Magnetic field resonance principle-based low-frequency power filter

Abstract

The present application relates to the technical field of filters, in particular to a magnetic field resonance principle-based low-frequency power filter. The filter comprises at least one resonance unit, the resonance unit comprising a first iron core, a first winding and a first capacitor, the first winding being wound on the first iron core, and the first winding being connected to the first capacitor in series. The material of the first iron core is a magnetic conductive material. An end part of the first iron core is provided with a magnetic circuit interface A, a magnetic circuit interface B, a magnetic circuit interface C and a magnetic circuit interface D, an air gap being formed between the magnetic circuit interface B and the magnetic circuit interface C. The magnetic field resonance principle-based low-frequency power filter provided by the present application can achieve band-pass filtering and band-stop filtering for high voltage, large current and medium-low-frequency current and voltage, thus overcoming the defects of existing filters.

Description

Low-frequency power filter based on magnetic field resonance principle Technical Field

[0001] The present application relates to the field of filter technology, and in particular to a low-frequency power filter based on the magnetic field resonance principle. Background Art

[0002] Existing analog filters primarily consist of capacitors and inductors connected in series and parallel, utilizing the electrical energy storage properties of capacitors and inductors (rather than magnetic field energy) to filter voltage or current. These analog filters suffer from large size, numerous components, and high power consumption. Therefore, in high-power applications, they typically rely on simple low-pass filters, making it difficult to implement high-pass or band-pass filters.

[0003] Existing filtering methods achieve resonance between parasitic inductance and capacitance by designing the filter's material structure. However, since the values ​​of parasitic capacitance and inductance are typically very small, they can only be used in high-frequency applications. Furthermore, due to their typically delicate structures, they struggle to withstand high voltage and high current conditions. Consequently, existing analog filtering methods can only achieve bandpass and bandstop filtering for high-frequency, low-power signals. For high-voltage, high-current, and medium-to-low-frequency power-level energy flows, low-pass filtering is typically achieved through inductance. Bandpass or bandstop filtering of high-voltage, high-current, and medium-to-low-frequency power-level voltages and currents is unavailable.

[0004] Summary of the Invention

[0005] The embodiment of the present application provides a low-frequency power filter based on the magnetic field resonance principle, which can achieve band-pass filtering and band-stop filtering of high voltage, large current, medium and low frequency current and voltage, making up for the shortcomings of existing filters.

[0006] In order to solve the above technical problems, an embodiment of the present application provides a low-frequency power filter based on the principle of magnetic field resonance, including: at least one resonant unit; the resonant unit includes a first iron core, a first winding and a first capacitor; wherein the first winding is wound around the first iron core, and the first winding is connected in series with the first capacitor; the material of the first iron core is a magnetic conductive material; the end of the first iron core is provided with a magnetic circuit interface A, a magnetic circuit interface B, a magnetic circuit interface C and a magnetic circuit interface D, and there is an air gap between the magnetic circuit interface B and the magnetic circuit interface C.

[0007] In some exemplary embodiments, when the external magnetic field flows into the first iron core from the magnetic circuit interface A or the magnetic circuit interface D, the magnetic field passes through the first winding to form a first magnetic circuit; when the first magnetic circuit flows through the first winding, part of the leakage magnetic field in the magnetic field flows from the magnetic circuit interface B to the magnetic circuit interface C, forming a second magnetic circuit, and at the same time charging the first winding, and the energized first winding resonates with the first capacitor.

[0008] In some exemplary embodiments, the first iron core includes a first protrusion and a second protrusion relatively arranged, the magnetic circuit interface B is arranged on the first protrusion, the magnetic circuit interface A is arranged at the end of the first iron core near the magnetic circuit interface B, the magnetic circuit interface C is arranged on the second protrusion, and the magnetic circuit interface D is arranged at the end of the first iron core near the magnetic circuit interface C.

[0009] In some exemplary embodiments, the first core includes a first sub-core, a second sub-core and a third sub-core, and the two ends of the second sub-core are respectively connected to the first sub-core and the third sub-core; the first sub-core and the third sub-core are arranged opposite to each other, the first winding is wound around the third sub-core, and there is an air gap between the first sub-core and the third sub-core; the magnetic circuit interface A is arranged at the end of the first sub-core, the magnetic circuit interface B is arranged on the side wall of the first sub-core facing the third sub-core, the magnetic circuit interface C is arranged on the side wall of the third sub-core facing the first sub-core, and the magnetic circuit interface D is arranged at the end of the third sub-core.

[0010] In some exemplary embodiments, the first core includes a first sub-core, a second sub-core, a third sub-core and a fourth sub-core, the two ends of the second sub-core are respectively connected to the first sub-core and the third sub-core, the fourth sub-core is located between the first sub-core and the third sub-core, and the end of the fourth sub-core is connected to the middle of the second sub-core; the first sub-core and the third sub-core are symmetrical about the longitudinal center axis of the fourth sub-core, the first winding is wound around the fourth sub-core, and there is an air gap between the fourth sub-core and the first sub-core, and between the fourth sub-core and the third sub-core; the end of the first sub-core and the end of the third sub-core are both provided with a magnetic circuit interface A, the side wall of the first sub-core and the side wall of the third sub-core are both provided with a magnetic circuit interface B, the end of the fourth sub-core is provided with a magnetic circuit interface D, and the side wall of the fourth sub-core facing the first sub-core and the side wall facing the third sub-core are both provided with a magnetic circuit interface C.

[0011] In some exemplary embodiments, the first core includes a first sub-core, a second sub-core and a third sub-core, the first sub-core is an annular structure, and the ends of the first sub-core and the third sub-core are both connected to the second sub-core; the first winding is wound around the third sub-core, and there is an air gap between the third sub-core and the annular first sub-core; a magnetic circuit interface A is provided on the annular end of the first sub-core, a magnetic circuit interface B is provided on the annular side wall of the first sub-core, a magnetic circuit interface C is provided on the side wall of the third sub-core, and a magnetic circuit interface D is provided on the end of the third sub-core.

