CN102930818A - Organic light emitting diode pixel circuit - Google Patents
Organic light emitting diode pixel circuit Download PDFInfo
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Abstract
An organic light emitting diode pixel circuit comprises a driving node, a pixel driving unit, a display electroluminescence element and an electroluminescence compensating unit, wherein the pixel driving unit is coupled to a data line so as to receive data voltage, responds to the data voltage and provides driving voltage to the driving node; the display electroluminescence element is coupled to the driving node, responds to the driving voltage and emits the light; the level of the driving voltage is related to the aging factor voltage of the display electroluminescence element; the aging factor voltage corresponds to the using time of the electroluminescence element; the electroluminescence compensating unit is coupled to the driving node; an electroluminescence compensating circuit comprises a compensating electroluminescence element; the electroluminescence compensating unit drives the compensating electroluminescence element to emit the light according to the driving voltage; and aging decay compensation on the display electroluminescence element can be realized by the compensating electroluminescence element.
Description
Technical field
The present invention relates to a kind of Organic Light Emitting Diode (Organic Light Emitting Diode, OLED) image element circuit, and particularly a kind of can be for the OLED image element circuit that compensate because of the long-time brightness decline situation of using the OLED element that causes.
Background technology
In the now epoch that development in science and technology is maked rapid progress, Organic Light Emitting Diode (Organic Light Emitting Diode, OLED) technology is developed, and be used in many display application occasions, such as being TV, computer screen, mobile computer, mobile phone or personal digital assistant etc.In general, comprise a plurality of OLED image element circuits of arranging with matrix-style in the OLED display, each OLED image element circuit comprises OLED element and corresponding driving circuit.
In general, the OLED element in the OLED display and driving circuit thereof need long-time conducting, to carry out accordingly image display operations.Yet the activation conducting will be so that the OLED element produces the situation that critical conduction voltage rises and display brightness descends for a long time.Accordingly, how designing and can be effectively use the critical conduction voltage that occur to rise and the compensating circuit of the situation of display brightness decline for the OLED element because of long-time, be one of direction of constantly endeavouring of industry.
Summary of the invention
A kind of Organic Light Emitting Diode (Organic Light Emitting Diode is proposed according to the present invention, OLED) image element circuit, cause element and provide driving voltage to drive the pixel drive unit that the demonstration electricity causes element comprising the demonstration electricity as display operation, wherein the level of driving voltage is relevant to and shows that electricity causes the aging factor voltage of element.The OLED image element circuit that the present invention is correlated with comprises that also electricity causes compensating unit, cause element comprising the compensation electricity, and electricity causes compensating unit and drives the compensation electricity according to driving voltage to cause element luminous, causes element via the compensation electricity by this and comes showing that electricity causes element and carries out the degradation compensation.Accordingly, compared to traditional OLED display technology, the OLED image element circuit that the present invention is correlated with has and can cause element for demonstration electricity wherein and carry out the advantage that aging factor voltage compensates.
A kind of OLED image element circuit is proposed according to the present invention, comprising drive node, pixel drive unit, the demonstration electricity causes element and electricity causes compensating unit.Pixel drive unit is coupled to data line with receive data voltage, and provides driving voltage to driving node in response to data voltage.Show that electricity causes element and is coupled to the driving node, it is luminous in driving voltage to show that electricity causes element responds, and wherein the level of driving voltage is relevant to and shows that electricity causes the aging factor voltage of element, and aging factor voltage corresponds to the service time that electricity causes element.Electricity causes compensating unit and is coupled to the driving node, and electricity causes compensating circuit and comprises that the compensation electricity causes element, and electricity causes compensating unit and drives the compensation electricity according to driving voltage to cause element luminous, causes element via the compensation electricity by this and comes showing that electricity causes element and carries out the degradation compensation.
For there is better understanding above-mentioned and other aspect of the present invention, preferred embodiment cited below particularly, and cooperation accompanying drawing are described in detail below:
Description of drawings
Fig. 1 illustrates the calcspar of the display of the organic light-emitting diode pixel circuit of using the embodiment of the invention.
Fig. 2 illustrates the calcspar of organic light-emitting diode pixel circuit P (i, j).
Fig. 3 illustrates the circuit diagram according to the organic light-emitting diode pixel circuit of first embodiment of the invention.
Fig. 4 illustrates the circuit diagram according to the organic light-emitting diode pixel circuit of second embodiment of the invention.
Fig. 5 illustrates the circuit diagram according to the organic light-emitting diode pixel circuit of third embodiment of the invention.
Fig. 6 illustrates the circuit diagram according to the organic light-emitting diode pixel circuit of fourth embodiment of the invention.
