Summary of the invention
The main technical problem to be solved in the present invention provides a kind of image element circuit and display device, can compensate the inhomogeneous OLED brightness disproportionation that causes because of poly-Si TFT threshold voltage under the prerequisite of the complexity that does not as far as possible increase peripheral IC complexity and image element circuit.
For this reason, the present invention proposes a kind of image element circuit, and it is disposed between the sweep trace of arranging with first direction that is used for supply control signal and the data line that is used for supplies data signals with the second direction arrangement, comprising:
The 4th transistor, the data-signal of the described data line supply that is used to sample;
Electric capacity;
The first transistor, it is luminous to be used for the driven for emitting lights device;
It is characterized in that also comprising: be used to provide power lead, transistor seconds and the 3rd transistor of power supply, wherein,
The described the 4th transistorized control utmost point is connected to the sweep trace that this image element circuit is expert at, the second current lead-through utmost point is connected to described data line, the first current lead-through utmost point is connected to the second current lead-through utmost point of described transistor seconds, is used at the data-signal of the valid period of given sequential conducting with the described data line supply of sampling;
First electrode of described electric capacity connects the control utmost point of described the first transistor and the control utmost point of described transistor seconds respectively, is used to described the first transistor and described transistor seconds that cut-in voltage is provided, and second electrode is connected to first power supply;
Described the first transistor is connected between described power lead and the ground by its first current lead-through utmost point and the second current lead-through utmost point, and provides electric current for luminescent device under the Control of Voltage of first electrode of described electric capacity;
The first current lead-through utmost point of described transistor seconds is joined together to form diode with its control utmost point and is connected;
The described the 3rd transistorized control utmost point is connected to the sweep trace of the previous row that this image element circuit is expert at, the second current lead-through utmost point is connected to first electrode of described electric capacity with the control utmost point of the first current lead-through utmost point of transistor seconds, the control utmost point and the first transistor, and the first current lead-through utmost point is connected to second source.
Further, described image element circuit also comprises: luminescent device, described luminescent device and described the first transistor are connected between described power lead and the ground.
Among a kind of embodiment, the plus earth of described luminescent device, anode is connected to the second current lead-through utmost point of described the first transistor; The first current lead-through utmost point of described the first transistor links to each other with described power lead; Described second source is described power lead; Described first power supply is ground or for the anode of described luminescent device or be described power lead.
Among the another kind of embodiment, the anode of described luminescent device is connected with described power lead, and its negative electrode is connected to the first current lead-through utmost point of described the first transistor; The second current lead-through utmost point ground connection of described the first transistor; Described second source is described power lead; Described first power supply is ground or is described power lead.
Preferably, described the first transistor, described transistor seconds, described the 3rd transistor, described the 4th transistor are N raceway groove polycrystalline SiTFT.
Among another embodiment, the plus earth of described luminescent device, its anode is connected to the second current lead-through utmost point of described the first transistor; First current lead-through of described the first transistor extremely directly links to each other with described power lead; Described second source is ground; Described first power supply is ground or for the anode of described luminescent device or be described power lead.
Wherein, described the first transistor, described transistor seconds, described the 3rd transistor, described the 4th transistor are P raceway groove polycrystalline SiTFT; Perhaps, described the first transistor and described transistor seconds are P raceway groove polycrystalline SiTFT, and described the 3rd transistor and described the 4th transistor are N raceway groove polycrystalline SiTFT.
In above-mentioned image element circuit, described luminescent device is an Organic Light Emitting Diode.
The present invention correspondingly provides a kind of display device, comprising:
Multi-strip scanning line with the first direction arrangement;
Scan drive circuit is used to produce sweep signal, and its output terminal is connected with the multi-strip scanning line respectively;
Many data lines with the second direction arrangement;
Data drive circuit is used to produce data-signal, and its output terminal is connected with many data lines respectively;
Also comprise a plurality of aforesaid image element circuits, described image element circuit is disposed between the described sweep trace and described data line that intersects.
