CN103884894B - A kind of improved shunt circuit linearity insulating circuit and its oscillograph - Google Patents
A kind of improved shunt circuit linearity insulating circuit and its oscillograph Download PDFInfo
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- CN103884894B CN103884894B CN201210560838.7A CN201210560838A CN103884894B CN 103884894 B CN103884894 B CN 103884894B CN 201210560838 A CN201210560838 A CN 201210560838A CN 103884894 B CN103884894 B CN 103884894B
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Abstract
The present invention provides a kind of improved shunt circuit linearity insulating circuits, including low-frequency amplifier circuit, linear optical coupling circuit, frequency compensated circuit, buffer circuit, transformer and add circuit.Low frequency component in input signal is subjected to linear isolation using linear optical coupling circuit, and increases compensating for frequency response circuit, compensation is recessed due to amplitude-frequency response caused by the delay of linear optical coupling.Input signal is connected to one end of transformer after buffer circuit, low frequency component is connected to the other end of primary coil, for the low frequency component in offset input signal, curent change in primary winding has reacted the high fdrequency component in input signal, high fdrequency component is carried out coupling isolation by transformer, low frequency signal and high-frequency signal after isolation are input to add circuit, carry out add operation, input signal has flat amplitude-frequency response, linear phase before output signal and isolation after isolation, that is, realizes linear isolation.
Description
Technical field
The present invention relates to electronic metering equipment, especially a kind of improved shunt circuit linearity insulating circuit and its oscillograph.
Background technology
The electric signal of input side can be transmitted to outlet side by isolation circuit, but electrically between input side and outlet side
It is isolation, or perhaps insulate, a smaller capacitance is only existed between input side and outlet side.Isolation circuit can carry
Common-mode rejection ratio when high measurement reduces interference, improves signal quality, can also insulation risks voltage, protection equipment and the person
Safety.Multichannel oscillograph simultaneously measure when, channel separation can also measure the signal of multiple and different common-mode voltages, prevent because
Interchannel causes short circuit accident altogether.
In terms of the frequency response of processed signal and isolation circuit, isolation circuit can be divided into digital isolation circuit and line
Property or analog isolation circuit.High and low level signal, i.e. digital signal can only be isolated in digital isolation circuit, belong to switching signal, skill
It is easy to implement in art.Circuit linearity insulating circuit is otherwise referred to as isolated amplifier, and output signal and input signal are linear,
Analog signal can be transmitted, the frequency response of circuit can be from DC to very high frequency.High bandwidth（Hundreds of MHz or more）It is linear
Isolation circuit is technically relatively difficult to achieve.And realize the circuit linearity insulating circuit with very high DC precision, it can be realized on oscillograph
Voltmeter or function of multimeter have good application value, but technically have higher difficulty.
Circuit linearity insulating circuit, there are commonly following methods：
Linear optical coupling isolation circuit, separation principle and the common optical coupler of linear optical coupling do not have difference, only by common optical coupler
Single-shot list receive pattern and slightly change, increase the light for feedback and receive circuit for feeding back.In this way, although two light connect
All it is nonlinear by circuit, but the nonlinear characteristic that two light receive circuit is the same.In this manner it is possible to pass through feedback
The non-linear of access offsets the non-linear of through path, to achieve the purpose that realize linear isolation.Linear optical coupling can be real
The existing very high linearity, can be isolated direct current signal, but signal bandwidth maximum can only arrive several MHz.
Transformer isolation circuit makes the electrical completely insulated of primary side and secondary side, makes circuit using electromagnetic induction principle
Isolation.Transformer according to the difference of core material and the difference of winding method may be implemented that very high frequency is isolated.
But direct current and low frequency signal cannot be isolated in the characteristics of due to electromagnetic induction, transformer, general transformer can be isolated
Minimum can arrive kHz ranks.
Isolated amplifier device, the isolated amplifier chip for having some integrated on the market at present, as ADI companies AD203,
AD215.Such devices use transformer is isolated, and input is carried out linear modulation into digital signal, then utilizes transformer
Digital signal is isolated, the signal after isolation generates the analog signal after isolation using demodulation.It is this kind of have it is higher
The linearity, but bandwidth is generally very low, maximum only hundreds of kHz at present.
To solve the disadvantage that above-mentioned device, the prior art also give a variety of solutions, below just to wherein several solutions
Certainly scheme is introduced：
A, the patent of Patent No. CN96101007.X provides a solution, realizes that block diagram is as shown in Figure 1.
It uses the amplifier of two different bandwidths, and input signal is divided into high-frequency path and low frequency path, low frequency path
It is isolated using linear optical coupling, high-frequency path is isolated using transformer.Transformer secondary side uses two windings, generates phase
Position opposite differential signal+Vout and-Vout.Low frequency signal after isolation passes through Gain tuning and single-ended transfer difference amplifier,
Biasing of the signal of output as transformer secondary side.Low frequency channel leads to the signal after superposition due to the delay of linear optical coupling,
High and low frequency junction amplitude-frequency response collapses, and is compensated using circuit 48,52,50,54, and amplitude-frequency response is made to be combined in high and low frequency
Place, promotion appropriate realize the flatness of amplitude-frequency response.
