CN103245840B - A kind of multiplexed port interface circuit for capacitance type sensor - Google Patents

Abstract

The invention discloses a kind of multiplexed port interface circuit for capacitance type sensor, V _ds+, V _ds-the fixed port of corresponding capacitance type sensor respectively, V _mathe movable port of corresponding capacitance type sensor: V _ds+, V _ds-be connected with two input ends of Full differential operational amplifier A1 respectively, V _ds+, V _ds-two the negative terminal inputs also inputting Single-end output operational amplifier A 3 respectively by electric capacity and three ends are connected, V _ds+and V _ds-respectively by other electric capacity and node V _sbe connected, the anode of A3 exports by a switch and node V _sbe connected; Full differential operational amplifier A1 output terminal is connected with Full differential operational amplifier A2 input end respectively by electric capacity.The present invention can apply electrostatic force at same port and carry out capacitance detecting, realizes multiplexed port, adopts fully differential mode to realize the size that can not reduce electrostatic force, can effectively suppress power supply and common-mode noise.

Description

A kind of multiplexed port interface circuit for capacitance type sensor

Technical field

The present invention relates to a kind of port multiplexing circuit, particularly a kind of multiplexed port interface circuit for capacitance type sensor.Background technology

Tested mechanical quantity, the sensor being converted to electric capacitance change as displacement, pressure etc. is called capacitance type sensor, since the end of the seventies, along with the development of integrated circuit technique, occur and the capacitance type sensor that miniature measurement instrument is packaged together, this novel sensor can make the impact of distributed capacitance greatly reduce, and the shortcoming making it intrinsic is overcome, and therefore obtains and uses widely.

Capacitance type sensor has the following advantage compared with the sensor such as resistance-type, inductance type:

(1) high impedance, power are little, and between charged pole plate, electrostatic attraction is minimum, therefore required input minimum energy, so suitable to especially solving the low measurement problem of input energy;

(2) temperature stability is good, and the capacitance of sensor is general to have nothing to do with electrode material, is conducive to the material that selective temperature coefficient is low, again because of own generate heat minimum, very micro-to stability influence;

(3) structure is simple, strong adaptability, body to be measured be conductor or semiconductor equalizing can, can work in rugged surroundings, capacitive sensor structure is simple, be easy to manufacture, can do very small and exquisite, to realize some special measurement; And can be operated in the rugged environments such as high/low temperature, intense radiation and high-intensity magnetic field, also can measure the magnetic workpiece of band.

Due to these above-mentioned advantages, capacitance type sensor has been widely used in the fields such as civilian industry control and military affairs.In Capacitative sensor system design, Capacitance-type sensor interface circuit determines the resolution of sensing system to detection limit to a certain extent, but be existingly easy to integrated and the capacitance type sensor extensively adopted can only be used for the detection of electric capacity, purposes is single, use other functions then must carry out integrated with other circuit, complex structure, uses inconvenience.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, there is provided a kind of can apply electrostatic force simultaneously at same port and carry out a kind of multiplexed port interface circuit for capacitance type sensor of capacitance detecting, this interface circuit can not reduce the size of electrostatic force while realizing capacitance detecting, adopt fully differential mode to realize applying electrostatic force and carrying out capacitance detecting, can effectively suppress power supply and common-mode noise.

The object of the invention is to be achieved through the following technical solutions: a kind of multiplexed port interface circuit for capacitance type sensor, V _ds+, V _ds-the fixed port of corresponding capacitance type sensor respectively, V _mathe movable port of corresponding capacitance type sensor:

V _ds+by electric capacity C _cdswith an input end V of Full differential operational amplifier A1 _i1+be connected, by another one electric capacity C _fbwith an output terminal V of Full differential operational amplifier A1 _o1-connect, V _ds+also by electric capacity C _cdssthe negative terminal inputting Single-end output operational amplifier A 3 with three ends inputs V _is2-be connected, V _ds+by another one electric capacity C _cmwith node V _sbe connected;

V _ds-by electric capacity C _cdswith another input end V of Full differential operational amplifier A1 _i1-be connected, by another one electric capacity C _fbwith another output terminal V of Full differential operational amplifier A1 _o1+connect, V _ds-also by electric capacity C _cdssanother negative terminal inputting Single-end output operational amplifier A 3 with three ends inputs V _is1-be connected, V _ds-by another one electric capacity C _cmwith node V _sbe connected;

The anode of three end input Single-end output operational amplifier A 3 exports by a switch and node V _sbe connected, node V _sthen pass through two switches respectively at two DC voltage V _r+, V _r-be connected;

The output terminal V of Full differential operational amplifier A1 _o1+, V _o1-respectively by an electric capacity C _s1with the Full differential operational amplifier A2 input end V of next stage _i2+, V _i2-be connected.

