CN103884893A - Shunt linearity isolation circuit and oscilloscope thereof - Google Patents
Shunt linearity isolation circuit and oscilloscope thereof Download PDFInfo
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- CN103884893A CN103884893A CN201210559700.5A CN201210559700A CN103884893A CN 103884893 A CN103884893 A CN 103884893A CN 201210559700 A CN201210559700 A CN 201210559700A CN 103884893 A CN103884893 A CN 103884893A
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Abstract
The invention provides a shunt linearity isolation circuit which is applicable to measuring equipment such as an oscilloscope and the like. The shunt linearity isolation circuit comprises a low-frequency amplification circuit, a first analog-to-digital converter, a digital isolator, a high-frequency subtraction amplification circuit, a transformer, a second analog-to-digital converter and a control processing circuit. An input signal is decomposed into a direct current to low frequency portion and a low frequency to high frequency portion by utilizing the low-frequency amplification circuit and the high-frequency subtraction amplification circuit, wherein the low frequency portion is sampled by utilizing the first analog-to-digital converter and then is output to the control processing circuit through the digital isolator. Since sampling-first-isolating-later mode is utilized, the selecting range of the isolator in a low-frequency path is expanded. After the high frequency portion is isolated by utilizing the transformer, sampled through the second analog-to-digital converter and then output to the control processing circuit, so that high sampling rate and high bandwidth of the oscilloscope are realized. The shunt linearity isolation circuit can be applied to the measuring equipment such as the oscilloscope and the like conveniently.
Description
Technical field
The present invention relates to electronic metering equipment, particularly a kind of shunt circuit linearity insulating circuit and oscillograph thereof.
Background technology
Buffer circuit can arrive outgoing side by the electrical signal transfer of input side, but on electric, isolates between input side and outgoing side, insulate in other words conj.or perhaps, only has a less electric capacity between input side and outgoing side.Buffer circuit can improve the common-mode rejection ratio while measurement, reduces and disturbs, and improves signal quality, also can insulation risks voltage, and protection equipment and personal safety.In the time that hyperchannel oscillograph is measured simultaneously, channel separation can also be measured the signal of multiple different common mode voltages, prevents from causing altogether short circuit accident because of interchannel.
From the frequency response of processed signal and buffer circuit, buffer circuit can be divided into digital buffer circuit and linear or simulation buffer circuit.Numeral buffer circuit can only be isolated high and low level signal, i.e. digital signal, belongs to switching signal, technical easy realization.Circuit linearity insulating circuit is sometimes also referred to as isolated amplifier, and its output signal and input signal are linear, can transfer die analog signal, and the frequency response of circuit can be from DC to very high frequency.The technical more difficult realization of circuit linearity insulating circuit of high bandwidth (more than hundreds of MHz).And realize the circuit linearity insulating circuit with very high DC precision, and can on oscillograph, realize voltage table or function of multimeter, there is good using value, but there is technically higher difficulty.
Circuit linearity insulating circuit, conventional have following several mode:
Linear optical coupling buffer circuit, separation principle and the common optical coupler of linear optical coupling do not have difference, just the single-shot list of common optical coupler are received to pattern and change a little, increase by one and accept circuit for feedback for the light feeding back.Like this, be all nonlinear although two light are accepted circuit, the nonlinear characteristic that two light is accepted circuit is all the same.Like this, just can offset the non-linear of through path by the non-linear of feedback network, thereby reach the object that realizes linear isolation.Linear optical coupling can be realized the very high linearity, can isolate direct current signal, but signal bandwidth maximum can only arrive several MHz.
Transformer isolation circuit, utilizes electromagnetic induction principle, makes the electric insulation completely of primary side and secondary side, makes loop isolation.Transformer, according to the difference of the difference of core material and winding method, can be realized very high frequency is isolated.But due to electromagnetic induction, transformer can not be isolated direct current and low frequency signal, general transformer can be isolated minimumly can get at kHz rank.
Isolated amplifier device, has some integrated isolated amplifier chips at present, on the market as the AD203 of ADI company, AD215.Such devices use transformer is isolated, and input is carried out to linear modulation and become digital signal, then utilizes transformer to isolate digital signal, and the signal after isolation passes through demodulation again, generates the simulating signal after isolation.This class has the higher linearity, but bandwidth is generally very low, and maximum only have hundreds of kHz at present.
For solving the shortcoming of above-mentioned device, prior art has also provided multiple solution, below just several solutions are wherein introduced:
The patent that A, the patent No. are CN96101007.X, provides a solution, realizes block diagram as shown in Figure 1.
The amplifier that it uses two different bandwidths, is divided into high-frequency path and low frequency path by input signal, and low frequency path is used linear optical coupling to isolate, and high-frequency path uses transformer to isolate.Transformer time limit is used two windings, produce single spin-echo differential signal+Vout and-Vout.Low frequency signal after isolation is adjusted and single-ended transfer difference amplifier through gain, and the signal of output is as the biasing on transformer time limit.Low frequency channel, due to the time delay of linear optical coupling, causes the signal after stack, and in high and low frequency junction, amplitude-frequency response subsides, adopt circuit 48,52,50,54 to compensate, make amplitude-frequency response in high and low frequency junction, suitable lifting, has realized the flatness of amplitude-frequency response.
