CN104050926B - A kind of OLED data drive circuit, based on the active TFT oled panel of this circuit and driving method thereof - Google Patents
A kind of OLED data drive circuit, based on the active TFT oled panel of this circuit and driving method thereof Download PDFInfo
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Abstract
The invention discloses a kind of OLED data drive circuit, active TFT based on this circuit? oled panel and driving method thereof, this current driving circuit is formed by with lower part: current feed-forward part; Current feedback part; Comparison amplifier; Dynamic compensation part; Bias supply; This data drive circuit can fast speed, accurately give current mode TFT? OLED pixel programming.Should based on the active TFT of data drive circuit? the raster data model line of oled panel is the twice of general panels, and the pixel in a gate line direction is divided into different two groups according to the parity of place data line, the gated sweep time of two groups of pixels in same line direction is the half of gated sweep time on general panels respectively, and the pixel in same line direction is sequentially opened in these two groups of controlling grid scan line complementations.
Description
Technical field
The present invention relates to a kind of OLED data drive circuit, based on the active TFTOLED panel of this circuit and driving method thereof.
Background technology
Organic light emitting diode display (organiclightemittingdiode, OLED) have the advantages such as active illuminating, high brightness, high-contrast, it is interpreted as the display technique of future generation into alternative liquid crystal display (LCD) widely.Different from the LCD technology of voltage driven type, OLED is a kind of current mode light emitting semiconductor device based on organic material, and its injection by charge carrier and compound produce luminescence phenomenon, and luminous intensity is directly proportional to the electric current of injection.The driving method of OLED is divided into passive (PMOLED) and active type (AMOLED).Wherein, thin film transistor (TFT) (TFT) is both increased in each pixel of OLED, for the programming of OLED and the AMOLED technology of driving owing to can overcome that PMOLED resolution is low, power consumption is large and the shortcoming such as the life-span is short, be thus more hopeful for the high-resolution display occasion of large scale.
According to the difference of image element circuit programming mode, AMOLED is divided into again current programmed type (currentprogram, CP) and voltage-programming type (voltageprogram, VP).Many results of study show: current programmed type is more accurate than voltage-programming type.Voltage-programming type image element circuit then programming precision, temperature compensation and to OLED compensate etc. in existing defects.And current-programmed pixel-driving circuit not only can compensate the performance degradation of TFT, the drift of such as threshold voltage, carrier mobility are uneven, can also degenerate by the display performance that brings of compensates or OLED aging (cut-in voltage of such as OLED rises).Therefore, current programmed type OLED pixel structure more likely adopt by industrialized production.
But also there is a serious shortcoming in current-programmed pixel-driving circuit, namely Time Created, (settlingtime) was long.When especially carrying out low gray scale, the programming of little drive current to pixel, often need the programming time reaching more than hundreds of microsecond just can set up stable pixel current.Due to long Time Created, under high frame rate or high-resolution situation, OLED pixel does not have time enough to carry out the switching of current status, and the gray shade scale causing oled panel to show reduces by this.Such as, even if adopt the TFT technology of the higher advanced person of mobility, oxide TFT (IGZOTFT), multi-crystal TFT etc., the long problem of current-programmed pixel-driving circuit programming time still exists.Although current programmed type image element circuit compensation performance is superior, because the long application in large scale high resolving power occasion Time Created is subject to great restriction.
It has been generally acknowledged that, the method accelerating the programming of current pixel drive circuits has following: (1) reduces stray capacitance; (2) data current is increased; (3) program voltage and data line starting potential V is reduced
0difference, adopt mixed type type of drive.But the value of stray capacitance is determined by technique, especially on panel, the source of stray capacitance is complicated, will reduce stray capacitance greatly and be not easy.Increase data current and then can bring the problem that power consumption is too large.The mode of combination drive makes the complexity of driving circuit greatly increase.Therefore, practical, fast current mode data drive circuit be the key issue realizing AMOLED high image quality, maximization.
Summary of the invention
The invention provides a kind of OLED data drive circuit, based on the active TFTOLED panel of this circuit and driving method thereof, its object is to, a kind of data drive circuit is provided, can fast speed, give current mode TFTOLED pixel programming accurately.
A kind of OLED data drive circuit, comprises current feed-forward module, current feedback module, comparison amplifier and bias supply;
Wherein, the outside input current source Idata of described data drive circuit is all connected with the input end of described current feed-forward module with the output terminal of described current feedback module, the electric current of the control end of described current feed-forward module is the outside input current Idata of data drive circuit and the electric current sum of current feedback module output, and the output current of described current feed-forward module is used for OLED pixel cell and drives;
The first input end of described comparison amplifier is connected to the input end of described current feed-forward module, and the second input end connects reference voltage source V
r, output terminal is connected with the control end of described current feed-forward module and the input end of described current feedback module;
The input end of described current feedback module is connected with the output terminal of described comparison amplifier, and output terminal output feedack electric current is to the first input end of described comparer;
Described bias supply output reference voltage, to comparison amplifier, exports reference current to described current feed-forward module and current feedback module.
Described bias supply comprises the first current source IB
1, the second current source IB
2and reference voltage source V
r, described first current source I
b1with the second current source I
b2be respectively current feed-forward module and current feedback module provides electric current, described reference voltage source V
rfor described comparison amplifier is powered;
Described first current source IB
1with the second current source IB
2the equal ground connection of negative pole, described reference voltage source V
rfor described comparison amplifier is powered.
There is provided bias current to current feed-forward module, current feedback module and comparison amplifier, make the transistor of each circuit part above have suitable bias state.