Three ends of three described end input Single-end output operational amplifier A 3 are input as two negative terminal inputs and an anode input, and output is that an anode exports.

The input end V of Full differential operational amplifier A1 _i1+, V _i1-with output terminal V _o1-, V _o1+respectively by switch and common mode voltage V _cmbe connected;

The anode of three end input Single-end output operational amplifier A 3 inputs directly and common mode voltage V _cmbe connected, two negative terminal input V _is1-and V _is2-respectively by switch and common mode voltage V _cmbe connected, the anode of A3 exports also by switch and common mode voltage V _cmbe connected, this anode exports and is also connected to the ground after an external electric capacity simultaneously;

The input end V of Full differential operational amplifier A2 _i2+, V _i2-with output terminal V _o-, V _o+respectively by switch and common mode voltage V _cmbe connected.

The input end V of Full differential operational amplifier A2 _i2+by electric capacity C _f1with the output terminal V of Full differential operational amplifier A2 _o-be connected, simultaneously input end V _i2+also pass through the output terminal V of a switch and Full differential operational amplifier A2 _o-be connected; The input end V of Full differential operational amplifier A2 _i2-by electric capacity C _f1with the output terminal V of Full differential operational amplifier A2 _o+be connected, simultaneously input end V _i2-also pass through the output terminal V of a switch and Full differential operational amplifier A2 _o+be connected.

The movable port V of described capacitance type sensor _maalso pass through two switches respectively at two DC voltage V _r+, V _r-be connected, fixed port V _ds+and V _ds-respectively by switch and the voltage V producing electrostatic forcing _d+and V _d-be connected.

The output terminal V of described Full differential operational amplifier A1 _o1-with input end V _i1+polarity contrary, another output terminal V _o1+with input end V _i1-polarity contrary.

The output terminal V of described Full differential operational amplifier A2 _o-with input end V _i2+polarity contrary, another output terminal V _o+with input end V _i2-polarity contrary.

The anode of three ends input Single-end output operational amplifier A 3 exports that being also connected to the ground after an external electric capacity to be connected with any one DC voltage after branch road can adopt external capacitor replaces.

The invention has the beneficial effects as follows: can electrostatic force be applied at same port simultaneously and carry out capacitance detecting, realize multiplexed port function, different from time-multiplexed implementation, circuit of the present invention can not reduce the size of electrostatic force while realizing capacitance detecting, can provide the electrostatic force that one stable;

Adopt fully differential mode to realize applying electrostatic force and carrying out capacitance detecting, can effectively suppress power supply and common-mode noise, improve the accuracy rate of capacitance detecting and the stability of electrostatic force.

Accompanying drawing explanation

Fig. 1 is circuit connection diagram of the present invention;

Fig. 2 is working timing figure of the present invention.

Embodiment

Further illustrate technical scheme of the present invention below in conjunction with accompanying drawing, but the content that the present invention protects is not limited to the following stated.

As shown in Figure 1, a kind of multiplexed port interface circuit for capacitance type sensor, V _ds+, V _ds-the fixed port of corresponding capacitance type sensor respectively, V _mathe movable port of corresponding capacitance type sensor:

V _ds+by electric capacity C _cdswith an input end V of Full differential operational amplifier A1 _i1+be connected, by another one electric capacity C _fbwith an output terminal V of Full differential operational amplifier A1 _o1-connect, V _ds+also by electric capacity C _cdssthe negative terminal inputting Single-end output operational amplifier A 3 with three ends inputs V _is2-be connected, V _ds+by another one electric capacity C _cmwith node V _sbe connected;

V _ds-by electric capacity C _cdswith another input end V of Full differential operational amplifier A1 _i1-be connected, by another one electric capacity C _fbwith another output terminal V of Full differential operational amplifier A1 _o1+connect, V _ds-also by electric capacity C _cdssanother negative terminal inputting Single-end output operational amplifier A 3 with three ends inputs V _is1-be connected, V _ds-by another one electric capacity C _cmwith node V _sbe connected;

The anode of three end input Single-end output operational amplifier A 3 exports by a switch and node V _sbe connected, node V _sthen pass through two switches respectively at two DC voltage V _r+, V _r-be connected;

The output terminal V of Full differential operational amplifier A1 _o1+, V _o1-respectively by an electric capacity C _s1with the Full differential operational amplifier A2 input end V of next stage _i2+, V _i2-be connected.

