Self-oscillating fluxgate sensor and measurement system

Abstract

The application relates to a self-excitation oscillation magnetic flux gate sensor and a measuring system, and relates to the technical field of measuring electric variables. The self-excitation oscillation magnetic flux gate sensor comprises a detection component connected with a measured wire and used for sensing a measured electric signal on the measured wire; a measurement and control circuit used for providing a control signal; a feedback filter circuit connected with the measurement and control circuit, used for filtering and processing the control signal and outputting a reference signal, and used for adjusting the output reference signal according to the reference signal and the filtered control signal; a driving excitation circuit connected with the detection component, the feedback filter circuit and the measurement and control circuit respectively, used for self-excitation oscillation according to the reference signal and the measured electric signal, and used for generating an excitation current; and the measurement and control circuit is further used for determining a measurement value of the measured electric signal according to the excitation current. The application can improve the measurement precision.

Description

Technical Field

[0001] This application relates to the field of electrical variable measurement technology, and in particular to a self-excited oscillating fluxgate sensor and measurement system. Background Technology

[0002] With the development of technology, sensors are widely used in various electrical and power electronic devices. Self-excited oscillating fluxgate sensors, due to their simple structure, good isolation, high accuracy, and low cost, have wide applications in power systems, industrial automation, medical equipment, and other fields.

[0003] Self-excited fluxgate sensors, without the need for an external oscillation source, can generate their own oscillation signals within their internal circuitry. This drives the magnetic core into periodic saturation and desaturation states, and the sensor measures the electrical parameters of the external circuitry by detecting changes in permeability. However, traditional self-excited fluxgate sensors suffer from significant measurement errors when measuring input signals. Summary of the Invention

[0004] Therefore, it is necessary to provide a self-excited oscillating fluxgate sensor and measurement system that can improve measurement accuracy.

[0005] In a first aspect, embodiments of this application provide a self-excited oscillating fluxgate sensor, comprising:

[0006] A detection component for connecting to the conductor under test and for sensing the electrical signal under test on the conductor under test;

[0007] Measurement and control circuits are used to provide control signals;

[0008] A feedback filtering circuit, connected to the measurement and control circuit, is used to filter the control signal and output a reference signal, and adjust the output reference signal according to the reference signal and the filtered control signal.

[0009] The driving excitation circuit is connected to the detection component, the feedback filter circuit, and the measurement and control circuit respectively, and is used to perform self-excited oscillation based on the reference signal and the measured electrical signal, and generate excitation current;

[0010] The measurement and control circuit is also used to determine the measured value of the electrical signal being measured based on the excitation current.

[0011] In one embodiment, the feedback filtering circuit includes: a first voltage comparator, a filtering module, a first resistor, and a second resistor. The positive input terminal of the first voltage comparator is connected to the measurement and control circuit through the filtering module, the negative input terminal of the first voltage comparator is grounded through the first resistor, and the negative input terminal of the first voltage comparator is connected to the output terminal of the first voltage comparator and the drive excitation circuit through the second resistor. The filtering module is used to filter the control signal.

[0012] In one embodiment, the filtering module includes a first capacitor, a second capacitor, a third resistor, and a fourth resistor, wherein the positive input terminal of the first voltage comparator is connected to the first terminal of the third resistor and the first terminal of the first capacitor, the second terminal of the third resistor is connected to the first terminal of the fourth resistor and the first terminal of the second capacitor, the second terminal of the fourth resistor is connected to the measurement and control circuit, and the second terminals of the first capacitor and the second terminals of the second capacitor are grounded.

[0013] In one embodiment, the detection component includes a magnetic core, a primary-side component, and a secondary-side component. The primary-side component is located on the magnetic core and is used to connect to the conductor under test. The primary-side component is used to sense the electrical signal transmitted on the conductor under test. The secondary-side component is located on the magnetic core and is connected to the measurement and control circuit and the drive excitation circuit, respectively. The secondary-side component is used to transmit the excitation current.

[0014] In one embodiment, the measured electrical signal includes at least one of a measured current signal and a measured voltage signal; wherein,

[0015] The primary-side component includes a current-measuring winding wound around the magnetic core. The current-measuring winding is connected to the conductor under test and is used to sense the measured current signal on the conductor under test. The measurement and control circuit is further configured to, when the current-measuring winding is connected to the conductor under test, determine the measured current value of the measured current signal based on the excitation current; and / or,

[0016] The primary-side component includes a voltage measuring winding and a measuring resistor. The voltage measuring winding is wound around the magnetic core and is connected in series with the conductor under test through the measuring resistor. The voltage measuring winding is used to sense the voltage signal under test on the conductor under test. The measurement and control circuit is also used to determine the voltage measurement value of the voltage signal under test based on the excitation current when the voltage measuring winding is connected to the conductor under test.