Beneficial effect of the present invention is:
(1) image element circuit of the present invention only needs four thin film transistor (TFT)s and an electric capacity, compare with other image element circuit that can compensate threshold voltage with similar structures, circuit of the present invention is reducing under one to two transistorized prerequisite, can realize identical functions, therefore both can reduce the complexity and the cost of pixel, can improve aperture ratio of pixels again
(2) circuit structure that utilizes the different crystal pipe to form produces threshold voltage, reduce the influence of threshold voltage by the mirror of transistor seconds and the first transistor and the threshold voltage information of generation, thereby effectively compensation is because of the inhomogeneous brightness disproportionation that causes of threshold voltage to luminescent device;
(3) image element circuit of the present invention only need utilize sweep trace that this image element circuit is expert at, with and the sweep trace of previous row drive each transistor respectively, and existing peripheral IC just provides these sweep traces originally, therefore adopts the solution of the present invention not increase the complexity of peripheral driver IC.
Embodiment
In conjunction with the accompanying drawings the present invention is described in further detail below by embodiment.
Embodiment one:
Image element circuit as shown in Figure 2 comprises: power lead V
DD, data line V
DATA, the first transistor T1, transistor seconds T2, the 3rd transistor T 3, the 4th transistor T 4 and capacitor C
S
The sweep trace that described image element circuit is expert at is called one's own profession grid sweep trace V
N, N is a natural number; The sweep trace of the previous row that described image element circuit is expert at is called previous row grid sweep trace V
N-1
Power lead V
DDBe used to image element circuit that power supply is provided, this power lead provides the high level constant voltage source among each embodiment of this paper.
Be that example describes with the luminescent device for Organic Light Emitting Diode OLED among the embodiment.
The first transistor T1, transistor seconds T2, the 3rd transistor T 3 and the 4th transistor T 4, these four transistors are the N channel thin-film transistor among the embodiment, the transistorized control utmost point corresponds to the grid of TFT, the first current lead-through utmost point and the second current lead-through utmost point can reciprocity, promptly, first current lead-through extremely can be that source electrode also can be drain electrode, and accordingly, second current lead-through extremely can be that to drain also can be source electrode.
Annexation between each components and parts is:
The grid of the 4th transistor T 4 is connected to V
N, drain electrode is connected to data line V
DATA, source electrode is connected to the source electrode of transistor seconds T2, is used at the data-signal of the valid period of given sequential conducting with the described data line supply of sampling;
Capacitor C
SFirst electrode connect the grid of the first transistor T1 and the grid of transistor seconds T2 respectively, be used to the first transistor T1 and transistor seconds T2 that cut-in voltage is provided, second electrode is connected to first power supply, first power supply or be power lead V
DDPerhaps be ground or be the anode of OLED that first power supply is among the embodiment one, i.e. second electrode grounding;
The drain electrode of the first transistor T1 is connected to power lead V
DD, source electrode is received the anode of OLED;
The drain electrode of transistor seconds T2 is joined together to form diode with its grid and is connected;
The grid of the 3rd transistor T 3 is connected to V
N-1, source electrode is connected to capacitor C
SFirst electrode, the drain electrode be connected to second source, second source can be power lead V
DDPerhaps be ground, second source is power lead V among the embodiment one
DD, i.e. power lead is received in drain electrode;
The anode of OLED connects the source electrode of the first transistor T1, plus earth.
The course of work of circuit shown in the embodiment one as shown in Figure 4, is divided into three phases: pre-charging stage, programming phases and glow phase.
