CN1241163C - Display driving process - Google Patents
Display driving process Download PDFInfo
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- CN1241163C CN1241163C CNB021224978A CN02122497A CN1241163C CN 1241163 C CN1241163 C CN 1241163C CN B021224978 A CNB021224978 A CN B021224978A CN 02122497 A CN02122497 A CN 02122497A CN 1241163 C CN1241163 C CN 1241163C
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- voltage
- display
- driving method
- picture
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Abstract
The present invention relates to a driving method for a display. The driving method uses a voltage driving circuit in the display of an organic light emitting diode. During the period of a frame, a data voltage is set into a data voltage with a negative value which can maintain for a set time. When a scanning voltage is set into a high voltage value, the data voltage with the negative value is supplied to a grid electrode of a driving thin film transistor, and the grid electrode maintains the voltage with the negative value of the grid electrode for a holding time. The threshold voltage for driving the thin film transistor can not be changed. Therefore, after the organic light emitting diode is used for a long time, the original brightness can be maintained, and the service life of the display can be effectively extended.
Description
Technical field
The present invention relates to a kind of driving method of display.
Background technology
The human dynamic image that can see the earliest is the film of documentary film form.Afterwards, the invention of cathode-ray tube (CRT) (Cathode Ray Tube is called for short CRT) successfully derives business-like televisor, and becomes the electrical home appliances of each family's indispensability.Along with development of science and technology, the application of CRT expands to the both desktop monitors in the computer industry again, and makes CRT scene many decades nearly.But the made all types of displays of CRT all face the problem of radiant rays, and because the structure of internal electron rifle, and make that display is bulky and take up space, so be unfavorable for thin type and lightweight.
Since above-mentioned problem, and make the researchist start to develop so-called flat-panel screens (Flat Panel Display).This field comprises LCD (Liquid Crystal Display, abbreviation LCD), Field Emission Display (Field Emission Display, abbreviation FED), organic LED (Organic Light Emitting Diode, be called for short OLED) and plasma scope (Plasma Display Panel is called for short PDP).
Wherein, organic LED is called display of organic electroluminescence (OrganicElectroluminescence Display is called for short OELD) again, and it is the element of self-luminosity.Because the characteristic of OLED is DC low-voltage driving, high brightness, high-level efficiency, high correlative value and frivolous, and its luminous color and luster is by red (Red, abbreviation R), green (Green, be called for short G) and blue (Blue, being called for short B) three primary colors are to white degree of freedom height, so OLED is called the development priority of the novel planar panel in next epoch.The OLED technology is except having the frivolous and high resolving power of LCD concurrently, and the active illuminating of LED, response speed is fast with advantage such as power saving cold light source outside, multiple advantages such as the visual angle is wide in addition, color contrast is effective and cost is low.Therefore, OLED can be widely used in backlight, mobile phone, digital camera and the PDA(Personal Digital Assistant) etc. of LCD or indication billboard.
From the viewpoint of type of drive, OLED can be divided into passive-matrix (Passive Matrix) type of drive and active-matrix (Active Matrix) type of drive two big kinds.The advantage of passive matrix type OLED is that structure very simply and not needs to use thin film transistor (TFT) (Thin FilmTransistor, be called for short TFT) drive, thereby cost is lower, but its shortcoming is the application that is not suitable for the high resolving power image quality, and, can produce that power consumption increases, component life reduces and problem that display performance is good etc. when large size panel develops.And the advantage of active-matrix formula OLED is except the demand that can be applicable to large-sized active matrix drive mode, and its visual angle is wide, high brightness and the fast characteristic of response speed also are very important, but its cost can be slightly higher than passive matrix type OLED.
