CN100375140C - Driving circuit having electro photoluminescence display - Google Patents
Driving circuit having electro photoluminescence display Download PDFInfo
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- CN100375140C CN100375140C CNB031466168A CN03146616A CN100375140C CN 100375140 C CN100375140 C CN 100375140C CN B031466168 A CNB031466168 A CN B031466168A CN 03146616 A CN03146616 A CN 03146616A CN 100375140 C CN100375140 C CN 100375140C
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- effect transistor
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- 238000005424 photoluminescence Methods 0.000 title 1
- 230000005669 field effect Effects 0.000 claims abstract description 62
- 238000004519 manufacturing process Methods 0.000 description 8
- 230000008859 change Effects 0.000 description 7
- 230000008901 benefit Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 239000004973 liquid crystal related substance Substances 0.000 description 2
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000005401 electroluminescence Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
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Abstract
The present invention relates to a driving circuit of an organic electroluminescent display, which comprises a current mirror, a first field effect transistor, a first cavity type field effect transistor and an operation amplifier, wherein the reference current input end of the current mirror is connected with the first field effect transistor and the first cavity type field effect transistor in series; a grid electrode of the first field effect transistor is connected with the operation amplifier in series. When the first cavity type field effect transistor is used as a current source of the driving circuit, the current source can not be affected by the drift of the output of a voltage source, and therefore, the driving circuit has high accuracy.
Description
Technical field
The present invention relates to a kind of driving circuit of organic electro-luminescent display, particularly relate to a kind of driving circuit that uses the cavity type field effect transistor as the organic electro-luminescent display of current source.
Background technology
(Organic Electro-Luminescence Display OLED) is a kind of luminous display of current drives organic film that uses to organic electro-luminescent display, and it luminously can be independent redness, blueness, green, or even full-color.Because the employed organic film of OLED is autoluminescence, therefore, (liquid crystal display LCD) also will add backlight at the liquid crystal rear unlike LCD.If OLED is compared with LCD, OLED can significantly reduce power consumption, simplifies manufacturing process, make the plate thickness attenuation, autoluminescence, wide viewing angle, response speed are fast so OLED has, low power consumption, contrast is strong, brightness is high, thin thickness, can full-colorization, reach characteristics such as animation display, and be considered to have the flat-panel screens of potentiality.
And in the process of this OLED development, still have many detail value to improve, for instance, the driving circuit cost of OLED is too high, and regular meeting causes the display frame of OLED inharmonious because some reason makes its drive current lose accuracy.
As shown in Figure 1, this figure is the rough schematic of known OLED driving circuit.In the driving circuit 100 of known OLED, mainly formed by fixed voltage source 110, operational amplifier 120, current mirror 125, MOS transistor 150 (comprising grid 151 and source electrode 153) and resistance 160.Wherein, OLED drives required electric current 145 is mainly provided by current mirror 125.And the required current source of current mirror 125, i.e. the current source of OLED drive current 145, then the electric current 161 that is produced by cross-pressure on the resistance 160 is provided.As for operational amplifier 120 and N passage MOS transistor 150, then, make that the pressure drop on the resistance 160 is identical with the pressure drop on the voltage source 110 in order to produce negative feedback paths 155.
But the layout of this driving circuit 100 is also incorrect in fact, and its reason is: the technician who is familiar with current mirror 125 as can be known, the electric current 145 of the P passage MOS transistor 140 of flowing through is with the electric current 135 of reference stream through P passage MOS transistor 130.In other words, the size of big young pathbreaker's reference current 135 values of electric current 145 value, and with both sizes than relevant.But because the cross-pressure that the current source of this electric current 135 is mainly on the resistance 160 produces, so electric current 135 is exactly the electric current 161 that cross-pressure produced on the resistance 160 in fact, the electric current 154 of the N passage MOS transistor 150 of just flowing through.
But disadvantageously, in order to make the current stabilization that cross-pressure produced on the resistance 160, to produce stable electric current 135 and OLED drive current 145, an accurate voltage source must be provided voltage source 110 so that resistance 160 two ends provide stable cross-pressure, and then produce stable electric current 161.Therefore, the voltage source 110 normally reference voltage source of a kind of Bandgap by name provides, and Bandgap itself is a kind of complexity height and the circuit that accounts for the integrated circuit layout area, so all relative paying must be arranged on OLED manufacturing process and cost.
