CN110212880A - A kind of charge amplifier circuit and its sequential control method - Google Patents
A kind of charge amplifier circuit and its sequential control method Download PDFInfo
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- CN110212880A CN110212880A CN201910597564.0A CN201910597564A CN110212880A CN 110212880 A CN110212880 A CN 110212880A CN 201910597564 A CN201910597564 A CN 201910597564A CN 110212880 A CN110212880 A CN 110212880A
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Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/70—Charge amplifiers
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/22—Modifications for ensuring a predetermined initial state when the supply voltage has been applied
Abstract
The invention discloses a kind of charge amplifier circuits, including first capacitor Cb, the second capacitor Cf, operational amplifier U1, first switch P1, second switch P2, third switch P3, the 4th switch P4, the 5th switch P5, the 6th switch P6 and the 7th switch P7.The invention also discloses the sequential control methods of charge amplifier circuit.Charge amplifier circuit and its sequential control method of the present invention are by changing the first control phase to the steady state voltage of the first capacitor Cb voltage to charge and the second pole plate of the second control phase first capacitor Cb, so that in certain first capacitor Cb, the second capacitor Cf, increase supported screen body self-capacitance range, optimize circuit performance, physical layout area is reduced, the cost of single chip is reduced.
Description
Technical field
The present invention relates to amplifier circuit technical field more particularly to a kind of charge amplifier circuit and its timing control sides
Method.
Background technique
In recent years, as the quick of intelligent terminal (smart phone, Intelligent flat etc.) is popularized, touch screen control technology is rapid
Development.Touch screen perceives the touch of finger, and the touch signal of finger is converted into voltage signal, is given after carrying out signal processing
Layer control system, top level control system calculate the movement of identification finger by algorithm and make respective feedback.Currently, being widely used
Touch screen there are mainly two types of: touch screens and capacitance plate, with technology make rapid progress development, capacitance plate increasingly occupies leading
Status.In capacitor screen system, the touch of finger from electrology characteristic for be capacitor variation, capacitor be store charge electricity
Road basic unit, therefore, perceiving the touch of finger its essence is exactly the change for perceiving the variable quantity of charge and converting thereof into voltage
Change amount.Charge amplifier is exactly a kind of device, circuit or the device that charge signal is converted into voltage signal, is had been widely used
In various sensors.
In IC design field, the physical layout area of circuit directly determines the cost of single chip, is design
One important indicator.Charge amplifier in the prior art, to support biggish screen body self-capacitance, need inside charge amplifier
Two capacitors used are also bigger, and big capacitor occupies biggish physical layout area, increase chip cost.Therefore,
Study how to reduce its physical layout area necessary under the premise of not significantly reducing charge amplifier circuit performance.
Summary of the invention
The technical problem to be solved in the present invention is that in view of the above drawbacks of the prior art, providing a kind of charge amplifier
Circuit and its sequential control method.
The technical solution adopted by the present invention to solve the technical problems is: it is according to an aspect of the present invention, a kind of electricity is provided
Lotus amplifier circuit, comprising: first capacitor Cb, the second capacitor Cf, operational amplifier U1, first switch P1, second switch P2,
Three switch P3, the 4th switch P4, the 5th switch P5, the 6th switch P6 and the 7th switch P7；
Specifically, the first pole of the one end first switch P1 and the one end second switch P2 with the screen body self-capacitance Cs of touch screen
Plate connection, first switch P1 other end ground connection, the second switch P2 other end and the one end third switch P3, the 4th one end switch P4 and
The first pole plate of first capacitor Cb connects, and the 4th switch P4 other end is connect with the first reference voltage V1, and the of first capacitor Cb
Two pole plates are connect with the 5th one end switch P5 and the 6th one end switch P6, the 5th switch P5 other end ground connection, and the 6th switch P6 is another
One end is connect with the first reference voltage V1；
Specifically, the first pole of the third switch P3 other end and operational amplifier U1 inverting input terminal Vn, the second capacitor Cf
Plate and the 7th one end switch P7 are all connected with, and operational amplifier U1 non-inverting input terminal Vp is connect with the second reference voltage V2, and operation is put
The second pole plate and the 7th switch P7 other end of big device U1 output end vo and the second capacitor Cf are all connected with as circuit output end Vo3；
The first reference voltage V1 and the second reference voltage V2 are unequal.
