CN1329880C - Active matrix organic light-emitting diode circuit capable of automatically adjusting cathode voltage and its automatic adjustment method - Google Patents
Active matrix organic light-emitting diode circuit capable of automatically adjusting cathode voltage and its automatic adjustment method Download PDFInfo
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- CN1329880C CN1329880C CNB031211038A CN03121103A CN1329880C CN 1329880 C CN1329880 C CN 1329880C CN B031211038 A CNB031211038 A CN B031211038A CN 03121103 A CN03121103 A CN 03121103A CN 1329880 C CN1329880 C CN 1329880C
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- 229920001621 AMOLED Polymers 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title claims abstract description 12
- 239000010409 thin film Substances 0.000 description 14
- 239000010408 film Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000000630 rising effect Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
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Abstract
An active matrix organic light emitting diode circuit capable of automatically adjusting cathode voltage and an automatic adjusting method thereof apply a resistor to sense current flowing through a cathode terminal of an Organic Light Emitting Diode (OLED) and automatically adjust voltage supplied to the cathode terminal of the OLED by a digital processing circuit so as to maintain the stability of the current flowing through the cathode terminal of the OLED.
Description
Technical field
The present invention relates to a kind of active matrix organic light-emitting diode circuit, and be particularly related to a kind of active matrix organic light-emitting diode circuit and the Automatic adjustment method thereof that can regulate cathode voltage automatically.
Background technology
Along with the prosperity of Information technology, of all kinds as information equipments such as computing machine, mobile phone, PDA(Personal Digital Assistant) and digital cameras, all constantly weed out the old and bring forth the new.In these information equipments, display is being played the part of critical role all the time, and flat-panel screens (FlatPanel Display) is little by little to receive an acclaim owing to have the characteristic of slimming, lightweight and power saving.
In various flat-panel screens, active matrix organic light-emitting diode (Active MatrixOrganic Emitting Diode, being called for short AMOLED) visual angle is wide, color contrast is effective because of having for display, frivolous, response speed reaches low cost and other advantages soon, so be very suitable for as portable terminal (notebook computer, PDA, mobile phone etc.), particularly large-scale display device such as TV, monitor etc.
Yet, because thin film transistor (TFT) (the Thin Film Transistor of the driving circuit of active matrix organic light-emitting diode (AMOLED), be called for short TFT), be activated the pressurization of circuit capacitance for a long time, so that cause the critical voltage Vth of thin film transistor (TFT) to rise, shown in the curve map of Fig. 1 along with the time.And the electric current I d of the Organic Light Emitting Diode of flowing through (OLED) generally is shown below:
Id＝(1/2)k(Vgs-Vth)(Vgs-Vth)……….(1)
The old friend, the electric current I d of the Organic Light Emitting Diode of flowing through (OLED) also can be along with the rising of the critical voltage Vth of thin film transistor (TFT) and descend, and has caused influencing the performance of Organic Light Emitting Diode (OLED) assembly brightness, and then has influenced the operation lifetime of assembly.
Summary of the invention
The invention provides a kind of active matrix organic light-emitting diode circuit and the Automatic adjustment method thereof that can regulate cathode voltage automatically, it can be by the electric current of senses flow through Organic Light Emitting Diode (OLED) cathode terminal, automatically regulate the voltage that is supplied with OLED (OLED) cathode terminal, stable with the electric current of keeping the Organic Light Emitting Diode of flowing through (OLED) cathode terminal.
For reaching above-mentioned and other purpose, the invention provides a kind of active matrix organic light-emitting diode circuit that can regulate cathode voltage automatically.This circuit comprises: active matrix organic light-emitting diode display board and cathode voltage auto-adjusting circuit.Wherein, the active matrix organic light-emitting diode display board has an Organic Light Emitting Diode (OLED) cathode terminal, the cathode voltage auto-adjusting circuit then is coupled with OLED (OLED) cathode terminal, electric current in order to sensing Organic Light Emitting Diode (OLED) cathode terminal, and according to the size of the electric current of Organic Light Emitting Diode (OLED) cathode terminal, automatically regulate the voltage that is supplied with OLED (OLED) cathode terminal, stable with the electric current of keeping the Organic Light Emitting Diode of flowing through (OLED) cathode terminal.
