CN104199581B - One kind is based on big CTP, little CTPCapacitive detection circuit and capacitance detecting device - Google Patents
One kind is based on big CTP, little CTPCapacitive detection circuit and capacitance detecting device Download PDFInfo
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- CN104199581B CN104199581B CN201410437122.7A CN201410437122A CN104199581B CN 104199581 B CN104199581 B CN 104199581B CN 201410437122 A CN201410437122 A CN 201410437122A CN 104199581 B CN104199581 B CN 104199581B
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Abstract
The present invention relates to electronic applications, disclose a kind of based on big CTP, little CTPCapacitive detection circuit and capacitance detecting device.In the present invention, comprising：Electric capacity C on screenTP, feedback capacity CfWith an operational amplifier；Also include：Programmable capacitor array Cs, the first charge switch, the second charge switch, the first change-over switch and the second change-over switch；CTPOne end be connected with the first bias voltage by the first charge switch, and be connected with the negative input end of operational amplifier by the first change-over switch, CTPThe other end ground connection；One end of Cs is connected with the second bias voltage by the second charge switch, and is connected with the negative input end of operational amplifier by the second change-over switch, the other end ground connection of Cs；Wherein, the first bias voltage is less than the second bias voltage.The output common mode level of amplifier is adjusted by the Cs for increasing newly, expands the output common mode level amplitude of oscillation, improve capacitance detecting sensitivity.
Description
Technical field
The present invention relates to electronic applications, are more particularly to based on big CTPCapacitive detection circuit, be based on little CTPCapacitance detecting
Circuit and capacitance detecting device.
Background technology
In recent years, capacitive touch screen is simple to operation due to which, and light transmittance is high, and the advantage such as wear-resisting, in intelligent terminal
Design in find broad application, such as single-touch, multiple point touching etc..Capacitive touch screen is mainly by detecting the upper electric capacity of screen
Change detecting whether the generation of touch.With the development of capacitance technology, its sensitivity and precision are proposed higher
Requirement, how accurately to judge the position of slight touch point become be currently needed for solve problem.
In prior art, as shown in figure 1, detection circuit mainly includes a screen above electric capacity CTP, feedback capacity CfAnd one
Individual operational amplifier 101, capacitance detecting process are broadly divided into charging and conversion both of which, are opened using charge switch 104, conversion
Pass 105 and charge switch 106 are controlled.Specifically, in charge mode, charge switch 104 and charge switch 106 are closed,
Change-over switch 105 is opened, the connection of its circuit as shown in Fig. 2 in this pattern, built-in bias voltage VTPElectric capacity C upper to screenTPCarry out
Charge, and feedback capacity CfIn cleared condition；And in translative mode, charge switch 104 and charge switch 106 are opened, turn
Change switch 105 to close, circuit structure is output as shown in figure 3, can obtain amplifier using law of conservation of charge：
If now shielding upper capacitance variations △ CTP, the exporting change of amplifier is：
Due in actual design application, it is contemplated that the finished product of chip, CTPC will be much larger thanf, soValue just
Larger, and due to VOUTExcursion be (0, V to the maximumDD), can be obtained according to above formula (1), be to ensure VOUTWithout departing from amplifier
Output area, (VTP-VCM) very little is needed, further according to △ Q=(VCM-VTP)△CTPCan obtain, the excursion of △ Q i.e. can be due to
(VTP-VCM) restriction and become very little so that touch detection when input signal-to-noise ratio reduce, antijamming capability decline, cause electricity
Hold the sensitvity constraint of detection.
Content of the invention
It is an object of the invention to provide a kind of be based on big CTP, little CTPCapacitive detection circuit and capacitance detecting device, make
Obtain capacitive detection circuit and can expand the output common mode level amplitude of oscillation, improve capacitance detecting sensitivity.
