CN1312650C - Method and device capable of making active organic light-emitting diode display produce uniform image - Google Patents
Method and device capable of making active organic light-emitting diode display produce uniform image Download PDFInfo
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- CN1312650C CN1312650C CNB031091032A CN03109103A CN1312650C CN 1312650 C CN1312650 C CN 1312650C CN B031091032 A CNB031091032 A CN B031091032A CN 03109103 A CN03109103 A CN 03109103A CN 1312650 C CN1312650 C CN 1312650C
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Abstract
The present invention relates to a method and a device for uniformly imaging for an active organic light emitting diode display. The display is composed of a plurality of pixel devices, wherein each pixel device is provided with a driving unit which is used for driving an organic light emitting diode to be brightened. The cathode of the organic light emitting diode is connected with a positive power supply, and thereby, the positive power supply supplies the voltage to improve the electric potential of the organic light emitting diode. Further, when each driving unit acts, the Vsd (the voltage difference of a source electrode and a drain electrode) of the driving unit is reduced, and the Vsg (the voltage difference of the source electrode and a grid electrode) is unchanged. When each driving unit has different initial voltages because of the change of characteristics, the difference of the output current of each driving unit is reduced when the driving unit is conducted.
Description
Technical field
The present invention relates to a kind of positive type organic light emitting diode display image uniform method and device, be particularly related to a kind of by reducing drive thin film transistors (Driving TFT) Vsd (source electrode, drain voltage poor) and keep its Vsg (source electrode, grid voltage poor) so that the unlikely variation of output current of each drive thin film transistors (Driving TFT) is excessive.
Background technology
Known Thin Film Transistor-LCD (TFT LCD) technology is divided into amorphous silicon film transistor (α-Si TFT) and two kinds of polycrystalline SiTFTs (Poly-Si TFT) at present, general alleged Thin Film Transistor-LCD (TFT LCD) is meant amorphous silicon film transistor (α-Si TFT), technology maturation is the main product of LCD (LCD) at present.And the maximum difference of low-temperature polysilicon film transistor (LTPS TFT) and amorphous silicon film transistor (α-Si TFT) is that the transistor of low temperature polycrystalline silicon (LTPS) need further accept the making step of laser tempering, (film of α-SiTFT) changes layer polysilicon film into amorphous silicon film transistor, make low temperature polycrystalline silicon (LTPS) more orderly than the arrangement of amorphous silicon film transistor (α-Si TFT) on the silicon wafer structure, therefore can improve electronic conduction speed reaches 200cm
2/ V-sec.Low temperature polycrystalline silicon (LTPS) technology can make element do forr a short time, and whole TFT element area is dwindled more than 50%; And promote aperture opening ratio (aperture ratio), under same size, can produce higher resolution with respect to α-Si TFT LCD, and reduce the consumption of power.In addition, low-temperature polysilicon film transistor (LTPS TFT) also possesses power saving, brightness height, picture is meticulous, frivolous and the few advantages such as (less than 200 contacts, increased qualification rate, α-Si TFT need greater than 3842 contacts) of contact.
Yet, because the thin film transistor (TFT) of manufacturing must be through the process of a laser tempering during low temperature polycrystalline silicon (LTPS) was made, often cause the starting potential (ThresholdVoltage) and the drift rate (Mobility) of thin film transistor (TFT) to change to some extent, make that the characteristic of each thin film transistor (TFT) (TFT) element can be different, so, when drive system is used simulation (analog) modulation mode with the performance GTG, Chang Yinwei thin film transistor (TFT) (TFT) is accepting behind the making step of laser tempering different qualities is arranged, even write identical voltage signal, but the Organic Light Emitting Diode of different pixels produces different electric currents, and sends the brightness of different sizes.This phenomenon can make organic LED panel demonstrate the image of GTG mistake, havoc image uniformity (Image Uniformity).
" thin-film display of organic electroluminescent device " of U.S. Pat 5684365 again, its proposition is a kind of by two thin film transistor (TFT)s and the image element circuit that electric capacity is formed, when this pixel arrangement during in the scan-image data, this switch element presents conducting state, this moment, image data was entered in the switch element by data line, after sweep trace scanning, and be stored in the storage element (also being after the switch element conducting) to the storage element charging, the voltage difference of storage element can provide the Vsg (source electrode as driver element, grid voltage is poor), make this driver element output current to organic electroluminescent element, and the brightness that organic electroluminescent element sent is proportional to the size of current of this element of flowing through.Yet this kind pixel arrangement just can cause the organic electroluminescent element non-uniform light when if the element characteristic of driver element occurs variation because of the manufacturing process restriction, and the destruction image uniformity.
