CN203149039U - Self-capacitance sensing circuit adopting charge compensation - Google Patents
Self-capacitance sensing circuit adopting charge compensation Download PDFInfo
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- CN203149039U CN203149039U CN 201320061417 CN201320061417U CN203149039U CN 203149039 U CN203149039 U CN 203149039U CN 201320061417 CN201320061417 CN 201320061417 CN 201320061417 U CN201320061417 U CN 201320061417U CN 203149039 U CN203149039 U CN 203149039U
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Abstract
The utility model discloses a self-capacitance sensing circuit adopting charge compensation. The self-capacitance sensing circuit includes a measured capacitor Cs, a sampling control circuit, a constant current compensation module, a charge compensation control module, a zero-cross detection module and a time recording module. The self-capacitance sensing circuit of the utility model has the advantages of simple circuit, utilization of conventional devices, artful and concise design; no requirement for external components, reduction of device cost, flexibility in realization of the charge compensation control module, filtering function, improved anti-interference performance, no need for an analog-to-digital converter (ADC), great reduction of circuit area, and saved cost.
Description
Technical field
The utility model belongs to electronic circuit and detection technology field, is specifically related to a kind of self-capacitance sensing circuit.
Background technology
With respect to traditional machinery (button) control mode, capacitance touch has tangible advantage, as good endurance, friendly interface etc., thereby in every field especially field of human-computer interaction more and more widely application is arranged.
Traditional self-capacitance method for sensing normally utilizes the relaxor principle or capacitance is converted to magnitude of voltage and utilizes analog to digital converter (ADC) to convert thereof into digital quantity then.The former, when the measured capacitance size variation, oscillation period also can respective change, thereby can take this as a foundation the variation of sensing measured capacitance the oscillation period that discharges and recharges to measure it by measured capacitance is not stopped; And latter's charge transfer effect by measured capacitance usually, by someway capacitance size being changed into corresponding voltage, use the analog to digital converter (ADC) of 8 (or more high precision) that this magnitude of voltage is sampled its quantification afterwards, thereby can come the sensing measured capacitance by quantizing to be worth changing.
The core of the former circuit is comparer and charge-discharge circuit normally; The latter then generally includes a switching capacity amplifier and an analog to digital converter (ADC).Comparatively speaking, the former circuit structure is simple, but the sensing time is long, anti-interference is relatively poor; Latter's speed is very fast, anti-interference is better, but because the module complexity especially needs a special analog to digital converter (ADC), causes decoring outside the increase of sheet area, and its dynamic power consumption is also higher.
The utility model content
The utility model purpose is to provide a kind of low-power consumption scheme of self-capacitance sensing, and the size (or variation) that is used for outside measured capacitance is measured, and has low, the characteristic of simple structure of cost.In conjunction with shown in Figure 1, realize that the technical scheme of above-mentioned purpose is as follows:
A kind of self-capacitance sensing circuit that adopts charge compensation is characterized in that, comprising:
Measured capacitance Cs, its first end is connected and fixed potential voltage V0, and second end connects the input of controlling of sampling circuit;
The controlling of sampling circuit 1., its first end connects second end of measured capacitance, second end is connected and fixed potential voltage V1, the 3rd end connects the charge compensation control module; Be used for measured capacitance Cs second end is initialised to set potential V1, also be used for the electric charge on the measured capacitance Cs is injected to the charge compensation control module;
2. the constant current compensating module controlledly down gives the charge compensation control module with the constant rate of speed electric charge that affords redress, and the electric charge by measured capacitance Cs iunjected charge compensation control module is compensated;
3. the charge compensation control module is initialised to the electric charge, the output simultaneously that receive on the measured capacitance Cs that injects by the controlling of sampling circuit after work zero point and departs from zero point, and compensation charge, output simultaneously that perhaps receiving the constant current compensating module provides return zero point;
4. the zero passage detection module connects the output of charge compensation control module, and produces reverse signal according to the output of charge compensation control module; And
5. the time logging modle connects the output 4. of zero passage detection module, the time cycle of recording described reverse signal.
As concrete technical scheme, 1. described controlling of sampling circuit is made of initialisation switch and sampling switch, second end of measured capacitance Cs is connected and be initialised to set potential V1 by closed initialisation switch, will make second end of measured capacitance Cs connect charge compensation control module input and iunjected charge 3. by closed sampling switch.