[0012] In some exemplary embodiments, the low-frequency power filter based on the magnetic field resonance principle further includes: a second iron core, on which a second winding is wound; the second winding includes two input ports, and the input ports are used to connect the AC signal of the voltage or current to be filtered; a magnetic circuit interface D is provided at the connection between the first iron core and the second iron core, and a magnetic circuit interface E is provided on the top side wall of the second iron core away from the first iron core; when the AC current flows into the second winding from both ends of the second winding, the second winding coil will generate a magnetic field to form a third magnetic circuit, and part of the leakage magnetic flux in the magnetic field of the second winding flows from the magnetic circuit interface D through the magnetic circuit interface E and the magnetic circuit interface A in sequence, and forms a first magnetic circuit in the first iron core and the second iron core, while charging the first winding; when the AC voltage or current signal to be filtered is applied to the third After the two input ports of the second winding, the alternating current generated in the second winding will excite an alternating magnetic field and flow out from the magnetic circuit interface E along the third magnetic circuit to form a third magnetic circuit; at the same time, part of the leakage magnetic field in the magnetic field enters the resonant unit along the magnetic circuit interface D, passes through the first winding along the first magnetic circuit, and charges the first winding, causing the first winding and the first capacitor to resonate, generating an alternating magnetic field along the second magnetic circuit; when the resonant current of the first winding and the first capacitor reaches a threshold peak at a certain frequency, the magnetic field flowing through the second magnetic circuit is significantly enhanced, and part of the magnetic field flows through the second winding along the first magnetic circuit, and the phase of the magnetic field flowing through the second winding is opposite to the phase of the magnetic field generated by the input port signal on the second winding, thereby offsetting the voltage or current input signal at the current frequency, and producing the effect of a band-stop filter.

[0013] In some exemplary embodiments, the cross-section of the second core is L-shaped or U-shaped.

[0014] In some exemplary embodiments, the low-frequency power filter based on the magnetic field resonance principle also includes: a second iron core, the second iron core is connected to the fourth sub-iron core, and the second winding is wound on the second iron core; the second winding includes two input ports, and the input ports are used to connect the AC signal of the voltage or current to be filtered; the magnetic circuit interface D is arranged at the connection between the first iron core and the fourth sub-iron core, and the two side walls of the second iron core away from the end of the fourth sub-iron core are provided with a magnetic circuit interface E; when the AC current flows into the second winding from both ends of the second winding, the second winding coil will generate a magnetic field to form a third magnetic circuit, and part of the leakage magnetic field in the second winding flows from the magnetic circuit interface D through the magnetic circuit interface E and the magnetic circuit interface A in sequence, and forms a first magnetic circuit in the first iron core and the second iron core, and at the same time charges the first winding; when the AC current to be filtered After the voltage or current signal is applied to the two input ports of the second winding, the alternating current generated in the second winding will excite an alternating magnetic field and flow out from the magnetic circuit interface E along the third magnetic circuit to form a third magnetic circuit; at the same time, part of the leakage magnetic field in the magnetic field enters the resonant unit along the magnetic circuit interface D, passes through the first winding along the first magnetic circuit, and charges the first winding, causing the first winding and the first capacitor to resonate, generating an alternating magnetic field along the second magnetic circuit; when the resonant current of the first winding and the first capacitor reaches a threshold peak at a certain frequency, the magnetic field flowing through the second magnetic circuit is significantly enhanced, and part of the magnetic field flows through the second winding along the first magnetic circuit, and the phase of the magnetic field flowing through the second winding is opposite to the phase of the magnetic field generated by the input port signal on the second winding, thereby offsetting the voltage or current input signal at the current frequency and producing the effect of a band-stop filter.

[0015] In some exemplary embodiments, the above-mentioned low-frequency power filter based on the magnetic field resonance principle includes two resonant units symmetrically arranged on both sides of the second winding; the filtering effect and the center frequency are adjusted by adjusting the distance between the two magnetic circuit interfaces A of the two resonant units, the air gap size of each resonant unit, the number of turns of the first winding, and the capacitance of the first capacitor.

[0016] In some exemplary embodiments, the low-frequency power filter based on the magnetic field resonance principle further includes: a second winding wound on the second iron core; the second winding includes two input ports, and the input ports are used to connect the AC signal of the voltage or current to be filtered; the distance between the magnetic circuit interface E and the magnetic circuit interface A is 0, and the cross-section of the first iron core is an O-shape or two O-shapes; when the voltage or current alternating signal to be filtered is connected to both ends of the second winding, an alternating current will flow through the second winding, and then an alternating magnetic field along the first magnetic circuit will be generated in the first iron core; when the generated magnetic field flows through the first winding, a current will be generated in the first winding, and an alternating magnetic field will be generated in the first winding. The magnetic fields generated by the two windings are in opposite directions, which offset the magnetic field of the second winding and hinder the input signal from flowing through the second winding; when the frequency of the input signal reaches a specific frequency, the first winding and the first capacitor will resonate, and the magnetic field generated by the first winding will be in phase with the magnetic field generated by the second winding, thereby allowing the input signal to pass through the second winding at this specific frequency, which acts as a bandpass filter; the filter includes two resonant units symmetrically arranged on both sides of the second winding; by adjusting the distance between the two magnetic circuit interfaces A of the two resonant units, the air gap size of each resonant unit, the number of turns of the first winding, and the capacitance of the first capacitor, the filtering effect and center frequency can be adjusted.

[0017] The technical solution provided by the embodiments of the present application has at least the following advantages:

[0018] The embodiment of the present application provides a low-frequency power filter based on the magnetic field resonance principle, which includes: at least one resonant unit; the resonant unit includes a first iron core, a first winding and a first capacitor; wherein the first winding is wound around the first iron core, and the first winding is connected in series with the first capacitor; the material of the first iron core is a magnetic conductive material; the ends of the first iron core are provided with a magnetic circuit interface A, a magnetic circuit interface B, a magnetic circuit interface C and a magnetic circuit interface D, and there is an air gap between the magnetic circuit interface B and the magnetic circuit interface C. When the external magnetic field flows into the first iron core from the magnetic circuit interface A or the magnetic circuit interface D, it will pass through the first winding to form a first magnetic circuit; when the first magnetic circuit flows through the first winding, a portion of the leakage magnetic flux will flow from the magnetic circuit interface B to the magnetic circuit interface C to form a second magnetic circuit; at the same time, the first winding is energized, and after the first winding is energized, it will resonate with the first capacitor. The low-frequency power filter based on the magnetic field resonance principle provided by this application differs from traditional bandpass and lowpass filters that only filter voltage or current energy. Instead, the filter of this application utilizes the characteristics of the magnetic field generated by the resonant unit and the magnetic field generated by the alternating voltage or current applied to the input terminal, which are opposite in phase but similar in amplitude. By canceling out the magnetic fields, the voltage or current is filtered. Therefore, it can achieve bandpass or bandstop filtering of high-power, high-voltage, and high-current energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] One or more embodiments are exemplarily described by the pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Unless otherwise stated, the pictures in the drawings do not constitute proportional limitations.

