CN106059510A - Method and device for eliminating direct current drift output by capacitance coupling amplification circuit - Google Patents

Abstract

The invention provides a device and a method for eliminating DC (Direct Current) drift output by a capacitance coupling amplification circuit. The device comprises a DC drift obtaining unit and a DC drift processing unit. The DC drift obtaining unit is connected to the output end of the capacitance coupling amplification circuit and is used for obtaining the DC drift of an output signal and transmitting the obtained signal to the DC drift processing unit; and the DC drift processing unit processes the signal, generates a DC elimination signal required for eliminating the DC drift and is connected to a grounding point of the input end of the capacitance coupling amplification circuit; and the grounding point is not grounded. As elimination of the output DC drift is carried out actively at the input stage of the capacitance coupling amplification circuit through changing the ground level, use of a switch is avoided, and the device and the method for eliminating the DC drift output by the capacitance coupling amplification circuit have the advantages of improving the working state of the amplifying circuit per se, avoiding influence from the input coupling capacitance and being easy to realize.

Description

A kind of device and method eliminating Capacitance Coupled amplifying circuit output DC shift

Technical field

The present invention relates to the dress that sensing circuit output signal DC shift eliminates when measuring low-frequency voltage or electric field signal Put and method, particularly to the device and method of a kind of DC shift eliminating Capacitance Coupled amplification circuit output end.

Background technology

Low frequency (0.1Hz 10kHz) electrical signal detection method has contact and contactless two big classes.At non-cpntact measurement In, generally use capacitive coupling to detect, input coupling electric capacity is picofarad range, in order to by signal preferably coupling Close circuit, input impedance is required the highest, it usually needs lucky ohm level.But, high input impedance and little input capacitance, hold Easily cause capacitance charge to accumulate, and then cause DC shift by sense amp circuit input at outfan.Electric capacity is the least, directly Stream drift is the most obvious, and accumulates DC shift in the case of input impedance is high over time and have increase tendency.Such directly Stream drift is likely to result in amplifier and exports close to running voltage, is unfavorable for long-term work.Simultaneously as amplifying circuit output is straight Stream level is higher, such as the supply voltage close to amplifying circuit, the dynamic range making output signal is diminished, and reduces the letter of system Make an uproar ratio, impact detection performance.

Current solution mostly is all kinds of high pass filters of use or band filter, directly filters in amplifying circuit rear class Except the flip-flop in output signal.But such solution is the passive existing direct current filtering output signal in rear class Drift, can not fundamentally change the duty of prime Capacitance Coupled amplifying circuit.If Capacitance Coupled output DC shift Exist and slowly increase or drift, detection dynamic range can be reduced, even cause detection distorted signals, even if now to output signal Carry out passive direct current to filter and also cannot obtain undistorted detection signal.For this reason, it may be necessary to use actively direct current elimination method, change The duty of kind amplifying circuit self.Actively direct current elimination method uses switch to reset or correlated-double-sampling realization, but For Capacitance Coupled amplifying circuit, input coupling electric capacity is picofarad range, and usually less than gigohm nurse turns off impedance switch, connects this Cannot normally work after the input coupling electric capacity that sample is little, therefore need to use the shutoff impedance switch of more than hundred gigohm nurses, this is usual It is difficult to, limits switch and reset or the active direct current elimination realization of correlated-double-sampling.For this reason, it may be necessary to a kind of method is avoided making Realize actively Capacitance Coupled amplifying circuit itself with switch to export the suppression of DC shift and filter, improve amplifying circuit self Duty.

Summary of the invention

In order to overcome above-mentioned deficiency of the prior art, the present invention proposes a kind of logical in Capacitance Coupled amplifying circuit input stage Cross change ground level actively to carry out exporting the device and method that DC shift eliminates.

For achieving the above object, the technical scheme that the present invention proposes is:

A kind of device eliminating Capacitance Coupled amplifying circuit output DC shift, including DC shift acquiring unit and direct current Drift processing unit, described DC shift acquiring unit is connected to the outfan of Capacitance Coupled amplifying circuit, is used for obtaining output The DC shift of signal, the signal of acquisition is transferred to DC shift processing unit by DC shift acquiring unit；Described direct current floats Move processing unit signal is processed, produce the direct current needed for eliminating DC shift and eliminate signal and be linked into described electric capacity coupling Close at the earth point of input amplifier, earth-free at this earth point.

