CN103353544B - Shunt circuit linearity insulating circuit apparatus - Google Patents
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- CN103353544B CN103353544B CN201210196730.4A CN201210196730A CN103353544B CN 103353544 B CN103353544 B CN 103353544B CN 201210196730 A CN201210196730 A CN 201210196730A CN 103353544 B CN103353544 B CN 103353544B
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Abstract
The present invention relates to a kind of electronic metering equipment.Shunt circuit linearity insulating circuit apparatus, comprise the high road signal path be made up of single order Hi-pass filter and transformer isolation circuit, also comprise the low path signal path be made up of low-pass first order filter and optical coupling isolation circuit, high road signal path and low path signal path are in input end parallel connection, and the output terminal of high road signal path and the output terminal of low path signal path are connected on summing circuit.The invention provides a kind ofly to have accurately and corresponding reliably in very wide signal measurement frequency range, and amplitude response drifts about little shunt circuit linearity insulating circuit apparatus; Solve in prior art and cannot be able to not realize in wideband circuit, signals revivification effect is undesirable, the technical matters of poor stability.
Description
Technical field
The present invention relates to a kind of electronic metering equipment, particularly relate to and a kind ofly in very wide frequency range, the linear buffer circuit along separate routes of electric signal measurement can be carried out isolator.
Background technology
Buffer circuit can by the electrical signal transfer of input side to outgoing side, but be isolation between input side and outgoing side on electrically, or perhaps insulation, the electric capacity that between input side and outgoing side, only existence one is less.
Buffer circuit can improve common-mode rejection ratio during measurement, reduces interference, improves signal quality, also can completely cut off dangerous voltage, proterctive equipment and personal safety.When hyperchannel is measured simultaneously, buffer circuit can also prevent the short circuit accident because interchannel causes altogether.
From processed signal, buffer circuit can be divided into digital buffer circuit and linear or analog isolation circuit.Numeral buffer circuit only processes high and low level signal, and normally 0V and 5V signal, belongs to switching signal, technically easily realizes.Circuit linearity insulating circuit is commonly referred to isolated amplifier, and its output signal is linear with input signal, can transfer die analog signal.The circuit linearity insulating circuit technically more difficult realization of high bandwidth (more than number megahertz).
Because numeral isolation easily realizes, analog input signal first can be carried out analog/digital conversion, become digital signal, then numeral isolation is carried out, D/A switch again, obtains analog output signal, so more easily realizes stable high linearity and the analog signal isolating of high bandwidth.But this technical scheme circuit is complicated, and cost is higher.Although input signal and output signal are all simulating signals, this method is numeral isolation in essence.
From the medium of signal transmission, the method for common isolation transmission of signal has by magnetic field, electric field, these three kinds of methods of light transmission of signal.
Transformer with the typical element of magnetic field transmission of signal.To the isolation of AC signal, directly transformer can be used.But transformer can not transmit direct current signal, the signal very low to frequency, excitatory reactance becomes very little, and transmission effect is also bad.Transmit direct current and low frequency signal with transformer, at input end, input signal must be modulated into an AC signal, transmit this signal with transformer, in output terminal demodulation, obtain an output signal linear with input signal.Typical circuit has the AD215 series isolated amplifier of Analog Devices, and isolation voltage ranges up to 2500Vrms, and nonlinearity can reach 0.005%, and signal band width ranges up to DC-120kHz.After adding modulation and demodulation link, frequency band is not easy to do height.
Electric capacity with the typical element of electric field transmission of signal.Electric capacity also can only transmit AC signal, cannot transmit direct current signal, the AC signal lower to frequency, and capacitive reactance becomes very large, is also unfavorable for transmitting.Want electricity container to transmit direct current and low frequency signal, at input end, input signal must be modulated into an AC signal, electricity container transmits this signal, in output terminal demodulation, obtains an output signal linear with input signal.In order to the isolation effect had, capacitance should be very low, usually below several pico farad.Typical circuit has the ISO124 series of Texas Instruments company, and isolation voltage ranges up to 1500Vrms, and nonlinearity can reach 0.01%, and signal band width ranges up to DC-50kHz.After adding modulation and demodulation link, frequency band is not easy to do height yet.