For solving above-mentioned technical problem, embodiments of the present invention provide a kind of based on big CTPCapacitive detection circuit,
Comprising：Electric capacity C on screenTP, feedback capacity Cf and an operational amplifier；Described based on big CTPCapacitive detection circuit also include：Can
Programming capacitor array Cs, the first charge switch, the second charge switch, the first change-over switch and the second change-over switch；
The CTPOne end be connected with the first bias voltage by first charge switch, and change by described first
Switch is connected with the negative input end of the operational amplifier, the CTPThe other end ground connection；
One end of the Cs is connected with the second bias voltage by second charge switch, and is changed by described second
Switch is connected with the negative input end of the operational amplifier, the other end ground connection of the Cs；
Wherein, first bias voltage is less than second bias voltage.
Embodiments of the present invention additionally provide a kind of based on little CTPCapacitive detection circuit, comprising：Electric capacity C on screenTP、
Feedback capacity Cf and an operational amplifier；Described based on little CTPCapacitive detection circuit also include：Programmable capacitor array Cs,
One charge switch, the second charge switch, the first change-over switch and the second change-over switch；
The CTPOne end be connected with the second bias voltage by first charge switch, and change by described first
Switch is connected with the negative input end of the operational amplifier, the CTPThe other end ground connection；
One end of the Cs is connected with the first bias voltage by second charge switch, and is changed by described second
Switch is connected with the negative input end of the operational amplifier, the other end ground connection of the Cs；
Wherein, first bias voltage is less than second bias voltage.
Embodiments of the present invention additionally provide a kind of capacitance detecting device, comprising：Big C is based on described aboveTPElectric capacity
Detect circuit and be based on little C described aboveTPCapacitive detection circuit, also include a selector；
Electric capacity C on screenTPValue of the value more than programmable capacitor array Cs when, selector connection is described based on big
CTPCapacitive detection circuit；
Electric capacity C on screenTPValue of the value less than programmable capacitor array Cs when, selector connection is described based on little
CTPCapacitive detection circuit.
Embodiment of the present invention in terms of existing technologies, increased programmable capacitor array Cs, in capacitance detecting
Charging stage, using different bias voltages to CTPCharged with Cs respectively, in the conversion stage of capacitance detecting, it is possible to use Cs inhales
Receive the upper electric capacity C of screenTPPartial charge, the output common mode level of amplifier is adjusted with this, expands the output common mode level amplitude of oscillation, improve electricity
Hold detection sensitivity.
As improving further, described based on big CTPCapacitive detection circuit also include：3rd charge switch, the 4th charge
Switch and the 3rd change-over switch；One end of the Cf is by the 3rd charge switch ground connection, and is opened by the 3rd conversion
Close and be connected with the negative input end of the operational amplifier, the other end of the Cf is by the 4th charge switch and the computing
The negative input end connection of amplifier.
The connection of Cf is adjusted using charge switch and change-over switch so that in the charging stage, using the output voltage of amplifier
Charge for Cf, Cf is reversed the certain electricity of preliminary filling, can expand the excursion of output common mode level further.
As improving further, described based on big CTPCapacitive detection circuit also include：5th charge switch, the 6th charge
Switch, the 7th charge switch, the 4th change-over switch and the 5th change-over switch；One end of the Cf passes through the 5th charge switch
Ground connection, and be connected with the negative input end of the operational amplifier by the 4th change-over switch；The other end of the Cf passes through
6th charge switch connects the 3rd bias voltage Vs, and defeated with the operational amplifier by the 5th change-over switch
Go out end connection；By the 7th charge switch connection between the negative input end of the operational amplifier and output end.
The connection of Cf is adjusted using charge switch and change-over switch so that in the charging stage, using a controlled biased electrical
Pressure Vs is charged for Cf, and Cf is reversed the certain electricity of preliminary filling, while the excursion of output common mode level is expanded further, is made
Obtain excursion more controlled.