Preferably, when first switch P1, the 4th switch P4, the 5th switch P5 and the 7th switch P7 are connected, and second switch
When P2, third switch P3 and the 6th switch P6 are disconnected, for the first control phase；
When first switch P1, the 4th switch P4, the 5th switch P5 and the 7th switch P7 are disconnected, and second switch P2, third
When switch P3 and the 6th switch P6 is connected, for the second control phase.
It preferably, further include third control phase rank between the first control phase and the second control phase
Section；
When second switch P2 and the 5th switch P5 are connected, and first switch P1, third switch P3, the 4th switch P4, the
When six switch P6 and the 7th switch P7 are disconnected, phase is controlled for third.
Preferably, phase is controlled first, the first reference voltage V1 charges to first capacitor Cb, charging complete
Afterwards, the charge of the first pole plate of first capacitor Cb is Q3, Q3Calculation formula are as follows:
Q3=V1*Cb (1)
Phase is controlled second, the quantity of electric charge of the first pole plate of first capacitor Cb is Q4, Q4Calculation formula are as follows:
Q4=V2*CS+(V2-VO3)*Cf+(V2-V1)*Cb (2)
According to law of conservation of charge, Q3=Q4, Vo3, the calculation formula of Vo3 are calculated according to calculation formula (1) and (2)
Are as follows:
According to calculation formula (3), the calculation formula of supported screen body self-capacitance Cs are as follows:
Preferably, when Vo3 is equal to ceiling voltage in circuit in calculation formula (4), the Cs is charge amplifier electricity
The most large-size screen monitors body self-capacitance that road can be supported；The ceiling voltage is supply voltage Vdda.
Preferably, phase is controlled in third, a part of flow of charge screen body of the first pole plate of first capacitor Cb is certainly
Capacitor Cs, when charge is in stable state, the voltage of the first pole plate of first capacitor Cb is VA, VACalculation formula are as follows:
VA*(Cb+CS)=V1*Cb (5)
To
According to another aspect of the present invention, a kind of sequential control method of charge amplifier circuit is provided, for above
The charge amplifier circuit carries out timing control, comprising steps of
It controls charge amplifier circuit and enters the first control phase, for passing through the first reference voltage V1 to the first electricity
Hold Cb to charge；
It controls charge amplifier circuit and enters the second control phase, the output stable state electricity for calculated charge amplifier
Pressure value, thus the maximum screen body self-capacitance Cs that Extrapolation can be supported.
Preferably, when first switch P1, the 4th switch P4, the 5th switch P5 and the 7th switch P7 are connected, and second switch
When P2, third switch P3 and the 6th switch P6 are disconnected, for the first control phase；
When second switch P2, third switch P3 and the 6th switch P6 conducting, and first switch P1, the 4th switch P4, the
Five switch P5 and the 7th switch P7 are disconnected, for the second control phase.
Preferably, control charge amplifier circuit enters third control phase, for reducing the second control is being entered
The steady state voltage of the first pole plate of first capacitor Cb before phase.
Preferably, it when second switch P2 and the 5th switch P5 are connected, and first switch P1, third switch P3, the 4th switchs
When P4, the 6th switch P6 and the 7th switch P7 are disconnected, phase is controlled for third.
The technical solution for implementing charge amplifier circuit and its sequential control method of the present invention, has the following advantages that or beneficial
Effect: charge amplifier circuit of the present invention gives first capacitor C by changing the first control phasebThe voltage of charging and second
The steady state voltage for controlling the second pole plate of phase first capacitor Cb, so that in certain first capacitor Cb, the second capacitor Cf
In the case of, supported maximum screen body self-capacitance is increased, circuit performance is optimized, reduces physical layout area, is reduced
The cost of single chip.
