emitting
Display includes image element circuit as above 20.Specifically refer to above, here is omitted.
To sum up, in the image element circuit and its driving method and OLED that the present invention is provided, tied using four ends
The threshold voltage of the second thin film transistor (TFT) is deposited in advance using the 3rd power supply by the second thin film transistor (TFT) of structure as driving transistor
It is stored in the source electrode of the second thin film transistor (TFT) so that the number that the electric current that second thin film transistor (TFT) is subsequently exported is provided by data wire
The the first supply voltage decision provided according to voltage and the first power supply, and it is unrelated with the threshold voltage of second thin film transistor (TFT),
Therefore, it is possible to the brightness disproportionation for avoiding threshold voltage deviation from causing, thus, having using the image element circuit and its driving method
Machine active display can avoid the display problem caused by threshold voltage shift, so as to improve brightness uniformity.
Foregoing description is only the description to present pre-ferred embodiments, not any restriction to the scope of the invention, this
Any change that the those of ordinary skill in bright field is done according to the disclosure above content, modification, belong to the protection of claims
Scope.
Claims (10)
1. a kind of image element circuit, it is characterised in that include：
First film transistor, its first electrode are connected with data wire, and its second electrode is connected with primary nodal point, and its grid connects
To the first scan line；
Second thin film transistor (TFT), its first electrode are connected with the first power supply, the anode of its second electrode and Organic Light Emitting Diode
Connection, its 3rd electrode are connected with secondary nodal point, and its grid is connected to primary nodal point；
3rd thin film transistor (TFT), its first electrode are connected with secondary nodal point, and its second electrode is connected with the 3rd power supply, and its grid connects
It is connected to the first scan line；
4th thin film transistor (TFT), its first electrode are connected with the 3rd power supply, the anode of its second electrode and Organic Light Emitting Diode
Connection, its grid are connected to the second scan line；
First electric capacity, is connected between the first power supply and primary nodal point；And
Second electric capacity, is connected between the first power supply and secondary nodal point.
2. image element circuit as claimed in claim 1, it is characterised in that the negative electrode and second source of the Organic Light Emitting Diode
Connection, first power supply and second source are used as the driving power supply of the Organic Light Emitting Diode；
3rd power supply is used to provide initialization voltage, and the initialization voltage is high level.
3. image element circuit as claimed in claim 1, it is characterised in that the first film transistor and the 3rd thin film transistor (TFT)
Conducting and cut-off by the first scan line provide the first scanning signal control, the conducting of the 4th thin film transistor (TFT) and cut
The the second scanning signal control for only being provided by the second scan line, the conducting and cut-off of second thin film transistor (TFT) is by primary nodal point
Control of Electric potentials.
4. image element circuit as claimed in claim 1, it is characterised in that second thin film transistor (TFT) as driving transistor,
Second thin film transistor (TFT) provides to the electric current of the Organic Light Emitting Diode data voltage and first provided by data wire
The first supply voltage decision that power supply is provided, and it is unrelated with the threshold voltage of second thin film transistor (TFT).
5. image element circuit as claimed in claim 1, it is characterised in that the first film transistor is to the 4th thin film transistor (TFT)
It is N-type TFT.
6. image element circuit as claimed in claim 1, it is characterised in that the first film transistor is to the 4th thin film transistor (TFT)
It is indium gallium zinc oxide thin film transistor (TFT).
7. a kind of driving method of the image element circuit as any one of claim 1 to 6, it is characterised in that scan period
Including first time period, second time period and the 3rd time period, wherein,
The second scanning signal that the first scanning signal provided in first time period, the first scan line and the second scan line are provided is equal
High level is changed into from low level, first film transistor, the 3rd thin film transistor (TFT) and the 4th thin film transistor (TFT) is opened, by the 3rd
Power supply is initialized to the anode of secondary nodal point and Organic Light Emitting Diode；
In second time period, the first scanning signal that the first scan line is provided is changed into high level from low level, and the second scan line is carried
For the second scanning signal keep low level, open first film transistor and that the 4th is closed while three thin film transistor (TFT)s be thin
Film transistor, the data voltage write primary nodal point that data wire is provided；
In the 3rd time period, the first scanning signal that the first scan line is provided is changed into low level from high level, and the second scan line is carried
For the second scanning signal keep low level, close first film transistor, the 3rd thin film transistor (TFT) and the 4th thin film transistor (TFT),
Second thin film transistor (TFT) output current simultaneously drives the organic light-emitting diode.
8. the driving method of image element circuit as claimed in claim 7, it is characterised in that in first time period, the described 3rd is electric
The data voltage that the initialization voltage and the data wire that source provides is provided is high level, and the initialization voltage and data
The voltage difference of voltage is equal to the threshold voltage of thin film transistor (TFT)；
In second time period, the data voltage that the data wire is provided is high level, the initialization electricity that the 3rd power supply is provided
Press as low level；
The data voltage that the initialization voltage provided in the 3rd time period, the 3rd power supply and the data wire are provided is low
Level.
9. the driving method of image element circuit as claimed in claim 7, it is characterised in that when the scan period also includes the 4th
Between section, the 4th time period is arranged between first time period and second time period；
The second scanning signal that the first scanning signal provided in the 4th time period, the first scan line and the second scan line are provided is equal
Low level is changed into from high level, first film transistor, the 3rd thin film transistor (TFT) and the 4th thin film transistor (TFT) is closed, is stopped to the
The anode of two nodes and Organic Light Emitting Diode is initialized.
10. a kind of OLED, it is characterised in that include the pixel electricity as any one of claim 1 to 6
Road.
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| CN201610932065.9A CN106652910B (en) | 2016-10-31 | 2016-10-31 | Pixel circuit, driving method thereof and organic light emitting display |
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| CN106652910B (en) | 2019-12-24 |
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