Self-oscillation fluxgate sensor and measuring system

Abstract

The invention relates to a self-oscillation fluxgate sensor and a measuring system, and relates to the technical field of electrical variable measurement. The self-oscillation fluxgate sensor comprises a detection assembly used for being connected with a detected wire and used for sensing a detected electric signal on the detected wire; the measurement and control circuit is used for providing a control signal; the feedback filter circuit is connected with the measurement and control circuit and is used for filtering the control signal, outputting a reference signal and adjusting the output reference signal according to the reference signal and the filtered control signal; the driving excitation circuit is respectively connected with the detection assembly, the feedback filter circuit and the measurement and control circuit, and is used for carrying out self-oscillation according to the reference signal and the detected electric signal and generating excitation current; and the measurement and control circuit is also used for determining a measurement value of the measured electric signal according to the excitation current. The method can improve the measurement precision.

Description

Technical Field

[0001] The present application relates to the technical field of measuring electrical variables, and in particular to a self-excited oscillation fluxgate sensor and a measurement system. Background Art

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

[0003] The self-excited oscillation fluxgate sensor can generate an oscillation signal on its own without the need for an external oscillation source, drive the magnetic core into a periodic saturation and unsaturation state, and measure the electrical parameters of the external circuit by detecting the change in magnetic permeability. However, the traditional self-excited oscillation fluxgate sensor has a large measurement error when measuring the input signal. Summary of the invention

[0004] Based on this, it is necessary to provide a self-excited oscillation fluxgate sensor and a measurement system to improve measurement accuracy.

[0005] In a first aspect, an embodiment of the present application provides a self-excited oscillation fluxgate sensor, comprising:

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

[0007] A measurement and control circuit, used for providing a control signal;

[0008] A feedback filter circuit, connected to the measurement and control circuit, configured 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] A driving excitation circuit, connected to the detection component, the feedback filter circuit, and the measurement and control circuit, respectively, for performing self-excited oscillation according to the reference signal and the measured electrical signal, and generating an excitation current;

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

[0011] In one embodiment, the feedback filter circuit includes: a first voltage comparator, a filter module, a first resistor and a second resistor, wherein the positive input terminal of the first voltage comparator is connected to the measurement and control circuit through the filter 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 respectively connected to the output terminal of the first voltage comparator and the drive excitation circuit through the second resistor, and the filter 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 respectively connected to the first end of the third resistor and the first end of the first capacitor, the second end of the third resistor is respectively connected to the first end of the fourth resistor and the first end of the second capacitor, the second end of the fourth resistor is connected to the measurement and control circuit, and the second end of the first capacitor and the second end of the second capacitor are respectively grounded.

[0013] In one embodiment, the detection component includes a magnetic core, a primary component and a secondary component, the primary component is located on the magnetic core, the primary component is used to connect to the measured conductor, the primary component is used to sense the measured electrical signal transmitted on the measured conductor, the secondary component is located on the magnetic core, the secondary component is respectively connected to the measurement and control circuit and the drive excitation circuit, and the secondary 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 component includes a current measuring winding, the current measuring winding is wound on the magnetic core, the current measuring winding is used to connect to the measured conductor, and the current measuring winding is used to sense the measured current signal on the measured conductor; the measurement and control circuit is also used to determine the current measurement value of the measured current signal according to the excitation current when the current measuring winding is connected to the measured conductor; and / or,

[0016] The primary side component includes a voltage measurement winding and a measurement resistor, wherein the voltage measurement winding is wound on the magnetic core, and is used to be connected in series with the measured conductor through the measurement resistor, and the voltage measurement winding is used to sense the measured voltage signal on the measured conductor; the measurement and control circuit is also used to determine the voltage measurement value of the measured voltage signal according to the excitation current when the voltage measurement winding is connected to the measured conductor.

