CN102073426A - Touch inductive circuit - Google Patents
Touch inductive circuit Download PDFInfo
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- CN102073426A CN102073426A CN 201010623500 CN201010623500A CN102073426A CN 102073426 A CN102073426 A CN 102073426A CN 201010623500 CN201010623500 CN 201010623500 CN 201010623500 A CN201010623500 A CN 201010623500A CN 102073426 A CN102073426 A CN 102073426A
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Abstract
The invention provides a touch inductive circuit, comprising a driving point and a sensing point, wherein a mutual capacitor is connected between the driving point and the sensing point; the driving point and ht sensing point are respectively grounded by the respective self capacitor; the sensing point is connected to a load sensing circuit by a resistor; the driving point is serially connected to the resistor and a current meter; the other end of the current meter is grounded.
Description
Technical field
The present invention relates to the touch technology field, more specifically, the present invention relates to a kind of sensor circuit of touch-screen.
Background technology
Projecting type capacitor formula touch-screen is the technology of Apple in issue in 2007, and its mobile cellular telephone iPhone is the commercial Application of first employing projecting type capacitor formula touch panel.By permanance, reliability and the overall performance of further raising projecting type capacitor formula touch panel, projecting type capacitor formula touch panel is accelerated the growth of touch panel industry just day by day.
Projecting type capacitor formula touch technology comprises self-capacitance and mutual capacitance.Wherein, self-capacitance is also referred to as absolute capacitance or stray capacitance, and from engineering viewpoint, self-capacitance is considered to connect the stray capacitance of object and the earth.Most of self-capacitance sensors are brought into play function by the variation of the capacity of detection self-capacitance, and capacitive transducer has the induction electrode that conductive materials is made usually, by sending the electric capacity that electric charge in a small amount comes exploring electrode internally.When the mankind touched the body proximity transducer, the electric capacity of human body touch body and the coupling capacitance of sensing electrode can change the self-capacitance of sensing electrode.The comparison of self-capacitance by sensing electrode and original self-capacitance can determine whether touch panel has the human body contact.
Fig. 1 illustrates the distribution of electrodes and the structure of a kind of self-capacitance touch panel of prior art.The glass substrate top is transparent sensing electrode, and these electrodes are in the same plane and isolated each other.Each electrode has a tail to link to each other with the sensor of self-capacitance.The quantity of inductor chip is directly proportional with the quantity of contact point.In touch panel applications, owing to the cost height of directly responding to, so it is not used usually.
Mutual capacitance is also referred to as conduction electric capacity, and the mutual capacitance touch panel moves based on the coupling capacitance between their electrodes of induction or the variation of mutual capacitance.As shown in Figure 2, the electrode of mutual capacitance touch panel is made up of driver circuit and induction line.These lines are in two mutually perpendicular separation layers, and are mingled with megohmite insulant between this is two-layer.In the normal running, activate drive wire, between adjacent electrode, set up capacitive coupling.When sense object touches when an electrode projects the field line of another electrode, can detect variation and definite contacting points position of mutual capacitance.The mutual capacitance touch panel has good optical outward appearance and sensing stability, but the manufacturing cost height of existing implementation method, complex process.
For other touch panel of the prior art, there is the problem of optical clarity and permanance in the resistive touch panel technology, and there is inhomogeneity problem in surface capacitance touch screen technology, and SAW and IR technology are difficult to be applied to portable set.Though the projected capacitive contact panel is better than other effect, touch-screen is formed with multilayer, and peripheral circuit is many, manufacturing cost height, complicated technology realization.
Summary of the invention
For overcoming the above-mentioned a plurality of defectives in the existing touch screen technology, the present invention proposes a kind of touch-screen and sensor circuit thereof.
According to an aspect of the present invention, a kind of touch induction circuit has been proposed, comprise drive point and induction point, connect mutual capacitance between the two, drive point and induction point pass through self-capacitance ground connection separately respectively, induction point is connected to the electric charge induction circuit by resistor, drive point resistors in series and galvanometer, galvanometric other end ground connection.