In addition, because the relation of manufacturing process or ambient temperature, often make the output voltage 113 of voltage source 110 drift about, 155 drifts of related operational amplifier 120 feedback voltages, the drift of resistance 160 cross-pressures cause whole electric current 161, electric current 135 and 145 drifts of OLED drive current at last.
Summary of the invention
In view of this, the present invention proposes a kind of driving circuit of organic electro-luminescent display, make 110 of voltage sources need to use general voltage source to get final product, do not need to use complicated Bandgap mode, and allow that OP has bigger OFFSET, a drive current that does not change with the voltage source output voltage fluctuation is provided.
Fundamental purpose of the present invention provides a kind of driving circuit of organic electro-luminescent display, and it comprises current mirror, first field effect transistor, first cavity type field effect transistor and the operational amplifier.Wherein, current mirror has reference current output terminal and corresponding current output terminal, and the current output terminal of current mirror couples organic electro-luminescent display.First field effect transistor has grid, source electrode and drain electrode, and the drain electrode of first field effect transistor couples the reference current output terminal of current mirror.And the first cavity type field effect transistor also has grid, source electrode and drain electrode, and the grid of the first cavity type field effect transistor, source electrode couples mutually and be coupled to ground, the first cavity type field effect transistor drain electrode couple the source electrode of first field effect transistor at first node.Operational amplifier has first input end, second input end and output terminal, and the first input end of operational amplifier couples voltage source, second input end of operational amplifier couples first node, and the output terminal of operational amplifier couples the grid of first field effect transistor.
In preferred embodiment of the present invention, this driving circuit also comprises second to N cavity type field effect transistor.Wherein each cavity type field effect transistor all has grid, source electrode and drain electrode, and the grid of each cavity type field effect transistor, source electrode couples mutually and be coupled to ground, and its drain electrode couples first node.
And in another preferred embodiment of the present invention, above-mentioned voltage source is only for using two field effect transistors.Wherein two field effect transistors all have grid, source electrode and drain electrode.And the source electrode of field effect transistor gate, drain electrode and another field effect transistor is coupled to Section Point mutually.When the source electrode of a field effect transistor couples reference voltage, and the grid of another field effect transistor, when drain electrode is coupled to ground mutually, the voltage on the Section Point is the output voltage of this voltage source.
To sum up, the present invention proposes a kind of driving circuit of organic electro-luminescent display, replace the current source of known resistance with the cavity type field effect transistor, thereby make that driving circuit of the present invention has high precision, arrangement space is little and advantage such as production cost is low as driving circuit.
In order further to understand feature of the present invention and technology contents, below in conjunction with accompanying drawing the present invention is elaborated, yet appended graphic reference and the explanation usefulness of only providing not is to be used for the present invention is limited.
Description of drawings
Fig. 1 is the rough schematic of known OLED driving circuit;
Fig. 2 A is the rough schematic of the OLED driving circuit of preferred embodiment of the present invention;
Fig. 2 B is the OLED driving circuit figure of another preferred embodiment according to the present invention; And
Fig. 2 C is the OLED driving circuit figure of the another preferred embodiment of the present invention.
Embodiment
The present invention is based on known OLED driving circuit, its voltage source and operational amplifier cause the drive current of OLED driving circuit to produce drift often because of manufacturing process or ambient temperature factor.Therefore, the present invention considers to use for example with the resistance in the driving component replacement OLED driving circuit of cavity type field effect transistor, to the insensitive characteristic of cross-pressure, produce the stable reference current source that does not change, by driving component so that OLED to be provided stable drive current with cross-pressure.
Shown in Fig. 2 A, this figure is the rough schematic of the OLED driving circuit of preferred embodiment of the present invention.The driving circuit that this driving circuit 200 and Fig. 1 are known is compared, the N passage cavity type MOS transistor 210 that still has current mirror 125, MOS transistor 150, operational amplifier 120 (comprising input end 249), voltage source 110 and replace resistance 160.Wherein, OLED drives required electric current 220 is still mainly provided by current mirror 125.And the required current source of current mirror 125, i.e. the current source of driving circuit 200, then changing by N passage cavity type MOS transistor 210 is provided.As for 150 of voltage source 110, operational amplifier 120 and N passage MOS transistor still in order to produce negative feedback paths 155.