A kind of method eliminating Capacitance Coupled amplifying circuit output DC shift of the present invention, comprises the steps:

(1) DC shift obtains: obtain the DC shift of Capacitance Coupled amplifying circuit output signal；

(2) DC shift processes: the DC shift signal obtaining step (1) processes, and produces and eliminates DC shift Required direct current eliminates signal；

(3) DC shift eliminates: the direct current produced in step (2) elimination signal is linked into Capacitance Coupled amplifying circuit defeated Enter at the earth point of level, earth-free at this earth point；

Further, the method also includes that step (4) DC shift confirms: obtain Capacitance Coupled amplifying circuit output signal DC shift, detection after step (3) amplifying circuit output DC shift situation, if the elimination degree of DC shift is not Enough, then repeat step (2) to (4) until meeting requirement.

Described step (1) utilizes DC measurement instrument or low pass filter to obtain the DC shift of output signal.

Described step (2) utilizes regulated power supply directly to export required direct current and eliminates signal, or utilizes amplifying circuit Or low pass filter carries out amplitude and Phase Processing to the DC shift signal obtained, produce direct current and eliminate signal.

DC shift can not pass through in time mainly due to the electric charge of input end capacitor accumulation in Capacitance Coupled amplifying circuit Resistance to earth is released and is produced, and then causes DC shift by input amplifier at outfan.Therefore, input is changed Ground level can alleviate on source and even eliminate this situation.The marked feature of the inventive method is: change input stage Ground level actively eliminates output DC shift, it is to avoid switch uses, and has the duty improving amplifying circuit self, not by defeated Enter to couple capacitive effect, it is easy to accomplish advantage.

Accompanying drawing explanation

Fig. 1 is the FB(flow block) of the inventive method.

Fig. 2 is the enforcement structure chart of present example 1.

Fig. 3 is the enforcement structure chart of present example 2.

Detailed description of the invention

Clearer by making the present invention be put forward technical scheme, below in conjunction with the accompanying drawings and the specific embodiments the present invention is carried out Describe in detail.

Being embodied as of the inventive method can be divided into automatic cancellation and manual cancellation.For the side of elimination automatically Method refers to use all kinds of low pass filters to be amplified the DC shift of circuit output in step (1), in step (2), adopts The process that the DC shift realizing obtaining step (1) with all kinds of low pass filters does in phase and amplitude, thus obtain required Direct current eliminates signal.Manual removing method is referred to be obtained by apparatus measures amplifying circuit output signal in step (1) DC shift, uses regulated power supply directly to export required direct current in step (2) and eliminates signal.

Embodiment 1

The present embodiment is a Capacitance Coupled bootstrapping high resistant amplifying circuit output manual cancellation of DC shift, physical circuit Structure sees Fig. 2, is described as follows:

(1) DC shift obtains: obtaining DC shift by apparatus measures amplifying circuit output signal, instrument can use Circuit tester, oscillograph etc..In the present embodiment, the oscilloscope measurement output signal of the DS1104B model of use RIGOL company is straight Stream size.

(2) DC shift processes: uses the regulated power supply of GW company GPD-3303S model directly to export required direct current and disappears Except signal, measuring instrument after adjusting one less DC quantity of the tentative output of source of stable pressure, is utilized to observe amplification circuit output end Change, determines size and the direction of source of stable pressure output direct current signal.Find that using source of stable pressure to export one obtains step with direct current The equidirectional direct current signal of direct current signal obtained in rapid can reach to export the purpose that DC shift reduces.

(3) DC shift eliminates: the direct current produced in step (2) elimination signal is linked into Capacitance Coupled amplifying circuit defeated Enter the R of level₂And R₃Common place, this common place is earth-free.

(4) DC shift confirms: the method detection amplifying circuit output DC shift situation of applying step (1), if directly Stream drift elimination degree is inadequate, repeats step (2) to (4) until meeting requirement.

Embodiment 2

The present embodiment is that a Capacitance Coupled bi-directional voltage stabilizing pipe realizes the high resistant amplifying circuit output DC shift side of elimination automatically Formula, particular circuit configurations sees Fig. 3, is described as follows:

(1) DC shift obtains: use low pass filter to obtain the DC shift of Capacitance Coupled amplifying circuit output signal. Resistance and Capacitance Coupled Amplification Circuit output signal is obtained output by a conventional second order active low pass filter with gain DC shift in signal, and determine the polarity of DC quantity, wherein resistance R₃With R₄、R₅With R₆, electric capacity C₂With C₃With operation amplifier Device A₂Constitute the active low-pass filter of band gain.

