CN104427266A - Pixel sensing unit - Google Patents
Pixel sensing unit Download PDFInfo
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- CN104427266A CN104427266A CN201310394985.6A CN201310394985A CN104427266A CN 104427266 A CN104427266 A CN 104427266A CN 201310394985 A CN201310394985 A CN 201310394985A CN 104427266 A CN104427266 A CN 104427266A
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Abstract
The invention provides a pixel sensing unit. The pixel sensing unit comprises a light sensor and a pixel amplifier, wherein the pixel amplifier comprises a floating diffusion region, a resetting gate, a source electrode following coupling device and a bias voltage control unit; the floating diffusion region is coupled with the light sensor; the resetting gate is provided with a control end point, a first connection end point and a second connection end point; resetting operation is carried out on the floating diffusion region on the second connection end point of the resetting gate according to a resetting signal received by the control end point of the resetting gate; the source electrode following coupling device is coupled with the floating diffusion region and is used for generating an output voltage signal according to a level of the floating diffusion region; the bias voltage control unit is coupled with the source electrode following coupling device and is used for providing first bias voltage when the resetting operation is carried out and providing second bias voltage after the resetting operation is finished.
Description
Technical field
Present invention is directed to a kind of pixels sense unit, espespecially a kind of can compensation charge injection effect to increase the pixels sense unit of output voltage swing.
Background technology
Along with the development and progression of science and technology, pixel in liquid crystal display and the distance between pixel also more and more less, in the design of small pixel, because pixel amplifier allows more pixels to share floating node (floating node), therefore can improve light harvesting effective area ratio (fill factor) and maintain high-conversion-gain simultaneously.But, carry out feedback owing to can have parasitic capacitance in circuit to gain, therefore the output voltage swing (output swing) of pixel amplifier can be subject to the impact of frequency feed-in (clock feedthrough) and charge injection (charge injection) effect.
For general image pixel sensing, the electric capacity be coupled between the grid of reset transistor and source electrode can cause resetting charge injection.Adding to the lower edge of reset frequency of grid of reset transistor, this electric capacity coupled can by the voltage of the floating node of pixel toward drop-down.The voltage of this floating node is lower by what draw, and the voltage swing that pixel can have is less.Because this phenomenon, the dynamic range of general image pixel sensing can reduce.
Therefore, the impact how avoiding the output voltage swing of frequency feed-in effect on pixels sense unit to cause is still a large problem in this field.
Summary of the invention
Therefore, an object of the present invention be propose a kind of can compensation charge injection effect to increase the pixels sense unit of output voltage swing, to solve above-mentioned problem.
According to one embodiment of the invention, it discloses a kind of system of the present invention and discloses a kind of pixels sense unit.This kind of pixels sense unit includes an optical sensor and a pixel amplifier.This pixel amplifier includes a floating diffusion region, and resets lock, one source pole follower and a bias control unit.This floating diffusion region is coupled to this optical sensor.This replacement lock has a control end points, one first connection end point and one second connection end point, and wherein this replacement lock is used for carrying out a replacement operation according to the replacement signal that this control end points of this replacement lock receives to this floating diffusion region on this second connection end point of this replacement lock.This source follower is coupled to this floating diffusion region, is used for producing an output voltage signal according to the position standard of this floating diffusion region.This bias control unit, is coupled to this source follower, when this replacement operates, provides one first bias voltage, after replacement operation terminates, then provides one second bias voltage.
As from the foregoing, the invention provides a kind of pixels sense unit, its impact produced by compensation charge injection effect, to increase the output voltage swing of pixel amplifier, and promote the quality of pixel reading.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of an embodiment of present invention pixel sensing cell.
Fig. 2 is the sequential chart of the control signal of present invention pixel sensing cell.