As concrete technical scheme, 2. described constant current compensating module is made up of a constant current source and its gauge tap, and the folding of gauge tap is used for control and utilizes this constant current source to carry out the time of charge compensation.
As concrete technical scheme, described constant current source is the switched-capacitor circuit of a constant current source or a fixed frequency or the resistance of a serial connection.
As concrete technical scheme, described charge compensation control module is 3. by the first operational amplifier OPA, integrating capacitor C
INTConstitute with reset switch; The input end of the first operational amplifier OPA connects the output of controlling of sampling circuit, its integrating capacitor C
INTPositive input terminal-V with the reset switch cross-over connection first operational amplifier OPA
REF0Reset switch is used for before the sampling compensation input end-output end voltage of the first operational amplifier OPA is initialized to V
REF0, when second end of measured capacitance Cs was connected to 3. the input of charge compensation control module, the electric charge on the measured capacitance Cs was transferred to integrating capacitor C
INTOn, and cause the output of the first operational amplifier OPA to depart from initial value V
REF0
As concrete technical scheme, 4. described zero passage detection module is made of second an operational amplifier CMP, and its first end is connected to reference voltage V
REF1, second end is connected to the output 3. of charge compensation control module, be used for the charge compensation stage to the charge compensation control module output 3. carried out V
REF1The point monitoring is when the output 3. of charge compensation control module strides across V
REF1The time, the output counter-rotating 4. of zero passage detection module.
As concrete technical scheme, 5. described time logging modle is made of digital counter, and with the output 4. of zero passage detection module as input, be used for record and begin to compensate to the time that 4. the zero passage detection module exports the whole process of counter-rotating from constant current source.
The circuit that the utility model provides can be used for the sensing of self-capacitance, and then can be used in the control application such as touch key-press, capacitance touch screen and approaching induction.Compared to existing technology, the beneficial effects of the utility model are:
1, circuit structure is simple, and conventional device is set up just and can be realized, designs ingenious but uncomplicated;
2, need not outer member, reduced device cost;
3, the charge compensation control module can realize flexibly, adds filter function, realizes that anti-interference improves;
4, owing to do not need analog to digital converter (ADC), thereby greatly reduce circuit area, saved cost.
Description of drawings
The self-capacitance sensing circuit that Fig. 1 provides for the utility model system principle diagram.
The specific implementation circuit of the self-capacitance sensing circuit that Fig. 2 provides for embodiment.
Fig. 3 is in the circuit state of initial phase for the specific implementation circuit.
Fig. 4 is in the circuit state of sample phase for the specific implementation circuit.
Fig. 5 is in the circuit state of compensated stage for the specific implementation circuit.
Embodiment
As shown in Figure 2, present embodiment has provided a kind of specific implementation circuit of self-capacitance sensing circuit shown in Figure 1.Wherein, 1. the controlling of sampling circuit is made of sampling switch S1 and initialisation switch S2; 2. the constant current compensating module is made up of constant current source i0 and gauge tap S4; The compensation control module is 3. by the first operational amplifier OPA and integrating capacitor C
INTForm with reset switch S3; 4. zero-crossing detection circuit is made of the second operational amplifier CMP; 5. the make-up time writing circuit is realized by a simple counter.
For convenience of description, whole measuring phases is divided into initial phase, sample phase and charge compensation stage, as detailed below:
As shown in Figure 3, at initial phase, second end by Closing Switch S2 measured capacitance Cs is initialized to certain set potential V1, and the input end by the Closing Switch S3 first operational amplifier OPA and output terminal are initialised to work zero point, i.e. reference voltage V
REF0Treat to enter sample phase after initialization is finished.
As shown in Figure 4, in sample phase, disconnect reset switch S3, closed sampling switch S1.Electric charge on the measured capacitance Cs will shift and be injected into integrating capacitor C
INTOn.Wherein, carry the quantity of electric charge before the S1 closure on the Cs: Q0=Cs*(V1-V0); Carrying electric charge after the S1 closure on the Cs will share and be injected into integrating capacitor C
INTOn, after circuit is stable, transfer to integrating capacitor C
INTOn the quantity of electric charge: δ Q=(V1-VREF0) * Cs*C
INT/ (Cs+C
INT); To cause change in voltage δ V=δ Q/C in the output of the first operational amplifier OPA
INT=Cs (V1-VREF0)/(Cs+C
INT).After finishing, sampling enters the charge compensation stage.
