CN103575960A - Giant magnetoresistance effect current sensor - Google Patents

Giant magnetoresistance effect current sensor Download PDF

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CN103575960A
CN103575960A CN201310520095.5A CN201310520095A CN103575960A CN 103575960 A CN103575960 A CN 103575960A CN 201310520095 A CN201310520095 A CN 201310520095A CN 103575960 A CN103575960 A CN 103575960A
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resistance
giant magnetoresistance
current sensor
voltage
output
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CN103575960B (en
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杨晓光
解存福
李元园
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Yasin Perception Technology Tianjin Co ltd
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Hebei University of Technology
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Abstract

The invention relates to devices for measuring currents, in particular to a giant magnetoresistance effect current sensor with a magnetic shielding shell and a bias coil. The giant magnetoresistance effect current sensor comprises the U-shaped magnetic shielding shell, a giant magnetoresistance chip, a bias coil winding, a current-carrying conductor, a PCB, a bias current source and a signal processing circuit, wherein the probe of the giant magnetoresistance effect current sensor is formed by the U-shaped magnetic shielding shell, the giant magnetoresistance chip, the bias coil winding, the current-carrying conductor and the PCB, the signal processing circuit comprises a bias magnetic field generating circuit, a giant magnetoresistance chip supply voltage switching circuit, a reference voltage generating circuit and an improved difference operational amplification circuit, the magnetic shielding shell overcomes the defect that magnetic fields are prone to being simultaneously influenced by an outside stray magnetic field due to the high sensitivity of giant magnetoresistance on the magnetic fields, and meanwhile hysteresis errors are reduced and alternate and direct currents are precisely measured through the method of providing the bias coil winding for a bias magnetic field.

Description

Giant magnetoresistance effect current sensor
Technical field
Technical scheme of the present invention relates to for measuring the device of electric current, specifically giant magnetoresistance effect current sensor.
Background technology
Along with the development of Power Electronic Technique, the demand of compact high performance current sensor increases gradually.Traditional electric current detecting method comprises shunt, current transformer, Luo-coil and Hall element; New type of current detection technique comprises fluxgate sensor, giant magnetoresistance effect current sensor and Fibre Optical Sensor.By contrast, giant magnetoresistance effect current sensor has himself outstanding advantage performance, has unique magnetic inductive capacity.The features such as giant magnetoresistance effect current sensor has that magnetic field high sensitivity, high workload bandwidth range, temperature stability are splendid to applying, low-power consumption and miniaturization.
Yet, due to the extremely sensitive characteristic of giant magnetoresistance to magnetic field, make them be subject to the impact of extraneous stray magnetic field simultaneously.The field source of these stray magnetic fields comprises the electric equipments such as motor and transformer, or sensor current-carrying conductor around etc.Stray magnetic field can cause that sensor produces larger output error, has affected the accuracy of current measurement result.Meanwhile, when by measuring magnetic field is weak and positive and negative while alternately changing, the coupling due to weak between giant magnetoresistance adjacent ferromagnetic, makes giant magnetoresistance chip list reveal obvious hysteresis effect.In prior art, giant magnetoresistance chip used is unipolarity output characteristics in addition, and when being measured as alternating current, output waveform is similar to full-wave rectification output, and the easy distortion of waveform of output, causes larger output error like this.
CN102043083A discloses a kind of giant magnetoresistance array current sensor, measures when realizing alternating current-direct current, and can complete Digital Transmission, the storage of information.Yet the weak point of this sensor is: 1. this sensor probe needs the Al-Ni-Co permanent magnet of 8 giant magnetoresistance chips and 16 bar shapeds to form, and cost is higher, and sonde configuration is comparatively complicated; 2. utilize permanent magnet that bias magnetic field is provided, the magnetic field producing is like this stable not, and permanent magnet, along with the variation of the environment temperature phenomenon of can demagnetizing, causes output signal out of true; 3. this sensor is sampled and is kept and A/D conversion the voltage signal of probe output, then processes and carry out spatial fourier transform through FPGA, and so signal processing circuit is comparatively complicated.
CN101038305B has proposed the array type current sensor of a kind of giant magnetic impedance having based on amorphous soft magnet band (GMI) effect, its defect has 3 points: 1. two array amorphous current sensor probes are required to just the same and Parallel Symmetric, but because the reasons such as manufacturing process are difficult to guarantee that two array amorphous current sensor probes are in full accord, consequent temperature is floated phenomenon can cause certain output error; 2. sensor circuit partly comprises two-way Bryant thatch oscillatory circuit and rectification circuit, relates to the devices such as starting of oscillation electric capacity, crystal oscillator, transistor, high-frequency operational amplifier, commutation diode, electric capacity of voltage regulation and filter capacitor, and circuit is comparatively complicated; 3. utilize permanent magnet provide bias magnetic field same exist as in CN102043083A 2. as described in defect and deficiency.