Fig. 7 illustrates the coherent signal sequential chart into the organic light-emitting diode pixel circuit of Fig. 6.
[main element symbol description]
1: display
12: data driver
14: scanner driver
16: light emission controller
18: display panel
P (i, j), 10,20,30:OLED image element circuit
U1: pixel drive unit
U2: show that electricity causes element
U3: electricity causes compensating unit
M1-M3, M11-M13, M21-M25, M31-M38: transistor
C, C1-C3: electric capacity
Nc, Nc1, NC2, Nc1-Nc3: node
Nd: drive node
D1, D2:OLED element
Embodiment
The Organic Light Emitting Diode of the embodiment of the invention (Organic Light Emitting Diode, OLED) image element circuit comprises that the demonstration electricity as display operation causes element and provides driving voltage to drive the pixel drive unit that the demonstration electricity causes element, and wherein the level of driving voltage is relevant to and shows that electricity causes the aging factor voltage of element.The OLED image element circuit of the embodiment of the invention comprises that also electricity causes compensating unit, and is luminous in order to cause element according to driving voltage driving compensation electricity, causes element to showing that electricity causes element and carries out the degradation compensation via the compensation electricity by this.
Please refer to Fig. 1, it illustrates the calcspar of the display of the OLED image element circuit of using the embodiment of the invention.For instance, comprise data driver 12, scanner driver 14, light emission controller 16 and display panel 18 in the display 1.Display panel 18 comprises pel array, wherein for example has M * N OLED image element circuit P (1,1)-P (M, N), and M and N are the natural number greater than 1.Data driver 12, scanner driver 14 and light emission controller 16 are respectively in order to provide data-signal D (1)-D (N), sweep signal S (1)-S (M) and luminous signal E (1)-E (M) to display panel 18, to drive wherein each OLED image element circuit P (1,1)-P (M, N) carries out picture disply operation.
Because each OLED image element circuit P (1 in the display panel 18,1)-P (M, N) have identical in fact circuit structure and operation, next, only single the OLED image element circuit P (i, j) in the display panel 18 as example, come each OLED image element circuit P (1 in the display panel 18,1)-and circuit structure and the operation of P (M, N) be described further, and wherein i and j are respectively the natural number that is less than or equal to M and is less than or equal to N.
Please refer to Fig. 2, it illustrates the calcspar of the Organic Light Emitting Diode P (i, j) that is Fig. 1.OLED image element circuit P (i, j) comprises driving node Nd, pixel drive unit u1, shows that electricity causes element u2 and electricity causes compensating unit u3.Pixel drive unit u1 is coupled to data line with receive data voltage Vdata, and provides driving voltage Vdr to driving node Nd in response to data voltage Vdata.
Show that electricity causes element u2 and is coupled to driving node Nd, and luminous in response to driving voltage Vdr, showing that wherein electricity causes element u2 and has aging factor voltage Vaging, it for example determines the level of driving voltage Vdr accordingly.For instance, show that it is the OLED element that electricity causes element u2, and aging factor voltage Vaging for example is the critical conduction voltage of OLED element.The critical conduction voltage of OLED element can rise along with the long-time use of OLED element.
Electricity causes compensating unit u3 and is coupled to driving node Nd, and causes element comprising the compensation electricity.Electricity causes compensating unit u3 and drives this compensation electricity according to driving voltage Vdr to cause element luminous, causes element via the compensation electricity by this and comes showing that electricity causes element u2 and carries out the degradation compensation.Electricity causes compensating unit u3 and also for example comprises compensation drive unit, and to cause element luminous in order to determine driving the compensation electricity by the assistive drive electric current according to driving voltage Vdr for it.
Next for OLED image element circuit P (i, j) several operational instances is proposed, so that each subelement among the OLED image element circuit P (i, j) is described in further detail.
The first embodiment
Please refer to Fig. 3, it illustrates the detailed circuit diagram according to the organic light-emitting diode pixel circuit of first embodiment of the invention.In the OLED of present embodiment image element circuit 10, pixel drive unit u1 has the circuit structure of 2T1C, wherein for example comprises node Nc, transistor M1, M2 and capacitor C; Show that electricity causes element u2 and comprises OLED element D1; Electricity causes compensating unit u3 and comprises transistor M3 and OLED element D2, and wherein OLED element D2 causes element in order to realize the compensation electricity, and transistor M3 is in order to realize auxiliary drive unit.
