Fluxgate sensor and detection system

Abstract

The invention relates to a fluxgate sensor and a detection system, the fluxgate sensor comprises a direct current zero flux detection unit, an alternating current zero flux detection unit and a compensation unit, and the direct current zero flux detection unit and the alternating current zero flux detection unit are electrically connected with the compensation unit. Wherein the direct-current zero-flux detection unit is used for generating excitation current through self-oscillation and generating a first output voltage signal according to detected current; the alternating-current zero-flux detection unit is used for generating a second output voltage signal according to the detected current; the compensation unit comprises a secondary side coil and is used for determining secondary side compensation current according to the first output voltage signal and the second output voltage signal, the secondary side compensation current generates a compensation magnetic field when flowing through the secondary side coil, and the compensation magnetic field counteracts a magnetic field generated by the detected current, so that zero magnetic flux of the fluxgate sensor is realized. The detection precision of the fluxgate sensor is improved, and the detection range of the fluxgate sensor is widened.

Description

Technical Field

[0001] This application relates to the field of current sensor application technology, and in particular to a fluxgate sensor and detection system. Background Technology

[0002] Current sensors play a crucial role in key fields such as power electronics, motors, and energy. They are not only widely used in various scenarios but are also core components for the normal and stable operation of modern facilities such as electric vehicles, photovoltaic systems, and charging piles. Meanwhile, the development of ultra-high voltage flexible direct current transmission systems has also spurred the demand for measuring large DC currents in power grids. Therefore, fields such as smart grids and new energy vehicles place higher demands on the real-time performance and accuracy of current monitoring.

[0003] Fluxgate sensors are widely used due to their advantages such as wide measurement range, high resolution, excellent temperature characteristics, fast response speed, and ability to measure both AC and DC current. Therefore, current sensing solutions are particularly urgent and important. The working principle of a fluxgate sensor is based on the easy saturation characteristic of soft magnetic materials. An AC excitation signal periodically drives a magnetic ring to reach magnetic saturation. When an external magnetic field is present, it causes a nonlinear change in the saturated magnetic ring, which modulates the magnetic flux and generates a corresponding induced electromotive force, thereby indirectly measuring the current. Existing fluxgate sensors mainly adopt an open-loop design, which limits their detection accuracy and range, failing to meet the requirements and challenges of high-precision and wide-bandwidth AC / DC current detection technology over a wide measurement range. Summary of the Invention

[0004] Based on this, this application provides a fluxgate sensor and detection system, which improves the detection accuracy of the fluxgate sensor, expands the detection range, and can perform AC / DC detection.

[0005] In a first aspect, embodiments of this application provide a fluxgate sensor, which includes a DC zero flux detection unit, an AC zero flux detection unit, and a compensation unit. The DC zero flux detection unit and the AC zero flux detection unit are electrically connected to the compensation unit, wherein:

[0006] The DC zero flux detection unit is used to generate excitation current through self-excited oscillation and generate a first output voltage signal based on the measured current.

[0007] The AC zero flux detection unit is used to generate a second output voltage signal based on the measured current.

[0008] The compensation unit includes a secondary coil, which is used to determine the secondary compensation current based on the first output voltage signal and the first output voltage signal. When the secondary compensation current flows through the secondary coil, it generates a compensation magnetic field. The compensation magnetic field cancels the magnetic field generated by the measured current, thereby achieving zero magnetic flux of the fluxgate sensor.

[0009] In some embodiments of this application, the fluxgate sensor further includes a first annular magnetic core, a second annular magnetic core, and a third annular magnetic core stacked sequentially along a stacking direction, the stacking direction being opposite to the direction of the current being measured flowing in.

[0010] In some embodiments of this application, the DC zero flux detection unit includes a self-excited oscillation circuit and a first low-pass filter electrically connected to the self-excited oscillation circuit. The self-excited oscillation circuit is used to generate an excitation current through self-excited oscillation.

[0011] In some embodiments of this application, the self-excited oscillation circuit includes an excitation coil, a reverse excitation coil, a driving circuit, a first feedback resistor, a second feedback resistor, a third feedback resistor, a fourth feedback resistor, and an operational amplifier, wherein,

[0012] The drive circuit includes an input terminal and an output terminal;

[0013] The excitation coil is wound on the first toroidal magnetic core. One end of the excitation coil is electrically connected to the output terminal of the drive circuit, and the other end is connected to one end of the reverse excitation coil.

[0014] The reverse excitation coil is wound in the opposite direction on the second toroidal core. One end of the reverse excitation coil is electrically connected to the excitation coil, and the other end is electrically connected to one end of the third feedback resistor.

[0015] The first feedback resistor and the second feedback resistor are connected in series. One end of the first feedback resistor and the second feedback resistor connected in series is electrically connected to the inverting input terminal of the operational amplifier. The end of the first feedback resistor that is not connected in series with the second feedback resistor is electrically connected to the output terminal of the drive circuit. The end of the second feedback resistor that is not connected in series with the first feedback resistor is grounded.