[0020] FIG1 is a schematic cross-sectional structural diagram of a resonance unit of a low-frequency power filter based on the magnetic field resonance principle provided in one embodiment of the present application.

[0021] FIG2 is a schematic diagram of the cross-sectional structure of a resonance unit of a low-frequency power filter based on the magnetic field resonance principle provided in another embodiment of the present application.

[0022] FIG3 is a three-dimensional diagram of the resonance unit of the low-frequency power filter based on the magnetic field resonance principle shown in FIG2 .

[0023] FIG4 is a schematic diagram of the cross-sectional structure of a resonance unit of a low-frequency power filter based on the magnetic field resonance principle provided in yet another embodiment of the present application.

[0024] FIG. 5 is a perspective view of an alternative solution to the resonance unit shown in FIG. 4 .

[0025] FIG. 6 is a perspective view of another alternative solution of the resonance unit shown in FIG. 4 .

[0026] FIG7 is a schematic diagram of a cross-sectional structure of a filter based on the resonance unit shown in FIG1 according to an embodiment of the present application.

[0027] FIG8 is a schematic diagram of a cross-sectional structure of an alternative solution to the filter shown in FIG7 .

[0028] FIG9 is a schematic cross-sectional view of another alternative to the filter shown in FIG7 .

[0029] FIG10 is a schematic diagram of a cross-sectional structure of a filter based on the resonance unit shown in FIG2 according to an embodiment of the present application.

[0030] FIG11 is a schematic diagram of a cross-sectional structure of an alternative solution to the filter shown in FIG10 .

[0031] FIG12 is a schematic diagram of a cross-sectional structure of another alternative solution to the filter shown in FIG10 .

[0032] FIG13 is a schematic diagram of a cross-sectional structure of a filter based on the resonance unit shown in FIG4 according to an embodiment of the present application.

[0033] FIG14 is a schematic diagram of a cross-sectional structure of an alternative solution to the filter shown in FIG13 .

[0034] FIG15 is a schematic diagram of a cross-sectional structure of another alternative to the filter shown in FIG13 .

[0035] FIG16 is a schematic diagram of a cross-sectional structure of a filter based on two resonant units shown in FIG1 according to an embodiment of the present application.

[0036] FIG17 is a schematic diagram of a cross-sectional structure of an alternative solution to the filter shown in FIG16 .

[0037] FIG18 is a schematic diagram of a cross-sectional structure of another alternative to the filter shown in FIG16 .

[0038] FIG19 is a schematic diagram of the cross-sectional structure of the filter shown in FIG12 provided by an embodiment of the present application when the distance between the magnetic circuit interface E and the magnetic circuit interface A is 0. FIG19 is a schematic diagram of the cross-sectional structure of the filter shown in FIG12 provided by an embodiment of the present application.

[0039] FIG20 is a schematic diagram of a cross-sectional structure of an alternative solution to the filter shown in FIG19 .

[0040] FIG21 is a schematic diagram of the cross-sectional structure of a resonant unit provided by an embodiment of the present application when multiple windings and capacitors are connected in series. DETAILED DESCRIPTION

[0041] As can be seen from the background technology, the existing low-frequency, high-power analog filters have complex structures and are difficult to filter high-power inputs. Moreover, power filter devices can only perform simple low-pass filtering and are difficult to achieve band-pass and band-stop filtering. That is, the existing ones cannot achieve band-pass or band-stop filtering of high voltage, large current, medium and low frequency power level voltages and currents.

[0042] Existing filters in high-power applications typically focus on simple low-pass filters, making it difficult to implement high-pass or bandpass filtering functions. Patent CN211479840U proposes an integrated filter (integrated inductor) for power supplies. By integrating coils with varying heat generation levels onto a single core, the average heat generation of the inductor is lower, reducing heat dissipation requirements. Patents CN107659129A and CN202004639U propose two common-mode and differential-mode magnetic integrated filters. These solutions primarily utilize a combination of two coils and a magnetic core to achieve differential or common-mode filtering, essentially forming an inductor-based low-pass filter. Patent CN114883111A proposes an integrated filter solution that integrates a housing, busbar capacitors, a DC busbar, a voltage-stabilizing capacitor, and a magnetic ring. Essentially, this approach integrates a magnetic ring onto the DC busbar and voltage-stabilizing capacitor to achieve low-pass filtering. While these solutions can withstand high voltages and currents, they essentially utilize inductive components such as magnetic rings and inductors to achieve low-pass filtering, making it difficult to implement bandpass or band-stop filtering.

[0043] On the other hand, in high-frequency applications (frequencies reaching MHz or even GHz), by properly designing the structure of conductive and dielectric materials, a certain amount of parasitic inductance and capacitance can be generated within the structure. By utilizing the parasitic inductance or capacitance within the structure to achieve resonance, bandpass and bandstop filtering can be achieved. However, these filters can only operate in high-frequency (MHz or even GHz) low-power applications (such as communications and radio frequency), and are difficult to apply to high-power applications with frequencies of several hundred kHz or even tens of kHz.

[0044] For example: Patents CN116094489A and CN116318003A realize the integration of capacitor elements and inductor elements through copper pillars, capacitor dielectrics, inductor dielectrics, etc., which can be used to filter high-frequency signals (the center frequency of the filter passband is 1GHz). However, this filter can only filter low-voltage and low-current signals and is difficult to withstand high-voltage and high-current situations. Patents CN113690555A, CN113937096A, and CN116960588A combine materials with different dielectric constants to form inductor and capacitor effects, forming resonance to achieve bandpass filtering. However, this filter can also only filter high-frequency (several GHz frequencies) and low-power signals. Patent CN201610796833.2 proposes a metamaterial microwave filter based on an open resonant ring structure, which is composed of an open resonant ring structure connected to a capacitor to improve the high-end external suppression and symmetry of the passband. Patent CN202010677785.1 proposes a terahertz metamaterial filter composed of multiple layers of polymer and metal materials, also known as metamaterial units. The stacking of these units causes incident terahertz signals to resonate and absorb terahertz waves at the resonant frequency. Patent CN201711158654.7 creates a metamaterial by carving a thin film of a substrate into a specific pattern. The transmittance is controlled based on the polarization of the electromagnetic wave striking the substrate to achieve filtering. Patent CN201810131434.3 modulates the coupling state of the resonant structure by adjusting two parallel metamaterial planes, thereby regulating signals in the microwave, terahertz, and optical bands. Patent CN202110712256.5 proposes a microstrip band-stop filter technology. Its core lies in its design based on a sector-shaped and sector-ring structure, with conductive connectors connecting the sectors and the sector-ring to adjust the operating frequency. The filter uses a conductor pattern pre-determined on a dielectric substrate, and the position of the conductive connectors can be adjusted to achieve filtering at different frequencies. The aforementioned resonance-based filtering methods all achieve filtering by designing material structures to create resonance between parasitic inductance and capacitance. However, since the parasitic capacitance and inductance are typically very small, they can only be used in high-frequency applications. Furthermore, due to their typically delicate structures, they are unable to withstand high voltage and high current conditions. Consequently, existing technologies are unable to achieve bandpass or bandstop filtering for high-voltage, high-current, and medium- and low-frequency power-level voltages and currents.