In preferred embodiment of the present invention, the working method of current mirror 125 will be identical with the known working method of Fig. 1, and the electric current 220 of the P passage MOS transistor 140 of promptly flowing through is with the electric current 230 of reference stream through P passage MOS transistor 130.Therefore, when replacing among Fig. 1 resistance 160 with N passage cavity type MOS transistor 210, the current source of the electric current 230 of the P passage MOS transistor 130 of flowing through in the current mirror 125, to be provided by N passage cavity type MOS transistor 210, just the drive current 220 of OLED will be provided by N passage cavity type MOS transistor 210.
Therefore, generally speaking, when P passage MOS transistor 130,140 source electrodes couple reference voltage VDD simultaneously, and when voltage source 110 provides the input end 249 of appropriate voltage to operational amplifier 120, P passage MOS transistor 130,140 and N passage MOS transistor 150 will fall within the workspace and conducting (ON), and the electric current 240 that N passage cavity type MOS transistor 210 is produced will be by N passage MOS transistor 150 to become the electric current 230 of 220 references of OLED drive current in the current mirror 125.
But preferred embodiment driving circuit 200 of the present invention is compared with Fig. 1 known drive circuit 100, and its electric current 240 that is also advantageous in that N passage cavity type MOS transistor 210 is produced will not be influenced by the source electrode 247 of N passage MOS transistor 150 and the nodes X voltage that operational amplifier 120 input ends 251 couple will.Its reason is that the current formula of desirable N passage cavity type MOS transistor 210 is:
Electric current=0.5 * μ
n* Cox * (W/L) | V
Gs-V
Tn|
2
But the grid 253 and the source electrode 255 of N passage cavity type MOS transistor 210 couple mutually and are coupled to ground.Therefore, grid 253 voltages of N passage cavity type MOS transistor 210 equate with source electrode 255 voltages and are zero.And the current formula of N passage cavity type MOS transistor 210 will change into:
Electric current=0.5 * μ
n* Cox * (W/L) |-V
Tn|
2
So the electric current 240 that N passage cavity type MOS transistor 210 is produced will with grid 253 voltages of N passage cavity type MOS transistor 210, source electrode 255 voltages, drain electrode 257 independent from voltage, and only with the parameter own such as the μ of N passage cavity type MOS transistor 210
n, Cox and size own be more relevant than W/L.Be that electric current 240 that N passage cavity type MOS transistor 210 is produced will not be subjected to that voltage influences on the nodes X.
Therefore, even when voltage source 110 is subjected to manufacturing process or ambient temperature to cause its output voltage to drift about, and related when influencing the drift of the output voltage of operational amplifier 120, the voltage of feedback path 155 (being voltage on the nodes X), electric current 240 will not influenced by these factors.So N passage cavity type MOS transistor 210 produces a constant current source that not influenced by voltage source 110 output voltages, make the reference current 230 in the current mirror 125, the drive current 220 of OLED to stablize thereupon.
Shown in Fig. 2 B, this figure is the OLED driving circuit figure of another preferred embodiment according to the present invention.The notion that replaces Fig. 1 resistance 160 with N passage cavity type MOS transistor 210 according to the present invention is applied, the present invention also can propose a plan: a plurality of N passage cavity type MOS transistor 210 are parallel on the nodes X, utilize the mode of wire jumper in the integrated circuit layout (Metal Option) to select to connect the number of required transistor 210 parallel connections, to reach the purpose of fine-adjusting current 245.
In Fig. 2 B, with a plurality of N passage cavity type MOS transistor 210 in parallel on the nodes X among Fig. 2 A.And compare with Fig. 2 A, the N passage cavity type MOS transistor 210 of a plurality of parallel connections can utilize the wire jumper mode to come fine-adjusting current 245.