[0016] The third feedback resistor and the fourth feedback resistor are connected in series. One end of the third feedback resistor and the fourth feedback resistor connected in series is electrically connected to the non-inverting input terminal of the operational amplifier. The end of the third feedback resistor that is not connected in series with the fourth feedback resistor is electrically connected to the reverse excitation coil. The end of the fourth feedback resistor that is not connected in series with the third feedback resistor is grounded.

[0017] The output terminal of the operational amplifier is electrically connected to the input terminal of the driver circuit;

[0018] The excitation current generated by the self-excited oscillation circuit flows into the end of the excitation coil that is electrically connected to the output terminal of the drive circuit.

[0019] One end of the first low-pass filter is electrically connected to the output of the driving circuit, and the other end outputs the first output voltage signal and is electrically connected to the compensation unit.

[0020] In some embodiments of this application, the driving circuit includes a push-pull circuit, which includes a first transistor and a second transistor with different polarities. The emitters of the first transistor and the second transistor are connected together as the output terminal of the driving circuit, and the bases of the first transistor and the second transistor are connected together as the input terminal of the driving circuit. The collector of the first transistor is connected to a first voltage terminal, and the collector of the second transistor is connected to a second voltage terminal.

[0021] An impedance matching resistor is connected in series between the output terminal of the operational amplifier and the input terminal of the driver circuit.

[0022] In some embodiments of this application, the AC zero flux detection unit includes an AC induction coil, a parallel resistor, a first differential amplifier, a second low-pass filter, and a third low-pass filter, wherein,

[0023] An AC induction coil is wound on a third toroidal magnetic core. One end of the AC induction coil is electrically connected to one end of a second low-pass filter, and the other end is electrically connected to one end of the second low-pass filter.

[0024] A parallel resistor is connected in parallel between one end and the other end of the AC induction coil;

[0025] The other end of the second low-pass filter is electrically connected to the positive input terminal of the first differential amplifier;

[0026] The other end of the third low-pass filter is electrically connected to the negative input terminal of the first differential amplifier;

[0027] The output terminal of the first differential amplifier outputs a second output voltage signal, which is electrically connected to the compensation unit.

[0028] In some embodiments of this application, it further includes: a measurement value output unit, which obtains the current value of the measured current based on the secondary compensation current flowing out of the secondary coil.

[0029] In some embodiments of this application, the compensation unit, in addition to including a secondary coil, further includes: a summing circuit, a proportional-integral converter, and a power amplifier, wherein,

[0030] The secondary coil is wound on the first toroidal core, the second toroidal core and the third toroidal core. One end of the secondary coil is electrically connected to the output terminal of the power amplifier and the other end is electrically connected to the measurement value output unit.

[0031] The summing circuit includes multiple input terminals and one output terminal. The multiple input terminals of the summing circuit are electrically connected to the end of the first low-pass filter that is not connected to the output terminal of the driving circuit, and are electrically connected to the output terminal of the first differential amplifier. The output terminal of the summing circuit is electrically connected to the input terminal of the proportional-integral converter. The summing circuit sums the first output voltage signal and the second output voltage signal.

[0032] The output of the proportional-integral converter is electrically connected to the input of the power amplifier, and the secondary-side compensation current is output from the output of the power amplifier.

[0033] In some embodiments of this application, the compensation unit further includes a bias compensation circuit, which generates a bias compensation voltage. The bias compensation circuit is electrically connected to the input terminal of the summing circuit, which sums the bias compensation voltage, the first output voltage signal, and the second output voltage signal.

[0034] The measurement output unit includes a measuring resistor, a second differential amplifier, an analog-to-digital converter, and a processor. One end of the measuring resistor is electrically connected to the positive input terminal of the second differential amplifier and the end of the secondary coil that is not connected to the output terminal of the power amplifier. The other end of the measuring resistor is grounded and electrically connected to the negative input terminal of the second differential amplifier. The output terminal of the second differential amplifier is electrically connected to the input terminal of the analog-to-digital converter. The output terminal of the analog-to-digital converter is electrically connected to the processor.

[0035] Secondly, embodiments of this application also provide a detection system, including the aforementioned fluxgate sensor.