This patent can realize the circuit linearity insulating circuit of big bandwidth, but have the disadvantage that：
1, since transformer secondary side uses two windings, the positive and negative anodes as output difference signal, it is more difficult to ensure positive and negative
The same phase of pole increases the difficulty of transformer winding.
2, the delay of the isolation using linear optical coupling as low frequency path, low frequency path causes frequency response uneven, uses
Circuit 48,52,50,54 compensates, since capacitor element is discrete, it is more difficult to ensure that differential signal positive and negative anodes are completely the same.
3, it can be superimposed since transformer should meet low-limit frequency and low frequency path, meet highest frequency again as possible
Greatly, due to the limitation of transformer, the bandwidth that can be realized is little, and maximum can arrive 100MHz or so.
B, the patent of Patent No. US5834973 the shortcomings that without patent CN96101007.X, realizes block diagram such as Fig. 2
It is shown.
This patent uses the amplifier of two different bandwidths, low bandwidth amplifier to realize that low frequency path, low frequency path use
Linear optical coupling is isolated.The output of low bandwidth amplifier is connected to high bandwidth amplifier composition by 124,126 partial pressure
Input signal is subtracted the signal of low frequency path by subtraction circuit one end, subtraction circuit, and the high-frequency signal of output is connected to transformer
Primary side, the signal of the high-frequency signal and low frequency path is added as input signal.The linear optical coupling circuit of low frequency path has
Certain gain, to offset the attenuation of the low frequency signal of subtraction circuit input.High-frequency signal is isolated using transformer, is become
Depressor secondary side exports and add circuit is passed through in the output of linear optical coupling, generates the signal after isolation, to realize the line to signal
Sexual isolation.
The problem of this patent preferably resolves transformer winding, but have a disadvantage that：
1, the isolation using linear optical coupling as low frequency path, low frequency path have certain delay, direct and high frequency road strength
Output is added, and low-and high-frequency frequency junction amplitude-frequency response can be made to collapse, this patent does not introduce compensation circuit, the width of output signal
Unevenness is answered in frequency response.
2, it can be superimposed since transformer should meet low-limit frequency and low frequency path, meet highest frequency again as possible
Greatly.Due to the limitation of transformer, the bandwidth that can be realized is little, and maximum can arrive 200MHz or so.
C, the patent of Patent No. CN200610154738.9 has carried out the implementation method of patent US5834973 specifically
Refinement, and solve its disadvantage, provide delay compensating chain, realize that block diagram is as shown in Figure 3.
This patent is consistent with the realization approach of US5834973, but has carried out circuit refinement, increases the delay of low frequency path
Compensation circuit 102,103,104.Input signal passes through low-frequency amplifier circuit 100, and output is connected to subtraction circuit 101, and subtraction is defeated
Go out as high-frequency signal.High-frequency signal is isolated by transformer 26, and circuit 105 is signally attached to after isolation.Low frequency is believed
Number it is isolated by linear optical coupling circuit 102, after low frequency signal isolation, by delay compensating chain 103,104 into line delay
Compensation, and necessary amplification is carried out, keep the amplitude of low frequency path consistent with high-frequency path, after the output and high-frequency isolation after compensation
Signal pass through add circuit 105, synthesis isolation after signal, that is, realize the linear isolation to signal.
This patent circuit is more detailed, patent before capable of solving the disadvantage that, but also has the disadvantages that：
1, it can be superimposed since transformer should meet low-limit frequency and low frequency path, meet highest frequency again as possible
Greatly, due to the limitation of transformer, the bandwidth that can be realized is little, and maximum can arrive 200MHz or so.
2, the delay compensating chain 103 mentioned in patent or 22,24,29,30, can not actually solve low frequency and high frequency
Amplitude-frequency recess at the overlapping frequencies of path.Because capacitance 24,30 plays the role of low pass in shown amplifier circuit, only
It can allow the high frequency of low frequency path is opposite to become lower with low frequency, and cannot play the role of suitably promoting high frequency.Circuit 103, it is real
Border is also RC low pass circuits, can not equally play the role of suitably promoting high frequency.
3, since the delay compensating chain of offer does not work, the output amplitude-frequency response of circuit linearity insulating circuit is uneven.
4, low frequency path circuit is complicated.
In conclusion currently available technology major defect is that subtraction formula frequency dividing circuit is complicated, high frequency frequency response debugging is difficult,
And the frequency response depression problem brought due to linear optical coupling circuit can not be compensated.
Invention content
It is a primary object of the present invention to solve problems of the prior art, provide a kind of improved split-path linear every
From circuit and its oscillograph.
