Low-power and low-loss proportionally amplified fluxgate current sensor and measurement method

Abstract

The present invention discloses a low-power, low-loss proportionally amplified fluxgate current sensor and a measuring method, wherein the sensor comprises a hollow-structured magnetic core, a logic judgment device, an excitation signal generating device and a signal processing device; the magnetic core is a hollow-structured circular ring structure formed by alternately stacking semicircular rings and full circular rings of the same radius but different angles, a first excitation winding is wound on the alternating sides of the semicircular rings and full circular rings, and a second excitation winding is wound on the alternating sides of the full circular rings and gaps; according to the magnitude of the current to be measured determined by the logic judgment device, the input end of the first / or second excitation winding is controlled to be connected to the excitation signal generating device and the output end of the first / or second excitation winding is controlled to be connected to the signal processing device. The fluxgate current sensor provided by the present invention can proportionally amplify the small current to be measured and expand the measurement range of the sensor by adopting a hollow-structured magnetic core, and can also effectively reduce the power consumption of the sensor and the loss in the magnetic core, thereby improving the measurement accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical engineering and measuring electric variables, and in particular relates to a low-power and low-loss proportionally amplified fluxgate current sensor and a measuring method. Background Art

[0002] In recent years, with the development of smart grid technology, more and more power equipment status monitoring technology has attracted attention. The status of many power equipment is judged by monitoring the voltage at both ends of the equipment and the current flowing through the equipment. However, due to the materials and structures of many power equipment, the current flowing through the equipment is as small as microamperes. In addition, the electromagnetic interference in the environment where the power equipment is located increases the difficulty of current measurement. At the same time, in order to achieve continuous status monitoring of power equipment, the loss of status monitoring equipment is also a factor that must be considered. The loss problem will seriously affect the measurement accuracy of the equipment.

[0003] The fluxgate sensor is a current sensor that measures weak magnetic fields based on fluxgate technology by utilizing the nonlinear relationship between the magnetic induction intensity and the magnetic field intensity of a high permeability magnetic core in the measured magnetic field under saturation excitation of an alternating magnetic field, and indirectly measures DC current through the relationship between the weak magnetic field and the current to be measured.

[0004] When a traditional fluxgate current sensor measures a small DC current, the magnetic field strength generated in the magnetic core will be very weak due to the small DC current to be measured. In order to achieve the prerequisite of periodic saturation and unsaturation state changes of the magnetic core, a large excitation signal needs to be added to the excitation winding coil. Under the action of the alternating magnetic field generated by the large excitation signal, a symmetrical induced electrical signal containing only odd harmonics will be generated in the induction coil. Under the action of the magnetic field generated by the DC current to be measured, the symmetrical electrical signal in the induction coil will be offset. Since the DC current to be measured is small, the offset of the electrical signal inside the induction coil caused by the magnetic field generated by it will be very small compared to the entire electrical signal, which will seriously affect the measurement accuracy of the sensor under the interference of noise. In addition, the large excitation signal added to achieve periodic saturation of the magnetic core will also increase the power consumption of the sensor and the loss inside the magnetic core. The resulting temperature rise of the magnetic core will affect the magnetic permeability, saturation magnetic induction intensity and other parameters of the magnetic core material, thereby further affecting the measurement accuracy of the fluxgate current sensor.

[0005] When a traditional fluxgate current sensor measures a relatively large DC current, due to the large DC current to be measured, a relatively strong magnetic field will be generated in the magnetic core, which will cause the magnetic core to tend to saturation or reach saturation. In order to achieve the prerequisite of periodic saturation and non-saturation state changes of the magnetic core, it is necessary to add an excitation signal larger than the large DC current to be measured in the excitation winding coil to achieve negative saturation of the magnetic core. The alternating magnetic field generated by the excitation signal will cause a symmetrical electrical signal containing only odd harmonics to be generated in the induction coil. Under the influence of the strong magnetic field generated by the large DC current to be measured, the original electrical signal in the induction coil will be offset to a large extent. Compared with the measurement of small currents, it has higher measurement accuracy. However, under the influence of the larger DC current to be measured and the larger excitation signal and the alternating strong magnetic field generated by it, the power consumption of the fluxgate current sensor and the eddy current and hysteresis losses inside the magnetic core will also increase sharply. The larger temperature rise generated by the magnetic core will reversely affect some characteristic parameters of the magnetic core, resulting in a decrease in the measurement accuracy of the fluxgate current sensor.

[0006] The probe of a traditional fluxgate current sensor consists of three parts: a magnetic core, an excitation winding coil, and an induction coil. The magnetic core is usually a circular ring structure with uniform texture and regular shape. The circular ring structure of the traditional magnetic core limits the measurement range of the fluxgate current sensor. When the cross-sectional area of ​​the magnetic core is larger than the DC current value to be measured, the magnetic flux density generated by the current to be measured inside the magnetic core is smaller. Under the interference of noise, the originally weak magnetic field will be more difficult to measure. At the same time, a larger excitation signal is required to achieve periodic saturation of the magnetic core, which will increase the power consumption and loss of the fluxgate current sensor; when the cross-sectional area of ​​the magnetic core is smaller than the current value to be measured, the magnetic field generated by the current to be measured alone can make the magnetic core tend to or reach positive saturation, which requires a larger excitation signal to achieve negative saturation of the magnetic core; a larger excitation signal and a larger current to be measured will not only increase the power consumption and internal loss of the fluxgate current sensor, but the temperature rise caused by the loss will also affect the measurement accuracy of the sensor.

[0007] In summary, the magnetic core of the traditional fluxgate current sensor is a major reason for limiting the sensor's measurement range, which also leads to a narrow measurement range of the traditional fluxgate current sensor. In addition, whether measuring small currents or large currents, power consumption and loss are inevitable and cannot be ignored in the measurement process of the fluxgate current sensor, because the loss mainly comes from the eddy current loss and hysteresis loss inside the magnetic core. Excessive loss will cause the core temperature to rise and then affect the changes in characteristic parameters such as the magnetic permeability of the magnetic core material, and ultimately affect the measurement accuracy of the sensor. Therefore, it is of great significance to reduce the power consumption and loss of traditional fluxgate current sensors. Summary of the invention

[0008] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides a low-power and low-loss proportionally amplified fluxgate current sensor and a measurement method. The magnetic core structure in the fluxgate current sensor is a hollow circular ring structure formed by alternatingly stacking semi-circular Permalloy sheets and full-circular Permalloy sheets with the same radius but different angles. It can not only proportionally amplify the small current to be measured and expand the measurement range of the sensor, but also effectively reduce the power consumption of the sensor and the loss in the magnetic core, thereby further improving the measurement accuracy of the sensor.