Detailed description of the invention
In order to illustrate the technical solution of the embodiments of the present invention more clearly, required use in being described below to embodiment
Attached drawing be briefly described, it is therefore apparent that drawings in the following description are only some embodiments of the invention, for ability
For the those of ordinary skill of domain, without creative efforts, it can also be obtained according to these attached drawings other attached
Scheme, in attached drawing:
Fig. 1 is the schematic diagram of prior art charge amplifier circuit；
Fig. 2 is the equivalent circuit schematic that the prior art first controls phase；
Fig. 3 is the equivalent circuit schematic that the prior art second controls phase；
Fig. 4 is the switching time diagram of the prior art；
Fig. 5 is the circuit diagram of charge amplifier circuit embodiment of the present invention；
Fig. 6 is the circuit diagram of the transmission gate switch of charge amplifier circuit embodiment of the present invention；
Fig. 7 is the equivalent circuit schematic that the present invention first controls phase；
Fig. 8 is the equivalent circuit schematic that the present invention second controls phase；
Fig. 9 is the equivalent circuit schematic of third control phase of the present invention；
Figure 10 is the switching time diagram of charge amplifier circuit embodiment one of the present invention；
Figure 11 is the switching time diagram of charge amplifier circuit embodiment two of the present invention.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, the various examples that will be described below
Property embodiment will refer to corresponding attached drawing, these attached drawings constitute a part of exemplary embodiment, and which describe realizations
The various exemplary embodiments that the present invention may use, unless otherwise indicated, same numbers in different attached drawings indicate it is identical or
Similar element.Embodiment described in following exemplary embodiment does not represent all implementations consistent with this disclosure
Mode.It should be appreciated that they are only and as detailed in the attached claim, some aspects disclosed by the invention are consistent
The example of device and method also can be used other embodiments, or carry out structurally and functionally to embodiment enumerated herein
Modification, without departing from the scope of the present invention and essence.In other cases, it omits to well-known system, device, electricity
The detailed description of road and method, in case unnecessary details interferes description of the invention.
In the description of the present invention, it is to be understood that, term " first ", " second " ..., " the 7th " be only used for describing
Purpose is not understood to indicate or imply relative importance or implicitly indicates the quantity of indicated technical characteristic.As a result,
" first " that limits, " second " ..., the feature of " the 7th " can explicitly or implicitly include it is one or more described
Feature.In the description of the present invention, the meaning of " plurality " is two or more, unless otherwise specifically defined.It needs
It is noted that unless otherwise clearly defined and limited, term " connected ", " connection " shall be understood in a broad sense, for example, it may be
Electrical connection can be in communication with each other；It can be directly connected, be also possible to indirectly connected through an intermediary, can be two members
The interaction relationship of connection or two elements inside part.Term as used herein "and/or" includes one or more phases
Any and all combinations of the listed item of pass.It for the ordinary skill in the art, can be according to specific feelings
Condition understands the concrete meaning of above-mentioned term in the present invention.
In order to illustrate technical solutions according to the invention, the following is a description of specific embodiments.As Fig. 5-11 shows
Go out circuit diagram provided in an embodiment of the present invention, for ease of description, illustrates only portion relevant to the embodiment of the present invention
Point.
Fig. 1-4 shows the circuit diagram and working sequence of prior art charge amplifier.The charge of the prior art is put
Big device principle is as shown in Figure 1, circuit basic functional principle are as follows: and P1 and P2 is switch control signal, is provided by the clock of chip,
P1, P2 are alternatively referred to as two phase control switch.Phase, the switch conduction of P1 control are controlled first, P2 control is opened
Shutdown is opened, and corresponding equivalent circuit is as shown in Figure 2；Phase is controlled second, the switch of P1 control disconnects, and P2 control is opened
Conducting is closed, corresponding equivalent circuit is as shown in Figure 3.