Summary of the invention
Technical matters to be solved by this invention is: giant magnetoresistance effect current sensor is provided, be a kind of giant magnetoresistance effect current sensor with magnetic shielding shell and bias coil, the existence of magnetic shielding shell has overcome and on the extremely sensitive characteristic in magnetic field, makes them be subject to the defect of the impact of extraneous stray magnetic field because of giant magnetoresistance simultaneously; By bias coil winding, provide the method for bias magnetic field to reduce hysteresis error and realize the accurate measurement to ac and dc current again simultaneously.
The present invention solves this technical problem adopted technical scheme: giant magnetoresistance effect current sensor, it is a kind of giant magnetoresistance effect current sensor with magnetic shielding shell and bias coil, its formation comprises U-shaped magnetic shielding shell, giant magnetoresistance chip, bias coil winding, current-carrying conductor, pcb board, bias current sources and signal processing circuit, wherein, by U-shaped magnetic shielding shell, giant magnetoresistance chip, bias coil winding, current-carrying conductor and pcb board form the probe of giant magnetoresistance effect current sensor, above-mentioned signal processing circuit comprises bias magnetic field circuit for generating, giant magnetoresistance chip power supply voltage conversion circuit, generating circuit from reference voltage and modified calculus of differences amplifying circuit, pcb board is placed in U-shaped magnetic shielding shell, giant magnetoresistance chip fixed placement is above pcb board, current-carrying conductor is placed in the below of giant magnetoresistance chip, bias coil winding is wrapped on giant magnetoresistance chip uniformly, the output voltage of giant magnetoresistance chip power supply voltage conversion circuit is connected to the power pins of giant magnetoresistance chip, bias current sources is connected to bias coil winding two ends, two input ends of modified calculus of differences amplifying circuit are connected to the positive output end of giant magnetoresistance chip and the negative output terminal of giant magnetoresistance chip, the output voltage V ref of generating circuit from reference voltage is connected to the positive input terminal of modified calculus of differences amplifying circuit, stack through modified calculus of differences input amplifier signal, the output signal of the last output terminal output current sensor at modified calculus of differences amplifying circuit, form thus giant magnetoresistance current sensor.
Above-mentioned giant magnetoresistance effect current sensor, what described U-shaped magnetic shielding shell adopted is that permalloy material is made, its resistivity is 0.56 μ Ω m, and Curie point is 400 ℃, and saturation induction density is Bs=0.7T, coercivity H under saturation induction density is not more than 1.6A/m, the magnetic permeability that DC magnetic performance meets in 0.08A/m magnetic field intensity is not less than 37.5mH/m, and thickness is 1mm, and width is 7mm, be highly 10mm, length is 13mm.
Above-mentioned giant magnetoresistance effect current sensor, described giant magnetoresistance chip is GMR chip, employing be the AA002-02 that U.S. NVE company produces.
Above-mentioned giant magnetoresistance effect current sensor, described bias magnetic field circuit for generating consists of chip LT3092 and bias coil winding L, chip LT3092 utilizes an internal current source and error amplifier and two external resistor Rset and resistor Rout that output current is provided, the size of the resistance of regulating resistor Rset and resistor Rout can obtain a constant output current that is positioned at 0.5mA to 200mA, LT3092 output terminal is connected to bias coil winding L, bias coil winding L other end ground connection, the coil diameter of bias coil winding L is 0.08mm, the number of turn is 50 circles, direct current resistance is 3.487 Ω, the DC current size of passing through is 50mA, resistor Rset resistance is 20k Ω, resistor Rout resistance is 4k Ω.
Above-mentioned giant magnetoresistance effect current sensor, the constituted mode of described giant magnetoresistance chip power supply voltage conversion circuit is: the input end Vin of voltage stabilizer VR7805 meets giant magnetoresistance current sensor system supplying DC electricity power supply+15V, the filter capacitor C1 of 0.33uF is connected in parallel between the input end Vin of voltage stabilizer VR7805 and the earth terminal of voltage stabilizer VR7805, the output end vo ut stable output of voltage stabilizer VR7805+direct current of 5V voltage, the filter capacitor C2 of 0.1uF is connected in parallel between the output end vo ut of voltage stabilizer VR7805 and the earth terminal of voltage stabilizer VR7805, the output voltage of Vout pin is stable 5V direct current thus.
Above-mentioned giant magnetoresistance effect current sensor, the constituted mode of described generating circuit from reference voltage is: operational amplifier U1A and resistance R 1 and R2 and R3 form anti-phase input scale operation circuit, the normal phase input end of one termination U1A of resistance R 1, the other end ground connection of resistance R 1, the inverting input of one termination U1A of resistance R 2, the voltage source of another termination direct current 5V of resistance R 2, inverting input and the output terminal of U1A received respectively at resistance R 3 two ends, the supply voltage of U1A is+15V and-15V; The output terminal of U1A is received the normal phase input end of U1B, the inverting input of U1B and the output terminal formation voltage follower that connects together, the model of operational amplifier U1A and operational amplifier U1B is LF353, above-mentioned resistance R 1 resistance is 8.2k Ω, resistance R 2 resistances are 3.6k Ω, and resistance R 3 resistances are 10k Ω.