The purpose of the present invention is what is be achieved by following technical proposals：
A kind of improved shunt circuit linearity insulating circuit, which is characterized in that including：Low-frequency amplifier circuit, linear optical coupling circuit,
Transformer and add circuit；
The low-frequency amplifier circuit exports the low frequency signal in input signal for being filtered to input signal；
The linear optical coupling circuit, is connected with the low-frequency amplifier circuit, the low frequency for being inputted to low-frequency amplifier circuit
Signal is isolated, and the low frequency signal exported after isolation is inputted the add circuit；
Input signal is accessed in primary side winding one end of the transformer, and the other end accesses the low frequency of low-frequency amplifier circuit output
Signal forms the high-frequency signal in input signal；The transformer, for the high-frequency signal in input signal to be isolated,
And the high-frequency signal exported after isolation is inputted into the add circuit；
The add circuit, the low frequency signal for being exported after the isolation by input are added with high-frequency signal, generate isolation
Output signal afterwards, and export.
The front end that the primary side winding end of input signal is accessed in the transformer is also associated with buffer circuit；The buffering electricity
Road, for enhancing the input signal.
The output end of the linear optical coupling circuit is additionally provided with frequency compensated circuit；
The frequency compensated circuit, for increasing the high frequency in the low frequency signal exported after the linear optical coupling circuit isolation
Response.
The frequency compensated circuit is made of amplifier U3, resistance R4, R5, R6, R7, capacitance C2；
The positive input terminal of the low frequency signal input amplifier U3 exported after the linear optical coupling circuit isolation；
Resistance R4, R5 are serially connected between the output end and ground connection of amplifier U3；The tie point and amplifier U3 of resistance R4, R5
Negative input end connect；
R6, R7 are serially connected between the output end and ground connection of amplifier U3；
Capacitance C2 is connected between the tie point of described resistance R4, R5 and the tie point of described resistance R6, R7.
The transformer uses line transformer winding method；The armature winding and secondary windings of the transformer are using double
Twisted wire, parallel lines or coaxial line.
The gain of the add circuit is adjusted according to the gain in the linear optical coupling circuit and transformer.
The add circuit uses Full differential operational amplifier；Two leading-out terminals of the transformer secondary output winding, which are connected to, to be added
Two input terminals of the fully-differential amplifier of method circuit；One is added between the linear optical coupling circuit output end and add circuit
A single-ended transfer difference circuit；The single-ended transfer difference circuit, for making the single-end circuit signal of linear optical coupling circuit output be converted to
Difference channel signal.
A kind of oscillograph with improved shunt circuit linearity insulating circuit, including：Decay switching module, input stage buffering and
Add circuit, programmable amplifier, high-speed ADC, control process module and D/A conversion modules；Input signal is cut through decaying successively
Mold changing block, input stage buffering and add circuit, programmable amplifier, high-speed ADC are sent to control process module；Control process mould
Gain control signal is sent to the programmable amplifier by block；Control process module also sends out offset signal through D/A conversion modules
It send to input stage buffering and add circuit；It is characterized in that：
The improved branch of any one in claim 1 to 7 is serially connected between the programmable amplifier and high-speed ADC
Circuit linearity insulating circuit, to realize signal isolation purpose；
Between the control process module and programmable amplifier and control process module and D/A conversion modules it
Between, also it is serially connected with digital isolator.
The output of the programmable amplifier is differential signal；In the programmable amplifier and the improved split-path linear
Between isolation circuit, it is serially connected with differential-to-single-ended circuit, the differential signal is converted into single-ended signal.
Present invention has the advantages that：
1, the high fdrequency component in input signal is directly generated using transformer, carries out the isolation of high frequency channel, circuit is simple,
Without computing circuits such as subtracters.
2, circuit linearity insulating circuit can be realized, signal and input signal are almost the same after isolation.
3, it can realize that the isolation of big bandwidth signal, isolation bandwidth can reach 200MHz or more.
4, transformer uses line transformer mode, coiling convenient.
5, the frequency compensated circuit of linear optical coupling circuit is simple, and debugging is convenient.
6, without increasing the compensation that delay circuit carries out linear optical coupling in high-frequency circuit.
7, it can easily utilize in isolation oscillograph front end, realize isolation oscillograph function.
Description of the drawings
Attached drawing described herein is used to provide further understanding of the present invention, and is constituted part of this application, not
Constitute limitation of the invention.In the accompanying drawings：
Fig. 1 is existing one structure chart of isolation circuit example；
Fig. 2 is existing two structure chart of isolation circuit example；
Fig. 3 is existing three structure chart of isolation circuit example；
Fig. 4 is improved shunt circuit linearity insulating circuit structural schematic diagram；
Fig. 5（A）For input signal schematic diagram；
Fig. 5（B）For output signal schematic diagram；
Fig. 6 is that amplitude-frequency recess principle illustrates schematic diagram after signal frequency is superimposed；
Fig. 7 is frequency compensation process schematic；
Fig. 8 is improved 1 structural schematic diagram of shunt circuit linearity insulating circuit embodiment；
Fig. 9 is improved 2 structural schematic diagram of shunt circuit linearity insulating circuit embodiment；
Figure 10 is the structure diagram of existing oscilloscope analog front end；
Figure 11 is the oscilloscope architecture schematic diagram of the shunt circuit linearity insulating circuit of application enhancements.