Further, transistor M1-M2 for example is N-type metal-oxide semiconductor (MOS) (Metal Oxide Semiconductor, MOS) transistor.The grid of transistor M1 receives sweep signal S at the corresponding levels (i), and source electrode is coupled to node Nc, and drain electrode is coupled to data line with receive data voltage Vdata.The grid of transistor M2 is coupled to node Nc, and drain electrode receives noble potential reference voltage VDD, and source electrode is coupled to and drives node Nd.The first end of electric capacity is coupled to node Nc, and the second termination is received electronegative potential reference voltage VSS.The anode of OLED element D1 and negative terminal are coupled to respectively and drive node Nd and receive low level reference voltage VSS.
Transistor M1 is in response to sweep signal S at the corresponding levels (i) conducting in the scan period at the corresponding levels of correspondence, according to data voltage Vdata capacitor C is charged.Transistor M2 is conducting accordingly in response to the charging voltage at capacitor C two ends, and so that drive current driving OLED element D1 to be provided, the driving voltage Vdr that wherein drives on the node Nd for example satisfies equation (1):
Vdr＝Vth_D1 (1)
Wherein Vth_D1 is the critical conduction voltage of OLED element D1.
In an operational instances, the critical conduction voltage Vth_D1 of OLED element D1 can increase along with its service time and promote accordingly, so will cause driving voltage Vdr also to promote accordingly.For instance, the critical conduction voltage Vth_D1 of OLED element D1 can represent by equation (2):
Vth_D1＝Vth_D1_initial+ΔV (2)
Wherein Vth_D1_initial is the initial critical conduction voltage of OLED element D1 when not being subject to stress effect (Stress Effect), and Δ V is the amount of variability that is subject to the critical conduction voltage of the lower OLED element D1 of stress effect impact, length positive correlation service time of its numerical value and OLED element D1.
Transistor M3 also for example is nmos pass transistor, and wherein the grid of transistor M3 receives driving voltage Vdr, and source electrode is coupled to OLED element D2, and drain electrode receives high level reference voltage VDD.The anode of OLED element D2 and negative terminal are coupled to respectively the source electrode of transistor M3 and receive low level reference voltage VSS.In other words, the grid of transistor M3 and source electrode are coupled to respectively the anode of OLED element D1 and D2.
In an example, via the element length breadth ratio (Width/Length Ratio) of design transistor M3 and OLED element D1 and D2, can make accordingly the critical conduction voltage Vth_D2 of critical conduction voltage Vth_D1, OLED element D2 of OLED element D1 and the critical conduction voltage Vth_M3 of transistor M3 satisfy equation (3):
Vth_D1_Initial-Vth_D2≤Vth_M3 (3)
So, when OLED image element circuit 10 had not been subject to stress effect and affects, the critical conduction voltage that the cross-pressure at OLED element D1 two ends deducts OLED element D2 was less than or equal to the critical conduction voltage of transistor M3.In other words, at the use initial stage of OLED image element circuit 10, the cross-pressure at OLED element D1 two ends is not enough to turn-on transistor M3, so that OLED element D2 is not luminous for cut-off.Lift an operational instances, the critical conduction voltage Vth_M3 of transistor M3 is 2 volts (Volt, V), and the critical conduction voltage of VOLED element D1 and D2 equals respectively 2V and 3V.
And as OLED image element circuit 10 use a period of time Tu (for example being 10000 hours), OLED element D1 is because of long-time conducting generation brightness decay, simultaneously the critical conduction voltage Vth_D1 of OLED element D1 also is subject to the impact of stress effect and rises accordingly, its also the related driving voltage Vdr that makes rise.The driving voltage Vdr (Tu) of this moment can represent by equation (4):
Vdr(Tu)＝Vth_D1(Tu)＝Vth_D1_initial+ΔV(Tu) (4)
Wherein, Δ V (Tu) is after the use of elapsed time Tu, critical conduction voltage Vth_D1 deducts the amount of variability of the initial critical conduction voltage Vth_D1_initial of OLED element D1, and driving voltage Vdr this moment (Tu) for example satisfies equation (5):
Vth_D1(Tu)-Vth_D2＝Vth_D1_initial+ΔV(Tu)-Vth_D2＞Vth_M3 (5)
In other words, because OLED element D1 stress effect generating device is aging, so that the impedance of OLED element D1 rises, and then the electric current of the OLED element D1 that causes flowing through descends, and so that the display brightness of OLED image element circuit 10 descend.This moment OLED element D1 critical conduction voltage Vth_D1 also the stress effect impact and produce the amount of variability of Δ V (Tu), and then so that the difference of critical conduction voltage Vth_D1 and Vth_D2 be higher than the critical conduction voltage Vth_M35 of transistor M3 and make transistor M3 conducting, and so that by way of compensation electricity to cause the OLED element D2 of element luminous.Accordingly, the OLED image element circuit 10 of present embodiment can come via the OLED element D2 (electricity causes element by way of compensation) of conducting to compensate for the brightness decay of OLED element D1 (as showing that electricity causes element u2).