Above-mentioned giant magnetoresistance effect current sensor, the formation of described modified calculus of differences amplifying circuit is: the inverting input of a termination operational amplifier A 1 of resistance R 4, the output terminal of another termination operational amplifier A 2 of resistance R 4, the inverting input of one termination operational amplifier A 2 of resistance R 5, the output terminal of another termination operational amplifier A 1 of resistance R 5, the positive input terminal of operational amplifier A 2 is connected to the output terminal of operational amplifier A 1, inverting input and the output terminal of operational amplifier A 2 received respectively at the two ends of resistance R 6, one termination voltage U 1 of resistance R 1, the inverting input of another termination operational amplifier A 1 of resistance R 1, one termination voltage U 2 of resistance R 2, the normal phase input end of another termination operational amplifier A 1 of resistance R 2, the normal phase input end of one termination operational amplifier A 1 of resistance R 3, the other end ground connection of resistance R 3, the model of operational amplifier A 1 and operational amplifier A 2 is LF356, above-mentioned resistance R 1 resistance is 27k Ω, resistance R 2 resistances are 27k Ω, resistance R 3 resistances are 270k Ω, resistance R 4 resistances are 270k Ω, resistance R 5 resistances are 1k Ω, resistance R 6 resistances are 10k Ω.
Above-mentioned giant magnetoresistance effect current sensor, related device and parts are all that known approach obtains, the installation method of all parts is that those skilled in the art grasp.
The invention has the beneficial effects as follows: compared with prior art, outstanding substantive distinguishing features of the present invention is:
(1) giant magnetoresistance current sensor principle of work is the magnetic field producing based on current-carrying conductor, for being increased as far as possible, the magnetic field at chip place guarantees the interference minimum that extraneous stray magnetic field causes chip place simultaneously, effective method is application magnetic shielding technology, i.e. magnetic shielding shell of the present invention and be designed to U-shaped structure.Magnetic shielding is for isolating the measure of magnetic Field Coupling, is to utilize magnetic flux to change the direction of extraneous stray magnetic field along the principle of low reluctance path circulation, thereby the magnetic line of force is gathered in shield.From magnetic resistance formula Rm=l/ μ S, the magnetic permeability of magnetic resistance and material is inversely proportional to, and therefore generally will select high-permeability material.In order to increase the range of sensing range, should select the permeability magnetic material of high saturation magnetic induction, in order to obtain in real time accurate testing result, select low magnetic hysteresis, low-coercivity material simultaneously.Conventional magnetic shielding material comprises: electromagnetism soft iron, siliconized plate, permalloy, non-crystaline amorphous metal etc.Wherein non-crystaline amorphous metal magnetic permeability is the highest, but price is comparatively expensive, electromagnetism soft iron and siliconized plate low price, but magnetic permeability is lower.From the viewpoint of performance and cost, the present invention has selected permalloy material as shielding case.
(2) although the magnetic shielding shell being formed by the permalloy magnetic material of high magnetic permeability, can effectively assemble wanted signal, reduce the impact of extraneous stray magnetic field simultaneously, but detection probe giant magnetoresistance chip used is unipolarity output characteristics, when being measured as alternating current, output waveform is similar to full-wave rectification output, and the easy distortion of waveform of output, causes larger output error like this.In addition, due to the present invention with the current sensor based on giant magnetoresistance effect of magnetic shielding shell and bias coil because giant magnetoresistance chip is magnetic element, therefore there is typical magnetic characteristic, there is hysteresis and saturated phenomenon.When being surpassed certain value by measuring magnetic field, giant magnetoresistance chip reaches capacity, and output no longer increases.When weak by measuring magnetic field and while changing between positive and negative zero crossing, the coupling due to weak between giant magnetoresistance adjacent ferromagnetic, makes giant magnetoresistance chip list reveal obvious hysteresis effect.Meanwhile, giant magnetoresistance chip used is unipolarity output characteristics, and when being measured as alternating current, output waveform is similar to full-wave rectification output, and the easy distortion of waveform of output, causes larger output error like this.The present invention has designed unique bias magnetic field structure for this reason, and it is that linear zone is all brought up in the magnetic field of GMR chip that the stack by magnetic field makes to act on giant magnetoresistance chip.Like this when when by measuring magnetic field, a DC offset voltage of giant magnetoresistance chip output, when having tested electric current, the output voltage of giant magnetoresistance chip is on the basis of former bias voltage, to have superposeed again the magnetic field being produced by tested electric current and the voltage that produces, provides DC bias magnetic field can effectively improve the linearity and the hysteresis error of sensor.