[0017] In one embodiment, the secondary side component includes an excitation winding and an excitation resistor, the excitation winding is wound on the magnetic core, and the excitation winding is connected to the measurement and control circuit and the drive excitation circuit respectively through the excitation resistor; wherein the measured value is 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 driving excitation circuit includes:

[0019] A driving excitation module, connected to the feedback filter circuit, and used to generate a driving signal according to the reference signal;

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

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

[0022] In one embodiment, the driving excitation module includes a second voltage comparator, a pulse width modulation module, a fifth switch tube and a sampling resistor, the positive input end of the second voltage comparator is respectively connected to the first end of the sampling resistor and the first pole of the fifth switch tube, the negative input end of the second voltage comparator is connected to the feedback filter circuit, the output end of the second voltage comparator is connected to the input end of the pulse width modulation module, the output end of the pulse width modulation module is connected to the gate of the fifth switch tube, the second pole of the fifth switch tube is connected to the full-bridge inverter module, and the second end of the sampling resistor is grounded; wherein the pulse width modulation module is used to generate a pulse width modulation signal according to the signal output by the second voltage comparator.

[0023] In a second aspect, an embodiment of the present application provides a measurement system, which includes: a self-excited oscillation fluxgate sensor as described above.

[0024] The above-mentioned self-excited oscillation fluxgate sensor and measurement system include a detection component, a measurement and control circuit, a feedback filter circuit and a drive excitation circuit. The detection component senses the measured electrical signal on the measured wire, and the measurement and control circuit provides a control signal. The feedback filter circuit filters the control signal and outputs a reference signal, and adjusts the output reference signal according to the reference signal and the filtered control signal. The drive excitation circuit performs self-excited oscillation and generates an excitation current according to the reference signal and the measured electrical signal, and the measurement and control circuit determines the measured value of the measured electrical signal according to 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 real-time regulated by the measurement and control signal, which helps to improve the measurement accuracy of the sensor. The control signal provided by the measurement and control signal is input into the drive excitation circuit after being processed by the feedback filter circuit, which can not only filter out noise interference, but also avoid the problem of unstable signal input to the drive excitation circuit due to signal fluctuations, thereby causing inaccurate measurement, and can further improve the measurement accuracy and stability of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

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

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

[0028] Figure 3 A schematic diagram of a hysteresis loop curve of an embodiment;

[0029] Figure 4 FIG. 4 is a schematic diagram of a curve of an excitation current according to an embodiment.

[0030] Description of reference numerals:

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

[0032] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0034] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. 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 can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0036] It can be understood that “at least one” means one or more, “plurality” means two or more, and “at least part of an element” means part or all of an element.

[0037] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0038] In one embodiment, Figure 1 As shown, a self-excited oscillation fluxgate sensor is provided, which includes 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 measured wire and to sense the measured electrical signal on the measured wire. Exemplarily, the measured electrical signal may include a measured current signal or a measured voltage signal. In application, the type of the measured electrical signal can be determined according to the actual measurement scenario, and no further limitation is made here.

[0040] The measurement and control circuit 20 is used to provide a control signal Ctrl, and the control signal Ctrl is used to control the self-excited oscillation of the driving excitation circuit 40 to achieve the measurement of the measured electrical signal. Exemplarily, the measurement and control circuit 20 includes a digital signal processing (DSP) chip, and accordingly, 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 is used to filter the control signal Ctrl and output a reference signal, and adjust the output reference signal according to the reference signal and the filtered control signal Ctrl. That is, the feedback filter circuit 30 not only has a filtering function, but also has a feedback adjustment function, so that the output reference signal is more accurate and more stable, which can not only reduce the interference caused by noise, but also avoid output instability caused by signal fluctuations.

[0042] The driving excitation circuit 40 is respectively connected to the detection component 10 and the feedback filter circuit 30. The driving excitation circuit 40 is used to perform self-excited oscillation according to the reference signal and the measured electrical signal, and generate an excitation current to make the magnetic core 110 work in a saturated state and a non-saturated state to achieve 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 according to the excitation current. Exemplarily, 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; when the measured electrical signal is a measured current signal, the measured value includes the current value of the measured current signal.

[0044] The above-mentioned self-excited oscillation 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 measured wire, and the measurement and control circuit 20 provides a control signal Ctrl, and the feedback filter circuit 30 filters the control signal Ctrl and outputs a reference signal, and adjusts the output reference signal according to the reference signal and the filtered control signal Ctrl, and the drive excitation circuit 40 performs self-excited oscillation according to the reference signal and the measured electrical signal and generates an excitation current, and the measurement and control circuit 20 performs self-excited oscillation according to the excitation current. The excitation current determines the measured value of the measured electrical signal. Since the reference signal provided to the driving excitation circuit 40 comes from the measurement and control circuit 20, the driving excitation circuit 40 can be effectively and real-time regulated through the measurement and control signal, which helps to improve the measurement accuracy of the sensor. The control signal Ctrl provided by the measurement and control signal is processed by the feedback filter circuit 30 and then input into the driving excitation circuit 40. It can not only filter out noise interference, but also avoid the problem of unstable signal input to the driving excitation circuit 40 due to signal fluctuations, which leads to inaccurate measurement, and can further improve the measurement accuracy and stability of the sensor.

