CN116500530B - Frequency band calibration method and calibration system of broadband current measurement device - Google Patents
Frequency band calibration method and calibration system of broadband current measurement device Download PDFInfo
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Abstract
The invention belongs to the technical field of measuring electric variables, and discloses a frequency band calibration method and a frequency band calibration system of a broadband current measuring device, wherein the method comprises the following steps: a Hall sensing unit; TMR sensing unit, low frequency path buffer unit, high frequency path buffer unit, addition unit includes: at least one addition operational amplifier; two third resistors, two fourth resistors, two fifth resistors; the frequency band calibration method comprises the following steps: cutting off the input or output of the TMR sensing unit, loading a current in the conductor, trimming the resistance value of the third resistor to obtain a determined output vout1; cutting off the input or output of the Hall sensing unit, loading a high-frequency current in the conductor, trimming the resistance value of the fourth resistor to obtain the determined vout2, wherein vout1 = vout2, obtaining the high-frequency sensitivity equal to the high-frequency sensitivity, and completing the frequency band calibration of the broadband current measuring device. The invention can realize real broadband detection and solve the problem that the low-frequency signal and the high-frequency signal exist simultaneously in practical application.
Description
Technical Field
The present invention relates to the field of current sensors, and in particular, to a method and a system for calibrating a broadband current measurement device.
Background
There are a variety of detection modes currently in use in current sensors, including but not limited to current transformers, rogowski coils, magnetoresistive sensors, and the like. Various detection modes have advantages and disadvantages, wherein the magneto-resistive sensor gradually becomes an important detection mode because of the advantages of non-contact measurement, electromagnetic interference resistance, high stability, simple packaging and the like. Magnetoresistive sensors include various forms such as Hall, AMR, GMR, TMR, some of which are suitable for low frequency detection and others of which are relatively good at high frequency detection, depending on their respective characteristics.
In many practical current detection applications, a wide frequency band needs to be processed, and in order to expand the frequency band, there is a technology of optimizing a single type of sensor, for example CN115362374, but this technology is limited by the characteristics of the sensor itself, and cannot fundamentally solve the problem; for example, a Hall sensor has a relatively large Offset (Offset) at a low frequency end, and needs to be eliminated by a chopping technology, but the Offset at a low frequency is shifted to a high frequency by using the chopping technology and needs to be restrained by a filter, which naturally limits the application of the Hall sensor at a high frequency side, and the Hall sensor at a high frequency band has the problem of eddy current, generates relatively large loss, and is suitable for low-frequency and high-precision application in combination;
there are also ways of detecting low frequencies using rogowski coils in combination with other low frequency techniques, such as: US6366076B1, however, the rogowski coil has a size above 10mm, is easy to generate space interference, is not easy to integrate, and because the rogowski coil has an inductance characteristic, a high-frequency filtering point of the rogowski coil is related to an inductance L, and a low-frequency filtering point of other low-frequency sensors is generally related to a capacitance C no matter what filter is adopted, at a low-frequency and high-frequency switching position, because the physical characteristics of the inductance L and the capacitance C of a passive device are inconsistent, a problem of distortion of a frequency response curve is easy to occur in practical application;
there are also ways of using a plurality of magnetic sensors in series, for example: CN113227813 dynamically selects a magnetic sensor by using a frequency band to realize detection with a higher bandwidth, but this mode can only be used in a low frequency band or a high frequency band alone, and cannot realize real detection and calibration of a wide frequency band, and cannot solve the problem that low frequency signals and high frequency signals exist simultaneously in practical application.
Therefore, there is a need for a method and a system for calibrating a broadband current measurement device that can achieve a truly broadband calibration.
Disclosure of Invention
The invention aims to provide a frequency band calibration method and a calibration system of a broadband current measurement device, which can realize real broadband calibration.
In order to achieve the above purpose, the technical scheme provided by the invention is as follows:
in a first aspect, the present invention provides a method for calibrating a broadband current measurement device, wherein the broadband current measurement device is configured to measure a magnitude of a current flowing through a conductor based on a Hall sensor and a TMR sensor, and the broadband current measurement device includes:
a Hall sensing unit for measuring a low frequency part of the magnitude of a current flowing through the conductor and outputting a low frequency measurement signal vin1;
a TMR sensing unit for measuring a high frequency portion of a magnitude of a current flowing through the conductor and outputting a high frequency measurement signal vin2;
the low-frequency path buffer unit is used for carrying out low-pass filtering on the low-frequency measurement signal vin1 and outputting a low-pass filtering signal;
the high-frequency channel buffer unit is used for carrying out high-pass filtering on the high-frequency measurement signal vin2 and outputting a high-pass filtering signal;
the adding unit is used for superposing the low-pass filtering signal and the high-pass filtering signal and outputting vout;
the addition unit includes:
the addition operational amplifier is provided with two input ends and two output ends;
two third resistors, two fourth resistors, two fifth resistors;
the two output ends of the low-frequency path operational amplifier are respectively connected to the two input ends of the addition operational amplifier, and a third resistor is respectively arranged between the two output ends of the low-frequency path operational amplifier and the two input ends of the addition operational amplifier;
the two output ends of the high-frequency channel operational amplifier are respectively connected to the two input ends of the addition operational amplifier, and a fourth resistor is respectively arranged between the two output ends of the high-frequency channel operational amplifier and the two input ends of the addition operational amplifier;
a fifth resistor is bridged between each group of input ends and output ends of the addition operational amplifier;
the frequency band calibration method comprises the following steps:
cutting off the input or output of the TMR sensing unit, loading a current in the conductor, trimming the resistance value of the third resistor to obtain a determined output vout1, and obtaining low-frequency sensitivity Sen_low=vout 1/B;
cutting off the input or output of the Hall sensing unit, loading a high-frequency current in the conductor, trimming the resistance value of the fourth resistor R4 to obtain a determined output vout2, and obtaining high-frequency sensitivity sen_high=vout 2/B;
let vout 1=vout 2, obtain sen_low=sen_high, and complete the band calibration of the broadband current measurement device.