According to the difference of type of drive, flat-panel screens can be divided into two kinds of voltage driven type and current drive-types again.Voltage driven type is applied in TFT-LCD usually, also just imports different voltage to data line, and reaches different GTGs, to reach full-color purpose.The TFT-LCD of voltage driven type possess skills maturation, stable and cheap advantage.And current drive-type is applied in the display of OLED usually, just imports different electric currents to data line, and reaches different GTGs, to reach full-color purpose.But the mode of this current drives picture element needs exploitation new circuit and IC, therefore needs huge cost.Therefore, if come driving OLED, cost is greatly reduced with the Voltag driving circuit of TFT-LCD.But, when the Voltag driving circuit with TFT-LCD comes driving OLED, under long-term operation, can make the threshold voltage (Threshold Voltage) of drive TFT that the phenomenon of drift is arranged, and make threshold voltage rise.And TFT at the formula of the drain current of saturation region is: I
d=(1/2) * μ
n* C
Ox* (W/L) * (V
Gs-V
Th)
2, electronics mobility μ wherein
nAnd the grid capacitance C on the unit area
OxBe definite value, V
ThBe the threshold voltage of TFT, W is the channel width of TFT, and L is the channel length of TFT.Formula when threshold voltage rises, can make the drive current of flowing through between drain electrode and the source electrode of drive TFT reduce as can be known thus.Owing to drive current is to be used for driving OLED to make OLED luminous, so when drive current reduces, will the brightness of OLED be decreased.
For the purpose of clearer, please refer to Fig. 1, it illustrates is circuit diagram with a picture element in the display of voltage driving mode driving OLED.This picture element comprises Voltag driving circuit 102 and OLED (104).Above-mentioned Voltag driving circuit 102 comprises TFT1 (106), capacitor C (108) and TFT2 (110).Wherein, TFT2 (110) is called drive thin film transistors, is in order to produce the drive current of driving OLED (104), so that OLED (104) is luminous.The drain electrode of TFT1 (106) is coupled to data voltage (V
Data); The grid of TFT1 (106) is coupled to scanning voltage (V
Scan); The source electrode of TFT1 (106) is coupled to first end of capacitor C (108) and the grid of TFT2 (110).The drain electrode of TFT2 (110) is coupled to supply voltage (V
DD); The source electrode of TFT2 (110) is coupled to the positive pole of OLED (104), wherein supplies voltage (V
DD) be generally positive voltage, and provided by voltage source.Second end of capacitor C (108) is coupled to one and has current potential V
RefPower supply unit.And the negative pole of OLED (104) is coupled to ground.
And the V of the driving method of existing a kind of Voltag driving circuit 102
DD, V
Scan, V
Data, and the voltage (V of the grid of TFT2 (110)
2g) between sequential chart, please refer to Fig. 2 and illustrate.At first be noted that and work as V
ScanWhen being set in high-voltage value, TFT1 (104) can conducting.Work as V
ScanWhen being set in low voltage value, TFT1 (104) can close.In addition, be noted that V
ScanThe time that a high-voltage value and a low voltage value occur is called the time of a picture (Frame) (be among Fig. 2 illustrated T), the time of one of them picture, be generally 1/60 second, that is frequency is 60Hz, and picture will be formed the portrait of a picture element.As shown in Figure 2, when at V
ScanIn the time of during high-voltage value, V
DataBe high-voltage value, so always make V
2gMaintain positive voltage, and make V
2gRise gradually.V
2gThe result of Shang Shenging will cause the oxide layer of the grid of TFT2 (110) to accumulate more trapped charge gradually, then make the threshold voltage of TFT2 (110) produce drift, and threshold voltage is risen.Such result will make the drive current of flowing through between drain electrode and the source electrode of TFT2 (110) reduce, and therefore can make the brightness of OLED (104) reduce.
Summary of the invention
In view of this, the present invention proposes a kind of driving method that improves the threshold voltage drift of drive thin film transistors.The present invention is during a picture, is to keep the negative value data voltage of the schedule time with data voltage sets.And when scanning voltage is set in high-voltage value, the negative value data voltage will be supplied to the grid of drive thin film transistors, and make grid keep the negative value grid voltage of a retention time.This will make the oxide layer of the grid of drive thin film transistors discharge trapped charge, and the threshold voltage of drive thin film transistors can not risen.