Specific implementation mode
To make the objectives, technical solutions, and advantages of the present invention clearer, right with reference to embodiment and attached drawing
The present invention is described in further details.Here, the exemplary embodiment and its explanation of the present invention be for explaining the present invention, but simultaneously
It is not as a limitation of the invention.
For it is aforementioned the problems of in the prior art, the present invention by input signal by being connected to primary line
Low frequency component is connected to the other end of primary coil by one end of circle, for the low frequency component in offset input signal, transformer
Curent change in armature winding has reacted the high fdrequency component in input signal, and different frequency part passes through different independence respectively
Access is isolated, to realize high bandwidth linear isolation.Fig. 4 is the improved shunt circuit linearity insulating circuit structural representation of the present invention
Figure.As shown, the improved shunt circuit linearity insulating circuit, including：Low-frequency amplifier circuit, linear optical coupling circuit, transformer and
Add circuit.
The low-frequency amplifier circuit exports the low frequency signal in input signal for being filtered to input signal；
The linear optical coupling circuit, is connected with the low-frequency amplifier circuit, the low frequency for being inputted to low-frequency amplifier circuit
Signal is isolated, and the low frequency signal exported after isolation is inputted the add circuit；
Input signal is accessed in primary side winding one end of the transformer, and the other end accesses the low frequency of low-frequency amplifier circuit output
Signal；In this way, the low frequency signal in the input signal that input signal is exported with low-frequency amplifier circuit is cancelled out each other, i.e., in the primary side
Winding side forms the high-frequency signal in input signal；The transformer, for in input signal high-frequency signal carry out every
From, and the high-frequency signal exported after isolation is inputted into the add circuit；
The add circuit, the low frequency signal for being exported after the isolation by input are added with high-frequency signal, generate isolation
Output signal afterwards, and export.
In above-mentioned improved shunt circuit linearity insulating circuit, input signal is connected to low-frequency amplifier circuit, low-frequency amplifier tool
It is the direct current tremendously low frequency part of input signal, abbreviation low frequency signal to have the effect of low pass, the frequency content of output signal.It will input
Low frequency component in signal carries out linear isolation using linear optical coupling circuit.Input signal is connected to the one of transformer primary side winding
Low frequency component, is connected to the other end of primary side winding by end, for the low frequency component in offset input signal, primary around
Curent change in group has reacted the high fdrequency component in input signal, and high fdrequency component is carried out coupling isolation by transformer, after isolation
Low frequency signal and high-frequency signal be input to add circuit, carry out add operation, input before the output signal and isolation after isolation
Signal has flat amplitude-frequency response, linear phase, that is, realizes linear isolation.Due to low frequency, high-frequency signal point in the present invention
Independent isolating is not carried out, therefore very high isolation bandwidth may be implemented.Also, since transformer directly generates height in input signal
Frequency component signal does not lean on subtracter to generate high frequency signal without subtraction formula frequency dividing circuit in the prior art, significantly simple
Circuit is changed.Subtracter gain is also avoided simultaneously due to error caused by resistance precision, amplifier input biasing, bias current.
In addition, in order to enhance driving capability of the input signal to transformer.As shown in figure 4, the isolation circuit is in transformer
The front end for accessing the primary side winding end of input signal is also associated with buffer circuit.The buffer circuit, for enhancing the input
Signal.By the way that the buffer circuit is arranged, the driving capability of input signal is on the one hand enhanced, on the other hand input signal is played
The effect of buffering, alleviates the load of signal source.Certainly, if input signal driving capability is sufficiently strong, buffer circuit can be with
It omits, does not influence the patentability of the present invention.
In the present invention, relationship is illustrated in fig. 5 shown below between input signal, low frequency signal and high-frequency signal.Fig. 5（A）It is defeated
Enter signal schematic representation, it is assumed that input signal is ideal pulse, and it is A, the frequency response of infinite bandwidth to have amplitude.Fig. 5（B）It is defeated
Go out signal schematic representation.Wherein, low frequency signal in frequency domain representation as shown, f1 be low frequency signal cutoff frequency.High-frequency signal
As shown, f2 is the cutoff frequency of high-frequency signal.Both of which is directly added, and signal after being added is as input signal.
High-frequency signal is isolated by transformer, and transformer needs the bandwidth for having sufficiently large, and meets high-frequency signal
Cutoff frequency f2, i.e. the low cutoff frequency of transformer should be less than f2.Signal component near frequency f2 in this way, could substantially not
Decaying be isolated, and the high-frequency signal after isolation is added with low frequency signal could go back original input signal.
The highest frequency and low-limit frequency of transformer are contradiction, to have lower working frequency, it is necessary to which magnetic core has
There is the number of turns of the saturation flux of bigger, the volume of bigger or coil more；There is higher working frequency, it is necessary to magnetic
Core has higher magnetic permeability, smaller volume and less coil turn.So the passband of various transformers（Higher cutoff frequency
Subtract low cutoff frequency）It can not be made big, generally also with regard to hundreds of MHz.In circuit linearity insulating circuit, low cutoff frequency is wanted can be full
The bandwidth of sufficient linear optical coupling isolation circuit, generally several kHz to tens kHz, then the general energy of highest cutoff frequency of transformer
Enough accomplish that 200MHz, more high bandwidth are difficult to, amplitude-frequency response flatness can be caused to be deteriorated, amplitude-frequency response rises and falls.