[0017] In one embodiment, the secondary component includes an excitation winding and an excitation resistor. The excitation winding is wound around the magnetic core and is connected to the measurement and control circuit and the drive excitation circuit through the excitation resistor, respectively. The measured values ​​are respectively related to the number of turns of the current measurement winding, the voltage measurement winding, and the excitation winding.

[0018] In one embodiment, the drive excitation circuit includes:

[0019] A drive excitation module, connected to the feedback filter circuit, is used to generate a drive signal based on the reference signal;

[0020] The full-bridge inverter module is connected to the drive excitation module and the detection component respectively, and is used to perform self-excited oscillation according to the drive signal and generate the excitation current.

[0021] In one embodiment, the full-bridge inverter module includes a voltage source, a first switch, a second switch, a third switch, and a fourth switch. The first terminal of the first switch and the first terminal of the second switch are respectively connected to the voltage source. The second terminal of the first switch is respectively connected to the first terminal of the detection component, the first terminal of the third switch, the gate of the second switch, and the gate of the fourth switch. The gate of the first switch is respectively connected to the second terminal of the detection component, the second terminal of the second switch, the gate of the third switch, and the first terminal of the fourth switch. The second terminal of the third switch is respectively connected to the second terminal of the fourth switch and the drive excitation module.

[0022] In one embodiment, the drive excitation module includes a second voltage comparator, a pulse width modulation module, a fifth switching transistor, and a sampling resistor. The positive input terminal of the second voltage comparator is connected to the first terminal of the sampling resistor and the first terminal of the fifth switching transistor, respectively. The negative input terminal of the second voltage comparator is connected to the feedback filter circuit. The output terminal of the second voltage comparator is connected to the input terminal of the pulse width modulation module. The output terminal of the pulse width modulation module is connected to the gate of the fifth switching transistor. The second terminal of the fifth switching transistor is connected to the full-bridge inverter module. The second terminal of the sampling resistor is grounded. The pulse width modulation module is used to generate a pulse width modulation signal based on the signal output by the second voltage comparator.

[0023] Secondly, embodiments of this application provide a measurement system, which includes: a self-excited fluxgate sensor as described above.

[0024] The aforementioned self-excited fluxgate sensor and measurement system includes a detection component, a measurement and control circuit, a feedback filtering circuit, and a drive excitation circuit. The detection component senses the measured electrical signal on the conductor and the measurement and control circuit provides a control signal. The feedback filtering circuit filters the control signal and outputs a reference signal. The output reference signal is adjusted based on the reference signal and the filtered control signal. The drive excitation circuit generates an excitation current through self-excited oscillation based on the reference signal and the measured electrical signal. The measurement and control circuit determines the measured value of the measured electrical signal based on the excitation current. Since the reference signal provided to the drive excitation circuit comes from the measurement and control circuit, the drive excitation circuit can be effectively and in real-time controlled, which helps improve the sensor's measurement accuracy. Furthermore, the control signal provided by the measurement and control circuit, after being processed by the feedback filtering circuit, is input to the drive excitation circuit. This not only filters out noise interference but also avoids instability caused by signal fluctuations, thus preventing measurement inaccuracies and further improving the sensor's measurement accuracy and stability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology 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.

[0026] Figure 1 This is a schematic diagram of the structure of a self-excited oscillating fluxgate sensor according to an embodiment;

[0027] Figure 2 A schematic diagram of the structure of a self-excited oscillating fluxgate sensor according to another embodiment;

[0028] Figure 3 A schematic diagram of the hysteresis loop in one embodiment;

[0029] Figure 4 This is a schematic diagram of the excitation current curve for one embodiment.

[0030] Explanation of reference numerals in the attached figures:

[0031] The system includes a detection component 10, a magnetic core 110, a current measurement winding 121, a voltage measurement winding 122, an excitation winding 123, a measurement and control circuit 20, a signal generation module 210, an analog-to-digital sampling module 220, an eCAP unit 221, an ADC sampling unit 222, a digital processing module 230, an external interrupt module 240, a feedback filter circuit 30, a drive excitation circuit 40, a drive excitation module 410, a pulse width modulation module 411, and a full-bridge inverter module 420. Detailed Implementation

[0032] 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.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0034] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0035] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0036] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0037] 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, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0038] In one embodiment, such as Figure 1 As shown, a self-excited oscillating fluxgate sensor is provided, including a detection component 10, a measurement and control circuit 20, a feedback filter circuit 30, and a drive excitation circuit 40.