Using up the typical element transmitting electric signal is photoelectrical coupler (optocoupler).Different from above-mentioned two kinds of methods, can directly transmit direct current and low frequency signal with optocoupler, not need to be modulated into AC signal.Early stage optocoupler is mainly isolation digital circuit designs, in order to isolation mode analog signal, needs to add the peripheral circuits such as operational amplifier, makes the LED in optocoupler and photoelectric tube be operated in linear condition.This kind of buffer circuit is structurally divided into non-feedback-type and feedback-type two kinds.Non-feedback-type usually adds an optocoupler by two operational amplifiers and forms, and the linearity is poor.Feedback-type usually adds two optocoupler by two operational amplifiers and forms, and wherein an optocoupler is used as feedback compensation, and the linearity increases.Occurred the linear optical coupling that linear isolation is special afterwards, its structure is integrated in by LED and two photodiode in an encapsulation, and wherein a photodiode is used for feedback compensation, and another photodiode is used for transmission of signal to outgoing side.Typical linear optical coupling has the LOC110 series of CLARE company, and the IL300 series of VISHAY, the nonlinearity of these two kinds of optocouplers can reach 0.01%, and bandwidth can reach DC-200kHz.The HCNR200/201 linear optical coupling of Agilent company has expanded bandwidth, can reach DC-1MHz.
Also document is had to introduce the circuit linearity insulating circuit of DC-4MHz bandwidth.
From above-mentioned introduction, the most multipotency of ready-made circuit linearity insulating circuit is operated in the frequency band of DC to number MHz.For more high bandwidth (as DC to tens of million or hundreds of megahertz) signal, foregoing circuit cannot realize linear isolation transmission.
Notice that foregoing circuit can realize the linear isolation from direct current to the signal of hundreds of KHz preferably, and directly can realize the linear isolation from low frequency (few kilohertz) to the AC signal of high frequency (tens of million or hundreds of megahertz) with transformer or electric capacity, if both can be combined, the linear isolation from direct current to hundreds of megahertz bandwidth just can be realized.So-called shunt that Here it is (or two-way) circuit linearity insulating circuit.It is made up of direct current tremendously low frequency passage (abbreviation low path) and low frequency tremendously high frequency passage (being called for short Gao Lu).
There are two difficult points in this method.
First difficult point signal decomposition is become low path and Gao Lu two parts.Use the frequency divider of the Hi-pass filter composition of more than the low-pass filter of more than second order or second order and second order or second order that input signal is resolved into low path and Gao Lu traditionally.But original input signal can not be gone back faithfully after the output signal of two wave filters being added, near the overlapping frequencies of high-pass and low-pass filter, there is salient point or concave point in amplitude-frequency response, and the phase-frequency response of whole circuit is not linear, therefore output signal square-wave response poor, broadband signal can not be used for and measure.For this reason, need to add complicated compensation and regulating circuit, improve circuit amplitude-frequency response and phase-frequency response.Broadband isolation circuit cost is high, debugging is complicated, poor stability to which results in this kind.Typical products is as Tektronix company early production A6902B.
Second difficult point is that the time delay of low path channel isolation and Gao Lu channel isolation is inconsistent.High paths is by transformer isolation, and process the signal of the paramount frequency range of low frequency, time delay is little; Low paths is by Phototube Coupling, and the signal of process direct current tremendously low frequency section, postpones long.Even if first difficult point does not exist, the inconsistent output signal of synthesizing that still can cause of the time delay of low path and Gao Lu can not go back original input signal, and its phenomenon is that near square-wave response forward position, top is recessed.For this reason, delay circuit need be added at Gao Lu, as described in paper " design of a wide-band isolated amplifier of dual path " literary composition of " electrical measurement and instrument " magazine the 6th phase in 2004.Delay circuit also makes that circuit cost improves, bad stability, and there is the spinoffs such as the uneven and phase-frequency response of amplitude-frequency response is non-linear.