[0036] The embodiments of this application may have, or at least have, the following advantages:

[0037] In this embodiment of the application, a fluxgate sensor and detection system are described. The fluxgate sensor includes a DC zero flux detection unit, an AC zero flux detection unit, and a compensation unit. The DC and AC zero flux detection units are electrically connected to the compensation unit. Specifically, the DC zero flux detection unit generates an excitation current through self-excited oscillation and generates a first output voltage signal based on the measured current. The AC zero flux detection unit generates a second output voltage signal based on the measured current. The compensation unit includes a secondary coil, which determines a secondary compensation current based on the first output voltage signal. When the secondary compensation current flows through the secondary coil, it generates a compensation magnetic field. The compensation magnetic field cancels the magnetic field generated by the measured current, thereby achieving zero flux in the fluxgate sensor. Since the DC zero flux detection unit and the compensation unit form a closed loop, and the AC zero flux detection unit and the compensation unit form another closed loop, the DC zero flux detection unit is not only used to generate excitation current through self-excited oscillation, but also generates a first output voltage signal based on the measured current. The AC zero flux detection unit generates a second output voltage signal based on the measured current. The compensation unit determines the secondary compensation current based on the first output voltage signal and the second output voltage signal. When the secondary compensation current flows through the secondary coil, it generates a compensation magnetic field. The compensation magnetic field cancels the magnetic field generated by the measured current, realizing the closed-loop zero flux of the fluxgate sensor, thereby improving the detection accuracy of the fluxgate sensor and widening the detection range of the fluxgate sensor.

[0038] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the structure of the fluxgate sensor provided in some embodiments of this application;

[0041] Figure 2 This is a schematic diagram of the circuit principle of the fluxgate sensor provided in some embodiments of this application;

[0042] Figure 3 This is a schematic diagram of the circuit operation of the fluxgate sensor provided in some embodiments of this application;

[0043] Figure 4 This is a schematic diagram of the circuit operation of the fluxgate sensor provided in some embodiments of this application.

[0044] Explanation of reference numerals in the attached figures:

[0045] DC zero flux detection unit 11; drive circuit 11a; AC zero flux detection unit 12; compensation unit 13; measurement output unit 14; first toroidal core C1; second toroidal core C2; ​​third toroidal core C3; first low-pass filter LPF1; second low-pass filter LPF2; third low-pass filter LPF3; first feedback resistor R1; second feedback resistor R2; third feedback resistor R3; fourth feedback resistor R4; impedance matching resistor R5; parallel resistor R6; measurement resistor R7; operational amplifier OPA; excitation coil We; reverse excitation coil Wf; AC induction coil Wa; secondary coil Ws; first transistor T1; second transistor T2; first differential amplifier DA1; summing circuit SUM; proportional-integral converter PI; power amplifier AMP; second differential amplifier DA2; analog-to-digital converter ADC. Detailed Implementation

[0046] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0047] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application's specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0048] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, parts, regions, layers, doping types, and / or portions, these elements, parts, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, part, region, layer, doping type, or portion from another element, part, region, layer, doping type, or portion. Therefore, without departing from the teachings of this application, the first element, part, region, layer, doping type, or portion discussed below may be referred to as a second element, part, region, layer, or portion.

[0049] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, in this specification, the term “and / or” includes any and all combinations of the associated listed items.

[0050] This application first provides a fluxgate sensor. Figure 1 This is a schematic diagram of the structure of the fluxgate sensor provided in some embodiments of this application; Figure 2 This is a schematic diagram of the circuit principle of the fluxgate sensor provided in some embodiments of this application.

[0051] refer to Figure 1 The fluxgate sensor includes a DC zero flux detection unit 11, an AC zero flux detection unit 12, and a compensation unit 13. The DC zero flux detection unit 11 and the AC zero flux detection unit 12 are electrically connected to the compensation unit 13, wherein:

[0052] The DC zero flux detection unit 11 is used to generate an excitation current Ie through self-excited oscillation and generate a first output voltage signal Vdc according to the measured current Id.

[0053] The AC zero flux detection unit 12 is used to generate a second output voltage signal Vac based on the measured current Id;

[0054] The compensation unit 13 includes a secondary coil Ws, which is used to determine the secondary compensation current Is based on the first output voltage signal Vdc. When the secondary compensation current Is flows through the secondary coil Ws, it generates a compensation magnetic field. The compensation magnetic field cancels the magnetic field generated by the measured current Id, thereby achieving zero magnetic flux of the fluxgate sensor.

[0055] In this application, the DC zero flux detection unit 11 and the compensation unit 13 form a closed loop, and the AC zero flux detection unit and the compensation unit 13 form another closed loop. The DC zero flux detection unit 11 is not only used to generate the excitation current Ie through self-excited oscillation, but also generates a first output voltage signal Vdc according to the measured current Id. The AC zero flux detection unit 12 generates a second output voltage signal Vac according to the measured current Id. The compensation unit 13 determines the secondary compensation current Is according to the first output voltage signal Vdc. When the secondary compensation current Is flows through the secondary coil Ws, it generates a compensation magnetic field. The compensation magnetic field cancels the magnetic field generated by the measured current Id, realizing the closed-loop zero flux of the fluxgate sensor, thereby improving the detection accuracy of the fluxgate sensor and widening the detection range of the fluxgate sensor.