Described current feed-forward module comprises the first transistor M1, and described the first transistor M1 is N-type metal-oxide-semiconductor;
First node n1 is the first input end of described comparison amplifier, and Section Point n2 is the output terminal of described comparison amplifier, and the 3rd node n3 is described first current source I
b1positive pole;
The drain coupled of described the first transistor is to first node n1, and grid is coupled to Section Point n2, and source class is coupled to the 3rd node n3.
Generated data electric current I data and current feedback portion of electrical current, and by add and electric current export and be provided to OLED pixel cell.
Described current feedback module comprises transistor seconds M2, third transistor M3 and the 4th transistor M4, and described transistor seconds M2 is N-type metal-oxide-semiconductor, and third transistor M3 and the 4th transistor M4 is P type metal-oxide-semiconductor;
Described 4th node n4 is described second current source I
b2positive pole, described 5th node n5 is the drain electrode of the 4th transistor;
The source class of described third transistor M3 and the 4th transistor M4 is all coupled to the first voltage source Vcc, the grid of described third transistor M3 and the 4th transistor M4 is all coupled to the 5th node n5, the drain electrode of described 4th transistor M4 is all coupled in the 5th node n5, the drain electrode of described third transistor is connected with the drain electrode of described the first transistor M1, and is coupled in first node n1; The drain coupled of described transistor seconds M2 is to the 5th node n5, and grid is connected with the grid of described the first transistor M1 and is coupled in Section Point n2, and source-coupled is in the 4th node n4.
Dynamically regulate the charge/discharge current of data line load capacitance on TFT panel according to OLED pixel voltage, reach the programming time reducing OLED pixel, the object accelerating programming process.
The positive input terminal of described comparison amplifier is connected with first node n1, negative input end and reference voltage source V
rbe connected, output terminal is connected with Section Point n2.
Relatively data line voltage and reference voltage, and regulate current feed-forward and feedback module according to the result compared.
Described comparison amplifier also comprises the 5th transistor M5, the 6th transistor M6, the 7th transistor M7, the 8th transistor M8 and the 3rd current source IB
3, described 5th transistor M5 and the 6th transistor M6 is P type metal-oxide-semiconductor, and the 7th transistor M7 and the 8th transistor M8 is N-type metal-oxide-semiconductor;
6th node n6 is described 3rd current source I
b3negative pole, the 7th node n7 is the drain electrode of the 5th transistor;
Described 3rd current source IB
3positive pole be coupled to the first voltage source Vcc, negative couplings is to the 6th node n6;
The source class of described 5th transistor M5 and the 6th transistor M6 is all coupled to the 6th node n6, and the grid of described 5th transistor M5 is coupled with first node n1, and the drain coupled of described 5th transistor M5 is in the 7th node n7; The grid of described 6th transistor M6 and described reference voltage source V
rbe connected, the drain coupled of described 6th transistor M6 is to Section Point n2;
The equal ground connection of source class of described 7th transistor M7 and the 8th transistor M8, the grid of described 7th transistor M7 and the 8th transistor M8 is all coupled in the 7th node n2, and the drain coupled of described 8th transistor M8 is in Section Point n2.
Also comprise dynamic compensation module, the output terminal of described dynamic compensation module is connected with the input end of described current feed-forward part and the output terminal of described comparison amplifier, and described bias supply is described dynamic compensation module for power supply.
Described dynamic compensation module comprises the 9th transistor Mp and building-out capacitor Cp; Described 9th transistor MP is N-type metal-oxide-semiconductor;
Described 8th node n8 is the source class of the 9th transistor;
The grid of described 9th transistor Mp is coupled to Section Point n2, and drain coupled is to first node n1, and source-coupled is to the 8th node n8;
The first end of described building-out capacitor Cp is coupled to the 8th node n8, the second end ground connection.
Dynamically adjust the depth of feedback of building-out capacitor, when program current is larger, implements depth compensation, suppress the voltage oscillation on the output node of described comparison amplifier, thus reduce the ripple current of described current feed-forward module and current feedback module; When program current is less, implements shallow compensation and even close compensating module, improve the response speed of described comparison amplifier, thus strengthen the effect of described current feed-forward and the programming of feedback module acceleration small area analysis.
A kind of active TFTOLED panel based on OLED data drive circuit, OLED data drive circuit described in employing, include N*M OLED pixel cell, wherein N is the pixel quantity of active TFTOLED panel array column direction, M is the pixel quantity of active TFTOLED panel array line direction, N and M is the integer being more than or equal to 1;
Described active TFTOLED panel array includes 2*N bar raster data model line V
g 1~ V
g 2N, M bar data drive wire V
d 1~ V
d m;
By two raster data model line V on described active TFTOLED panel array
g 2k-1, V
g 2kdrive a line TFTOLED pixel, and as one group of raster data model line, wherein k is integer, and 1≤k≤N;
Often organize connected pixel on raster data model line and be divided into two classes according to the parity of place alignment serial number, comprise odd column pixel and even column pixels; The raster data model end of odd column pixel is connected to raster data model line V
g 2k-1, data-driven end is connected to the 3rd node n3 of described OLED data drive circuit; The raster data model end of even column pixels is connected to raster data model line V
g 2k, data-driven end is connected to the 4th node n4 of described OLED data drive circuit.
A kind of driving method of the active TFTOLED panel based on OLED data drive circuit, the active TFTOLED panel based on OLED data drive circuit described in employing, often organize connected pixel on raster data model line and be divided into two classes according to the parity of place alignment, comprise odd column pixel and even column pixels, odd column pixel and even column pixels complementation are programmed: when in odd even ordered series of numbers pixel, when wherein a row pixel is in data-driven programming state, another row pixel is for keeping current state.