This patent can realize the circuit linearity insulating circuit of large bandwidth, but has following shortcoming:
1, because transformer time limit has adopted two windings, as the both positive and negative polarity of output difference sub-signal, be difficult to ensure the same phase of card both positive and negative polarity, increase the difficulty of transformer winding.
2, adopt the isolation of linear optical coupling as low frequency path, the time delay in low frequency path causes frequency response unevenness, has adopted circuit 48,52,50,54 to compensate, and because capacitor element is discrete, is difficult to ensure that card differential signal both positive and negative polarity is in full accord.
3, because transformer should meet low-limit frequency and low frequency path can superpose, meet again highest frequency as far as possible large, due to the restriction of transformer, the bandwidth that can realize is little, and maximum can get at 100MHz left and right.
The patent that B, the patent No. are US5834973, does not have the shortcoming of patent CN96101007.X, and it realizes block diagram as shown in Figure 2.
This patent is used the amplifier of two different bandwidths, and low bandwidth amplifier is realized low frequency path, and low frequency path is used linear optical coupling to isolate.The output of low bandwidth amplifier is through 124,126 dividing potential drop, be connected to subtraction circuit one end that high bandwidth amplifier forms, subtraction circuit deducts input signal the signal in low frequency path, the high-frequency signal of output is connected to the former limit of transformer, and the signal plus in this high-frequency signal and low frequency path is input signal.The linear optical coupling circuit in low frequency path has certain gain, to offset the damping capacity of low frequency signal of subtraction circuit input.High-frequency signal uses transformer to isolate, and the output of transformer time limit output and linear optical coupling, through adding circuit, produces the signal after isolation, thereby realizes the linear isolation to signal.
This patent preferably resolves the problem of transformer winding, but has following shortcoming:
1, adopt the isolation of linear optical coupling as low frequency path, there is certain time delay in low frequency path, and direct and high frequency road strength output is added, and can make low-and high-frequency frequency junction amplitude-frequency response subside, this patent is not introduced compensating circuit, the amplitude-frequency response unevenness of output signal.
2,, because transformer should meet low-limit frequency and low frequency path can superpose, meet again highest frequency as far as possible large.Due to the restriction of transformer, the bandwidth that can realize is little, and maximum can get at 200MHz left and right.
The patent that C, the patent No. are CN200610154738.9, has carried out concrete refinement by the implementation method of patent US5834973, and has solved its shortcoming, and delay compensating chain is provided, and it realizes block diagram as shown in Figure 3.
The realization approach of this patent and US5834973 is consistent, but has carried out circuit refinement, has increased the delay compensating chain 102,103,104 in low frequency path.Input signal is through low-frequency amplifier circuit 100, and output is connected to subtraction circuit 101, and subtraction output is high-frequency signal.High-frequency signal is isolated through transformer 26, and the signal after isolation is connected to circuit 105.Low frequency signal is isolated through linear optical coupling circuit 102, after low frequency signal isolation, carry out compensation of delay through delay compensating chain 103,104, and carry out necessary amplification, make the amplitude in low frequency path consistent with high-frequency path, signal after output and high-frequency isolation after compensation is through adding circuit 105, and the signal after synthetic isolation, realizes the linear isolation to signal.
This patent circuit is more detailed, the shortcoming of patent before can solving, but also there is following shortcoming:
1, because transformer should meet low-limit frequency and low frequency path can superpose, meet again highest frequency as far as possible large, due to the restriction of transformer, the bandwidth that can realize is little, and maximum can get at 200MHz left and right.
2, the delay compensating chain 103 or 22,24,29,30 of mentioning in patent, the actual amplitude-frequency depression that can not solve low frequency and high-frequency path crossover frequency place.Because electric capacity 24,30 shown in amplifier circuit, played the effect of low pass, can only allow low frequency path high frequency relatively and low frequency become lower, and can not play the effect of suitable lifting high frequency.Circuit 103, reality is also RC low pass circuit, can not play equally the effect of suitable lifting high frequency.
3, because the delay compensating chain providing is inoperative, the output amplitude-frequency response unevenness of circuit linearity insulating circuit.
4, low frequency path circuit complexity.
In sum, currently available technology major defect is that the circuit linearity insulating circuit bandwidth that can realize is low, cannot realize the isolation oscillograph of larger bandwidth.And, the frequency response depression problem that linear optical coupling circuit can bring.
Summary of the invention
Fundamental purpose of the present invention is to solve problems of the prior art, and a kind of shunt circuit linearity insulating circuit and oscillograph thereof are provided.