High frequency transformation in the present invention is in order to realize bandwidth as big as possible, and its low cutoff frequency needs to meet linearly
The cutoff frequency of photoelectric coupled circuit, generally several kHz to tens kHz.So using line transformer winding method, may be implemented
Bandwidth as high as possible.
Armature winding and secondary windings by modes such as twisted-pair feeder, parallel lines, coaxial lines, are formed and are passed by line transformer
Defeated line, primary and secondary conducting wire are closely packed together, and the line capacitance of arbitrary point is all very big, and is to be uniformly distributed on entire line, due to
Conducting wire is wound on high permeability magnetic core, therefore inductance value of the conducting wire per segment is also very big, and is evenly distributed on entire line, therefore is passed
Defeated line can regard the coupled chain of numerous inductance, capacitance composition as, complete the transmission of energy, therefore line transformer line
Between capacitance do not influence the transmission of high-frequency energy not only, but the necessary condition of electromagnetic energy conversion, since electromagnetic wave is mainly
Propagation between conducting wire, the influence of the loss of magnetic core to signal transmission will greatly reduce, so line transformer
Maximum operating frequency can greatly improve, several GHz can be arrived.The soft magnetic property of high permeability, such as iron are selected in the present invention
Ferrite core.Higher isolation bandwidth may be implemented in transformer in the present invention, reaches 200MHz or more.
Magnetic core in the present invention can generally select round magnet ring, coiling simple and convenient.Certainly other shapes, such as Fang Huan need to be used
It can also.
In the present embodiment, transformer is all made of 1:1 former secondary side winding carries out 1 to signal:1 isolation.Certainly, it selects
With the transformer of other ratios, the creativeness of the present invention is nor affected on.Correspondingly, only need to by the gain of the add circuit according to
Gain in linear optical coupling circuit and transformer is adjusted, and keeps the two signal amplitude balance consistent.
The load resistance of transformer output is R8, by the circuit conversion in secondary winding at voltage.Output voltage is connected to
The input terminal of add circuit.
As shown, the linear optical coupling circuit includes operational amplifier U1, resistance R1, resistance R2, capacitance C1, linear light
Coupling, operational amplifier U2 and resistance R3.There are one light emitting diode and two two poles of matched photoelectricity for linear optical coupling enclosed inside
Pipe, one is used to feed back, and one is used for isolation coupling signal.Linear optical coupling preferably select Avago companies HCNR200 or
HCNR201.Amplifier U1 completes the driving of light emitting diode and feeds back the detection of photodiode.Amplifier U2 constitutes electricity
Voltage change circuit is flowed, the current signal of photodiode-couple is converted into voltage output by R3.R2 is as hair in circuit
The current-limiting resistance of optical diode.Resistance R1, R3 determine that the gain of linear optical coupling circuit, R3/R1 are equal to gain, and C1 capacitances are used for
Improve circuit stability, while playing certain low-pass effect.Reference power source-Vref ,+Vref are for making linear optical coupling circuit
Input and output biasing it is the same, input the voltage of 0V, output is also 0V.
Linear optical coupling circuit has certain delay, while C1 also has certain low-pass effect, and linear optical coupling is caused to export
When being superimposed with high frequency signal, in the amplitude-frequency recess that the place that low frequency signal and IF signal frequency are superimposed occurs.Such as Fig. 6 institutes
Show, input signal is square-wave signal, and output signal is divided into low frequency signal and high-frequency signal.If low frequency signal is not delayed, directly
It is consistent with input waveform to connect waveform after being added.But if low frequency signal has delay t, direct signal after being added such as figure below,
Occur recess behind square wave edge, be embodied in frequency domain, is exactly that the frequency of high-frequency signal and low frequency signal is folded the amplitude-frequency at place and reduces
, this frequency is near the cutoff frequency in low frequency signal.Same capacitance C1 has low frequency signal certain low-pass effect,
Also the high fdrequency component amplitude-frequency in low frequency signal can be made to be lower, amplitude-frequency recess equally occur.
According to the above problem, as shown in figure 4, the present invention is additionally provided with frequency compensation in the output end of the linear optical coupling circuit
Circuit.The linear optical coupling circuit, for increasing the high frequency sound in the low frequency signal exported after the linear optical coupling circuit isolation
It answers.
Specifically, the frequency compensated circuit is made of amplifier U3, resistance R4, R5, R6, R7, capacitance C2.The line
Property photoelectric coupled circuit isolation after the positive input terminal of low frequency signal input amplifier U3 that exports.Resistance R4, R5 are serially connected with amplifier U3
Output end and ground connection between.The tie point of resistance R4, R5 connect with the negative input end of amplifier U3.R6, R7 are serially connected with amplification
Between the output end and ground connection of device U3.Capacitance C2 is connected to the connection of the tie point and described resistance R6, R7 of described resistance R4, R5
Between point.