[0009] The first object of the present invention can be achieved by adopting the following technical solutions:

[0010] A low-power, low-loss proportionally amplified fluxgate current sensor, comprising a hollow-structured magnetic core, an excitation signal generating device, a signal processing device, and a logic judgment device. When the fluxgate current sensor is working, the logic judgment device automatically switches the measurement scheme according to the magnitude of the current to be measured, wherein:

[0011] The magnetic core is a hollow ring structure formed by alternately stacking half rings and full rings with the same radius but different angles, a first excitation winding for measuring large current is wound on the alternately stacked side of the half rings and full rings, and a second excitation winding for measuring small current is wound on the alternately stacked side of the full rings and gaps, wherein the half rings and full rings are electrically insulated;

[0012] The excitation signal generating device includes two self-excited oscillation signal generating circuits, corresponding to the first excitation winding and the second excitation winding respectively; the input end of the excitation signal generating device is connected to the output end of the logic judgment device, and the output end is connected to the corresponding first excitation winding or the second excitation winding;

[0013] The signal processing device includes two level signal processing circuits corresponding to the first excitation winding and the second excitation winding respectively, wherein the output end of the level signal processing circuit corresponding to the first excitation winding is connected to the input end of the logic judgment device and the first excitation winding.

[0014] Furthermore, the number of turns of the first excitation winding is greater than the number of turns of the second excitation winding.

[0015] Furthermore, the angles of the semicircular ring and the full circular ring differ by 180°, and the materials are both 1J85 type Permalloy with high magnetic permeability and low coercivity.

[0016] Furthermore, the logic judgment device automatically switches the measurement scheme according to the magnitude of the current to be measured, including:

[0017] The logic judgment device determines the excitation winding put into operation by judging the size of the current to be measured; and measures the voltage of the excitation winding put into operation using the level signal processing circuit corresponding to the excitation winding put into operation to obtain the value of the current to be measured.

[0018] Furthermore, the signal processing device also includes a digital signal processing circuit;

[0019] The two levels of signal processing circuits are respectively a first level signal processing circuit and a second level signal processing circuit, which are used to measure the large and small currents to be measured;

[0020] The logic judgment device determines the excitation winding put into operation by judging the magnitude of the current to be measured; and measures the voltage of the excitation winding put into operation by using the level signal processing circuit corresponding to the excitation winding put into operation to obtain the value of the current to be measured, including:

[0021] The logic judgment device controls the first excitation winding to be connected to its corresponding self-excited oscillation signal generating circuit; the first level signal processing circuit starts to work to collect electrical signals from the first excitation winding, and feeds back the processed electrical signals to the first excitation winding and the logic judgment device;

[0022] The logic judgment device judges the processed electrical signal. If it is a large current, the first excitation winding is still connected to the corresponding self-excited oscillation signal circuit, and the first-level signal processing circuit continues to work to collect and process the electrical signal from the first excitation winding; if it is a small current, the logic judgment device controls the first excitation winding to be disconnected from the corresponding self-excited oscillation signal generating circuit, and controls the second excitation winding to be connected to the corresponding self-excited oscillation signal generating circuit; the second-level signal processing circuit starts to work to collect and process the electrical signal from the second excitation winding;

[0023] The processed electrical signal passes through the digital signal processing circuit to obtain the value of the current to be measured.

[0024] Furthermore, the first-level signal processing circuit includes a differential voltage stabilization circuit, a voltage divider circuit, an integral amplifier circuit, a low-pass filter circuit, and a dual-channel feedback circuit;

[0025] When the first-level signal processing circuit is working, the electrical signal collected from the first excitation winding is passed through a differential voltage stabilization circuit to eliminate the influence of noise, and then input into the integral amplifier circuit after passing through a voltage divider circuit to obtain the integral value of the current to be measured. The integrated electrical signal is processed by a low-pass filter, and then the processed electrical signal is fed back to the first excitation winding and the logic judgment device respectively through a dual-channel feedback circuit; wherein, the signal fed back to the first excitation winding is used to offset the offset of the electrical signal in the first excitation winding caused by the current to be measured, so that the average magnetic field strength inside the magnetic core is zero; the signal fed back to the logic judgment device is used to help the logic judgment device determine the size of the current to be measured, and determine the excitation winding to be put into operation according to the size of the current to be measured. The connection between the self-excited oscillation signal generating circuit and the signal processing circuit.

[0026] Furthermore, the second-level signal processing circuit includes a differential amplifier circuit, a multi-stage amplifier circuit and a bandpass filter circuit;

[0027] When the second-level signal processing circuit is working, the electrical signal collected from the second excitation winding is eliminated by the differential amplifier circuit, and then the small signal is amplified by the multi-stage amplifier circuit. The amplified signal is passed through the bandpass filter circuit to obtain the even harmonic content.

[0028] Furthermore, the logic judgment device includes a low-power MCU and a peripheral signal acquisition circuit;

[0029] The peripheral signal acquisition circuit acquires the processed electrical signal;

[0030] The low-power MCU performs analog-to-digital conversion on the electrical signal collected by the peripheral signal collection circuit; the magnitude of the current to be measured is determined according to the converted value and a threshold value set in the low-power MCU: if the converted value is greater than the threshold value, the current to be measured is a large current, otherwise the current to be measured is a small current;

[0031] According to the determined magnitude of the current to be measured, the output signal of the low-power MCU is used as a switch control signal to connect the excitation winding put into operation to its corresponding self-excited oscillation signal generating circuit and signal processing circuit.

[0032] Furthermore, the excitation signal generating device also includes a power amplifier circuit;

[0033] The two self-excited oscillation signal generating circuits are a first winding self-excited oscillation signal generating circuit and a second winding self-excited oscillation signal generating circuit, which correspond to the first excitation winding and the second excitation winding respectively, and are used to generate high-frequency sinusoidal wave excitation signals;

[0034] The first winding self-excited oscillation signal generating circuit and the second winding self-excited oscillation signal generating circuit are both connected to the corresponding excitation winding through the power amplifier circuit.

[0035] The second object of the present invention can be achieved by adopting the following technical solutions:

[0036] A current measurement method uses the fluxgate current sensor as described above to measure the current of a conductor.