In addition, critical conduction voltage Vth_D1 will increase accordingly along with the increase of stress influence time, so that the difference of critical conduction voltage Vth_D1 and Vth_D2 increases accordingly, driving transistors M3 provides larger electric current to come OLED element D2 is driven by this.In other words, electricity causes the brightness meeting and display operation time and aging factor voltage of the OLED element D2 of element by way of compensation, namely is the critical conduction voltage Vth D1 of OLED element D1, is directly proportional.
The second embodiment
Please refer to Fig. 4, it illustrates the circuit diagram according to the organic light-emitting diode pixel circuit of second embodiment of the invention.OLED image element circuit 10 differences of the OLED image element circuit 20 of present embodiment and the first embodiment are that transistor wherein is to adopt the LTPS processing procedure, so all be P type MOS transistor.
Cause compensating unit u3 with electricity, the grid of transistor M13 wherein receives electronegative potential reference voltage VSS, and drain electrode is coupled to the anode of OLED element D2; And the negative terminal of OLED element D2 is received the end points that receives low level reference voltage VSS, and the source electrode of transistor M13 is coupled to and drives node Nd to receive driving voltage Vdr.So, when OLED image element circuit 20 was not subject to stress effect and affects, the positive terminal voltage of OLED element D1 caused the power supply supply of compensating circuit u3 as electricity.At this moment, because the grounded-grid of transistor M13, so the gate-to-source cross-pressure VGS_M13 of transistor M13 is negative value, and makes transistor M13 conducting.For instance, the gate-to-source cross-pressure VGS_M13 of transistor M13 satisfies equation (6) at this moment:
VGS_M13＝VSS-Vth_D1_initial＜0 (6)
And after OLED image element circuit 20 showed a period of time Tu, the cross-pressure between OLED element D1 anode and negative terminal rose because of problem of aging, so that the anode level of OLED element D1 also rises accordingly.So, with so that the level of the gate-to-source cross-pressure VGS M13 of transistor M13 becomes more negative, the current boost of transistor M13 so that flow through, and then so that by way of compensation electricity to cause the OLED element D2 luminosity of element brighter, by this to as showing that the brightness decay that electricity causes the OLED element D1 of element u2 compensates.
The 3rd embodiment
Please refer to Fig. 5, it illustrates the circuit diagram according to the organic light-emitting diode pixel circuit of third embodiment of the invention.The OLED image element circuit 30 of present embodiment is that from OLED image element circuit 10 differences of the first embodiment pixel drive unit u1 wherein has different circuit structures.Furthermore, the pixel drive unit u1 of present embodiment comprises node Nc1, Nc2, transistor M21-M25 and capacitor C, and wherein transistor M21-M25 for example is nmos pass transistor.
The grid of transistor M21 receives sweep signal S at the corresponding levels (i), and drain electrode is coupled to data line with receive data voltage Vdata, and source electrode is coupled to node Nc1.The grid of transistor M22 receives sweep signal S at the corresponding levels (i), and drain electrode is coupled to node Nc1, and source electrode is coupled to node Nc2.The grid of transistor M23 is coupled to node Nc2, and drain electrode is coupled to node Nc1, and source electrode is coupled to and drives node Nd.The grid of transistor M24 is coupled to node Nc2, and drain electrode receives noble potential reference voltage VDD, and source electrode is coupled to and drives node Nd.The first end of capacitor C and the second end are coupled to respectively node Nc2 and receive clock signal CK.
For instance, transistor M22 conducting is with grid and the drain electrode of short circuit connection transistor M23, so that transistor M23 is biased for diode connects configuration, is coupled between transistor M21 and the OLED element D1.Transistor M21, M23 and OLED element D1 more form bleeder circuit, come data voltage Vdata is carried out dividing potential drop, so that the driving voltage Vdr on the driving node Nd is essentially the dividing potential drop composition of data voltage Vdata.For instance, driving voltage Vdr and data voltage Vdata satisfy equation (7):
Wherein Z_D1, Z_M21 and M_M23 are respectively the equivalent resistance of OLED element D1, transistor M21 and M23.