[0039] The detection component 10 is used to connect to the conductor under test and to sense the electrical signal under test on the conductor. For example, the electrical signal under test may include a current signal or a voltage signal. In applications, the type of electrical signal under test can be determined according to the actual measurement scenario, and no further limitations are made here.

[0040] The measurement and control circuit 20 provides a control signal Ctrl, which controls the self-oscillation of the drive excitation circuit 40 to achieve the measurement of the electrical signal under test. For example, the measurement and control circuit 20 includes a digital signal processing (DSP) chip, and correspondingly, the control signal Ctrl includes a digital control signal Ctrl, that is, the digital control signal Ctrl is provided by the DSP chip.

[0041] The feedback filter circuit 30 is connected to the measurement and control circuit 20. The feedback filter circuit 30 filters the control signal Ctrl and outputs a reference signal, adjusting the output reference signal based on the reference signal and the filtered control signal Ctrl. In other words, the feedback filter circuit 30 not only has filtering functionality but also feedback adjustment functionality, making the output reference signal more accurate and stable. This not only reduces interference caused by noise but also prevents output instability due to signal fluctuations.

[0042] The drive excitation circuit 40 is connected to the detection component 10 and the feedback filter circuit 30, respectively. The drive excitation circuit 40 is used to perform self-excited oscillation based on the reference signal and the measured electrical signal, and generate an excitation current to make the magnetic core 110 work in saturation and unsaturation states, so as to realize the measurement of the measured electrical signal.

[0043] The measurement and control circuit 20 is also used to determine the measured value of the measured electrical signal based on the excitation current. For example, the measured value includes a current value or a voltage value, wherein, when the measured electrical signal is a measured voltage signal, the measured value includes the voltage value of the measured voltage signal; and when the measured electrical signal is a measured current signal, the measured value includes the current value of the measured current signal.

[0044] The aforementioned self-excited fluxgate sensor includes a detection component 10, a measurement and control circuit 20, a feedback filter circuit 30, and a drive excitation circuit 40. The detection component 10 senses the measured electrical signal on the conductor, and the measurement and control circuit 20 provides a control signal Ctrl. The feedback filter circuit 30 filters the control signal Ctrl and outputs a reference signal. The output reference signal is adjusted based on the reference signal and the filtered control signal Ctrl. The drive excitation circuit 40 performs self-excited oscillation based on the reference signal and the measured electrical signal to generate an excitation current. The measurement and control circuit 20 then adjusts the excitation current according to the excitation signal. The excitation current determines the measured value of the electrical signal being measured. Since the reference signal provided to the drive excitation circuit 40 comes from the measurement and control circuit 20, the drive excitation circuit 40 can be effectively and in real time controlled through the measurement and control signal, which helps to improve the measurement accuracy of the sensor. Furthermore, the control signal Ctrl provided by the measurement and control signal is processed by the feedback filter circuit 30 and then input to the drive excitation circuit 40. This not only filters out noise interference but also avoids the problem of inaccurate measurement caused by signal fluctuations leading to unstable signals input to the drive excitation circuit 40. This further improves the measurement accuracy and stability of the sensor.

[0045] In one embodiment, such as Figure 2 As shown, the feedback filter circuit 30 includes a first voltage comparator U1C, a filter module, a first resistor R1, and a second resistor R2. The filter module filters the control signal Ctrl to reduce noise interference and prevent the drive excitation circuit 40 from malfunctioning, thereby improving the accuracy and stability of the sensor. The positive input terminal of the first voltage comparator U1C is connected to the measurement and control circuit 20 through the filter module, the negative input terminal of the first voltage comparator U1C is grounded through the first resistor R1, and the negative input terminal of the first voltage comparator U1C is connected to both the output terminal of the first voltage comparator U1C and the drive excitation circuit 40 through the second resistor R2. The first voltage comparator U1C compares the filtered control signal Ctrl with the reference signal after it has been divided by the second resistor R2, adjusting the reference signal output. That is, a feedback mechanism is used to adjust the output reference signal, reducing the impact of signal fluctuations and improving the measurement accuracy and stability of the sensor. For example, the first voltage comparator U1C includes an LM360 comparator.