[0037] The present invention has the following beneficial effects compared with the prior art:

[0038] 1. The fluxgate current sensor provided by the present invention adopts a hollow ring structure formed by alternating stacking of semi-circular Permalloy sheets and full-circular Permalloy sheets with the same radius. Although the hollow ring structure of the magnetic core cannot essentially amplify the current to be measured, it can increase the proportion of even harmonics caused by the current to be measured in the excitation winding coil, thereby achieving the purpose of proportionally amplifying the current to be measured, and can improve the measurement accuracy of the fluxgate current sensor. Since the second excitation winding coil is wound around the alternating sides of the full-circular Permalloy sheet and the gap, the self-excited oscillation signal generating circuit only needs to generate a smaller excitation signal to achieve forward and reverse saturation of the magnetic core on this side. Amplifying the proportion of the current to be measured compared to the excitation signal can not only reduce the error in the signal processing process and improve the measurement accuracy of the sensor, but also achieve the purpose of reducing the power consumption of the sensor by reducing the excitation signal.

[0039] 2. The fluxgate current sensor provided by the present invention selects different self-excited oscillation signal generating circuits and signal processing circuits according to the magnitude of different current values ​​to be measured, thereby increasing the measurement range of the sensor and significantly reducing the power consumption compared to the traditional fluxgate current sensor. In particular, in the process of measuring weak (small) currents, the magnetic induction intensity in the magnetic core on the alternating side of the full-circle Permalloy sheet and the gap is greater than the magnetic induction intensity in the magnetic core on the alternating side of the semi-circle Permalloy sheet and the full-circle Permalloy sheet, thereby reducing the size of the excitation signal in the second excitation winding, achieving the purpose of reducing the power consumption of the sensor.

[0040] 3. The fluxgate current sensor provided by the present invention has a signal processing circuit including a first-level signal processing circuit for processing a large current to be measured and a second-level signal processing circuit for processing a weak current to be measured. The two types of signal processing circuits are essentially different. There are also obvious differences in the processing process of electrical signals in different ranges, wherein the first-level signal processing circuit is a closed-loop control with dual feedback signals, while the second-level signal processing circuit is an open-loop control. After receiving the feedback signal from the first-level signal processing circuit, the logic judgment device compares the received signal with the set threshold value. If it is greater than the threshold value, it is judged that the current to be measured is a large current. The first-level signal processing circuit starts to work, and will measure the electrical signal in the first excitation winding and feed it back to the first excitation winding and the logic judgment device after a series of processing until the signal processing circuit works in a steady state. At this time, the average magnetic field strength inside the sensor core is zero; if the received feedback signal is less than the threshold value, it is judged that the current to be measured is a small current, and the second-level signal processing circuit starts to work, and will measure the electrical signal in the second excitation winding and pass through the amplification and filtering circuit. Finally, the value of the weak current to be measured is obtained by the digital signal processing circuit. In this process, the average magnetic field strength inside the sensor core is not zero and the average magnetic field strength is numerically equal to the magnetic field strength generated by the current to be measured.

[0041] 4. The fluxgate current sensor provided by the present invention can effectively reduce the eddy current loss and hysteresis loss caused by the magnetic core by using the hollow magnetic core structure, thereby ensuring the stability of the characteristic parameters of the magnetic core material and improving the measurement accuracy of the sensor. Regardless of whether the current to be measured is a large current or a weak current, the magnetic field intensity distribution state inside the magnetic core is always that the magnetic field intensity of the alternating side of the whole circular Permalloy sheet and the gap is greater than the magnetic field intensity of the alternating stacking side of the semicircular Permalloy sheet and the whole circular Permalloy sheet. A stronger alternating magnetic field will cause greater losses in the magnetic core on the alternating side of the whole circular Permalloy sheet and the gap, especially in the process of measuring large currents, the losses in the magnetic core on the alternating side of the whole circular Permalloy sheet and the gap will be greater, and different degrees of losses in the magnetic core will cause different degrees of temperature rise, which will affect the characteristic parameters such as the magnetic permeability and saturation magnetic induction intensity of the magnetic core material, thereby further affecting the measurement accuracy of the fluxgate current sensor. The hollow ring structure of the magnetic core of the present invention, in which the semi-circular Permalloy sheets and the full-circular Permalloy sheets are alternately stacked, can significantly reduce the loss inside the magnetic core, reduce the influence of the temperature rise of the magnetic core on the characteristic parameters of the magnetic core material, and thus improve the measurement accuracy of the fluxgate current sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0043] Figure 1 This is a structural block diagram of the fluxgate current sensor according to embodiment 1 of the present invention.

[0044] Figure 2 Schematic diagram of the magnetic core structure of Example 1 of the present invention, wherein Figure (a) shows semicircular rings and full circular rings constituting the magnetic core structure, and Figure (b) shows a hollow circular ring structure in which semicircular rings and full circular rings with equal radius are alternately stacked.

[0045] Figure 3 1 is a schematic diagram of the signal processing flow of the signal processing device of Example 1 of the present invention, wherein Figures (a) and (b) are respectively signal processing flow diagrams when the first and second level signal processing circuits are working. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. It should be understood that the specific embodiments described are only used to explain the present invention and are not used to limit the present invention.

[0047] Embodiment 1:

[0048] An embodiment of the present invention provides a low-power, low-loss proportional amplification fluxgate current sensor, which is a fluxgate current sensor with low power consumption and low loss and can proportionally amplify small currents to be measured. The sensor judges the current range to be measured based on a feedback signal and forms a closed-loop or open-loop signal processing system with signal processing circuits of different levels.

[0049] like Figure 1 As shown, the low-power and low-loss proportionally amplified fluxgate current sensor provided by an embodiment of the present invention includes: a magnetic core with a hollow circular ring structure, a first excitation winding, a second excitation winding, an excitation signal generating device, a logic judgment device, a first-level signal processing device and a second-level signal processing device.

[0050] like Figure 2As shown, the hollow ring structure of the magnetic core described in the embodiment of the present invention is formed by alternately stacking semi-circular Permalloy sheets and full-circular Permalloy sheets with the same radius, wherein the angles of the semi-circular Permalloy sheets and the full-circular Permalloy sheets are different, and one full-circular Permalloy sheet can be made into two semi-circular Permalloy sheets; a first excitation winding and a second excitation winding are wound on the hollow ring magnetic core, and the wire constituting the excitation winding needs to have a smaller cross-sectional radius and a stronger current carrying capacity. The number of turns of the excitation winding is determined by the measurement range. Depending on the current range to be measured, the number of turns of the first excitation winding wound on the alternately stacked side of the semi-circular and full-circular Permalloy sheets is greater than the number of turns of the second excitation winding wound on the alternate side of the full-circular Permalloy sheets and the gap. In the embodiment of the present invention, the number of turns of the first excitation winding is 1-3 times the number of turns of the second excitation winding.