[0045] To solve the above technical problems, the embodiments of the present application provide a low-frequency power filter based on the principle of magnetic field resonance, comprising: at least one resonant unit; the resonant unit comprises a first iron core, a first winding, and a first capacitor; wherein the first winding is wound around the first iron core and is connected in series with the first capacitor; the material of the first iron core is a magnetic conductive material; the ends of the first iron core are provided with magnetic circuit interfaces A, B, C, and D, and an air gap is provided between magnetic circuit interfaces B and C. The embodiments of the present application provide a low-frequency power filter based on the principle of magnetic field resonance, which can achieve bandpass filtering and bandstop filtering of high voltage, large current, medium and low frequency current, and voltage, thus making up for the shortcomings of existing filter technology.

[0046] The following detailed description of the various embodiments of the present application is provided in conjunction with the accompanying drawings. However, those skilled in the art will appreciate that many technical details are provided in the various embodiments of the present application to facilitate a better understanding of the present application. However, even without these technical details and the various variations and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0047] Referring to Figure 1, an embodiment of the present application provides a low-frequency power filter based on the principle of magnetic field resonance, including: at least one resonant unit; the resonant unit includes a first iron core 101, a first winding 102 and a first capacitor 103; wherein, the first winding 102 is wound around the first iron core 101, and the first winding 102 is connected in series with the first capacitor 103; the material of the first iron core 101 is a magnetic conductive material; the end of the first iron core 101 is provided with a magnetic circuit interface A, a magnetic circuit interface B, a magnetic circuit interface C and a magnetic circuit interface D, and there is an air gap between the magnetic circuit interface B and the magnetic circuit interface C.

[0048] This application mainly addresses the problems of existing low-frequency, high-power analog filters that are complex in structure and difficult to filter high-power inputs; and the problem that power filter devices can only perform simple low-pass filtering and are difficult to achieve band-pass and band-stop filtering. Based on the principle of magnetic field resonance, this application proposes a resonant unit, and on the basis of the proposed resonant unit, proposes a high-power, low-frequency band-pass and band-stop filter with a simple structure, which can achieve band-pass filtering and band-stop filtering of high voltage, large current, medium and low-frequency current and voltage, making up for the shortcomings of existing filters.

[0049] This application first proposes a resonant unit with a dual magnetic circuit. Based on this resonant unit, this application further proposes a band-stop filter and a band-pass filter. Unlike traditional band-pass and low-pass filters that only filter voltage or current electrical energy, this application utilizes the characteristics that the magnetic field generated by the resonant unit and the magnetic field generated by the alternating voltage or current applied to the input end have opposite phases and similar amplitudes. By canceling out the magnetic fields, the voltage or current is filtered. Therefore, it can achieve band-pass or band-stop filtering of high-power, high-voltage, high-current, low-frequency electrical energy.

[0050] This application proposes a low-frequency power filter based on the principle of magnetic field resonance, including at least one resonant unit. The cross-sectional structure of the resonant unit is shown in Figure 1. Its main structure is a C-shaped dual magnetic circuit structure with four magnetic circuit interfaces (magnetic circuit interfaces A, B, C, and D). The resonant unit is composed of a first iron core 101, a first winding 102, and a first capacitor 103, wherein the first winding 102 is wound around the first iron core 101, and the first capacitor 103 is connected in series with the first winding 102.

[0051] The first core 101 is made of a magnetically conductive material and is provided with magnetic circuit interfaces A, B, C, and D, with an air gap provided between magnetic circuit interface B and magnetic circuit interface C. When an external magnetic field flows into the first core 101 through magnetic circuit interface A or magnetic circuit interface D, the magnetic field passes through the first winding 102 to form a first magnetic circuit. When the first magnetic circuit flows through the first winding 102, some leakage magnetic flux in the magnetic field flows from magnetic circuit interface B to magnetic circuit interface C, forming a second magnetic circuit and simultaneously energizing the first winding 102. The energized first winding 102 resonates with the first capacitor 103. The resonant frequency of the resonant unit can be adjusted by adjusting the air gap between magnetic circuit interfaces B and C, the capacitance of the first capacitor 103, the number of turns of the first winding 102, and the like.

[0052] As shown in Figure 1, in some embodiments, the first iron core 101 includes a first protrusion (the protrusion at the left end of the first iron core 101 in Figure 1) and a second protrusion (the protrusion at the right end of the first iron core 101 in Figure 1) relatively arranged, the magnetic circuit interface B is arranged at the first protrusion, the magnetic circuit interface A is arranged at the end of the first iron core 101 near the magnetic circuit interface B, the magnetic circuit interface C is arranged at the second protrusion, and the magnetic circuit interface D is arranged at the end of the first iron core 101 near the magnetic circuit interface C.

[0053] An alternative to the resonant unit shown in FIG1 is shown in FIG2 , in which the magnetic circuit interface B and the magnetic circuit interface C can be made integral with the core without having to protrude. As shown in FIG2 , in some embodiments, the first core 101 includes a first sub-core (the core on the left side in FIG2 ), a second sub-core (the core at the bottom in FIG2 ), and a third sub-core (the core on the right side in FIG2 ), with the two ends of the second sub-core connected to the first sub-core and the third sub-core, respectively; the first sub-core and the third sub-core are arranged opposite each other, the first winding 102 is wound around the third sub-core, and an air gap is provided between the first sub-core and the third sub-core; the magnetic circuit interface A is arranged at the end of the first sub-core, the magnetic circuit interface B is arranged on the side wall of the first sub-core facing the third sub-core, the magnetic circuit interface C is arranged on the side wall of the third sub-core facing the first sub-core, and the magnetic circuit interface D is arranged at the end of the third sub-core.