So, D1 is subject to the impact of stress effect when the OLED element, and when having accordingly higher critical conduction voltage Vth_D1, resistance Z _ D1 of OLED element D1 also rises accordingly; So, according to equation (7) as can be known, driving voltage Vdr has a voltage rising amount of variability accordingly because of the rising of resistance Z _ D1.More than comprehensive, the critical conduction voltage Vth_D1 that pixel drive unit u1 can rise in response to OLED element D1 provide higher driving voltage Vdr accordingly, by this compensation is made in the variation of the critical conduction voltage Vth_D1 of OLED element D1.
The OLED image element circuit 30 of present embodiment also comprises accordingly that electricity causes compensating unit u3, and it is for example realized by transistor M25 and OLED element D2.It is luminous accordingly in response to driving voltage Vdr that electricity causes compensating unit u3, by this OLED element D1 compensated with the brightness decay that produces service time.The electricity of present embodiment causes compensating unit u3 operating principle and the electricity of the first embodiment, and to cause compensating unit u3 identical, seldom gives unnecessary details at this.
In addition, in the OLED of present embodiment image element circuit 30, more use second of capacitor C and bring in receive clock signal CK.In an operational instances, when transistor M21 and M22 in response to sweep signal S at the corresponding levels (i) in scan period at the corresponding levels during conducting, clock signal C K for example corresponds to low level reference voltage VSS; So data voltage Vdata writes to node Nc2 via transistor M21 and M22, so that node Nc2 corresponds to operating voltage Vdata ', and the first end of capacitor C is compared to the second end store storage voltage Vdata '-VSS accordingly.
After finishing OLED element D1 display operation, the OLED image element circuit 30 of present embodiment then will provide negative potential voltage to come transistor M24 is driven, and slow down by this transistor M24 because of the impact of the stress effect of long-time conducting.Further, behind the display operation of finishing OLED element D1, this moment, clock signal C K was that electronegative potential reference voltage VSS switches to a negative potential reference voltage Vmin; So, the level of the first end of capacitor C will be pulled low to because of the coupling effect at capacitor C two ends operating voltage Vdata '+Vmin.For instance, the absolute value of operating voltage Vdata ' is in fact less than the absolute value of negative potential reference voltage Vmin, so that operating voltage Vdata '+Vmin corresponds in fact the negative potential that is lower than electronegative potential reference voltage VSS.So, after scan period at the corresponding levels, can provide accordingly negative potential voltage to come transistor M24 is driven on the first end of capacitor C, slow down by this transistor M24 because of the impact of the stress effect of long-time conducting.
The 4th embodiment
Please be simultaneously with reference to Fig. 6 and Fig. 7, Fig. 6 illustrates the circuit diagram according to the organic light-emitting diode pixel circuit of fourth embodiment of the invention; Fig. 7 illustrates the circuit operation sequential into Fig. 6, be divided into Tp between precharge phase, pre-during writing Tr, during writing Tw and show during Te.
The OLED image element circuit 40 of present embodiment is that from OLED image element circuit 10 differences of the first embodiment pixel drive unit u1 wherein has different circuit structures.Furthermore, the pixel drive unit u1 of present embodiment comprises node Nc1, Nc2, transistor M31-M37 and capacitor C 1-C3, comprises transistor M38 and OLED element D2 and electricity causes compensating unit u3; Wherein transistor M31-M38 for example is nmos pass transistor.
The grid of transistor M32, M33 and M36 receives previous stage sweep signal S (i-1), source electrode receives respectively electronegative potential reference voltage VSS, is coupled to node Nc2 and is coupled to driving node Nd, and the drain electrode of transistor M32 is coupled to node Nc1, and the drain electrode of transistor M33 and M36 is coupled to node Nc3.Transistor M32, M33 and M36 be in response to previous stage sweep signal S (i-1) conducting among Tp and the pre-during writing Tr between precharge phase, and end in other operating periods.
The grid of transistor M31 and M37 receives sweep signal S at the corresponding levels (i), drain electrode receive data voltage Vdata, and source electrode is coupled to respectively node Nc1 and drives node Nd.Transistor M31 and M37 be in response to sweep signal S at the corresponding levels (i) conducting in during writing Tw, and end in other operating periods.
The grid of transistor M34 receives luminous signal E at the corresponding levels (i), and drain electrode receives noble potential reference voltage VDD, and source electrode is coupled to node Nc3.Transistor M34 in response to luminous signal E at the corresponding levels (i) between precharge phase Tp and show during conducting among the Te, and in other operating periods, end.
The grid of transistor M35 is coupled to node Nc2, and drain electrode is coupled to node Nc3, and source electrode is coupled to and shows that electricity causes element u2.The two ends of capacitor C 1 are coupled to respectively node Nc1 and receive electronegative potential reference voltage VSS; The first end C2_E1 of capacitor C 2 and the second end C2E2 are coupled to respectively node Nc2 and Nc1; The first end C3_E1 of capacitor C 3 and the second end C3_E2 are coupled to respectively and drive node Nd and receive electronegative potential reference voltage VSS.