[0051] In the embodiment of the present invention, the basic component structure of the hollow-type magnetic core is a semi-circular Permalloy sheet and a full-circular Permalloy sheet, wherein the first excitation winding is wound on the alternately stacked side of the semi-circular Permalloy sheet and the full-circular Permalloy sheet, and the second excitation winding is wound on the alternately stacked side of the full-circular Permalloy sheet and the gap; the magnetic flux passing through each cross section of the magnetic core is constant, and due to the hollow-type structure, the magnetic flux density on the alternately stacked side of the full-circular Permalloy sheet and the gap is greater than the alternately stacked side of the semi-circular Permalloy sheet and the full-circular Permalloy sheet. Therefore, in the process of measuring small currents, the excitation signal of the required second excitation winding is smaller than the excitation signal in the first excitation winding, thereby reducing the power consumption of the sensor. The loss of the alternating sides of the full-circle Permalloy sheet and the gap due to the increase in magnetic flux density can be effectively reduced by alternating stacking of different types of circular rings. It should be noted that different types of Permalloy sheets are electrically insulated; the size of the magnetic core is related to the size of the required measured current and the wire that transmits the measured current. The simulation results show that the smaller the value of the measured current is, the smaller the size of the magnetic core is to maintain the accuracy of the measurement. Therefore, the specific size of the magnetic core should be determined according to the actual current value and the current-carrying wire; the size of the excitation signal should be determined according to the size of the magnetic core. Under the action of the measured current, the excitation signal should be able to meet the condition of periodic saturation of the magnetic core. In short, the size of the measured current determines the size of the magnetic core and the size of the excitation signal, and the determination of the size of the magnetic core and the size of the excitation signal can also determine the measurement range of the fluxgate current sensor.

[0052] The hollow circular magnetic core described in the embodiment of the present invention is made of 1J85 type Permalloy, and the basic structure of the magnetic core is a semicircular Permalloy sheet and a full-circular Permalloy sheet. The magnetic core is wound with excitation windings for different measurement ranges, and the size of the excitation signal can be flexibly adjusted to reduce the power consumption of the sensor. The first excitation winding and the second excitation winding both use fine enameled wires with a certain degree of insulation and a certain current carrying capacity.

[0053] like Figure 1 As shown, the main parts involved in the signal measurement and processing process in the embodiment of the present invention include a logic judgment device, an excitation signal generating device and a signal processing device, wherein the logic judgment device mainly includes a low-power MCU and a peripheral information acquisition circuit; the excitation signal generating device mainly includes a power amplifier circuit and two self-excited oscillation signal generating circuits; the signal processing device mainly includes a first-level signal processing circuit and a second-level signal processing circuit and share a digital signal processing circuit. In addition, the first-level signal processing circuit also includes a differential voltage stabilization circuit, a voltage divider circuit, an integral amplifier circuit, a low-pass filter circuit and a dual-channel feedback circuit, and the second-level signal processing circuit includes a differential amplifier circuit, a multi-stage amplifier circuit and a band-pass filter circuit.

[0054] The excitation signal generating device in the embodiment of the present invention includes a self-excited oscillation signal generating circuit and a power amplifier circuit corresponding to the first excitation winding coil and the second excitation winding coil, wherein the input and output of the power amplifier circuit are controlled by a low-power MCU, and after judgment by the MCU, the self-excited oscillation signal generating circuit used for operation will self-oscillate to generate a high-frequency sinusoidal wave excitation signal and input it into the power amplifier circuit, and the MCU will also control the output of the power amplifier circuit to be connected to the corresponding excitation winding coil. In this process, only one excitation winding coil and its corresponding self-excited oscillation signal generating circuit are in a working state, while the other excitation winding coil is in an open circuit state because it is not connected to its corresponding self-excited oscillation signal generating circuit, thereby avoiding mutual interference between the excitation winding coils.

[0055] The signal processing device described in the embodiment of the present invention includes a first-level signal processing circuit, a second-level signal processing circuit, and a digital signal processing circuit. In different working states, the measurement and processing process of the signal is different, and the magnetic field state inside the magnetic core is also significantly different, wherein:

[0056] The first-level signal processing circuit includes: a differential voltage stabilization circuit, a voltage divider circuit, an integral amplifier circuit, a low-pass filter circuit and a feedback circuit. The feedback circuit includes two feedback signals fed back to the first excitation winding coil and the logic judgment device. The signal fed back to the first excitation winding coil is used to offset the offset of the electrical signal in the excitation winding coil caused by the current to be measured, so that the average magnetic field strength inside the magnetic core is zero; the signal fed back to the logic judgment device is used to help the low-power MCU determine the range of the current to be measured, thereby determining the excitation winding coil and signal processing circuit to be put into operation.

[0057] The second-level signal processing circuit includes: a differential amplifier circuit, a multi-stage amplifier circuit and a bandpass filter circuit. The most obvious difference compared with the first-level signal processing circuit is that there is no feedback circuit, so the feedback signal of the logic judgment device only comes from the first-level signal processing circuit. Since the current to be measured is small, differential amplification processing is first performed during the acquisition process, and the amplified signal is passed through a bandpass filter circuit to extract the content of even harmonics, and then the relationship between the current to be measured and the even harmonics is used to calculate the value of the current to be measured by the digital signal processing circuit. In this process, the average magnetic field strength inside the magnetic core is no longer zero.

[0058] In the embodiment of the present invention, only the first-level signal processing circuit has two feedback channels, and the second-level signal processing circuit is an open-loop measurement, so the feedback signal received by the logic judgment device always comes from the first-level signal processing circuit. The logic judgment device can judge the range of the current value to be measured according to the relationship between the feedback signal and the set threshold value, thereby controlling the input and output of the power amplifier circuit to be connected to the self-excited oscillation signal generating circuit and the corresponding excitation winding coil respectively. It should be noted that although there are two excitation winding coils, there is only one power amplifier circuit. Therefore, only one excitation winding coil is in a working state at any time, and the other excitation winding coil is in an open circuit state because it is not connected to the corresponding self-excited oscillation signal generating circuit. This strategy can avoid the influence of the current generated by the alternating magnetic field in the non-working excitation winding coil on the accuracy of the measurement result.

[0059] In the embodiment of the present invention, the threshold value set in the low-power MCU in the logic judgment device is determined according to the measurement range of the sensor.