The object of the invention is to be achieved by following technical proposals:
A kind of shunt circuit linearity insulating circuit, is characterized in that, comprising: low-frequency amplifier circuit, the first analog to digital converter, digital isolator, high frequency subtraction amplification circuit, transformer, the second analog to digital converter and control treatment circuit;
Input signal is inputted respectively the positive input terminal of described low-frequency amplifier circuit and high frequency subtraction amplification circuit;
Described low-frequency amplifier circuit, for input signal is carried out to filtering, the low frequency signal in output input signal; Described low frequency signal is inputted respectively the negative input end of described the first analog to digital converter and high frequency subtraction amplification circuit;
Described high frequency subtraction circuit, for the input signal of described input being deducted to the low frequency signal of described low-frequency amplifier circuit input, to export high-frequency signal;
Described the first analog to digital converter, is connected with described low-frequency amplifier circuit, for the low frequency signal of low-frequency amplifier circuit input is sampled, and by the low-frequency digital signal input digital isolator after sampling;
Described digital isolator, is connected with described the first analog to digital converter, for the low frequency signal of low-frequency amplifier circuit output is isolated, and the low-frequency digital signal of exporting after isolation is inputted to described control treatment circuit;
Described transformer, is connected with described high frequency subtraction circuit, for the high-frequency signal of high frequency subtraction circuit input is isolated, and the high-frequency signal of exporting after isolation is inputted to described the second analog to digital converter;
Described the second analog to digital converter, is connected with described transformer, for the high-frequency signal of exporting after transformer isolation is sampled, and by the high-frequency digital signal input control treatment circuit after sampling;
Described control treatment circuit, for the low-frequency digital signal after the high-frequency digital signal after described sampling and isolation is added, generates the rear output signal of isolation, and output.
Also comprise buffer circuit, between described transformer and described the second analog to digital converter, the high-frequency signal of exporting afterwards for strengthening described isolation, to drive the second analog to digital converter.
Described transformer adopting line transformer winding method; The armature winding of this transformer and secondary winding adopt twisted-pair feeder, parallel lines or coaxial cable.
Described control treatment circuit, comprising: interpolator and totalizer; Wherein,
Described interpolator, accesses the low-frequency digital signal after described isolation, for the low-frequency digital signal after the isolation of input is carried out to interpolation arithmetic, obtains low-frequency digital signal after interpolation;
Described totalizer, for low-frequency digital signal after the high-frequency digital signal after described sampling and interpolation is added, generates output signal after described isolation.
Described control treatment circuit, comprising: timer, interpolator and totalizer; Wherein,
Described timer, accesses the high-frequency digital signal after described sampling, for the high-frequency digital signal after the sampling of input is carried out to time delay, obtains high-frequency digital signal after time delay;
Described interpolator, accesses the low-frequency digital signal after described isolation, for the low-frequency digital signal after the isolation of input is carried out to interpolation arithmetic, obtains low-frequency digital signal after interpolation;
Described totalizer, is connected with interpolator with described timer device, for low-frequency digital signal after high-frequency digital signal and interpolation after described time delay is added, generates output signal after described isolation.
An oscillograph with shunt circuit linearity insulating circuit, comprising: decay switching module, input stage buffering and adding circuit, programmable amplifier, control processing module and D/A modular converter; Input signal is sent to control processing module through decay switching module, input stage buffering and adding circuit, programmable amplifier successively; Control processing module gain control signal is sent to this programmable amplifier; Control processing module and also offset signal is sent to input stage buffering and adding circuit through D/A modular converter; It is characterized in that:
Any one shunt circuit linearity insulating circuit be serially connected with claim 1 to 4 between described programmable amplifier and control processing module in, to realize signal isolation object;
Described control treatment circuit is arranged among described control processing module;
Between described control processing module and programmable amplifier, and control between processing module and D/A modular converter, be also serially connected with digital isolator, this digital isolator and described shunt circuit linearity insulating circuit parallel connection.
Described programmable amplifier is output as differential signal; Between this programmable amplifier and described shunt circuit linearity insulating circuit, be serially connected with difference and turn single-end circuit, so that described differential signal is converted to single-ended signal.
Beneficial effect of the present invention is:
1, circuit form is simple, does not need low-frequency compensation circuit.
2, can realize bandwidth more than DC to 200MHz.
3, there is very high direct current degree of accuracy.
4, can be applied to the linear isolation of single-ended signal, can be also differential signal.
5, realize the isolation oscillograph that passage is isolated mutually.
Accompanying drawing explanation
Accompanying drawing described herein is used to provide a further understanding of the present invention, forms the application's a part, does not form limitation of the invention.In the accompanying drawings:
Fig. 1 is existing buffer circuit example one structural drawing;
Fig. 2 is existing buffer circuit example two structural drawing;
Fig. 3 is existing buffer circuit example three structural drawing;
Fig. 4 is shunt circuit linearity insulating circuit structural drawing;
Fig. 5 is for controlling treatment circuit structural drawing;
Fig. 6 is shunt circuit linearity insulating circuit embodiment 1 structural drawing;
Fig. 7 (A) low-frequency amplifier circuit form 1 structural drawing;
Fig. 7 (B) low-frequency amplifier circuit form 2 structural drawing;
Fig. 7 (C) low-frequency amplifier circuit form 3 structural drawing;
Fig. 7 (D) low-frequency amplifier circuit form 4 structural drawing;
Fig. 8 (A) is input signal figure;
Fig. 8 (B) is output signal frequency response figure;
Fig. 8 (C) is square-wave signal low frequency path and high-frequency path output schematic diagram under time domain;
Fig. 9 is shunt circuit linearity insulating circuit embodiment 2 structural drawing;
Figure 10 is shunt circuit linearity insulating circuit embodiment 3 structural drawing;
Figure 11 is shunt circuit linearity insulating circuit embodiment 3 amplifier architecture figure;
Figure 12 is the structured flowchart of existing oscilloscope analog front end;
Figure 13 is the oscilloscope architecture figure of application shunt circuit linearity insulating circuit.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with embodiment and accompanying drawing, the present invention is described in further details.At this, exemplary embodiment of the present invention and explanation thereof are used for explaining the present invention, but not as a limitation of the invention.