[0045] In one embodiment, 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. Among them, the filter module is used to filter the control signal Ctrl to reduce noise interference and prevent the drive excitation circuit 40 from starting up incorrectly, 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 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 is used to compare the control signal Ctrl after filtering and the signal of the reference signal after voltage division by the second resistor R2, and adjust the reference signal output from the output terminal, that is, the reference signal output is adjusted by a feedback mechanism to reduce the influence of signal fluctuations, so as to improve the measurement accuracy and stability of the sensor. Exemplarily, the first voltage comparator U1C includes an LM360 comparator.

[0046] Please continue reading Figure 2In one embodiment, the filter 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 respectively connected to the first end of the third resistor R3 and the first end of the first capacitor C1, the second end of the third resistor R3 is respectively connected to the first end of the fourth resistor R4 and the first end of the second capacitor C2, the second end of the fourth resistor R4 is connected to the measurement and control circuit 20, and the second end of the first capacitor C1 and the second end of the second capacitor C2 are respectively grounded. In this way, the filter module forms a second-order low-pass filter circuit through the first capacitor C1, the second capacitor C2, the third resistor R3 and the fourth resistor R4, and utilizes the frequency-dependent properties of capacitors and resistors, and by combining their impedance characteristics, the frequency-selective attenuation of the control signal Ctrl is achieved, thereby improving the stability of the sensor.

[0047] Please continue reading Figure 2 In one embodiment, the detection component 10 includes a magnetic core 110, a primary component and a secondary component. The primary component is located on the magnetic core 110. The primary component is used to connect to the measured wire, and the primary component is used to sense the measured electrical signal transmitted on the measured wire. The secondary component is located on the magnetic core 110. The primary component and the secondary component are respectively arranged at intervals on the magnetic core 110. The secondary component is respectively connected to the measurement and control circuit 20 and the drive excitation circuit 40. The secondary component is used to transmit an excitation current. In an application, when the measured electrical signal transmitted on the primary component is not zero, the measurement and control circuit 20, the feedback filter circuit 30 and the drive excitation circuit 40 cooperate with each other to generate an excitation current in a self-excited oscillation manner, and transmit the excitation current on the secondary component, so that the excitation current can offset the magnetic flux generated by the measured electrical signal, thereby achieving the measurement of the measured electrical signal.

[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 component includes a current measurement winding 121, and / or the primary component includes a voltage measurement winding 122 and a measurement resistor R. In the application, the type of the measured electrical signal can be determined according to the measurement requirements. For example, the measured conductor can be connected to the current measurement winding 121 to achieve the measurement of the measured current signal, that is, the self-excited oscillation fluxgate sensor works in the current measurement mode; for another example, the measured conductor can be connected in series with the voltage measurement winding 122 through a measurement circuit to achieve the measurement of the measured voltage signal, that is, the self-excited oscillation fluxgate sensor works in the voltage measurement mode.

[0049] Among them, the current measuring winding 121 is wound on the magnetic core 110. In the embodiment of the present application, the number of turns of the current measuring winding 121 is recorded as N1. The current measuring winding 121 is used to be connected to the measured conductor. The current measuring winding 121 is used to sense the measured current signal on the measured conductor. The measurement and control circuit 20 is also used to determine the current measurement value of the measured current signal according to the excitation current when the current measuring winding 121 is connected to the measured conductor, which is recorded as I1. Based on this, the current measuring winding 121 can be connected to the measured conductor to achieve the measurement of the measured current signal transmitted on the measured conductor, which can be applicable to the current measurement scenario.