Description of the drawings
Fig. 1 be according to the capacitive detection circuit structure chart in background technology；
Fig. 2 is the charged state structure chart according to the capacitive detection circuit in background technology；
Fig. 3 is the transition status structure chart according to the capacitive detection circuit in background technology；
Fig. 4 be according to based on big C in first embodimentTPCapacitive detection circuit structure chart；
Fig. 5 be according to based on big C in first embodimentTPCapacitive detection circuit charged state structure chart；
Fig. 6 be according to based on big C in first embodimentTPCapacitive detection circuit transition status structure chart；
Fig. 7 be according to based on big C in second embodimentTPCapacitive detection circuit structure chart；
Fig. 8 be according to based on big C in the 3rd embodimentTPCapacitive detection circuit structure chart；
Fig. 9 be according to based on little C in the 4th embodimentTPCapacitive detection circuit structure chart；
Figure 10 be according to based on little C in the 5th embodimentTPCapacitive detection circuit structure chart；
Figure 11 be according to based on little C in the 6th embodimentTPCapacitive detection circuit structure chart；
Figure 12 be according to the capacitance detecting device structured flowchart in the 7th embodiment；
Figure 13 be according to the capacitance detecting device circuit structure diagram in the 7th embodiment.
Specific embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with each reality of the accompanying drawing to the present invention
The mode of applying is explained in detail.However, it will be understood by those skilled in the art that in each embodiment of the present invention,
In order that reader more fully understands the application and proposes many ins and outs.But, even if there is no these ins and outs and base
Many variations and modification in following embodiment, it is also possible to realize each claim of the application technical side required for protection
Case.
It was found by the inventors of the present invention that in existing capacitive detection circuit application, the corresponding electric capacity of different touch screens
CTPChange greatly, for make the present invention with wider range of application.Can make full use of to CTPThe regulation of charging level,
So that the capacitance range of detection is maximum.Further, since when the upper electric capacity of screen is larger or smaller, the excursion of its output common mode level
May be different, if design is for the capacitive detection circuit of the upper capacitance of different screens, you can fully amplify the defeated of operational amplifier
Go out dynamic range, and as tester can rule of thumb know that capacitance is substantially greatly still on the screen of the capacitance plate of application
Little, so according to capacitance value on different screens, different capacitive detection circuits are designed, can effectively expand output common mode electricity
Flat excursion.
The first embodiment of the present invention is related to a kind of based on big CTPCapacitive detection circuit, its circuit structure such as Fig. 4 institute
Show, specifically include：Electric capacity C on screenTP, feedback capacity Cf, operational amplifier 101, resistance 102, electric capacity 103, programmable capacitor battle array
Row Cs, the first charge switch 201, the second charge switch 203, charge switch 205, the first change-over switch 202 and the second conversion are opened
Close 204.
In present embodiment based on big CTPCapacitive detection circuit specifically connection is as follows：Resistance 102 is connected to computing and puts
101 positive input terminal of big device and bias voltage VCMBetween, electric capacity 103 is connected between 101 positive input terminal of operational amplifier and earth terminal；
Cf is connected between the negative input end of operational amplifier 101 and output end, while charge switch 205 to be connected in parallel on the two ends of Cf；
CTPOne end be connected with the first bias voltage V1 by the first charge switch 201, and put with computing by the first change-over switch 202
The negative input end connection of big device 101, CTPThe other end ground connection；One end of Cs is by the second charge switch 203 and the second biased electrical
Pressure V2 connection, and be connected with the negative input end of operational amplifier 101 by the second change-over switch 204, the other end ground connection of Cs.Need
It is noted that the first bias voltage V1 in present embodiment is less than the second bias voltage V2.
In actual applications, in the charging stage, respectively the first charge switch 201, the second charge switch 203 and charging are opened
Close 205 to close, the first change-over switch 202 and the second change-over switch 204 are opened, and circuit construction variations are as shown in Figure 5；Now,
CTPIt is connected between the first bias voltage V1 and earth terminal, two terminal shortcircuit of Cf connects, the first bias voltage V1 is CTPCharge, the
Two bias voltage V2 are charged for Cs, while Cf resets.In the conversion stage, respectively by the first charge switch 201, the second charge switch
203 and charge switch 205 open, the first change-over switch 202 and the second change-over switch 204 are closed, circuit construction variations be as Fig. 6
Shown；CTPIt is connected between negative input end and the earth terminal of operational amplifier 101, Cs is connected to the negative defeated of operational amplifier 101
Enter between end and earth terminal, Cf is connected directly between the negative input end of operational amplifier 101 and output end, CTPElectric charge difference
It is transferred to Cf and Cs.