For reaching above-mentioned and other purpose, the present invention proposes a kind of driving method of display.This driving method is the Voltag driving circuit that is used for the display of organic LED.This display comprises a plurality of picture elements, and the portrait of each picture element is made up of a picture (Frame), and this picture has original frequency.Being characterized as of this driving method: during this picture, be to keep the negative value data voltage of a schedule time with data voltage sets; And when scanning voltage is set in high-voltage value, the negative value data voltage will be supplied to the grid of drive thin film transistors, and make grid keep the negative value grid voltage of a retention time.
In an embodiment of the present invention, the schedule time can be adjusted.
In one embodiment of this invention, the retention time and the schedule time are inequality.And the frequency of picture can be greater than original frequency.
In another embodiment of the present invention, the retention time is identical with the schedule time.And the frequency of picture is identical with original frequency.
In an embodiment of the present invention, driving method of the present invention drive current that drive thin film transistors will be produced can not decayed.And this drive current is in order to driving organic LED, and makes organic LED luminous.
In an embodiment of the present invention, the drain electrode of drive thin film transistors is coupled to supply voltage.And supply voltage is to be provided by voltage source.
In an embodiment of the present invention, the source electrode of drive thin film transistors is coupled to the positive pole of organic LED.
In an embodiment of the present invention, the negative pole of organic LED is coupled to ground.
In sum, the present invention is during a picture, is to keep the negative value data voltage of a schedule time with data voltage sets.And when scanning voltage is set in high-voltage value, the negative value data voltage will be supplied to the grid of drive thin film transistors, and make grid keep the negative value grid voltage of a retention time.This will make the oxide layer of the grid of drive thin film transistors discharge trapped charge, and the threshold voltage of drive thin film transistors can not risen.Therefore, the present invention can make the brightness of organic LED after using for a long time, still keeps original brightness, so can effectively increase the serviceable life of display.
Description of drawings
For allowing above and other objects of the present invention, feature and advantage, can become apparent more, preferred embodiment cited below particularly, and conjunction with figs. are described below in detail:
Fig. 1 illustrates is circuit diagram with a picture element in the voltage driving mode driving OLED display;
That Fig. 2 illustrates is the V of the driving method of existing a kind of Voltag driving circuit
DD, V
Scan, V
Data, and V
2gBetween sequential chart;
Fig. 3 illustrates is V according to the driving method of a preferred embodiment of the present invention display
DD, V
Scan, V
Data, and V
2gBetween sequential chart; And
That Fig. 4 illustrates is the V of the driving method of the display of another preferred embodiment according to the present invention
DD, V
Scan, V
Data, and V
2gBetween sequential chart.
Symbol description among the figure:
10: picture element
102: Voltag driving circuit
104：OLED
106：TFT1
108: electric capacity
110：TFT2
Embodiment
Please referring again to Fig. 1, the driving method of display of the present invention is the Voltag driving circuit 102 that is used for Fig. 1, beneathly will do explanation to driving method of the present invention according to Fig. 1.
The driving method of display of the present invention is to be used for the OLED display.And according to the supply voltage (V of the driving method of the display of a preferred embodiment of the present invention
DD), scanning voltage (V
Scan), data voltage (V
Data) and the grid voltage (V of TFT2 (110)
2g) between sequential chart, please refer to Fig. 3 and illustrate.As shown in Figure 3, present embodiment is the frequency with a picture, is speeded by original 60Hz to be 120Hz.Just, shortened to 1/120 second by 1/60 second with the time of a picture.If so during a picture, work as V
ScanBe set at high-voltage value, and V
DataFor when the voltage, then during next picture, work as V
ScanWhen being set at high-voltage value, V
DataCan keep the negative value voltage of a schedule time, wherein this schedule time and V
ScanThe time that remains on high-voltage value is identical.Just every the time (1/120 second) of a picture, V
DataCan do mutual counter-rotating.