[0050] Among them, the primary component includes a voltage measurement winding 122 and a measuring resistor R. The measuring resistor R may include one or more and can be set according to actual needs, and is not limited too much here. The voltage measurement winding 122 is wound on the magnetic core 110. In the embodiment of the present application, the number of turns of the current measurement winding 121 is recorded as N2. The voltage measurement winding 122 is used to be connected in series with the measured conductor through the measuring resistor R. The voltage measurement winding 122 is used to sense the measured voltage signal on the measured conductor. In application, the voltage measurement winding 122 is connected to the measured conductor, and when the measured voltage signal flows through the measured conductor, a primary current I is generated through the measuring resistor R and the voltage measurement winding 122. p The measurement and control circuit 20 is also used to determine the voltage measurement value of the measured voltage signal according to the excitation current when the voltage measurement winding 122 is connected to the measured wire, which is recorded as U1. Based on this, the voltage measurement winding 122 and the measured wire can be connected to the measured wire to achieve the measurement of the measured voltage signal transmitted on the measured wire, which can be applied to voltage measurement scenarios, expand the measurement scenarios, and improve the measurement range of the sensor.

[0051] Please continue reading Figure 2 In one embodiment, the secondary component includes an excitation winding 123 and an excitation resistor Rs, wherein the excitation resistor Rs may be one or more, which is not limited here and can be set according to actual needs. In the embodiment of the present application, the number of turns of the excitation winding 123 is recorded as N L The excitation winding 123 is connected to the measurement and control circuit 20 and the driving excitation circuit 40 respectively through the excitation resistor Rs. The excitation winding 123 is used to transmit the excitation current, which can be recorded as Is. In application, the driving excitation circuit 40 self-excites to generate an alternating voltage, and 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 measured electrical signal by measuring the excitation current, thereby realizing the measurement of the measured 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. Exemplarily, when the sensor works in the current measuring mode, the current measurement value I1 of the measured current signal is negatively correlated with the number of turns N1 of the current measuring winding 121, and the current measurement value I1 is positively correlated with the number of turns N1 of the excitation winding 123. L In another exemplary embodiment, when the sensor works in the voltage measurement mode, the voltage measurement value U1 of the measured voltage signal is negatively correlated with the number of turns N2 of the voltage measurement winding 122, and the voltage measurement value U1 is positively correlated with the number of turns N2 of the excitation winding 123. L Positive correlation.

[0053] See also Figures 2 to 4 , Figure 3 is an ideal hysteresis loop, Figure 4 is the excitation current waveform. When the magnetic core 110 is working in the saturation state, when the measured electrical signal is not zero, the secondary side component will generate a magnetic field in the magnetic core 110, causing the hysteresis loop to have an overall offset, and the center line of the hysteresis loop will shift to the right. At this time, the excitation current is no longer symmetrical when the magnetic core 110 reaches saturation, and then the current in the magnetic core 110 can be obtained by measuring the current at t2 and t5, and then the measured voltage or measured current can be obtained. Figure 3 From the hysteresis loop shown, we can know that the magnetic field strength at time t1 is:

[0054] (1)

[0055] Among them, H sat represents the minimum saturation magnetic field strength of the magnetic core 110, H c represents the coercive field strength of the magnetic core 110. Taking the current measuring winding 121 as an example, N1 represents the number of coil turns of the current measuring winding 121, and I1 is the current measurement value of the measured current signal on the measured wire. According to the Ampere loop theorem, it can be obtained that:

[0056] (2)

[0057] Among them, l m is the magnetic path length of the magnetic core 110. From equations (1) and (2), we can get the excitation current I at time t1. t1 for:

[0058] (3)

[0059] During the time t1-t3, the excitation current continues to increase. However, due to the high relative magnetic permeability of the magnetic core 110, the excitation current I sThe slope is small, and the magnetic flux density B reaches zero at t2. After that, the working point of the magnetic core 110 moves from the second quadrant to the third quadrant, and the magnetic flux density B increases in the reverse direction until the magnetic core 110 reaches reverse saturation at t3. The excitation current at t3 is:

[0060] (4)

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

[0062] (5)

[0063] From time t6, the magnetic core 110 works in an unsaturated state, and:

[0064] (6)

[0065] Excitation current I t6 for:

[0066] (7)

[0067] The excitation current at time t2 is the midpoint between time t1 and time t3, and the corresponding magnetic field strength is H c , you can get I t2 The excitation current at the moment is:

[0068] (8)

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

[0070] (9)

[0071] By adding the formula, the expression of current I1 can be obtained as follows:

[0072] (10)

[0073] From the above formula, we can know 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 at time t2 is zero and the magnetic induction intensity H is a negative value, and the magnetic flux density B at time t5 is zero and the magnetic induction intensity is a positive value.