Namely when odd column pixel is in data-driven programming state, even column pixels remains original data mode, otherwise when even column pixels is in data-driven programming state, odd column pixel remains original data mode.
Beneficial effect
Compared to existing technology, tool of the present invention has the following advantages:
A kind of OLED data drive circuit is formed by with lower part: current feed-forward part; Current feedback part; Comparison amplifier; Dynamic compensation part; Bias supply; This data drive circuit can fast speed, accurately give current mode TFTOLED pixel programming.
(1) program speed is fast.Voltage condition also according to OLED pixel circuit outside program current Idata introduces transient current IM3, this can offset the delay in the programming process that OLED pel array brings due to the discharge and recharge of stray capacitance CL, so current programmed speed improves significantly.Even in small area analysis, heavy load electric capacity situation, current programmed speed still can meet the performance requirement of high resolving power, large-size display panel.
(2) circuit stability is good, and programming precision is high.By the method for dynamic compensation, comparatively stable big current can be exported.Meanwhile, the feature that the fast speed of small area analysis is programmed and programming precision is high can also be kept.
(3) circuit structure is simple, and hardware cost is low.This current driving circuit can embed the framework of ripe TFTLCD source electrode driver, and structure is simple, and hardware increases less.
(4) compared to methods such as minimizing stray capacitance, increase program currents, this active TFT-OLED panel technology newly does not need to change TFT panel process significantly, and feasibility is higher.
Compared with common active TFT-OLED panel, the twice that the raster data model line of this active TFTOLED panel based on dynamic compensation data drive circuit is, and the pixel in a gate line direction is divided into different two groups according to the parity of place data line, the gated sweep time of two groups of pixels in same line direction is the half of gated sweep time on general panels respectively, and the pixel in same line direction is sequentially opened in these two groups of controlling grid scan line complementations; And the time sequence control logic of the driving method of described panel is simple, implementation complexity is low.
(5) the unit pixel circuit of this TFTOLED panel only needs four TFT, and the structure of panels en bloc is simple, can ensure higher yield rate.
Accompanying drawing explanation
Fig. 1 is TFTOLED panel construction schematic diagram;
Fig. 2 is TFTOLED pixel schematic diagram, wherein, and (a) voltage-type, (b) current mode;
Fig. 3 is current mode TFTOLED pixel equivalent circuit figure, and wherein, figure (a) is detailed equivalent circuit diagram, the current programmed design sketch that figure (b) is circuit equivalent OLED pixel;
Fig. 4 is the effect schematic diagram adopting constant current source drive current type TFTOLED pixel;
Fig. 5 is TFTOLED current driving circuit block diagram of the present invention;
Fig. 6 is the comparison amplifier circuit diagram of TFTOLED current driving circuit of the present invention;
Fig. 7 is transient response (a) small area analysis transient response (b) the big current transient response of TFTOLED current driving circuit of the present invention;
Fig. 8 is circuit diagram and the transient response figure that capacitance compensation improves big current transient response;
Fig. 9 is the TFTOLED current driving circuit that the present invention adopts the fast speed of dynamic compensation;
Figure 10 is the transient response that the present invention adopts the TFTOLED current driving circuit of the fast speed of dynamic compensation, wherein, and (a) big current transient response, (b) small area analysis transient response;
Figure 11 is the panel construction schematic diagram that TFTOLED electric current of the present invention drives.
Embodiment
Below in conjunction with drawings and Examples, the present invention is described further.
Fig. 1 TFTOLED panel construction schematic diagram.This display panel is made up of two-dimensional array, gate line, data line.In the periphery of TFTOLED panel, gate drivers and data driver is needed to provide gated sweep signal and data drive signal respectively.Different from TFTLCD, TFTOLED is current drive type display part.Therefore require the drive current that the image element circuit of TFTOLED can provide stable, make TFTOLED send the light with respective strengths, realize display GTG.Here, the type of TFT can be non-crystalline silicon tft, multi-crystal TFT, organic tft or oxide TFT.Here only explain for oxide TFT display panel, but disclosed Driving technique can not be thought and is only confined to oxide TFT display panel.
Fig. 2 is TFTOLED pixel schematic diagram of the prior art.Wherein, Fig. 2 (a) is voltage-type TFTOLED pixel schematic diagram, and Fig. 2 (b) is current mode TFTOLED pixel schematic diagram.Voltage-type TFTOLED image element circuit is by selecting pipe T
swith driving tube T
dform.When gated sweep signal is high level, select pipe T
sopen, driving tube T
dgate-to-source be programmed into voltage corresponding to certain gray scale.When gated sweep signal is low level, select pipe T
sclose, driving tube T
dthere is provided the drive current that correspond to certain gray shade scale to pixel OLED.
Current mode TFTOLED image element circuit is by two switch transistor T 1 and T2, and mirror image pipe T3 and driving tube T4 is formed.When gated sweep signal is high level, pipe T1 and T2 is selected to open.The gate-to-drain of mirror image pipe T3 is shorted to together.Because the electric current of mirror image pipe T3 equals program current I
dATA, the gate-to-drain of mirror image pipe T3 according to current-voltage relation by program current I
dATAdetermine.
When gated sweep signal is high level, pipe T1 and T2 is selected to close.The drain electrode of mirror image pipe T3 does not have electric current to flow through because suspend yet.But because the memory action of the gate source capacitance of T3, between the gate-to-source of mirror image pipe T3, remain the voltage corresponding to certain gray scale.The gate-to-source of driving tube T4 is connected with the gate-to-source of mirror image pipe T3 respectively.Therefore program current I
dATAaccording to driving tube T4 and the channel width of mirror image pipe T3, the ratio of length and by the channel current of exact mirror image to driving tube T4.This relation can reach by following mathematical expression sublist:
Although the voltage-type pixel-driving circuit shown in Fig. 2 (a) has the simple advantage of structure, for TFT performance drift and uneven cannot realize compensate.Thus the drive current that exports of this image element circuit finally can be unstable and have influence on the effect of display.Current mode image element circuit shown in Fig. 2 (b) can realize compensating the performance drift of TFT and uneven realization, is a kind of pel array design proposal being hopeful to be applied in the AMOLED panel of high image quality.