(3), because giant magnetoresistance chip signal output is faint differential signal, therefore need to apply calculus of differences amplifying circuit signal is amplified.General calculus of differences amplifying circuit is comprised of an integrated operational amplifier and external resistor network, and this structure causes input and output phase differential also to increase along with the increase of measured signal frequency, has affected the bandwidth range of measured signal.In order to reduce phase error, the present invention proposes a kind of modified calculus of differences amplifying circuit, its structure is to have introduced amplifier resistor network in the backfeed loop of general calculus of differences amplifying circuit, can effective compensation phase error, there is higher common-mode rejection ratio simultaneously.The bias voltage that the reference voltage Vref of this modified calculus of differences amplifying circuit positive input terminal produces for eliminate bias magnetic field, make the final output of giant magnetoresistance current sensor of the present invention obtain the voltage of a bipolar output, also output has and just has negative voltage.
Compared with prior art, marked improvement of the present invention is:
(1) with the current sensor based on giant magnetoresistance effect of magnetic shielding shell and bias coil, the maximum error in full range is 0.8% in the present invention, and has higher sensitivity and precision;
(2) the present invention adopts permalloy material with the magnetic shielding shell of the current sensor based on giant magnetoresistance effect of magnetic shielding shell and bias coil, it has advantages of high magnetic permeability, low-coercivity, high squareness ratio, core loss is low and high-temperature stability good, and saturation induction density is higher, wearing quality and corrosion stability are all strong.Add magnetic shielding shell and not only make the sensitivity of sensor output be greatly improved, the linearity has also had improvement to a certain extent simultaneously.
(3) the present invention has effectively assembled wanted signal with the current sensor based on giant magnetoresistance effect of magnetic shielding shell and bias coil, reduces the impact of extraneous stray magnetic field simultaneously.When there is the extraneous stray magnetic field of 2mT, the output error signal that the present invention has the giant magnetoresistance current sensor of shielding case is about 4mV, be about 400mV with the output error signal of the current sensor of unshielded shell and compare, be subject to the impact of extraneous stray magnetic field to reduce to be about 100 times.
Accompanying drawing explanation
Below in conjunction with drawings and Examples, the present invention is further described.
Fig. 1 is the sonde configuration figure of giant magnetoresistance current sensor of the present invention.
Fig. 2 is the schematic diagram that interacts between each component part in giant magnetoresistance current sensor of the present invention.
Fig. 3 is the structural representation of giant magnetoresistance current sensor of the present invention.
Fig. 4 is the giant magnetoresistance chip power supply voltage conversion circuit schematic diagram of giant magnetoresistance current sensor of the present invention.
Fig. 5 is the bias magnetic field circuit for generating schematic diagram of giant magnetoresistance current sensor of the present invention.
Fig. 6 is the generating circuit from reference voltage schematic diagram of giant magnetoresistance current sensor of the present invention.
Fig. 7 is the circuit diagram of general type calculus of differences amplifying circuit.
Fig. 8 is the modified calculus of differences amplifying circuit schematic diagram of giant magnetoresistance current sensor of the present invention.
Fig. 9 is the B-H loop of giant magnetoresistance current sensor of the present invention in two kinds of situations of being and not being bias magnetic field.
Figure 10 is the input-output characteristic curve of giant magnetoresistance current sensor of the present invention in two kinds of situations of being and not being magnetic shielding shell.
Figure 11 is giant magnetoresistance current sensor of the present invention current sensor relative error curve map when adding magnetic shielding shell.
In figure, 1. magnetic shielding shell, 2. bias coil winding, 3. giant magnetoresistance chip, 4. current-carrying conductor, 5.PCB plate, 6. bias current sources, 7. modified calculus of differences amplifying circuit, 8. generating circuit from reference voltage, 9. giant magnetoresistance chip positive output end, 10. giant magnetoresistance chip negative output terminal.
Embodiment
Embodiment illustrated in fig. 1 showing, the probe of giant magnetoresistance current sensor of the present invention comprises magnetic shielding shell 1, bias coil winding 2, giant magnetoresistance chip 3, current-carrying conductor 4 and pcb board 5, magnetic shielding shell 1 is U-shaped structure, from the viewpoint of performance and cost, selected the material of permalloy as shielding case, the magnetic field at giant magnetoresistance chip 3 places is increased as far as possible, guarantee the interference minimum that extraneous stray magnetic field causes giant magnetoresistance chip 3 places simultaneously.Because giant magnetoresistance chip 3 has the characteristic of unipolarity output, therefore by bias coil winding 2, provide DC bias magnetic field, bias coil winding 2 is wrapped on giant magnetoresistance chip 3 uniformly, and the stack by magnetic field makes the magnetic field that acts on giant magnetoresistance chip 3 all bring up to linear zone.Giant magnetoresistance chip 3 is fixed on pcb board 5.Current-carrying conductor 4 is placed between giant magnetoresistance chip 3 and pcb board 5, passes into electric current and produces magnetic field, giant magnetoresistance chip 3 output difference divided voltage signal under by the effect of measuring magnetic field in current-carrying conductor 4.Due to output signal and had linear change rule between measuring magnetic field, the voltage of output is proportional to tested electric current, thereby realizes the measurement function of current signal.