As shown in figure 4, controlling phase first, the resetting charge of screen body self-capacitance Cs is reset switching timing,
The input terminal and output of operational amplifier charge to first capacitor Cb, fill in reset state, the second reference voltage V2
After the completion of electricity, the charge of the first pole plate of first capacitor Cb is Q1, Q1Calculation formula are as follows:
Q1=V2*Cb (11)
Phase is controlled second, the charge of the first pole plate of first capacitor Cb is redistributed, a part of charge
It charges to screen body self-capacitance Cs, another part charge charges to the second capacitor Cf, in stable state, due to first capacitor
The first pole plate and the second polar plate voltage of Cb is V2, and therefore, the two-plate of first capacitor Cb does not have charge.In stable state, the
The total electrical charge of one capacitor Cs and the second capacitor Cf are Q2, Q2Calculation formula are as follows:
Q2=V2*CS+(V2-VO2)*Cf (12)
According to law of conservation of charge, Q1=Q2, further according to calculation formula (11) and (12), can obtain:
Calculation formula (13) is the steady state output voltage of charge amplifier after the second control phase is stablized.When having
When finger touches screen, it equivalent can think that shielding body self-capacitance Cs is changed, according to calculation formula (13), charge amplifier
The variation that the variation for shielding body self-capacitance Cs is converted to voltage, is sent to analog-digital converter for analog voltage and is converted to number
Output, is provided to digital module and is stored, software reads the digital value, it is determined whether there is finger touch, if any touch,
Then provide the respective coordinates of touch point.
Since difference and manufacturing process, the process of making material have bigger difference, the screen body of touch screen is certainly
Capacitor difference is also larger, at present common touch screen on the market, the small only several picofarads of the capacitance of screen body self-capacitance, greatly
Up to picofarads up to a hundred.Therefore, one critically important technical indicator of charge amplifier is the screen body for the touch screen that can be supported
Self-capacitance range usually supports small screen body self-capacitance to be easier, and big screen body self-capacitance is supported to be limited to chip cost.One
A good charge amplifier allows for adapting to the screen body self-capacitance of larger range variation, is especially able to support sufficiently large
Shield body self-capacitance.
It can be obtained according to calculation formula (13):
Vo2 is charge amplifier equal to the Cs in circuit when ceiling voltage (supply voltage Vdda) in calculation formula (14)
The maximum screen body self-capacitance that can be supported, to support sufficiently large screen body self-capacitance Cs, Cb, Cf to need big as far as possible；Cb, Cf increase
Greatly, chip layout area increases, and the cost of single chip is got higher.Therefore, in chip area (chip cost) and chip performance (energy
The screen body self-capacitance for the maximum touch screen enough supported) aspect produce contradiction, to solve this contradiction, the present invention provides one
Kind new charge amplifier circuit and its sequential control method.
Embodiment one:
As shown in figure 5, being the circuit diagram embodiment of charge amplifier circuit of the present invention.Unlike the prior art
It is that circuit of the present invention changes the first control phase to the first capacitor Cb voltage to charge and the second control phase
First capacitor Cb the second pole plate steady state voltage, working sequence keep it is consistent with the prior art.
In the present embodiment, charge amplifier circuit of the present invention, including first capacitor Cb, the second capacitor Cf, operation amplifier
Device U1, first switch P1, second switch P2, third switch P3, the 4th switch P4, the 5th switch P5, the 6th switch P6 and
Seven switch P7.Preferably, first switch P1, second switch P2, third switch P3, the 4th switch P4, the 5th switch P5, the 6th open
It closes P6 and the 7th switch P7 circuit implementations is all the same, it is for illustration only to be conveniently distinguish.
In the present embodiment, the one end first switch P1 and the one end second switch P2 are with the screen body self-capacitance Cs's of touch screen
The connection of first pole plate, first switch P1 other end ground connection, the second switch P2 other end and the one end third switch P3, the 4th switch P4
The connection of the first pole plate of one end and first capacitor Cb, the 4th switch P4 other end are connect with the first reference voltage V1, first capacitor
The second pole plate of Cb is connect with the 5th one end switch P5 and the 6th one end switch P6, and the 5th switch P5 other end ground connection, the 6th opens
The P6 other end is closed to connect with the first reference voltage V1；The third switch P3 other end and operational amplifier U1 inverting input terminal Vn, the
The first pole plate of two capacitor Cf and the connection of the 7th one end switch P7, operational amplifier U1 non-inverting input terminal Vp and the second reference voltage
The second pole plate and the 7th switch P7 other end of V2 connection, operational amplifier U1 output end vo and the second capacitor Cf are connected as circuit
Output end vo 3；Specifically, the first reference voltage V1 and the second reference voltage V2 are unequal.