The low-frequency current is direct current, and the magnitude of the low-frequency current is equal to that of the high-frequency current.
The switching off of the input or output of the TMR sensor cell, in particular, the switching off of the output of the TMR sensor cell, i.e. the grounding of the high frequency measurement signal vin2.
The input or output of the Hall sensor unit is switched off, in particular the output of the Hall sensor unit is switched off, i.e. the low frequency measurement signal vin1 is grounded.
The low frequency path buffer unit includes:
at least one low frequency path operational amplifier, the low frequency path operational amplifier having two input ends and two output ends;
two first resistors and two first capacitors;
the Hall sensing unit comprises two output ends, the two output ends are respectively connected with two input ends of the low-frequency channel operational amplifier, a first resistor is respectively arranged between the two output ends of the Hall sensing unit and the two input ends of the low-frequency channel operational amplifier, each input end of the low-frequency channel operational amplifier is also respectively connected with a first capacitor, and the other ends of the two first capacitors are grounded;
the high-frequency path buffer unit includes:
at least one high frequency channel operational amplifier, the high frequency channel operational amplifier having two input ends and two output ends;
two second resistors and two second capacitors;
the TMR sensing unit comprises two output ends, the two output ends are respectively connected with the two input ends of the high-frequency channel operational amplifier, a second resistor is respectively arranged between the two output ends of the TMR sensing unit and the two input ends of the high-frequency channel operational amplifier, each input end of the high-frequency channel operational amplifier is also respectively connected with one of the second capacitors, and the other ends of the two second capacitors are grounded.
The method for low-pass filtering the low-frequency measurement signal vin1 and outputting a low-pass filtered signal includes:
acquiring a low-pass filtering frequency point of the low-frequency channel buffer unit, performing low-pass filtering on vin1 at the low-pass filtering frequency point through the low-frequency channel buffer unit, and outputting a low-pass filtering signal;
obtaining the low-frequency gain of vin1 passing through the low-frequency path buffer unit and the addition unit;
the method for high-pass filtering the high-frequency measurement signal vin2 and outputting a high-pass filtered signal includes:
acquiring a high-pass filtering frequency point of the high-frequency channel buffer unit, performing high-pass filtering on vin2 at the high-pass filtering frequency point through the high-frequency channel buffer unit, and outputting a high-pass filtering signal;
obtaining the high-frequency gain of vin2 passing through the high-frequency channel buffer unit and the addition unit;
wherein the low-pass filtering frequency points and the high-pass filtering frequency points are mutually offset;
wherein the low frequency gain is the same as the high frequency gain.
The output of the low frequency measurement signal vin1 specifically comprises the steps of placing the Hall sensor in a magnetic field generated by the conductor, loading a bias voltage Vb1 and establishing an output function of vin 1:
vin1= Vb1*Sen1*B
wherein Sen1 is the sensitivity of the Hall sensor and B is the spatial magnetic field generated by the conductor.
The output of high frequency measurement signal vin2 specifically includes placing the TMR sensor in a magnetic field generated by the conductor, loading bias voltage Vb2 and establishing an output function of vin 2:
vin2= Vb2*Sen2*B
wherein Sen2 is the sensitivity of the TMR sensor, and B is the spatial magnetic field generated by the conductor.
The obtaining the low-frequency gain of vin1 through the low-frequency path buffer unit and the addition unit specifically includes:
establishing a transfer function Hlp(s) of vin1 to vout 1:
Hlp(s)=(R5/R3)*Ha1(s)/(1+sR1*C1)
filter frequency point: fp1=1/(2 pi×r1×c1)
Wherein Ha 1(s) is a transfer function of the low-frequency path buffer unit, s is a Laplacian operator, and pi is a circumference rate;
when the input or output of the TMR sensing unit is cut off:
Vout1=Hlp(s)*vin1
wherein R1, R3, R5 and C1 are respectively a first resistor, a third resistor and a fifth resistor, and a first capacitor.
The obtaining the high-frequency gain of vin2 through the high-frequency path buffer unit and the adding unit specifically includes:
establishing a transfer function Hhp(s) of vin2 to vout 2:
Hhp(s)=(R5/R4) *Ha2(s)*sR2*C2/(1+sR2*C2)
filter frequency point: fp2=1/(2×pi×r2×c2)
When the input or output of the Hall sensor unit is cut off:
Vout2= Hhp(s)*vin2
let r1=c1=r2=c2=r×c, and the low-pass filtered frequency point and the high-pass filtered frequency point cancel each other;
let Vb1×sen1×r 5/R3) =vb2×sen2×r5/R4, the low-frequency gain and the high-frequency gain are equal;
wherein Ha 2(s) is a transfer function of the high-frequency path buffer unit, s is a Laplacian operator, and pi is a circumference ratio;
wherein R1, R2, R3, R4, R5, C1 and C2 are respectively a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor, a first capacitor and a second capacitor.
In a second aspect, the present invention provides a frequency band calibration system of a broadband current measurement device, the frequency band calibration system comprising at least one processor, a storage medium, the at least one processor being connected to the storage medium; the storage medium is used for storing a program, and the processor is used for executing the program, and the program, when executed by the at least one processor, causes the at least one processor to execute the frequency band calibration method of the broadband current measurement device.
Compared with the prior art, the broadband current measurement method, device, system and chip have the following beneficial effects:
1. the Hall sensor has low-frequency characteristics from the current I to the output vout transfer function Hlp, the TMR sensor has high-frequency characteristics from the current I to the output vout transfer function Hhp, real broadband detection and calibration can be realized, and the problem that low-frequency signals and high-frequency signals exist simultaneously in practical application is solved;
2. by matching the low-frequency gain and the high-frequency gain, broadband consistent gain response can be realized, the frequency response curve of the transfer function from the current I to the output vout can be free from distortion, the high-frequency limit of the Hall sensor and the low-frequency limit of the TMR sensor can be avoided, and the application frequency band of the sensor is expanded.