In the preferred embodiment of the present invention, its cathode voltage auto-adjusting circuit comprises: resistance, subtraction circuit, comparator circuit and digital processing circuit.Wherein, resistance is used for the electric current according to Organic Light Emitting Diode (OLED) cathode terminal, comes sensing to produce a sensing voltage.Subtraction circuit couples resistance, in order to ask for sensing voltage and to be supplied with voltage difference between the voltage of OLED (OLED) cathode terminal.Comparator circuit is in order to make comparisons above-mentioned voltage difference and reference voltage, with the output control signal.Digital processing circuit then couples comparator circuit, is used for according to control signal, regulates the voltage that is supplied with OLED (OLED) cathode terminal automatically, stable with the electric current of keeping the Organic Light Emitting Diode of flowing through (OLED) cathode terminal.
In one embodiment, the resistance of use is resistance less than 10 ohm resistance.
In one embodiment, the reference voltage of use is to calculate and get according to the standard value of the electric current of Organic Light Emitting Diode (OLED) cathode terminal.
The present invention provides a kind of cathode voltage Automatic adjustment method that can regulate the active matrix organic light-emitting diode circuit of cathode voltage automatically in addition, and it is applicable to the active matrix organic light-emitting diode display board with an Organic Light Emitting Diode (OLED) cathode terminal.The method comprises the following steps: the at first electric current of sensing Organic Light Emitting Diode (OLED) cathode terminal; According to the size of the electric current of the Organic Light Emitting Diode cathode terminal (OLED) of sensing, regulate the voltage that is supplied with OLED (OLED) cathode terminal automatically then, stable with the electric current of keeping the Organic Light Emitting Diode of flowing through (OLED) cathode terminal.
By in the above-mentioned explanation as can be known, use a kind of active matrix organic light-emitting diode circuit and the Automatic adjustment method thereof that can regulate cathode voltage automatically provided by the present invention, cause can be by the electric current of senses flow through Organic Light Emitting Diode (OLED) cathode terminal, automatically regulate the voltage that is supplied with OLED (OLED) cathode terminal, so can keep electric current stable of the Organic Light Emitting Diode of flowing through (OLED) cathode terminal.
For above and other objects of the present invention, feature, advantage can be become apparent, hereinafter special with preferred embodiment, and conjunction with figs., be described in detail below:
Description of drawings
Fig. 1 is the critical voltage upcurve figure of thin film transistor (TFT);
Fig. 2 is the pixel drive synoptic diagram of active matrix organic light-emitting diode display board;
Fig. 3 is the active matrix organic light-emitting diode circuit diagram that can regulate cathode voltage automatically of the preferred embodiment according to the present invention.
Description of reference numerals is as follows:
210 the first film transistors
220 second thin film transistor (TFT)s
230 electric capacity
240 Organic Light Emitting Diodes
241,311 Organic Light Emitting Diode cathode terminals
310 active matrix organic light-emitting diode display boards
320 resistance
330 subtraction circuits
340 comparator circuits
350 digital processing circuits
390 cathode voltage auto-adjusting circuits
Embodiment
Please refer to shown in Figure 2ly, it is the pixel drive synoptic diagram of active matrix organic light-emitting diode (AMOLED) display board (Panel).Show among the figure that the pixel of this active matrix organic light-emitting diode (AMOLED) display board comprises: the first film transistor 210, second thin film transistor (TFT) 220, electric capacity 230 and Organic Light Emitting Diode (OLED) 240.Its coupling mode is that grid connection sweep trace, the drain electrode of the first film transistor 210 connects data line, source electrode then connects an end of electric capacity 230 and the grid of second thin film transistor (TFT) 220, the drain electrode of second thin film transistor (TFT) 220 connects positive source V+, source electrode connects an end of electric capacity 230 and the anode tap of Organic Light Emitting Diode (OLED) 240, and 241 of the cathode terminals of Organic Light Emitting Diode (OLED) 240 are connected to power cathode Vss usually.