Specifically, in present embodiment based on big CTPCapacitive detection circuit conversion the stage, according to charge conservation
Final amplifier output such as following formula (3) can be obtained with the short characteristic of the void of amplifier：
If capacitance variations are C on screenTP+△CTP, the exporting change of amplifier is following formula (4)
The upper electric capacity C of screen be can be seen that from above formula (3) formulaTPA part of electric charge will be by capacitor array CsTo absorb, thus fortune
The output common mode level that puts simply can be adjusted, that is, by adjusting CsSize carry out the DC operation state of bucking circuit
Restriction to output common mode level.Therefore, when circuit carries out detection work, need to programmable capacitor array CsCarry out
One initialized " frequency modulation " process, its purpose is exactly in order that amplifier is output as common mode electrical level VCM, that is, so that in formula (3)
VOUT=VCM.Now, above formula (4) i.e. alterable is following formula (5)：
(V thereinCM-V1) can be unrestricted and increase, that is to say, that the change of output common mode level will not receive circuit
DC operation state limit and expand, also just improve the sensitivity of capacitive detection circuit.
Further, since VOUT=VCM, following formula (6) is obtained：
In the present embodiment, typically big CTPIt is interpreted as that its capacitance meets CTP>Cs, its dynamic output range be from VCM
To VDD, you can with by reducing common mode electrical level VCMTo adjust the direct-current working volts of amplifier.
As an example it is assumed that now CTP=80pF (capacitance is larger), meanwhile, V can be set1=0, V2=VDD, VCM=
VDD/ 3, Cs=40pF comes so that amplifier output VOUT=VCM.Hereafter, when there is finger to touch, on screen, electric capacity increases △ CTP, amplifier is defeated
Go out to increaseDue to now common mode electrical level VCM=VDD/ 3, the dynamic detection range of its output is from VDD/3
To VDD, maximum can have 2*VDD/ 3 variable quantity, thus can be by adjusting CfTo strengthen the sensitivity of detection, according to above formula (5)
Understand, its size is：
Wherein, △ CTP,maxFor the amplitude of variation that the upper electric capacity of screen is maximum.
Final electric capacity can be obtained to the conversion gain of voltage is
Present embodiment in terms of existing technologies, increased programmable capacitor array Cs, in the charging of capacitance detecting
Stage, using different bias voltages to CTPCharged with Cs respectively, in the conversion stage of capacitance detecting, it is possible to use Cs absorbing screen
Upper electric capacity CTPPartial charge, shadow of the circuit direct working condition to the out-put dynamic range of capacitive detection circuit is eliminated with this
Ring, the output common mode level of amplifier is adjusted, expand the output common mode level amplitude of oscillation, improve detection sensitivity.
Second embodiment of the present invention is related to a kind of based on big CTPCapacitive detection circuit.Second embodiment be
Do on the basis of one embodiment and improved further, mainly theed improvement is that：In the charging stage of first embodiment,
Two terminal shortcircuit of Cf connects so that Cf resets.And in second embodiment of the invention, adjusted using charge switch and change-over switch
The connection of Cf so that in the charging stage, charged for Cf using the output voltage of amplifier, Cf is reversed the certain electricity of preliminary filling, permissible
Expand the excursion of output common mode level further.
Specifically, in present embodiment based on big CTPCapacitive detection circuit as shown in fig. 7, also including：3rd fills
Electric switch 206, the 4th charge switch 208 and the 3rd change-over switch 207；One end of Cf is grounded by the 3rd charge switch 206, and
It is connected with the negative input end of operational amplifier 101 by the 3rd change-over switch 207, the other end of Cf passes through the 4th charge switch
208 are connected with the negative input end of operational amplifier 101.
As Cf was connected between the output and ground of amplifier in the charging stage, that is, in charging stage, Cf
The reverse electric charge by preliminary filling, the short characteristic of void also according to charge conservation and amplifier can be obtained, VOUTChange lower limit will more
Low, its excursion is also just bigger, is based on big C in present embodimentTPThe sensitivity of capacitive detection circuit will be higher.