The invention will become more apparent from the following description taken in conjunction with the accompanying drawings which illustrate embodiments of the invention.
Drawings
Fig. 1 is a block diagram of a broadband current measurement device.
Fig. 2 shows a schematic diagram of a Hall sensor and a TMR sensor in a magnetic field.
Fig. 3 is a schematic circuit diagram of an embodiment of a broadband current measurement device.
FIG. 4 is a flow chart of a method for calibrating a broadband current measuring device according to the present invention.
Fig. 5 is a schematic diagram showing abstractions of Hall sensor and TMR sensor frequency response curves.
Fig. 6 shows a spectral characteristic of an ideal first-order low-pass filter.
Fig. 7 shows a spectral characteristic diagram of an ideal first-order high-pass filter.
Fig. 8 is a diagram showing the spectral characteristics of an ideal first-order low-pass filter and an ideal first-order high-pass filter after addition.
Fig. 9 is a diagram showing the spectral characteristics of the first order low pass filter when the resistor and capacitor are mismatched.
Fig. 10 is a graph showing the spectral characteristics of a first order high pass filter when the resistor and capacitor are mismatched.
Fig. 11 is a diagram showing spectral characteristics of the first-order low-pass filter and the first-order high-pass filter shown in fig. 9 and 10 after addition.
Fig. 12 is a flowchart showing the low-pass filtering of vin1 by the low-frequency path buffer unit.
Fig. 13 is a flowchart showing the low-pass filtering of vin2 by the high-frequency path buffer unit.
Fig. 14 is a schematic diagram of a band calibration system of the broadband current measurement device according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.
The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present invention.
In the following, the terms "comprises", "comprising", "having" and their cognate terms as used in various embodiments of the invention are intended to refer only to a particular feature, number, step, operation, element, component, or combination of the foregoing, and should not be taken to first exclude the presence of or increase the likelihood of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.
Furthermore, the terms "first," "second," "third," and the like, as used herein, are used merely for distinguishing between descriptions and not for indicating or implying a relative importance.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of the invention belong. The terms (such as those defined in commonly used dictionaries) will be interpreted as having a meaning that is the same as the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein in connection with the various embodiments of the invention.
The invention solves the difficult problem of broadband detection based on the advantages of simple and easy integration of reluctance packaging and strong anti-interference capability by selecting and combining two reluctance sensors suitable for low-frequency and high-frequency detection. For example, hall sensors (Hall) are easy to integrate with semiconductor technology, but because the offset (offset) is relatively large, the offset is eliminated by using a rotating current mode in the current application, but the application bandwidth of the Hall sensors is limited, so that the Hall sensors are suitable for low-frequency detection application; although the tunnel magneto-resistance sensor (TMR) cannot be fully compatible and integrated with a semiconductor process, the TMR is generally smaller than 1mm in size, is easy to package with a signal processing chip, has larger signal and high response speed, but is relatively large in low-frequency noise due to the problem of a manufacturing process and is relatively suitable for high-frequency detection application. The invention takes the combination of the two magnetic resistance sensors as an example, and solves the problem of wide-band application.
Referring to fig. 1, in one embodiment, a method for calibrating a broadband current measurement device, wherein the broadband current measurement device measures a magnitude of a current flowing through a conductor based on a Hall sensor and a TMR sensor, the broadband current measurement device includes:
a Hall sensing unit 40 for measuring a low frequency portion of the magnitude of a current flowing through the conductor and outputting a low frequency measurement signal vin1;
a TMR sensing unit 41 for measuring a high frequency portion of the magnitude of a current flowing through the conductor and outputting a high frequency measurement signal vin2;
a low frequency path buffer unit 50 for low-pass filtering the low frequency measurement signal vin1 and outputting a low-pass filtered signal;
a high-frequency path buffer unit 51 for performing high-pass filtering on the high-frequency measurement signal vin2 and outputting a high-pass filtered signal;
an adding unit 60, configured to superimpose the low-pass filtered signal and the high-pass filtered signal, and output vout;
referring to fig. 3, the adding unit 60 includes:
the addition operational amplifier is provided with two input ends and two output ends;
two third resistors R3, two fourth resistors R4, two fifth resistors R5;
the two output ends of the low-frequency channel operational amplifier Ha1 are respectively connected to the two input ends of the addition operational amplifier, and a third resistor R3 is respectively arranged between the two output ends of the low-frequency channel operational amplifier Ha1 and the two input ends of the addition operational amplifier;
the two output ends of the high-frequency channel operational amplifier Ha2 are respectively connected to the two input ends of the addition operational amplifier, and a fourth resistor R4 is respectively arranged between the two output ends of the high-frequency channel operational amplifier and the two input ends of the addition operational amplifier;
the fifth resistor R5 is connected between each group of input ends and output ends of the addition operational amplifier in a bridging way;
referring to fig. 4, fig. 4 is a flowchart illustrating a method for calibrating a frequency band of the broadband current measurement apparatus according to the present invention, the method for calibrating the frequency band includes:
s110, cutting off the input or output of the TMR sensing unit, loading a current I1 in the conductor, trimming the resistance value of the third resistor R3 to obtain a determined output vout1, and obtaining a low-frequency sensitivity Sen_low=vout 1/B;
s120 cuts off the input or output of the Hall sensing unit, loads a high-frequency current I2 in the conductor, adjusts the resistance value of the fourth resistor R4 to obtain a determined output vout2, obtains high-frequency sensitivity Sen_high=vout 2/B, enables vout 1=vout 2 to obtain Sen_low=Sen_high, and completes the frequency band calibration of the broadband current measuring device.