[0054] It should be noted that the first, second, and third sub-cores can be made from a single piece of iron core, i.e., they can be an integrated structure. As shown in FIG2 , the first winding 102 is wound around the third sub-core, and the first and third sub-cores are arranged face to face, with the first and third sub-cores positioned above the second sub-core; together, the first, second, and third sub-cores form a "C"-shaped structure.

[0055] The stereogram of the resonant unit shown in Figure 2 is shown in Figure 3. Similarly, the resonant frequency of the resonant unit can be adjusted by adjusting the air gap between the magnetic circuit interface B and the magnetic circuit interface C, the capacitance of the first capacitor 103, the number of turns of the first winding 102, etc.

[0056] An alternative to the resonant unit shown in FIG1 is shown in FIG4 , in which two first cores 101 can be combined into a symmetrical structure and share a set of first capacitors 103 and first windings 102. A perspective view of the solution shown in FIG4 is shown in FIG5 and FIG6 , in which the radial cross-section of the first core 101 can be either square or circular.

[0057] As shown in Figures 4 and 5, in some embodiments, the first core 101 includes a first sub-core, a second sub-core, a third sub-core, and a fourth sub-core (the core shown in Figure 5 located in the middle of the resonant unit, on which the first winding 102 is wound), the two ends of the second sub-core are respectively connected to the first sub-core (the core located on the right side of the fourth sub-core) and the third sub-core (the core located on the left side of the fourth sub-core), the fourth sub-core is located between the first sub-core and the third sub-core, and the end of the fourth sub-core is connected to the middle of the second sub-core; the first sub-core The core and the third sub-core are symmetrical about the longitudinal center axis of the fourth sub-core, the first winding 102 is wound around the fourth sub-core, and there is an air gap between the fourth sub-core and the first sub-core, and between the fourth sub-core and the third sub-core; the end of the first sub-core and the end of the third sub-core are provided with a magnetic circuit interface A, the side wall of the first sub-core and the side wall of the third sub-core are provided with a magnetic circuit interface B, the end of the fourth sub-core is provided with a magnetic circuit interface D, and the side wall of the fourth sub-core facing the first sub-core and the side wall facing the third sub-core are provided with a magnetic circuit interface C.

[0058] It should be noted that the first sub-core, the second sub-core, the third sub-core and the fourth sub-core in Figures 4 and 5 can be made of a whole piece of core, that is, the first sub-core, the second sub-core, the third sub-core and the fourth sub-core can be an integrated structure, together constituting the first core 101.

[0059] As shown in Figure 6, in some embodiments, the first core 101 includes a first sub-core (an annular core surrounding the first winding 102), a second sub-core (located at the bottom of the resonant unit) and a third sub-core (located in the middle of the resonant unit, with the first winding 102 wrapped around it), the first sub-core is an annular structure, and the ends of the first sub-core and the third sub-core are both connected to the second sub-core; the first winding 102 is wound around the third sub-core, and there is an air gap between the third sub-core and the annular first sub-core; a magnetic circuit interface A is provided on the annular end of the first sub-core, a magnetic circuit interface B is provided on the annular side wall of the first sub-core, a magnetic circuit interface C is provided on the side wall of the third sub-core, and a magnetic circuit interface D is provided at the end of the third sub-core.

[0060] It should be noted that the first sub-core, the second sub-core and the third sub-core in Figure 6 can be made of a whole core, that is, the first sub-core, the second sub-core and the third sub-core can be an integrated structure, together constituting the first core 101.

[0061] Based on the resonant units shown in Figures 1 to 6 , the present application also proposes a filter. The filter based on the solution shown in Figure 1 is shown in Figure 7 .

[0062] As shown in FIG7 , a second core 104 is connected to the magnetic circuit interface D of the solution shown in FIG1 , and a second winding 105 is wound around the second core 104. The AC signal of the voltage or current to be filtered is connected to the two ports (input port 1 and input port 2) of the second winding 105. It should be noted that the first core 101 and the second core 104 can be made of a single piece of iron core.

[0063] As shown in Figure 7, in some embodiments, the low-frequency power filter based on the magnetic field resonance principle also includes: a second iron core 104, and a second winding 105 is wound on the second iron core 104; the second winding 105 includes two input ports (input port 1, input port 2), and the input port is used to connect the AC signal of the voltage or current to be filtered; the magnetic circuit interface D is arranged at the connection between the first iron core 101 and the second iron core 104, and a magnetic circuit interface E is provided on the top side wall of the second iron core 104 away from the first iron core 101; when the AC current flows into the second winding from both ends of the second winding 105, the second winding coil will generate a magnetic field to form a third magnetic circuit, and part of the leakage magnetic field in the second winding flows from the magnetic circuit interface D through the magnetic circuit interface E and the magnetic circuit interface A in sequence, and forms a first magnetic circuit in the first iron core 101 and the second iron core 104, while charging the first winding 102.

[0064] When the alternating voltage or current signal to be filtered is applied to the two input ports of the second winding 105, the alternating current generated in the second winding 105 will excite an alternating magnetic field and flow out from the magnetic circuit interface E along the third magnetic circuit to form a third magnetic circuit; at the same time, part of the leakage magnetic field in the magnetic field enters the resonant unit along the magnetic circuit interface D, passes through the first winding 102 along the first magnetic circuit, and charges the first winding 102, causing the first winding 102 and the first capacitor 103 to resonate, generating an alternating magnetic field along the second magnetic circuit.

[0065] When the resonant current of the first winding 102 and the first capacitor 103 reaches a threshold peak value at a certain frequency, the magnetic field flowing through the second magnetic circuit is significantly enhanced, and part of the magnetic field flows along the first magnetic circuit through the second winding 105, and the phase of the magnetic field flowing through the second winding 105 is opposite to the phase of the magnetic field generated by the input port signal on the second winding 105, thereby offsetting the voltage or current input signal at the current frequency and producing the effect of a band-stop filter. Unlike the traditional method of filtering only the electrical energy of voltage or current, the solution proposed in this application utilizes the characteristics that the magnetic field generated by the resonant unit and the magnetic field generated by the alternating voltage or current applied to the input end are opposite in phase and similar in amplitude, and the magnetic fields cancel each other out to achieve filtering of the voltage or current.

