Summary of the invention
Based on this, it is necessary to be not easy the technical issues of being unfolded for grayscale adjacent in traditional technology, provide a kind of pixelCircuit, its driving method and display device.
A kind of pixel circuit, comprising: transistor T1, transistor T2, transistor T3, transistor T4, transistor T5, transistorT6, transistor T7, capacitor C1 and Organic Light Emitting Diode OLED；The control terminal of the transistor T4 is for inputting the first scanning letterNumber, the first pole of the transistor T4 connects the second pole of the transistor T3, the control terminal of the transistor T1 and the capacitorOne end of C1, the second pole of another termination of capacitor C1 transistor T2, the second pole of the transistor T5 and describedThe first pole of transistor T1；The control terminal of the transistor T5 is used to input the first LED control signal, the transistor T5'sFirst pole is for inputting the first power supply signal VDD；The second pole of the transistor T4 is used for input reference voltage Vref, andConnect the second pole of the transistor T7；The control terminal of the transistor T2 is for inputting the second scanning signal, the transistor T2The first pole be used for input data voltage；The control terminal of the transistor T3 is for inputting the second scanning signal, the transistorThe first pole of T3 connects the second pole of the transistor T1 and the first pole of the transistor T6；The control terminal of the transistor T6 is usedIn inputting the second LED control signal, the second pole of the transistor T6 connects the first pole of the transistor T7；The transistorFor the control terminal of T7 for inputting the first scanning signal, the first pole of the transistor T7 connects the Organic Light Emitting Diode OLED'sInput terminal；The output end of the Organic Light Emitting Diode OLED is for inputting second source signal VSS.
The transistor T1, the transistor T2, the transistor T3, the transistor in one of the embodiments,T4, the transistor T5, the transistor T6 and the transistor T7 are that low-temperature polysilicon film transistor, oxide are partly ledAny one of body thin film transistor and amorphous silicon film transistor.
The transistor T1, the transistor T2, the transistor T3, the transistor in one of the embodiments,T4, the transistor T5, the transistor T6 and the transistor T7 are P-type TFT.
The reference voltage Vref is lower than the second source voltage VSS in one of the embodiments,.
A kind of display device, comprising: the pixel circuit as described in above-mentioned any embodiment.
A kind of driving method of pixel circuit, the driving method based on pixel circuit described in any of the above-described embodiment,Include:
Initial phase, first scanning signal and first LED control signal are low level signal, describedSecond scanning signal and second LED control signal are high level signal；The reference voltage Vref, for initializingThe control terminal of the anode of the Organic Light Emitting Diode OLED, the transistor T1；
Memory phase, first scanning signal, first LED control signal and second LED control signalIt is high level signal, second scanning signal is low level signal；The data voltage Vdata is used for offset voltageThe capacitor C1 is written；
Light emitting phase, first scanning signal and second scanning signal are high level signal, first hairOptical control signal and second LED control signal are low level signal；The first supply voltage VDD, for being supplied toThe Organic Light Emitting Diode OLED is so that the Organic Light Emitting Diode OLED shines.
In one of the embodiments, in the initial phase, the transistor T5 is believed by first light emitting controlNumber conducting, the first supply voltage VDD connects one end of second pole transistor T5 for initializing the capacitor C1.
In one of the embodiments, in the initial phase, the transistor T4 is led by first scanning signalLogical, the reference voltage Vref connects one end of the transistor T1 control terminal for initializing the capacitor C1.
In one of the embodiments, in the memory phase, the transistor T5 is by first LED control signalCut-off, the transistor T2 are connected by second scanning signal, and the current potential of the first pole of the transistor T1 is equal to data electricityPress Vdata；The current potential of the control terminal of the transistor T1 is equal to Vdata- | Vth |.
In one of the embodiments, in the light emitting phase, the transistor T5 is by first LED control signalConducting, the transistor T4 are ended by first scanning signal, and the transistor T3 is ended by second scanning signal, instituteThe current potential for stating the first pole of transistor T1 is equal to the first supply voltage VDD；The current potential of the control terminal of the transistor T1 is equal toVdata-|Vth|+η(VDD-Vdata)；Wherein, η is that the total capacitance at the capacitor C1 and the transistor T1 control terminal removes electricityHold the dividing ratios coefficient that other capacitors C2 except C1 is determined.