It should be noted that references to vout, vout1, and vout2 herein refer to signals output from the adding unit 60, wherein in all embodiments herein, the output of the adding unit 60 is denoted as vout for convenience of distinction, the output of the adding unit 60 is denoted as vout1 when the input or output of the TMR sensing unit is cut off, and the output of the adding unit 60 is denoted as vout2 when the input or output of the Hall sensing unit is cut off.
In one embodiment, in the step S110, the current I1 is dc, in the step S120, the current I2 is ac, and the magnitude of the current I1 is equal to the magnitude of the current I2.
Referring to fig. 1 and 3, the Hall sensor unit 40 and the low-frequency path buffer unit 50 form a low-frequency measurement path of the broadband current measurement device, the TMR sensor unit 41 and the high-frequency path buffer unit 51 form a high-frequency measurement path of the broadband current measurement device, and the adding unit 60 performs addition operation on the low-frequency measurement path and the high-frequency measurement path.
Referring to fig. 5, fig. 5 is a schematic diagram showing abstractions of Hall sensor and TMR sensor frequency response curves. As shown in fig. 5, the Hall sensor has a low frequency characteristic from the current I to the output vout transfer function Hlp; TMR sensor transfer function Hhp from current I to output vout, has high frequency characteristics (ignoring the low pass characteristics of the actual circuit at very high frequencies, such as Ha(s) bandwidth limitations); by matching the low frequency gain of Hlp and the high frequency gain of Hhp, that is, ensuring that the response to the low frequency current and the response to the high frequency current have the same amplification factor, that is, a broadband-identical gain response, by matching the frequency point fp1 of Hlp and the frequency point fp2 of Hhp, that is, fp1=fp2, it is possible to realize that the transfer function Hs from the current I to the output vout is not distorted at the frequency point. Thus, the current I1 and the current I2 are equal in magnitude, so that matching between the low-frequency gain of Hlp and the high-frequency gain of Hhp is easier to achieve. Therefore, the conditions described above are satisfied, i.e., the limitation of the Hall sensor (high frequency limitation) and the TMR sensor (low frequency limitation) can be avoided, and the sensor application band is expanded.
Referring to fig. 6, fig. 6 shows a spectrum characteristic diagram of an ideal first-order low-pass filter, taking normalized ideal first-order low-pass filter hl=1/(1+s) as an example, it can be seen from the figure that the amplitude is attenuated by-3 decibels (dB) at 1Hz, and the phase is shifted by 45 degrees (deg).
Referring to fig. 7, fig. 7 shows a spectrum characteristic diagram of an ideal first-order high-pass filter, taking normalized ideal first-order high-pass filter hl=1/(1+s) as an example, it can be seen from the figure that the amplitude is attenuated by-3 dB at 1Hz, and the phase is shifted by 45deg.
Referring to fig. 8, a spectrum characteristic diagram of the ideal first-order low-pass filter and the ideal first-order high-pass filter added is shown. The ideal first-order low-pass filter and the first-order high-pass filter are added together, and the final transfer function is hl+hh=1, and as shown in fig. 11, the ideal wideband characteristic is shown, and no distortion is generated at the frequency point.
Referring to fig. 9, a spectral characteristic of a first order low pass filter is shown when the resistor and capacitor are mismatched. In the semiconductor process, the resistor R and the capacitor C may be manufactured with a certain deviation. With the current state of the art, the mismatch rate of the resistor R and the capacitor C is relatively easy to control within 10%, and here, the mismatch rate of 10% is taken as an example to describe the distortion condition at the frequency point caused by the mismatch of the resistor R and the capacitor C which determine the filter frequency point. Assuming that the normalized ideal first-order low-pass filter is still hl=1/(1+s), its amplitude-frequency characteristic is as shown in fig. 6: the amplitude attenuation is-3 dB at 1Hz, phase shift 45deg.
Referring to fig. 10, fig. 10 is a graph showing the spectral characteristics of a first order high pass filter when the resistors and capacitors are mismatched.
Since in the embodiment shown in fig. 9, the mismatch ratio between the resistor R and the capacitor C is assumed to be 10%, that is, the normalized first-order high-pass filter is hh=0.9×s/(0.9×s+1), and the amplitude-frequency characteristic is as shown in fig. 10: the amplitude attenuation at 1Hz is-3.49 dB (shown with specific reference to the rectangular small black dot A1 of FIG. 10), and the phase shift is 47.8deg (shown with specific reference to the rectangular small black dot A2 below FIG. 10).
Fig. 11 is a diagram showing spectral characteristics of the first-order low-pass filter and the first-order high-pass filter shown in fig. 9 and 10 after addition. Referring to fig. 11, the amplitude-frequency characteristics are: amplitude attenuation at 1 Hz-0.468 dB (shown with particular reference to the upper rectangular small black dot A3 of fig. 11), phase shift-1.53 deg (shown with particular reference to the lower rectangular small black dot A4 of fig. 11).
The low pass filter shown in fig. 9 and the high pass filter shown in fig. 10 are added together, and the final transfer function is hl+hh= (0.9 x s 2+1.8 x s + 1)/(0.9 x s 2+1.9 x s + 1), and as shown in fig. 11, an amplitude change of approximately 0.5dB occurs at 1Hz, and the maximum phase change is 1.5deg, that is, the degree of distortion can satisfy most practical applications even if the mismatch ratio between the resistor R and the capacitor C is within 10%.
In summary, in practical application, since the characteristics of the Hall sensor and the TMR sensor are different, if the sensitivity Sen1 of the Hall sensor and the sensitivity Sen2 of the TMR sensor are different, the bias voltage Vb1 of the Hall sensor and the Vb2 of the TMR sensor are different, the operational amplifier transfer function Ha1 of the low frequency channel and the operational amplifier transfer function Ha2 of the high frequency channel are also different, so as to meet the problem that in practical application, it is required that the low frequency gain and the high frequency gain are consistent, a solution is proposed:
in the adding unit 60, by setting the adjustable third resistor R3 and the fourth resistor R4, the gain of R5/R3 and Vb1×sen1×ha1 are compensated by calibrating and adjusting, and the gain of R5/R4 and Vb2×sen2×ha2 are compensated by calibrating and adjusting, so as to realize that Vb1×sen1 (R5/R3) =vb 2×sen2 (R5/R4).