[0066] It should be noted that the first magnetic circuit is both a magnetic circuit through which a portion of the magnetic field of the second winding 105 flows and a magnetic circuit through which a portion of the magnetic field of the first winding 102 flows after resonance.

[0067] In some embodiments, the cross-section of the second core 104 is L-shaped or U-shaped.

[0068] Figure 8 shows an alternative to the filter solution shown in Figure 7, in which the second core cross-section can also be made into an "L" shape. Furthermore, the second core cross-section can also be made into a "U" shape, as shown in Figure 9. By adjusting the length of the second air gap between magnetic circuit interface E and magnetic circuit interface A, the filtering effect can be adjusted.

[0069] Similar to FIG7 , the filter based on the resonant unit shown in FIG2 is shown in FIG10 .

[0070] Similar to FIG8 , FIG9 , and FIG10 , alternative solutions to the filters shown are shown in FIG11 and FIG12 .

[0071] Similar to FIG7 , the filter based on the resonant unit shown in FIG4 is shown in FIG13 .

[0072] As shown in Figure 13, in some embodiments, the low-frequency power filter based on the magnetic field resonance principle also includes: a second iron core 104, the second iron core 104 is connected to the fourth sub-core (the iron core located in the middle of the resonant unit), and the second winding 105 is wound on the second iron core 104; the second winding 105 includes two input ports (input port 1 and input port 2), and the two input ports are used to connect the AC signal of the voltage or current to be filtered; the magnetic circuit interface D is arranged at the connection between the first iron core 101 and the fourth sub-core, and the magnetic circuit interface E is provided on the two side walls of the end of the second iron core 104 away from the fourth sub-core.

[0073] When an alternating current flows into the second winding 105 from both ends of the second winding 105, the coil of the second winding 105 will generate a magnetic field to form a third magnetic circuit. Part of the leakage magnetic flux in the magnetic field of the second winding 105 flows from the magnetic circuit interface D through the magnetic circuit interface E and the magnetic circuit interface A in sequence, and forms a first magnetic circuit in the first iron core 101 and the second iron core 104, while energizing the first winding.

[0074] When the alternating voltage or current signal to be filtered is applied to the two input ports of the second winding 105, the alternating current generated in the second winding 105 will excite an alternating magnetic field and flow out from the magnetic circuit interface E along the third magnetic circuit to form a third magnetic circuit; at the same time, part of the leakage magnetic field in the magnetic field enters the resonant unit along the magnetic circuit interface D, passes through the first winding 102 along the first magnetic circuit, and charges the first winding 102, causing the first winding 102 and the first capacitor 103 to resonate, generating an alternating magnetic field along the second magnetic circuit.

[0075] When the resonant current of the first winding 102 and the first capacitor 103 reaches a threshold peak at a certain frequency, the magnetic field flowing through the second magnetic circuit is significantly enhanced, and part of the magnetic field flows through the second winding 105 along the first magnetic circuit. The phase of the magnetic field flowing through the second winding 105 is opposite to the phase of the magnetic field generated by the input port signal on the second winding 105, thereby offsetting the voltage or current input signal at the current frequency and producing the effect of a band-stop filter.

[0076] Similar to Figures 8 and 9 , alternatives to the filter shown in Figure 13 are shown in Figures 14 and 15 .

[0077] In some embodiments, the low-frequency power filter based on the magnetic field resonance principle includes two resonant units symmetrically arranged on either side of the second winding 105, as shown in FIG16 . The filtering effect and center frequency can be adjusted by adjusting the distance between the two magnetic circuit interfaces A of the two resonant units, the air gap size of each resonant unit, the number of turns of the first winding 102, and the capacitance of the first capacitor 103.

[0078] As shown in Figure 16, in order to enhance the filtering effect of the resonant unit, the two resonant units shown in Figure 1 can be symmetrically arranged on both sides of the second winding 105, and the filtering principle is the same as the scheme shown in Figure 7; by adjusting the distance between the two magnetic circuit interfaces A of the two resonant units, the size of the air gap of each resonant unit itself, the number of turns of the first winding 102, and the capacitance of the first capacitor 103, the filtering effect and center frequency can be adjusted.

[0079] As shown in FIG. 17 and FIG. 18 , the solution shown in FIG. 16 can also be replaced by the resonance units shown in FIG. 2 and FIG. 4 .

[0080] It should be noted that there is an extreme case where the distance between magnetic circuit interface E and magnetic circuit interface A in Figure 12 is zero. In this case, the cross-section of the first core 101 of the filter in Figure 12 is an "O"-shaped cross-section (which can also be regarded as a "0"-shaped cross-section), as shown in Figure 19. The cross-section of the first core 101 can also be two parallel "O"-shaped core cross-sections (which can also be regarded as two parallel "0"-shaped) core cross-sections, as shown in Figure 20.

[0081] In the bandpass filter shown in Figures 19 and 20, the second winding 105 is wound around the first core 101. The second winding 105 includes two input ports (input port 1 and input port 2) for connecting the AC voltage or current signal to be filtered. The bandpass filtering principle is as follows: the cross-section of the filter's first core 101 is a single "0"-shaped or double "0"-shaped core cross-section. Since the magnetic resistance of the first core is very low, the second and third magnetic circuits in Figure 12 are short-circuited, leaving only the first magnetic circuit. When the alternating voltage or current signal to be filtered is connected to both ends of the second winding, an alternating current flows through the second winding 105, generating an alternating magnetic field along the first magnetic circuit in the first core 101. When this generated magnetic field flows through the first winding 102, a current is generated within the first winding 102, generating a magnetic field in the opposite direction to the magnetic field generated by the second winding 105. This cancels the magnetic field of the second winding 102 and prevents the input signal from flowing through the second winding 105. When the frequency of the input signal reaches a specific frequency, the first winding 102 and the first capacitor 103 will resonate, and the magnetic field generated by the first winding 102 will be in phase with the magnetic field generated by the second winding 102, so that the input signal can pass through the second winding 105 at this specific frequency, which acts as a bandpass filter.

[0082] The distance between the magnetic circuit interface E and the magnetic circuit interface A in the scheme shown in Figure 15 is set to 0. At this time, the cross-section of the first iron core 101 of the filter in Figure 15 is two parallel "0" shapes, as shown in Figure 20. Its filtering principle is the same as that of the scheme shown in Figure 19 and will not be repeated here.