Embodiment
Some vocabulary is employed to censure specific assembly in the middle of specification and follow-up claim.Person with usual knowledge in their respective areas should understand, and hardware manufacturer may call same assembly with different nouns.This specification and follow-up claim are not used as with the difference of title the mode distinguishing assembly, but are used as the criterion of differentiation with assembly difference functionally." comprising " mentioned in the middle of specification and follow-up claims is in the whole text an open term, therefore should be construed to " comprise but be not limited to ".In addition, " coupling " word at this is comprise directly any and be indirectly electrically connected means.Therefore, if describe a first device in literary composition to be coupled to one second device, then represent this first device and directly can be electrically connected in this second device, or be indirectly electrically connected to this second device by other device or connection means.
An image sensor comprises the matrix of a plurality of pixels sense unit arrangement, explains for a pixels sense unit at this.Please refer to Fig. 1, Fig. 1 is an embodiment of the present invention's pixels sense unit 100.Pixels sense unit 100 comprises optical sensor 102, pixel amplifier 110 and a bias control unit 120.
Pixel amplifier 110 includes a floating diffusion region (floating diffusion) FD, a replacement lock 112, is chosen lock 114, and transmitted lock 115, one source pole follower 116 and a capacitance component 118.In other embodiments, choose lock 114 and inessential, also can otherwise reach the object choosing a pixels sense unit, capacitance component 118 can be parasitic capacitance.Reset lock 112 and there is a control end C1, one first link N11 and one second link N12, and reset lock 112 and be used for carrying out a replacement operation according to the replacement signal S_RST that control end C1 receives to the floating diffusion region FD on the second link N12.Choosing lock 114 is select a pixels sense unit to export, but in other embodiments, selects lock 114 to omit, and reach identical object with other operation.Choose lock 114 and there is a control end C2, one first link N21 and one second link N22, and choose that lock 114 is used for receiving according to control end C2 one choose signal S_SEL and export a voltage signal S_V in the first link N21.Source follower 116 is coupled to the second link N12 resetting lock 112 and the second link N22 choosing lock 114, and source follower 116 is used for according to electric charge signal S_CHG to produce voltage signal S_V.Capacitance component 118 is such as the electric capacity of parasitic capacitance or reality, between the second link N12 being coupled to replacement lock 112 and the first link N21 choosing lock 114.In addition, transmission lock 115 is coupled to the first link N11 and source follower 116 that reset lock 112, to be used for, according to a transmission signal S_TX, electric charge signal S_CHG is passed to source follower 116.
Bias control unit 120 is coupled to pixels sense unit 110, and bias voltage bias control unit 120 is used for according to the voltage quasi position V resetting signal S_RST and control to choose the first link N21 of lock 114.Bias control unit 120 can be that multiple pixel amplifier 110 is shared, or the pixel amplifier 110 of a whole row or column is shared.For bias control unit 120, it includes current source 122, operational amplifier 124 and a reference voltage generator 126.Current source 122 is coupled to source follower 116, and current source 122 is used for providing a bias current I to pixels sense unit 110 according to a control signal S_CTRL.Operational amplifier 124 is coupled to current source 122 and source follower 116, and operational amplifier 124 is used for the dividing potential drop V_DVI that produces according to a bias current I and reference voltage V_REF produces and control signal S_CTRL.Reference voltage generator 126 is coupled to operational amplifier 124, and reference voltage generator 126 is used for according to resetting signal S_RST to adjust reference voltage V_REF.In other embodiments, operational amplifier 124 can control multiple current source 122 simultaneously.
In the present embodiment, pixels sense unit 110 can first carry out a pixels sense operation, makes optical sensor 111 receive light signal to produce electric charge signal S_CHG, now transmits lock 115 and not yet electric charge signal S_CHG is passed to source follower 116.Then pixels sense unit 110 can carry out a pixel read operation: first reset the replacement signal S_RST that lock 112 can receive according to control end C1, such as, be first standard, carry out replacement operation to floating diffusion region FD.After replacement lock 112 couples of floating diffusion region FD carry out replacement operation, source follower 116 exports according to the floating diffusion region FD be reset.It should be noted that, after replacement operation, reset signal S_RST and can change into second standard to terminate to reset operation, now easily produce Charge injection effect and to affect the position of floating diffusion region FD accurate, and then affect the output valve of source follower 116, be greater than second standard for first standard in the present embodiment.