Therefore, for the combination of the low-frequency sensor and the high-frequency sensor to form a circuit with wide frequency band application, a step-by-step calibration method is proposed to realize the full-frequency band calibration.
It should be noted that, in the low frequency measurement path, R5/R3 is a transfer function of the summing unit 60, and Vb1×sen1×ha1 is a transfer function of the Hall sensing unit 40 and the low frequency path buffer unit 50;
in the high frequency measurement path, R5/R4 is the transfer function of the adder unit 60, and Vb2 x Sen2 x Ha2 is the transfer function of the high frequency path buffer unit 51.
In an embodiment, the switching off of the input or output of the TMR sensor cell, in particular the switching off of the output of the TMR sensor cell, i.e. the high frequency measurement signal vin2 is grounded.
Specifically, the manner of cutting off the input or output of the TMR sensor cell may be various, for example, may include cutting off the input of Vb2 to cut off the input of the TMR sensor cell, and this embodiment gives the effect of grounding the high-frequency measurement signal vin2 to achieve the effect of cutting off the output of the TMR sensor cell.
In one embodiment, the switching off of the input or output of the Hall sensor unit, in particular the switching off of the output of the Hall sensor unit, i.e. the grounding of the low frequency measurement signal vin 1.
Specifically, the input or output of the Hall sensor unit may be cut off in various manners, for example, the input of Vbi may be cut off, so as to cut off the input of the Hall sensor unit, and this embodiment gives an effect of grounding the high-frequency measurement signal vin1 to achieve the output of the Hall sensor unit.
Referring to fig. 3, vb1 is the bias voltage of Hall sensor cell 40, vb2 is the bias voltage of TMR sensor cell 41, and I is the magnitude of the current through the conductor.
Referring to fig. 1, in one embodiment, the Hall sensor unit 40 and the TMR sensor unit 41 detect vertical and parallel magnetic fields, respectively, and the Hall sensor unit 40 and the TMR sensor unit 41 can sense a current magnetic field at the same time by means of a vertical package.
Since the Hall sensor unit 40 is mainly used for measuring the low-frequency part of the magnitude of the current flowing through the conductor, a low-frequency measurement signal vin1 is output under the action of the bias voltage Vb 1;
since TMR sensing unit 41 is mainly used for measuring the high frequency portion of the magnitude of the current flowing through the conductor, high frequency measurement signal vin2 is outputted under the action of bias voltage Vb 2.
Note that, in the low-frequency path buffer unit 50 and the high-frequency path buffer unit 51, the low-frequency path buffer unit may be various low-frequency path buffer circuits known to those skilled in the art, and each of the low-frequency path buffer circuits may be capable of low-pass filtering the low-frequency measurement signal vin1 and outputting a low-pass filtered signal; the high-frequency path buffer unit may be various high-frequency path buffer circuits known to those skilled in the art, and is capable of performing high-pass filtering on the high-frequency measurement signal vin2 and outputting a high-pass filtered signal, which is not particularly limited herein.
Referring to fig. 3, the low-frequency measurement signal vin1 output by the hall sensing unit 40 is low-pass filtered by the low-frequency path buffer unit 50, and then outputs a low-pass filtered signal, the high-frequency measurement signal vin2 output by the TMR sensing unit 41 is high-pass filtered by the high-frequency path buffer unit 51, and then outputs a high-pass filtered signal, and in the adding unit 60, the low-pass filtered signal and the high-pass filtered signal respectively obtained by the low-frequency path buffer unit 50 and the high-frequency path buffer unit 51 are superimposed by the adding unit 60, and then output a superimposed signal vout, which is a signal capable of simultaneously having a low frequency band or a high frequency band, so that a real wide-band measurement can be realized, and the problem existing in practical application of both low frequency and high frequency can be solved.
The internal structure and operation principle of the low frequency path buffer unit 50 may refer to fig. 3, and a schematic circuit diagram of the low frequency path buffer unit 50 includes:
at least one low-frequency channel operational amplifier Ha1, wherein the low-frequency channel operational amplifier Ha1 is provided with two input ends and two output ends;
two first resistors R1 and two first capacitors C1;
the Hall sensor 10 comprises two output ends, the two output ends are respectively connected with two input ends of the low-frequency path operational amplifier, a resistor R1 is respectively arranged between the two output ends of the Hall sensor 10 and the two input ends of the low-frequency path operational amplifier, each input end of the low-frequency path operational amplifier is also respectively connected with a first capacitor C1, and the other end of the first capacitor C1 is grounded;
the internal structure and operation principle of the high-frequency path buffer unit 51 may also refer to fig. 3, and a schematic diagram of the high-frequency path buffer unit 51 includes:
at least one high-frequency channel operational amplifier Ha2, wherein the high-frequency channel operational amplifier Ha2 is provided with two input ends and two output ends;
two second resistors R2 and two second capacitors C2;
the TMR sensor 11 includes two output ends, and is connected to the two input ends of the high-frequency path operational amplifier, and a second resistor R2 is respectively disposed between the two output ends of the TMR sensor 11 and the two input ends of the high-frequency path operational amplifier, each input end of the high-frequency path operational amplifier is further connected to a second capacitor C2, and the other end of the second capacitor C2 is grounded.