[0060] In one embodiment, the maximum value of the small current measurement range is taken as 1 / 10 of the maximum value of the measurement range, and the threshold value is the digital signal value corresponding to the maximum value of the small current measurement range. If the measurement range of the sensor is [0A, 50A], the small current measurement range of the sensor is [0A, 5A], and the large current measurement range is (5A, 50A]. The reference voltage of the low-power MCU is selected as 3.3V, and the analog-to-digital conversion channel of the MCU has a 12-bit resolution, then the analog voltage signal 0~3.3V corresponds to the digital signal value 0~4095. In the initial working state of this fluxgate current sensor, the first excitation winding coil and its corresponding self-excited oscillation signal generating circuit are connected to the power amplifier circuit, and the first-level signal processing circuit is put into operation. At this time, the sensor judges the current to be measured: the current signal to be measured in the range of 0~50A will be converted into a digital signal after passing through the first-level signal processing circuit. The voltage signal corresponding to 0~3.3V, at this time, the maximum value of 5A in the small current measurement range corresponds to a voltage signal of 0.33V. After the logic judgment device, the analog signal 0.33V will be converted into a digital signal value 409. The value of the digital signal 409 is the size of the set threshold. If the digital signal value corresponding to the feedback signal received by the logic judgment device is greater than 409, the first excitation winding coil and its corresponding self-excited oscillation signal generating circuit continue to work; if the digital signal value corresponding to the feedback signal received by the logic judgment device is less than 409, the logic judgment device controls the power amplifier circuit to be connected to the second excitation winding coil and its corresponding self-excited oscillation signal generating circuit, and the second-level signal processing circuit starts to work.

[0061] like Figure 3As shown, in the embodiment of the present invention, when the fluxgate current sensor starts to work, the logic judgment device controls the power amplifier circuit to be connected to the first excitation winding coil and its corresponding self-excited oscillation signal generating circuit. At this time, the first-level signal processing circuit starts to work, and the electrical signal collected from the first excitation winding first passes through the differential voltage stabilization circuit to eliminate the influence of noise, and then passes through the voltage divider circuit and is input into the integral amplifier circuit to obtain the integral value of the current to be measured. After the integrated electrical signal is processed by a low-pass filter, the feedback signal is input into the first excitation winding coil and the logic judgment device through the feedback loop, wherein the electrical signal fed back to the logic judgment device is used to judge the size of the current to be measured. If the feedback signal is greater than the set threshold value, it indicates that the current to be measured is If the current is large, the power amplifier circuit is still connected to the first excitation winding and its corresponding self-excited oscillation signal generating circuit, and the first-level signal processing circuit continues to work; if the feedback signal is less than the set threshold, it means that the current to be measured is a small current, and the logic judgment device will control the power amplifier circuit to disconnect from the first excitation winding and its corresponding self-excited oscillation signal generating circuit and connect the power amplifier circuit to the second excitation winding and its corresponding self-excited oscillation signal generating circuit. At this time, the second-level signal processing circuit starts to work, and the electrical signal collected from the second excitation winding first passes through the differential amplifier circuit to eliminate the influence of noise, and then amplifies the small signal through the multi-stage amplifier circuit. The amplified signal passes through the bandpass filter circuit to obtain the even harmonic content. Regardless of the first-level signal processing circuit or the second-level signal processing circuit, the signal after passing through the filter will pass through the digital signal processing circuit to finally calculate the value of the current to be measured.

[0062] In an exemplary embodiment of the present invention, the first-level signal processing circuit and the second-level signal processing circuit in the signal processing device are respectively used for measuring a larger current to be measured and a smaller current to be measured. According to the different sizes of the current to be measured, the signal acquisition and processing processes are also significantly different. When the current to be measured is a large current, the first-level signal processing circuit is in a working state, and the collected signal first passes through a differential voltage stabilization circuit to eliminate the interference of noise on the measurement, and then passes through a voltage divider circuit to reduce the voltage so as to serve as the input of the integral amplifier circuit, and finally passes through a low-pass filter circuit to obtain a DC component, and finally feeds back to the excitation winding coil and the logic through a feedback circuit. The judging device forms a closed-loop control, and finally the output signal of the low-pass filter circuit is collected by the digital signal processing circuit and the value of the current to be measured is obtained by calculation; when the current to be measured is a small current, the second-level signal processing circuit is in working state, and the collected signal first passes through the differential amplifier circuit, which not only eliminates the interference of noise on the measurement to be measured, but also amplifies the signal to be measured for subsequent measurement, and then passes through the band-pass filter circuit to obtain the even harmonics in the collected signal, and finally the output signal of the band-pass filter circuit is collected by the digital signal processing circuit, and the relationship between the DC current to be measured and the even harmonic content is used to calculate the value of the current to be measured. It can be seen that closed-loop and open-loop signal processing circuits are used for large currents and small currents respectively. This is because the influence of noise on different currents to be measured is different. For large currents to be measured, the fluctuation caused by noise is smaller than that of the current to be measured, and the influence of noise on the current to be measured is also smaller. Therefore, under the action of the differential circuit, the influence of noise can be ignored, and then fed back to the excitation winding coil after processing by the subsequent circuit. When the average magnetic field strength inside the magnetic core is zero, the measurement can be carried out. The use of closed-loop control can not only improve the stability of the system but also ensure a certain measurement accuracy. For small currents to be measured, the fluctuation caused by noise is not negligible compared to the current to be measured. Therefore, after the acquisition signal is differentially and amplified, if the closed-loop control is used to feed the processed acquisition signal back to the excitation winding coil, the average magnetic field inside the magnetic core cannot be zero due to the existence of noise and it cannot be ignored, and it will also cause the acquisition signal to be in a fluctuating state, thereby increasing the measurement error of the sensor. In order to maximize the measurement accuracy of the sensor when measuring small currents, an open-loop control measurement method is used to measure the small current to be measured.

[0063] The core processing chip of the digital signal processing circuit in the logic judgment device and the signal processing device described in the embodiment of the present invention can use the same microcontroller unit. In the embodiment of the present invention, STM32F429IGT6 is used for logic judgment and signal processing. The chip has three ADCs that can be used for logic judgment, large current signal processing and small current signal processing respectively. The three ADCs are independent of each other, so that the signal processing device of the present invention has a self-checking function. Each ADC is a 12-bit successive approximation digital-to-analog converter with a resolution of up to 2 12 The sampling frequency can reach up to 22.5MHz, ensuring a certain sampling accuracy.