In the frequency compensated circuit, R4, R5 constitute amplifier gain, and gain is equal to R5/R4, which is multiplied by linear light
The gain of coupling circuit is equal to the overall gain of low frequency channel, needs to be equal to 1, makes low frequency signal 1:1 isolation, is realized and medium-high frequency is logical
The addition of signal after the isolation of road.If gain is not equal to 1, the isolation gain of corresponding medium-high frequency access is also required to be not equal to 1, needs
It is equal with low frequency channel overall gain.For adjusting frequency response, the product of wherein C2, R4 determine compensation by R6, R7 and C2
Frequency point, if R6/R7 is equal to R5/R4, the high fdrequency component of frequency compensated circuit output signal does not increase, does not also reduce；Such as
Fruit R6/R7 is more than R5/R4, then the high fdrequency component of output signal increases.The frequency compensated circuit can prolong linear optical coupling circuit
When and lower passband come frequency be recessed into capable compensation.
The frequency compensation process is as shown in Figure 7.The low frequency signal medium-high frequency portion exported after frequency compensated circuit increase isolation
The frequency response divided is substantially to reduce above-mentioned recess, the recess of the signal after superposition is made to can't see or be submerged in noise substantially.
Because after signal delay, no matter how low frequency signal is lifted high fdrequency component, and in t moment, low frequency signal is minimum level always,
So after superposition or can there are one very little recess.But since the delay of photoelectric coupled circuit is very small, thus this recess when
Between be very small, can ignore substantially.So the amplitude-frequency response depression problem that the present invention can solve delay and lower passband comes.
The signal of low frequency channel is after frequency compensated circuit and transformer output signal is connected to add circuit input
End, is added, and output signal and input signal after being added have flat amplitude-frequency response, linear phase, i.e. output signal
Input signal can be reacted, that is, realizes linear isolation.
The present invention's is dielectrically separated from voltage, is determined by the winding conducting wire of linear optical coupling, transformer, 5000Vrms may be implemented
Isolation strength.
With several specific embodiments, the invention will be further described below：
Embodiment 1
Fig. 8 is the present embodiment structural schematic diagram.The present embodiment is inputted suitable for single-ended signal, and single-ended signal output is answered
With.
In the present embodiment, low-frequency amplifier circuit follows circuit using R, C low-pass filtering and amplifier.Resistance and capacitance are determined
The bandwidth for having determined low-frequency amplifier circuit, needs the bandwidth for meeting linear optical coupling circuit, and selection resistance is 10k Ω, capacitance 1.5nF,
The bandwidth of low-frequency amplifier circuit is 10kHz.Amplifier can select any high-precision amplifying, to meet to low-frequency sampling precision
Requirement, select these more preferably amplifiers of precision, low noise, low distortion, Low-bias Current, Low Drift Temperature certainly, can be advantageous
In the realization to low frequency high precision technology effect.Such as select AD823, AD8639 etc. of ADI companies.
Linear optical coupling circuit, frequency compensated circuit amplifier can select amplifier identical with low-frequency amplifier circuit.
The resistance capacitance value of linear optical coupling circuit is that R2 takes 150 Ω, is used for current limliting.R1 takes 10k Ω, R3 to take 5k Ω, line
Property photoelectric coupled circuit gain be 0.5, C1 recommend 3pF.
The gain of frequency compensated circuit is 2, takes R4=R5=1k Ω, is recessed according to frequency caused by practical optocoupler, and selection is closed
Suitable capacitance, in the present embodiment, C2=100pF.The ratio of R6, R7 are used to adjust the degree of frequency recess, adjust suitable value,
Recess is set to disappear substantially.In the present embodiment, R6=1.5k Ω, R7=1k.
High frequency buffer circuit selects high speed operation amplifier, current embodiment require that realizing the isolation electricity of at least 200MHz bandwidth
Road.Amplifier composition follows circuit, gain 1.High speed amplifier can select AD8038, AD8000 of ADI companies, AD8001,
AD8009 etc..
Add circuit can select operational amplifier identical with buffer circuit, composition add circuit, circuit gain
It is 1, wherein 4 resistance are equal.
Transformer in the present embodiment, in order to realize the bandwidth of 200MHz, and its lowest operating frequency needs are low as possible,
It at least extends to and is less than 10kHz.And the pressure resistance between primary and secondary will meet design and it is expected.Transformer winding mode in the present embodiment
Line transformer mode is used, preferable frequency response may be implemented.The transformer of other forms can be with, but frequency response
It responds slightly worse.
The magnetic optimal selection high permeability soft magnetic ferrite bead of transformer, such as Beijing QiXing flying Electronics Co., Ltd
R10K series, such as R10K-H13x7x5, diameter 13mm, internal diameter 7mm.A10 such as Yue Feng electronic materials limited liability company is serial,
Such as A10-T12x6x4, diameter 12mm, internal diameter 6mm.