In one embodiment, referring to fig. 3 and 12, fig. 12 is a flowchart of low-pass filtering of vin1 by the low-frequency path buffer unit, where the low-pass filtering of vin1 by the low-frequency path buffer unit 50 and outputting a low-pass filtered signal includes:
s210, obtaining a low-pass filter frequency point of the low-frequency channel buffer unit 50, performing low-pass filtering on vin1 at the low-pass filter frequency point through the low-frequency channel buffer unit 50, and outputting a low-pass filtering signal;
s220, obtaining the low-frequency gain of vin1 passing through the low-frequency path buffer unit 50 and the addition unit 60;
in this embodiment, the low-pass filtering frequency point of the low-frequency path buffer unit 50 is obtained by determining the size of the low-pass filtering frequency point through a specific circuit design of the low-frequency path buffer unit 50;
in this embodiment, the low frequency gain of vin1 passing through the low frequency path buffer unit 50 and the adding unit 60 is obtained, and mainly depends on the magnitude of the bias voltage Vb1 of the Hall sensor unit 40, the sensitivity Sen1 of the Hall sensor unit 40, and the specific circuit design of the adding unit 60 with reference to fig. 1.
Referring to fig. 3 and 13, the method for high-pass filtering vin2 by the high-frequency path buffer unit 51 and outputting a high-pass filtered signal includes:
s310, obtaining a high-pass filter frequency point of the high-frequency channel buffer unit 51, performing high-pass filtering on vin2 at the high-pass filter frequency point through the high-frequency channel buffer unit 51, and outputting a high-pass filtering signal;
s320, obtaining the high-frequency gain of vin2 through the high-frequency path buffer unit 51 and the addition unit 60;
in this embodiment, the high-pass filtering frequency point of the high-frequency path buffer unit 51 is obtained by determining the size of the high-pass filtering frequency point through a specific circuit design of the high-frequency path buffer unit 51;
in this embodiment, the high frequency gain of vin2 passing through the high frequency path buffer unit 51 and the adding unit 60 is obtained, and the magnitude of the high frequency gain is determined mainly by referring to fig. 1 depending on the magnitude of the bias voltage Vb2 of the TMR sensor unit 41, the sensitivity Sen2 of the TMR sensor unit 41, and the specific circuit design of the adding unit 60.
Wherein the low-pass filtering frequency points and the high-pass filtering frequency points are mutually offset; if the low-pass filter frequency point of vin1 passing through the low-frequency path buffer unit 50 and the high-pass filter frequency point of vin2 passing through the high-frequency path buffer unit 41 are mutually offset, the signal can be ensured not to distort the frequency response curve in a wide frequency band;
wherein the low frequency gain is the same as the high frequency gain, so that a consistent gain correspondence with low frequency and high frequency bands can be achieved.
The outputting of the low frequency measurement signal vin1 of the Hall sensor unit 40 specifically includes placing the Hall sensor unit 40 in a magnetic field generated by the conductor, loading a bias voltage Vb1 and establishing an output function of vin 1:
vin1= Vb1*Sen1*B
wherein, vb1 is the bias voltage of the Hall sensing unit 40, sen1 is the sensitivity of the Hall sensing unit 40, and B is the space magnetic field generated by the conductor;
the outputting of the high frequency measurement signal vin2 of the TMR sensing unit 41 specifically includes placing the TMR sensing unit 41 in a magnetic field generated by the conductor, loading a bias voltage Vb2 and establishing an output function of vin 2:
vin2= Vb2*Sen2*B
where Vb2 is the bias voltage of TMR sensor cell 41, sen2 is the sensitivity of TMR sensor cell 41.
Note that, the sensitivity Sen1 of the Hall sensor unit 40 is constant, the magnitude of B depends on the magnitude of the current passing through the conductor and the position of the Hall sensor unit 40, and similarly, the sensitivity Sen2 of the TMR sensor unit 41 is also constant, and the magnitude of B depends on the magnitude of the current passing through the conductor and the position of the TMR sensor unit 41.
The obtaining the low-frequency gain of vin1 through the low-frequency path buffer unit 50 and the adding unit specifically includes:
establishing a transfer function Hlp(s) of vin1 to vout 1:
Hlp(s)=(R5/R3)*Ha1(s)/(1+sR1*C1)
filter frequency point: fp1=1/(2 pi×r1×c1)
Where Ha 1(s) is the transfer function of the low frequency path buffer unit 50, s is the laplace operator, pi is the circumference ratio;
when the input or output of the TMR sensing unit is cut off:
Vout1=Hlp(s)*vin1
wherein R1, R3, R5 and C1 are respectively a first resistor, a third resistor and a fifth resistor, and a first capacitor.
The obtaining the high-frequency gain of vin2 through the high-frequency path buffer unit 50 and the adding unit 60 specifically includes:
establishing a transfer function Hhp(s) of vin2 to vout 2:
Hhp(s)=(R5/R4) *Ha2(s)*sR2*C2/(1+sR2*C2)
filter frequency point: fp2=1/(2×pi×r2×c2)
Wherein Ha 2(s) is a transfer function of the high-frequency path buffer unit, s is a Laplacian operator, and pi is a circumference ratio;
when the input or output of the Hall sensor unit is cut off:
Vout2= Hhp(s)*vin2
in order to more conveniently describe the units of the present invention, such as the low-frequency path buffer unit 50, the high-frequency path buffer unit 51 and the adding unit 60, in particular, in the embodiment shown in fig. 3, the circuit is represented as simply as possible, and other equivalent circuits of the circuit can be obtained without inventive labor, and also belong to the protection scope of the present invention, for example, the low-frequency path buffer unit 50, the high-frequency path buffer unit 51 can be further extended to active, passive, first-order, high-order low-pass filter buffer circuits and high-pass filter buffer circuits formed by the same types of resistors and capacitors; the summing unit 60 should include other summing circuits known to those skilled in the art as applicable to the present invention.
Let r1=c1=r2=c2=r×c, and the low-pass filtered frequency point and the high-pass filtered frequency point cancel each other;
let Vb1×sen1×r 5/R3) =vb2×sen2×r5/R4, the low-frequency gain and the high-frequency gain are equal.