For overcoming above-mentioned difficult point, patent ZL 96101007.X proposes a kind of in direct current tremendously low frequency section, utilizes the output signal of photoelectric isolating circuit to carry out the wideband double-path circuit linearity insulating circuit of magnetic flux zeroing to transformer.But the transformer in the method is more complicated, and, when low path and the non-matched well of high road signal amplitude, in magnetic core of transformer, may direct current flux be there is, magnetic core can be caused saturated or magnetize.Patent CN200610154738.9 adopts subtraction formula frequency divider to realize along separate routes, makes can also keep smooth amplitude-frequency response and linear phase response with signal after isolation, but its subtraction formula frequency divider is comparatively complicated.
Summary of the invention
The invention provides a kind ofly to have accurately and corresponding reliably in very wide signal measurement frequency range, and amplitude response drifts about little shunt circuit linearity insulating circuit apparatus; Solve in prior art and cannot be able to not realize in wideband circuit, signals revivification effect is undesirable, the technical matters of poor stability.
The present invention also provides a kind of shunt isolated amplifier of simplification simultaneously, it can maintain stable frequency and impulse response, only need simple frequency response compensation adjustment, without the need to adding delay circuit at Gao Lu, also without the need to carrying out the shunt circuit linearity insulating circuit of magnetic flux zeroing to transformer in direct current tremendously low frequency section; Solve the technical matters of the circuit structure complicacy existed in prior art.
Above-mentioned technical matters of the present invention is solved by following technical proposals: shunt circuit linearity insulating circuit apparatus, it is characterized in that: comprise the high road signal path be made up of single order Hi-pass filter and transformer isolation circuit, also comprise the low path signal path be made up of low-pass first order filter and optical coupling isolation circuit, high road signal path and low path signal path are in input end parallel connection, and the output terminal of high road signal path and the output terminal of low path signal path are connected on summing circuit; Single order Hi-pass filter is identical with the cutoff frequency of low-pass first order filter, and input signal after frequency division and the isolation of too high road signal path and low path signal path, then exports summing signal through summing circuit and is reduced into input signal.
High road signal path, can be connected to input end or the output terminal of transformer isolation circuit by single order Hi-pass filter; Low path signal path, can be connected to input end or the output terminal of optical coupling isolation circuit by low-pass first order filter.
-3dB the cut off of single order Hi-pass filter is identical or almost identical with the-3dB cut off of low-pass first order filter.
Adopt single order Hi-pass filter and low-pass first order filter to realize frequency division, obtain high road signal and low path signal, single order Hi-pass filter is identical or almost identical with the-3dB cutoff frequency of low-pass first order filter.The frequency divider that the single order Hi-pass filter identical by-3dB cutoff frequency and low-pass first order filter are formed, wideband input signal is separated into Gao Lu and low path two parts, if again this two paths of signals is sued for peace, gained with signal compared with input signal, there is no the change of amplitude and phase place, input signal can be reappeared without distortion.This fraction frequency device is simple, and element is minimum, stable performance.
After Gao Lu and low path signal are respectively through transformer and light-coupled isolation, if transformer and optical coupling isolation circuit have enough linearities, signal sum then after isolation still can reappear input signal well, there is smooth amplitude response and linear phase response, there is accurate impulse response and step response.
Single order Hi-pass filter and low-pass first order filter achieve to input signal from DC the frequency division to the signal of hundreds of megahertz be connected with the effective of buffer circuit because have employed the frequency dividing circuit of single order, achieve linear isolation transmission and effective reduction of signal.
As preferably, described single order Hi-pass filter is connected to the input end of transformer isolation circuit, and low-pass first order filter is connected to the output terminal of optical coupling isolation circuit.The input end that single order Hi-pass filter is connected to transformer isolation circuit has every straight effect.Optical coupling isolation circuit includes faint light Current amplifier, easy introducing noise and interference, low-pass filter is contained in optical coupling isolation circuit output terminal, can filtering or reduce optical coupling isolation circuit introduce noise and interference, improve quality of output signals, therefore low-pass first order filter is connected to the output terminal of optical coupling isolation circuit.