Wire rod uses three layer insulation wire, very high pressure resistance may be implemented, such as electronics industry Co., Ltd. of Furukawa Electronic
TEX-E three layer insulation wires, line footpath Ф 0.20mm.Such as the TIW-B directly weldering type three layer insulation wires along positive electron Co., Ltd, line footpath Ф
0.20mm。
Winding method is primary and secondary conducting wire, twists into twisted-pair feeder every 5mm, is wound on magnet ring, 15 circle of coiling.
Minimum 1kHz, the working frequency of highest 200MHz, frequency range may be implemented in the line transformer of the present embodiment
Interior amplitude-frequency response fluctuates very little.
The dielectric strength of transformer is determined by the insulation between primary and secondary winding conducting wire, multilayer can be selected exhausted in the present embodiment
Edge line, such as 3 layers of insulated wire, may be implemented the voltage device isolation of 5000V or more.
The circuit linearity insulating circuit that band is wider than 5200MHz may be implemented in the present embodiment, and the voltage with 5000V or more is isolated
Degree.
Embodiment 2
Fig. 9 is the present embodiment structural schematic diagram.The present embodiment is inputted suitable for single-ended signal, and differential signal output is answered
With.
The difference of the present embodiment and embodiment 1 is that add circuit uses Full differential operational amplifier, difference output.Composition ratio
Example add circuit, two leading-out terminals of transformer secondary output winding are connected to two input terminals of difference add circuit, add circuit
6 resistance to select identical resistance, add circuit gain be 1.Full differential operational amplifier can select ADI companies
LMH6552, LMH6554 of ADA4927 TI companies.
Former low frequency channel remains as single-end circuit.It need to only increase between the linear optical coupling circuit output end and add circuit
If a single-ended transfer difference circuit.The single-ended transfer difference circuit, using Full differential operational amplifier, so that single-end circuit signal turns
It is changed to difference channel signal, inputs add circuit.Specifically, the fully-differential amplifier for meeting low frequency channel bandwidth can be selected,
Such as AD8476, AD8275 of ADI companies.
The isolation circuit that the present embodiment is provided is differential signal by the isolation signals of add circuit final output.
The present invention provides improved shunt circuit linearity insulating circuit, can be applied to the measuring apparatus such as oscillograph.Figure 10 is existing
The structure diagram of oscilloscope analog front end.As shown, the oscillograph, including：Decay switching module, input stage buffering and addition
Circuit, programmable amplifier, high-speed ADC, control process module and D/A conversion modules.Input signal switches mould through decaying successively
Block, input stage buffering and add circuit, programmable amplifier, high-speed ADC are sent to control process module.Control process module will
Gain control signal is sent to the programmable amplifier.Offset signal is also sent to by control process module through D/A conversion modules
Input stage buffers and add circuit.
Figure 11 is the oscilloscope architecture schematic diagram using improved shunt circuit linearity insulating circuit designed by the present invention.As schemed
Show, which concatenates this on the basis of above-mentioned existing oscilloscope architecture between the programmable amplifier and high-speed ADC
The designed improved shunt circuit linearity insulating circuit of invention, to realize signal isolation purpose.Meanwhile also in the control process mould
Between block and programmable amplifier and between control process module and D/A conversion modules, it is serially connected with digital isolator.The number
Word isolator is the prior art, is mainly used for isolating digital signal.Digital isolator generally has photoelectric coupling mode, magnetic coupling side
Formula and capacitive coupling etc..Such as the photoisolator of Avgao companies, the iCoupler series magnetic coupling modes of ADI companies
Digital isolator, the capacitance digital isolator of TI companies.
In addition, if the output of the programmable amplifier is differential signal, in the programmable amplifier and shunt lead
Differential-to-single-ended circuit is concatenated between sexual isolation circuit, its differential signal is converted into single-ended signal, is isolated for split-path linear
Circuit uses.
Improved shunt circuit linearity insulating circuit designed by the present invention and its oscillograph, by the way that input signal is connected to change
Low frequency component is connected to the other end of primary coil by one end of depressor primary coil, for the low frequency in offset input signal
Component, the curent change in primary winding have reacted the high fdrequency component in input signal, and different frequency part leads to respectively
It crosses different independent paths to be isolated, to realize high bandwidth linear isolation.Also, since transformer directly generates input letter
Number high frequency components signal does not lean on subtracter to generate high frequency signal without subtraction formula frequency dividing circuit in the prior art,
Enormously simplify circuit.Subtracter gain is also avoided simultaneously due to being missed caused by resistance precision, amplifier input biasing, bias current
Difference.And the new frequency compensated circuit of the embodiment of the present invention can solve the prior art and can not achieve linear optical coupling compensation of delay
The shortcomings that.Persons skilled in the art do any transformation for not having creativeness under this design philosophy, are regarded as
Within protection scope of the present invention.