Specifically, the low-pass filtering frequency point and the high-pass filtering frequency point cancel each other, and firstly, an output function of vout is established:
vout=Hlp(s)*vin1+Hhp(s)*vin2
the formulae (1), (2), (3) and (5) show that:
= Vb1*Sen1*I*(R5/R3)*Ha1(s)/(1+sR1*C1)+ Vb2*Sen2*I*(R5/R4) *Ha2(s)*sR2*C2/(1+sR2*C2)
where Vb1 and Vb2 are bias voltages of the Hall sensor unit 40 and the TMR sensor unit 41, sen1 and Sen2 are sensitivities of the Hall sensor unit 40 and the TMR sensor unit 41, and I is a current to be measured;
when the transfer functions of the low frequency path buffer unit 50 and the high frequency path buffer unit 51 are the same, namely:
Ha1(s)= Ha2(s)=Ha（s）
then: vout= (Vb 1×sen1×1 (R5/R3)/(1+sr1×c1) +vb2×sen2×r 5/R4) ×sr2×c2/(1+sr2×c2))×i×ha(s)
From the formula:
when Vb1 x Sen1 x (R5/R3) =vb2 x Sen2 x (R5/R4) =k,
vout=（K/(1+sR1*C1)+ K*sR2*C2/(1+sR2*C2)）*B* Ha（s）
if r1=c1=r2=c2=rc,
then vout=k×b×ha(s)
That is, as long as r1=c1=r2=c2=r×c can be satisfied, the filtered frequency point of the low-frequency path buffer unit 50 and the filtered frequency point of the high-frequency path buffer unit 51 can be ensured to cancel each other, and the signal is ensured not to distort the frequency response curve in a wide frequency band; as long as the ratio of Vb1 x Sen1 (R5/R3) =vb2 x Sen2 (R5/R4) can be satisfied, the low-frequency gain and the high-frequency gain are equal, so that the signal has consistent gain response in a wide frequency band; the vout can be made immune to the frequency response of the hall sensor cell and the TMR sensor cell itself.
Compared with the patent US6366076B1, hall and TMR which are all magneto-resistance type sensors, the sensor has the same advantages of easy packaging and strong anti-interference capability; 2. the same type of sensor is used, and the complementary low-high pass filter is used for realizing frequency point compensation, so that the low-frequency to high-frequency switching is relatively flat, and the real broadband application is realized; 3. the problem that the low-frequency gain and the high-frequency gain are consistent is solved by trimming the resistance values of the third resistor R3 and the fourth resistor R4, the gain response with the consistent broadband is realized, the calibration of the application circuit of the broadband sensor is completed, and the low-frequency output and the high-frequency output can be simultaneously output to truly realize the broadband output.
Referring to fig. 14, the embodiment of the present invention further provides a band calibration system 200 of a broadband current measurement device, where the band calibration system 200 includes at least one processor 201 and a storage medium 202, and the at least one processor 201 is connected to the storage medium 202; the storage medium 202 is configured to store a program 203, the processor 201 is configured to execute the program 203, and the program 203, when executed by the at least one processor 201, causes the at least one processor 201 to perform the method for calibrating a frequency band of the broadband current measurement device.
The foregoing description of the preferred embodiments of the present invention is not intended to limit the scope of the claims, which follow, as defined in the claims.
Claims (13)
1. A method for calibrating a broadband current measurement device for measuring the magnitude of a current flowing through a conductor based on a Hall sensor and a TMR sensor, the broadband current measurement device comprising:
a Hall sensing unit for measuring a low frequency part of the magnitude of a current flowing through the conductor and outputting a low frequency measurement signal vin1;
a TMR sensing unit for measuring a high frequency portion of a magnitude of a current flowing through the conductor and outputting a high frequency measurement signal vin2;
the low-frequency path buffer unit is used for carrying out low-pass filtering on the low-frequency measurement signal vin1 and outputting a low-pass filtering signal;
the high-frequency channel buffer unit is used for carrying out high-pass filtering on the high-frequency measurement signal vin2 and outputting a high-pass filtering signal;
the adding unit is used for superposing the low-pass filtering signal and the high-pass filtering signal and outputting vout;
the addition unit includes:
the addition operational amplifier is provided with two input ends and two output ends;
two third resistors, two fourth resistors, two fifth resistors;
the two output ends of the low-frequency path buffer unit are respectively connected to the two input ends of the addition operational amplifier, and a third resistor is respectively arranged between the two output ends of the low-frequency path buffer unit and the two input ends of the addition operational amplifier;
the two output ends of the high-frequency channel buffer unit are respectively connected to the two input ends of the addition operational amplifier, and a fourth resistor is respectively arranged between the two output ends of the high-frequency channel buffer unit and the two input ends of the addition operational amplifier;
a fifth resistor is bridged between each group of input ends and output ends of the addition operational amplifier;
the frequency band calibration method comprises the following steps:
cutting off the input or output of the TMR sensing unit, loading a low-frequency current into the conductor, trimming the resistance value of the third resistor to obtain a determined output vout1, and obtaining a low-frequency sensitivity Sen_low=vout 1/B;
cutting off the input or output of a Hall sensing unit, loading a high-frequency current in the conductor, trimming the resistance value of the fourth resistor to obtain a determined output vout2, obtaining high-frequency sensitivity sen_high=vout 2/B, enabling vout 1=vout 2 to obtain sen_low=sen_high, and completing the frequency band calibration of the broadband current measuring device;
wherein B is a space magnetic field generated by the conductor.
2. The method of calibrating a broadband current measuring apparatus according to claim 1, wherein the low-frequency current is a direct current, and the magnitude of the low-frequency current is equal to the magnitude of the high-frequency current.