Embodiment illustrated in fig. 2 showing, in giant magnetoresistance current sensor of the present invention, between each component part, interacting is: giant magnetoresistance chip is placed in magnetic shielding shell; Bias magnetic field circuit for generating acts on giant magnetoresistance chip, makes the magnetic field that acts on giant magnetoresistance chip all bring up to linear zone; The magnetic field that tested electric current produces acts on giant magnetoresistance chip after the poly-magnetic of magnetic shielding shell, and giant magnetoresistance chip output voltage signal enters the general type calculus of differences amplifying circuit in the amplifying circuit of modified calculus of differences shown in dotted line frame in figure; The DC offset voltage causing for eliminate bias magnetic generation circuit, the reference voltage that has added generating circuit from reference voltage to produce at the input amplifier of modified calculus of differences shown in dotted line frame, the stack of the bias voltage producing by this reference voltage and bias magnetic field circuit for generating, plays the effect of bias compensation.Because general type calculus of differences amplifying circuit is along with the increase of measured signal frequency causes input and output phase differential also to increase, therefore in the backfeed loop of general type calculus of differences amplifying circuit, introduced amplifier resistor network, so general type calculus of differences amplifying circuit is played to effect of phase compensation, form thus the modified calculus of differences amplifying circuit shown in dotted line frame, output signal and the tested electric current of final modified calculus of differences amplifying circuit are forward proportionate relationship.
Embodiment illustrated in fig. 3 showing, the structure of giant magnetoresistance current sensor of the present invention is: giant magnetoresistance chip 3 is placed in magnetic shielding shell 1, current-carrying conductor 4 is placed in the below of giant magnetoresistance chip 3, bias coil winding 2 is wrapped on giant magnetoresistance chip 3 uniformly, bias current sources 6 is connected to bias coil winding 2 two ends, for giant magnetoresistance chip 3 provides bias magnetic field.The magnetic fields that current-carrying conductor 4 produces is in giant magnetoresistance chip 3 output voltage signals, output signal enters modified calculus of differences amplifying circuit 7 and amplifies, generating circuit from reference voltage 8 is added to the input end of modified calculus of differences amplifying circuit 7, so through generating circuit from reference voltage 8 and the bias voltage superposition that the bias magnetic field being produced by bias coil winding produces, make the voltage signal of one of modified calculus of differences amplifying circuit 7 output and the proportional routine relation of tested electric current.
Embodiment illustrated in fig. 4 showing, the constituted mode of the giant magnetoresistance chip power supply voltage conversion circuit of giant magnetoresistance current sensor of the present invention is: the input end Vin of voltage stabilizer VR7805 meets giant magnetoresistance current sensor system supplying DC electricity power supply+15V, the filter capacitor C1 of 0.33uF is connected in parallel between the input end Vin of voltage stabilizer VR7805 and the earth terminal of voltage stabilizer VR7805, the output end vo ut stable output of voltage stabilizer VR7805+direct current of 5V voltage, the filter capacitor C2 of 0.1uF is connected in parallel between the output end vo ut of voltage stabilizer VR7805 and the earth terminal of voltage stabilizer VR7805, the output voltage of Vout pin is stable 5V direct current thus.Because the required supply voltage of giant magnetoresistance chip is positive 5V, and giant magnetoresistance current sensor system power supply is positive and negative 15V, therefore by the effect of voltage stabilizer VR7805, produce the required supply voltage of stable DC voltage supply giant magnetoresistance chip of 5V.
Embodiment shown in Fig. 5 shows, the bias magnetic field circuit for generating of giant magnetoresistance current sensor of the present invention consists of chip LT3092 and bias coil winding L.In Fig. 5 square frame, show the inner structure of the DC current source of the power voltage supply of using 5V, its chips LT3092 utilizes an internal current source and error amplifier and two external resistor Rset and resistor Rout that output current is provided, the size of the resistance of regulating resistor Rset and resistor Rout can obtain a constant output current that is positioned at 0.5mA to 200mA, IN is the input end pin of LT3092 chip, the power supply input end that this pin is chip.OUT is the output terminal of chip, and SET is chip arranges end, and SET is connected to the in-phase input end of chip internal error amplifier, and the offset operation point of electric current can be set simultaneously.10 μ A are LT3092 chip internal reference current source, and this reference current source flows through resistor Rset and produces a voltage, and this voltage is applied to another resistor Rout and produces output current, and resistor Rout is connected to chip OUT output terminal and resistor Rset two ends.LT3092 output terminal is connected to bias coil winding L, bias coil winding L other end ground connection, and the coil diameter of bias coil winding L is 0.08mm, and the number of turn is 50 circles, and direct current resistance is 3.487 Ω, and the DC current size of passing through is 50mA.In figure, resistor Rset resistance is 20k Ω, and resistor Rout resistance is 4k Ω.