Using second order active low pass filter, its transmission function is as follows herein:

$A\left(s\right)=\frac{A_{VF}}{1+(3-A_{VF})sCR+{\left(sCR\right)}^2}---\left(1\right)$

Wherein:

A_VF=1+R₆/R₅ (2)

Its cut-off frequency is:

$f=\frac{1}{2\mathrm{\π}RC}---\left(3\right)$

C=C₂=C₃ (4)

R=R₃=R₄ (5)

(2) DC shift processes: the DC shift signal obtaining step (1) carries out suitably amplitude and Phase Processing and produces Raw direct current eliminates signal, takes the see-saw circuit of band gain to realize.Resistance R₇With R₈With operational amplifier A₃Constitute anti-phase putting Big device.

Wherein resistance R₇With R₈Determine the gain of see-saw circuit:

A=R₈/R₇ (6)

(3) DC shift eliminates: the direct current produced in step (2) elimination signal is linked into Capacitance Coupled amplifying circuit defeated Enter the R of level₁With bi-directional voltage stabilizing pipe D₁With D₂Common place, this common place is earth-free.

(4) DC shift confirms: the method detection amplifying circuit output DC shift situation of applying step (1), if directly Stream drift elimination degree is inadequate, repeats step (2) to (4) until meeting requirement.

Amplifying circuit for embodiment 1, naturally it is also possible to use the automatic removing method in embodiment 2.Equally, implement Example 2 amplifying circuit can also use the manual removing method in embodiment 1.The method that DC shift in two embodiments obtains Can also be general.

It should be noted that above-described embodiment, be not used for limiting protection scope of the present invention, in technique scheme Equivalents or replacement done by the basis of each fall within the scope that the claims in the present invention are protected.

Claims (8)

1. eliminate a device for Capacitance Coupled amplifying circuit output DC shift, float including DC shift acquiring unit and direct current Move processing unit, it is characterised in that described DC shift acquiring unit is connected to the outfan of Capacitance Coupled amplifying circuit, is used for Obtain the DC shift of output signal, and the signal of acquisition is transferred to DC shift processing unit；Described DC shift processes Signal is processed by unit, produces the direct current needed for eliminating DC shift and eliminates signal and be linked into the amplification of described Capacitance Coupled At the earth point of circuit input end, earth-free at this earth point.

A kind of device eliminating Capacitance Coupled amplifying circuit output DC shift the most according to claim 1, its feature exists In, this device also includes that DC shift confirmation unit, described DC shift confirmation unit are connected to Capacitance Coupled amplifying circuit Outfan, is used for detecting the removal situation of DC shift.

A kind of device eliminating Capacitance Coupled amplifying circuit output DC shift the most according to claim 1 and 2, its feature Being, described DC shift acquiring unit uses DC measurement instrument or low pass filter to obtain the direct current drift of output signal Move.

A kind of device eliminating Capacitance Coupled amplifying circuit output DC shift the most according to claim 1 and 2, its feature Being, described DC shift processing unit uses regulated power supply, amplifying circuit or low pass filter to produce direct current and eliminates signal.

5. the method eliminating Capacitance Coupled amplifying circuit output DC shift, it is characterised in that comprise the steps:

(1) DC shift obtains: obtain the DC shift of Capacitance Coupled amplifying circuit output signal；

(2) DC shift processes: the DC shift signal obtaining step (1) processes, and produces needed for eliminating DC shift Direct current eliminate signal；

(3) DC shift eliminates: the direct current produced in step (2) is eliminated signal and is linked into Capacitance Coupled amplifying circuit input stage Earth point at, earth-free at this earth point.

A kind of method eliminating Capacitance Coupled amplifying circuit output DC shift the most according to claim 5, its feature exists In, the method also includes that step (4) DC shift confirms: obtain the DC shift of Capacitance Coupled amplifying circuit output signal, inspection Survey the situation of amplifying circuit output DC shift after step (3), if the elimination degree of DC shift is inadequate, then repeat step (2) to (4) until meeting requirement.

7. according to a kind of method eliminating Capacitance Coupled amplifying circuit output DC shift described in claim 5 or 6, its feature Being, described step (1) utilizes DC measurement instrument or low pass filter to obtain the DC shift of output signal.

8. according to a kind of method eliminating Capacitance Coupled amplifying circuit output DC shift described in claim 5 or 6, its feature Being, described step (2) utilizes regulated power supply directly to export required direct current and eliminates signal, or utilizes amplifying circuit or low Bandpass filter carries out amplitude and Phase Processing to the DC shift signal obtained, and produces direct current and eliminates signal.