As shown in Figure 5, in the charge compensation stage, disconnect sampling switch S1, constant current compensating module gauge tap S4 closure 2., constant current source i0 begins integrating capacitor C
INTThe electric charge that injects opposite in sign compensates (charge polarity of compensation is opposite with the polarity of measured capacitance Cs iunjected charge) with the electric charge that measured capacitance Cs is injected.Along with the carrying out of compensation, the output voltage of the first operational amplifier OPA is gradually to V
REF0Direction returns, and the electric charge on the measured capacitance Cs also will continue is injected into integrating capacitor C
INT, when the output voltage of OPA revert to V
REF1The time zero passage detection module output counter-rotating 4..When beginning to compensate, 5. the time logging modle picks up counting; Along with the carrying out the output 3. of charge compensation control module and will return work zero point gradually and will finally cause the output counter-rotating 4. of zero passage detection module of compensation, 5. the time logging modle stops timing, and all electric charges on this moment Cs will all be injected into integrating capacitor C
INTGo up and by full remuneration.Because the quantity of electric charge of measured capacitance Cs injection is proportional to its size, thereby by the length of record charge compensation time and to its analysis, can obtain size and the variation thereof of measured capacitance Cs.
Wherein, make the output of the first operational amplifier OPA revert to voltage V
REF1Need the quantity of electric charge of compensation to be:
Qc=C
INT(V
REF0-V
REF1)+Cs (V1-V
REF1); Suppose V
REF0=V
REF1, Qc=Cs (V1-V then
REF1), with C
INTSize irrelevant.
Constant current source i0 begins C
INTThe electric charge that injects opposite in sign compensates with the electric charge that measured capacitance Cs is injected, and needing elapsed time is t=Qc/i0=Cs (V1-V
REF1As seen)/i0, the make-up time that 5. t just records for the time logging modle, under the constant situation of i0, make-up time t is directly proportional with the size of measured capacitance Cs.Thereby the size of make-up time t reflected the size of measured capacitance, and the variation of make-up time t has then reflected the variation of measured capacitance Cs.
In above-described embodiment, set potential voltage V0, V1 can be identical, also can be different; Reference potential voltage V
REF0, V
REF1Can be identical, also can be different.
Self-capacitance sensing circuit and method for sensing that above embodiment provides have following characteristics:
1. circuit structure is simple, and conventional device is set up just and can be realized, designs ingenious but uncomplicated;
2. the first operational amplifier OPA and integrating capacitor C
INTHave filtering characteristic, thereby improved anti-interference greatly;
3. do not have similar analog to digital converter (ADC) large tracts of land and high power consumption module, thereby have power consumption advantages when saving cost.
Be understandable that, concerning the those of ordinary skill in field, the utility model place, can carry out corresponding equivalence transformation according to the technical solution of the utility model and design thereof, all should belong to the disclosed scope of the utility model without creationary equivalence replacement.The utility model also can be used for approaching to detect waiting other sensor application except can using in the touch-control field.
Claims (7)
1. a self-capacitance sensing circuit that adopts charge compensation is characterized in that, comprising:
Measured capacitance Cs, its first end is connected and fixed potential voltage V0, and second end connects the input of controlling of sampling circuit;
The controlling of sampling circuit, its first end connects second end of measured capacitance, and second end is connected and fixed potential voltage V1, and the 3rd end connects the charge compensation control module; Be used for measured capacitance Cs second end is initialised to set potential V1, also be used for the electric charge on the measured capacitance Cs is injected to the charge compensation control module;
The constant current compensating module is controlledly down given the charge compensation control module with the constant rate of speed electric charge that affords redress, and the electric charge by measured capacitance Cs iunjected charge compensation control module is compensated;
The charge compensation control module is initialised to the electric charge, the output simultaneously that receive on the measured capacitance Cs that injects by the controlling of sampling circuit after work zero point and departs from zero point, and compensation charge, output simultaneously that perhaps receiving the constant current compensating module provides return zero point;
The zero passage detection module connects the output of charge compensation control module, and produces reverse signal according to the output of charge compensation control module; And
The time logging modle connects the output of zero passage detection module, and record begins to compensate time cycle to described reverse signal by constant current source.