As previously mentioned, the display brightness of Organic Light Emitting Diode (OLED) 240 is directly proportional with the electric current I d of the Organic Light Emitting Diode of flowing through (OLED) 240, shown in the electric current I d of organic light emission two diodes (OLED) 240 of flowing through then calculates suc as formula (1).When sweep trace scans so far pixel, can conducting the first film transistor 210, be sent to the grid of second thin film transistor (TFT) 220 with voltage with data line, obtain grid voltage Vg.The forward voltage of supposing Organic Light Emitting Diode (OLED) 240 is Voled, and then the gate source voltage Vgs of second thin film transistor (TFT) 220 is:
Vgs＝Vg-Vs＝Vg-(Vss+Voled)
Because the critical voltage Vth of second thin film transistor (TFT) 220 is known, thus by the calculating formula of formula (1), and can comply with required display brightness, come the magnitude of voltage of transmit data line.
Yet, critical voltage Vth when second thin film transistor (TFT) 220, when rising along with the increase of running time as shown in Figure 1, significantly, by the calculating formula of formula (1) as can be known, the magnitude of voltage that transmits according to data line, the electric current I d of the Organic Light Emitting Diode of flowing through (OLED) that calculates and obtain, also can be and descend along with the rising of the critical voltage Vth of thin film transistor (TFT), cause influencing the performance of Organic Light Emitting Diode (OLED) assembly brightness, and then also influenced the operation lifetime of assembly.
Therefore, as shown in Figure 3, Organic Light Emitting Diode (OLED) cathode terminal 311 of the active matrix organic light-emitting diode of present embodiment (AMOLED) display board 310, be connected to a cathode voltage auto-adjusting circuit 390, so that electric current that can sensing Organic Light Emitting Diode (OLED) cathode terminal 311, and according to the size of the electric current of Organic Light Emitting Diode (OLED) cathode terminal 311, automatically regulate the voltage Vss that is supplied with OLED (OLED) cathode terminal 311, stable with the electric current of keeping the Organic Light Emitting Diode of flowing through (OLED) cathode terminal 311.
As shown in the figure, cathode voltage auto-adjusting circuit 390 comprises: resistance 320, subtraction circuit 330, comparator circuit 340 and digital processing circuit 350.Wherein, resistance 320 meetings are according to the electric current of Organic Light Emitting Diode (OLED) cathode terminal 311, and sensing produces a sensing voltage Va.330 of subtraction circuits can be asked for sensing voltage Va and be supplied with voltage difference between the voltage Vss of OLED (OLED) cathode terminal.This voltage difference Va-Vss will be sent to comparator circuit 340, and 340 reference voltage Vref with this voltage difference Va-Vss and setting of comparator circuit are made comparisons, and export control signal according to result relatively.This control signal enters digital processing circuit 350 among the figure with transmission, digital processing circuit 350 is just according to this control signal, automatically regulate the voltage Vss that is supplied with OLED (OLED) cathode terminal, stable with the electric current of keeping the Organic Light Emitting Diode of flowing through (OLED) cathode terminal.That is to say, downgrade the voltage Vss of Organic Light Emitting Diode (OLED) cathode terminal if electric current is too low, otherwise, then increase the voltage Vss of Organic Light Emitting Diode (OLED) cathode terminal.
Wherein, in order to reduce the influence of resistance 320 for driving circuit, the resistance of the resistance 320 of use should be as much as possible little, for example uses resistance less than 10 ohm resistance 320.And the reference voltage Vref of using, be to calculate and get according to the standard value of the electric current of Organic Light Emitting Diode (OLED) cathode terminal 311, so that can be according to the electric current of the Organic Light Emitting Diode of flowing through (OLED) cathode terminal, automatically regulate the voltage Vss that is supplied with OLED (OLED) cathode terminal, stable with the electric current of keeping the Organic Light Emitting Diode of flowing through (OLED) cathode terminal.
