A magnetic device applied to a switching converter

Abstract

The application discloses a magnetic device applied to a switching converter, and relates to the field of magnetic devices.The magnetic device comprises a framework, a main magnetic core, a leakage magnetic core and two or more windings; the framework is provided with a main magnetic core accommodating groove, a leakage magnetic core accommodating groove and two or more winding accommodating grooves; the winding accommodating groove comprises a plurality of sub-grooves; the main magnetic core is installed in the main magnetic core accommodating groove; the leakage magnetic core is installed in the leakage magnetic core accommodating groove; different windings are wound in different winding accommodating grooves, and the same winding is wound in at least two sub-grooves of the same winding accommodating groove. The main magnetic core and the leakage magnetic core jointly act in the application, so that the magnetic device has stable leakage inductance and low parasitic capacitance when working at high frequency. The design of the sub-groove winding significantly reduces the parasitic capacitance inside the winding and between the windings, and improves the performance of the device.

Description

Technical Field

[0001] This application relates to the field of magnetic devices, and in particular to a magnetic device used in switching converters. Background Technology

[0002] With the widespread application of compound semiconductors such as gallium nitride, the switching frequency of switching converters is increasing, placing higher demands on the parasitic capacitance and leakage inductance of the magnetic core devices. In resonant and input filtering applications, small parasitic capacitance and large leakage inductance are required to reduce the escape of high-frequency interference signals and suppress high-frequency current fluctuations.

[0003] Limitations of traditional magnetic devices: 1) Parasitic capacitance problem: Traditional multilayer windings or tightly coupled structures (such as planar transformers) have large interlayer and inter-turn capacitances, which lead to significant eddy current losses and efficiency reduction at high frequencies; 2) Trade-off between leakage inductance and efficiency: Traditional designs reduce leakage inductance through tight coupling (such as sandwich winding), but in wide bandgap applications, leakage inductance is needed to achieve soft switching (such as LLC resonant converters), and precise control of leakage inductance is required. Summary of the Invention

[0004] The purpose of this application is to provide a magnetic device for use in switching converters, which solves the problems of excessive parasitic capacitance and insufficient leakage inductance in the prior art.

[0005] To achieve the above objectives, this application provides the following solution:

[0006] In a first aspect, this application provides a magnetic device for use in a switching converter, comprising: a frame, a main magnetic core, a leakage magnetic core, and two or more windings; the frame is provided with a main magnetic core receiving slot, a leakage magnetic core receiving slot, and two or more winding receiving slots; the winding receiving slots include multiple sub-slots; the main magnetic core is installed in the main magnetic core receiving slot; the leakage magnetic core is installed in the leakage magnetic core receiving slot; different windings are wound in different winding receiving slots, and the same winding is wound in at least two sub-slots of the same winding receiving slot.

[0007] According to the specific embodiments provided in this application, this application has the following technical effects:

[0008] The main magnetic core and the leakage core work together to ensure stable leakage inductance and low parasitic capacitance of the magnetic device at high frequencies. The slotted winding design significantly reduces parasitic capacitance within and between windings, improving device performance. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 This is a schematic diagram of the structure of a magnetic device applied to a switching converter according to an embodiment of this application;

[0011] Figure 2 Schematic diagram of each receiving tank;

[0012] Figure 3 Schematic diagram of the main magnetic core and leakage magnetic core;

[0013] Figure 4 This is the equivalent circuit diagram of the original structure of the internal capacitor of the winding;

[0014] Figure 5 This is an equivalent circuit diagram of the internal capacitance of the winding provided in an embodiment of this application. Detailed Implementation

[0015] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0016] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] In one exemplary embodiment, such as Figures 1-3 As shown, a magnetic device for use in a switching converter is provided, including a frame 1, a main magnetic core 2, a leakage magnetic core 3, and two or more windings 4.

[0018] The frame 1 is provided with a main magnetic core receiving slot 11, a leakage magnetic core receiving slot 12 and two or more winding receiving slots 13; the winding receiving slot 13 includes multiple sub-slots.

[0019] The main magnetic core 2 is installed in the main magnetic core receiving slot 11, wherein the column 21 passes through each winding to form a common magnetic circuit.

[0020] The leakage magnetic core 3 is installed in the leakage magnetic core receiving slot 12 and is located in the gap between adjacent windings, forming an independent leakage magnetic circuit.