Above-mentioned pixel circuit, its driving method and display device, the pixel circuit include transistor T1, transistor T2, crystalline substanceBody pipe T3, transistor T4, transistor T5, transistor T6, transistor T7, capacitor C1 and Organic Light Emitting Diode OLED.InitialChange stage, reference voltage Vref are added in the anode of Organic Light Emitting Diode OLED through transistor T7, realize Organic Light Emitting DiodeThe initialization of the anode of OLED, reference voltage Vref are added in the control terminal of transistor T1 through transistor T4, initialization transistorThe control terminal of T1.During light emitting phase, transistor T5 is connected by the first LED control signal, the electricity of the first pole of transistor T1Position becomes the first supply voltage VDD from data voltage Vdata, since transistor T3 and transistor T4 is in off state, capacitorThe electricity of C1 remains unchanged, and the current potential of the control terminal of transistor T1 is from Vdata- | Vth | become Vdata- | and Vth |+η (VDD-Vdata), to flow through coefficient (η -1) 2 in the current formula of Organic Light Emitting Diode OLED, since η is close to 1, so adjacent ashThe corresponding data voltage Vdata value of rank can have biggish difference, so that solving grayscale is not easy the technical issues of being unfolded.
Specific embodiment
In order to make the foregoing objectives, features and advantages of the present invention clearer and more comprehensible, with reference to the accompanying drawing to the present inventionSpecific embodiment be described in detail.Many details are explained in the following description in order to fully understand this hairIt is bright.But the invention can be embodied in many other ways as described herein, those skilled in the art can be notSimilar improvement is done in the case where violating intension of the present invention, therefore the present invention is not limited by the specific embodiments disclosed below.
In one embodiment, referring to Figure 1, the application provides a kind of pixel circuit, which includes: transistorT1, transistor T2, transistor T3, transistor T4, transistor T5, transistor T6, transistor T7, capacitor C1 and organic light-emitting diodesPipe OLED.Wherein, transistor T1 to transistor T7 includes control terminal, the first pole and the second pole.
Specifically, the control of transistor T4 terminates the first scanning signal end, transmits for inputting through the first scan signal lineThe first scanning signal SCAN1.The first pole of transistor T4 connects the control terminal and capacitor of the second pole of transistor T3, transistor T1One end of C1, the first pole of the second pole of another termination transistor T2 of capacitor C1, the second pole of transistor T5 and transistor T1.
The control of transistor T5 terminates the first light emitting control end, for inputting the first hair through the transmission of the first light emitting control lineThe first pole of optical control signal EM1, transistor T5 connect the first power supply, for inputting the first supply voltage VDD.
The second pole of transistor T4 is used for input reference voltage Vref, and connects the second pole of transistor T7.
The control terminal of transistor T2 is for inputting the second scanning signal SCAN2, and the first pole of transistor T2 is for inputting numberAccording to voltage Vdata.
The control of transistor T3 terminates the second scanning signal end, second sweeps for input through the second scan signal line transmitsSignal SCAN2 is retouched, the first pole of transistor T3 connects the second pole of transistor T1 and the first pole of transistor T6.
The control of transistor T6 terminates the second light emitting control end, for inputting the first hair through the transmission of the second light emitting control lineThe second pole of optical control signal EM2, transistor T6 connect the first pole of transistor T7.
The control of transistor T7 terminates the first scanning signal end, first sweeps for input through the first scan signal line transmitsSignal SCAN1 is retouched, the first pole of transistor T7 connects the input terminal of Organic Light Emitting Diode OLED.
The output of Organic Light Emitting Diode OLED terminates second source, for inputting second source voltage VSS.
Wherein, transistor T2, transistor T3, transistor T4, transistor T5, transistor T6 and transistor T7 are pixel circuitsIn switching transistor.Transistor T1 is the driving transistor in pixel circuit.Capacitor C1 is storage capacitor, is connected to transistorBetween the control terminal of T1 and the first pole of transistor T1.