Pre-charging stage:
Grid sweep trace V
N-1Become high level by low level, V
NKeep low level, T4 closes, because T3 opens, makes capacitor C
sFirst electrode on current potential filled very highly, near V
DD
Programming phases:
Grid sweep trace V
N-1Become low level by high level, V
NBecome high level by low level, make T3 close, T4 opens.Capacitor C
sOn electric charge by the branch road discharge that T2 and T4 form, end up to T2, at this moment C
sElectromotive force on first electrode equals V
TH_T2+ V
DATA
Glow phase:
Grid sweep trace V
N-1, V
NAll become low level, T3 and T4 end; Programming phases C
sThe voltage of first electrode is saved to frame scan next time; The A point voltage provides electric current for OLED:
I=K(V
GS_T1-V
TH_T1)
2=K(V
DATA+V
TH_T2-V
OLED-V
TH_T1)
2
Owing to close on T1 and the T2 position, and adopt identical technology, can think that both threshold voltages equate, i.e. V
TH_T2=V
TH_T1, but so the following formula abbreviation is:
I=K(V
DATA-V
OLED)
2 (1)
V wherein
TH_T1And V
TH_T2The threshold voltage of representing T1 and T2 respectively, V
OLEDThe anode potential of expression glow phase OLED.K=0.5 μ C
OX(W/L) be gain factor, μ and C
OXBe respectively carrier mobility and the gate insulation layer electric capacity of TFT, W and L represent channel width and the length of TFT respectively.From following formula (1) as can be known, OLED electric current and TFT threshold voltage V
THIrrelevant, thus compensated the inhomogeneous brightness disproportionation that causes of threshold voltage.
The driving sequential of image element circuit shown in the embodiment one adopts the gate signal of the superior and the subordinate's pixel: the gate signal V in the circuit
N-1And V
NBecome high level successively in the entire frame scanning process, and identical, non-overlapping copies of duration in high level stage, the one's own profession grid sweep trace of previous row pixel that therefore can utilize a certain pixel on the panel is as V
N-1, one's own profession grid sweep trace V
NWhen providing sweep signal for the one's own profession pixel, and as the previous row grid sweep trace of next line pixel.This just is equivalent to every grade of pixel and only uses a scanning gate signal, and does not need extra grid sweep trace, has simplified peripheral drive IC greatly, and the complexity of pixel wiring also is lowered simultaneously.
Embodiment two:
Shown in Fig. 3 a, embodiment two and embodiment one different be in: first power supply is the anode voltage of OLED, promptly this moment capacitor C
sSecond electrode link to each other with the anode of OLED.
The circuit working process of embodiment two is identical with embodiment one, repeats no more herein.
Embodiment three:
Shown in Fig. 3 b, embodiment three and embodiment one different be in: first power supply is power lead V
DD, promptly this moment capacitor C
sSecond electrode and power lead V
DDLink to each other.
The circuit working process of embodiment three is identical with embodiment one, repeats no more herein.
Embodiment four:
Shown in Fig. 3 c, embodiment four and embodiment one different are in power lead V
DDLink to each other with the anode of OLED, the negative electrode of OLED is connected to the drain electrode of the first transistor T1, the source ground of the first transistor T1.
The circuit working process of embodiment four and the difference of embodiment one are: in glow phase, the OLED electric current is I=K (V
DATA)
2Reach same brightness this moment, and required data voltage is littler.
Embodiment five:
Shown in Fig. 3 d, embodiment five and embodiment three different are in power lead V
DDLink to each other with the anode of OLED, the negative electrode of OLED is connected to the drain electrode of the first transistor T1, the source ground of the first transistor T1.
The circuit working process of embodiment five is identical with embodiment four, repeats no more herein.
Among the above embodiment one to five, T1, T2, these four transistors of T3, T4 can all be N raceway groove multi-crystal TFTs; Can all be P raceway groove multi-crystal TFT also, specifically see embodiment six to eight.
Embodiment six:
As shown in Figure 5, embodiment six is with the difference of embodiment three: T1, T2, these four transistors of T3, T4 are P raceway groove multi-crystal TFT, and this moment, second source was ground, the i.e. grounded drain of T3.