Third embodiment of the present invention also relates to a kind of based on big CTPCapacitive detection circuit.3rd embodiment is
Do on the basis of first embodiment and improved further, mainly theed improvement is that：In the first embodiment, charge
Two terminal shortcircuit of stage Cf connects so that Cf resets.And in third embodiment of the invention, using controlled bias voltage Vs be
Cf charges, and Cf is reversed the certain electricity of preliminary filling, while the excursion of output common mode level is expanded further so that change
Scope is more controlled.
It was found by the inventors of the present invention that in this second embodiment, although the output of amplifier has been adjusted to (VCM~
VDD), its amplitude of oscillation still leaves certain allowance, can be by making full use of CfThe quantity of electric charge of pre- punching, so that increase output further
The amplitude of oscillation.
Specifically, in present embodiment based on big CTPCapacitive detection circuit as shown in figure 8, also including：5th fills
Electric switch 212, the 6th charge switch 210, the 7th charge switch 213, the 4th change-over switch 209 and the 5th change-over switch 211.Its
In, one end of Cf is grounded by the 5th charge switch 212, and negative defeated with operational amplifier 101 by the 4th change-over switch 209
Enter end connection；The other end of Cf connects the 3rd bias voltage Vs by the 6th charge switch 210, and passes through the 5th change-over switch
211 are connected with the output end of operational amplifier 101；Fill by the 7th between the negative input end of operational amplifier 101 and output end
Electric switch 213 connects.
Similar to second embodiment, as Cf was connected between the output and ground of amplifier in the charging stage,
Namely in the charging stage, Cf reverse electric charge by preliminary filling, the short characteristic of void also according to charge conservation and amplifier can be by
Above formula (3) change is turned to：
It can be seen that, the output of amplifier is changed into (VCM-VS～VDD), VOUTLower limit will be lower, its excursion is also just bigger, spirit
Sensitivity is improved further.
For example, if now setting VCM=VS=VDD/ 2, the amplitude of oscillation of amplifier can reach (0～VDD).
4th embodiment of the present invention is related to a kind of based on little CTPCapacitive detection circuit, its circuit structure such as Fig. 9 institute
Show, specifically include：Electric capacity C on screenTP, feedback capacity Cf, operational amplifier 101, resistance 102, electric capacity 103, programmable capacitor battle array
Row Cs, the first charge switch 201, the second charge switch 203, charge switch 205, the first change-over switch 202 and the second conversion are opened
Close 204.
Due in present embodiment capacitive detection circuit be based on little CTPCapacitive detection circuit, its attachment structure and first
Embodiment is compared, differ only in the charging stage by the second bias voltage V2 be CTPCharge, by the first bias voltage V1 be
Cs charges, due in little CTPDetection under the premise of, be ensure amplifier normal work, it is required that be CTPThe biased electrical of charging
Pressure is more than the bias voltage charged for Cs.Other attachment structures are similar all with first embodiment with design principle, and here is not
Repeat again.
5th embodiment of the present invention is related to a kind of based on little CTPCapacitive detection circuit.5th embodiment be
Do on the basis of four embodiments and improved further, mainly theed improvement is that：In the 4th embodiment, charging stage Cf
Two terminal shortcircuits connect so that Cf resets.And in fifth embodiment of the invention, Cf is adjusted using charge switch and change-over switch
Connection so that in the charging stage, be that Cf charges using the output voltage of amplifier, Cf is reversed the certain electricity of preliminary filling, Ke Yijin
One step expands the excursion of output common mode level.