Expression formula (1) and (2) merely depict current-voltage relation during stable state.In fact, due to factors such as the stray capacitances that image element circuit inside and periphery exist, finally to reach the stable solution of (1) and (2), need through one section of transient process.Such as, the drain electrode of T1 is connected to data line, due to the reason such as the overlapping stray capacitance of gate-to-drain of overlapping, T1 and T2 of data line-gate line, data line has no small stray capacitance C
l.In the stage that T1 and T2 is strobed, stray capacitance C
lrelation in parallel with the path T1 ~ T3 programmed to OLED.Therefore I is reached at the On current of T3 pipe
dATAbefore, stray capacitance C
lalso certain electric current to be absorbed, then suitable voltage could be set up at the grid of T3 and drain electrode.Stray capacitance C in other words
lon also want the regular hour can be formed and program current I
dATAcorresponding voltage, transient process is necessary is called as Time Created (settlingtime) during this period of time.
According to the panel driving mechanism of AMOLED, should control Time Created can reach high-resolution image within the gated sweep time.Qualitatively analyze is known, the value of Time Created and stray capacitance C
l, program current I
dATAvalue relevant.Shorten Time Created, have following certain methods: (1) reduces stray capacitance C
lvalue; (2) program current I is increased
dATA; (3) stray capacitance C is given in advance
lon be charged to and program current I
dATAcorresponding magnitude of voltage.
The exact value of Time Created will by the transient process of research image element circuit, and the equation of solution electric current, voltage relationship obtains.Fig. 3 is the equivalent circuit diagram of OLED pixel.Wherein Fig. 3 (a) is more detailed equivalent circuit diagram.In Fig. 3 (a), because circuit is still comparatively complicated, still there is more non-linear elements, be not easy the analytic solution obtaining circuit.Therefore, assuming that voltage is comparatively stable on OLED, and by regulating V
sSvalue, make the anode potential of OLED close to zero level; Also suppose R
t1and R
t2in the conducting resistance of programming phases much smaller than T3, and ignore R
t1and R
t2on the impact of image element circuit programming transient process.On the basis of this supposition, adopt the current programmed process of circuit equivalent OLED pixel as Suo Shi Fig. 3 (b).
In order to the Time Created under worst case of deriving, assuming that when t=0, the electric current that the T3 that diode connects flows through is 0.From analysis above, after current programmed beginning, program current I
dATAbe divided into two-way transmission, its first via flows through the T3 of conducting, and its second tunnel is to C
lcharging.Under the effect of this second road electric current, C
lon be stored the enough electric charges of epipodium, the current potential therefore on it is raised step by step.Work as C
lon voltage be less than V
t3time, T3 is still in the region of below threshold voltage, and therefore on T3, almost no current flows through; At this moment, I
dATAmost current to C
lcharging.Work as C
lupper voltage is more than V
t3time, I
dATAmost current flowed away by T3, C
lon voltage tend towards stability gradually.When steady state (SS), C
lon voltage no longer change, current value that its value is flow through by T3 determines.Therefore:
I
data＝I
CL+I
T3(3)
Wherein:
In upper formula, V is C
lon voltage, β is the conducting factor of T3.
Can solve
Wherein, time factor τ equals
As can be seen from the expression formula of time factor, because C on data line
lcomparatively large, the time factor of current mode image element circuit is larger.This means the problem that the programming adopting simple constant current source to carry out current mode image element circuit can cause programming time oversize.Especially at program current I
dATAtime less, problem is more serious.Such as, typical program current is maximal value 1 μ A, and minimum program current 20nA, then the difference of the time constant of the two reaches 7 times.
On the other hand, the larger TFT of the conducting factor is adopted to be hopeful to reduce time factor.The main way increasing the conducting factor is the size increasing T3, improves the mobility etc. of TFT.But many results of study show, even if adopt the higher IGZOTFT of mobility, constant current source is adopted to carry out current programmedly still to adopt current programmed mode in high-resolution applications occasion to pixel.Fig. 4 simulates the employing IGZOTFT that obtains (mobility is 8cm (V.s)
-1) the electric current corresponding relation figure of current mode pixel programming circuit.In the IGZOTFT situation that have employed higher carrier mobility, C
leven if reduced to 2pF, at program current I
dATAafter being less than 0.4uA, even if the difference of program current reaches 0.1 μ A all become undistinguishable.Therefore, because electric current is long for Time Created, particularly the Time Created of small area analysis is long, if adopt simple constant current source to carry out the programming display of current mode image element circuit, cannot obtain acceptable resolution.
Fig. 5 is disclosed a kind of current driving circuit realizing fast programming.The main thought of this invention utilizes electronic feedback to produce extra electric current, and this extra current is used for compensating because stray capacitance C
lcharging and the program current loss that causes, thus realize fast programming.Below in conjunction with accompanying drawing, how the current driving circuit describing this fast programming in detail realizes.