[0074] Similarly, in the 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 the current I p Multiplying by the measuring resistance R, the voltage measurement value U1 of the measured voltage signal is:

[0075] (11)

[0076] It should be noted that, in formula (11), a self-excited oscillation fluxgate sensor including two measuring resistors R is used as an example. The corresponding voltage measurement value U1 can be determined according to the actual setting, which will not be elaborated here.

[0077] Please continue reading Figure 2 In one embodiment, the driving excitation circuit 40 includes a driving excitation module 410 and a full-bridge inverter module 420. The driving excitation module 410 is connected to the feedback filter circuit 30. The driving excitation module 410 is used to generate a driving signal according to a reference signal, so as to control the working state of the full-bridge inverter module 420 through the driving signal, so that the full-bridge inverter module 420 can self-oscillate and generate an excitation current under the drive of the driving signal, thereby realizing the measurement of current or voltage.

[0078] The full-bridge inverter module 420 is connected to the drive excitation module 410 and the detection component 10 respectively. Exemplarily, 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 is used to generate an excitation current according to a drive signal, wherein the frequency of the excitation current is greater than the frequency of the measured electrical signal. The full-bridge inverter circuit drives the magnetic core 110 to operate in two states, saturation and unsaturation, under the drive of the drive signal. Specifically, the full-bridge inverter circuit changes the direction of the excitation current to make the magnetic core 110 operate in a saturated state and an unsaturated state. When the measured voltage / current is zero, the waveform of the excitation current is positively and negatively 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 the mathematical model (i.e., the aforementioned formula 10 or 11). For details, please refer to the aforementioned content, which will not be repeated here.

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

[0080] Exemplarily, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3 and the fourth switch tube Q4 may respectively include a metal-oxide-semiconductor field-effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT) or other types of switch tubes, which are not specifically limited here. Exemplarily, the first switch tube Q1 and the second switch tube Q2 are P-channel MOSFETs, which are turned on by a low gate voltage, and the third switch tube Q3 and the fourth switch tube Q4 are N-channel MOSFETs, which are turned on by a high gate voltage. The drive signal controls the opening and closing of the four switch tubes, and controls the switching action of the first switch tube Q1 and the fourth switch tube Q4, and the second switch tube Q2 and the third switch tube Q3. A low level is output during switching, and a high level is output at 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 negative on the left and positive on the right to drive the first switch tube Q1 and the fourth switch tube Q4 to turn on. When switching, the drive signal outputs a low level. According to Lenz's law, the electromotive force on the excitation winding 123 is reversed, and a signal is generated at this time to drive the second switch tube Q2 and the third switch tube Q3 to turn on.

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

[0082] In the application, the second voltage comparator U2C outputs a comparison signal by comparing the voltage on the sampling resistor R0 with the reference signal output by the feedback filter circuit 30. The comparison signal is pulse-width modulated by the pulse-width modulation module 411 and then outputs a PWM signal. The opening and closing of the fifth switch tube Q5 is controlled by the PWM signal, and the opening and closing of the first switch tube Q1 and the fourth switch tube Q4, as well as the opening and switching and switching of the second switch tube Q2 and the third switch tube Q3 are controlled by the on-off state of the fifth switch tube Q5.

[0083] Please continue reading Figure 2In one embodiment, the measurement and control circuit 20 includes a signal generating module 210, an analog-to-digital sampling module 220 and a digital processing module 230. The signal generating module 210 is connected to the feedback filtering circuit 30, and the signal generating module 210 is used to provide a control signal Ctrl. The analog-to-digital sampling module 220 is connected to the driving excitation circuit 40, and the analog-to-digital sampling module 220 is used to sample the excitation current and convert it into a digital signal. The digital processing module 220 is used to output the measured value of the measured electrical signal according to 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 by the eCAP unit 221, and the rising and falling edges of the excitation signal are captured by the external interrupt module 240, and then the ADC sampling unit 222 is turned on for sampling, and the voltage measurement value of the measured voltage signal and / or the current measurement value of the measured current signal are obtained by digitally processing the sampled excitation current. Exemplarily, the measurement and control circuit 20 includes a DSP chip, for example, the DPS chip is a TMS320F28335 chip.