[0056] refer to Figure 2 The fluxgate sensor also includes a first annular magnetic core C1, a second annular magnetic core C2, and a third annular magnetic core C3 stacked sequentially along a stacking direction, opposite to the direction of the measured current Id. The first annular magnetic core C1, the second annular magnetic core C2, and the third annular magnetic core C3 are all annular in shape and are made of a high-permeability material, such as permalloy.

[0057] In some embodiments, the DC zero flux detection unit 11 includes a self-oscillating circuit and a first low-pass filter LPF1 electrically connected to the self-oscillating circuit. The self-oscillating circuit is used to generate an excitation current Ie through self-oscillation. (Continue to refer to...) Figure 2 The self-excited oscillation circuit includes an excitation coil We, a reverse excitation coil Wf, a drive circuit 11a, a first feedback resistor R1, a second feedback resistor R2, a third feedback resistor R3, a fourth feedback resistor R4, and an operational amplifier OPA.

[0058] The drive circuit 11a includes an input terminal and an output terminal;

[0059] The excitation coil We is wound on the first toroidal magnetic core C1. One end of the excitation coil We is electrically connected to the output terminal of the drive circuit 11a, and the other end is connected to one end of the reverse excitation coil Wf. The excitation coil We is made of enameled wire and the number of turns of the excitation coil We is Ne (Ne is greater than 1). The excitation current Ie generated by the self-excited oscillation circuit flows into the end of the excitation coil We that is electrically connected to the output terminal of the drive circuit 11a, so that the excitation coil We generates an excitation magnetic field.

[0060] The reverse excitation coil Wf is wound in the opposite direction (opposite to the winding direction of the excitation coil We) on the second toroidal core C2. One end of the reverse excitation coil Wf is electrically connected to the excitation coil We, and the other end is electrically connected to one end of the third feedback resistor R3. The reverse excitation coil Wf is made of enameled wire and has Nf (Nf is greater than 1) turns. The reverse excitation coil Wf can generate a reverse magnetic field to counteract the excitation magnetic field generated by the excitation coil We, thereby reducing the zero-point bias and further improving the detection accuracy and sensitivity of the fluxgate current sensor.

[0061] The first feedback resistor R1 and the second feedback resistor R2 are connected in series. One end of the first feedback resistor R1 and the second feedback resistor R2 connected in series is electrically connected to the inverting input terminal of the operational amplifier OPA. The end of the first feedback resistor R1 that is not connected in series with the second feedback resistor R2 is electrically connected to the output terminal of the drive circuit 11a. The end of the second feedback resistor R2 that is not connected in series with the first feedback resistor R1 is grounded.

[0062] The third feedback resistor R3 and the fourth feedback resistor R4 are connected in series. One end of the third feedback resistor R3 and the fourth feedback resistor R4 connected in series is electrically connected to the non-inverting input terminal of the operational amplifier OPA. The end of the third feedback resistor R3 that is not connected in series with the fourth feedback resistor R4 is electrically connected to the reverse excitation coil Wf. The end of the fourth feedback resistor R4 that is not connected in series with the third feedback resistor R3 is grounded.

[0063] The output terminal of the operational amplifier OPA is electrically connected to the input terminal of the driver circuit 11a. The first feedback resistor R1, the second feedback resistor R2, the third feedback resistor R3 and the fourth feedback resistor R4 cooperate with the operational amplifier OPA and the driver circuit 11a to realize the self-excited oscillation of the self-excited oscillation circuit to generate the excitation current Ie.

[0064] One end of the first low-pass filter LPF1 is electrically connected to the output terminal of the drive circuit 11a, and the other end outputs the first output voltage signal Vdc and is electrically connected to the compensation unit 13. When the measured current Id is DC, the first output voltage signal Vdc changes with the magnitude of the measured current Id. The first low-pass filter LPF1 is used to perform low-pass filtering on the output voltage Ve of the output terminal of the drive circuit 11a and then output the first output voltage signal Vdc.

[0065] In some embodiments, the driving circuit 11a includes a push-pull circuit, which includes a first transistor T1 and a second transistor T2 of different polarities. The emitters of the first transistor T1 and the second transistor T2 are connected together as the output terminal of the driving circuit 11a, and the bases of the first transistor T1 and the second transistor T2 are connected together as the input terminal of the driving circuit 11a. The collector of the first transistor T1 is connected to a first voltage terminal, and the collector of the second transistor T2 is connected to a second voltage terminal. In one example, the first transistor T1 is an NPN transistor, the second transistor T2 is a PNP transistor, the first voltage terminal is a high voltage terminal with a voltage value of +15V, and the second voltage terminal is a low voltage terminal with a voltage value of -15V. In other examples, the voltage values ​​of the first and second voltage terminals can be other values. The push-pull circuit, in conjunction with the first feedback resistor R1, the second feedback resistor R2, the third feedback resistor R3, the fourth feedback resistor R4 and the operational amplifier OPA, achieves self-excited oscillation of the self-excited oscillation circuit to generate excitation current Ie. The specific process will be described in detail later.