As shown in Figure 5, a kind of OLED data drive circuit, comprises current feed-forward module, current feedback module, comparison amplifier and bias supply;
Wherein, the outside input current source Idata of described data drive circuit is all connected with the input end of described current feed-forward module with the output terminal of described current feedback module, the electric current of the control end of described current feed-forward module is the outside input current Idata of data drive circuit and the electric current sum of current feedback module output, and the output current of described current feed-forward module is used for OLED pixel cell and drives;
The first input end of described comparison amplifier is connected to the input end of described current feed-forward module, and the second input end connects reference voltage source V
r, output terminal is connected with the control end of described current feed-forward module and the input end of described current feedback module;
The input end of described current feedback module is connected with the output terminal of described comparison amplifier, and output terminal output feedack electric current is to the first input end of described comparer;
Described bias supply output reference voltage, to comparison amplifier, exports reference current to described current feed-forward module and current feedback module.
Described current feed-forward module comprises the first transistor M1, and described the first transistor M1 is N-type metal-oxide-semiconductor;
First node n1 is the first input end of described comparison amplifier, and Section Point n2 is the output terminal of described comparison amplifier, and the 3rd node n3 is described first current source I
b1positive pole;
The drain coupled of described the first transistor is to first node n1, and grid is coupled to Section Point n2, and source class is coupled to the 3rd node n3.
Generated data electric current I data and current feedback portion of electrical current, and by add and electric current export and be provided to OLED pixel cell.
Described current feedback module comprises transistor seconds M2, third transistor M3 and the 4th transistor M4, and described transistor seconds M2 is N-type metal-oxide-semiconductor, and third transistor M3 and the 4th transistor M4 is P type metal-oxide-semiconductor;
Described 4th node n4 is described second current source I
b2positive pole, described 5th node n5 is the drain electrode of the 4th transistor;
The source class of described third transistor M3 and the 4th transistor M4 is all coupled to the first voltage source Vcc, the grid of described third transistor M3 and the 4th transistor M4 is all coupled to the 5th node n5, the drain electrode of described 4th transistor M4 is all coupled in the 5th node n5, the drain electrode of described third transistor is connected with the drain electrode of described the first transistor M1, and is coupled in first node n1; The drain coupled of described transistor seconds M2 is to the 5th node n5, and grid is connected with the grid of described the first transistor M1 and is coupled in Section Point n2, and source-coupled is in the 4th node n4.
Dynamically regulate the charge/discharge current of data line load capacitance on TFT panel according to OLED pixel voltage, reach the programming time reducing OLED pixel, the object accelerating programming process.
The positive input terminal of described comparison amplifier is connected with first node n1, negative input end and reference voltage source V
rbe connected, output terminal is connected with Section Point n2.
Relatively data line voltage and reference voltage, and regulate current feed-forward and feedback module according to the result compared.
Below the qualitative analysis of circuit shown in Fig. 5:
Under the effect of comparison amplifier and current feedback path, the electric current of supply OLED pixel is except I
dATA, the electric current provided from M3 has in fact also been provided.Therefore, I
dATAand be jointly supplied to the stray capacitance OLED pixel and oled panel on data line from the electric current that M3 flows out.In theory, if the electric current that M3 provides just in time corresponds to stray capacitance C
lcharge/discharge current, then program current correspond to OLED pixel current; And if the electric current that M3 provides is instantaneous and correspond to stray capacitance C exactly
lcharge/discharge current, then the programming time of OLED pixel is 0.
The correctness of above qualitative analysis can be verified by calculating the transient process of this current driving circuit.As shown in Figure 5, C
l1and C
l2the stray capacitance on adjacent two alignments respectively.On same panel, on adjacent alignment, the matching degree of parasitic capacitance value is higher in theory.Add the designed in mirror image of this driving circuit, suppose C
l1and C
l2upper voltage is identical.Therefore:
In addition
Suppose
C
L1＝C
L2(11)
Then
I
data＝I
OLED(12)
Above expression formula illustrates, if this current compensation can accurately and also speed enough soon, then I
oLEDwith program current I
dATAone_to_one corresponding, and this corresponding relation had nothing to do with the time.In other words, ideally, due to this current compensation, the current programmed time of OLED is 0.But in fact, imperfect due to comparison amplifier, the gain bandwidth (GB) of such as comparison amplifier is limited; In addition there is the factors such as unsymmetrical factors in circuit itself, and the generation of OLED electric current still needs the regular hour, and just this programming time has benefited from this current compensation mechanism and can greatly reduce.
Described comparison amplifier also comprises the 5th transistor M5, the 6th transistor M6, the 7th transistor M7, the 8th transistor M8 and the 3rd current source IB
3, described 5th transistor M5 and the 6th transistor M6 is P type metal-oxide-semiconductor, and the 7th transistor M7 and the 8th transistor M8 is N-type metal-oxide-semiconductor;
6th node n6 is described 3rd current source I
b3negative pole, the 7th node n7 is the drain electrode of the 5th transistor;
Described 3rd current source IB
3positive pole be coupled to the first voltage source Vcc, negative couplings is to the 6th node n6;
The source class of described 5th transistor M5 and the 6th transistor M6 is all coupled to the 6th node n6, and the grid of described 5th transistor M5 is coupled with first node n1, and the drain coupled of described 5th transistor M5 is in the 7th node n7; The grid of described 6th transistor M6 and described reference voltage source V
rbe connected, the drain coupled of described 6th transistor M6 is to Section Point n2;
The equal ground connection of source class of described 7th transistor M7 and the 8th transistor M8, the grid of described 7th transistor M7 and the 8th transistor M8 is all coupled in the 7th node n2, and the drain coupled of described 8th transistor M8 is in Section Point n2.