[0084] Based on the same inventive concept, an embodiment of the present application further provides a measurement system, which includes a measured conductor and a self-excited oscillation fluxgate sensor, wherein the measured conductor is connected to the self-excited oscillation fluxgate sensor.

[0085] The measuring system includes a measured conductor and a self-excited oscillation fluxgate sensor, wherein the self-excited oscillation fluxgate sensor includes a detection component 10, a measurement and control circuit 20, a feedback filter circuit 30 and a drive excitation circuit 40, wherein the measured electrical signal on the measured conductor is sensed by the detection component 10, and a control signal Ctrl is provided by the measurement and control circuit 20, the control signal Ctrl is filtered by the feedback filter circuit 30 and a reference signal is output, and the output reference signal is adjusted according to the reference signal and the filtered control signal Ctrl, and the self-excited oscillation is performed according to the reference signal and the measured electrical signal and an excitation current is generated by the drive excitation circuit 40, and The measurement and control circuit 20 determines the measured value of the measured electrical signal 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 real-time regulated through the measurement and control signal, which helps to improve the measurement accuracy of the sensor and reduce the measurement error. The control signal Ctrl provided by the measurement and control signal is processed by the feedback filter circuit 30 and input to the drive excitation circuit 40, which can not only filter out noise interference, but also avoid the problem of unstable signal input to the drive excitation circuit 40 due to signal fluctuations, thereby causing inaccurate measurement, and can further improve the measurement accuracy and stability.

[0086] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0087] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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 above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A self-oscillating fluxgate sensor, characterized in that: include: A detection component, used for connecting to the wire under test and for sensing the electrical signal under test on the wire under test; A measurement and control circuit, used for providing a control signal; A feedback filter circuit, connected to the measurement and control circuit, configured 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; A driving excitation circuit, connected to the detection component, the feedback filter circuit, and the measurement and control circuit, respectively, for performing self-excited oscillation according to the reference signal and the measured electrical signal, and generating an excitation current; The measurement and control circuit is also used to determine the measured value of the measured electrical signal according to the excitation current.

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

3. The self-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, wherein the positive input terminal of the first voltage comparator is respectively connected to the first end of the third resistor and the first end of the first capacitor, the second end of the third resistor is respectively connected to the first end of the fourth resistor and the first end of the second capacitor, the second end of the fourth resistor is connected to the measurement and control circuit, and the second end of the first capacitor and the second end of the second capacitor are respectively grounded.

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

5. The self-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 component includes a current measuring winding, the current measuring winding is wound on the magnetic core, the current measuring winding is used to connect to the measured conductor, and the current measuring winding is used to sense the measured current signal on the measured conductor; the measurement and control circuit is also used to determine the current measurement value of the measured current signal according to the excitation current when the current measuring winding is connected to the measured conductor; and / or, The primary side component includes a voltage measurement winding and a measurement resistor, wherein the voltage measurement winding is wound on the magnetic core, and is used to be connected in series with the measured conductor through the measurement resistor, and the voltage measurement winding is used to sense the measured voltage signal on the measured conductor; the measurement and control circuit is also used to determine the voltage measurement value of the measured voltage signal according to the excitation current when the voltage measurement winding is connected to the measured conductor.

6. The self-oscillating fluxgate sensor according to claim 5, characterized in that: The secondary side component includes an excitation winding and an excitation resistor, the excitation winding is wound on the magnetic core, and the excitation winding is connected to the measurement and control circuit and the drive excitation circuit respectively through the excitation resistor; wherein the measurement value is respectively related to the number of turns of the current measurement winding, the voltage measurement winding, and the excitation winding.

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

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

9. The self-oscillating fluxgate sensor according to claim 7, characterized in that: The driving excitation module includes a second voltage comparator, a pulse width modulation module, a fifth switch tube and a sampling resistor, wherein the positive input end of the second voltage comparator is respectively connected to the first end of the sampling resistor and the first pole of the fifth switch tube, the negative input end of the second voltage comparator is connected to the feedback filter circuit, the output end of the second voltage comparator is connected to the input end of the pulse width modulation module, the output end of the pulse width modulation module is connected to the gate of the fifth switch tube, the second pole of the fifth switch tube is connected to the full-bridge inverter module, and the second end of the sampling resistor is grounded; wherein the pulse width modulation module is used to generate a pulse width modulation signal according to the signal output by the second voltage comparator.

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

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