In the present embodiment, the sequential control method of charge amplifier circuit, for previously described charge amplifier
Circuit carries out timing control, comprising steps of
It controls charge amplifier circuit and enters the first control phase, for passing through the first reference voltage V1 to the first electricity
Hold Cb to charge；Specifically, when first switch P1, the 4th switch P4, the 5th switch P5 and the 7th switch P7 conducting, and second
When switch P2, third switch P3 and the 6th switch P6 are disconnected, for the first control phase；
It controls charge amplifier circuit and enters the second control phase, the output stable state electricity for calculated charge amplifier
Pressure value, thus the maximum screen body self-capacitance Cs that Extrapolation can be supported；Specifically, when first switch P1, the 4th switch P4,
5th switch P5 and the 7th switch P7 is disconnected, and when second switch P2, third switch P3 and the 6th switch P6 conducting, for the second control
Phase processed.
Phase is controlled first, the first reference voltage V1 charges to first capacitor Cb, after charging complete, first
The charge of the first pole plate of capacitor Cb is Q3, Q3Calculation formula are as follows:
Q3=V1*Cb (1)
Phase is controlled second, the quantity of electric charge of the first pole plate of first capacitor Cb is Q4, Q4Calculation formula are as follows:
Q4=V2*CS+(V2-VO3)*Cf+(V2-V1)*Cb (2)
According to law of conservation of charge, Q3=Q4, Vo3 is calculated further according to calculation formula (1) and (2), the calculating of Vo3 is public
Formula are as follows:
Calculation formula (3) gives new charge amplifier in the steady state output voltage and screen body of the second control phase
The relationship of self-capacitance Cs shields the calculation formula of body self-capacitance Cs according to calculation formula (3) are as follows:
Preferably, when Vo3 is equal to ceiling voltage in circuit in calculation formula (4), Cs is charge amplifier circuit branch
The most large-size screen monitors body self-capacitance held, specifically, ceiling voltage is generally supply voltage Vdda.
Comparing calculation formula (4) and calculation formula (14), first half (with Cf associated section) be it is essentially identical, it is later half
It is partially different (from Cb associated section), when the second reference voltage V2 is less than the first reference voltage V1, what the present invention can support
Maximum screen body self-capacitance is greater than the maximum screen body self-capacitance that the prior art can be supported.In general circuit, the second ginseng is taken
The half (i.e. V2=Vdda/2) that voltage V2 is supply voltage Vdda, even lower voltage are examined, the first reference voltage V1 is equal to
Supply voltage Vdda, at this point, the screen body self-capacitance that the present invention can support is bigger.
From circuit theory angle analysis, compared with prior art, phase rank is controlled to second in the first control phase
During section switching, there is bigger mutation, the voltage difference of first capacitor Cb in the voltage difference of the two-plate of first capacitor Cb
Sudden Changing Rate determine the second control phase can be supplied to screen body self-capacitance Cs and the second capacitor Cf maximum total charge dosage,
Sudden Changing Rate is bigger, and the total charge dosage provided is bigger, and the screen body self-capacitance Cs that can be supported is also bigger.All switches in Fig. 5
The timing of two control phase switchings is identical as switching sequence used in the prior art, as shown in Figure 10, does not do herein
It repeats.
In the present embodiment, the voltage of the first pole plate of first capacitor Cb was easy to be flushed to the maximum potential in circuit
(supply voltage Vdda), it could even be possible to being more than supply voltage Vdda.First control phase, the first of first capacitor Cb
The voltage of pole plate is V1, and the voltage of the second pole plate is 0, when the first control phase switches to the second control phase,
The voltage instantaneous of the second pole plate of first capacitor Cb is lifted to V1, when the charge discharging resisting speed of A point is not fast enough in circuit, A point electricity
Pressure is that very possible upper punching is more than supply voltage Vdda, theoretically, if A point is at this moment without charge discharging resisting, the first electricity
The voltage highest for holding the first pole plate of Cb is up to twice of 2*Vdda of supply voltage.