[0066] In some embodiments, an impedance matching resistor R5 is connected in series between the output terminal of the operational amplifier OPA and the input terminal of the drive circuit 11a.

[0067] Continue to refer to Figure 2The self-excited oscillation circuit includes an excitation coil We, a reverse excitation coil Wf, a drive circuit 11a, a first feedback resistor R1, a second feedback resistor R2, a third feedback resistor R3, a fourth feedback resistor R4, and an operational amplifier OPA. The drive circuit 11a includes a push-pull circuit composed of a first transistor T1 and a second transistor T2 of different polarities. Specifically, when the upper bridge arm (first transistor T1) of the push-pull circuit is turned on, the self-oscillation point voltage is +15V. At this time, the voltage at the inverting input terminal "-" of the operational amplifier OPA is R2 / (R1+R2)*15V, where R1 is the resistance of the first feedback resistor R1 and R2 is the resistance of the second feedback resistor R2. Since the excitation coil We is not yet magnetically saturated, the voltage drop across it is significant, resulting in a very low voltage at the non-inverting input terminal "+" of the operational amplifier OPA, keeping the first transistor T1 on. However, when the excitation coil We is magnetically saturated, it can be considered as a wire, with almost no voltage drop. At this time, the voltage at the non-inverting input terminal "+" of the operational amplifier OPA is R4 / (R3+R4)*15V. R3 is the resistance value of the third feedback resistor R3, and R4 is the resistance value of the fourth feedback resistor R4. By reasonably setting the resistance values ​​of the first feedback resistor R1, the second feedback resistor R2, the third feedback resistor R3, and the fourth feedback resistor R4, so that R2 / (R1+R2)>R4 / (R3+R4), the operational amplifier OPA output can be made to have a negative voltage, realizing the conduction of the lower transistor (second transistor T2) in the push-pull circuit, thereby achieving the self-excited oscillation function. Since the self-excited oscillation circuit will generate a square wave of a certain frequency at the self-excited oscillation point ve, and since this application uses closed-loop magnetic modulation, the duty cycle of the square wave at the self-excited oscillation point will be maintained at about 50%. Therefore, this application detects the voltage at the closed-loop signal output point on the secondary coil Ws (i.e., the measured voltage U across the measuring resistor R7) and achieves accurate detection of the measured current Id through a certain conversion formula.

[0068] In some embodiments, continue to refer to Figure 2 The AC zero flux detection unit 12 includes an AC induction coil Wa, a parallel resistor R6, a first differential amplifier DA1, a second low-pass filter LPF2, and a third low-pass filter LPF3, wherein...

[0069] An AC induction coil Wa is wound on a third toroidal magnetic core C3. One end of the AC induction coil Wa is electrically connected to one end of the second low-pass filter LPF2, and the other end is electrically connected to one end of the second low-pass filter LPF2. The AC induction coil Waf is made of enameled wire, and the number of turns of the AC induction coil Wa is Na (Na is greater than 1). When the measured current Id is AC, the AC induction coil Wa senses the AC measured current Id and generates an induced voltage signal.

[0070] The parallel resistor R6 is connected in parallel between one end and the other end of the AC induction coil Wa;

[0071] The other end of the second low-pass filter LPF2 is electrically connected to the positive input terminal of the first differential amplifier DA1;

[0072] The other end of the third low-pass filter LPF3 is electrically connected to the negative input terminal of the first differential amplifier DA1. The second low-pass filter LPF2 and the third low-pass filter LPF3 are used to perform low-pass filtering on the induced voltage signal.

[0073] The output terminal of the first differential amplifier DA1 outputs a second output voltage signal Vac, which is electrically connected to the compensation unit 13. Specifically, the first differential amplifier DA1 is used to acquire the AC differential signal in the filtered induced voltage signal and amplify it to output the second output voltage signal Vac.

[0074] In some embodiments, continue to refer to Figure 1 The fluxgate sensor also includes a measurement value output unit 14, which obtains the current value of the measured current Id based on the secondary compensation current Is flowing out of the secondary coil Ws.

[0075] In some embodiments, continue to refer to Figure 1 The compensation unit 13, in addition to the secondary coil Ws, also includes: a summing circuit SUM, a proportional-integral circuit PI, and a power amplifier AMP.

[0076] The secondary coil Ws is wound on the first toroidal core C1, the second toroidal core C2, and the third toroidal core C3. One end of the secondary coil Ws is electrically connected to the output terminal of the power amplifier AMP, and the other end is electrically connected to the measurement output unit 14. The secondary coil Ws is made of enameled wire and has Ns (Ns is greater than 1) turns. When the secondary compensation current Is flows through the secondary coil Ws, it generates a compensation magnetic field. The compensation magnetic field cancels the magnetic field generated by the measured current Id, thereby achieving zero flux of the fluxgate sensor. Furthermore, the use of the secondary coil Ws enables the fluxgate sensor to form a closed-loop structure (the DC zero flux detection unit 11 and the compensation unit 13 (and the detection resistor R7) form a closed-loop circuit, and the AC zero flux detection unit and the compensation unit 13 (and the detection resistor R7) form another closed-loop circuit), realizing closed-loop zero flux of fluxgate technology and broadening the detection range of the fluxgate sensor.