[0046] Please continue reading. Figure 2In one embodiment, the filtering module includes a first capacitor C1, a second capacitor C2, a third resistor R3, and a fourth resistor R4. The positive input terminal of the first voltage comparator U1C is connected to the first terminal of the third resistor R3 and the first terminal of the first capacitor C1. The second terminal of the third resistor R3 is connected to the first terminal of the fourth resistor R4 and the first terminal of the second capacitor C2. The second terminal of the fourth resistor R4 is connected to the measurement and control circuit 20. The second terminals of the first capacitor C1 and the second capacitor C2 are grounded. Thus, the filtering module, through the first capacitor C1, the second capacitor C2, the third resistor R3, and the fourth resistor R4, forms a second-order low-pass filter circuit. Utilizing the frequency-dependent properties of capacitors and resistors, and by combining their impedance characteristics, it achieves frequency-selective attenuation of the control signal Ctrl, improving sensor stability.

[0047] Please continue reading. Figure 2 In one embodiment, the detection component 10 includes a magnetic core 110, a primary-side component, and a secondary-side component. The primary-side component is located on the magnetic core 110. It is used to connect to the conductor under test and to sense the electrical signal transmitted on the conductor. The secondary-side component is also located on the magnetic core 110. The primary and secondary-side components are spaced apart on the magnetic core 110. The secondary-side component is connected to the measurement and control circuit 20 and the drive excitation circuit 40. It is used to transmit excitation current. In application, when the electrical signal transmitted on the primary-side component is not zero, the measurement and control circuit 20, the feedback filter circuit 30, and the drive excitation circuit 40 cooperate to generate an excitation current through self-excited oscillation. This excitation current is then transmitted on the secondary-side component, allowing it to cancel the magnetic flux generated by the electrical signal under test, thereby achieving the measurement of the electrical signal under test.

[0048] Please continue reading. Figure 2 In one embodiment, the measured electrical signal includes at least one of a measured current signal and a measured voltage signal. The primary-side component includes a current measuring winding 121, and / or, the primary-side component includes a voltage measuring winding 122 and a measuring resistor R. In application, the type of measured electrical signal can be determined according to measurement requirements. For example, the measured wire can be connected to the current measuring winding 121 to measure the measured current signal; that is, the self-excited fluxgate sensor operates in current measurement mode. Alternatively, the measured wire can be connected in series with the voltage measuring winding 122 through a measuring circuit to measure the measured voltage signal; that is, the self-excited fluxgate sensor operates in voltage measurement mode.

[0049] In this embodiment, the current measuring winding 121 is wound around the magnetic core 110. The number of turns in the current measuring winding 121 is denoted as N1. The current measuring winding 121 is used to connect to the conductor under test. The current measuring winding 121 is used to sense the measured current signal on the conductor under test. The measurement and control circuit 20 is also used to determine the measured current value of the measured current signal, denoted as I1, based on the excitation current when the current measuring winding 121 is connected to the conductor under test. Therefore, by connecting the current measuring winding 121 to the conductor under test, the measurement of the measured current signal transmitted on the conductor under test can be realized, which is applicable to current measurement scenarios.

[0050] The primary-side component includes a voltage measuring winding 122 and a measuring resistor R. The measuring resistor R can include one or more components, and can be set according to actual needs; no further limitations are made here. The voltage measuring winding 122 is wound around the magnetic core 110. In this embodiment, the number of turns of the current measuring winding 121 is denoted as N2. The voltage measuring winding 122 is connected in series with the conductor under test through the measuring resistor R. The voltage measuring winding 122 is used to sense the voltage signal to be measured on the conductor under test. In application, the voltage measuring winding 122 is connected to the conductor under test. When the voltage signal to be measured flows through the conductor under test, a primary-side current I is generated through the measuring resistor R and the voltage measuring winding 122. p The measurement and control circuit 20 is also used to determine the voltage measurement value of the voltage signal to be measured, denoted as U1, based on the excitation current when the voltage measurement winding 122 is connected to the conductor under test. Based on this, the voltage signal transmitted on the conductor under test can be measured by connecting the voltage measurement winding 122 and the conductor under test. This is applicable to voltage measurement scenarios, expands the measurement scope, and improves the sensor's measurement range.