Fig. 6 gives the specific implementation circuit diagram switched in the present invention, including transmission gate switch TG, transmission gate switch
TG includes in parallel PMOS tube and NMOS tube, and the substrate of PMOS tube is connect with supply voltage Vdda, the substrate of NMOS tube with it is public
Ground GND connection.Specifically, the substrate of PMOS tube connects the maximum potential (supply voltage Vdda) of circuit, the substrate of NMOS tube connects electricity
The potential minimum GND on road.Under normal circumstances, the source-drain voltage of PMOS tube does not exceed supply voltage Vdda, and transmission gate is opened
Parasitic pn-junction and NMOS tube source and drain that the PMOS tube source and drain and substrate in the Central Shanxi Plain are formed and the parasitic pn-junction that substrate is formed are reversed
Biasing, not will form electric current.After A point voltage is more than supply voltage Vdda, the parasitic pn-junction of script reverse bias becomes positive
Biasing, forms very big forward current, and charge is released to power supply from this paths, the output voltage of charge amplifier is caused to occur
Undesirable change.The basic function of charge amplifier is exactly the change for requiring output voltage that can uniquely reflect detection self-capacitance
Change, once and there are other factors (for example the voltage overshoot of the first pole plate of first capacitor Cb leads to charge leakage) also can in circuit
Change output voltage, then the touch signal of finger is possible to be disturbed, or even is flooded completely by leaky, thus charge
Amplifier can not work normally.
Embodiment two:
In the present embodiment, the basic phase of charge amplifier circuit principle of charge amplifier circuit principle and embodiment one
Together, steady state output voltage theory deduction is no difference with embodiment one, the same calculation formula of steady state output voltage theoretical expression
(3).What is different from the first embodiment is that the control phase state of charge amplifier increases to three from original two, increase
One intermediate phase is compared with embodiment one for convenience, and intermediate phase is referred to as third control phase.Each control
The corresponding equivalent circuit schematic of phase is as Figure 7-9.Third controls the introducing of phase so that from the first control
During phase switches to the second control phase, the variation of the first pole plate (A point) voltage of first capacitor Cb becomes
Gently, to substantially reduce the voltage overshoot of A point, charge leakage problem caused by avoiding after A point overtension.
It as shown in figure 11, is the switching timing control flow chart of charge amplifier circuit of the present invention, for charge
Amplifier circuit carries out timing control, comprising steps of
It controls charge amplifier circuit and enters the first control phase, for passing through the first reference voltage V1 to the first electricity
Hold Cb to charge；
Control charge amplifier circuit enters third control phase, for reducing the second control phase is being entered
The steady state voltage of the first pole plate of first capacitor Cb before；
It controls charge amplifier circuit and enters the second control phase, the output stable state electricity for calculated charge amplifier
Pressure value, thus the maximum screen body self-capacitance Cs that Extrapolation can be supported.
More specifically, when first switch P1, the 4th switch P4, the 5th switch P5 and the 7th switch P7 are connected, and second
When switch P2, third switch P3 and the 6th switch P6 are disconnected, for the first control phase.
Phase is controlled first, equivalent circuit schematic is as shown in fig. 7, control phase rank with the first of embodiment one
Section working principle is identical, is charged with the first reference voltage V1 to first capacitor Cb, the first control phase rank in embodiment one
Section is directly entered the second control phase after completing, and the first control phase enters the after completing in the present embodiment
Three control phases.
When second switch P2 and the 5th switch P5 are connected, and first switch P1, third switch P3, the 4th switch P4, the 6th
When switch P6 and the 7th switch P7 is disconnected, phase is controlled for third.Phase, equivalent circuit schematic are controlled in third
As shown in figure 8, the charge of the first pole plate of first capacitor Cb is redistributed, a part of charge continues to stay on first capacitor Cb,
A part of flow of charge screen body self-capacitance Cs, charge ratio relationship depends on the capacitance ratio of Cb and Cs, specifically, first
A part of flow of charge screen body self-capacitance Cs of the first pole plate of capacitor Cb, when charge is in stable state, the of first capacitor Cb
The voltage of one pole plate is VA, VACalculation formula are as follows:
VA*(Cb+CS)=V1*Cb (5)
To
If Cb=Cs, VA=V1/2, the voltage for being equivalent to the first pole plate of first capacitor Cb are declined by original V1
Half.If Cb < Cs, voltage will be lower, and third controls the lower V of phaseAVoltage is beneficial to the second control phase
When the switching of position stage, VAVoltage is unlikely to overshoot too big, guarantee VAVoltage is not higher than supply voltage Vdda, avoids switch drain.The
Three control phases are switched to the second control phase after stablizing.