The course of work of circuit shown in the embodiment six is divided into three phases as shown in Figure 8 equally: pre-arcing stage, programming phases and glow phase.
The pre-arcing stage:
Grid sweep trace V
N-1Become low level by high level, V
NBe high level, T4 closes, because T3 opens, the voltage on first electrode of capacitor C s is discharged to zero by T3.
Programming phases:
Grid sweep trace V
N-1Become high level by low level, V
NBecome low level by high level, make T3 close, T4 opens.Data voltage V
DATAFor first electrode of memory capacitance Cs charges to V
TH_T2+ V
DATA(this moment V
TH_T2<0).
Glow phase:
Grid sweep trace V
N-1, V
NAll become high level, T3 and T4 end.The voltage of programming phases Cs first electrode is saved to frame scan next time.T1 provides electric current for OLED:
I=K(V
GS_T1-V
TH_T1)
2=K(V
DATA+V
TH_T2-V
DD-V
TH_T1)
2
Owing to close on T1 and the T2 position, and adopt identical technology, can think that both threshold voltages equate, i.e. V
TH_T2=V
TH_T1, but so the following formula abbreviation is:
I=K(V
DATA-V
DD)
2 (1)
From following formula as can be known, OLED electric current and TFT threshold voltage V
THIrrelevant, thereby the inhomogeneous brightness disproportionation problem that causes of compensation multi-crystal TFT panel threshold voltage, similarly, it drives the gate signal of control signal employing the superior and the subordinate pixel in the sequential, do not need extra grid sweep trace, simplified peripheral drive IC greatly, the complexity of pixel wiring also is lowered simultaneously.
Embodiment seven:
As shown in Figure 6, embodiment seven and embodiment six different be in: first power supply is the OLED anode voltage, that is, capacitor C
sSecond electrode link to each other with the anode of OLED.
The circuit working process of embodiment seven is identical with embodiment six, repeats no more herein.
Embodiment eight:
As shown in Figure 7, embodiment eight and embodiment six different be in: first power supply is ground, that is, capacitor C
sSecond electrode grounding.
The circuit working process of embodiment eight is identical with embodiment six, repeats no more herein.
T1, T2, T3 and T4 are P raceway groove multi-crystal TFT in the previous embodiment six to eight; The transistor of image element circuit can also be a complementary type in other embodiments, and for example embodiment nine.
Embodiment nine:
Among the embodiment nine shown in Fig. 9 a, circuit structure and embodiment six are roughly the same, and difference is: T1 and T2 are the N channel TFT, and T3 and T4 are the P channel TFT; At this moment, data signal line V
DATAAdopt the data voltage line of embodiment six described full P channel TFT image element circuits; And grid sweep trace, i.e. V
N-1And V
NAdopt the scanning gate signal of embodiment one described full N channel TFT image element circuit; And effective unblocked level of controlling the 3rd transistor T 3 and the 4th transistor T 4 is a high level.
The driving sequential of embodiment nine is shown in Fig. 9 b, the same with the analysis of aforementioned each embodiment, this circuit is the effectively uneven influence of threshold voltage in the compensation pixel circuit also, and control signal adopts the grid sweep trace between the superior and the subordinate's pixel, does not additionally increase sweep trace.
To sum up, the full N raceway groove multi-crystal TFT pixel-driving circuit of embodiment of the invention proposition and full P raceway groove multi-crystal TFT pixel-driving circuit and complementary raceway groove multi-crystal TFT pixel-driving circuit have following advantage:
(1) only needs four polycrystalline SiTFTs and an electric capacity; Compare with other image element circuit that can compensate threshold voltage with similar structures, circuit of the present invention not only can compensate the influence of the uneven counter plate brightness of TFT threshold voltage, and reducing under one to two transistorized prerequisite, can realize identical functions, therefore both can reduce the complexity and the cost of pixel, can improve aperture ratio of pixels again.