In the present embodiment, suppose during first picture, to work as V
ScanWhen being set at high-voltage value, V
DataBe to be set in positive voltage (for example being 5V).And the operating principle of present embodiment is during first picture, works as V
ScanWhen being set at high-voltage value, TFT1 (106) can conducting, on the occasion of V
DataCan be fed to the grid of TFT2 (110), and make V
2gKeep an image time (1/120 second) on the occasion of voltage (for example for 5V).At this moment can make the oxide layer accumulation trapped charge of the grid of TFT2 (110).During second picture, work as V
ScanWhen being set at high-voltage value, TFT1 (106) meeting conducting, the V of negative value
Data(for example be-5V) can be fed to the grid of TFT2 (110), and make V
2gKeep an image time (1/120 second) negative value voltage (for example for-5V).At this moment can make the oxide layer of the grid of TFT2 (110) discharge trapped charge.After picture during, will repeatedly carry out according to above-mentioned mode.
In the present embodiment, because during two image times (1/60 second), V
2gCan keep the negative value voltage of an image time (1/120 second), thus can make the oxide layer of the grid of TFT2 (110) discharge trapped charge, and the threshold voltage of TFT2 (110) can not be risen, and remain near the original threshold voltage.And TFT at the formula of the drain current of saturation region is: I
d=(1/2) * μ
n* C
Ox* (W/L) * (V
Gs-V
Th)
2, electronics mobility μ wherein
nAnd the grid capacitance C on the unit area
OxBe definite value, V
ThBe the threshold voltage of TFT, W is the channel width of TFT, and L is the channel length of TFT.Thus formula as can be known because the threshold voltage of TFT2 (110) can not rise, so the drive current of TFT2 (110) can not reduce.Therefore, can make OLED (104) under operating for a long time, still keep original brightness, and the life-span of display can be prolonged effectively.
And according to the present invention the supply voltage (V of the display drive method of another preferred embodiment
DD), scanning voltage (V
Scan), data voltage (V
Data) and the grid voltage (V of TFT2 (110)
2g) between sequential chart, please refer to Fig. 4 and illustrate.As shown in Figure 4, the frequency of a picture is identical with original 60Hz in the present embodiment.Just, still maintain 1/60 second with the time of a picture.Present embodiment is worked as V during each picture
ScanBe set in high-voltage value hold time to T (being illustrated) as Fig. 4 the time, V
DataCan keep a period of time T
1The negative value voltage of (illustrating) as Fig. 4, and keep a period of time T
2(illustrating) as Fig. 4 on the occasion of voltage.
And the operating principle of present embodiment is worked as V during an image time
ScanBe set at high-voltage value and in time T
1During the time, TFT1 (106) can conducting, the V of negative value
DataCan be fed to the grid of TFT2 (110), and make V
2gT holds time
1Negative value voltage.At this moment can make the oxide layer of TFT2 (110) grid discharge trapped charge.Work as V
ScanBe set at high-voltage value and in time T
2During the time, TFT1 (106) can conducting, on the occasion of V
DataCan be fed to the grid of TFT2 (110), and make V
2gKeep on the occasion of voltage, and be maintained to the V of next picture
ScanWhen being set at high-voltage value.At this moment can make the oxide layer accumulation trapped charge of TFT2 (110) grid.After picture during, will repeatedly carry out according to above-mentioned mode.
In the present embodiment, owing to during each picture, work as V
ScanWhen being set at high-voltage value, V
DataHas a period of time of keeping T
1Negative value voltage, so can make V
2gT can hold time
1Negative value voltage.Therefore, can make the oxide layer of the grid of TFT2 (110) discharge trapped charge, and the threshold voltage of TFT2 (110) can not be risen, so the threshold voltage of TFT2 (110) is remained near the original threshold voltage.And TFT at the formula of the drain current of saturation region is: I
d=(1/2) * μ
n* C
Ox* (W/L) * (V
Gs-V
Th)
2, electronics mobility μ wherein
nAnd the grid capacitance C on the unit area
OxBe definite value, V
ThBe the threshold voltage of TFT, W is the channel width of TFT, and L is the channel length of TFT.Thus formula as can be known because the threshold voltage of TFT2 (110) can not rise, so the drive current of TFT2 (110) can not reduce.Therefore, can make OLED (104) under operating for a long time, still keep original brightness, and the life-span of display can be prolonged effectively.