For existing problem in aforementioned prior art, the present invention is by being divided into input signal low frequency and high frequency two parts, and different frequency part is isolated by different independent paths respectively, thereby realizes high bandwidth linear isolation.Fig. 4 is shunt circuit linearity insulating circuit structural drawing of the present invention.As shown in the figure, this shunt circuit linearity insulating circuit, comprising: low-frequency amplifier circuit, the first analog to digital converter, digital isolator, high frequency subtraction amplification circuit, transformer, the second analog to digital converter and control treatment circuit;
Input signal is inputted respectively the positive input terminal of described low-frequency amplifier circuit and high frequency subtraction amplification circuit;
Described low-frequency amplifier circuit, for input signal is carried out to filtering, the low frequency signal in output input signal; Described low frequency signal is inputted respectively the negative input end of described the first analog to digital converter and high frequency subtraction amplification circuit;
Described high frequency subtraction circuit, for the input signal of described input being deducted to the low frequency signal of described low-frequency amplifier circuit input, to export high-frequency signal;
Described the first analog to digital converter, is connected with described low-frequency amplifier circuit, for the low frequency signal of low-frequency amplifier circuit input is sampled, and by the low-frequency digital signal input digital isolator after sampling;
Described digital isolator, is connected with described the first analog to digital converter, for the low frequency signal of low-frequency amplifier circuit output is isolated, and the low-frequency digital signal of exporting after isolation is inputted to described control treatment circuit;
Described transformer, is connected with described high frequency subtraction circuit, for the high-frequency signal of high frequency subtraction circuit input is isolated, and the high-frequency signal of exporting after isolation is inputted to described the second analog to digital converter;
Described the second analog to digital converter, is connected with described transformer, for the high-frequency signal of exporting after transformer isolation is sampled, and by the high-frequency digital signal input control treatment circuit after sampling;
Described control treatment circuit, for the low-frequency digital signal after the high-frequency digital signal after described sampling and isolation is added, generates the rear output signal of isolation, and output.
Due to, the first analog to digital converter and the second analog to digital converter be respectively used to sample low frequency and high-frequency signal in the present invention.Therefore, the sampling rate of its selected analog to digital converter requires also different.This first analog to digital converter adopts low speed analog to digital converter, and this second analog to digital converter adopts high-speed AD converter.
Due to the difference of sampling rate, the sampling interval of the data of the first analog to digital converter output is more much larger than the interval of the second analog to digital converter output data, so the data of the first analog to digital converter output need to be carried out interpolation arithmetic in control processing module inside, are interpolated to and the same data break of the second analog to digital converter data.Because the time delay of slow-path may be different with high speed path, so being carried out to necessary time delay, the data of the second analog to digital converter regulate, make low-and high-frequency data align in sampling instant.Then carry out sum operation, the data after addition are exactly the sampled data of input signal.
For these reasons, the present invention designs described control treatment circuit as shown in Figure 5.Described control treatment circuit, comprising: timer, interpolator and totalizer; Wherein,
Described timer, accesses the high-frequency digital signal after described sampling, for the high-frequency digital signal after the sampling of input is carried out to time delay, obtains high-frequency digital signal after time delay;
Described interpolator, accesses the low-frequency digital signal after described isolation, for the low-frequency digital signal after the isolation of input is carried out to interpolation arithmetic, obtains low-frequency digital signal after interpolation;
Described totalizer, is connected with interpolator with described timer device, for low-frequency digital signal after high-frequency digital signal and interpolation after described time delay is added, generates output signal after described isolation.
In specific implementation process, above-mentioned control treatment circuit can be arranged in oscillographic control processing module, to simplify oscilloscope architecture.
Give an example as one, between low speed sampled data and high-speed sampling data, there is no time delay, control treatment circuit and can not establish timer.
In above-mentioned shunt circuit linearity insulating circuit, utilize low-frequency amplifier circuit and high frequency subtraction circuit, input signal is resolved into direct current tremendously low frequency part and low frequency tremendously high frequency part.Low frequency part adopts high-precision ADC to sample, and through digital isolator part, exports the digital signal after sampling to FPGA.HFS uses transformer to isolate, and the signal after isolation, through necessary ADC driving circuit, exports the second analog to digital converter to and samples, and realizes oscillographic high sampling rate and bandwidth, and the second analog to digital converter output is connected to FPGA.FPGA controls treatment circuit, and the signal of FPGA inside after to the second analog to digital converter and the first analog to digital converter collection carries out necessary compensation of delay and interpolation arithmetic, is then added processing, obtains the digital signal after input signal sampling.Thereby realize the linear isolation to input signal.Digital signal after this sampling has pinpoint accuracy to the low frequency part of input signal, can realize accurate voltage measurement function.If this buffer circuit uses at oscillograph front end, can realize the real isolation oscillograph with function of voltmeter.If increase a current source that can arrange at oscillograph input end, can also realize function of multimeter such as resistance measurement, break-make drive test amount, diode polarity measurement.