[0077] The summing circuit SUM includes multiple (at least two) input terminals and one output terminal. The multiple input terminals of the summing circuit SUM are electrically connected to the end of the first low-pass filter LPF1 that is not connected to the output terminal of the drive circuit 11a, and are electrically connected to the output terminal of the first differential amplifier DA1. The output terminal of the summing circuit SUM is electrically connected to the input terminal of the proportional-integral converter PI. The summing circuit SUM sums the first output voltage signal Vdc and the second output voltage signal Vac to obtain the summed voltage signal Vs, and then outputs the summed voltage signal Vs to the proportional-integral converter PI.

[0078] The output of the proportional-integral (PI) converter is electrically connected to the input of the power amplifier AMP. The secondary compensation current Is is output from the output of the power amplifier AMP. The PI converter is used to address the deviation in the summed voltage signal Vs and eliminate the stable deviation in the summed voltage signal Vs, thereby filtering the summed voltage signal Vs. The function of the power amplifier AMP is to amplify the summed voltage signal Vs after it has been processed by the PI converter.

[0079] In some embodiments, continue to refer to Figure 2 The compensation unit 13 also includes a bias compensation circuit, which generates a bias compensation voltage Vb. The bias compensation circuit is electrically connected to the input of the summing circuit SUM, which sums the bias compensation voltage Vb, the first output voltage signal Vdc, and the second output voltage signal Vac. Due to interference from environmental magnetic fields such as the Earth's magnetic field and uneven coil winding, the fluxgate sensor may experience a zero-point bias problem. A voltage compensation circuit is designed to perform zero-point bias calibration, further improving the detection accuracy of the fluxgate sensor.

[0080] In some embodiments, continue to refer to Figure 2 The measurement output unit 14 includes a measuring resistor R7, a second differential amplifier DA2, an analog-to-digital converter ADC, and a processor. One end of the measuring resistor R7 is electrically connected to the positive input terminal of the second differential amplifier DA2 and the end of the secondary coil Ws that is not connected to the output terminal of the power amplifier AMP. The other end of the measuring resistor R7 is grounded and electrically connected to the negative input terminal of the second differential amplifier DA2. The output terminal of the second differential amplifier DA2 is electrically connected to the input terminal of the analog-to-digital converter ADC. The output terminal of the analog-to-digital converter ADC is electrically connected to the processor.

[0081] After passing through the DC zero flux detection unit 11, the AC zero flux detection unit 12, and the compensation unit 13, the larger measured current Id is precisely converted into a smaller secondary compensation current Is according to a certain ratio. The smaller secondary compensation current Is is then easily converted into a measuring voltage U through the precision measuring resistor R7. This measuring voltage U is differentially amplified by the second differential amplifier DA2 and then converted to digital form by the analog-to-digital converter ADC to obtain the digital signal of the measuring voltage U. The digital signal of the measuring voltage U is transmitted to the processor, which calculates the current value of the measured current Id based on the corresponding current calculation formula using the digital signal of the measuring voltage U.

[0082] In some embodiments, the processor includes a microprocessor (MCU) and a host computer (PC) connected to the MCU. The MCU can optimize the received data algorithm and transmit the optimized data to the host computer for further data processing and analysis. It can also use a current calculation formula to calculate the current value of the measured current Id.

[0083] The specific process of obtaining the current calculation formula is as follows:

[0084] By introducing a secondary coil Ws, the magnetic cores (first toroidal core C1, second toroidal core C2, and third toroidal core C3) are kept in a zero flux state. According to the equal ampere-turn theorem, the magnitude of the measured current Id and the magnitude of the secondary compensation current Is satisfy the following formula: ;

[0085] Where I d N d These represent the magnitude of the measured current Id and the number of turns of the coil corresponding to the measured current Id, respectively. s N s These represent the magnitude of the secondary compensation current Is and the number of turns of the secondary coil Ws, respectively.

[0086] The coil corresponding to the measured current Id has 1 turn, i.e., N. d =1. Therefore, the magnitude of the measured current Id is:

[0087]

[0088] A measuring voltage U exists across resistor R7. Therefore, the measuring voltage U is:

[0089] ;

[0090] Through formula conversion, the magnitude of the measured current Id is obtained. d for:

[0091] ;

[0092] K is the operational amplifier ratio of the second differential amplifier DA2, which is known. The measured voltage U can be obtained through the analog-to-digital converter (ADC), and is also known. The number of turns N of the secondary coil Ws is also known. s Since the resistance value of the measuring resistor R7 is known, the magnitude of the measured current Id can be obtained using the aforementioned formula. d .