Specifically, in present embodiment based on little CTPCapacitive detection circuit circuit as shown in Figure 10, its connection
Structure is roughly the same with the Fig. 7 in second embodiment, differs primarily in that, in present embodiment, based on little CTPElectric capacity inspection
Slowdown monitoring circuit also includes：3rd charge switch 206, the 4th charge switch 208 and the 3rd change-over switch 207；One end of Cf is by the
Three charge switch are grounded, and are connected with the negative input end of operational amplifier by the 3rd change-over switch, and the other end of Cf passes through the
Four charge switch are connected with the negative input end of operational amplifier.In charging stage, it is CTPThe bias voltage of charging is more than filling for Cs
The bias voltage of electricity.That is, in the charging stage, being charged for Cf using the output voltage of amplifier, it is certain that Cf is reversed preliminary filling
Electricity；In the conversion stage, its connection is identical with the Fig. 6 in first embodiment, according to the short characteristic of the void of charge conservation and amplifier
Final amplifier can be obtained be output as：
Now, if the upper capacitance variations of screen are CTP+△CTP, the exporting change of amplifier is：
Now for adjusting amplifier output common mode level, it is required that CsMeet：
As an example it is assumed that the capacitance size for needing detection is CTP=20pF, can now arrange V1=0, V2=VDD, VCM
=VDD/ 3, Cs=40pF comes so that amplifier output VOUT=2*VCM.From (8) if formula can be seen that now shields upper electric capacity increase △
CTP, amplifier output will reductionAs amplifier output DC level now is 2*VDD/ 3, its output still has
2*VDD/ 3 dynamic detection range, feedback capacity C nowfSize could be arranged to：
Wherein △ CTP,maxThe amplitude of variation maximum for now shielding upper electric capacity.
If setting VCM=VDD/ 2, then the output voltage swing of amplifier can reach from VDDTo 0 maximum magnitude.
6th embodiment of the present invention also relates to a kind of based on little CTPCapacitive detection circuit.6th embodiment is
Do further on the basis of the 4th embodiment and improved, mainly theed improvement is that：Charging rank in the 4th embodiment
Two terminal shortcircuit of Duan Zhong, Cf connects so that Cf resets.And in the charging stage in sixth embodiment of the invention, using controlled
Bias voltage Vs be that Cf charges, Cf is reversed the certain electricity of preliminary filling, in the excursion for expanding output common mode level further
While so that excursion is more controlled.
Specifically, in present embodiment based on little CTPCapacitive detection circuit as shown in figure 11, its attachment structure with
Fig. 8 in 3rd embodiment is roughly the same, differs primarily in that, in present embodiment based on little CTPCapacitance detecting electricity
Road also includes：5th charge switch 212, the 6th charge switch 210, the 7th charge switch 213, the 4th change-over switch 209 and
Five change-over switches 211.Wherein, one end of Cf is grounded by the 5th charge switch 212, and by the 4th change-over switch 209 and fortune
Calculate the negative input end connection of amplifier 101；The other end of Cf connects the 3rd bias voltage Vs by the 6th charge switch 210, and
It is connected with the output end of operational amplifier 101 by the 5th change-over switch 211；The negative input end of operational amplifier 101 and output
Connected by the 7th charge switch 213 between end.In charging stage, it is CTPThe bias voltage of charging is more than the biasing that charges for Cs
Voltage.
That is, in the charging stage, being charged for Cf using a 3rd controlled bias voltage Vs；In the conversion stage, its
Connection is identical with the Fig. 6 in first embodiment, can be obtained according to the short characteristic of the void of charge conservation and amplifier, VOUTChange
Lower limit will be controlled while lower, and its excursion is also just bigger, and sensitivity is improved further.
7th embodiment of the present invention is related to a kind of capacitance detecting device.Its structured flowchart as shown in figure 12, is specifically wrapped
Contain：As first embodiment, to the 3rd embodiment, any one is based on big CTPCapacitive detection circuit and as the 4th embodiment party
To the 6th embodiment, any one is based on little C to formulaTPCapacitive detection circuit, also include a selector.Whole using selector
Close and be based on big CTPCapacitive detection circuit and be based on little CTPCapacitive detection circuit so that capacitance detecting chips production when, its
In components and parts can be multiplexed in a large number, it is also possible to according to different CTPValue, flexibly changes capacitive detection circuit, expands which
Application scenarios.
Specifically, electric capacity C on screenTPValue of the value more than programmable capacitor array Cs when, selector connection is based on big
CTPCapacitive detection circuit；Electric capacity C on screenTPValue of the value less than programmable capacitor array Cs when, selector connection is based on little
CTPCapacitive detection circuit.