When second switch P2, third switch P3 and the 6th switch P6 are connected, and first switch P1, the 4th switch P4, the 5th
When switch P5 and the 7th switch P7 is disconnected, for the second control phase.Phase, equivalent circuit schematic are controlled second
As shown in Figure 9, it is found that the second control phase of the present embodiment and the second control phase state of embodiment one
Identical, the A point charge of the first pole plate of first capacitor Cb is redistributed again, a part of the second capacitor of flow of charge Cf.
Calculation formula (1) in embodiment one, (2), (3) are still set up in the present embodiment.
Phase, the calculation formula of circuit output end Vo4 are controlled second are as follows:
Calculation formula (7) and (3) be it is the same, the maximum screen body that the present embodiment two and embodiment one can be supported is from electricity
Hold also identical.
Charge amplifier circuit of the present invention by change voltage that the first control phase charge to first capacitor Cb with
The steady state voltage of the second pole plate of second control phase first capacitor Cb, so that in certain first capacitor Cb, the second electricity
In the case of holding Cf, the range of supported maximum screen body self-capacitance is increased, circuit performance is optimized, reduces domain face
Product, reduces the cost of single chip.
The above is merely preferred embodiments of the present invention, those skilled in the art know, are not departing from essence of the invention
In the case where mind and range, various changes or equivalent replacement can be carried out to these features and embodiment.In addition, of the invention
Under introduction, it can modify to these features and embodiment to adapt to particular situation and material without departing from of the invention
Spirit and scope.Therefore, the present invention is not limited to the particular embodiment disclosed, and the right of fallen with the application is wanted
The embodiment in range is asked to belong to protection scope of the present invention.
Claims (10)
1. a kind of charge amplifier circuit characterized by comprising first capacitor (Cb), the second capacitor (Cf), operational amplifier
(U1), first switch (P1), second switch (P2), third switch (P3), the 4th switch (P4), the 5th switch (P5), the 6th open
Close (P6) and the 7th switch (P7)；
The first pole of described first switch one end (P1) and the one end second switch (P2) with the screen body self-capacitance (Cs) of touch screen
Plate connection, first switch (P1) other end ground connection, second switch (P2) other end and the third switch (P3) one
The first pole plate connection at end, the 4th switch one end (P4) and first capacitor (Cb), the 4th switch (P4) other end and first
Reference voltage (V1) connection, the second pole plate of the first capacitor (Cb) and described 5th switch one end (P5) and the 6th switch
(P6) one end connects, the 5th switch (P5) other end ground connection, the 6th switch (P6) other end and first reference
Voltage (V1) connection；
Third switch (P3) other end and the operational amplifier (U1) inverting input terminal (Vn), second capacitor (Cf)
The first pole plate and it is described 7th switch the one end (P7) be all connected with, operational amplifier (U1) non-inverting input terminal (Vp) and second
Reference voltage (V2) connection, the second pole plate of operational amplifier (U1) output end (Vo) and second capacitor (Cf) and the
Seven switch (P7) other ends are all connected with as circuit output end (Vo3)；First reference voltage (V1) and described second is with reference to electricity
Press (V2) unequal.
2. charge amplifier circuit according to claim 1, which is characterized in that when the first switch (P1), the 4th open
It closes (P4), the 5th switch (P5) and the 7th switch (P7) conducting, and the second switch (P2), third switch (P3) and the 6th opens
When closing (P6) disconnection, for the first control phase；
It is disconnected when the first switch (P1), the 4th switch (P4), the 5th switch (P5) and the 7th switch (P7), and described second
When switching (P2), third switch (P3) and the 6th switch (P6) conducting, for the second control phase.