Description of drawings
Fig. 1 is the self-capacitance touch panel structural representation of prior art;
Fig. 2 is the mutual capacitance touch panel structural representation of prior art;
Fig. 3 is the structural representation according to the touch panel of the embodiment of the invention;
Fig. 4 is the electrode synoptic diagram according to the direct driving of the embodiment of the invention;
Fig. 5 is the measurement result figure of the corresponding electric capacity of sensor of different size;
Fig. 6 is the distribution of electrodes figure according to the multiple spot design of the embodiment of the invention;
Fig. 7 is the 3D synoptic diagram according to the touch-sensitive area unit of the embodiment of the invention;
Fig. 8 is according to the touch sensing unit of the embodiment of the invention structural drawing when the no finger touch;
Fig. 9 is the sensing unit synoptic diagram according to embodiment of the invention shunt mode when the finger touch;
Figure 10 is the sensing unit synoptic diagram of transmission mode when finger closely touches;
Figure 11 is the circuit diagram of charge amplifier;
Figure 12 is the structured flowchart according to the touch control system of the embodiment of the invention;
Figure 13 is the figure as a result of two finger touch panels of signal;
Figure 14 be the signal single finger touch pressure color code, wherein colourity deeply feel more show strong more;
Figure 15 is the result schematic diagram of finger touch diverse location;
Figure 16 is the result schematic diagram that finger touches under different pressures;
Figure 17 is the synoptic diagram of catching of multiple point touching detection.
Embodiment
Below in conjunction with the drawings and specific embodiments a kind of touch-screen provided by the invention and sensor circuit thereof are described in detail.
(Indium Tim Oxide, ITO) form, and realizes complexity and cost height by electrode by two-layer tin indium oxide for traditional mutual capacitance touch panel.The present invention discloses a kind of method of making multiple spot individual layer touch panel, and touch panel only is made up of a transparent ITO electrode thin layer that is deposited on the glass substrate.
Fig. 3 is the structural representation according to the touch-screen of the embodiment of the invention.As shown in Figure 3, touch-screen comprises touch panel and LCD unit.Touch panel is positioned at the top of LCD unit, and touch panel only is made up of one deck ITO electrode that is deposited on the glass substrate.For the application of touch-screen, touch panel can be laminated on the LCD unit.The ITO electrode down, between glass substrate and LCD unit.Glass substrate can provide protection for touch panel, is not subjected to scratch, and improves the durability of design.The ITO Butut adopts the photoetching of standard.In the practice, can add bonding coat and screen layer.
1), in glass substrate (for example, thickness is 1.1mm) in further detail, wherein, as shown in Figure 3, touch panel manufacturing process comprises:, wherein one side apply ITO layer (for example, thickness is 1500 dusts); 2), be that photolithography seal (photolithography) prepares the pattern of electrode, the minimum spacing between the electrode is 100um; 3), in photolithography seal (photolithography) mode, the ITO layer of glass sheet is made the apperance of electrode.Between the glass substrate of touch panel and LCD unit, arrange polarizer.
ITO electrode layer of the present invention adopts mutual capacitance, comprises the drive wire and the line of induction.For the application as keyboard or controller equiment, the touch area is clear and definite for the technician, and it can adopt direct driving.As shown in Figure 4, the inductor of ITO electrode layer comprises drive electrode and induction electrode, and wherein, in the middle of induction electrode was positioned at, drive electrode was around induction electrode.
Usually, the size of electrode can influence capacity coupled result, determines preferred size by the capacitance variations of test different size touch inductor under finger touch.The mutual capacitance of using HP4284A (the accurate LCR table of Hewlett-Packard/Agilent 4284A is measured the electric capacity between the two poles of the earth) to measure the different size between drive electrode and the induction electrode.As Fig. 5, the capacitance variations corresponding to different external areas is shown, it is 2x2 that external area is shown respectively among the figure, 4x4,6x6 and 8x8 (mm
2) measurement result of pairing capacitance variations.
When the finger proximity transducer, capacitance can descend, and this electric capacity drop-out value is directly proportional with the electric field amount of being shunted.When the size of sensor strengthened, mutual capacitance also increased thereupon.But effectively the electric capacity drop-out value reaches capacity because of the approaching of finger, and shows downward trend.This is because the contact area between finger and the touch panel no longer is enough to contain the whole circumference of sensor.Therefore, if the size of sensor is too little, then can cause the coupling capacitance difference that can not offer the best to respond touch action.Consider this two factors, the size of mutual capacitance sensors should be best suited in this scope of 4-6mm.