[0093] The working principle of the aforementioned fluxgate sensor will be described in detail below.

[0094] refer to Figure 2 When the measured current Id is DC, Faraday's law of electromagnetic induction does not hold, therefore the AC zero flux detection unit 12 does not work (equivalent to a short circuit). Figure 2 As shown in the figure, the light-colored lines represent the areas where the function is lost. At this time, the DC zero flux detection unit 11, the compensation unit 13, and the measuring resistor R7 form a closed loop. During normal operation, the above closed loop is in a zero flux state, and the measured current of the DC zero flux detection unit 11 is equivalent to zero (actually equivalent to a very small differential current). The average value of the excitation current Ie in the excitation coil We is zero, that is, the first output voltage signal Vdc of the first low-pass filter LPF1 is zero. Since the AC zero flux detection unit 12 does not work under this condition, the second output voltage signal Vac generated on the AC induction coil Wa is zero, and therefore the summation voltage signal Vs output by the summing circuit SUM is zero, that is, the closed loop is in an ampere-turn balance state. At this time, the magnitude of the measured current Id and the magnitude of the secondary compensation current Is satisfy the formula: However, any magnetic flux imbalance will cause the average value of the excitation current Ie of the DC zero magnetic flux detection unit 11 to be non-zero, that is, the output voltage Ve at the output terminal of the drive circuit 11a will be non-zero (with the system error signal superimposed). After the signal passes through the first low-pass filter LPF1, it is transmitted to the compensation unit 13 as the first output voltage signal Vdc. The compensation unit 13 outputs the corresponding signal, which serves as the error signal of the proportional-integral unit PI, driving the power amplifier PA to output the corresponding secondary compensation current until the closed loop reaches ampere-turn balance again.

[0095] refer to Figure 3 When the measured current Id is AC, the DC zero flux detection unit 11 does not work (equivalent to a short circuit) due to the limitations of the frequency of the excitation current Ie and the cutoff frequency of the first low-pass filter LPF1. Figure 3As shown in the diagram, the lighter-colored lines represent areas where the function is lost. At this point, the AC zero-flux detection unit 12, the compensation unit 13, and the measuring resistor R7 form a closed-loop circuit, the so-called magnetic integrator. The magnetic integrator can essentially be viewed as a zero-flux active AC current transformer. Its working principle is similar to the closed-loop circuit formed by the DC zero-flux detection unit described above. The commonality is that the high open-loop gain of the proportional-integrator PI ensures that the closed-loop circuit remains in a zero-flux state within a certain frequency range. The difference is that the second output voltage signal is obtained by the AC induction coil Wa according to Faraday's law of electromagnetic induction. Using the AC induction coil Wa as the detection coil of the magnetic integrator suppresses the inductive modulation ripple caused by the transformer effect and improves the bandwidth of the fluxgate sensor.

[0096] This application also provides a detection system including a fluxgate sensor.

[0097] In the description of this application, the references to terms such as "some embodiments," "other embodiments," "ideal embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example that are included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0098] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0099] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A fluxgate sensor, characterized in that, The fluxgate sensor includes a DC zero flux detection unit, an AC zero flux detection unit, and a compensation unit. The DC zero flux detection unit and the AC zero flux detection unit are electrically connected to the compensation unit, wherein: The DC zero flux detection unit is used to generate excitation current through self-excited oscillation and generate a first output voltage signal according to the measured current. The AC zero flux detection unit is used to generate a second output voltage signal based on the measured current. The compensation unit includes a secondary coil, which is used to determine the secondary compensation current based on the first output voltage signal and the first output voltage signal. When the secondary compensation current flows through the secondary coil, it generates a compensation magnetic field. The compensation magnetic field cancels the magnetic field generated by the measured current, thereby achieving zero magnetic flux of the fluxgate sensor.

2. The fluxgate sensor according to claim 1, characterized in that, The fluxgate sensor further includes a first annular magnetic core, a second annular magnetic core, and a third annular magnetic core stacked sequentially along a stacking direction, the stacking direction being opposite to the direction of the current being measured flowing in.

3. The fluxgate sensor according to claim 2, characterized in that, The DC zero flux detection unit includes a self-excited oscillation circuit and a first low-pass filter electrically connected to the self-excited oscillation circuit. The self-excited oscillation circuit is used to generate excitation current through self-excited oscillation.