Three ends of three described end input Single-end output operational amplifier A 3 are input as two negative terminal inputs and an anode input, and output is that an anode exports.

The input end V of described Full differential operational amplifier A1 _i1+, V _i1-with output terminal V _o1-, V _o1+respectively by switch and common mode voltage V _cmbe connected;

The anode of three end input Single-end output operational amplifier A 3 inputs directly and common mode voltage V _cmbe connected, two negative terminal input V _is1-and V _is2-respectively by switch and common mode voltage V _cmbe connected, the anode of A3 exports also by switch and common mode voltage V _cmbe connected, this anode exports and is also connected to the ground after an external electric capacity simultaneously;

The input end V of Full differential operational amplifier A2 _i2+, V _i2-with output terminal V _o-, _vO+respectively by switch and common mode voltage V _cmbe connected.

The input end V of Full differential operational amplifier A2 _i2+by electric capacity C _f1with the output terminal V of Full differential operational amplifier A2 _o-be connected, simultaneously input end V _i2+also pass through the output terminal V of a switch and Full differential operational amplifier A2 _o-be connected; The input end V of Full differential operational amplifier A2 _i2-by electric capacity C _f1with the output terminal V of Full differential operational amplifier A2 _o+be connected, simultaneously input end V _i2-also pass through the output terminal V of a switch and Full differential operational amplifier A2 _o+be connected.

The movable port V of described capacitance type sensor _maalso pass through two switches respectively at two DC voltage V _r+, V _r-be connected, fixed port V _ds+and V _ds-respectively by switch and the voltage V producing electrostatic forcing _d+and V _d-be connected.

The output terminal V of described Full differential operational amplifier A1 _o1-with input end V _i1+polarity contrary, another output terminal V _o1+with input end V _i1-polarity contrary.

The output terminal V of described Full differential operational amplifier A2 _o-with input end V _i2+polarity contrary, another output terminal V _o+with input end V _i2-polarity contrary.

The anode of described three ends input Single-end output operational amplifier A 3 exports that being also connected to the ground after an external electric capacity to be connected with any one DC voltage after branch road can adopt external capacitor replaces.

As shown in Figure 2, each end-point voltage of the present invention is respectively when each phase place:

1, T ₁phase place: V _ds+=V _d+, V _ds-=V _d-, V _i1+=V _cm, V _i1-=V _cm, V _o1+=Vcm, V _o1-=V _cm, V _i2+=V _cm, V _i2-=V _cm, V _ma=V _r-, V _is1-=V _cm, V _is2-=V _cm, V _s=V _r+; On this time sensor, the voltage of bottom crown is V _d+and V _d-, the voltage of middle plate is V _r-, so just reach the effect applying electrostatic force, the input and output of all operational amplifiers are simultaneously set to fixed level.

2, T ₂phase place: the capacitance change of inner sensor is very small during this period of time, like this and V _ds+and V _ds-all branch roads that two nodes are connected do not have electric current, so the voltage of the voltage of these two nodes can not change, that is: V _ds+=V _d+, V _ds-=V _d-, V _i1+=V _cm, V _i1-=V _cm, V _o1+=V _cm, V _o1-=V _cm, V _i2+=V _cm, V _i2-=V _cm, V _ma=V _r-, V _is1-=V _cm, V _is2-=V _cm, V _s=V _r+.

3, T ₃phase place: with T ₂phase place is similar, according to principle of charge conservation, obtains: V _ds+=V _d+, V _ds-=V _d-, V _i1+=V _cm, V _i1-=V _cm, V _o1+=V _cm, V _o1-=V _cm, V _i2+=V _cm, V _i2-=V _cm, V _ma=V _r-, V _is1-=V _cm, V _is2-=V _cm, V _s=V _r+.