In the present embodiment, the first scanning signal SCAN1 controls the cut-off or conducting of transistor T4, transistor T7, theThe cut-off or conducting of two scanning signal SCAN2 control transistor T2, transistor T3.First LED control signal EM1 control is brilliantThe cut-off or conducting of body pipe T5.The cut-off or conducting of second LED control signal EM2 control transistor T6.As transistor T4When conducting, control terminal of the reference voltage Vref through transistor T4 initialization transistor T1.When transistor T7 conducting, reference voltageAnode of the Vref through transistor T7 initialization Organic Light Emitting Diode OLED.When transistor T5 conducting when, initialization capacitor C1 withThe pole plate of the second pole transistor T5 connection.When transistor T2 and transistor T3 are connected, data voltage Vdata through transistor T2,Transistor T1, transistor T3 are added in the grid of driving transistor T1.When transistor T5 and transistor T6 is connected, the first power supply electricityPressure VDD adds to Organic Light Emitting Diode OLED, Organic Light Emitting Diode OLED hair through transistor T5, transistor T1 and transistor T6Light.
In one embodiment, transistor T1, transistor T2, transistor T3, transistor T4, transistor T5, transistor T6And transistor T7 is in low-temperature polysilicon film transistor, oxide semiconductor thin-film transistor and amorphous silicon film transistorIt is any.Transistor T1, transistor T2, transistor T3, transistor T4, transistor T5, transistor T6 and transistor T7 can be withUsing P-type TFT, N-type TFT can also be used.In use P-type TFT as in pixel circuitWhen transistor, to the control terminal input low level signal for the transistor that needs are connected；In use N-type TFT as pixelWhen transistor in circuit, to the control terminal input high level signal for the transistor that needs are connected.
In one embodiment, refer to Fig. 2, transistor T1 that pixel circuit provided by the present application uses, transistor T2,Transistor T3, transistor T4, transistor T5, transistor T6 and transistor T7 are P-type TFT.It is possible to understand, control terminal can be the grid of transistor T1 to transistor T7, and the first pole can be transistor T1 to the source of transistor T7Pole, the second pole can be the drain electrode of transistor T1 to transistor T7.
In one embodiment, reference voltage Vref is lower than second source voltage VSS.Wherein, in light emitting phase, the first electricitySource voltage VDD adds to Organic Light Emitting Diode OLED, Organic Light Emitting Diode through transistor T5, transistor T1 and transistor T6OLED shines.Under the action of flowing through the forward current of Organic Light Emitting Diode OLED, hole accumulation and indium oxide will causeIndium ion is mobile in tin, accelerates the aging of Organic Light Emitting Diode OLED.In initial phase, by the way that reference voltage is arrangedVref is lower than second source signal VSS, reverse bias is carried out to Organic Light Emitting Diode OLED, so that compensating light emitting phase causesAging, and then extend the service life of Organic Light Emitting Diode OLED.
In one embodiment, the application provides the driving method that circuit is moved based on the pixel in any of the above-described embodiment,The driving method successively includes:
Initial phase t1, the first scanning signal SCAN1 and the first LED control signal EM1 are low level signal, theTwo scanning signal SCAN2 and the second LED control signal EM2 are high level signal.Reference voltage Vref has for initializingThe control terminal of the anode of machine light emitting diode OLED, transistor T1.
Memory phase t2, the first scanning signal SCAN1, the first LED control signal EM1 and the second LED control signal EM2It is high level signal, the second scanning signal SCAN2 is low level signal.Data voltage Vdata, for offset voltage to be writtenCapacitor C1.
Light emitting phase t3, the first scanning signal SCAN1 and the second scanning signal SCAN2 are high level signal, the first hairOptical control signal EM1 and the second LED control signal EM2 is low level signal.First supply voltage VDD, for being supplied toMachine light emitting diode OLED is so that Organic Light Emitting Diode OLED shines.