Claims (9)
1. a kind of improved shunt circuit linearity insulating circuit, which is characterized in that including：Low-frequency amplifier circuit, becomes linear optical coupling circuit
Depressor and add circuit；
The low-frequency amplifier circuit exports the low frequency signal in input signal for being filtered to input signal；
The linear optical coupling circuit, is connected with the low-frequency amplifier circuit, the low frequency signal for being inputted to low-frequency amplifier circuit
It is isolated, and the low frequency signal exported after isolation is inputted into the add circuit；
Input signal is accessed in primary side winding one end of the transformer, and the other end accesses the low frequency letter of low-frequency amplifier circuit output
Number, form the high-frequency signal in input signal；The transformer, for the high-frequency signal in input signal to be isolated, and
The high-frequency signal exported after isolation is inputted into the add circuit；
The add circuit, for believing the low frequency signal exported after the isolation of input and the high frequency exported after the isolation
It number is added, generates output signal after isolation, and export.
2. improved shunt circuit linearity insulating circuit as described in claim 1, it is characterised in that：It accesses and inputs in the transformer
The front end at the primary side winding end of signal is also associated with buffer circuit；The buffer circuit, for enhancing the input signal.
3. improved shunt circuit linearity insulating circuit as described in claim 1, it is characterised in that：The linear optical coupling circuit it is defeated
Outlet is additionally provided with frequency compensated circuit；
The frequency compensated circuit, for increasing the high frequency sound in the low frequency signal exported after the linear optical coupling circuit isolation
It answers.
4. improved shunt circuit linearity insulating circuit as claimed in claim 3, it is characterised in that：The frequency compensated circuit is by putting
Big device U3, resistance R4, R5, R6, R7, capacitance C2 are constituted；
The positive input terminal of the low frequency signal input amplifier U3 exported after the linear optical coupling circuit isolation；
Resistance R4, R5 are serially connected between the output end and ground connection of amplifier U3；The tie point of resistance R4, R5 are negative with amplifier U3's
Input terminal connects；
R6, R7 are serially connected between the output end and ground connection of amplifier U3；
Capacitance C2 is connected between the tie point of described resistance R4, R5 and the tie point of described resistance R6, R7.
5. improved shunt circuit linearity insulating circuit as described in claim 1, it is characterised in that：
The transformer uses line transformer winding method；The armature winding and secondary windings of the transformer use multiple twin
Line, parallel lines or coaxial line.
6. improved shunt circuit linearity insulating circuit as described in claim 1, it is characterised in that：The gain root of the add circuit
It is adjusted according to the gain in the linear optical coupling circuit and transformer.
7. improved shunt circuit linearity insulating circuit as described in claim 1, it is characterised in that：The add circuit is using complete poor
Divide operational amplifier；Two of the fully-differential amplifier that two leading-out terminals of the transformer secondary output winding are connected to add circuit are defeated
Enter end；A single-ended transfer difference circuit is added between the linear optical coupling circuit output end and add circuit；The single-ended slip
Parallel circuit, for making the single-end circuit signal of linear optical coupling circuit output be converted to difference channel signal.
8. a kind of oscillograph with improved shunt circuit linearity insulating circuit, including：Decay switching module, input stage buffer and add
Method circuit, programmable amplifier, high-speed ADC, control process module and D/A conversion modules；Input signal switches through decaying successively
Module, input stage buffering and add circuit, programmable amplifier, high-speed ADC are sent to control process module；Control process module
Gain control signal is sent to the programmable amplifier；Control process module also sends offset signal through D/A conversion modules
To input stage buffering and add circuit；It is characterized in that：
The improved split-path linear of any one in claim 1 to 7 is serially connected between the programmable amplifier and high-speed ADC
Isolation circuit, to realize signal isolation purpose；
Between the control process module and programmable amplifier and between control process module and D/A conversion modules, also
It is serially connected with digital isolator.
9. the oscillograph with improved shunt circuit linearity insulating circuit as claimed in claim 8, it is characterised in that：It is described to compile
The output of journey amplifier is differential signal；Between the programmable amplifier and the improved shunt circuit linearity insulating circuit, string
It is connected to differential-to-single-ended circuit, the differential signal is converted into single-ended signal.
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| 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 |
| CN106896251B (en) * | 2015-12-17 | 2019-06-04 | 北京航天测控技术有限公司 | A kind of automatic correcting method of oscillograph inband flatness |
| CN106656063A (en) * | 2017-01-12 | 2017-05-10 | 中国电子科技集团公司第四十四研究所 | Method for achieving linear isolated transmission of bipolar analog signals |
| CN107395191A (en) * | 2017-06-16 | 2017-11-24 | 薄焕林 | Passive linear optical coupling isolator |
| CN111257612B (en) * | 2020-01-17 | 2022-02-25 | 南京瑞控电气有限公司 | Isolation circuit for realizing linear pulse electric quantity based on electromagnetic sensor |
| CN113466654A (en) * | 2021-06-01 | 2021-10-01 | 中国电子科技集团公司第四十三研究所 | Method for detecting isolation voltage of linear optical isolation amplifier |
| CN117310247B (en) * | 2023-11-30 | 2024-03-01 | 深圳市鼎阳科技股份有限公司 | Oscilloscope and power supply probe frequency response compensation method thereof |
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