Embodiment shown in Fig. 6 shows, the constituted mode of the generating circuit from reference voltage of giant magnetoresistance current sensor of the present invention is: operational amplifier U1A and resistance R 1 and R2 and R3 form anti-phase input scale operation circuit, the normal phase input end c of one termination U1A of resistance R 1, the other end ground connection of resistance R 1.The inverting input b of one termination U1A of resistance R 2, the voltage source of another termination direct current 5V of resistance R 2, inverting input b and the output terminal a of U1A received respectively at resistance R 3 two ends, the supply voltage of U1A is+15V end h and-15V holds d; The output terminal a of U1A receives the normal phase input end e of U1B, the inverting input f of U1B and the output terminal g formation voltage follower that connects together.Because voltage follower has, input impedance is high, output impedance is low, and late-class circuit is equivalent to a constant pressure source, and its output voltage is not affected by loaded impedance, so obtain a constant reference voltage Vref.The model of operational amplifier U1A and operational amplifier U1B is LF353.In figure, resistance R 1 resistance is 8.2k Ω, and resistance R 2 resistances are 3.6k Ω, and resistance R 3 resistances are 10k Ω.
Embodiment shown in Fig. 7 shows, the formation of the circuit of general type calculus of differences amplifying circuit is: an integrated operational amplifier and external resistor network, consist of, one termination voltage U 1 of resistance R 1, the inverting input of another termination operational amplifier of resistance R 1, one termination voltage U 2 of resistance R 2, the normal phase input end of another termination operational amplifier of resistance R 2, inverting input and the output terminal of operational amplifier received respectively at resistance R 4 two ends, the normal phase input end of one termination operational amplifier of resistance R 3, the other end ground connection of resistance R 3.Operational amplifier model is LF356.This structure causes input and output phase differential also to increase along with the increase of measured signal frequency, has affected the bandwidth range of measured signal.In figure, resistance R 1 resistance is 27k Ω, and resistance R 2 resistances are 27k Ω, and resistance R 3 resistances are 270k Ω, and resistance R 4 resistances are 270k Ω.
Embodiment shown in Fig. 8 shows, the formation of the modified calculus of differences amplifying circuit of giant magnetoresistance current sensor of the present invention is: the inverting input of a termination operational amplifier A 1 of resistance R 4, the output terminal of another termination operational amplifier A 2 of resistance R 4, the inverting input of one termination operational amplifier A 2 of resistance R 5, the output terminal Uo of another termination operational amplifier A 1 of resistance R 5 is the output terminal of modified calculus of differences amplifying circuit, the positive input terminal of operational amplifier A 2 is connected to the output terminal Uo of operational amplifier A 1, inverting input and the output terminal of operational amplifier A 2 received respectively at the two ends of resistance R 6, one termination voltage U 1 of resistance R 1, the inverting input of another termination operational amplifier A 1 of resistance R 1, one termination voltage U 2 of resistance R 2, the normal phase input end of another termination operational amplifier A 1 of resistance R 2, the normal phase input end of one termination operational amplifier A 1 of resistance R 3, the other end ground connection of resistance R 3, the model of operational amplifier A 1 and operational amplifier A 2 is LF356.In figure, resistance R 1 resistance is 27k Ω, and resistance R 2 resistances are 27k Ω, and resistance R 3 resistances are 270k Ω, and resistance R 4 resistances are 270k Ω, and resistance R 5 resistances are 1k Ω, and resistance R 6 resistances are 10k Ω.
In order to reduce phase error, the present invention proposes a kind of modified calculus of differences amplifying circuit.Compare with the general type calculus of differences amplifying circuit shown in Fig. 7, the improvement of modified calculus of differences amplifying circuit of the present invention is exactly the output terminal of the inverting input one termination amplifier A2 of resistance R 4 one termination amplifier A1, the inverting input of one termination amplifier A2 of resistance R 5, the output terminal Uo of another termination amplifier A1 of resistance R 5, the positive input terminal of amplifier A2 is also connected to the output terminal Uo of amplifier A1, and inverting input and the output terminal of amplifier A2 received respectively at the two ends of resistance R 6.Modified calculus of differences amplifying circuit of the present invention has been introduced amplifier resistor network in the backfeed loop of general type calculus of differences amplifying circuit, can effective compensation phase error, there is higher common-mode rejection ratio simultaneously.