In above-mentioned explanation, can conclude the cathode voltage Automatic adjustment method of a kind of active matrix organic light-emitting diode (AMOLED) circuit, it is applicable to the active matrix organic light-emitting diode display board with an Organic Light Emitting Diode (OLED) cathode terminal.The method comprises the following steps: the at first electric current of sensing Organic Light Emitting Diode (OLED) cathode terminal; According to the size of the electric current of the Organic Light Emitting Diode cathode terminal (OLED) of sensing, regulate the voltage that is supplied with OLED (OLED) cathode terminal automatically then, stable with the electric current of keeping the Organic Light Emitting Diode of flowing through (OLED) cathode terminal.
In sum, the present invention has following advantage at least:
1. can regulate the voltage that is supplied with OLED (OLED) cathode terminal automatically, stable with the electric current of keeping the Organic Light Emitting Diode of flowing through (OLED) cathode terminal.
2. can prolong the operation lifetime of assembly.
Though the present invention discloses as above with preferred embodiment; so it is not to be used to limit the present invention, any those of ordinary skills, without departing from the spirit and scope of the present invention; can do various changes and retouching, so protection scope of the present invention is as the criterion with the scope that claims define.
Claims (5)
1. the active matrix organic light-emitting diode circuit that can regulate cathode voltage automatically is characterized in that this circuit comprises:
One active matrix organic light-emitting diode display board has an Organic Light Emitting Diode cathode terminal; And
One cathode voltage auto-adjusting circuit, couple this Organic Light Emitting Diode cathode terminal, electric current in order to this Organic Light Emitting Diode cathode terminal of sensing, and according to the size of the electric current of this Organic Light Emitting Diode cathode terminal, automatically regulate the voltage of this Organic Light Emitting Diode cathode terminal of supply, wherein this cathode voltage auto-adjusting circuit is made comparisons the electric current and a normative reference of this Organic Light Emitting Diode cathode terminal, selects to increase or downgrade the voltage of this organic light emitting diode cathode terminal.
2. the active matrix organic light-emitting diode circuit that can regulate cathode voltage automatically as claimed in claim 1 is characterized in that, described cathode voltage auto-adjusting circuit comprises:
One resistance is used for producing a sensing voltage according to the current sense of this Organic Light Emitting Diode cathode terminal;
One subtraction circuit couples this resistance, the voltage difference between the voltage that is used to ask for this sensing voltage and supply this Organic Light Emitting Diode cathode terminal;
One comparator circuit is used for this voltage difference and a reference voltage are made comparisons, to export a control signal; And
One digital processing circuit couples this comparator circuit, is used for according to this control signal, regulates the voltage of this Organic Light Emitting Diode cathode terminal of supply automatically.
3. the active matrix organic light-emitting diode circuit that can regulate cathode voltage automatically as claimed in claim 2, it is characterized in that: the resistance of described resistance is less than 10 ohm.
4. the active matrix organic light-emitting diode circuit that can regulate cathode voltage automatically as claimed in claim 2 is characterized in that: described reference voltage calculates and gets according to the standard value of the electric current of this Organic Light Emitting Diode cathode terminal.