3. charge amplifier circuit according to claim 2, which is characterized in that in the first control phase and the
It further include third control phase between two control phases；
When the second switch (P2) and the 5th switch (P5) conducting, and first switch (P1), third switch (P3), the 4th switch
(P4), when the 6th switch (P6) and the 7th switch (P7) disconnect, phase is controlled for the third.
4. charge amplifier circuit according to claim 2 or 3, which is characterized in that phase is controlled described first,
First reference voltage (V1) charges to the first capacitor (Cb), after charging complete, the first capacitor (Cb)
The charge of first pole plate is Q3, the Q3Calculation formula are as follows:
Q3=V1*Cb (1)
In the second control phase, the quantity of electric charge of the first pole plate of the first capacitor (Cb) is Q4, the Q4Calculating
Formula are as follows:
Q4=V2*CS+(V2-VO3)*Cf+(V2-V1)*Cb (2)
According to law of conservation of charge, the Q3=Q4, Vo3 is calculated according to the calculation formula (1) and (2), the Vo3's
Calculation formula are as follows:
According to the calculation formula (3), the calculation formula of the screen body self-capacitance (Cs) are as follows:
5. charge amplifier circuit according to claim 4, which is characterized in that the Vo3 described in the calculation formula (4)
Equal to when ceiling voltage, the Cs is the maximum screen that the charge amplifier circuit is supported in the charge amplifier circuit
Body self-capacitance；The ceiling voltage is supply voltage (Vdda).
6. charge amplifier circuit according to claim 4, which is characterized in that control phase, institute in the third
Screen body self-capacitance (Cs) described in a part of flow of charge of the first pole plate of first capacitor (Cb) is stated, when charge is in stable state,
The voltage of first pole plate of the first capacitor (Cb) is VA, the VACalculation formula are as follows:
VA*(Cb+CS)=V1*Cb (5)
To
7. a kind of sequential control method of charge amplifier circuit, which is characterized in that for described in claim any one of 1-6
Charge amplifier circuit carry out timing control, comprising steps of
The charge amplifier circuit is controlled into the first control phase, for right by first reference voltage (V1)
The first capacitor (Cb) is charged；
The charge amplifier circuit is controlled into the second control phase, the output for calculating the charge amplifier is steady
State voltage value, thus the maximum screen body self-capacitance (Cs) that Extrapolation can be supported.
8. the sequential control method of charge amplifier circuit according to claim 7, which is characterized in that open when described first
(P1), the 4th switch (P4), the 5th switch (P5) and the 7th switch (P7) conducting are closed, and the second switch (P2), third are opened
When closing (P3) and the 6th switch (P6) disconnection, for the first control phase；
When the second switch (P2), third switch (P3) and the 6th switch (P6) conducting, and the first switch (P1), the 4th
When switching (P4), the 5th switch (P5) and the 7th switch (P7) disconnection, for the second control phase.
9. the sequential control method of charge amplifier circuit according to claim 7, which is characterized in that described in the control
Charge amplifier circuit enters before the second control phase, further comprises the steps of:
It controls the charge amplifier circuit and enters third control phase, for reducing the second control phase is being entered
The steady state voltage of first pole plate of stage foregoing description first capacitor (Cb).
10. the sequential control method of charge amplifier circuit according to claim 9, which is characterized in that when described second
Switch (P2) and the 5th switch (P5) conducting, and first switch (P1), third switch (P3), the 4th switch (P4), the 6th switch
(P6) when and the 7th switch (P7) disconnects, phase is controlled for the third.
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| CN111404528A (en) * | 2020-06-02 | 2020-07-10 | 深圳市芯天下技术有限公司 | Reset circuit of charge amplifier and reset time acquisition method |
| CN112332828A (en) * | 2020-09-15 | 2021-02-05 | 南京芯思科技有限公司 | Charging circuit, analog receiving circuit and charging method based on self-capacitance touch screen |
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| CN110212880B (en) | 2024-03-22 |
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