So, for improving the problem of display image uniformity, just there is the dealer to develop and digital driving framework, and show GTG by time scale (Time Ratio) modulation mode, its operating principle is by the conducting of control TFT (TFT) (ON) and by (OFF), that controls Organic Light Emitting Diode (OLED) is shinny and not shinny, and the ratio that the shinny time by OLED accounts for frame time (Frame Time) decides image gray scale.
Yet, drive Organic Light Emitting Diode with digital form, but exist following gordian technique to demand urgently breaking through:
(1) each thin film transistor (TFT) is when conducting state on the display pannel, and the difference of institute's output current size must be enough little.
(2) on the display pannel each thin film transistor (TFT) when cut-off state, must guarantee all TFT all can be fully by and without any output.
Summary of the invention
So, fundamental purpose of the present invention, be to solve above-mentioned traditional defective, for avoiding the existence of this defective, positive type organic light emitting diode display image uniform method of the present invention and device, negative electrode by each Organic Light Emitting Diode is connected to a positive supply, so as to improving the current potential of Organic Light Emitting Diode, the Vsd (source electrode, drain voltage poor) of drive TFT is reduced, Vsg (source electrode, grid voltage poor) then remains unchanged, make each thin film transistor (TFT) when conducting state, the difference of institute's output current size is dwindled.
For reaching above-mentioned purpose, the present invention adopts positive type organic light emitting diode display image uniform method and device, this display is made of a plurality of pixel arrangement, it is shinny to drive Organic Light Emitting Diode that each pixel arrangement has a driver element, the negative electrode of this Organic Light Emitting Diode is connected a positive supply, thereby provide voltage to improve the current potential of Organic Light Emitting Diode by this positive supply, and then make driver element at its Vsd (source electrode of when action, drain voltage is poor) reduce, and Vsg (source electrode, grid voltage is poor) then remain unchanged, then when each driver element has different starting potential (Threshold Voltage) because of the characteristic variation, the difference of each driver element its output current when conducting is dwindled.
Description of drawings
Fig. 1 is a circuit diagram of the present invention.
Fig. 2 is the current-voltage synoptic diagram of driver element.
Fig. 3 is the current-voltage synoptic diagram (two) of driver element.
Embodiment
To detailed content of the present invention and technical descriptioon, as follows now with reference to description of drawings:
Seeing also shown in Figure 1ly, is circuit diagram of the present invention.As shown in the figure: positive type organic light emitting diode display image uniform method of the present invention and device, this display is made of a plurality of pixel arrangement 10, it is shinny to drive Organic Light Emitting Diode 4 that each pixel arrangement 10 has a driver element 2, the negative electrode of this Organic Light Emitting Diode 4 is to be connected a positive supply 5, thereby provide voltage to improve the current potential of Organic Light Emitting Diode 4 by this positive supply 5, and then make driver element 2 at its Vsd (source electrode of when action, drain voltage is poor) reduce, and Vsg (source electrode, grid voltage is poor) then remain unchanged, then when each driver element 2 has different starting potential (Threshold Voltage) because of the characteristic variation, the difference of each driver element 2 its output current when conducting is dwindled.
For reaching above-mentioned method, pixel of the present invention (pixel) device 10 includes: a switch element 1, a driver element 2, a storage element 3 and an Organic Light Emitting Diode 4 constitute; Wherein,
Above-mentioned switch element 1 is a thin film transistor (TFT) (TFT), and 1 liang of input end of this switch element 11,12 respectively is connected with an one scan line 60 (Scan Line) and a data line 61 (Data Line) respectively;
This driver element 2 is a thin film transistor (TFT) (TFT), and the input end 21 of this driver element 2 is connected with a power lead 62 (Supply Line), and another input end 22 is connected to the output terminal 13 of switch element 1;
This storage element 3 is made of capacitor, and an end is connected with a power lead 62 (Supply Line), and the other end is connected the output terminal 13 of switch element 1;
The anode of this Organic Light Emitting Diode 4 is connected with the output terminal 23 of above-mentioned driver element 2, and its negative electrode then is connected to a positive supply 5;
The negative electrode and the anode potential that provide voltage to increase this Organic Light Emitting Diode 4 by this positive supply 5, and the current potential of the output terminal 23 of this driver element 2 of related raising, and then this driver element 2 is reduced at its Vsd of when action (source electrode, drain voltage poor), Vsg (source electrode, grid voltage poor) then remains unchanged, then as each driver element 2 starting potential (Threshold Voltage different because of characteristic variations has; Vth) time, the difference of each driver element 2 its output current when conducting is dwindled.