As preferably, described single order Hi-pass filter is by electric capacity C
1with resistance R
1form, input signal is connected to single order Hi-pass filter, the output of single order Hi-pass filter connects the in-phase input end of the first operational amplifier, the output of the first operational amplifier is connected with one end of the armature winding of the transformer in transformer isolation circuit, another termination input end of the armature winding of transformer is with reference to ground, the output signal of one end of the secondary winding of transformer is the high communication number after isolation, high communication number is connected to the first input end of summing circuit, and another termination output terminal of the secondary winding of transformer is with reference to ground; Input signal is connected to the in-phase input end of the second operational amplifier simultaneously, and the output of the second operational amplifier is by resistance R
2be connected to the light emitting diode of the photoelectrical coupler in optical coupling isolation circuit, another termination input end of light emitting diode is with reference to ground, and the first photodiode one termination power+V1 of photoelectrical coupler, the other end of the first photodiode is by resistance R
3be connected with the inverting input of the second operational amplifier, resistance R
3another termination reference voltage-Vref1, the second photodiode one termination power+V2 in photoelectrical coupler, the other end receives adjustable resistance R
4with the in-phase input end of the 3rd operational amplifier, another termination reference voltage-Vref2 of adjustable resistance R4; Adjustable resistance R
5form low-pass first order filter with electric capacity C2, the output termination low-pass first order filter of the 3rd operational amplifier, the output of low-pass first order filter is the low path signal after isolation, and low path signal is connected to the second input end of summing circuit.Carry out adjustment by the amplitude of adjustable resistance R4 to Gao Lu and low path signal and make it coupling, by adjustable resistance R5, Hi-pass filter and low-pass filter frequency are regulated, make it consistent.Light-coupled isolation channel gain is adjustable, makes it to mate with transformer isolation passage.It is adjustable that low-pass first order filter-3dB ends frequency, makes it to end frequency with the-3dB of single order Hi-pass filter identical or almost identical.Or transformer isolation channel gain is adjustable, make it to mate with light-coupled isolation passage.It is adjustable that single order Hi-pass filter-3dB ends frequency, makes it to end frequency with the-3dB of low-pass first order filter identical or almost identical.
As preferably, the high-frequency cut-off frequency of described optical coupling isolation circuit is higher than the cutoff frequency 100 times of low-pass first order filter, and-3dB the cutoff frequency of single order Hi-pass filter is 10kHz-30kHz.The signal of the output of the low-pass first order filter after making to be connected on optical coupling isolation circuit, compared with the signal exported when this low-pass first order filter is directly received input signal, is linear.
As preferably, the low-frequency cut-off frequency of described transformer isolation circuit lower than single order Hi-pass filter cutoff frequency 1/100 ,-3dB the cutoff frequency of single order Hi-pass filter is 10kHz-30kHz.The signal that single order Hi-pass filter is exported can linearly by transformer from elementary be coupled to secondary.
Shunt circuit linearity insulating circuit apparatus of the present invention possesses following advantage: after the high pass and low-pass filter of single order, at Gao Lu and low path signal after transformer and optical coupling isolation circuit isolation, again through summing circuit, well can reappear input signal, have smooth amplitude response and linear phase response, it is corresponding with step to have accurate impulse response, improves overall buffer circuit common-mode rejection ratio, reduce interference, improve signal quality.
Accompanying drawing explanation
A kind of structured flowchart of Fig. 1 shunt circuit linearity insulating circuit apparatus of the present invention.
The another kind of structured flowchart of Fig. 2 shunt circuit linearity insulating circuit apparatus of the present invention.
The concrete implementing circuit of Fig. 3 Fig. 2.
Fig. 4 is the amplitude-frequency response of Gao Lu, low path and output signal in Fig. 3 circuit.