Fig. 6 illustrates the entire I TO distribution of electrodes of multiple point touching panel, and right-hand component view and left side general view are not corresponding among Fig. 6, and the oblique line on the right is filled the only below of on the left side, and it is not even distribution.Shown in the little figure in right side, a left side tiltedly is to drive, and the right side tiltedly is induction, and what fill grid is pad, and the touch-sensitive area unit is exaggerated demonstration in this drawing.In each touch sensing unit, in the middle of an induction zone is mixed in by 2 drive areas.Each drive area has an independent lead-in wire to be connected with outside.In Fig. 6, there are some drive areas to be provided with highlighted demonstration, they have represented one of 8 levels virtual " drive wire " on the panel, and the outside links together.Therefore, a line of induction and 8 that has 8 cylindricalitys is listed as virtual drive wire.
About the Multipoint Drive method, at first use first row of virtual drive wire, and other untapped drive wire is coupled over the ground.Collect 8 groups of data by scanning each line of induction.By scanning each group drive wire successively, repeat these steps 8 time, last, obtain 64 groups of data plots of whole front panel.
Below go through the principle of work of mutual capacitance touch panel.At first, with reference to figure 7, Fig. 7 illustrates the circuit model of the touch-sensitive area unit of Fig. 6, in the touch-sensitive area unit, shown in Fig. 6 and 7, drive point and induction point is arranged, just corresponding to driving district and the induction zone of Fig. 6.2 mutual capacitance (C have been formed between the two
DS) and self-capacitance (C separately
D, C
S).
The circuit model of Fig. 7 can be described as a schematic diagram, shown in 8 figure.Among Fig. 8, be connected with mutual capacitance between drive point and the induction point, drive point and induction point pass through self-capacitance ground connection separately respectively, and induction point is connected to the electric charge induction circuit by resistor, drive point resistors in series and galvanometer, galvanometric other end ground connection.Be excited when drive point, field is projected onto induction point.When inductor is not sensed object, C
DSIn the capacitive coupling point keep relative stability.
On the other hand, when an object such as finger are close to sensor, be equivalent to form the circuit of Fig. 9 this moment, the equivalent electrical circuit that the expression finger brings in the dotted line of top as shown in Figure 9, can be upset C
DSElectric field.Finger can be considered to a point and be connected to virtual field.In this case, electric field flows to a lower finger point from a higher potential point.Finger effectively is diverted to ground with the part electric field, so the amount that is connected with induction electrode of electric field reduces, i.e. C
DSThe electric capacity that falls, this operation is referred to as " shunt mode ".
As Figure 10, the finger the closer to the time, object and electrode (C
DFAnd C
SF) between electric capacity increase considerably.From the electric field of drive electrode capacitive coupling object, as the bolter of whole object electric field.Electric field is known the increase of induction electrode and effectively the time, C
DSIncrease.This phenomenon is called " transmission mode " or " human transmission effects ".
In fact, shunt mode and transmission mode all are simultaneous, but touch the main shunting principle that relies on.In order to ensure the touch panel stable operation, must stop transmission mode to control touch.In this case, ITO electrode and finger (C
DF﹠amp; C
DS) between electric capacity, with C
DSBy comparison must be little, so human transmission effects can be left in the basket.Therefore,
C
DS＞＞C
DF?&?C
SF (6.1)
And
A here and d represent the distance between overlapped district area and finger and electrode layer respectively.
In order to ensure the stable operation of touch panel, must guarantee the operation of shunt mode, rather than human transmission mode.Can calculate and keep required finger of shunt mode operation and the critical separation distance between the ITO layer.Equation (6.1) and (6.2) are if C
DS=2pF, ε
(glass)=4 and finger and the overlapped district of electrode area A
MAX=1.96x10
-5m
-2(being r=2.5mm).Critical separation distance D
MINBe 0.1mm, so the thickness of cover glass enough stop transmission mode to become to take as the leading factor usually.