[0051] Please continue reading. Figure 2 In one embodiment, the secondary-side component includes an excitation winding 123 and an excitation resistor Rs. The excitation resistor Rs can be one or more, and is not limited here; it can be set according to actual needs. In this embodiment, the number of turns of the excitation winding 123 is denoted as N. L The excitation winding 123 is connected to the measurement and control circuit 20 and the drive excitation circuit 40 through the excitation resistor Rs. The excitation winding 123 is used to transmit the excitation current, which can be denoted as Is. In application, the drive excitation circuit 40 generates an alternating voltage through self-excited oscillation, which generates an excitation current through the excitation resistor Rs and the excitation winding. The measurement and control circuit 20 determines the measured value of the electrical signal by measuring the excitation current, thereby realizing the measurement of the electrical signal.

[0052] The measured values ​​are respectively related to the number of turns of the current measuring winding 121, the voltage measuring winding 122, and the excitation winding 123. For example, when the sensor operates in current measuring mode, the measured current value I1 of the measured current signal is negatively correlated with the number of turns N1 of the current measuring winding 121, and the measured current value I1 is also negatively correlated with the number of turns N1 of the excitation winding 123. L Positive correlation. As another example, when the sensor operates in voltage measurement mode, the measured voltage value U1 of the measured voltage signal is negatively correlated with the number of turns N2 of the voltage measurement winding 122, and the measured voltage value U1 is negatively correlated with the number of turns N of the excitation winding 123. L Positive correlation.

[0053] Please see Figures 2 to 4 , Figure 3 For an ideal hysteresis loop, Figure 4 This is the excitation current waveform. When the magnetic core 110 operates in saturation, and the measured electrical signal is not zero, the secondary-side components generate a magnetic field in the magnetic core 110, causing a general shift in the hysteresis loop. The center line of the hysteresis loop shifts to the right. At this point, the excitation current is no longer symmetrical when the magnetic core 110 reaches saturation. Therefore, the current in the magnetic core 110 can be obtained by measuring the current at times t2 and t5, thus yielding the measured voltage or current. Figure 3 The hysteresis loop shown indicates that the magnetic field strength at time t1 is:

[0054] (1)

[0055] Among them, H sat H represents the minimum saturation magnetic field strength of magnetic core 110. c This represents the coercive field strength of the magnetic core 110. Taking the current measuring winding 121 as an example, N1 represents the number of turns of the current measuring winding 121, and I1 is the measured current value of the measured current signal on the measured conductor. From Ampere's circuital law, we can obtain:

[0056] (2)

[0057] Among them, l m Given the magnetic circuit length of the magnetic core 110, from equations (1) and (2), the excitation current I at time t1 can be obtained. t1 for:

[0058] (3)

[0059] During the time interval t1-t3, the excitation current continuously increases, but due to the high relative permeability of the 110 magnetic core, the excitation current I... sWith a small slope, the magnetic flux density B reaches zero at time t2. Afterward, the operating point of magnetic core 110 shifts from the second quadrant to the third quadrant, and the magnetic flux density B increases in the reverse direction until time t3 when magnetic core 110 reaches reverse saturation. The excitation current at time t3 is:

[0060] (4)

[0061] The excitation current during the time interval t4-t6 is opposite to that during the time interval t1-t3. At time t5, the magnetic flux density B reaches zero, after which the magnetic core 110 operates in the first quadrant. According to Ampere's circuital law, the magnitude of the excitation current at time t4 is:

[0062] (5)

[0063] From time t6 onwards, magnetic core 110 operates in an unsaturated state, with the following:

[0064] (6)

[0065] Excitation current I t6 for:

[0066] (7)

[0067] The excitation current at time t2 is the midpoint between times t1 and t3, and the corresponding magnetic field strength at this time is H. c , can obtain I t2 The excitation current at time t is:

[0068] (8)

[0069] Similarly, the magnetic field strength at point t5 is -H c We can get I t5 The excitation current at time t is:

[0070] (9)

[0071] By adding the equations together, we can obtain the expression for the current I1 as follows:

[0072] (10)

[0073] From the above equation, it can be seen that by measuring the excitation current I at time t2... t2 and the excitation current I at time t5 t5 The measured current I1 can be obtained, where the magnetic flux density B is zero and the magnetic induction intensity H is negative at time t2, and the magnetic flux density B is zero and the magnetic induction intensity is positive at time t5.

[0074] Similarly, in a voltage measurement scenario, for the measured voltage signal U1 on the voltage measurement winding 122, the current I on the voltage measurement winding 122 can be calculated by referring to the above process. p Then use current I p Multiplying the measured resistance R, the voltage measurement value U1 of the measured voltage signal is:

[0075] (11)

[0076] It should be noted that formula (11) takes the self-excited oscillating fluxgate sensor including two measuring resistors R as an example. The specific voltage measurement value U1 can be determined according to the actual settings, which will not be elaborated here.