Embodiment shown in Fig. 9 shows, in two kinds of situations of being and not being bias magnetic field, when tested electric current relation of current sensor output and input in positive stroke and revesal process in certain range, test result shows to add that the hysteresis error that has improved current sensor after bias magnetic field has obviously reduced, and the linearity has had raising to a certain degree simultaneously.
Embodiment shown in Figure 10 shows, in two kinds of situations of being and not being magnetic shielding shell, the figure that the data that the tested electric current lower sensor of difference output voltage is obtained are carried out curve fitting and obtained by matlab software, test result shows to compare without magnet shielding structure, has the sensitivity of the giant magnetoresistance current sensor of the present invention of magnetic shielding shell to be greatly improved.
Embodiment shown in Figure 11 shows giant magnetoresistance current sensor of the present invention current sensor relative error curve map when adding magnetic shielding shell.By the theoretical value of output voltage, deduct actual value, more just can obtain the relative error within the scope of this current sensor measurement divided by actual value.Based on experimental data can draw range of current be-during 20A~+ 20A, relative error has been restricted to 0.8%.
Embodiment
With above-mentioned Fig. 1, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 and all parts embodiment illustrated in fig. 8, device becomes to have the current sensor based on giant magnetoresistance effect of magnetic shielding shell and bias coil, and wherein all express in Fig. 1 shape and the position of the planform of magnetic shielding shell 1 and bias coil winding 2.Giant magnetoresistance chip 3 is GMR chip, employing be the AA002-02 that U.S. NVE company produces; What U-shaped magnetic shielding shell adopted is that permalloy material is made, its resistivity is 0.56 μ Ω m, Curie point is 400 ℃, saturation induction density is Bs=0.7T, and the coercivity H under saturation induction density is not more than 1.6A/m, and the magnetic permeability that DC magnetic performance meets in 0.08A/m magnetic field intensity is not less than 37.5mH/m, thickness is 1mm, width is 7mm, is highly 10mm, and length is 13mm.
The giant magnetoresistance current sensor that said apparatus is become carries out the experiments of measuring of DC current, and tested electric current, from-20A~20A, is measured the output voltage of modified calculus of differences amplifying circuit.The data that obtain are inputted to international business software matlab and carry out least square curve fitting, obtain the relation of the output voltage of current sensor shown in Figure 10 and tested electric current.The fit equation of this curve is respectively: while there is magnetic shielding shell, the pass of sensor output voltage and tested electric current is as shown in figure 10: Uout=119.96*I+4.1659, this formula represents the quantitative relation between tested electric current and current sensor output voltage, can obtain, the sensitivity of this current sensor is 119.96, drift is 4.1659mV, be limited in ± 3V of output voltage.Test while there is no again magnetic shielding shell, equally also with least square curve fitting, obtain sensor output voltage as shown in figure 10 and the pass of tested electric current is: Uout=47.289*I+5.7122, the sensitivity that analysis obtains current sensor is 47.289, and drift is 5.7122mV.The sensitivity that adds magnetic shielding shell can effectively increase current sensor can be found out, the drift of current sensor can be reduced simultaneously.By the theoretical value of output voltage, deduct actual value, just the relative error in the time of can obtaining this current sensor measurement scope for-20A~20A divided by actual value again, embodiment as shown in figure 11 shows giant magnetoresistance current sensor of the present invention current sensor relative error curve map when adding magnetic shielding shell, visible at-20A in the range of 20A, relative error is limited in ± 0.8% in.
Device and parts related in above-described embodiment are all that known approach obtains, and the installation method of all parts is that those skilled in the art grasp.

Claims (7)

1. giant magnetoresistance effect current sensor, it is characterized in that: be a kind of giant magnetoresistance effect current sensor with magnetic shielding shell and bias coil, its formation comprises U-shaped magnetic shielding shell, giant magnetoresistance chip, bias coil winding, current-carrying conductor, pcb board, bias current sources and signal processing circuit, wherein, by U-shaped magnetic shielding shell, giant magnetoresistance chip, bias coil winding, current-carrying conductor and pcb board form the probe of giant magnetoresistance effect current sensor, above-mentioned signal processing circuit comprises bias magnetic field circuit for generating, giant magnetoresistance chip power supply voltage conversion circuit, generating circuit from reference voltage and modified calculus of differences amplifying circuit, pcb board is placed in U-shaped magnetic shielding shell, giant magnetoresistance chip fixed placement is above pcb board, current-carrying conductor is placed in the below of giant magnetoresistance chip, bias coil winding is wrapped on giant magnetoresistance chip uniformly, the output voltage of giant magnetoresistance chip power supply voltage conversion circuit is connected to the power pins of giant magnetoresistance chip, bias current sources is connected to bias coil winding two ends, two input ends of modified calculus of differences amplifying circuit are connected to the positive output end of giant magnetoresistance chip and the negative output terminal of giant magnetoresistance chip, the output voltage V ref of generating circuit from reference voltage is connected to the positive input terminal of modified calculus of differences amplifying circuit, stack through modified calculus of differences input amplifier signal, the output signal of the last output terminal output current sensor at modified calculus of differences amplifying circuit, form thus giant magnetoresistance current sensor.