5. the cathode voltage Automatic adjustment method that can regulate the active matrix organic light-emitting diode circuit of cathode voltage automatically, be applicable to active matrix organic light-emitting diode display board with an Organic Light Emitting Diode cathode terminal, it is characterized in that this method comprises the following steps:
The electric current of this Organic Light Emitting Diode cathode terminal of sensing; And
According to the size of the electric current of this Organic Light Emitting Diode cathode terminal, regulate the voltage of this Organic Light Emitting Diode cathode terminal of supply automatically.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031211038A CN1329880C (en) | 2003-03-21 | 2003-03-21 | Active matrix organic light-emitting diode circuit capable of automatically adjusting cathode voltage and its automatic adjustment method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031211038A CN1329880C (en) | 2003-03-21 | 2003-03-21 | Active matrix organic light-emitting diode circuit capable of automatically adjusting cathode voltage and its automatic adjustment method |
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| CN1532793A CN1532793A (en) | 2004-09-29 |
| CN1329880C true CN1329880C (en) | 2007-08-01 |
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| CNB031211038A Expired - Lifetime CN1329880C (en) | 2003-03-21 | 2003-03-21 | Active matrix organic light-emitting diode circuit capable of automatically adjusting cathode voltage and its automatic adjustment method |
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Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100392713C (en) * | 2005-03-11 | 2008-06-04 | 友达光电股份有限公司 | Brightness adjusting circuit and electroluminescent display using the same |
| CN100446631C (en) * | 2006-04-30 | 2008-12-24 | 友达光电股份有限公司 | Brightness adjusting circuit and electroluminescent display using the same |
| CN109992147B (en) * | 2017-12-29 | 2022-10-11 | 上海和辉光电股份有限公司 | Control method and device for cathode voltage of OLED display module |
| CN108877660B (en) * | 2018-08-06 | 2020-11-27 | 京东方科技集团股份有限公司 | Driving circuit, display device and driving method of display device |
| CN109215580B (en) * | 2018-09-18 | 2020-05-05 | 昆山国显光电有限公司 | Pixel circuit structure and driving method thereof |
Citations (8)
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| JPH10319910A (en) * | 1997-05-15 | 1998-12-04 | Tdk Corp | Driving device for organic display device |
| US6239716B1 (en) * | 1998-06-25 | 2001-05-29 | Hewlett Packard-Company | Optical display device and method of operating an optical display device |
| CN1339772A (en) * | 2001-10-12 | 2002-03-13 | 清华大学 | Driving method and driving circuit for grey display of organic electroluminescent display device |
| CN1364285A (en) * | 2000-03-14 | 2002-08-14 | 皇家菲利浦电子有限公司 | Electroluminescent display device with luminance correction in dependence on age and ambient light |
| CN1369916A (en) * | 2001-01-29 | 2002-09-18 | 株式会社半导体能源研究所 | Light-emitting element |
| CN1372240A (en) * | 2001-02-26 | 2002-10-02 | 三洋电机株式会社 | Indicator |
| CN1397058A (en) * | 2000-09-28 | 2003-02-12 | 精工爱普生株式会社 | Display device, method of driving the same, and electronic apparatus |
| CN1400578A (en) * | 2001-07-30 | 2003-03-05 | 先锋株式会社 | Display equipment with brightness regulating function |
-
2003
- 2003-03-21 CN CNB031211038A patent/CN1329880C/en not_active Expired - Lifetime
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10319910A (en) * | 1997-05-15 | 1998-12-04 | Tdk Corp | Driving device for organic display device |
| US6239716B1 (en) * | 1998-06-25 | 2001-05-29 | Hewlett Packard-Company | Optical display device and method of operating an optical display device |
| CN1364285A (en) * | 2000-03-14 | 2002-08-14 | 皇家菲利浦电子有限公司 | Electroluminescent display device with luminance correction in dependence on age and ambient light |
| CN1397058A (en) * | 2000-09-28 | 2003-02-12 | 精工爱普生株式会社 | Display device, method of driving the same, and electronic apparatus |
| CN1369916A (en) * | 2001-01-29 | 2002-09-18 | 株式会社半导体能源研究所 | Light-emitting element |
| CN1372240A (en) * | 2001-02-26 | 2002-10-02 | 三洋电机株式会社 | Indicator |
| CN1400578A (en) * | 2001-07-30 | 2003-03-05 | 先锋株式会社 | Display equipment with brightness regulating function |
| CN1339772A (en) * | 2001-10-12 | 2002-03-13 | 清华大学 | Driving method and driving circuit for grey display of organic electroluminescent display device |
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| CN1532793A (en) | 2004-09-29 |
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Granted publication date: 20070801 |