Fig. 6 signal be a kind of realizing circuit of comparison amplifier.The positive input terminal V of this comparison amplifier
i+be connected to I
dATA, negative input end VI-is connected to reference voltage source V
r.Work as V
i+be less than V
i-time, export as low level voltage.Now, M1 and M2 turns off.The drain voltage being conducive to M1 like this accumulates rapidly, rises.Work as V
i+rise and exceed reference voltage source V
rtime, export as high level voltage.Thus M1 and M2 opens fully, the source electrode of M1 and M2 is lifted to higher level.Thus C
l1and C
l2on obtain high level voltage rapidly.After adopting the amplifier architecture shown in Fig. 6, V
i+and the positive and negative difference between reference voltage source is amplified all rapidly and feeds back on the grid of M1 and M2.Can be regulated by the grid voltage of M1 and M2 like this, control to C
land T
othe size of charge volume.Thus reach the effect automatically controlled.
Fig. 7 is the transient response that the data drive circuit proposed the present invention simulates the TFTOLED current driving circuit of the fast speed obtained.Wherein Fig. 7 (a) is the transient response of the transient response of small area analysis, Fig. 7 (b) big current.Compared to Fig. 4, after adopting current driving circuit of the present invention, the electric current of TFTOLED pixel drives transient response greatly to improve.Especially at low currents, even be less than the data current of 20nA, also within the programming time of 10 μ s, programming can be completed exactly.Therefore, after have employed this fast speed current driving circuit, the resolution of TFTOLED can bring up to the even above level of XGA.
But as shown in Fig. 7 (b), vibrating more significantly has appearred in the big current transient response of this current driver.Although these current oscillations finally can settle out, and level off to desired program current value, these oscillating currents are finally stable needs many time.Such as, in the program current situation of 1 μ A, oscillating current stable more than 20 μ s.On the other hand, these current oscillations very likely cause circuit bias unstable, and final amplifier and circuit enter de-synchronization state, thus the display effect of effect diagram picture.Therefore, the current oscillation of current driver in big current situation is needed to take measures to suppress.
According to channel frequency compensation principle, add the frequency response that building-out capacitor can improve circuit in circuit, suppress the vibration that circuit exports.As a kind of embodiment, such as, between the gate-to-drain of M2, add building-out capacitor, then can improve the transient response of big current significantly.Fig. 8 illustrates the fast current drive circuit and transient analysis schematic diagram with building-out capacitor.Wherein, Fig. 8 (a) is a kind of fast current drive circuit with building-out capacitor; Fig. 8 (b) is the transient analysis analog result of this fast current drive circuit.
On the one hand, building-out capacitor can suppress the vibration of program current.Such as, I is worked as
dATAwhen being 1 μ A, being reduced to Time Created and being less than 10 μ s.This is because two reasons: the grid of (1) M1, M2 adds the value exporting limit because of adding of building-out capacitor.(2) building-out capacitor too increases the value of the drain electrode limit of M2.Under the increase of these two limits all makes big current situation, the generation of feedback current slows.Therefore in large current characteristic, vibration reduces.
But another aspect, the increase due to above-mentioned two inherent pole makes the transient response of small area analysis be deteriorated.As shown in Figure 8, the programming time of 0.1 μ s is increased to from 7 original μ s and is greater than 25 μ s.Therefore, although big current characteristic improvement due to frequency compensation, the output of small area analysis then becomes slow.The fast programming of small area analysis and big current can not be realized only by increase building-out capacitor simultaneously.
Therefore, need a kind of compensatory approach of intelligence: do not need when small area analysis to compensate, keep the fast programming of small area analysis; Be only when exporting the big current for vibration, the mechanism of compensation just plays a role, stabilizing output current, this compensation method and dynamic compensation.
Also comprise dynamic compensation module, the output terminal of described dynamic compensation module is connected with the input end of described current feed-forward part and the output terminal of described comparison amplifier, and described bias supply is described dynamic compensation module for power supply.
Described dynamic compensation module comprises the 9th transistor Mp and building-out capacitor Cp; Described 9th transistor MP is N-type metal-oxide-semiconductor;
Described 8th node n8 is the source class of the 9th transistor;
The grid of described 9th transistor Mp is coupled to Section Point n2, and drain coupled is to first node n1, and source-coupled is to the 8th node n8;
The first end of described building-out capacitor Cp is coupled to the 8th node n8, the second end ground connection.
Dynamically adjust the depth of feedback of building-out capacitor, when program current is larger, implements depth compensation, suppress the voltage oscillation on the output node of described comparison amplifier, thus reduce the ripple current of described current feed-forward module and current feedback module; When program current is less, implements shallow compensation and even close compensating module, improve the response speed of described comparison amplifier, thus strengthen the effect of described current feed-forward and the programming of feedback module acceleration small area analysis.
Fig. 9 is a kind of current driving circuit based on dynamic compensation principle.C
pbuilding-out capacitor, M
pit is switching tube.Only when program current is big current, the grid potential of M1 and M2 just can rise to high potential and open M
p.And program current is when being small area analysis, the grid potential of M1 and M2 is still not enough to open M
p.Therefore on the one hand, when being programmed for big current, in transient process, input end has newly increased building-out capacitor C
p, this is beneficial to for current oscillation when suppressing big current.On the other hand, when being programmed for small area analysis, equalizing network does not have conducting, and therefore small area analysis program speed is still very fast, can't be subject to the impact of building-out capacitor.Thus this circuit can realize the fast programming of big current and small area analysis simultaneously.
Figure 10 is the transient response simulating the current driving circuit based on dynamic compensation principle obtained.Wherein Figure 10 (a) is the transient response of the transient response of big current, Figure 10 (b) small area analysis.Compared to Fig. 4 and Fig. 7, adopt this based on after the current driving circuit of dynamic compensation principle, the electric current driving transient response of TFTOLED pixel obtains greatly to be improved.In whole program current situations, output is not only stable, and all remains speed faster.Development is continued in TFT technology, when mobility is higher, stray capacitance is less, the current driving circuit of this dynamic compensation principle is expected to the electric current actuating speed of TFTOLED pixel to rise to 5 below μ s, thus realize giant-screen, high-resolution AMOLED shows.