4, T ₄phase place: the voltage V of sensor middle plate _maby V _r-→ V _r+, V simultaneously _is2-, V _is1-, V _i1+, V _i1-, V _i2+, V _i2-as the input end (for desirable operational amplifier, the input end current path of operational amplifier) of operational amplifier, the voltage of these points can not change, so V _i1+=V _cm, V _i1-=V _cm, V _i2+=V _cm, V _i2-=V _cm, V _is1-=V _cm, V _is2-=V _cm, according to derivation above, the input terminal voltage of operational amplifier does not change, so V _ds+, V _ds-also can not change, i.e. V _ds+=V _d+, V _ds-=V _d-; There are these conclusions, following result can have been calculated:

$V_S=\frac{C_S}{C_{\mathrm{cm}}}(V_{R-}-V_{R+})+V_{R+}$

$(V_{O1+}-V_{O1-})=\frac{2\mathrm{\ΔC}}{C_{\mathrm{fb}}}(V_{R+}-V_{R-})$

$(V_{O+}-V_{O-})=\frac{C_{S1}}{C_{F1}}\frac{2\mathrm{\ΔC}}{C_{\mathrm{fb}}}(V_{R+}-V_{R-})$

5, T ₅phase place: V _ds+=V _d+, V _ds-=V _d-, V _i1+=V _cm, V _i1-=V _cm, V _o1+=V _cm, V _o1-=V _cm, V _i2+=V _cm, V _i2-=V _cm, V _ma=V _r+, V _is1-=V _cm, V _is2-=V _cm, V _s=V _r-; At this moment on sensor, the voltage of bottom crown is V _d+and V _d-, the voltage of middle plate is V _r-, so just reach the effect applying electrostatic force, the input and output of all operational amplifiers are simultaneously set to fixed level.

6, T ₆phase place: the capacitance change of inner sensor is very small during this period of time, like this and V _ds+and V _ds-all branch roads that two nodes are connected do not have electric current, so the voltage of the voltage of these two nodes can not change, that is: V _ds+=V _d+, V _ds-=V _d-, V _i1+=V _cm, V _i1-=V _cm, V _o1+=V _cm, V _o1-=V _cm, V _i2+=V _cm, V _i2-=V _cm, V _ma=V _r+, V _is1-=V _cm, V _is2-=V _cm, V _s=V _r-.

7, T ₇phase place: with T ₆phase place is similar, according to principle of charge conservation, obtains: V _ds+=V _d+, V _ds-=V _d-, V _i1+=V _cm, V _i1-=V _cm, V _o1+=V _cm, V _o1-=V _cm, V _i2+=V _cm, V _i2-=V _cm, V _ma=V _r+, V _is1-=V _cm, V _is2-=V _cm, V _s=V _r-, the voltage of all nodes can not change in the moment that this phase place terminates.

8, T ₈phase place: the voltage V of sensor middle plate _maby V _r+→ V _r-, V simultaneously _is2-, V _is1-, V _i1+, V _i1-, V _i2+, V _i2-as the input end (for desirable operational amplifier, the input end current path of operational amplifier) of operational amplifier, the voltage of these points can not change, so V _i1+=V _cm, V _i1-=V _cm, V _i2+=V _cm, V _i2-=V _cm, V _is1-=V _cm, V _is2-=V _cm, according to derivation above, the input terminal voltage of operational amplifier does not change, so V _ds+, V _ds-also can not change, i.e. V _ds+=V _d+; V _ds-=V _d-; There are these conclusions, following result can have been calculated:

$V_S=\frac{C_S}{C_{\mathrm{cm}}}(V_{R+}-V_{R-})+V_{R-}$

$(V_{O1+}-V_{O1-})=\frac{2\mathrm{\ΔC}}{C_{\mathrm{fb}}}(V_{R-}-V_{R+})$

$(V_{O+}-V_{O-})=\frac{C_{S1}}{C_{F1}}\frac{2\mathrm{\ΔC}}{C_{\mathrm{fb}}}(V_{R+}-V_{R+})$

From phase place T ₁to T ₈namely intactly completing the function once applying electrostatic force and capacitance detecting, by repeating identical phase sequence, the function applying electrostatic force and capacitance detecting can be realized incessantly; According to description above, on known sensor, the voltage of bottom crown remains at V within a complete function cycle _d+and V _d-left and right, the electrostatic force this ensures that thering applying can not diminish because of multiplexed port.