[0077] Please continue reading. Figure 2 In one embodiment, the drive excitation circuit 40 includes a drive excitation module 410 and a full-bridge inverter module 420. The drive excitation module 410 is connected to the feedback filter circuit 30. The drive excitation module 410 generates a drive signal based on a reference signal, thereby controlling the operating state of the full-bridge inverter module 420. This enables the full-bridge inverter module 420 to self-oscillate and generate an excitation current under the drive signal, thus achieving current or voltage measurement.

[0078] The full-bridge inverter module 420 is connected to the drive excitation module 410 and the detection component 10. For example, the detection component 10 includes an excitation winding 123 and an excitation resistor Rs, wherein the full-bridge inverter module 420 is connected to the excitation winding 123 through the excitation resistor Rs. The full-bridge inverter module 420 generates an excitation current based on a drive signal, wherein the frequency of the excitation current is greater than the frequency of the measured electrical signal. Under the drive signal, the full-bridge inverter circuit causes the magnetic core 110 to operate in both saturated and unsaturated states. Specifically, the full-bridge inverter circuit changes the direction of the excitation current to cause the magnetic core 110 to operate in saturated and unsaturated states. When the measured voltage / current is zero, the waveform of the excitation current is symmetrical. When the measured voltage / current is not zero, the waveform of the excitation current is no longer symmetrical, and the measured voltage value U1 or the measured current value I1 can be obtained according to a mathematical model (i.e., the aforementioned formula 10 or 11), as detailed above.

[0079] Please continue reading. Figure 2In one embodiment, the full-bridge inverter module 420 includes a voltage source Vcc, a first switch Q1, a second switch Q2, a third switch Q3, and a fourth switch Q4. The voltage source Vcc provides a power signal. The first terminals of the first switch Q1 and the second switch Q2 are connected to the voltage source Vcc. The second terminal of the first switch Q1 is connected to the first terminal of the secondary-side component, the first terminal of the third switch Q3, the gate of the second switch Q2, and the gate of the fourth switch Q4. The gate of the first switch Q1 is connected to the second terminal of the secondary-side component, the second terminal of the second switch Q2, the gate of the third switch Q3, and the first terminal of the fourth switch Q4. The second terminal of the third switch Q3 is connected to the second terminal of the fourth switch Q4 and the drive excitation module 410. Figure 2 Taking the structure shown as an example, one end of the excitation winding 123 is connected to the second terminal of the first switch Q1, the first terminal of the third switch Q3, the gate of the second switch Q2, and the gate of the fourth switch Q4 through a measuring resistor R. The other end of the excitation winding 123 is connected to the gate of the first switch Q1, the second terminal of the second switch Q2, the gate of the third switch Q3, and the first terminal of the fourth switch Q4 through another measuring resistor R.

[0080] For example, the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 can each include a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), an Insulated-Gate Bipolar Transistor (IGBT), or other types of switches, without specific limitations. For example, the first switch Q1 and the second switch Q2 are both P-channel MOSFETs, turned on at low gate voltage, while the third switch Q3 and the fourth switch Q4 are both N-channel MOSFETs, turned on at high gate voltage. The drive signal controls the switching of the four switches and controls the commutation of the first switch Q1 and the fourth switch Q4 with the second switch Q2 and the third switch Q3. A low level is output during commutation, and a high level is output at all other times. When the measured electrical signal is not zero, the magnetic core 110 generates a magnetic field strength, and the excitation winding 123 induces an electromotive force with the left side being negative and the right side being positive, driving the first switch Q1 and the fourth switch Q4 to conduct. During commutation, the drive signal outputs a low level. According to Lenz's law, the electromotive force on the excitation winding 123 is reversed, and at this time a signal is generated to drive the second switch Q2 and the third switch Q3 to conduct.

[0081] Please continue reading. Figure 2In one embodiment, the drive excitation module 410 includes a second voltage comparator U2C, a pulse width modulation module 411, a fifth switch Q5, and a sampling resistor R0. The positive input terminal of the second voltage comparator U2C is connected to the first terminal of the sampling resistor R0 and the first terminal of the fifth switch Q5, respectively. The negative input terminal of the second voltage comparator U2C is connected to the feedback filter circuit 30. The output terminal of the second voltage comparator U2C is connected to the input terminal of the pulse width modulation module 411. The output terminal of the pulse width modulation module 411 is connected to the gate of the fifth switch Q5. The second terminal of the fifth switch Q5 is connected to the full-bridge inverter module 420. The second terminal of the sampling resistor R0 is grounded. The pulse width modulation module 411 is used to generate a pulse width modulation (PWM) signal based on the signal output by the second voltage comparator U2C. For example, the second voltage comparator U2C includes an LM360 comparator.