[0083] It should be noted that the above-mentioned bandpass filter also includes two resonant units symmetrically arranged on both sides of the second winding 105; the filtering effect and center frequency are adjusted by adjusting the distance between the two magnetic circuit interfaces A of the two resonant units, the air gap size of each resonant unit, the number of turns of the first winding, and the capacitance of the first capacitor.

[0084] When multiple windings and capacitors are connected in series to the first core 101 of a resonant unit, as shown in FIG21 (103n and 102n represent the nth capacitor and nth winding, respectively), the resonant unit will resonate at multiple frequencies. Therefore, by incorporating the resonant unit shown in FIG21 into the aforementioned filters, band-stop or band-pass filtering with multiple center frequencies can be achieved.

[0085] Figure 21 shows a resonant unit with multiple first capacitors and first windings connected in series to its core. By connecting multiple capacitors and windings in series, the resonant unit can resonate at different frequencies. Using the resonant unit shown in Figure 21 instead of the resonant units in Figures 7 to 20 enables bandpass filtering or bandstop filtering for multiple frequencies.

[0086] It should be noted that the first core 101 and the second core 104 in the drawings of this application can be made of a whole piece of core. For the convenience of description, this application divides the core into the first core and the second core.

[0087] Compared with the prior art, the low-frequency power filter based on the magnetic field resonance principle provided by the present application has the following advantages: the filter of the present application is different from the traditional band-pass and low-pass filters that only filter the electrical energy of voltage or current. The solution proposed in the present application is to utilize the characteristics that the magnetic field generated by the resonant unit and the magnetic field generated by the alternating voltage or current applied to the input end are opposite in phase and similar in amplitude, and the magnetic fields cancel each other out to achieve filtering of the voltage or current. Therefore, band-pass or band-stop filtering of high-power, high-voltage, and high-current electrical energy can be achieved. The low-frequency power filter based on the magnetic field resonance principle provided by the present application has been verified by simulation and experiments, and the effect is good.

[0088] Based on the above technical solution, an embodiment of the present application provides a low-frequency power filter based on the principle of magnetic field resonance, which filter includes: at least one resonant unit; the resonant unit includes a first iron core 101, a first winding 102 and a first capacitor 103; wherein, the first winding 102 is wound around the first iron core 101, and the first winding 102 is connected in series with the first capacitor 103; the material of the first iron core 101 is a magnetic conductive material; the end of the first iron core 101 is provided with a magnetic circuit interface A, a magnetic circuit interface B, a magnetic circuit interface C and a magnetic circuit interface D, and there is an air gap between the magnetic circuit interface B and the magnetic circuit interface C.

[0089] When the external magnetic field flows into the first iron core 101 from the magnetic circuit interface A or the magnetic circuit interface D, it will pass through the first winding 102 to form a first magnetic circuit; when the first magnetic circuit flows through the first winding 102, a part of the leakage magnetic flux will flow from the magnetic circuit interface B to the magnetic circuit interface C to form a second magnetic circuit; at the same time, the first winding 102 is energized, and after the first winding 102 is energized, it will resonate with the first capacitor 103. The low-frequency power filter based on the magnetic field resonance principle provided by the present application is different from the traditional band-pass and low-pass filters that only filter the electrical energy of voltage or current. The filter of the present application utilizes the characteristics that the magnetic field generated by the resonant unit and the magnetic field generated by the alternating voltage or current applied to the input end are opposite in phase and similar in amplitude. The magnetic fields cancel each other out to achieve filtering of the voltage or current. Therefore, band-pass or band-stop filtering of high-power, high-voltage, and high-current electrical energy can be achieved.

[0090] Those skilled in the art will appreciate that the above-described embodiments are specific examples for implementing the present application, and that in actual applications, various changes in form and detail may be made thereto without departing from the spirit and scope of the present application. Any person skilled in the art may make changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be subject to the scope defined in the claims.

Claims

1. A low-frequency power filter based on the magnetic field resonance principle, characterized in that: include: at least one resonant unit; The resonant unit includes a first iron core, a first winding and a first capacitor; wherein, The first winding is wound around the first iron core, and the first winding is connected in series with the first capacitor; The material of the first iron core is magnetic conductive material; the ends of the first iron core are provided with magnetic circuit interface A, magnetic circuit interface B, magnetic circuit interface C and magnetic circuit interface D, and there is an air gap between the magnetic circuit interface B and the magnetic circuit interface C.

2. The low-frequency power filter based on the magnetic field resonance principle according to claim 1, characterized in that: When the external magnetic field flows into the first iron core from magnetic circuit interface A or magnetic circuit interface D, the magnetic field passes through the first winding to form a first magnetic circuit; when the first magnetic circuit flows through the first winding, part of the leakage magnetic field in the magnetic field flows from magnetic circuit interface B to magnetic circuit interface C, forming a second magnetic circuit, and at the same time charging the first winding. The energized first winding resonates with the first capacitor.

3. The low-frequency power filter based on the magnetic field resonance principle according to claim 2, characterized in that: The first iron core includes a first protrusion and a second protrusion relatively arranged, the magnetic circuit interface B is arranged on the first protrusion, the magnetic circuit interface A is arranged at the end of the first iron core near the magnetic circuit interface B, the magnetic circuit interface C is arranged on the second protrusion, and the magnetic circuit interface D is arranged at the end of the first iron core near the magnetic circuit interface C.

4. The low-frequency power filter based on the magnetic field resonance principle according to claim 2, characterized in that: The first iron core includes a first sub-core, a second sub-core, and a third sub-core, wherein two ends of the second sub-core are connected to the first sub-core and the third sub-core respectively; the first sub-core and the third sub-core are arranged opposite to each other, the first winding is wound around the third sub-core, and an air gap is formed between the first sub-core and the third sub-core; The magnetic circuit interface A is arranged at the end of the first sub-core, the magnetic circuit interface B is arranged on the side wall of the first sub-core facing the third sub-core, the magnetic circuit interface C is arranged on the side wall of the third sub-core facing the first sub-core, and the magnetic circuit interface D is arranged at the end of the third sub-core.