Fig. 3 is referred to, Fig. 3 is the corresponding signal timing diagram of the driving method, wherein signal timing diagram includes initialization rankSection t1, memory phase t2 and light emitting phase t3.Specifically the course of work is as follows:
It is low level signal, transistor T1, transistor T4, transistor in initial phase t1, the first scanning signal SCAN1T7 conducting, reference voltage Vref initialize the anode of Organic Light Emitting Diode OLED and the control terminal of transistor T1.First shinesControl signal EM1 is low level signal, transistor T5 conducting, and the first supply voltage VDD initializes capacitor C1 and transistor T1 theFirst pole plate of one pole connection.To which the current potential of capacitor C1 the first pole plate connecting with the second pole transistor T5 is equal to the first power supplyThe current potential for the second pole plate that voltage VDD, capacitor C1 are connect with transistor T1 control terminal is equal to reference voltage Vref.Second scanning letterNumber SCAN2 and the second LED control signal EM2 is high level signal, transistor T2, transistor T3, transistor T5 and transistorT6 cut-off, no driving current flows through Organic Light Emitting Diode OLED, so that it does not shine.
In memory phase t2, the first scanning signal SCAN1, the first LED control signal EM1 and the second LED control signalEM2 is high level signal, transistor T4, transistor T5, transistor T6 and transistor T7 cut-off, the second scanning signal SCAN2For low level signal, transistor T2 and transistor T3 conducting.The current potential of the first pole of transistor T1 is equal to data voltage Vdata,The current potential of the control terminal of transistor T1 is equal to Vdata- | Vth |.Control terminal, the first pole pole difference of transistor T1 of transistor T1The two-plate of capacitor C1 is connect, offset voltage | Vth | write-in capacitor C1.
Specifically, transistor T5 is ended by the first LED control signal EM1, and transistor T2 is by the second scanning signal SCAN2The current potential of conducting, the first pole of transistor T1 is equal to data voltage Vdata.The current potential of the control terminal of transistor T1 is equal to Vdata-|Vth|。
It is high level signal, crystal in light emitting phase t3, the first scanning signal SCAN1 and the second scanning signal SCAN2Pipe T4, transistor T7 cut-off, transistor T2, transistor T3 cut-off.First LED control signal EM1 and the second LED control signalEM2 is low level signal, and transistor T5, transistor T6 conducting, the first supply voltage VDD is through transistor T5, driving transistorT1 and transistor T6 add to Organic Light Emitting Diode OLED, so that Organic Light Emitting Diode OLED shines.
Specifically, the first pole plate of capacitor C1 connects the first pole of transistor T1, and the second pole plate of capacitor C1 meets transistor T1Control terminal.Transistor T5 is connected by the first LED control signal EM1, and the current potential of the first pole plate of capacitor C1 is equal to the first power supplyVoltage VDD.It is equal to Vdata in the current potential of memory phase t2, the first pole plate of capacitor C1, then the potential change of the first pole plate of capacitor C1Amount are as follows: VDD-Vdata.Also, other capacitors of the total capacitance at transistor T1 control end node in addition to capacitor C1 are denoted as C2, andThe partial pressure effect of other capacitors C2 further influences the current potential of the second pole plate of capacitor C1, then the current potential of the second pole plate of capacitor C1 is equal toVdata-|Vth|+η(VDD-Vdata).Wherein, η is that the total capacitance that capacitor C1 and transistor T1 is controlled at end node removes capacitor C1Except other capacitors C2 determine dividing ratios coefficient.
In the present embodiment, the current potential of the first pole of transistor T1 becomes the first supply voltage from data voltage VdataVDD, since transistor T3 and transistor T4 is in off state, the electricity of capacitor C1 is remained unchanged, the control terminal of transistor T1Current potential from Vdata- | Vth | become Vdata- | Vth |+η (VDD-Vdata), to flow through Organic Light Emitting Diode OLED'sCoefficient (η -1) 2 in current formula, since η is close to 1, so the corresponding data voltage Vdata value of adjacent grayscale can haveBiggish difference can accurately control the corresponding data voltage of adjacent grayscale, so that solving grayscale is not easy the technical issues of being unfolded.