A kind of active TFTOLED panel based on OLED data drive circuit, OLED data drive circuit described in employing, include N*M OLED pixel cell, wherein N is the pixel quantity of active TFTOLED panel array column direction, M is the pixel quantity of active TFTOLED panel array line direction, N and M is the integer being more than or equal to 1;
Described active TFTOLED panel array includes 2*N bar raster data model line V
g 1~ V
g 2N, M bar data drive wire V
d 1~ V
d m;
By two raster data model line V on described active TFTOLED panel array
g 2k-1, V
g 2kdrive a line TFTOLED pixel, and as one group of raster data model line, wherein k is integer, and 1≤k≤N;
Often organize connected pixel on raster data model line and be divided into two classes according to the parity of place alignment serial number, comprise odd column pixel and even column pixels; The raster data model end of odd column pixel is connected to raster data model line V
g 2k-1, data-driven end is connected to the 3rd node n3 of described OLED data drive circuit; The raster data model end of even column pixels is connected to raster data model line V
g 2k, data-driven end is connected to the 4th node n4 of described OLED data drive circuit.
The structural representation of the TFTOLED panel that Figure 11 is corresponding with this current driving circuit.General T FTOLED panel construction in prior art shown in comparison diagram 1, the raster data model line of this panel is the twice of general panels, and the pixel in a gate line direction is divided into different two groups according to the parity of place data line.Its course of work is with the first behavior example: the pixel of the first row is divided into first group and second group, the grid of the selection TFT of its first group of pixel is all connected to VG (1,1), the grid of the selection TFT of its second group of pixel is all connected to VG (1,0).
When VG (1,1) is high level, when VG (1,0) is for low level, the odd column TFTOLED pixel-parallel ground programming in the first row, in the first row, the TFTOLED pixel of even column turns off, and is non-programmable state.Now, the electric capacity on even column is the building-out capacitor C as above-mentioned current driver
l2, and the electric capacity on odd column is only the load capacitance C of current driver
l1.
When VG (1,0) is high level, when VG (1,1) is for low level, the even column TFTOLED pixel-parallel ground programming in the first row, in the first row, the TFTOLED pixel of odd column turns off, for keeping current data state.Now, the electric capacity on odd column is the building-out capacitor C as above-mentioned current driver
l2, and the electric capacity on even column is only the load capacitance CL1 of current driver.
Above-described embodiment is citing of the present invention, although disclose most preferred embodiment of the present invention and accompanying drawing for the purpose of illustration, but it will be appreciated by those skilled in the art that: without departing from the spirit and scope of the invention and the appended claims, various replacement, change and amendment are all possible.Therefore, the present invention should not be limited to the content disclosed in most preferred embodiment and accompanying drawing.
Claims (10)
1. an OLED data drive circuit, is characterized in that, comprises current feed-forward module, current feedback module, comparison amplifier and bias supply;
Wherein, the outside input current source Idata of described data drive circuit is all connected with the input end of described current feed-forward module with the output terminal of described current feedback module, the electric current of the control end of described current feed-forward module is the outside input current Idata of data drive circuit and the electric current sum of current feedback module output, and the output current of described current feed-forward module is used for OLED pixel cell and drives;
The first input end of described comparison amplifier is connected to the input end of described current feed-forward module, and the second input end connects reference voltage source V
r, output terminal is connected with the control end of described current feed-forward module and the input end of described current feedback module;
The input end of described current feedback module is connected with the output terminal of described comparison amplifier, and output terminal output feedack electric current is to the first input end of described comparer;
Described bias supply output reference voltage, to comparison amplifier, exports reference current to described current feed-forward module and current feedback module.
2. described OLED data drive circuit according to claim 1, it is characterized in that, described bias supply comprises the first current source IB
1, the second current source IB
2and reference voltage source V
r, described first current source I
b1with the second current source I
b2be respectively current feed-forward module and current feedback module provides electric current, described reference voltage source V
rfor described comparison amplifier is powered;
Described first current source IB
1with the second current source IB
2the equal ground connection of negative pole.
3. OLED data drive circuit according to claim 2, is characterized in that, described current feed-forward module comprises the first transistor M1, and described the first transistor M1 is N-type metal-oxide-semiconductor;
First node n1 is the first input end of described comparison amplifier, and Section Point n2 is the output terminal of described comparison amplifier, and the 3rd node n3 is described first current source I
b1positive pole;
The drain coupled of described the first transistor is to first node n1, and grid is coupled to Section Point n2, and source class is coupled to the 3rd node n3.
4. OLED data drive circuit according to claim 3, it is characterized in that, described current feedback module comprises transistor seconds M2, third transistor M3 and the 4th transistor M4, and described transistor seconds M2 is N-type metal-oxide-semiconductor, and third transistor M3 and the 4th transistor M4 is P type metal-oxide-semiconductor;
4th node n4 is described second current source I
b2positive pole, the 5th node n5 is the drain electrode of the 4th transistor;
The source class of described third transistor M3 and the 4th transistor M4 is all coupled to the first voltage source Vcc, the grid of described third transistor M3 and the 4th transistor M4 is all coupled to the 5th node n5, the drain electrode of described 4th transistor M4 is all coupled in the 5th node n5, the drain electrode of described third transistor is connected with the drain electrode of described the first transistor M1, and is coupled in first node n1; The drain coupled of described transistor seconds M2 is to the 5th node n5, and grid is connected with the grid of described the first transistor M1 and is coupled in Section Point n2, and source-coupled is in the 4th node n4.