The grid of transistor M38 receives driving voltage Vdr, and source electrode is coupled to OLED element D2, and drain electrode receives high level reference voltage VDD.The anode of OLED element D2 and negative terminal are coupled to respectively the source electrode of transistor M38 and receive low level reference voltage VSS.
Referring again to Fig. 7.Among the Tp, previous stage sweep signal S (i-1) and luminous signal E at the corresponding levels (i) are activation between precharge phase, and sweep signal S at the corresponding levels (i) is disabled.Accordingly, transistor M32, M33, M34, M35 and M36 are that conducting and transistor M31 and M37 are cut-off, so that the first end C2_E1 of capacitor C 2 has pre-charge voltage Vpre compared to the second end C2_E2, and the first end C3_E1 of capacitor C 3 also has pre-charge voltage Vpre compared to the second end C3_E2.For instance, pre-charge voltage Vpre for example satisfies equation (8):
Vpre＝VDD-VSS＝VDD (8)
In pre-during writing Tr, previous stage sweep signal S (i-1) is activation, and luminous signal E at the corresponding levels (i) and sweep signal S at the corresponding levels (i) are disabled.Accordingly, transistor M32, M33, M35 and M36 are that conducting and transistor M31, M34 and M37 are cut-off, and wherein the transistor M33 short circuit of conducting connects grid and the drain electrode of transistor M35, make that transistor M35 is biased to be diode arrangement.So, so that the path of the voltage at capacitor C 2 two ends through comprising transistor M35 and OLED element D1 is discharged to critical voltage Vth1, and the path of the voltage at capacitor C 3 two ends through comprising transistor M35, M36 and OLED element D1 is discharged to critical voltage Vth2, and wherein critical voltage Vth1 and Vth2 satisfy equation (9):
Vth1＝Vth2＝Vth_M35+Vth_D1 (9)
Wherein Vth_M35 and Vth_D1 are respectively the critical conduction voltage of transistor M35 and OLED element D1.In other words, the critical conduction voltage of capacitor C 2 and C3 record transistor M35 and OLED element D1 and.
In data during writing Tw, sweep signal S at the corresponding levels (i) is activation, and previous stage sweep signal S (i-1) and luminous signal E at the corresponding levels (i) are disabled.Transistor M31 and M37 are that conducting and transistor M32-M36 are cut-off accordingly, so that capacitor C 1 two ends are charged to data voltage Vdata, capacitor C 2 two ends continue storage critical voltage Vth1, and the voltage Vth2 ' at capacitor C 3 two ends satisfies following equation (10) in response to the conducting of transistor M37:
Vth2′＝Vth_M35+Vth_D1-Vdischarge (10)
Wherein sparking voltage Vdischarge is relevant with the level of data voltage Vdata.Further it, transistor M37 has high conduction impedance Ron, and the high conduction impedance Ron of the velocity of discharge of sparking voltage Vdischarge when depending on transistor M37 conducting; So, so that under the data voltage Vdata of varying level, in various degree compensation is carried out in the decay of OLED element D1.In other words, transistor M37 drives node Nd in order in data during writing Tw data voltage Vdata provided, make and drive the level that the driving voltage Vdr on the node Nd can follow data voltage Vdata, by this when data voltage Vdata corresponds to different voltage levels, via providing data voltage Vdata to make in various degree compensation to driving element characteristic decline that node Nd comes the critical conduction voltage to OLED element D1 to rise.
Among the Te, at the corresponding levels and previous stage sweep signal S (i) is disabled with S (i-1) during driving, and luminous signal E at the corresponding levels (i) is activation.Transistor M34 and M35 are that conducting and transistor M31-M33 and M36-M37 are cut-off accordingly, with with the first end C2E1 of capacitor C 2 cross-pressure to the second end C1E2 of capacitor C 1, namely be critical voltage Vth1 and data voltage Vdata and, put on the grid and source electrode and OLED element D2 of transistor M35.So, cooperate equation (8) as can be known, wherein the grid of transistor M35 and source voltage Vgs_M35 satisfy equation (11):
Vgs_M35＝Vth1+Vdata-Vth_D1＝Vth_M35+Vth_D1+Vdata-Vth_D1
＝Vth_M35+Vdata (11)
Because the grid-source voltage Vgs_M35 of transistor M35 can equation (10) expression, the source current I of the transistor M35 that so flows through namely is the drive current of OLED cells D 1 of flowing through, and satisfies equation (12):
I＝k(Vgs_M35-Vth_M35)
2＝k[(Vth_M35+Vdata)-Vth_M35]
2
＝k[Vdata]
2 (12)
By equation (11) as can be known, the current equation by OLED element D1 can not be subject to the impact of the critical conduction voltage Vth_D1 of the critical conduction voltage Vth_M35 of transistor M35 and OLED element D1.Accordingly, even if critical conduction voltage Vth_M35 and the Vth_D1 of transistor M35 and OLED element D1 rise because of stress effect, the size of drive current I still is not subjected to its impact, and only has with data voltage Vdata relevant.In other words, the OLED image element circuit 40 of present embodiment can be accordingly compensates for wherein driving transistors M35 and the critical conduction voltage amount of variability of OLED element D1.