It is worked below with reference to the driving method pixels illustrated circuit of the pixel circuit and pixel circuit in above-described embodimentJourney.Refer to Fig. 2 and Fig. 3, wherein Fig. 3 is the corresponding signal timing diagram of the driving method, and signal timing diagram includes initialization rankSection t1, memory phase t2 and light emitting phase t3.Specifically the course of work is as follows:
It is low level signal, transistor T4 conducting, reference voltage in initial phase t1, the first scanning signal SCAN1The grid of Vref initialization transistor T1.First scanning signal SCAN1 is low level signal, transistor T7 conducting, reference voltageThe anode of Vref initialization Organic Light Emitting Diode OLED.First LED control signal EM1 be low level signal, transistor T5 byFirst LED control signal EM1 conducting, the first supply voltage VDD add to the first pole plate of capacitor C1.Due to the grid of transistor T1Pole connects the second pole plate of capacitor C1, to initialize to capacitor C1 two-plate, i.e. capacitor C1 first in initial phaseThe current potential of pole plate is equal to the first supply voltage VDD, and the current potential of the second pole plate of capacitor C1 is equal to reference voltage Vref.Avoid previous framePicture point time, which is stored in the dump energy in capacitor C1, influences sampling of the current frame pixel time to threshold voltage.Second scanning letterNumber be high level signal, transistor T2, transistor T3 cut-off.Second LED control signal EM2 is high level signal, transistorT5, transistor T6 cut-off, no driving current flows through Organic Light Emitting Diode OLED, so that it does not shine.
In memory phase t2, the first scanning signal SCAN1, the first LED control signal EM1 and the second LED control signalEM2 is high level signal, transistor T4, transistor T5, transistor T6 and transistor T7 cut-off.Second scanning signal SCAN2For low level signal, transistor T2 and transistor T3 conducting.Data voltage Vdata adds to the source of transistor T1 through transistor T2Pole, until transistor T1 is in critical state, the current potential of the source electrode of transistor T1 is equal to data voltage Vdata, transistor T1'sThe current potential of grid is equal to Vdata- | Vth |.Since the source electrode pole of the grid of transistor T1, transistor T1 connect the two of capacitor C1 respectivelyPole plate, thus offset voltage | Vth | write-in capacitor C1.
At this point, the grid voltage of transistor T2 is Vdata- | Vth |, wherein Vth is the threshold voltage of transistor T1, andThe value of the threshold voltage is negative value, then the grid voltage Vdata+Vth of transistor T1.
It is high level signal, crystal in light emitting phase t3, the first scanning signal SCAN1 and the second scanning signal SCAN2Pipe T4, transistor T7 cut-off, transistor T2, transistor T3 cut-off.First LED control signal EM1 and the second LED control signalEM2 is low level signal, and transistor T5, transistor T6 conducting, the first supply voltage VDD is through transistor T5, driving transistorT1 and transistor T6 add to Organic Light Emitting Diode OLED, so that Organic Light Emitting Diode OLED shines.
The first pole plate of capacitor C1 connects the source electrode of transistor T1, and the second pole plate of capacitor C1 connects the grid of transistor T1, thenThe current potential of the current potential of source electrode of the current potential of the first pole plate of capacitor C1 equal to transistor T1, the second pole plate of capacitor C1 is equal to crystalThe current potential of the grid of pipe T1.Transistor T5 is connected by the first LED control signal EM1, and the current potential of the source electrode of transistor T1 is equal to theThe current potential of the first pole plate of one supply voltage VDD, capacitor C1 is equal to the first supply voltage VDD.
Since transistor T3 ends, the electricity of capacitor C1 is remained unchanged, and the voltage difference between capacitor C1 two-plate is also keptConstant, i.e., the current potential of the first pole plate of capacitor C1 changes with the potential change of the second pole plate of capacitor C1.