3. The method for calibrating a broadband current measuring apparatus according to claim 1, wherein the switching off the input or output of the TMR sensor cell, in particular, switching off the output of the TMR sensor cell, i.e., grounding the high frequency measurement signal vin2.
4. The method of calibrating a broadband current measuring apparatus according to claim 1, wherein the switching off of the input or output of the Hall sensor unit, in particular the switching off of the output of the Hall sensor unit, i.e. the grounding of the low frequency measurement signal vin 1.
5. The method for calibrating a wideband current measuring apparatus according to claim 1, wherein,
the low frequency path buffer unit includes:
at least one low frequency path operational amplifier, the low frequency path operational amplifier having two input ends and two output ends;
two first resistors and two first capacitors;
the Hall sensing unit comprises two output ends, the two output ends are respectively connected with the two input ends of the low-frequency channel operational amplifier, a first resistor is respectively arranged between the two output ends of the Hall sensing unit and the two input ends of the low-frequency channel operational amplifier, each input end of the low-frequency channel operational amplifier is also respectively connected with a first capacitor, and the other ends of the two first capacitors are grounded.
6. The method for calibrating a wideband current measuring apparatus according to claim 1, wherein,
the high-frequency path buffer unit includes:
at least one high frequency channel operational amplifier, the high frequency channel operational amplifier having two input ends and two output ends;
two second resistors and two second capacitors;
the TMR sensing unit comprises two output ends, the two output ends are respectively connected with the two input ends of the high-frequency channel operational amplifier, a second resistor is respectively arranged between the two output ends of the TMR sensing unit and the two input ends of the high-frequency channel operational amplifier, each input end of the high-frequency channel operational amplifier is also respectively connected with one of the second capacitors, and the other ends of the two second capacitors are grounded.
7. The method for calibrating a wideband current measuring apparatus according to claim 4, wherein,
the method for low-pass filtering the low-frequency measurement signal vin1 and outputting a low-pass filtered signal includes:
acquiring a low-pass filtering frequency point of the low-frequency channel buffer unit, performing low-pass filtering on vin1 at the low-pass filtering frequency point through the low-frequency channel buffer unit, and outputting a low-pass filtering signal;
and obtaining the low-frequency gain of vin1 passing through the low-frequency path buffer unit and the addition unit.
8. The method for calibrating a wideband current measuring apparatus as recited in claim 7, wherein,
the method for high-pass filtering the high-frequency measurement signal vin2 and outputting a high-pass filtered signal includes:
acquiring a high-pass filtering frequency point of the high-frequency channel buffer unit, performing high-pass filtering on vin2 at the high-pass filtering frequency point through the high-frequency channel buffer unit, and outputting a high-pass filtering signal;
obtaining the high-frequency gain of vin2 passing through the high-frequency channel buffer unit and the addition unit;
wherein the low-pass filtering frequency points and the high-pass filtering frequency points are mutually offset;
wherein the low frequency gain is the same as the high frequency gain.
9. The method for calibrating a wideband current measuring apparatus as recited in claim 7, wherein,
the output of the low frequency measurement signal vin1 specifically comprises the steps of placing the Hall sensor in a magnetic field generated by the conductor, loading a bias voltage Vb1 and establishing an output function of vin 1:
vin1＝Vb1*Sen1*B
wherein Sen1 is the sensitivity of the Hall sensor and B is the spatial magnetic field generated by the conductor.
10. The method for calibrating a wideband current measuring apparatus according to claim 8, wherein,
the output of high frequency measurement signal vin2 specifically includes placing the TMR sensor in a magnetic field generated by the conductor, loading bias voltage Vb2 and establishing an output function of vin 2:
vin2＝Vb2*Sen2*B
wherein Sen2 is the sensitivity of the TMR sensor, and B is the spatial magnetic field generated by the conductor.
11. The method for calibrating a wideband current measuring apparatus according to claim 9, wherein,
the obtaining the low-frequency gain of vin1 through the low-frequency path buffer unit and the addition unit specifically includes:
establishing a transfer function Hlp(s) of vin1 to vout 1:
Hlp(s)＝(R5/R3)*Ha1(s)/(1+sR1*C1)
filter frequency point: fp1=1/(2 pi×r1×c1)
Wherein Ha 1(s) is a transfer function of the low-frequency path buffer unit, s is a Laplacian operator, and pi is a circumference rate;
when the input or output of the TMR sensing unit is cut off:
Vout1＝Hlp(s)*vin1
wherein R1, R3, R5 and C1 are respectively a first resistor, a third resistor and a fifth resistor, and a first capacitor.
12. The method for calibrating a wideband current measuring apparatus as recited in claim 10, wherein,
the obtaining the high-frequency gain of vin2 through the high-frequency path buffer unit and the adding unit specifically includes:
establishing a transfer function Hhp(s) of vin2 to vout 2:
Hhp(s)＝(R5/R4)*Ha2(s)*sR2*C2/(1+sR2*C2)
filter frequency point: fp2=1/(2×pi×r2×c2)
When the input or output of the Hall sensor unit is cut off:
Vout2＝Hhp(s)*vin2
let r1=c1=r2=c2=r×c, and the low-pass filtered frequency point and the high-pass filtered frequency point cancel each other;
let Vb1×sen1×r 5/R3) =vb2×sen2×r5/R4, the low-frequency gain and the high-frequency gain are equal;
wherein Ha 2(s) is a transfer function of the high-frequency path buffer unit, s is a Laplacian operator, and pi is a circumference ratio;
wherein R1, R2, R3, R4, R5, C1 and C2 are respectively a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor, a first capacitor and a second capacitor.
13. A frequency band calibration system of a broadband current measurement device, wherein the frequency band calibration system comprises at least one processor and a storage medium, and the at least one processor is connected with the storage medium; the storage medium is for storing a program, the processor is for executing the program, the program when executed by the at least one processor causes the at least one processor to perform the method of band calibration of the broadband current measurement device according to any one of claims 1-12.
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