In addition, being fully to understand the effect that this case reached, seeing also shown in Figure 2ly, is the current-voltage synoptic diagram of driver element.As shown in the figure: when the input voltage Vdd of power lead 62 is that 13V and the input voltage signal of data line 61 are when being 0V, under the known pixels apparatus structure, driver element 2 has a known load curve 71, so on the Vsd working point of known drive unit (Operating Point) intersection point when being the family curve 1 that is located in known load curve 71 and driver element 2 (when the input voltage (Vdd) of power lead is 0V for the input voltage signal (Vdata) of 13V data line).
Suppose starting potential (the Threshold Voltage of TFT element; Vth) because of processing procedure restriction has ± variation of 1.5V, by can find among the figure when Vth have-during the variation of 1.5V, will cause the output current that has driver element that 23.3% variation is arranged.
Otherwise, when using pixel arrangement 10 of the present invention, when the cathode potential of supposing Organic Light Emitting Diode (OLED) provides voltage that the 5V size is arranged because of positive supply, this driver element 2 has a load curve 73 of the present invention, so the Vsd working point (OperatingPoint) of driver element 2 is to be located on the intersection point of load curve 73 of the present invention and the family curve 1 of driver element 2, then the starting potential (Vth) of TFT element equally because of the processing procedure restriction have-during the variation of 1.5V, through experiment confirm, the output current of its driver element 2 then only has 13.6% variation.
Seeing also shown in Figure 3ly again, is the current-voltage synoptic diagram (two) of driver element.As shown in the figure: (this family curve is that the input voltage (Vdd) when power lead 62 is 8V when family curve 3 83, and the input voltage signal (Vdata) of data line 61 is when being 0V), under the conventional pixel apparatus structure, the Vsg of its conventional ADS driving unit diminishes and is 8V, and the Vsd working point of conventional ADS driving unit (Operating Point) is located on the intersection point of load curve 2 81 and the family curve 3 83 (Vsg=8V) of driver element 2.Then the starting potential Vth of TFT element (Threshold Voltage) because of processing procedure restriction have ± during the variation of 1.5V, the output current that causes the conventional ADS driving unit had 39.6% variation.
But, when using drive unit of the present invention, because Organic Light Emitting Diode (OLED) panel common cathode current potential equals 5V, so input voltage (Vdd) is 13V, the input voltage signal (Vdata) of data line 61 is 0V, and the Vsd working point of driver element 2 (Operating Point) is located on the intersection point of load curve 2 81 and conventional ADS driving element characteristics curve 2 82 (Vsg=13V).Then the starting potential Vth of TFT element (Threshold Voltage) because of processing procedure restriction have ± during the variation of 1.5V, the output current of this driver element 2 has only 13.6% variation.
Thereby, the conventional pixel device is supplied voltage (Vdd) when diminishing at power supply, though the Vsd of conventional ADS driving unit is diminished, but also cause Vsg to diminish simultaneously, make the output current of each conventional ADS driving unit be subjected to the influence of characteristic variations to become big on the contrary, and can't also keep its Vsg at certain value simultaneously at the Vsd that reduces driver element 2 as the present invention, so can make TFT when conducting (ON), the output current size is not subjected to the characteristic variations of TFT and influences.
Above-mentioned is preferred embodiment of the present invention only, is not to be used for limiting scope of the invention process.Be that all equalizations of being done according to the present patent application claim change and modification, be all claim of the present invention and contain.
Claims (5)
1. a positive type organic light emitting diode display image installs uniformly, and described display is made of a plurality of pixel arrangements (10), it is characterized in that described each pixel arrangement (10) comprising:
One switch element (1) has two input ends (11), (12) and an output terminal (13) on it, described two input ends (11), (12) connect sweep trace (60) and data line (61) respectively;
One storage element (3), end is connected with a power lead (62) on it, and the other end then is connected in the output terminal (13) of described switch element (1);
One driver element (2) has two input ends (21), (22) and an output terminal (23) on it, a described input end (21) is connected with a power lead (62), and described another input end (22) then is connected to the output terminal (13) of described switch element (1);
One Organic Light Emitting Diode (4) has an anode and a negative electrode on it, described anode is connected to the described output terminal (23) of described driver element (2), and described negative electrode then is connected to a positive supply (5);
The described negative electrode and the described anode potential that provide voltage to increase described Organic Light Emitting Diode (4) by described positive supply (5), and the current potential of the described output terminal (23) of the described driver element of related raising (2), and then described driver element (2) its source electrode, drain voltage difference when action are reduced, source electrode, grid voltage difference then remain unchanged.