If low frequency path adopts traditional mode of first isolating post-sampling, need the isolating device of a high linearity.And can realize the isolation of direct current tremendously low frequency, and only having at present linear optical coupling, it selects face relative narrower.And the present invention adopts the mode of first sampling and isolating afterwards, isolator can use digital isolator, selectable leeway is a lot, the data signal rate of at present general digital isolator part can arrive hundred Mbps ranks, the output data of isolating the first analog to digital converter are no problem, and the output of a lot of the first analog to digital converters is all serial data, as SPI, IIC interface, generally only have several data lines, do not need a lot of digital isolators just can realize.Therefore, the present invention has expanded the isolator range of choice in its low frequency path by above-mentioned design.
Above-mentioned the first analog to digital converter adopts high-precision adc, and high precision the first analog to digital converter is generally selected 16 above ADC, and for example 24 sigma-delta ADC, can realize the sampling with high precision of direct current (DC) to hundreds of kHz signal.The impacts such as the ADC of 24 samples to low frequency signal, the noise of consideration front end, if can realize the efficiently sampling figure place of 18, can realize 218 grades (262144) accurately to sample, and can realize the high-accuracy voltage measurement that is greater than 5 half.Because the first analog to digital converter has adopted high-precision adc, thereby digital signal after the sampling of this shunt circuit linearity insulating circuit has pinpoint accuracy to the low frequency part of input signal, can realize accurate voltage measurement function.If this buffer circuit uses at oscillograph front end, can realize the real isolation oscillograph with function of voltmeter.If increase a current source that can arrange at oscillograph input end, can also realize function of multimeter such as resistance measurement, break-make drive test amount, diode polarity measurement.
In the present embodiment, high-frequency transformer adopts former the limit winding of 1:1, signal is carried out to the isolation of 1:1.Certainly, select the transformer of other ratios, also do not affect creativeness of the present invention.Accordingly, only the gain of described control treatment circuit need be adjusted according to digital isolator with the gain in transformer, be made two paths of signals amplitude balance unanimously.
Insulation isolation voltage of the present invention, is determined by the winding conducting wire of digital isolator, transformer.
With several specific embodiments, the invention will be further described below:
Fig. 6 is the present embodiment structural drawing.The present embodiment is for realizing the linear isolation to single-ended signal input.
In the present embodiment, low-frequency amplifier circuit amplifier U1 selects low bandwidth high-precision amplifying, and the circuit form of low-frequency amplifier circuit can have 4 kinds of forms below:
As Fig. 7 (A), form 1, follow circuit, circuit bandwidth is determined by amplifier itself.
As Fig. 7 (B), form 2, low pass follow circuit, circuit bandwidth is determined by R1, C1 and amplifier band width.
As Fig. 7 (C), form 3, first RC low pass, then amplifier is followed, and circuit bandwidth has R, C and amplifier band width to determine.
As Fig. 7 (D), 4, one active step low-pass amplifiers of form, circuit bandwidth has R1, C1, R2, C2 and amplifier band width to determine.
Certainly circuit also can adopt the mode such as polystage amplifier or low-pass filter cascade, also can adopt everybody known other active low-pass filter circuit forms, does not affect creativeness of the present invention.
Amplifier U1 can select any high-precision amplifying, to meet the requirement to low-frequency sampling precision, certainly select precision, low noise, low distortion, Low-bias Current, these more excellent amplifiers of Low Drift Temperature, can be conducive to the realization to low frequency high precision technology effect.For example select AD823, the AD8639 etc. of ADI company.
The circuit form of high frequency subtraction amplification circuit is scale operation circuit, because low frequency path gain is 1, so R2=R3=R4=R5, the gain of high-frequency path is also 1.Suppose that signal is input as V
in, low-frequency amplifier circuit is output as V
lf, U2 output U
hf=V
in-V
lf.
Amplifier U2 in high frequency subtraction amplification circuit can select any high speed amplifier, as long as can meet maximum bandwidth and the maximum voltage amplitude of design needs.Certainly select larger bandwidth, low noise, low distortion amplifier, can be conducive to realize design bandwidth demand.Such as AD8038, the AD8012 etc. of ADI company.
Relation between input signal and low frequency signal, high-frequency signal is as follows, and on frequency domain, adding input signal frequency response is straight line, as Fig. 8 (A).
Low frequency path frequency response after low-frequency amplifier circuit is low-pass characteristic, and through subtraction circuit, the frequency response of high-frequency path presents high pass characteristic, and figure is as Fig. 8 (B).The frequency binding site of the low frequency in the present embodiment and high-frequency path may be between 10kHz ~ 100kHz.Certainly select different amplifiers, and in different bandwidth Design index situations, this interval may change.