Detection method
Existing detection method is all accurate and complicated than the application's mode, generally all can use the ASIC controller.Among the application, touch can be by surveying C
DSThe drop-out value of electric capacity uses two kinds of methods to survey this variation.First method is the induction point of measuring voltage coupling, and it requires sensor circuit that high output resistance is arranged.The voltage of induction point can pass through formula (6.3) and obtain.
ΔVs＝(1+C
S/C
DS)
-1ΔV
D (6.3)
Therefore, at induction point (Δ V
S), C
DSBe directly proportional with the AC compounent of being surveyed.Because the signal that obtains by this method is very little and moment, and precisely controls C
DSWith stray capacitance C
SBe to be difficult to realize, so this method degree easy to use is relatively poor.
Second method couples together the line of induction and charge amplifier, and perhaps each line of induction all is connected with a charge amplifier, and for example, the operational amplifier compositor as shown in figure 11.The small amount of charge that capacitive coupling produces, electric charge is forced to flow to upper channel, is stored among the feedback condenser C, and is transformed into the voltage output Vout of readability, therefore touches the minimizing that can be considered to flow of charge.This detection method has produced a better output drive strength, and in charge amplifier circuit, output gain signal can be changed by changing feedback capacity.
Control system
Figure 12 shows that the block diagram of control system.This system comprises touch-screen, electric charge induction circuit, sample-and-hold circuit, Port Multiplier, analog to digital converter and controller.The output signal of touch panel is through the electric charge induction circuit, after obtaining by induction as above, output signal is buffered in the sample-and-hold circuit, sample-and-hold circuit is to the processing of taking a sample of this signal, and by the simulation Port Multiplier signal that stores is supplied to the ADC converter successively, the numeral output after the conversion is sent to the MCU controller and carries out digital processing.
MCU sends pulse signal to drive touch-screen, and touch-screen returns induced signal to the electric charge induction circuit, and the charge amplifier (not shown) amplifies signal.
The result
The application's touch panel scan rate can reach 100Hz, and the corresponding response time is 10ms.This is enough fast for the mobile object on touch panel operation or the tracking panel.Optical clarity also is an advantage of this design, because panel construction comprises the ITO individual layer is only arranged.Transparency depends primarily on the thickness of ITO layer.On this prototype, the ITO coating is 700A, and the transmittance of being surveyed is 91%.In theory, the panel light transmission rate can reach 95%.
Figure 13 illustrates 2 fingers is placed on example on the touch panel.According to the difference of finger pressure, the area difference that skin covers, common single touch can cover 1 to 4 sensor.The minimizing amplitude of the charge amplifier output that finger pressure can pass through reflects.This charge amplifier output is adjusted to several depth level before showing by the ADC digitizing and on screen.Figure 14 is shown as the color code of finger pressure level.Dark more strong more, shallow more weak more.
Data according to calibration can be located focus, and image can be accomplished to handle in real time and improve resolution, and some DSP algorithms insert as the sub-pixel of having reported.In this stage, can use bilinear interpolation increases panel resolution rate, from hardware resolution 8x8 to virtual resolution 15x15.Two adjacent datas are divided equally, inserted into new data, in order to increase resolution dividing the new numerical value that draws equally.
Figure 15 at diverse location, points different pressure and multiple spot result of detection figure to the finger touch that is respectively shown in Figure 17.Synthetic image after improving resolution, show how accurate hotspot graph picture and touch after coordinate more accurately.
Sum up and comparison
In a word, that the design of proposed individual layer projecting type capacitor formula touch panel has is simple in structure, permanance strong, the high grade of transparency, multiple point touching electric capacity and the low advantage of cost, and it is not influenced by surface blot.Single layer structure also can be used for curved substrate, and but, the quantity that the I/O of design connects is 2x (NxM), supposes that resolution is NxM.
The design of being carried is not complicated as other two kinds of technology, but individual layer mutual capacitance method has the advantage that other technology does not have, and it has the structure of individual layer, and has optical clarity preferably with respect to double-deck mutual capacitance.It utilizes various method for scanning, reduces the quantity of required sensor chip.Measuring mutual capacitance is to see through to detect electric charge, but not directly measures self-capacitance, has eliminated the necessity of using glass-chip to combine with sensor chip like this.All these advantages so that integrating process are simple more and cost is lower.Therefore, the individual layer mutual capacitance is the substitute of projecting type capacitor touching technique, to realize function, the balance of performance and cost.