It is equal to Vdata in the current potential of memory phase t2, the first pole plate of capacitor C1；
In from memory phase t2 to the time phase of light emitting phase t3, the potential change amount of the first pole plate of capacitor C1 are as follows:VDD-Vdata。
Also, other capacitors of the total capacitance at transistor T1 gate node in addition to capacitor C1 are denoted as C2, and other capacitorsThe partial pressure effect of C2 further influences the current potential of the second pole plate of capacitor C1, then the current potential of the second pole plate of capacitor C1 is equal to Vdata+Vth+η(VDD-Vdata)。
Wherein η=C1/ (C1+C2), i.e. η are the total capacitance at capacitor C1 and transistor T1 gate node in addition to capacitor C1Other capacitors C2 determine dividing ratios coefficient.
The second pole plate of capacitor C1 connects the grid of transistor T1, then the current potential of the grid of transistor T1 is equal to Vdata+Vth+η(VDD-Vdata)。
The gate-source pressure drop of transistor T1 are as follows: Vgs=Vg-Vs；
Vgs=Vdata+Vth+ η (VDD-Vdata)-VDD；
Vgs=(1- η) * (VDD-Vdata)+Vth；
Driving current size in transistor T1:
I=K* (Vgs-Vth)2=K* (1- η)2*(VDD-Vdata)2；
Wherein, K=1/2* μ * Cox*W/L.μ is the electron mobility of thin film transistor (TFT), and Cox is thin film transistor (TFT) unit planeLong-pending gate oxide capacitance, W are the channel widths of thin film transistor (TFT), and L is the channel length of thin film transistor (TFT).
Therefore, the driving current size in available the first transistor T1 are as follows:
I=1/2* μ * Cox*W/L*(1-η)2*(VDD-Vdata)2
It is available from above-mentioned formula, flow through the current formula inlet coefficient (η -1) 2, η of Organic Light Emitting Diode OLEDClose to 1, so the corresponding data voltage of adjacent grayscale can have biggish difference, reduces and solve what grayscale was not easy to be unfoldedTechnical problem.In addition, the driving current size in transistor T1 is unrelated with the threshold voltage vt h size of transistor T2, thus realExisting threshold voltage compensation, so that the brightness stability of Organic Light Emitting Diode OLED.
In one embodiment, the application provides a kind of display device, refers to Fig. 4, which includes:
Multiple pixels, for showing image.Each pixel packet appoints the pixel circuit in said one embodiment.
Scanning signal is applied sequentially to pixel by scanner driver 410.
LED control signal is applied to pixel by light emitting control driver 420.
Data voltage is applied to pixel by data driver 430.
Wherein, pixel response scanning signal and receive data voltage, pixel generate have it is corresponding with data voltage predeterminedThe light of brightness is to show image.The fluorescent lifetime section of pixel is controlled by LED control signal.Light emitting control driver is in response to firstBeginning control signal is initialised, and generates LED control signal.
Illustratively, Fig. 4 is referred to, scanner driver 410 is arranged by scan signal line S1 to Sn connection matrix formMultiple pixel PX11 to PXnm, pixel PX11 to PXnm is also connected to LED control signal line E1 to Em, and passes through the control that shinesSignal wire E1 to Em connection light emitting control driver 420 processed.Pixel PX11 to PXnm is also connected to data signal line D1 to Dm, andPass through data signal line D1 to Em connection data driver 430.Wherein, LED control signal line E1 to Em is roughly parallel to scanningSignal wire S1 to Sn.LED control signal line E1 to Em is approximately perpendicular to data signal line D1 to Dm.
Each technical characteristic of embodiment described above can be combined arbitrarily, for simplicity of description, not to above-mentioned realityIt applies all possible combination of each technical characteristic in example to be all described, as long as however, the combination of these technical characteristics is not depositedIn contradiction, all should be considered as described in this specification.
The embodiments described above only express several embodiments of the present invention, and the description thereof is more specific and detailed, but simultaneouslyIt cannot therefore be construed as limiting the scope of the patent.It should be pointed out that coming for those of ordinary skill in the artIt says, without departing from the inventive concept of the premise, various modifications and improvements can be made, these belong to protection of the inventionRange.Therefore, the scope of protection of the patent of the invention shall be subject to the appended claims.