The level that reference voltage generator 126 can adjust reference voltage V_REF compensates the Charge injection effect produced in pixels sense unit 100.In replacement operation, reference voltage V_REF is a first higher reference level, and the level of the dividing potential drop V_DVI that bias current I is produced is a first higher bias voltage; The a bit of time after replacement operation, reference voltage V_REF just comes down to a second lower reference level, and the level of the dividing potential drop V_DVI that bias current I is produced is a second lower bias voltage.When the level of reference voltage V_REF is downgraded, the level of the dividing potential drop V_DVI that bias current I produces also can decline thereupon, now transmit lock 115 just can open/electric charge signal S_CHG is passed to floating diffusion region FD, then exported by source follower 116 by conducting.Level due to dividing potential drop V_DVI drops to one second bias voltage, and the voltage quasi position V choosing the first connection end point N21 of lock 114 also can decline, and therefore voltage quasi position V can affect floating diffusion region FD by capacitance component 118.
Decline a little to cause the level of electric charge signal S_CHG due to Charge injection effect can be produced when transmitting lock 115 and electric charge signal S_CHG being passed to source follower 116, therefore the voltage signal S_V that source follower 116 produces according to electric charge signal S_CHG also can decline a little, cause the reduction of the output voltage swing of pixels sense unit 100, so, when voltage quasi position V is charged to electric charge signal S_CHG by capacitance component 118, then the level of electric charge signal S_CHG can be drawn high again, with the impact that compensation charge injection effect causes, and then recover pixels sense unit 100 due output voltage swing originally.Voltage quasi position V note that capacitance component 118 can be a capacitor or a parasitic capacitance, as long as can carry out to electric charge signal S_CHG the effect that charging can reach compensation charge injection effect by capacitance component 118.For example, when the first connection end point N11 resetting lock 112 is directly connected in the first connection end point N21 choosing lock 114, namely the parasitic capacitance produced between second link N12 of replacement lock 112 and the first link N21 choosing lock 114 can be used as capacitance component 118 and uses, but, this is only as the use that example illustrates, not as restrictive condition of the present invention.
Please refer to Fig. 2, Fig. 2 is the sequential chart of the control signal of present invention pixel sensing cell 100.In fig. 2, pixels sense unit 100 can enter an exposure stage at the beginning, under this stage, reset signal S_RST first can carry out replacement operation to floating diffusion region FD, and transmission signal S_TX can be unlocked in the cycle of carrying out replacement operation, make transmission lock 115 that electric charge signal S_CHG is passed to source follower 116, so expose.When pixels sense unit 110 carries out pixel read operation, reset signal S_RST and choose signal S_SEL and can open in the period of time point T1 ~ T2 simultaneously, make to reset lock 112 couples of electric charge signal S_CHG to carry out replacement operation.When after the replacement operation that replacement lock 112 completes electric charge signal S_CHG, reset signal S_RST and can be closed in time point T2, now choose signal S_SEL and continue to be held open.After replacement signal S_RST is closed, reference voltage generator 126 can start to turn down the level of reference voltage V_REF again to draw high the level of electric charge signal S_CHG in time point T3.Then, transmission signal S_TX can be unlocked in time point T4, makes transmission lock 115 that electric charge signal S_CHG is passed to source follower 116.After electric charge signal S_CHG is passed to source follower 116 by transmission lock 115, transmission signal S_TX can be closed in time point T5, now choose signal S_SEL to continue to be held open, and reference voltage generator 126 controls reference voltage V_REF and maintains low level, make pixels sense unit 110 can continue pixel read operation (that is, convert electric charge signal S_CHG to voltage signal S_V by source follower 116, and export by choosing lock 114).After voltage signal S_V is read smoothly, choose signal S_SEL and can be closed in time point T6, reference voltage generator 126 adjusts reference voltage V_REF and returns to high levle simultaneously, to complete the operation that pixels sense unit 110 pixel reads.
Haveing the knack of this those skilled in the art when can in reading the operation understanding each signal shown in Fig. 2 after above paragraph easily, to describe in detail and change can with reference to aforementioned, for for purpose of brevity, therefore just repeat no more in this.