By using individual layer projecting type capacitor formula touch panel of the present invention, make project organization simple, the permanance height, the transparency height, multiple point touching electric capacity and cost are low, and not influenced by surface blot, and single layer structure also makes it can be used for curved substrate.
It should be noted that at last above embodiment is only in order to describe technical scheme of the present invention rather than the present technique method is limited.
Claims (6)
1. a touch induction circuit comprises drive point and induction point, connects mutual capacitance between the two, drive point and induction point pass through self-capacitance ground connection separately respectively, induction point is connected to the electric charge induction circuit by resistor, drive point resistors in series and galvanometer, galvanometric other end ground connection.
2. the described sensor circuit of claim 1 is characterized in that, is excited when drive point, and field is projected onto induction point.
3. the described sensor circuit of claim 1 is characterized in that, described electric charge induction circuit comprises charge amplifier, charge amplifier feedback condenser in parallel.
4. the described sensor circuit of claim 3 is characterized in that, described each induction point all is connected with a charge amplifier.
5. the described sensor circuit of claim 3 is characterized in that, the small amount of charge that described induction point coupling produces is forced to the upper reaches, is stored in the feedback condenser, and is transformed into the voltage output of easily reading.
6. the described sensor circuit of claim 5 is characterized in that, the gain of described voltage output changes by the electric capacity that changes feedback condenser.
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| CN 201010623500 CN102073426A (en) | 2010-12-29 | 2010-12-29 | Touch inductive circuit |
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| CN 201010623500 CN102073426A (en) | 2010-12-29 | 2010-12-29 | Touch inductive circuit |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102955634A (en) * | 2012-10-12 | 2013-03-06 | 华映视讯（吴江）有限公司 | Touch panel and driving method thereof |
| CN103326703A (en) * | 2013-06-14 | 2013-09-25 | 深圳欧菲光科技股份有限公司 | Key module and touch electronic device with same |
| CN103593097A (en) * | 2012-11-29 | 2014-02-19 | 敦泰科技有限公司 | Terminal equipment and touch detection system thereof |
| WO2015081719A1 (en) * | 2013-12-04 | 2015-06-11 | 深圳市汇顶科技股份有限公司 | Touch detection system, detection method thereof, and touch screen terminal |
| CN105320387A (en) * | 2014-08-01 | 2016-02-10 | 三星电子株式会社 | Semiconductor device and method of operating the same |
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| CN101833121A (en) * | 2010-04-09 | 2010-09-15 | 深圳市汇顶科技有限公司 | Double-coupling detection circuit, rain sensor and rain identification method |
| WO2010111668A1 (en) * | 2009-03-26 | 2010-09-30 | Cypress Semiconductor | Multi-functional capacitance sensing circuit with a current conveyor |
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| WO2010111668A1 (en) * | 2009-03-26 | 2010-09-30 | Cypress Semiconductor | Multi-functional capacitance sensing circuit with a current conveyor |
| CN101833121A (en) * | 2010-04-09 | 2010-09-15 | 深圳市汇顶科技有限公司 | Double-coupling detection circuit, rain sensor and rain identification method |
| CN202058127U (en) * | 2010-12-29 | 2011-11-30 | 广东中显科技有限公司 | Touch sensitive circuit |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102955634A (en) * | 2012-10-12 | 2013-03-06 | 华映视讯（吴江）有限公司 | Touch panel and driving method thereof |
| CN103593097A (en) * | 2012-11-29 | 2014-02-19 | 敦泰科技有限公司 | Terminal equipment and touch detection system thereof |
| CN103593097B (en) * | 2012-11-29 | 2017-03-01 | 敦泰科技有限公司 | A kind of touch detecting system of terminal unit and terminal unit |
| CN103326703A (en) * | 2013-06-14 | 2013-09-25 | 深圳欧菲光科技股份有限公司 | Key module and touch electronic device with same |
| WO2015081719A1 (en) * | 2013-12-04 | 2015-06-11 | 深圳市汇顶科技股份有限公司 | Touch detection system, detection method thereof, and touch screen terminal |
| CN105320387A (en) * | 2014-08-01 | 2016-02-10 | 三星电子株式会社 | Semiconductor device and method of operating the same |
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