It should be noted that as capacitance measurement technique personnel can rule of thumb know CTPThe approximate range of value, also may be used
To realize the function of selector in present embodiment using analog switch, in present embodiment, with using in first embodiment
Based on big CTPCapacitive detection circuit and the 4th embodiment in based on little CTPCapacitive detection circuit as a example by, its structure
As shown in figure 13, specifically, the selector 30 in present embodiment can include：First switch 301, second switch 302,
3rd switch 303 and the 4th switch 304；Wherein, the second bias voltage V2 is by first switch 301 and the first charge switch 201
Connection, the second bias voltage V2 are connected with the second charge switch 203 by second switch 302；First bias voltage V1 is by the
Three switches 303 are connected with the first charge switch 201, and the second bias voltage V2 is by the 4th switch 304 and the second charge switch 203
Connection.
In actual applications, close in second switch 302 and the 3rd switch 303, first switch 301 and the 4th switchs 304
When opening, the first capacitive detection circuit is connected；Open in second switch 302 and the 3rd switch 303, first switch 301 and the 4th
When switch 304 is closed, the second capacitive detection circuit is connected.
It is noted that the selector in present embodiment can also be realized using digital control scheme, first to CTPValue enter
Row detection, judges its size, then connects different capacitive detection circuits.
It will be understood by those skilled in the art that the respective embodiments described above are to realize the specific embodiment of the present invention,
And in actual applications, can to which, various changes can be made in the form and details, without departing from the spirit and scope of the present invention.
Claims (8)
1. a kind of based on big CTPCapacitive detection circuit, comprising：Electric capacity C on screenTP, feedback capacity Cf and an operational amplifier；Its
It is characterised by, described based on big CTPCapacitive detection circuit also include：Programmable capacitor array Cs, the first charge switch, second
Charge switch, the first change-over switch and the second change-over switch；Wherein, the CTPValue more than the Cs value；
The CTPOne end be connected with the first bias voltage by first charge switch, and pass through first change-over switch
It is connected with the negative input end of the operational amplifier, the CTPThe other end ground connection；
One end of the Cs is connected with the second bias voltage by second charge switch, and passes through second change-over switch
It is connected with the negative input end of the operational amplifier, the other end ground connection of the Cs；
Wherein, first bias voltage is less than second bias voltage.
2. according to claim 1 based on big CTPCapacitive detection circuit, it is characterised in that described based on big CTPElectric capacity
Detection circuit also includes：3rd charge switch, the 4th charge switch and the 3rd change-over switch；
One end of the Cf is by the 3rd charge switch ground connection, and passes through the 3rd change-over switch and the operation amplifier
The negative input end connection of device, the other end of the Cf pass through the negative input end of the 4th charge switch and the operational amplifier
Connection.
3. according to claim 1 based on big CTPCapacitive detection circuit, it is characterised in that described based on big CTPElectric capacity
Detection circuit also includes：5th charge switch, the 6th charge switch, the 7th charge switch, the 4th change-over switch and the 5th conversion
Switch；
One end of the Cf is by the 5th charge switch ground connection, and passes through the 4th change-over switch and the operation amplifier
The negative input end connection of device；
The other end of the Cf connects the 3rd bias voltage Vs by the 6th charge switch, and is opened by the 5th conversion
Close and be connected with the output end of the operational amplifier；
By the 7th charge switch connection between the negative input end of the operational amplifier and output end.
4. a kind of based on little CTPCapacitive detection circuit, comprising：Electric capacity C on screenTP, feedback capacity Cf and an operational amplifier；Its
It is characterised by, described based on little CTPCapacitive detection circuit also include：Programmable capacitor array Cs, the first charge switch, second
Charge switch, the first change-over switch and the second change-over switch；Wherein, the CTPValue less than the Cs value；
The CTPOne end be connected with the second bias voltage by first charge switch, and pass through first change-over switch
It is connected with the negative input end of the operational amplifier, the CTPThe other end ground connection；
One end of the Cs is connected with the first bias voltage by second charge switch, and passes through second change-over switch
It is connected with the negative input end of the operational amplifier, the other end ground connection of the Cs；
Wherein, first bias voltage is less than second bias voltage.