In addition, the OLED image element circuit 40 of present embodiment also has electricity and causes compensating unit u3, comes for showing that the electric brightness decay that causes element u2 compensates.In addition, in the OLED of present embodiment image element circuit 40, the driving voltage Vdr that drives on the node Nd is relevant with critical conduction voltage Vth_M35 and the Vth_D1 of transistor M35 and OLED element D1; When the impact of the critical conduction voltage Vth_M35 of transistor M35 and OLED element D1 and Vth_D1 stress effect and when becoming higher, driving voltage Vdr corresponds to higher voltage level.So, the transistor M38 that causes among the compensating unit u3 of electricity can in response to the driving voltage Vdr with higher voltage level (please refer to equation (9)), provide larger drive current to come OLED element D2 is driven accordingly.In other words, OLED element D2 can adjust brightness accordingly according to the critical conduction voltage Vth_M35 of OLED element D1 and transistor M35 and the variation amplitude of Vth_D1; When the amount of variability of critical conduction voltage Vth_M35 and Vth_D1 was larger, the level of driving voltage Vdr was higher, and the electric current of driving OLED element D2 is just larger.
Comprise in the OLED image element circuit of the above embodiment of the present invention that the demonstration electricity as display operation causes element and provides driving voltage to drive the pixel drive unit that the demonstration electricity causes element, wherein the level of driving voltage is relevant to and shows that electricity causes the aging factor voltage of element.The OLED image element circuit of the above embodiment of the present invention more uses and comprises that the electric electricity that causes element of compensation causes compensating unit, and is luminous to cause element according to driving voltage driving compensation electricity, causes element via the compensation electricity by this and comes showing that electricity causes element and carries out the degradation compensation.Accordingly, compared to traditional OLED display technology, the OLED image element circuit of the above embodiment of the present invention has and can cause element for demonstration electricity wherein and carry out the advantage that aging factor voltage compensates.
In sum, although the present invention with preferred embodiment openly as above, so it is not to limit the present invention.Those skilled in the art without departing from the spirit and scope of the present invention, when being used for a variety of modifications and variations.Therefore, protection scope of the present invention is as the criterion when looking the appended claims person of defining.
Claims (11)
1. Organic Light Emitting Diode OLED image element circuit comprises:
One drives node;
One pixel drive unit is coupled to a data line receiving a data voltage, and provides a driving voltage to drive node to this in response to this data voltage;
One shows that electricity causes element, be coupled to this driving node, it is luminous in this driving voltage that this demonstration electricity causes element responds, and wherein the level of this driving voltage is relevant to the aging factor voltage that this demonstration electricity causes element, and this aging factor voltage corresponds to the service time that this demonstration electricity causes element; And
One electricity causes compensating unit, be coupled to this driving node, this electricity causes compensating circuit and comprises that a compensation electricity causes element, and this electricity causes compensating unit and drives this compensation electricity according to this driving voltage to cause element luminous, causes element via this compensation electricity by this and comes that this demonstration electricity is caused element and carry out degradation and compensate.
2. OLED image element circuit as claimed in claim 1, wherein this electricity causes compensating unit and comprises:
One auxiliary drive unit is coupled to this driving node, and this auxiliary drive unit determines an assistive drive electric current according to this driving voltage, and driving according to this this compensation electricity, to cause element luminous.
3. OLED image element circuit as claimed in claim 2, wherein this auxiliary drive unit comprises:
One transistor, grid are coupled to this driving node to receive this driving voltage, and drain electrode receives a noble potential reference voltage, and source electrode is coupled to this compensation electricity and causes element.
4. OLED pixel cell as claimed in claim 3, wherein this compensation electricity causes element and comprises:
One OLED, anode are coupled to this transistorized source electrode, and negative terminal receives an electronegative potential reference voltage.