[0064] In the embodiment of the present invention, the magnetic core adopts a hollow ring structure formed by alternately stacking semi-circular Permalloy sheets and full-circular Permalloy sheets. The advantage of adopting this structure is that different signal processing methods can be used for different ranges of currents to be measured, which can improve the overall measurement accuracy of the sensor. Especially in the measurement of small currents, the advantages of this magnetic core structure are more obvious; when the current to be measured is a small current, the logic judgment device will control the power amplifier circuit to be connected to the second excitation winding coil and its corresponding self-excited oscillation signal generating circuit, the second-level signal processing circuit is in a working state, and the magnetic flux density in the magnetic core on the alternating side of the full-circular Permalloy sheet and the air is greater than that of the semi-circular Permalloy sheet. The magnetic flux density in the magnetic core on the side where the gold sheets and the whole circular Permalloy sheets are alternately stacked is increased, so only a small excitation signal needs to be provided to the second excitation winding coil to meet the condition of periodic saturation of the magnetic core. By reducing the excitation signal, the asymmetry of the signal in the excitation winding coil caused by the measured current increases. Although the measured current is not fundamentally amplified, the proportion of the influence of the measured current in the collected signal is increased, which greatly facilitates the subsequent signal collection and processing, and also improves the measurement accuracy of the sensor when measuring small currents. In addition, due to the large magnetic field strength inside the magnetic core on the side where the whole circular Permalloy sheets and the gaps are alternately stacked, greater losses will be generated, and the losses caused by The temperature rise caused by this will also increase, and the increase in temperature rise will affect the characteristic parameters of the magnetic core material such as the magnetic permeability and saturation magnetic induction intensity, which will cause greater measurement errors for the fluxgate current sensor, which is already difficult to measure small currents. The structure of alternating stacking of semi-circular Permalloy sheets and full-circular Permalloy sheets can effectively reduce the loss inside the magnetic core and suppress the temperature rise to a certain extent, thereby further improving the measurement accuracy of the sensor; the magnetic core is wound with an excitation winding for measuring currents in different ranges. Compared with traditional fluxgate current sensors, the measurement range is greatly improved. At the same time, in order to avoid mutual interference between the excitation windings, the two excitation windings are connected in parallel. The excitation windings have their corresponding self-excited oscillation signal generating circuits respectively and are in a pre-connected state. The logic circuit makes a judgment based on the relationship between the feedback signal and the set threshold value, and then connects the self-excited oscillation signal generating circuit to its corresponding excitation winding coil through the power amplifier circuit. There is only one power amplifier circuit, so at any time only one excitation winding coil is connected to its corresponding self-excited oscillation signal generating circuit and is in a working state, while the other excitation winding coil is in an open circuit state because it is not connected to its corresponding self-excited oscillation signal generating circuit, and no induced current is generated inside it, thereby avoiding mutual interference between the excitation winding coils to a large extent.

[0065] For traditional fluxgate current sensors, their core structure is usually a common circular ring structure. When measuring different ranges of current to be measured, the measurement accuracy of the sensor is different, especially when the current to be measured is small. Since the magnetic field strength generated by the small current in space is weak, the magnetic field change caused by the current to be measured inside the core is also very weak. In addition, the interference of noise will seriously affect the measurement accuracy of the fluxgate current sensor, and even make it impossible to measure the current to be measured. Although the core structure formed by alternating stacking of semicircular rings and full circular rings still cannot amplify the current to be measured essentially, it can reduce the requirements for the excitation signal and achieve the purpose of amplifying the current to be measured by reducing the amplitude of the excitation signal, which not only improves the measurement accuracy of the sensor, It can also reduce the power consumption of the sensor. The increase in magnetic induction intensity will cause the eddy current loss inside the magnetic core to increase exponentially. The temperature rise of the magnetic core caused by the loss will react on the magnetic core. In severe cases, it will even affect the changes in characteristic parameters such as the magnetic permeability of the magnetic core, further affecting the measurement accuracy of the sensor. Especially when the sensor monitors the state of the lightning arrester and is in a working state for a long time, the effective control of the sensor loss can ensure the measurement accuracy of the sensor. The core structure of alternately stacked semi-circular and full-circular Permalloy sheets can effectively reduce the core loss of the fluxgate current sensor, fundamentally reducing the measurement error caused by the loss temperature rise. The basic component structure of the magnetic core is semi-circular Permalloy sheets and full-circular Permalloy sheets, which makes the magnetic core easy to manufacture and assemble.

[0066] In the process of collecting and processing the current to be measured, the collection amount and measurement method of the current in different ranges are also different; when the current to be measured is large, the first-level signal processing circuit will be in working state. Since the current to be measured itself is large, amplification processing is not required. In order to improve the measurement accuracy of the sensor, differential processing is first required to eliminate the influence of noise. The signal after differential processing is input to the integral amplifier circuit through the voltage divider circuit. The excitation signal in the signal can be filtered out through the integral circuit and the low-pass filter circuit. Finally, only the current to be measured after integration processing is fed back to the inside of the excitation winding coil through the feedback circuit. When the circuit is in a stable working state, the average magnetic induction intensity inside the magnetic core is zero; when the current to be measured is a small current, the second-level signal processing circuit will be in working state. Since the current to be measured itself is small, amplification is first required. Processing, at the same time, in order to improve the measurement accuracy of the sensor and reduce the measurement error of the sensor, it is first necessary to perform differential amplification on the collected signal, and then filter the amplified signal through a bandpass filter to extract the even harmonic components in the signal. Finally, according to the relationship between the even harmonics and the current to be measured, the value of the current to be measured is calculated by the digital signal processing circuit. It should be noted that in the processing of small currents, no closed-loop channel is formed like the large current to be measured. This is because when the current to be measured is a small current, the interference caused by noise cannot be ignored. If closed-loop control is used as the current to be measured is a large current, it is difficult to make the circuit work in a stable state, and the circuit will always be in a fluctuating state, which will lead to unreliable measurement results. In order to ensure the accuracy of the measurement, the open-loop control method is used for the processing of the small current to be measured. It is worth noting that at this time, the average magnetic field strength inside the magnetic core is no longer zero.

[0067] The material of the hollow structure magnetic core described in the embodiment of the present invention is 1J85 Permalloy with low coercive force, high magnetic permeability and easy saturation. Assuming that the magnetic permeability of the magnetic core is μ(t), during the periodic saturation process of the magnetic core, the magnetic permeability of the magnetic core changes with time. There are n1 semi-circular Permalloy sheets, n2 full-circular Permalloy sheets, the cross-sectional area of ​​each Permalloy sheet is S, the thickness is d, the volume of the magnetic core is V, the length is l, the resistivity is ρ, the first excitation winding coil has N1 turns, and the second excitation winding coil has N2 turns. When the current to be measured is a large current, the first excitation winding wound on the alternately stacked side of the semi-circular Permalloy sheets and the full-circular Permalloy sheets is in a working state, while the second excitation winding is open circuit and no current passes through. Assuming that the magnetic field strength generated by the current to be measured is H0, the magnetic field strength generated by the excitation signal is H1=H 1m cos(2πf1t), where f1 is the frequency of the excitation signal, H 1m is the amplitude of the magnetic field strength generated by the excitation signal. Under the action of the measured current and the excitation signal, the magnetic field strength inside the magnetic core on the side where the semi-circular Permalloy sheets and the full-circular Permalloy sheets are alternately stacked is:

[0068] H=H0+H 1m cos(2πf1t) (1)

[0069] Then the magnetic induction intensity inside the magnetic core on the side where the semi-circular Permalloy sheets and the full-circular Permalloy sheets are alternately stacked is:

[0070] B=μH=μ(t)·(H0+H 1m cos(2πf1t)) (2)

[0071] In order to meet the periodic saturation conditions inside the magnetic core, the maximum and minimum values ​​of B should be able to meet the positive and negative saturation conditions of the magnetic core. At this time, the magnetic flux on the alternately stacked side of the semi-circular Permalloy sheets and the full-circular Permalloy sheets inside the magnetic core is:

[0072] φ=(n1+n2)BS=(n1+n2)·μ(t)·(H0+H 1m cos(2πf1t))S (3)

[0073] Therefore, the magnetic induction intensity B1 inside the magnetic core on the alternating sides of the full-circle Permalloy sheet and the gap is:

[0074] B1=(n1+n2)B / n2 (4)

[0075] Since the condition of periodic saturation of the core is met and B1 is greater than B, the magnetic field inside the core on the alternating sides of the full-circle Permalloy sheet and the gap is oversaturated, which will cause the magnetic permeability to be too small and thus cause uneven magnetic field distribution inside the core, but this will not affect the collection and measurement of the large current to be measured.

[0076] According to the magnetic field strength, the current inside the excitation winding coil can be obtained as:

[0077] I=H1 / N1=(H0+H 1m cos(2πf1t))l / N1 (5)

[0078] From the formula, we can see the components of the current inside the excitation winding coil. After being processed by the first-level circuit, only the DC component current signal is fed back to the excitation winding coil through the feedback circuit. When the circuit is in a stable state, the current value inside the excitation winding coil will become:

[0079] I=H1 / N1=1H 1m cos(2πf1t) / N1 (6)

[0080] After stabilization, the current inside the excitation winding coil no longer has a DC part. After passing through the integral amplifier circuit in the first-level signal processing circuit, it is zero, and the feedback value is also zero. At this time, the value of the current to be measured can be obtained by the digital signal processing circuit, and the average magnetic field strength inside the magnetic core is also zero.

[0081] When the current to be measured is a small current, the second excitation winding wound on the alternating sides of the full-circular permalloy sheet and the gap is in working state. At this time, the first excitation winding is open circuit and no current passes through. Assuming that the magnetic field strength generated by the current to be measured is still H0, the magnetic field strength generated by the excitation signal is H2 = H 2m cos(2πf2t), where f2 is the frequency of the excitation signal, H 2m is the amplitude of the magnetic field strength generated by the excitation signal. Under the action of the measured current and the excitation signal, the magnetic field strength inside the full-circle Permalloy sheet and the alternating gap side magnetic core is:

[0082] H=H0+H 2m cos(2πf2t) (7)

[0083] At this time, the magnetic induction intensity inside the full-circle Permalloy sheet and the alternating gap side magnetic core is:

[0084] B=μH=μ(t)·(H0+H 2m cos(2πf2t)) (8)

[0085] In order to meet the condition of periodic saturation of the core, the maximum and minimum values ​​of B should be able to meet the positive and negative saturation of the core on the alternating sides of the full-circle Permalloy sheet and the gap. The magnetic flux on the alternating sides of the full-circle Permalloy sheet and the gap inside the core is:

[0086] φ=n2BS=n2μ(t)·(H0+H 2m cos(2πf2t))S (9)

[0087] When the core is periodically saturated, the magnetic permeability μ is a function of time and changes with the periodic change of the magnetic field strength. The frequency of μ change is twice the frequency of the excitation signal, that is, 2f2. Fourier decomposition of it yields:

[0088]

[0089] In the formula, μ 2im sin(4iπf2t) represents the relationship between the magnetic permeability corresponding to each harmonic and time.

[0090] Therefore, under the action of the alternating magnetic field, the induced electromotive force generated inside the exciting winding coil is:

[0091]

[0092] From the expression of the induced electromotive force inside the exciting winding coil, it can be seen that the even harmonic term is And it is related to the magnetic field strength generated by the current to be measured. When the current to be measured is zero, the induced electromotive force in the excitation winding coil has only odd harmonics but no even harmonics. When the current to be measured is not zero, even harmonic components will be generated in the excitation winding coil. The even harmonic content of the induced electromotive force is extracted through the second-level signal processing circuit:

[0093]

[0094] The magnitude of the magnetic field strength generated by the measured current is obtained according to the even harmonic induced electromotive force, and finally the value of the measured current is obtained according to the proportional relationship between the magnetic field strength and the measured current. It can be seen from the expression that the hollow structure magnetic core in the present invention cannot amplify the measured current, but it can be amplified by reducing the excitation signal, that is, reducing H 2m To increase the proportion of even harmonics in the induced electromotive force, thereby indirectly achieving the purpose of proportional amplification.

[0095] In the complete measurement process, the loss mainly comes from the eddy current loss and hysteresis loss of the magnetic core. The size of the loss will directly affect the temperature rise of the magnetic core, and the temperature rise will affect the characteristic parameters of the magnetic core material such as the magnetic permeability and saturation magnetic induction intensity, increasing the measurement error of the sensor. Especially when the current to be measured is a small current, the measurement error will be greater. Therefore, it is very necessary to control the core loss. The eddy current loss P inside the magnetic core w and hysteresis loss P h The relationship is:

[0096] P w ∝(f 2 d 2 B m V) / ρ (13)

[0097]

[0098] According to the loss relationship, it can be seen that the loss is related to factors such as the frequency of the excitation signal, magnetic induction intensity, material, volume and thickness of the magnetic core. The use of Permalloy sheets can reduce the thickness of the magnetic core and thus reduce the eddy current loss inside the magnetic core. The use of a magnetic core structure with alternating stacking of semi-circular and full-circular Permalloy sheets can reduce the volume of the magnetic core and thus reduce eddy current and hysteresis losses, thereby suppressing the measurement error caused by temperature rise and improving the measurement accuracy of the sensor.