In addition, the embodiment of comparison diagram 3 and Fig. 4 as can be known because in the embodiments of figure 3, V
2gThe time of keeping negative value voltage is longer, so can make the oxide layer of TFT2 (110) grid discharge more trapped charge, the effect of threshold voltage drift of therefore improving TFT2 (110) is better, but frame frequency need rise to two times of original frame frequency.
In sum, the present invention is during a picture (Frame), is to keep the negative value data voltage of a schedule time with data voltage sets.And when scanning voltage is set in high-voltage value, the negative value data voltage will be supplied to the grid of drive thin film transistors, and make grid keep the negative value grid voltage of a retention time.This will make the oxide layer of the grid of drive thin film transistors discharge trapped charge, and the threshold voltage of drive thin film transistors can not risen.Therefore, the present invention can make the brightness of organic LED after using for a long time, still keeps original brightness, so can effectively increase the serviceable life of display.
Though the present invention is exposed in preferred embodiment; right its is not in order to limit the present invention; any those skilled in the art; without departing from the spirit and scope of the present invention; when can being used for a variety of modifications and variations, thus protection scope of the present invention with claims and in conjunction with instructions and accompanying drawing the person of being defined be as the criterion.
Claims (11)
1. the driving method of display, this driving method is a Voltag driving circuit that is used for a display of an organic LED, and this display comprises a plurality of picture elements, and the portrait of each these picture element is made up of a picture, this picture has an original frequency, it is characterized in that:
During this picture, be to keep the negative value data voltage of the schedule time with data voltage sets; And
When scanning voltage is set in high-voltage value, this negative value data voltage will be supplied to the grid of a drive thin film transistors, and make this grid keep the negative value grid voltage of retention time.
2. the driving method of display as claimed in claim 1, it is characterized in that: this schedule time can be adjusted.
3. the driving method of display as claimed in claim 1, it is characterized in that: this retention time and this schedule time are inequality.
4. the driving method of display as claimed in claim 3, it is characterized in that: the frequency of this picture is greater than this original frequency.
5. the driving method of display as claimed in claim 1, it is characterized in that: this retention time is identical with this schedule time.
6. the driving method of display as claimed in claim 5, it is characterized in that: the frequency of this picture is identical with this original frequency.
7. the driving method of display as claimed in claim 1, it is characterized in that: the drive current that this driving method will make this drive thin film transistors produce can not decayed.
8. the driving method of display as claimed in claim 1 is characterized in that: the drain electrode of this drive thin film transistors is coupled to a supply voltage.
9. the driving method of display as claimed in claim 8, it is characterized in that: this supply voltage is to be provided by a voltage source.
10. the driving method of display as claimed in claim 1, it is characterized in that: the source electrode of this drive thin film transistors is coupled to the positive pole of this organic LED.
11. the driving method of display as claimed in claim 1 is characterized in that: the negative pole of this organic LED is coupled to ground.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021224978A CN1241163C (en) | 2002-06-04 | 2002-06-04 | Display driving process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021224978A CN1241163C (en) | 2002-06-04 | 2002-06-04 | Display driving process |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1464497A CN1464497A (en) | 2003-12-31 |
| CN1241163C true CN1241163C (en) | 2006-02-08 |
Family
ID=29743248
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB021224978A Expired - Lifetime CN1241163C (en) | 2002-06-04 | 2002-06-04 | Display driving process |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1241163C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4111185B2 (en) * | 2004-10-19 | 2008-07-02 | セイコーエプソン株式会社 | Electro-optical device, driving method thereof, and electronic apparatus |
| JP4988603B2 (en) * | 2005-02-10 | 2012-08-01 | トムソン ライセンシング | Image display device and method for controlling the same |
| KR101338312B1 (en) * | 2008-04-30 | 2013-12-09 | 엘지디스플레이 주식회사 | Organic electroluminescent display device and driving method thereof |
-
2002
- 2002-06-04 CN CNB021224978A patent/CN1241163C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CN1464497A (en) | 2003-12-31 |
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Granted publication date: 20060208 |
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