2. the self-capacitance sensing circuit of employing charge compensation according to claim 1, it is characterized in that, described controlling of sampling circuit is made of initialisation switch and sampling switch, second end of measured capacitance Cs is connected and be initialised to set potential V1 by closed initialisation switch, will make second end of measured capacitance Cs connect input and the iunjected charge of charge compensation control module by closed sampling switch.
3. the self-capacitance sensing circuit of employing charge compensation according to claim 2, it is characterized in that: described constant current compensating module is made up of a constant current source and constant current source gauge tap, and gauge tap control utilizes this constant current source to carry out the time of charge compensation.
4. the self-capacitance sensing circuit of employing charge compensation according to claim 3, it is characterized in that: described constant current source is the switched-capacitor circuit of a constant current source or a fixed frequency or the resistance of a serial connection.
5. according to the self-capacitance sensing circuit of claim 2 or 3 described employing charge compensations, it is characterized in that: described charge compensation control module is by the first operational amplifier OPA, integrating capacitor C
INTConstitute with reset switch; The input end of the first operational amplifier OPA connects the output of controlling of sampling circuit, integrating capacitor C
INTWith energy of the common formation of the first operational amplifier OPA iunjected charge is converted into the circuit that voltage is exported; Reset switch is used for before the sampling compensation input end-output end voltage of the first operational amplifier OPA is initialized to V
REF0, when second end of measured capacitance Cs was connected to the input of charge compensation control module, the electric charge on the measured capacitance Cs was transferred to integrating capacitor C
INTOn, and cause the output of the first operational amplifier OPA to depart from initial value V
REF0
6. the self-capacitance sensing circuit of employing charge compensation according to claim 5, it is characterized in that: described zero passage detection module is made of second an operational amplifier CMP, and its first end is connected to reference voltage V
REF1, second end is connected to the output of charge compensation control module, is used in the charge compensation stage V being carried out in the output of charge compensation control module
REF1Point monitoring is when the output of charge compensation control module strides across V
REF1The time, the output counter-rotating of zero passage detection module.
7. the self-capacitance sensing circuit of employing charge compensation according to claim 6, it is characterized in that: described time logging modle is made of digital counter, and with the output of zero passage detection module as input, be used for record begins to compensate to the whole process of zero passage detection module output counter-rotating from constant current source time.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201320061417 CN203149039U (en) | 2013-01-31 | 2013-01-31 | Self-capacitance sensing circuit adopting charge compensation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 201320061417 CN203149039U (en) | 2013-01-31 | 2013-01-31 | Self-capacitance sensing circuit adopting charge compensation |
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| Publication Number | Publication Date |
|---|---|
| CN203149039U true CN203149039U (en) | 2013-08-21 |
Family
ID=48976555
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 201320061417 Withdrawn - After Issue CN203149039U (en) | 2013-01-31 | 2013-01-31 | Self-capacitance sensing circuit adopting charge compensation |
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|---|---|
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103149450A (en) * | 2013-01-31 | 2013-06-12 | 珠海中慧微电子有限公司 | Self-capacitance sensing circuit using charge compensation and self-capacitance sensing method |
| CN112255464A (en) * | 2020-09-29 | 2021-01-22 | 华中科技大学 | Capacitance measuring circuit and measuring method based on charge compensation analog front end |
-
2013
- 2013-01-31 CN CN 201320061417 patent/CN203149039U/en not_active Withdrawn - After Issue
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103149450A (en) * | 2013-01-31 | 2013-06-12 | 珠海中慧微电子有限公司 | Self-capacitance sensing circuit using charge compensation and self-capacitance sensing method |
| CN103149450B (en) * | 2013-01-31 | 2015-05-20 | 珠海中慧微电子有限公司 | Self-capacitance sensing circuit using charge compensation and self-capacitance sensing method |
| CN112255464A (en) * | 2020-09-29 | 2021-01-22 | 华中科技大学 | Capacitance measuring circuit and measuring method based on charge compensation analog front end |
| CN112255464B (en) * | 2020-09-29 | 2021-08-24 | 华中科技大学 | Capacitance measuring circuit and measuring method based on charge compensation analog front end |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| AV01 | Patent right actively abandoned |
Granted publication date: 20130821 Effective date of abandoning: 20150520 |
|
| RGAV | Abandon patent right to avoid regrant |