And the equivalent resistance R that raising is seen into by N passage cavity type MOS transistor 210 ends
InCan reduce the current drift that electric current 230 produces because the Y point voltage changes in the current mirror 125.
Its reason is, mirror electric current 220 is except the current source that is subjected to current mirror 125 influences, because the effect of passage length modulation (Channel Length Modulation), also is subjected to node Y voltage influence and produces drift.When adopting N passage cavity type MOS transistor assembly to replace resistance, the equivalent resistance of being seen into by the Y point increases relatively, can improve electric current 230 in the current mirror 125 because the current drift that the change of Y point equivalent resistance is produced makes that the electric current 220 in the current mirror 125 becomes very stable.
In addition, when N passage cavity type MOS transistor 210 forms a constant current source that not influenced by voltage source 110 output voltages, and when making the drive current 220 of OLED not influenced by voltage source 110 output voltages, the output voltage that the drive current 220 of OLED can bear voltage source 110 drifts about on a large scale.Therefore, voltage source 110 does not use the Bandgap reference voltage source that adopts high complexity as is known and account for layout area, for example is that the ball bearing made using of two series connection P passage MOS transistor is as voltage source 110 and use instead.
Shown in Fig. 2 C, be the OLED driving circuit of the another preferred embodiment of the present invention.Among Fig. 2 C, only with the P passage MOS transistor 260,270 of two series connection as voltage source 110.Wherein, the grid 261 of P passage MOS transistor 260, drain electrode 263 are coupled to node Y with the source electrode 271 of P passage MOS transistor 270.And the source electrode 265 of working as P passage MOS transistor 260 couples reference voltage V
DD, and the grid 273 of P passage MOS transistor 270, drain electrode 275 be coupled to when ground mutually, and the voltage of node Y is the output voltage of voltage source 110.
By last, OLED driving circuit of the present invention has following advantage:
1. replace the current source of known resistance as the OLED driving circuit with the cavity type field effect transistor, therefore, this current source will not drift about with the output of OLED driving circuit internal source voltage and change;
2. when replacing known resistance with the cavity type field effect transistor, OLED driving circuit of the present invention is compared with known driving circuit, has bigger output resistance, and has improved the coupling of electric current in the driving circuit internal current mirror;
3. can use ball bearing made using to replace known OLED internal source voltage, to save its arrangement space and production cost.
To sum up, the present invention proposes the driving circuit of a kind of organic electro-luminescent display (OLED), particularly replace the current source of resistance, so the current source of current mirror will not be subjected to the influence of driving circuit internal source voltage output drift and change as current mirror by the cavity type field effect transistor.So OLED driving circuit of the present invention is compared with known driving circuit, except that having high accuracy, has more advantages such as layout dimension is little, production cost is low.
In sum; though the present invention discloses as above with aforesaid preferred embodiment; yet be not in order to limit the present invention; protection scope of the present invention should be as the criterion with the scope that claims define; those skilled in the art; a little change of being done without departing from the spirit and scope of the present invention all should be included within protection scope of the present invention.
Claims (8)
1. the driving circuit of an organic electro-luminescent display is characterized in that, comprising:
Current mirror, it has reference current output terminal and corresponding current output terminal, and the current output terminal of this current mirror couples this organic electro-luminescent display;
First field effect transistor, it has grid, source electrode and drain electrode, and wherein the drain electrode of this first field effect transistor couples the reference current output terminal of this current mirror;
The first cavity type field effect transistor, have grid, source electrode and drain electrode, wherein the grid of this first cavity type field effect transistor, source electrode couple and are coupled to ground mutually, and the drain electrode of this first cavity type field effect transistor couples the source electrode of this first field effect transistor in first node; And
Operational amplifier, have first input end, second input end and output terminal, wherein the first input end of this operational amplifier couples voltage source, and second input end of this operational amplifier couples first node, and the output terminal of this operational amplifier couples the grid of this first field effect transistor.
2. the driving circuit of organic electro-luminescent display as claimed in claim 1 is characterized in that, this driving circuit also comprises:
The second cavity type field effect transistor, it has grid, source electrode and drain electrode, and wherein the grid of this second cavity type field effect transistor, source electrode couple and are coupled to ground mutually, and the drain electrode of this second cavity type field effect transistor couples first node.