(2) embodiment of the invention can the compensation pixel circuit in the inhomogeneous brightness disproportionation problem that causes of threshold voltage.Wherein, only adopt one type TFT (N raceway groove or P raceway groove) in full N raceway groove or the full P channel TFT pixel-driving circuit, technological process is simpler, and cost is lower; Adopt the image element circuit of full N channel TFT and complementary TFT, its scanning gate signal low duration accounts for the overwhelming majority cycle, and dutycycle is very little, easier realization; Adopting its driving tube of image element circuit of P channel TFT and complementary TFT is P-channel device, and under the long-time bias effect, the P-channel device characteristic is more stable.
(3) the driving sequential of circuit adopts the scanning gate signal of the superior and the subordinate's pixel: the gate signal V in the circuit
N-1And V
NIn the entire frame scanning process, become high level (or low level) successively, and high level (or low level) stage non-overlapping copies.Therefore can utilize the V of the gate signal of previous stage pixel as the one's own profession pixel
N-1, one's own profession grid sweep trace V
NAlso be used as the V of next line pixel when providing the grid drive signal for the pixel corresponding levels at the corresponding levels
N-1This just is equivalent to every grade of pixel and only uses a scanning gate signal, and does not increase extra grid sweep trace; Compare with the circuit of several gate signals of needs, this circuit has been simplified peripheral grid driving circuit greatly, has also reduced the complexity of pixel wiring simultaneously.
The various embodiments described above are to describe according to the situation that has connected luminescent device, in a further embodiment, also can be that the image element circuit that will not comprise luminescent device is produced on the substrate earlier, reserve the connection terminal that is connected with luminescent device, and then the making luminescent device, and in assembling process, luminescent device is connected with image element circuit.
The foregoing description can be applicable to display device, as shown in figure 10, comprising:
Multi-strip scanning line with the first direction arrangement;
Scan drive circuit is used to produce sweep signal, and its output terminal is connected with the multi-strip scanning line respectively;
Many data lines with the second direction arrangement;
Data drive circuit is used to produce data-signal, and its output terminal is connected with many data lines respectively;
The described image element circuit of a plurality of as above embodiment, this image element circuit is disposed between the sweep trace and data line that intersects.
In this display device, its previous row grid sweep trace V
N-1Draw this horizontal scanning line, V in the driving process from the capable pixel previous row of N (N-1 is capable) pixel
N-1Become effective unblocked level (high level or low level are decided on the TFT of concrete use) earlier, upset again after effectively unblocked level continues for some time; One's own profession grid sweep trace V
NFor the capable pixel of N provides sweep signal, V in the driving process
NAt V
N-1Become the upset afterwards of anti-phase level by effective unblocked level and be effective unblocked level, and and V
N-1Effective unblocked level continue the identical time; One's own profession grid sweep trace V
NAnd as the previous row grid sweep trace of next line (N+1) pixel, wherein N is a natural number.Among a kind of embodiment, before the first row pixel, exist delegation's grid sweep trace to be used as the V of the first row pixel
N-1320 row pixels are for example arranged, need to exist 321 row grid sweep traces among the embodiment, wherein the 0th row grid sweep trace is then as the V of the 1st row pixel
N-1
Aforementioned each embodiment comprises image element circuit embodiment and display device embodiment, the grid sweep trace V of the superior and the subordinate's pixel that it adopts
NAnd V
N-1In other image element circuits embodiment or display device embodiment, can also be as V
NAnd V
N+1Etc. the grid sweep trace of form, V wherein
NBe the grid sweep trace of current line pixel, V
N+1Back delegation grid sweep trace for the current line pixel.This moment data-signal V
DATAThereby cooperating with scanning-line signal for pixel, the gating time that should postpone a sweep trace provides data voltage.
Above content be in conjunction with concrete embodiment to further describing that the present invention did, can not assert that concrete enforcement of the present invention is confined to these explanations.For the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to protection scope of the present invention.