5. OLED pixel cell as claimed in claim 2, wherein this auxiliary drive unit comprises:
One transistor, source electrode are coupled to this driving node to receive this driving voltage, and drain electrode is coupled to this compensation electricity and causes element, and grid receives an electronegative potential reference voltage.
6. OLED pixel cell as claimed in claim 5, wherein this compensation electricity causes element and comprises:
One OLED, anode are coupled to this transistorized drain electrode, and negative terminal receives this electronegative potential reference voltage.
7. OLED pixel cell as claimed in claim 1, wherein this demonstration electricity causes element and comprises:
One OLED, anode are coupled to this driving node and receive this driving voltage, and negative terminal receives an electronegative potential reference voltage.
8. OLED pixel cell as claimed in claim 1, wherein this pixel drive unit comprises:
One node;
One the first transistor, grid receive a sweep signal at the corresponding levels, and source electrode is coupled to this node, and drain electrode is coupled to this data line to receive this data voltage;
One transistor seconds, grid are coupled to this node, and drain electrode receives a noble potential reference voltage, and source electrode is coupled to this driving node; And
One electric capacity, first end are coupled to this node, and the second termination is received an electronegative potential reference voltage.
9. OLED pixel cell as claimed in claim 1, wherein this pixel drive unit comprises:
One node;
One the first transistor, grid receive a sweep signal at the corresponding levels, and drain electrode is coupled to this node, and source electrode is coupled to this data line to receive this data voltage;
One transistor seconds, grid are coupled to this node, and drain electrode is coupled to this driving node, and source electrode receives a noble potential reference voltage; And
One electric capacity, first end are coupled to this node, and the second termination is received this noble potential reference voltage.
10. OLED pixel cell as claimed in claim 1, wherein this pixel drive unit comprises:
One first node and a Section Point;
One the first transistor, grid receive a sweep signal at the corresponding levels, and drain electrode is coupled to this data line to receive this data voltage, and source electrode is coupled to this first node;
One transistor seconds, grid receive this corresponding levels sweep signal, and drain electrode is coupled to this first node, and source electrode is coupled to this Section Point;
One the 3rd transistor, grid is coupled to this Section Point, and drain electrode is coupled to this first node, and source electrode is coupled to this driving node;
One the 4th transistor, grid is coupled to this Section Point, and drain electrode receives a noble potential reference voltage, and source electrode is coupled to this driving node; And
One electric capacity, first end and the second end are coupled to respectively this Section Point and receive a clock signal.
11. OLED pixel cell as claimed in claim 1, wherein this pixel drive unit comprises:
One first node, a Section Point and one the 3rd node;
One the first transistor, grid receive a previous stage sweep signal, and drain electrode is coupled to this first node, and source electrode receives an electronegative potential reference voltage;
One transistor seconds, grid receive this previous stage sweep signal, and drain electrode is coupled to the 3rd node, and source electrode is coupled to this Section Point;
One the 3rd transistor, grid receive this previous stage sweep signal, and drain electrode is coupled to the 3rd node, and source electrode is coupled to this driving node;
One the 4th transistor, grid receive a sweep signal at the corresponding levels, and drain electrode receives this data voltage, and source electrode is coupled to this first node;
One the 5th transistor, grid receive this corresponding levels sweep signal, and drain electrode receives this data voltage, and source electrode is coupled to this driving node;
One the 6th transistor, grid receive a luminous signal at the corresponding levels, and drain electrode receives this noble potential reference voltage, and source electrode is coupled to the 3rd node;
One the 7th transistor, grid is coupled to this Section Point, and drain electrode is coupled to the 3rd node, and source electrode is coupled to and shows that electricity causes element u2;
One first electric capacity, two ends are coupled to respectively this first node and receive this electronegative potential reference voltage;
One second electric capacity, two ends be coupled to respectively this first and this Section Point; And
One the 3rd electric capacity, two ends are coupled to respectively this driving node and receive this electronegative potential reference voltage.
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| CN2011102265573A CN102930818A (en) | 2011-08-08 | 2011-08-08 | Organic light emitting diode pixel circuit |
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| CN2011102265573A CN102930818A (en) | 2011-08-08 | 2011-08-08 | Organic light emitting diode pixel circuit |
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| CN2013103111444A Division CN103400545A (en) | 2011-08-08 | 2011-08-08 | Pixel circuit |
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| CN102930818A true CN102930818A (en) | 2013-02-13 |
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| WO2023000989A1 (en) * | 2021-07-20 | 2023-01-26 | 京东方科技集团股份有限公司 | Display substrate and brightness compensation method thereof, and display apparatus |
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Application publication date: 20130213 |