[0082] In the application, the second voltage comparator U2C compares the voltage across the sampling resistor R0 with the reference signal output by the feedback filter circuit 30 to output a comparison signal. The comparison signal is pulse-width modulated by the pulse width modulation module 411 to output a PWM signal. The PWM signal controls the switching on and off of the fifth switch Q5. The switching on and off state of the fifth switch Q5 controls the switching on and off and commutation of the first switch Q1, the fourth switch Q4, the second switch Q2, and the third switch Q3.

[0083] Please continue reading. Figure 2In one embodiment, the measurement and control circuit 20 includes a signal generation module 210, an analog-to-digital sampling module 220, and a digital processing module 230. The signal generation module 210 is connected to the feedback filter circuit 30 and provides a control signal Ctrl. The analog-to-digital sampling module 220 is connected to the drive excitation circuit 40 and samples the excitation current and converts it into a digital signal. The digital processing module 220 outputs the measured value of the measured electrical signal based on the digital signal. Exemplarily, the analog-to-digital sampling module 220 includes an eCAP (electronic circuit analysis program) unit 221 and an ADC (analog-to-digital converter) sampling unit 222. Exemplarily, the measurement and control circuit 20 may also include an external interrupt module 240. In the application, the period of the excitation signal applied to both ends of the magnetic core 110 is obtained through the eCAP unit 221, and the edges of the rising and falling edges of the excitation signal are captured by the external interrupt module 240. Then, the ADC sampling unit 222 is activated for sampling. The voltage measurement value of the measured voltage signal and / or the current measurement value of the measured current signal are obtained by digital processing of the sampled excitation current. For example, the measurement and control circuit 20 includes a DSP chip, such as a TMS320F28335 chip.

[0084] Based on the same inventive concept, this application also provides a measurement system, which includes a test lead and a self-excited oscillating fluxgate sensor, wherein the test lead is connected to the self-excited oscillating fluxgate sensor.

[0085] The measurement system includes a test conductor and a self-excited fluxgate sensor. The self-excited fluxgate sensor includes a detection component 10, a measurement and control circuit 20, a feedback filter circuit 30, and a drive excitation circuit 40. The detection component 10 senses the measured electrical signal on the test conductor, and the measurement and control circuit 20 provides a control signal Ctrl. The feedback filter circuit 30 filters the control signal Ctrl and outputs a reference signal. The output reference signal is adjusted based on the reference signal and the filtered control signal Ctrl. The drive excitation circuit 40 performs self-excited oscillation based on the reference signal and the measured electrical signal to generate an excitation current. The measurement and control circuit 20 determines the measured value of the electrical signal being measured based on the excitation current. Since the reference signal provided to the drive excitation circuit 40 comes from the measurement and control circuit 20, the drive excitation circuit 40 can be effectively and in real time controlled through the measurement and control signal. This helps to improve the sensor measurement accuracy and reduce measurement error. Furthermore, the control signal Ctrl provided by the measurement and control signal is processed by the feedback filter circuit 30 and then input to the drive excitation circuit 40. This not only filters out noise interference but also avoids the problem of inaccurate measurement caused by signal fluctuations leading to unstable signals input to the drive excitation circuit 40. This further improves the measurement accuracy and stability.

[0086] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is 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.

[0087] 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 in 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.

[0088] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this 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 modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A self-excited oscillating fluxgate sensor, characterized in that, include: A detection component for connecting to the conductor under test and for sensing the electrical signal under test on the conductor under test; Measurement and control circuits are used to provide control signals; A feedback filtering circuit, connected to the measurement and control circuit, is used to filter the control signal and output a reference signal, and adjust the output reference signal according to the reference signal and the filtered control signal. The driving excitation circuit is connected to the detection component, the feedback filter circuit, and the measurement and control circuit respectively, and is used to perform self-excited oscillation based on the reference signal and the measured electrical signal, and generate excitation current; The measurement and control circuit is also used to determine the measured value of the electrical signal being measured based on the excitation current.