From time-domain analysis, if input signal is input as square wave, the frequency content of square wave can cover said frequencies interval.The output of low frequency path and high-frequency path is as shown in Fig. 8 (C).
Sigma-delta ADC(in the present embodiment claims again Delta-Sigma modulation analog to digital converter) optimal case is the ADC that uses 24bit, can realize higher measuring accuracy.As the AD7763 of ADI company, be the sigma-delta ADC of 24bit, 625kHz sampling rate, 109dB dynamic range.AD7763 is output as SPI interface, needs 3 railway digital isolation to realize the isolation to sampled digital signal.
Sigma-delta ADC in the present embodiment and digital isolator suboptimal design are the analog to digital converter AD7401A that adopts the band isolation of ADI company.
It is 16 sigma-delta modulators of an isolation, can realize 5000Vrms, the isolating power of 1 minute duration.Input is converted to 1bit data stream at a high speed by it, then passes through inner transformer isolation, the clock MCLKIN of a 20MHz frequency of input, and as the sampling clock of modulator, output 1bit data MDAT.
Like this, only need a device, just realized the function of sigma-delta ADC and digital isolator, simple on circuit structure.
Certainly, use AD7401A, low frequency path signal need to be connected to its input end VIN+, the ground of measuring passage is connected on VIN-.
Transformer in the present embodiment, in order to realize large as far as possible bandwidth, the maximum operation frequency of transformer need to be greater than the bandwidth of design requirement, and the lowest operating frequency of transformer need to extend to and is less than 10kHz, lowest operating frequency is extended to and is less than 10kHz, in order that with the frequency of operation in low frequency path has certain overlappingly, low frequency and high-frequency path output are added ability reflected input signal like this.And withstand voltage between primary and secondary will meet design and expect.In the present embodiment, transformer winding mode has adopted line transformer mode, can realize good frequency response.Other forms of transformer is also passable, but frequency response response is slightly poor.
Magnetic core of transformer is most preferably used high permeability soft magnetic ferrite bead, as the R10K series of Beijing QiXing flying Electronics Co., Ltd, as R10K-H13x7x5.As the A10 series of Yue Feng electronic material incorporated company, as A10-T12x6x4.
Wire rod adopts three layer insulation wire, can realize very high withstand voltage, as the TEX-E three layer insulation wire of electronics industry Co., Ltd. of Furukawa Electronic, wire diameter Ф 0.20mm.As directly weldering type of the TIW-B three layer insulation wire along positron company limited, wire diameter Ф 0.20mm.
The line transformer of the present embodiment can be realized minimum 1kHz, the frequency of operation of the highest 200MHz, and in frequency band range, amplitude-frequency response fluctuation is very little.
In buffer circuit in the present embodiment, R6 is the pull-up resistor on transformer time limit, for regulating the amplitude-frequency response of transformer.Selected value is 1.2k Ω.Amplifier U3 selects Differential OPAMP, to adapt to the difference input requirements of the second analog to digital converter, selects the LMH6554 of TI company, input, feedback resistance R7=R8=R9=R10=300 Ω.
The second analog to digital converter in the present embodiment, the ADC that can select any satisfied design sampling rate to require.As select the ADC of 8 1Gsa/s of TI company, model ADC08D1000.As select the ADC of 8 1Gsa/s of E2V company, model AT84AD001B.
Embodiment 2
Fig. 9 is the present embodiment structural drawing.
The difference of the second embodiment and the first embodiment is that the driving of transformer T1 and reception all adopt differential mode.The amplifier of high frequency subtraction amplification circuit is selected fully-differential amplifier, and amplifier is output as differential signal, is connected to the two ends on the former limit of transformer T1, for driving transformer.Signal input and low frequency signal are connected to two input ends of differential amplifier circuit, form subtraction circuit.Resistance value R2=R3=R4=R5=300 Ω.
Buffer circuit connects as shown in Figure 9, and transformer load resistance R 6 is connected to the two ends on transformer time limit, is connected to the positive-negative input end of differential amplifier circuit.
Embodiment 3
Figure 10 is the present embodiment, the structural drawing of shunt circuit linearity insulating circuit.
The present embodiment provides a kind of shunt circuit linearity insulating circuit for differential signal input.Signal is input as differential signal, low-frequency amplifier circuit also adopts fully differential amplifying circuit, its bandwidth can be selected according to the requirement in low frequency path, also can increase extra low-pass filter circuit, guarantees that the bandwidth in low frequency path meets the signal input requirements of sigma-delta ADC.As the fully-differential amplifier AD8476 of ADI company.
Or use two single-ended amplifiers, and the P to differential input signal, N end carries out low frequency amplification respectively, and amplifier type selecting is with embodiment 1, as shown in figure 11.
High frequency subtraction amplification circuit and embodiment 2 differences are, fully-differential amplifier has formed scale operation circuit, and resistance is chosen R1, R2, R3, R4, R5, R6 equate, is 300 Ω.The output of U1 is exactly subtracting each other of input signal and low-frequency amplifier circuit output like this.