2. according to the said giant magnetoresistance effect current sensor of claim 1, it is characterized in that: what described U-shaped magnetic shielding shell adopted is that permalloy material is made, its resistivity is 0.56 μ Ω m, and Curie point is 400 ℃, and saturation induction density is Bs=0.7T, coercivity H under saturation induction density is not more than 1.6A/m, the magnetic permeability that DC magnetic performance meets in 0.08A/m magnetic field intensity is not less than 37.5mH/m, and thickness is 1mm, and width is 7mm, be highly 10mm, length is 13mm.
3. according to the said giant magnetoresistance effect current sensor of claim 1, it is characterized in that: described giant magnetoresistance chip is GMR chip, employing be the AA002-02 that U.S. NVE company produces.
4. according to the said giant magnetoresistance effect current sensor of claim 1, it is characterized in that: described bias magnetic field circuit for generating consists of chip LT3092 and bias coil winding L, chip LT3092 utilizes an internal current source and error amplifier and two external resistor Rset and resistor Rout that output current is provided, the size of the resistance of regulating resistor Rset and resistor Rout can obtain a constant output current that is positioned at 0.5mA to 200mA, LT3092 output terminal is connected to bias coil winding L, bias coil winding L other end ground connection, the coil diameter of bias coil winding L is 0.08mm, the number of turn is 50 circles, direct current resistance is 3.487 Ω, the DC current size of passing through is 50mA, resistor Rset resistance is 20k Ω, resistor Rout resistance is 4k Ω.
5. according to the said giant magnetoresistance effect current sensor of claim 1, it is characterized in that: the constituted mode of described giant magnetoresistance chip power supply voltage conversion circuit is: the input end Vin of voltage stabilizer VR7805 meets giant magnetoresistance current sensor system supplying DC electricity power supply+15V, the filter capacitor C1 of 0.33uF is connected in parallel between the input end Vin of voltage stabilizer VR7805 and the earth terminal of voltage stabilizer VR7805, the output end vo ut stable output of voltage stabilizer VR7805+direct current of 5V voltage, the filter capacitor C2 of 0.1uF is connected in parallel between the output end vo ut of voltage stabilizer VR7805 and the earth terminal of voltage stabilizer VR7805, the output voltage of Vout pin is stable 5V direct current thus.
6. according to the said giant magnetoresistance effect current sensor of claim 1, it is characterized in that: the constituted mode of described generating circuit from reference voltage is: operational amplifier U1A and resistance R 1 and R2 and R3 form anti-phase input scale operation circuit, the normal phase input end of one termination U1A of resistance R 1, the other end ground connection of resistance R 1, the inverting input of one termination U1A of resistance R 2, the voltage source of another termination direct current 5V of resistance R 2, inverting input and the output terminal of U1A received respectively at resistance R 3 two ends, the supply voltage of U1A is+15V and-15V; The output terminal of U1A is received the normal phase input end of U1B, the inverting input of U1B and the output terminal formation voltage follower that connects together, the model of operational amplifier U1A and operational amplifier U1B is LF353, above-mentioned resistance R 1 resistance is 8.2k Ω, resistance R 2 resistances are 3.6k Ω, and resistance R 3 resistances are 10k Ω.
7. according to the said giant magnetoresistance effect current sensor of claim 1, it is characterized in that: the formation of described modified calculus of differences amplifying circuit is: the inverting input of a termination operational amplifier A 1 of resistance R 4, the output terminal of another termination operational amplifier A 2 of resistance R 4, the inverting input of one termination operational amplifier A 2 of resistance R 5, the output terminal of another termination operational amplifier A 1 of resistance R 5, the positive input terminal of operational amplifier A 2 is connected to the output terminal of operational amplifier A 1, inverting input and the output terminal of operational amplifier A 2 received respectively at the two ends of resistance R 6, one termination voltage U 1 of resistance R 1, the inverting input of another termination operational amplifier A 1 of resistance R 1, one termination voltage U 2 of resistance R 2, the normal phase input end of another termination operational amplifier A 1 of resistance R 2, the normal phase input end of one termination operational amplifier A 1 of resistance R 3, the other end ground connection of resistance R 3, the model of operational amplifier A 1 and operational amplifier A 2 is LF356, above-mentioned resistance R 1 resistance is 27k Ω, resistance R 2 resistances are 27k Ω, resistance R 3 resistances are 270k Ω, resistance R 4 resistances are 270k Ω, resistance R 5 resistances are 1k Ω, resistance R 6 resistances are 10k Ω.
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