2. The self-excited oscillating fluxgate sensor according to claim 1, characterized in that, The feedback filtering circuit includes: a first voltage comparator, a filtering module, a first resistor, and a second resistor. The positive input terminal of the first voltage comparator is connected to the measurement and control circuit through the filtering module. The negative input terminal of the first voltage comparator is grounded through the first resistor. The negative input terminal of the first voltage comparator is connected to the output terminal of the first voltage comparator and the drive excitation circuit through the second resistor. The filtering module is used to filter the control signal.

3. The self-excited oscillating fluxgate sensor according to claim 2, characterized in that, The filtering module includes a first capacitor, a second capacitor, a third resistor, and a fourth resistor. The positive input terminal of the first voltage comparator is connected to the first terminal of the third resistor and the first terminal of the first capacitor. The second terminal of the third resistor is connected to the first terminal of the fourth resistor and the first terminal of the second capacitor. The second terminal of the fourth resistor is connected to the measurement and control circuit. The second terminals of the first capacitor and the second terminals of the second capacitor are grounded.

4. The self-excited oscillating fluxgate sensor according to any one of claims 1-3, characterized in that, The detection component includes a magnetic core, a primary-side component, and a secondary-side component. The primary-side component is located on the magnetic core and is used to connect to the conductor under test. The primary-side component is used to sense the electrical signal transmitted on the conductor under test. The secondary-side component is located on the magnetic core and is connected to the measurement and control circuit and the drive excitation circuit, respectively. The secondary-side component is used to transmit the excitation current.

5. The self-excited oscillating fluxgate sensor according to claim 4, characterized in that, The measured electrical signal includes at least one of a measured current signal and a measured voltage signal; wherein... The primary-side component includes a current-measuring winding wound around the magnetic core. The current-measuring winding is connected to the conductor under test and is used to sense the measured current signal on the conductor under test. The measurement and control circuit is further configured to, when the current-measuring winding is connected to the conductor under test, determine the measured current value of the measured current signal based on the excitation current; and / or, The primary-side component includes a voltage measuring winding and a measuring resistor. The voltage measuring winding is wound around the magnetic core and is connected in series with the conductor under test through the measuring resistor. The voltage measuring winding is used to sense the voltage signal under test on the conductor under test. The measurement and control circuit is also used to determine the voltage measurement value of the voltage signal under test based on the excitation current when the voltage measuring winding is connected to the conductor under test.

6. The self-excited oscillating fluxgate sensor according to claim 5, characterized in that, The secondary component includes an excitation winding and an excitation resistor. The excitation winding is wound around the magnetic core and is connected to the measurement and control circuit and the drive excitation circuit through the excitation resistor. The measured values ​​are respectively related to the number of turns of the current measurement winding, the voltage measurement winding, and the excitation winding.

7. The self-excited oscillating fluxgate sensor according to any one of claims 1-3, characterized in that, The drive excitation circuit includes: A drive excitation module, connected to the feedback filter circuit, is used to generate a drive signal based on the reference signal; The full-bridge inverter module is connected to the drive excitation module and the detection component respectively, and is used to perform self-excited oscillation according to the drive signal and generate the excitation current.

8. The self-excited oscillating fluxgate sensor according to claim 7, characterized in that, The full-bridge inverter module includes a voltage source, a first switch, a second switch, a third switch, and a fourth switch. The first terminal of the first switch and the first terminal of the second switch are respectively connected to the voltage source. The second terminal of the first switch is respectively connected to the first terminal of the detection component, the first terminal of the third switch, the gate of the second switch, and the gate of the fourth switch. The gate of the first switch is respectively connected to the second terminal of the detection component, the second terminal of the second switch, the gate of the third switch, and the first terminal of the fourth switch. The second terminal of the third switch is respectively connected to the second terminal of the fourth switch and the drive excitation module.

9. The self-excited oscillating fluxgate sensor according to claim 7, characterized in that, The drive excitation module includes a second voltage comparator, a pulse width modulation module, a fifth switching transistor, and a sampling resistor. The positive input terminal of the second voltage comparator is connected to the first terminal of the sampling resistor and the first terminal of the fifth switching transistor. The negative input terminal of the second voltage comparator is connected to the feedback filter circuit. The output terminal of the second voltage comparator is connected to the input terminal of the pulse width modulation module. The output terminal of the pulse width modulation module is connected to the gate of the fifth switching transistor. The second terminal of the fifth switching transistor is connected to the full-bridge inverter module. The second terminal of the sampling resistor is grounded. The pulse width modulation module is used to generate a pulse width modulation signal based on the signal output by the second voltage comparator.

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

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