5. OLED data drive circuit according to claim 4, is characterized in that, the positive input terminal of described comparison amplifier is connected with first node n1, negative input end and reference voltage source V
rbe connected, output terminal is connected with Section Point n2.
6. OLED data drive circuit according to claim 5, is characterized in that, described comparison amplifier also comprises the 5th transistor M5, the 6th transistor M6, the 7th transistor M7, the 8th transistor M8 and the 3rd current source IB
3, described 5th transistor M5 and the 6th transistor M6 is P type metal-oxide-semiconductor, and the 7th transistor M7 and the 8th transistor M8 is N-type metal-oxide-semiconductor;
6th node n6 is described 3rd current source I
b3negative pole, the 7th node n7 is the drain electrode of the 5th transistor;
Described 3rd current source IB
3positive pole be coupled to the first voltage source Vcc, negative couplings is to the 6th node n6;
The source class of described 5th transistor M5 and the 6th transistor M6 is all coupled to the 6th node n6, and the grid of described 5th transistor M5 is coupled with first node n1, and the drain coupled of described 5th transistor M5 is in the 7th node n7; The grid of described 6th transistor M6 and described reference voltage source V
rbe connected, the drain coupled of described 6th transistor M6 is to Section Point n2;
The equal ground connection of source class of described 7th transistor M7 and the 8th transistor M8, the grid of described 7th transistor M7 and the 8th transistor M8 is all coupled in the 7th node n2, and the drain coupled of described 8th transistor M8 is in Section Point n2.
7. the OLED data drive circuit according to any one of claim 1-6, it is characterized in that, also comprise dynamic compensation module, the output terminal of described dynamic compensation module is connected with the input end of described current feed-forward part and the output terminal of described comparison amplifier, and described bias supply is described dynamic compensation module for power supply.
8. OLED data drive circuit according to claim 7, is characterized in that, described dynamic compensation module comprises the 9th transistor Mp and building-out capacitor Cp; Described 9th transistor MP is N-type metal-oxide-semiconductor;
8th node n8 is the source class of the 9th transistor;
The grid of described 9th transistor Mp is coupled to Section Point n2, and drain coupled is to first node n1, and source-coupled is to the 8th node n8;
The first end of described building-out capacitor Cp is coupled to the 8th node n8, the second end ground connection.
9. the active TFTOLED panel based on OLED data drive circuit, it is characterized in that, adopt the OLED data drive circuit described in any one of claim 1-8, include N*M OLED pixel cell, wherein N is the pixel quantity of active TFTOLED panel array column direction, M is the pixel quantity of active TFTOLED panel array line direction, N and M is the integer being more than or equal to 1;
Described active TFTOLED panel array includes 2*N bar raster data model line V
g 1~ V
g 2N, M bar data drive wire V
d 1~ V
d m;
By two raster data model line V on described active TFTOLED panel array
g 2k-1, V
g 2kdrive a line TFTOLED pixel, and as one group of raster data model line, wherein k is integer, and 1≤k≤N;
Often organize connected pixel on raster data model line and be divided into two classes according to the parity of place alignment serial number, comprise odd column pixel and even column pixels; The raster data model end of odd column pixel is connected to raster data model line V
g 2k-1, data-driven end is connected to the 3rd node n3 of described OLED data drive circuit; The raster data model end of even column pixels is connected to raster data model line V
g 2k, data-driven end is connected to the 4th node n4 of described OLED data drive circuit.
10. the driving method based on the active TFTOLED panel of OLED data drive circuit, it is characterized in that, adopt the active TFTOLED panel based on OLED data drive circuit according to claim 9, often organize connected pixel on raster data model line and be divided into two classes according to the parity of place alignment, comprise odd column pixel and even column pixels, odd column pixel and even column pixels complementation are programmed: when in odd even ordered series of numbers pixel, when wherein a row pixel is in data-driven programming state, another row pixel is for keeping current state.
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| JP2016192665A (en) * | 2015-03-31 | 2016-11-10 | ラピスセミコンダクタ株式会社 | Semiconductor device |
| CN105139799B (en) * | 2015-06-26 | 2018-02-06 | 中山大学 | A kind of AMOLED display pixels point drive circuit and its driving method |
| CN108062189A (en) * | 2018-01-22 | 2018-05-22 | 京东方科技集团股份有限公司 | Capacitance compensation module, method and touch control display apparatus |
| CN108428431B (en) * | 2018-03-19 | 2020-03-24 | 联想(北京)有限公司 | Screen and display compensation method |
| CN110796993B (en) * | 2019-11-15 | 2022-03-08 | 福州京东方光电科技有限公司 | Voltage compensation circuit and display device |
| CN111048029B (en) * | 2019-12-31 | 2023-05-05 | 视涯科技股份有限公司 | Data driving circuit, driving chip, display device and driving method thereof |
| CN111432520B (en) * | 2020-04-02 | 2022-04-19 | 晟合微电子(肇庆)有限公司 | Equalization method for driving OLED panel with low power consumption |
| CN111599311B (en) * | 2020-05-28 | 2021-04-23 | 维沃移动通信有限公司 | Pixel circuit, display unit and terminal equipment |
| CN111785211B (en) * | 2020-07-29 | 2021-12-10 | 武汉天马微电子有限公司 | Pixel driving circuit, driving method, display panel and display device |
| CN112289270B (en) | 2020-12-28 | 2021-03-23 | 上海视涯技术有限公司 | Source electrode driving circuit, display device and pixel driving method |
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