4. The fluxgate sensor according to claim 3, characterized in that, The self-excited oscillation circuit includes an excitation coil, a reverse excitation coil, a drive circuit, a first feedback resistor, a second feedback resistor, a third feedback resistor, a fourth feedback resistor, and an operational amplifier. The driving circuit includes an input terminal and an output terminal; The excitation coil is wound on the first annular magnetic core. One end of the excitation coil is electrically connected to the output terminal of the driving circuit, and the other end is connected to one end of the reverse excitation coil. The reverse excitation coil is wound in the reverse direction on the second annular magnetic core. One end of the reverse excitation coil is electrically connected to the excitation coil, and the other end is electrically connected to one end of the third feedback resistor. The first feedback resistor and the second feedback resistor are connected in series. One end of the first feedback resistor and the second feedback resistor connected in series is electrically connected to the inverting input terminal of the operational amplifier. The end of the first feedback resistor that is not connected in series with the second feedback resistor is electrically connected to the output terminal of the drive circuit. The end of the second feedback resistor that is not connected in series with the first feedback resistor is grounded. The third feedback resistor and the fourth feedback resistor are connected in series. One end of the third feedback resistor and the fourth feedback resistor connected in series is electrically connected to the non-inverting input terminal of the operational amplifier. The end of the third feedback resistor that is not connected in series with the fourth feedback resistor is electrically connected to the reverse excitation coil. The end of the fourth feedback resistor that is not connected in series with the third feedback resistor is grounded. The output terminal of the operational amplifier is electrically connected to the input terminal of the driving circuit; The excitation current generated by the self-excited oscillation circuit flows into one end of the excitation coil that is electrically connected to the output terminal of the drive circuit. One end of the first low-pass filter is electrically connected to the output terminal of the driving circuit, and the other end outputs the first output voltage signal and is electrically connected to the compensation unit.

5. The fluxgate sensor according to claim 4, characterized in that, The driving circuit includes a push-pull circuit, which includes a first transistor and a second transistor with different polarities. The emitters of the first transistor and the second transistor are connected together as the output terminal of the driving circuit, and the bases of the first transistor and the second transistor are connected together as the input terminal of the driving circuit. The collector of the first transistor is connected to a first voltage terminal, and the collector of the second transistor is connected to a second voltage terminal. An impedance matching resistor is connected in series between the output terminal of the operational amplifier and the input terminal of the driving circuit.

6. The fluxgate sensor according to claim 3, characterized in that, The AC zero flux detection unit includes an AC induction coil, a parallel resistor, a first differential amplifier, a second low-pass filter, and a third low-pass filter, wherein... The AC induction coil is wound on the third annular magnetic core. One end of the AC induction coil is electrically connected to one end of the second low-pass filter, and the other end is electrically connected to one end of the second low-pass filter. The parallel resistor is connected in parallel between one end and the other end of the AC induction coil; The other end of the second low-pass filter is electrically connected to the positive input terminal of the first differential amplifier; The other end of the third low-pass filter is electrically connected to the negative input terminal of the first differential amplifier; The output terminal of the first differential amplifier outputs a second output voltage signal, which is electrically connected to the compensation unit.

7. The fluxgate sensor according to claim 6, characterized in that, Also includes: The measurement value output unit obtains the current value of the measured current based on the secondary compensation current flowing out of the secondary coil.

8. The fluxgate sensor according to claim 7, characterized in that, In addition to the secondary coil, the compensation unit also includes a summing circuit, a proportional-integral converter, and a power amplifier. The secondary coil is wound on the first toroidal core, the second toroidal core and the third toroidal core. One end of the secondary coil is electrically connected to the output terminal of the power amplifier and the other end is electrically connected to the measurement value output unit. The summing circuit includes multiple input terminals and one output terminal. The multiple input terminals of the summing circuit are electrically connected to the end of the first low-pass filter that is not connected to the output terminal of the driving circuit, and are electrically connected to the output terminal of the first differential amplifier. The output terminal of the summing circuit is electrically connected to the input terminal of the proportional-integral unit. The summing circuit sums the first output voltage signal and the second output voltage signal. The output terminal of the proportional-integral converter is electrically connected to the input terminal of the power amplifier, and the secondary-side compensation current is output from the output terminal of the power amplifier.

9. The fluxgate sensor according to claim 8, characterized in that, The compensation unit further includes a bias compensation circuit, which generates a bias compensation voltage. The bias compensation circuit is electrically connected to the input terminal of the summing circuit, which sums the bias compensation voltage, the first output voltage signal, and the second output voltage signal. The measurement output unit includes a measuring resistor, a second differential amplifier, an analog-to-digital converter, and a processor. One end of the measuring resistor is electrically connected to the positive input terminal of the second differential amplifier and the end of the secondary coil that is not connected to the output terminal of the power amplifier. The other end of the measuring resistor is grounded and electrically connected to the negative input terminal of the second differential amplifier. The output terminal of the second differential amplifier is electrically connected to the input terminal of the analog-to-digital converter. The output terminal of the analog-to-digital converter is electrically connected to the processor.

10. A detection system, characterized in that, The detection system includes: a fluxgate sensor as described in any one of claims 1-9.

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