2. positive type organic light emitting diode display image according to claim 1 installs uniformly, it is characterized in that, described switch element (1) can be a thin film transistor (TFT).
3. positive type organic light emitting diode display image according to claim 1 installs uniformly, it is characterized in that, described driver element (2) can be a thin film transistor (TFT).
4. positive type organic light emitting diode display image according to claim 1 installs uniformly, it is characterized in that, described storage element (3) is made of capacitor.
5. positive type organic light emitting diode display image uniform method, described display mainly is made up of many groups pixel arrangement, it is characterized in that, it is shinny to drive described Organic Light Emitting Diode (4) that each described pixel arrangement (10) has a driver element (2), the negative electrode of described Organic Light Emitting Diode (4) is to be connected a positive supply (5), provide voltage to improve the current potential of Organic Light Emitting Diode (4) by described positive supply (5), and then make described driver element (2) at its source electrode of when action, the drain voltage difference reduces, and source electrode, the grid voltage difference then remains unchanged, then when each described driver element (2) has different starting potentials because of the characteristic variation, each described driver element (2) difference of its output current when conducting is dwindled.
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| Application Number | Priority Date | Filing Date | Title |
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| CNB031091032A CN1312650C (en) | 2003-04-03 | 2003-04-03 | Method and device capable of making active organic light-emitting diode display produce uniform image |
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| CNB031091032A CN1312650C (en) | 2003-04-03 | 2003-04-03 | Method and device capable of making active organic light-emitting diode display produce uniform image |
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| CN1536550A CN1536550A (en) | 2004-10-13 |
| CN1312650C true CN1312650C (en) | 2007-04-25 |
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| CNB031091032A Expired - Fee Related CN1312650C (en) | 2003-04-03 | 2003-04-03 | Method and device capable of making active organic light-emitting diode display produce uniform image |
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| CN105118425A (en) * | 2015-10-14 | 2015-12-02 | 京东方科技集团股份有限公司 | Display panel and display control method thereof as well as display device |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5684365A (en) * | 1994-12-14 | 1997-11-04 | Eastman Kodak Company | TFT-el display panel using organic electroluminescent media |
| US5714968A (en) * | 1994-08-09 | 1998-02-03 | Nec Corporation | Current-dependent light-emitting element drive circuit for use in active matrix display device |
| CN1341915A (en) * | 2000-07-31 | 2002-03-27 | 三洋电机株式会社 | Active matrix self-luminous display device and active matrix organic EL display device |
| CN1369870A (en) * | 2001-02-08 | 2002-09-18 | 株式会社半导体能源研究所 | Light-emitting element and electronic appliance using such element |
| CN1369916A (en) * | 2001-01-29 | 2002-09-18 | 株式会社半导体能源研究所 | Light-emitting element |
| US20020180679A1 (en) * | 2001-02-23 | 2002-12-05 | Hiroshi Kageyama | Drive circuit and image display apparatus |
| JP2002358031A (en) * | 2001-06-01 | 2002-12-13 | Semiconductor Energy Lab Co Ltd | Light emitting device and its driving method |
-
2003
- 2003-04-03 CN CNB031091032A patent/CN1312650C/en not_active Expired - Fee Related
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5714968A (en) * | 1994-08-09 | 1998-02-03 | Nec Corporation | Current-dependent light-emitting element drive circuit for use in active matrix display device |
| US5684365A (en) * | 1994-12-14 | 1997-11-04 | Eastman Kodak Company | TFT-el display panel using organic electroluminescent media |
| CN1341915A (en) * | 2000-07-31 | 2002-03-27 | 三洋电机株式会社 | Active matrix self-luminous display device and active matrix organic EL display device |
| CN1369916A (en) * | 2001-01-29 | 2002-09-18 | 株式会社半导体能源研究所 | Light-emitting element |
| CN1369870A (en) * | 2001-02-08 | 2002-09-18 | 株式会社半导体能源研究所 | Light-emitting element and electronic appliance using such element |
| US20020180679A1 (en) * | 2001-02-23 | 2002-12-05 | Hiroshi Kageyama | Drive circuit and image display apparatus |
| JP2002358031A (en) * | 2001-06-01 | 2002-12-13 | Semiconductor Energy Lab Co Ltd | Light emitting device and its driving method |
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