Fig. 5 is the phase-frequency response of Gao Lu, low path and output signal in Fig. 3 circuit.
Embodiment
Below by embodiment, and by reference to the accompanying drawings, the technical scheme of invention is described in further detail.
Embodiment 1:
As shown in Figure 1, a kind of shunt circuit linearity insulating circuit apparatus, comprises high road signal path and low path signal path, and input signal after too high road signal path and the isolation of low path signal path frequency division, then exports through summing circuit.High road signal path comprises single order Hi-pass filter and transformer isolation circuit, the low-frequency cut-off frequency of transformer should far below the cutoff frequency of single order Hi-pass filter,-3dB the cutoff frequency of single order Hi-pass filter is usually got 10kHz-30kHz and is advisable, low frequency-3dB the cutoff frequency of transformer isolation circuit is less than 1/100 of the cutoff frequency of single order Hi-pass filter, namely correspondence is less than 100Hz-300Hz, the high-frequency cut-off frequency of the circuit of transformer isolation depends on the high frequency response demand to buffer circuit in reality, usually at 2MHz-500MHz.Single order Hi-pass filter is connected to the input end of transformer isolation circuit, and the input end of single order Hi-pass filter is connected with input signal, and the output terminal of transformer isolation circuit is connected to the input end of summing circuit.Low path signal path comprises low-pass first order filter and optical coupling isolation circuit, the high-frequency cut-off frequency of optical coupling isolation circuit should far above the cutoff frequency of low-pass first order filter,-3dB the cutoff frequency of low-pass first order filter is identical with the-3dB cutoff frequency of single order Hi-pass filter, namely usually 10kHz-30kHz is got, high frequency-3dB the cutoff frequency of optical coupling isolation circuit should be greater than 100 times of the cutoff frequency of low-pass first order filter and be advisable, namely correspondence is greater than 1000kHz-3000kHz, under the low frequency end of the circuit of light-coupled isolation can be operated in 0Hz and direct current signal usually.Low-pass first order filter is connected to the input end of optical coupling isolation circuit, and the input end of low-pass first order filter is connected with input signal, and the output terminal of optical coupling isolation circuit is connected to the input end of summing circuit.-3dB the cut off of single order Hi-pass filter is identical or almost identical with the-3dB cut off of low-pass first order filter.
Embodiment 2:
As shown in Figure 2, a kind of shunt circuit linearity insulating circuit apparatus, single order Hi-pass filter is arranged on the input side of transformer channels, because optical coupling isolation circuit includes faint light Current amplifier, easy introducing noise and interference, therefore low-pass filter is contained in optical coupling isolation circuit output terminal, can filtering or reduce optical coupling isolation circuit introduce noise and interference, improve quality of output signals.
As shown in Figure 3, input signal 1 is connected to single order Hi-pass filter 2.Electric capacity C
13 and resistance R
14 form single order Hi-pass filter 2, and it exports the input end connecing the first operational amplifier 5, and the first operational amplifier 5 exports and is connected with transformer 6 armature winding one end, and another termination input side of transformer 6 armature winding is with reference to ground 7.The output signal of transformer 6 secondary winding one end is isolation Hou Gao road signal 8, and high road signal 8 is connected to an input end of summing circuit 9.Another termination outgoing side of transformer 6 secondary winding is with reference to ground 10.
Input signal 1 is also connected to the input end of optical coupling isolation circuit simultaneously, i.e. the in-phase input end of the second operational amplifier 11.The output of the second operational amplifier 11 is by resistance R
212 are connected to the light emitting diode 14 in photoelectrical coupler 13, and another termination input side of light emitting diode 14 is with reference to ground 7.The first photodiode 15 1 termination power+V1 in photoelectrical coupler 13, the other end receives resistance R
316 and second inverting input of operational amplifier 11.Resistance R
316 another termination reference voltage-Vref1.The second photodiode 17 1 termination power+V2 in photoelectrical coupler 13, the other end receives the first adjustable resistance R
418 and the 3rd in-phase input end of operational amplifier 19.First adjustable resistance R
418 another termination reference voltage-Vref2. adjustable resistance R
520 and electric capacity C
2the 21 output termination low-pass first order filters 22 forming low-pass first order filter the 22, three operational amplifiers 19, the output of low-pass first order filter 22 is the low path signal 23 after isolation, and this signal is connected to another input end of summing circuit 9.