[0099] In summary, the embodiment of the present invention provides a fluxgate current sensor with low power consumption, low power loss and the ability to proportionally amplify a small current to be measured. The fluxgate current sensor includes: a hollow structure magnetic core, a logic judgment device, an excitation signal generating device and a signal processing device; the magnetic core is a hollow ring structure formed by alternately stacking a semi-circular ring Permalloy sheet and a full-circular ring Permalloy sheet, on which a first and a second excitation winding coil and a corresponding signal processing device are wound, and the excitation winding coil and the signal processing device are selectively controlled according to the range of the current to be measured, and the signal processing flow adopted for the current to be measured in different ranges is different, and closed-loop control is adopted for large currents to be measured, and open-loop control is adopted for small currents to be measured. The purpose of adopting the hollow magnetic core structure is to increase the proportion of even harmonic content in the induced electromotive force when measuring a small current, so as to achieve the purpose of proportionally amplifying the current to be measured and reducing the power consumption of the sensor, and at the same time, it can reduce the excessive loss caused by the magnetic field of the full-circular ring Permalloy sheet and the alternating side of the gap, reduce the measurement error caused by the temperature rise, and further improve the measurement accuracy of the sensor.

[0100] The description of the disclosed embodiments of the present invention is only used to illustrate the technology and implementation scheme of the present invention and is not intended to limit the embodiments described herein. The general principles described in the present invention can be applied to other embodiments without departing from the spirit and scope of the present invention. Professionals and technicians in this field can modify or replace the embodiments described in the present invention, and these modifications and replacements are within the scope of protection of the pending claims of the present invention.

Claims

1. A low-power, low-loss proportionally amplified fluxgate current sensor, characterized in that: It includes a hollow-structured magnetic core, an excitation signal generating device, a signal processing device, and a logic judgment device. When the fluxgate current sensor is working, the logic judgment device automatically switches the measurement scheme according to the size of the current to be measured, wherein: The magnetic core is a hollow ring structure formed by alternately stacking half rings and full rings with the same radius but different angles, a first excitation winding for measuring large current is wound on the alternately stacked side of the half rings and full rings, and a second excitation winding for measuring small current is wound on the alternately stacked side of the full rings and gaps, wherein the half rings and full rings are electrically insulated; The excitation signal generating device comprises a first level signal processing circuit and a second level signal processing circuit, which correspond to the first excitation winding and the second excitation winding respectively; the input end of the excitation signal generating device is connected to the output end of the logic judgment device, and the output end is connected to the corresponding first excitation winding or the second excitation winding; The signal processing device comprises two level signal processing circuits, corresponding to the first excitation winding and the second excitation winding respectively, wherein the output end of the level signal processing circuit corresponding to the first excitation winding is connected to the input end of the logic judgment device and the first excitation winding; The logic judgment device automatically switches the measurement scheme according to the magnitude of the current to be measured, including: The logic judgment device controls the first excitation winding to be connected to the corresponding self-excited oscillation signal generating circuit; the first level signal processing circuit starts to work, collects the electrical signal from the first excitation winding, and feeds the processed electrical signal back to the first excitation winding and the logic judgment device; The logic judgment device judges the processed electrical signal. If it is a large current, the first excitation winding is still connected to its corresponding self-excited oscillation signal circuit, and the first-level signal processing circuit continues to work, collecting and processing the electrical signal from the first excitation winding to obtain the processed electrical signal; if it is a small current, the logic judgment device controls the first excitation winding to disconnect from its corresponding self-excited oscillation signal generating circuit, and controls the second excitation winding to connect to its corresponding self-excited oscillation signal generating circuit; the second-level signal processing circuit starts to work to collect and process the electrical signal from the second excitation winding to obtain the processed electrical signal.

2. The fluxgate current sensor according to claim 1, characterized in that: The number of turns of the first excitation winding is greater than the number of turns of the second excitation winding.

3. The fluxgate current sensor according to claim 1, characterized in that: The angles of the semicircular ring and the full-circular ring differ by 180°, and the materials are both 1J85 type Permalloy with high magnetic permeability and low coercivity.

4. The fluxgate current sensor according to claim 1, characterized in that: The signal processing device also includes a digital signal processing circuit for processing the processed electrical signal to obtain the value of the current to be measured.

5. The fluxgate current sensor according to claim 1, characterized in that: The first level signal processing circuit includes a differential voltage stabilization circuit, a voltage divider circuit, an integral amplifier circuit, a low-pass filter circuit and a dual-channel feedback circuit; When the first-level signal processing circuit is working, the electrical signal collected from the first excitation winding is passed through a differential voltage stabilization circuit to eliminate the influence of noise, and then input into the integral amplifier circuit after passing through a voltage divider circuit to obtain the integral value of the current to be measured. The integrated electrical signal is processed by a low-pass filter, and then the processed electrical signal is fed back to the first excitation winding and the logic judgment device respectively through a dual-channel feedback circuit; wherein, the signal fed back to the first excitation winding is used to offset the offset of the electrical signal in the first excitation winding caused by the current to be measured, so that the average magnetic field strength inside the magnetic core is zero; the signal fed back to the logic judgment device is used to help the logic judgment device determine the size of the current to be measured, and the excitation winding put into operation is determined according to the size of the current to be measured to be connected to the corresponding self-excited oscillation signal generating circuit and the signal processing circuit.

6. The fluxgate current sensor according to claim 1, characterized in that: The second level signal processing circuit includes a differential amplifier circuit, a multi-stage amplifier circuit and a bandpass filter circuit; When the second-level signal processing circuit is working, the electrical signal collected from the second excitation winding is eliminated by the differential amplifier circuit, and then the small signal is amplified by the multi-stage amplifier circuit. The amplified signal is passed through the bandpass filter circuit to obtain the even harmonic content.

7. The fluxgate current sensor according to claim 1, characterized in that: The logic judgment device includes a low-power MCU and a peripheral signal acquisition circuit; The peripheral signal acquisition circuit acquires the processed electrical signal; The low-power MCU performs analog-to-digital conversion on the electrical signal collected by the peripheral signal collection circuit; the magnitude of the current to be measured is determined according to the converted value and a threshold value set in the low-power MCU: if the converted value is greater than the threshold value, the current to be measured is a large current, otherwise the current to be measured is a small current; According to the determined magnitude of the current to be measured, the output signal of the low-power MCU is used as a switch control signal to connect the excitation winding put into operation to its corresponding self-excited oscillation signal generating circuit and signal processing circuit.

8. The fluxgate current sensor according to any one of claims 1 to 7, characterized in that: The excitation signal generating device also includes a power amplifying circuit; The two self-excited oscillation signal generating circuits are a first winding self-excited oscillation signal generating circuit and a second winding self-excited oscillation signal generating circuit, which correspond to the first excitation winding and the second excitation winding respectively, and are used to generate high-frequency sinusoidal wave excitation signals; The first winding self-excited oscillation signal generating circuit and the second winding self-excited oscillation signal generating circuit are both connected to the corresponding excitation winding through the power amplifier circuit.

9. A current measurement method, characterized in that: Conductor current measurement is achieved using the fluxgate current sensor as described in any one of claims 1 to 8.

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