Figure 12 is the structured flowchart of existing oscilloscope analog front end.As shown in the figure, this oscillograph, comprising: decay switching module, input stage buffering and adding circuit, programmable amplifier, control processing module and D/A modular converter.Input signal is sent to control processing module through decay switching module, input stage buffering and adding circuit, programmable amplifier successively.Control processing module gain control signal is sent to this programmable amplifier.Control processing module and also offset signal is sent to input stage buffering and adding circuit through D/A modular converter.
Figure 13 is the oscilloscope architecture figure of the designed shunt circuit linearity insulating circuit of application the present invention.As shown in the figure, this oscillograph, on the basis of above-mentioned existing oscilloscope architecture, is connected in series the designed shunt circuit linearity insulating circuit of the present invention between described programmable amplifier and control processing module, to realize signal isolation object.Generally the control treatment circuit in shunt circuit linearity insulating circuit can be arranged in oscillographic control processing module, to simplify oscilloscope architecture.
, also between described control processing module and programmable amplifier, and control between processing module and D/A modular converter meanwhile, be serially connected with digital isolator, this digital isolator and above-mentioned shunt circuit linearity insulating circuit are in parallel.
In addition, if the output of described programmable amplifier is differential signal, between this programmable amplifier and shunt circuit linearity insulating circuit, is connected in series difference and turns single-end circuit, so that its differential signal is converted to single-ended signal, for shunt circuit linearity insulating circuit.
The shunt circuit linearity insulating circuit that the present invention is designed and oscillograph thereof, by input signal being divided into low frequency and high frequency two parts, different frequency part is isolated by different independent paths respectively, thereby realizes high bandwidth linear isolation.This circuit has can realize circuit linearity insulating circuit, and after isolation, signal and input signal are basically identical; Can realize the isolation of very large bandwidth signal, more than isolation bandwidth can reach 200MHz; Transformer winding is convenient; The frequency compensated circuit of linear optical coupling circuit is simple, and debugging is convenient; Carry out the compensation of linear optical coupling without increasing delay circuit at high-frequency circuit; Can utilize easily in isolation oscillograph front end, realize isolation oscillograph function; Digital signal after this oscillograph sampling has pinpoint accuracy to the low frequency part of input signal, can realize accurate voltage measurement function.If this buffer circuit uses at oscillograph front end, can realize the real isolation oscillograph with function of voltmeter.If increase a current source that can arrange at oscillograph input end, can also realize function of multimeter such as resistance measurement, break-make drive test amount, diode polarity measurement.Persons skilled in the art any not creative transformation of doing under this design philosophy, all should be considered as within protection scope of the present invention.
Claims (10)
1. a shunt circuit linearity insulating circuit, is characterized in that, comprising: low-frequency amplifier circuit, the first analog to digital converter, digital isolator, high frequency subtraction amplification circuit, transformer, the second analog to digital converter and control treatment circuit;
Input signal is inputted respectively the positive input terminal of described low-frequency amplifier circuit and high frequency subtraction amplification circuit;
Described low-frequency amplifier circuit, for input signal is carried out to filtering, the low frequency signal in output input signal; Described low frequency signal is inputted respectively the negative input end of described the first analog to digital converter and high frequency subtraction amplification circuit;
Described high frequency subtraction circuit, for the input signal of described input being deducted to the low frequency signal of described low-frequency amplifier circuit input, to export high-frequency signal;
Described the first analog to digital converter, is connected with described low-frequency amplifier circuit, for the low frequency signal of low-frequency amplifier circuit input is sampled, and by the low-frequency digital signal input digital isolator after sampling;
Described digital isolator, is connected with described the first analog to digital converter, for the low frequency signal of low-frequency amplifier circuit output is isolated, and the low-frequency digital signal of exporting after isolation is inputted to described control treatment circuit;
Described transformer, is connected with described high frequency subtraction circuit, for the high-frequency signal of high frequency subtraction circuit input is isolated, and the high-frequency signal of exporting after isolation is inputted to described the second analog to digital converter;
Described the second analog to digital converter, is connected with described transformer, for the high-frequency signal of exporting after transformer isolation is sampled, and by the high-frequency digital signal input control treatment circuit after sampling;
Described control treatment circuit, for the low-frequency digital signal after the high-frequency digital signal after described sampling and isolation is added, generates the rear output signal of isolation, and output.
2. shunt circuit linearity insulating circuit as claimed in claim 1, is characterized in that: also comprise buffer circuit, between described transformer and described the second analog to digital converter, the high-frequency signal of exporting afterwards for strengthening described isolation, to drive the second analog to digital converter.
3. shunt circuit linearity insulating circuit as claimed in claim 1, is characterized in that:
Described transformer adopting line transformer winding method; The armature winding of this transformer and secondary winding adopt twisted-pair feeder, parallel lines or coaxial cable.
4. shunt circuit linearity insulating circuit as claimed in claim 1, is characterized in that:
Described transformer is 1:1 transformer.
5. shunt circuit linearity insulating circuit as claimed in claim 1, is characterized in that: described control treatment circuit, comprising: interpolator and totalizer; Wherein,
Described interpolator, accesses the low-frequency digital signal after described isolation, for the low-frequency digital signal after the isolation of input is carried out to interpolation arithmetic, obtains low-frequency digital signal after interpolation;
Described totalizer, for low-frequency digital signal after the high-frequency digital signal after described sampling and interpolation is added, generates output signal after described isolation.