Be irradiated to the first photodiode 15 and the second photodiode 17 the light simultaneous equal of light emitting diode 14.The photocurrent that first photodiode 15 produces is at resistance R
3produce voltage on 16, under the FEEDBACK CONTROL of the second operational amplifier 11, make node 24 voltage equal the low-frequency range part of input signal 1.The photocurrent produced in second photodiode 17 is substantially equal with the photocurrent that produces of the first photodiode 15, only differs from a less coefficient.Regulate adjustable resistance R
418 can make node 25 voltage equal or linear with node 24 voltage, also just equal or linear with the low-frequency range part signal voltage of input signal 1.So the low-frequency range part of input signal 1 is isolated linearly be transferred to the 3rd operational amplifier 19, and time delay is minimum, without the need to compensation of delay.3rd operational amplifier 19 exports and is connected to low-pass first order filter 22, carries out first-order low-pass ripple to the low-frequency range part of the input signal 1 after isolation.
The low-frequency cut-off frequency of transformer 6 should far below the cutoff frequency of single order Hi-pass filter 2, the signal that single order Hi-pass filter 2 is exported can linearly by transformer 6 from elementary be coupled to secondary.
The high-frequency cut-off frequency of optical coupling isolation circuit should far above the cutoff frequency of low-pass first order filter 22, the signal of the output of the low-pass first order filter 22 after making to be connected on optical coupling isolation circuit, compared with the signal exported when this low-pass first order filter directly being received input signal 1, be linear.
The amplitude-frequency response of curve 26 Shi Gao road signal 8 compared with input signal 1 in Fig. 4; Curve 27 is low path signal 23 amplitude-frequency responses compared with input signal 1.Stitching 28 is output signal 29 amplitude-frequency responses compared with input signal 1 of summing circuit 9, and stitching 28 is a horizontal linear, has nothing to do with frequency, and visible output 29 is linear relationship with input signal 1 in amplitude.
The phase-frequency response curve of curve 30 Shi Gao road signal 8 compared with input signal 1 in Fig. 5; Curve 31 is low path signal 23 phase-frequency response curves compared with input signal 1.Stitching 32 is output signal 29 phase-frequency response curves compared with input signal 1 of summing circuit 9, and stitching 32 is a horizontal linear, is linear phase response.
Like this, input signal 1 by linearly isolation be transferred to output terminal.
In reality, inputting with reference to ground 7 and output reference ground 10 is not equipotential usually, and may have high-voltage difference, the isolation barrier be made up of transformer 6, photoelectrical coupler 13, can tolerate this potential difference (PD).
-Vref1 makes photoelectrical coupler 13 produce a bias current, makes optical coupling isolation circuit can accept negative polarity input voltage.Node 25 initial potential is adjusted to 0. and usually gets-Vref2 and equal-Vref1 by-Vref2.
Regulate adjustable resistance 18 that the amplitude of low path signal 23 can be made to mate with high road signal 8; Regulate adjustable resistance R
520 can make the cutoff frequency of low-pass first order filter 22 identical with the cutoff frequency of single order Hi-pass filter 2 or almost identical, thus obtain as the response characteristic in Fig. 4 and Fig. 5.Also the gain of adjustable Gao Lu is mated with low path, regulates the cut-off frequency of Hi-pass filter identical with low-pass filter or almost identical.
those skilled in the art are when understanding, and some part of the present invention can have other embodiment.
Above-mentioned most preferred embodiment lists some preferred component type and numerical value, but obviously, can change, adds or remove some amplifiers, transformer, photoelectrical coupler, and about the element of model and numerical value, to adapt to the needs of various special-purpose.