Claims (6)

1., for a multiplexed port interface circuit for capacitance type sensor, it is characterized in that: V _ds+, V _dsthe fixed port of corresponding capacitance type sensor respectively, V _mathe movable port of corresponding capacitance type sensor:

V _ds+by electric capacity C _cdswith an input end V of Full differential operational amplifier A1 _i1+be connected, by another one electric capacity C _fbwith an output terminal V of Full differential operational amplifier A1 _o1connect, V _ds+also by electric capacity C _cdssthe negative terminal inputting Single-end output operational amplifier A 3 with three ends inputs V _is2be connected, V _ds+by another one electric capacity C _cmwith node V _sbe connected;

V _dsby electric capacity C _cdswith another input end V of Full differential operational amplifier A1 _i1be connected, by another one electric capacity C _fbwith another output terminal V of Full differential operational amplifier A1 _o1+connect, V _dsalso by electric capacity C _cdssanother negative terminal inputting Single-end output operational amplifier A 3 with three ends inputs V _is1be connected, V _dsby another one electric capacity C _cmwith node V _sbe connected;

The anode of three end input Single-end output operational amplifier A 3 exports by a switch and node V _sbe connected, node V _sthen pass through two switches respectively at two DC voltage V _r+, V _rbe connected;

The output terminal V of Full differential operational amplifier A1 _o1+, V _o1respectively by an electric capacity C _s1with the Full differential operational amplifier A2 input end V of next stage _i2+, V _i2be connected;

The input end V of described Full differential operational amplifier A1 _i1+, V _i1with output terminal V _o1, V _o1+respectively by switch and common mode voltage V _cmbe connected;

The anode of three end input Single-end output operational amplifier A 3 inputs directly and common mode voltage V _cmbe connected, two negative terminal input V _is1and V _is2respectively by switch and common mode voltage V _cmbe connected, the anode of A3 exports also by switch and common mode voltage V _cmbe connected, this anode exports and is also connected to the ground after an external electric capacity simultaneously;

The input end V of Full differential operational amplifier A2 _i2+, V _i2with output terminal V _o, V _o+respectively by switch and common mode voltage V _cmbe connected;

The movable port V of described capacitance type sensor _maalso by two switches respectively with two DC voltage V _r+, V _rbe connected, fixed port V _ds+and V _dsrespectively by switch and the voltage V producing electrostatic forcing _d+and V _dbe connected;

This multiplexed port interface circuit adopts fully differential mode apply electrostatic force at same port simultaneously and carry out capacitance detecting, realize multiplexed port function, the size of electrostatic force can not be reduced while realizing capacitance detecting, power supply and common-mode noise be can effectively suppress, the accuracy rate of capacitance detecting and the stability of electrostatic force improved.

2. a kind of multiplexed port interface circuit for capacitance type sensor according to claim 1, it is characterized in that: three ends of three described end input Single-end output operational amplifier A 3 are input as two negative terminal inputs and an anode input, and output is that an anode exports.

3. a kind of multiplexed port interface circuit for capacitance type sensor according to claim 1, is characterized in that: the input end V of described Full differential operational amplifier A2 _i2+by electric capacity C _f1with the output terminal V of Full differential operational amplifier A2 _obe connected, simultaneously input end V _i2+also pass through the output terminal V of a switch and Full differential operational amplifier A2 _obe connected; The input end V of Full differential operational amplifier A2 _i2by electric capacity C _f1with the output terminal V of Full differential operational amplifier A2 _o+be connected, simultaneously input end V _i2also pass through the output terminal V of a switch and Full differential operational amplifier A2 _o+be connected.

4. a kind of multiplexed port interface circuit for capacitance type sensor according to claim 1, is characterized in that: the output terminal V of described Full differential operational amplifier A1 _o1with input end V _i1+polarity contrary, another output terminal V _o1+with input end V _i1polarity contrary.

5. a kind of multiplexed port interface circuit for capacitance type sensor according to claim 3, is characterized in that: the output terminal V of described Full differential operational amplifier A2 _owith input end V _i2+polarity contrary, another output terminal V _o+with input end V _i2polarity contrary.

6. a kind of multiplexed port interface circuit for capacitance type sensor according to claim 1, is characterized in that: the anode of described three ends input Single-end output operational amplifier A 3 exports that being also connected to the ground after an external electric capacity to be connected with any one DC voltage after branch road can adopt external capacitor replaces.