[symbol description]
110 pixel amplifiers
100 pixels sense unit
102 optical sensors
112 reset lock
114 choose lock
116 source follower
118 capacitance components
115 transmission locks
120 bias control units
122 current sources
124 operational amplifiers
126 reference voltage generators
Claims (5)
1. a pixels sense unit, includes:
One optical sensor; And
One pixel amplifier, includes:
One floating diffusion region, is coupled to this optical sensor;
One resets lock, have a control end points, one first connection end point and one second connection end point, wherein this replacement lock is used for carrying out a replacement operation according to the replacement signal that this control end points of this replacement lock receives to this floating diffusion region on this second connection end point of this replacement lock;
One source pole follower, is coupled to this floating diffusion region, is used for producing an output voltage signal according to the position standard of this floating diffusion region; And
One bias control unit, is coupled to this source follower, when this replacement operates, provides one first bias voltage, after replacement operation terminates, then provides one second bias voltage.
2. pixels sense unit as claimed in claim 1, wherein this bias control unit includes:
One current source, is coupled to this source follower, and being used for controlling signal according to one provides a bias current to give this pixels sense unit;
One operational amplifier, is coupled to this current source and this source follower, is used for the dividing potential drop that produces according to this bias current and a reference voltage, produces this control signal; And
One reference voltage generator, is coupled to this operational amplifier, is used for according to this replacement signal to adjust this reference voltage.
3. pixels sense unit as claimed in claim 1, wherein in a pixel read operation of this pixels sense unit, this control unit, after this replacement lock carries out this replacement operation to this electric charge signal, just controls this voltage quasi position that this chooses this first connection end point of lock.
4. pixels sense unit as claimed in claim 4, wherein this bias control unit can reduce this voltage quasi position of this first connection end point of this replacement lock.
5. pixels sense unit as claimed in claim 1, wherein this pixels sense unit separately includes:
One transmission lock, is coupled to this replacement lock and this source follower, and wherein control during this chooses this voltage quasi position of this first connection end point of lock in this control unit, this electric charge signal just can be passed to this source follower by this transmission lock.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310394985.6A CN104427266B (en) | 2013-09-03 | 2013-09-03 | Pixels sense unit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201310394985.6A CN104427266B (en) | 2013-09-03 | 2013-09-03 | Pixels sense unit |
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| CN104427266A true CN104427266A (en) | 2015-03-18 |
| CN104427266B CN104427266B (en) | 2017-08-25 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109194890A (en) * | 2018-10-31 | 2019-01-11 | 昆山锐芯微电子有限公司 | Image sensor pixel circuit and its working method |
| CN112449126A (en) * | 2019-09-05 | 2021-03-05 | 昇佳电子股份有限公司 | Light sensor circuit |
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| CN202150896U (en) * | 2011-06-23 | 2012-02-22 | 格科微电子（上海）有限公司 | Signal reading circuit and module of image sensor |
| CN102487436A (en) * | 2010-12-01 | 2012-06-06 | 英属开曼群岛商恒景科技股份有限公司 | Sensing pixel array and sensing apparatus |
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| US20100097509A1 (en) * | 2004-08-25 | 2010-04-22 | Mauritzson Richard A | Pixel for boosting pixel reset voltage |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109194890A (en) * | 2018-10-31 | 2019-01-11 | 昆山锐芯微电子有限公司 | Image sensor pixel circuit and its working method |
| CN109194890B (en) * | 2018-10-31 | 2020-12-08 | 锐芯微电子股份有限公司 | Image sensor pixel circuit and working method thereof |
| CN112449126A (en) * | 2019-09-05 | 2021-03-05 | 昇佳电子股份有限公司 | Light sensor circuit |
| US11509322B2 (en) | 2019-09-05 | 2022-11-22 | Sensortek Technology Corp. | Light sensor circuit |
| CN112449126B (en) * | 2019-09-05 | 2023-02-10 | 昇佳电子股份有限公司 | Light sensor circuit |
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| CN104427266B (en) | 2017-08-25 |
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