Equally, the present invention described above implements with discrete elements, but some of them amplifier, parts and subsystem also can make the assembly of integrated circuit, hybrid circuit or multi-chip module.
In addition, although what describe in most preferred embodiment is regulate relevant element in a manual manner low path gain is mated with high road, High Pass Filter Cutoff Frequency mates with low-pass filter to make, parameter regulates and also can to use in the present invention on any efficient circuit assembly manually or automatically.
Those skilled in the art is clear, and various amendment all can be made in the many details aspects for the above embodiment of the present invention, but this does not depart from design of the present invention.The present invention also can be used for relevant signals isolation aspect, and is not only on electric signal measurement equipment.Therefore, scope of the present invention should only have appending claims to determine.
Claims (3)
1. shunt circuit linearity insulating circuit apparatus, it is characterized in that: comprise the high road signal path be made up of single order Hi-pass filter and transformer isolation circuit, also comprise the low path signal path be made up of low-pass first order filter and optical coupling isolation circuit, high road signal path and low path signal path are in input end parallel connection, and the output terminal of high road signal path and the output terminal of low path signal path are connected on summing circuit; Single order Hi-pass filter is identical with the cutoff frequency of low-pass first order filter, and input signal after frequency division and the isolation of too high road signal path and low path signal path, then exports summing signal through summing circuit and is reduced into input signal; Described single order Hi-pass filter is connected to the input end of transformer isolation circuit, and low-pass first order filter is connected to the output terminal of optical coupling isolation circuit; Described single order Hi-pass filter is by electric capacity C
1with resistance R
1form, input signal is connected to single order Hi-pass filter, the output of single order Hi-pass filter connects the in-phase input end of the first operational amplifier, the output of the first operational amplifier is connected with one end of the armature winding of the transformer in transformer isolation circuit, another termination input end of the armature winding of transformer is with reference to ground, the output signal of one end of the secondary winding of transformer is the high communication number after isolation, high communication number is connected to the first input end of summing circuit, and another termination output terminal of the secondary winding of transformer is with reference to ground; Input signal is connected to the in-phase input end of the second operational amplifier simultaneously, and the output of the second operational amplifier is by resistance R
2be connected to the light emitting diode of the photoelectrical coupler in optical coupling isolation circuit, another termination input end of light emitting diode is with reference to ground, and the first photodiode one termination power+V1 of photoelectrical coupler, the other end of the first photodiode is by resistance R
3be connected with the inverting input of the second operational amplifier, resistance R
3another termination reference voltage-Vref1, the second photodiode one termination power+V2 in photoelectrical coupler, the other end receives adjustable resistance R
4with the in-phase input end of the 3rd operational amplifier, another termination reference voltage-Vref2 of adjustable resistance R4; Adjustable resistance R
5form low-pass first order filter with electric capacity C2, the output termination low-pass first order filter of the 3rd operational amplifier, the output of low-pass first order filter is the low path signal after isolation, and low path signal is connected to the second input end of summing circuit.
2. shunt circuit linearity insulating circuit apparatus according to claim 1, it is characterized in that: the high-frequency cut-off frequency of described optical coupling isolation circuit is higher than the cutoff frequency 100 times of low-pass first order filter, and-3dB the cutoff frequency of low-pass first order filter is 10kHz-30kHz.
3. shunt circuit linearity insulating circuit apparatus according to claim 1 and 2, it is characterized in that: the low-frequency cut-off frequency of described transformer isolation circuit lower than single order Hi-pass filter cutoff frequency 1/100 ,-3dB the cutoff frequency of single order Hi-pass filter is 10kHz-30kHz.
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| CN101645708A (en) * | 2009-07-21 | 2010-02-10 | 叶克江 | Linear isolating circuit based on optical couplers and method |
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| CN202693656U (en) * | 2012-06-15 | 2013-01-23 | 杭州祺来电子有限公司 | Shunting linear isolation circuit |
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