5. according to claim 4 based on little CTPCapacitive detection circuit, it is characterised in that described based on little CTPElectric capacity
Detection circuit also includes：3rd charge switch, the 4th charge switch and the 3rd change-over switch；
One end of the Cf is by the 3rd charge switch ground connection, and passes through the 3rd change-over switch and the operation amplifier
The negative input end connection of device, the other end of the Cf pass through the negative input end of the 4th charge switch and the operational amplifier
Connection.
6. according to claim 4 based on little CTPCapacitive detection circuit, it is characterised in that described based on little CTPElectric capacity
Detection circuit also includes：5th charge switch, the 6th charge switch, the 7th charge switch, the 4th change-over switch and the 5th conversion
Switch；
One end of the Cf is by the 5th charge switch ground connection, and passes through the 4th change-over switch and the operation amplifier
The negative input end connection of device；
The other end of the Cf connects the 3rd bias voltage Vs by the 6th charge switch, and is opened by the 5th conversion
Close and be connected with the output end of the operational amplifier；
By the 7th charge switch connection between the negative input end of the operational amplifier and output end.
7. a kind of capacitance detecting device, it is characterised in that include：As described in any one in claims 1 to 3 based on big CTP
Capacitive detection circuit and as described in any one in claim 4 to 6 based on little CTPCapacitive detection circuit, also include one
Selector；
Electric capacity C on screenTPValue of the value more than programmable capacitor array Cs when, selector connection is described to be based on big CTPElectricity
Hold detection circuit；
Electric capacity C on screenTPValue of the value less than programmable capacitor array Cs when, selector connection is described to be based on little CTPElectricity
Hold detection circuit.
8. capacitance detecting device according to claim 7, it is characterised in that the selector includes：First switch, second
Switch, the 3rd switch and the 4th switch；
Second bias voltage is connected with first charge switch by the first switch, and second bias voltage leads to
Cross the second switch to be connected with second charge switch；
First bias voltage is connected with first charge switch by the 3rd switch, and second bias voltage leads to
Cross the described 4th switch to be connected with second charge switch.
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| CN201410437122.7A CN104199581B (en) | 2014-08-29 | 2014-08-29 | One kind is based on big CTP, little CTPCapacitive detection circuit and capacitance detecting device |
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| CN106553431B (en) * | 2016-10-25 | 2018-09-04 | 爱司凯科技股份有限公司 | The plate adjustment of the printing plate of CTP platemaking machine detection circuit and detection method in place |
| EP3591507B1 (en) * | 2018-03-30 | 2023-11-22 | Shenzhen Weitongbo Technology Co., Ltd. | Capacitive detection circuit, touch detection apparatus, and terminal device |
| US10581431B2 (en) * | 2018-04-06 | 2020-03-03 | Qualcomm Incorporated | Self capacitance drive offset cancellation in touch controller integrated circuits |
| KR102611016B1 (en) | 2018-12-26 | 2023-12-07 | 엘지디스플레이 주식회사 | Touch display and driving method for the same |
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| US20080191714A1 (en) * | 2007-02-08 | 2008-08-14 | Denso Corporation | Capacitive physical quantity detection device |
| CN101556297A (en) * | 2008-04-08 | 2009-10-14 | 瑞鼎科技股份有限公司 | Capacitance value measuring circuit and measuring method thereof |
| TW201118387A (en) * | 2009-11-19 | 2011-06-01 | Raydium Semiconductor Corp | Capacitance measurement circuit and method therefor |
| TW201337279A (en) * | 2012-03-05 | 2013-09-16 | Mstar Semiconductor Inc | Device for detecting capacitance and capacitive-type touch control system utilizing the same |
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| JP2013088382A (en) * | 2011-10-21 | 2013-05-13 | Asahi Kasei Electronics Co Ltd | Electrostatic capacitance detection circuit and signal processing circuit for touch sensor |
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| US20080191714A1 (en) * | 2007-02-08 | 2008-08-14 | Denso Corporation | Capacitive physical quantity detection device |
| CN101556297A (en) * | 2008-04-08 | 2009-10-14 | 瑞鼎科技股份有限公司 | Capacitance value measuring circuit and measuring method thereof |
| TW201118387A (en) * | 2009-11-19 | 2011-06-01 | Raydium Semiconductor Corp | Capacitance measurement circuit and method therefor |
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