5. The low-frequency power filter based on the magnetic field resonance principle according to claim 2, characterized in that: The first iron core includes a first sub-core, a second sub-core, a third sub-core, and a fourth sub-core. The second sub-core has two ends connected to the first sub-core and the third sub-core, respectively. The fourth sub-core is located between the first sub-core and the third sub-core, and an end of the fourth sub-core is connected to the middle of the second sub-core. The first sub-core and the third sub-core are symmetrical about the longitudinal center axis of the fourth sub-core. The first winding is wound around the fourth sub-core, and an air gap is formed between the fourth sub-core and the first sub-core, and between the fourth sub-core and the third sub-core. The ends of the first sub-core and the third sub-core are both provided with a magnetic circuit interface A, the side walls of the first sub-core and the third sub-core are both provided with a magnetic circuit interface B, and the end of the fourth sub-core is provided with a magnetic circuit interface D, and a magnetic circuit interface C is provided on the side wall of the fourth sub-core facing the first sub-core and the side wall facing the third sub-core.

6. The low-frequency power filter based on the magnetic field resonance principle according to claim 2, characterized in that: The first core includes a first sub-core, a second sub-core, and a third sub-core. The first sub-core is an annular structure, and ends of the first sub-core and the third sub-core are both connected to the second sub-core. The first winding is wound around the third sub-core, and an air gap is formed between the third sub-core and the annular first sub-core. A magnetic circuit interface A is provided on the annular end of the first sub-core, a magnetic circuit interface B is provided on the annular side wall of the first sub-core, a magnetic circuit interface C is provided on the side wall of the third sub-core, and a magnetic circuit interface D is provided on the end of the third sub-core.

7. The low-frequency power filter based on the magnetic field resonance principle according to claim 3 or 4, characterized in that: Also includes: a second iron core, on which a second winding is wound; the second winding comprises two input ports, the input ports being used to connect an AC signal of a voltage or current to be filtered; A magnetic circuit interface D is provided at the connection between the first iron core and the second iron core, and a magnetic circuit interface E is provided on the top side wall of the second iron core away from the first iron core; When an alternating current flows into the second winding from both ends, the second winding coil will generate a magnetic field, forming a third magnetic circuit. Part of the leakage magnetic flux in the second winding magnetic field flows from magnetic circuit interface D through magnetic circuit interface E and magnetic circuit interface A in sequence, and forms a first magnetic circuit in the first iron core and the second iron core, while charging the first winding. When an alternating voltage or current signal to be filtered is applied to the two input ports of the second winding, the alternating current generated in the second winding excites an alternating magnetic field and flows out from the magnetic circuit interface E along the third magnetic circuit, forming a third magnetic circuit. At the same time, part of the leakage magnetic flux in the magnetic field enters the resonant unit along the magnetic circuit interface D, passes through the first winding along the first magnetic circuit, and charges the first winding, causing the first winding and the first capacitor to resonate, thereby generating an alternating magnetic field along the second magnetic circuit. When the resonant current of the first winding and the first capacitor reaches a threshold peak at a certain frequency, the magnetic field flowing through the second magnetic circuit is significantly enhanced, and part of the magnetic field flows through the second winding along the first magnetic circuit. The phase of the magnetic field flowing through the second winding is opposite to the phase of the magnetic field generated by the input port signal on the second winding, thereby offsetting the voltage or current input signal at the current frequency and producing the effect of a band-stop filter.

8. The low-frequency power filter based on the magnetic field resonance principle according to claim 5, characterized in that: Also includes: a second iron core, the second iron core being connected to the fourth sub-iron core and having a second winding wound thereon; the second winding comprising two input ports, the input ports being used to connect an AC signal of a voltage or current to be filtered; The magnetic circuit interface D is provided at the connection between the first iron core and the fourth sub-iron core, and the second iron core is away from the first iron core. Magnetic circuit interfaces E are provided on both side walls of the ends of the four-sub iron core; When an alternating current flows into the second winding from both ends, the second winding coil will generate a magnetic field, forming a third magnetic circuit. Part of the leakage magnetic flux in the second winding magnetic field flows from magnetic circuit interface D through magnetic circuit interface E and magnetic circuit interface A in sequence, and forms a first magnetic circuit in the first iron core and the second iron core, while charging the first winding. When an alternating voltage or current signal to be filtered is applied to the two input ports of the second winding, the alternating current generated in the second winding excites an alternating magnetic field and flows out from the magnetic circuit interface E along the third magnetic circuit, forming a third magnetic circuit. At the same time, part of the leakage magnetic flux in the magnetic field enters the resonant unit along the magnetic circuit interface D, passes through the first winding along the first magnetic circuit, and charges the first winding, causing the first winding and the first capacitor to resonate, thereby generating an alternating magnetic field along the second magnetic circuit. When the resonant current of the first winding and the first capacitor reaches a threshold peak at a certain frequency, the magnetic field flowing through the second magnetic circuit is significantly enhanced, and part of the magnetic field flows through the second winding along the first magnetic circuit. The phase of the magnetic field flowing through the second winding is opposite to the phase of the magnetic field generated by the input port signal on the second winding, thereby offsetting the voltage or current input signal at the current frequency and producing the effect of a band-stop filter.

9. The low-frequency power filter based on the magnetic field resonance principle according to claim 7 comprises two resonant units symmetrically arranged on both sides of the second winding; the filtering effect and the center frequency are adjusted by adjusting the distance between the two magnetic circuit interfaces A of the two resonant units, the air gap size of each resonant unit, the number of turns of the first winding, and the capacitance of the first capacitor.

10. The low-frequency power filter based on the magnetic field resonance principle according to claim 1, characterized in that: Also includes: a second winding wound on the first core; the second winding comprising two input ports, the input ports being used to connect an AC signal of a voltage or current to be filtered; The distance between the magnetic circuit interface E and the magnetic circuit interface A is 0, and the cross section of the first core is an O-shape or two O-shapes; When the voltage or current alternating signal to be filtered is connected to both ends of the second winding, an alternating current will flow through the second winding, thereby generating an alternating magnetic field along the first magnetic circuit in the first core; When the generated magnetic field flows through the first winding, a current is generated in the first winding, and a magnetic field in the opposite direction to the magnetic field generated by the second winding is generated, which cancels out the magnetic field of the second winding and prevents the input signal from flowing through the second winding. When the frequency of the input signal reaches a specific frequency, the first winding and the first capacitor will resonate, and the magnetic field generated by the first winding will be in phase with the magnetic field generated by the second winding, thereby allowing the input signal to pass through the second winding at this specific frequency, thus acting as a bandpass filter. The filter comprises two resonant units symmetrically arranged on both sides of the second winding; by adjusting the distance between the two magnetic circuit interfaces A of the two resonant units, the air gap size of each resonant unit, the number of turns of the first winding, the capacitance of the first capacitor, value to adjust the filtering effect and center frequency.

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