3. the driving circuit of organic electro-luminescent display as claimed in claim 2 is characterized in that, this driving circuit also comprises:
At least one cavity type field effect transistor, have grid, source electrode and drain electrode, wherein the grid of this at least one cavity type field effect transistor, source electrode couple and are coupled to ground mutually, and the drain electrode of this at least one cavity type field effect transistor couples first node.
4. the driving circuit of organic electro-luminescent display as claimed in claim 1 is characterized in that, this current mirror comprises:
Second field effect transistor, it has grid, source electrode and drain electrode, and wherein this second field effect transistor drain electrode is the reference current output terminal of this current mirror, and the source electrode of this second field effect transistor couples reference voltage;
The 3rd field effect transistor, it has grid, source electrode and drain electrode, wherein the grid of the grid of the 3rd field effect transistor and this second field effect transistor couples mutually, and be coupled to the drain electrode of this second field effect transistor, the source electrode of the 3rd field effect transistor couples this reference voltage, and the drain electrode of the 3rd field effect transistor is the current output terminal of this current mirror.
5. the driving circuit of organic electro-luminescent display as claimed in claim 1 is characterized in that, this voltage source comprises:
The 4th field effect transistor, it has grid, source electrode and drain electrode, and wherein the grid of the 4th field effect transistor, drain electrode are coupled to Section Point mutually, and the source electrode of the 4th field effect transistor couples reference voltage; And
The 5th field effect transistor, it has grid, source electrode and drain electrode, and wherein the grid of the 5th field effect transistor, drain electrode couple and are coupled to ground mutually, and the source electrode of the 5th field effect transistor couples Section Point.
6. the driving circuit of organic electro-luminescent display as claimed in claim 1 is characterized in that, this first field effect transistor is a N passage MOS transistor.
7. the driving circuit of organic electro-luminescent display as claimed in claim 1 is characterized in that, this first cavity type field effect transistor is a N passage cavity type MOS transistor.
8. the driving circuit of organic electro-luminescent display as claimed in claim 4 is characterized in that, this second field effect transistor and the 3rd field effect transistor are all P passage MOS transistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031466168A CN100375140C (en) | 2003-07-08 | 2003-07-08 | Driving circuit having electro photoluminescence display |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031466168A CN100375140C (en) | 2003-07-08 | 2003-07-08 | Driving circuit having electro photoluminescence display |
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| Publication Number | Publication Date |
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| CN1567408A CN1567408A (en) | 2005-01-19 |
| CN100375140C true CN100375140C (en) | 2008-03-12 |
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| CNB031466168A Expired - Fee Related CN100375140C (en) | 2003-07-08 | 2003-07-08 | Driving circuit having electro photoluminescence display |
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Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2435956B (en) * | 2006-03-09 | 2008-07-23 | Cambridge Display Tech Ltd | Current drive systems |
| CN104200776B (en) * | 2014-09-25 | 2017-02-15 | 武汉精测电子技术股份有限公司 | Pixel driving circuit and driving method for improving Mura defect of OLED panel |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20020105373A1 (en) * | 2001-02-08 | 2002-08-08 | Minoru Sudo | LED drive circuit |
| US6501449B1 (en) * | 1999-12-08 | 2002-12-31 | Industrial Technology Research Institute | High matching precision OLED driver by using a current-cascaded method |
| JP2003188465A (en) * | 2001-10-11 | 2003-07-04 | Hamamatsu Photonics Kk | Light emitting element driving circuit |
-
2003
- 2003-07-08 CN CNB031466168A patent/CN100375140C/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6501449B1 (en) * | 1999-12-08 | 2002-12-31 | Industrial Technology Research Institute | High matching precision OLED driver by using a current-cascaded method |
| US20020105373A1 (en) * | 2001-02-08 | 2002-08-08 | Minoru Sudo | LED drive circuit |
| JP2003188465A (en) * | 2001-10-11 | 2003-07-04 | Hamamatsu Photonics Kk | Light emitting element driving circuit |
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| Publication number | Publication date |
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| CN1567408A (en) | 2005-01-19 |
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