6. shunt circuit linearity insulating circuit as claimed in claim 1, is characterized in that: described control treatment circuit, comprising: timer, interpolator and totalizer; Wherein,
Described timer, accesses the high-frequency digital signal after described sampling, for the high-frequency digital signal after the sampling of input is carried out to time delay, obtains high-frequency digital signal after time delay;
Described interpolator, accesses the low-frequency digital signal after described isolation, for the low-frequency digital signal after the isolation of input is carried out to interpolation arithmetic, obtains low-frequency digital signal after interpolation;
Described totalizer, is connected with interpolator with described timer, for low-frequency digital signal after high-frequency digital signal and interpolation after described time delay is added, generates output signal after described isolation.
7. the shunt circuit linearity insulating circuit as described in claim 1,5 or 6, is characterized in that:
Described the first analog to digital converter adopts low speed analog to digital converter, and the second analog to digital converter adopts high-speed AD converter.
8. an oscillograph with shunt circuit linearity insulating circuit, comprising: decay switching module, input stage buffering and adding circuit, programmable amplifier, control processing module and D/A modular converter; Input signal is sent to control processing module through decay switching module, input stage buffering and adding circuit, programmable amplifier successively; Control processing module gain control signal is sent to this programmable amplifier; Control processing module and also offset signal is sent to input stage buffering and adding circuit through D/A modular converter; It is characterized in that:
Any one shunt circuit linearity insulating circuit be serially connected with claim 1 to 6 between described programmable amplifier and control processing module in, to realize signal isolation object;
Between described control processing module and programmable amplifier, and control between processing module and D/A modular converter, be also serially connected with digital isolator, this digital isolator is in parallel with described shunt circuit linearity insulating circuit.
9. the oscillograph with shunt circuit linearity insulating circuit as claimed in claim 8, is characterized in that: in the shunt circuit linearity insulating circuit being connected in series between described programmable amplifier and control processor, control treatment circuit and be arranged in described control processing module.
10. the oscillograph with shunt circuit linearity insulating circuit as claimed in claim 8, is characterized in that: described programmable amplifier is output as differential signal; Between this programmable amplifier and described shunt circuit linearity insulating circuit, be serially connected with difference and turn single-end circuit, so that described differential signal is converted to single-ended signal.
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| CN104931814A (en) * | 2015-05-23 | 2015-09-23 | 成都众孚理想科技有限公司 | Digital isolation type grid detector |
| CN107783009A (en) * | 2016-08-31 | 2018-03-09 | 通号（郑州）轨道交通科技有限公司 | A kind of communication system monitoring device of multi-internet integration |
| CN109932547A (en) * | 2017-12-15 | 2019-06-25 | 北京机电工程研究所 | Sampling system is isolated in multichannel |
| CN110269634A (en) * | 2019-06-20 | 2019-09-24 | 上海联影医疗科技有限公司 | Isolated converter, X-ray generate equipment and medical image system |
| CN111856152A (en) * | 2020-07-28 | 2020-10-30 | 哈尔滨工业大学 | Pulse signal sampling method and device |
| CN112033451A (en) * | 2020-08-03 | 2020-12-04 | 珠海格力电器股份有限公司 | Measuring device and method of encoder and encoder |
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| CN117590056A (en) * | 2024-01-15 | 2024-02-23 | 广州德肯电子股份有限公司 | Alternating current-direct current signal isolation detection circuit and detection device |
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| CN104811183A (en) * | 2015-05-21 | 2015-07-29 | 北京联合大学 | Electric signal sampling isolation circuit |
| CN104811183B (en) * | 2015-05-21 | 2018-02-02 | 北京联合大学 | A kind of electric signal sampling isolation circuit |
| CN104931814A (en) * | 2015-05-23 | 2015-09-23 | 成都众孚理想科技有限公司 | Digital isolation type grid detector |
| CN104931814B (en) * | 2015-05-23 | 2018-01-26 | 成都众孚理想科技有限公司 | A kind of isolated power network detector of numeral |
| CN107783009A (en) * | 2016-08-31 | 2018-03-09 | 通号（郑州）轨道交通科技有限公司 | A kind of communication system monitoring device of multi-internet integration |
| CN109932547A (en) * | 2017-12-15 | 2019-06-25 | 北京机电工程研究所 | Sampling system is isolated in multichannel |
| CN110269634A (en) * | 2019-06-20 | 2019-09-24 | 上海联影医疗科技有限公司 | Isolated converter, X-ray generate equipment and medical image system |
| CN110269634B (en) * | 2019-06-20 | 2023-09-12 | 上海联影医疗科技股份有限公司 | Isolation converter, X-ray generating device and medical imaging system |
| CN111856152A (en) * | 2020-07-28 | 2020-10-30 | 哈尔滨工业大学 | Pulse signal sampling method and device |
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| CN112511115B (en) * | 2021-02-02 | 2021-05-04 | 深圳市鼎阳科技股份有限公司 | Composite signal amplifying circuit and signal generator |
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