[0021] Different windings 4 are wound in different winding receiving slots 13 to reduce inter-winding capacitance. The same winding 4 is wound in at least two slots of the same winding receiving slot 13 to reduce inter-layer capacitance within the winding.

[0022] In this implementation, the windings are divided into physically isolated blocks to reduce interlayer capacitance. The primary and secondary windings are arranged alternately to balance leakage inductance and capacitance (e.g., in a matrix transformer). The inter-turn spacing is increased, sacrificing some coupling coefficient to reduce capacitance. A split core or distributed air-gap design is employed to control leakage inductance and avoid local saturation.

[0023] Embedded magnets allow for flexible changes to the core material and parameters, optimizing the electric field distribution. Insulating materials are placed between adjacent slots, using polyimide, air gap isolation, or nano-coatings to reduce the inter-winding dielectric constant.

[0024] According to the capacitor principle: C = ε*S / d, the capacitance C is directly proportional to the area S and inversely proportional to the spacing D. In general magnetic devices, with multilayer windings such as W2 and W1, the relatively large area and small spacing D result in a relatively large parasitic capacitance.

[0025] This application reduces the parasitic capacitance within the windings and the parasitic capacitance between windings by changing the winding structure. The principle is as follows:

[0026] Inter-winding parasitic capacitance: Due to slotted winding, an increase in D leads to a significant decrease in capacitance C.

[0027] Internal capacitance of windings: such as Figure 4 and Figure 5 As shown, in high-frequency operation, the parasitic capacitance of the dual-slot structure is only 1 / 4 of the original, and in the case of a single winding with three slots, the parasitic capacitance is only 1 / 6 of the original.

[0028] In resonant operation or differential mode suppression applications, magnetic devices require a large leakage inductance to suppress current variations. To achieve this, this application uses a low-resistivity magnetic core in the gap between windings. This low-resistivity core is flexible, and different materials such as ferrite cores, amorphous cores, alloy cores, and high-permeability cores can be selected according to the application scenario and function. The permeability range of different materials will vary, and the saturation magnetic flux density will also change with the material. Key parameters such as the temperature coefficient will also change accordingly. Because this design structure can fix one type of core while flexibly replacing it with different materials, it can achieve the purpose of increasing leakage inductance and different required characteristics.

[0029] For calculating the inductance of an air-gap inductor, the expression for inductance L is generally related to the air gap length δ, permeability μ, number of turns N, effective area A of the coil, and average magnetic path length l in the magnetic circuit. The general formula can be expressed as:

[0030]

[0031] μ0 is the permeability of free space (describing the ability of "air / vacuum" to conduct magnetic fields; it is a constant). However, please note that this formula is a simplified model. In practical applications, the inductance is affected by many other factors, such as the specific arrangement of the windings and the properties of the core material.

[0032] Leakage flux control principle: L p For the required leakage inductance, its air gap l g The calculation formula can be approximated as follows:

[0033]

[0034] A e The effective cross-sectional area (the cross-sectional area of ​​the air gap or iron core, through which the magnetic field is mainly conducted); L p For a certain type of inductance (such as "primary inductance," "equivalent inductance related to permanent magnets," etc., which reflects the magnetic energy storage capacity); μ e The effective permeability of the iron core (describing the iron core's ability to conduct magnetic fields, much greater than μ0; l) e This is the effective length of the iron core (the path length that the magnetic field travels inside the iron core).

[0035] In this embodiment, when the leakage inductance of the leakage inductance magnetic circuit is 3mH, the air gap length in the leakage inductance magnetic circuit is 1.4mm.

[0036] In this application, the influence of winding slots on the magnetic field distribution is analyzed based on Maxwell's equations (especially Ampère's circuital law and Faraday's law of electromagnetic induction):

[0037] (1) Slotting effect.

[0038] Distributing the windings into multiple slots results in a more discrete conductor spatial distribution, leading to: 1) Reduced magnetic field harmonics: Concentrated windings generate high-amplitude spatial harmonic magnetic fields, while the slotted design makes the magnetomotive force distribution closer to sinusoidal (the amplitude of higher harmonics is reduced as can be seen through Fourier decomposition); 2) Reduced local magnetic field strength: Increased conductor spacing weakens the magnetic field coupling strength between adjacent conductors.

[0039] (2) Regulation mechanism of parasitic capacitance.

[0040] Parasitic capacitance mainly originates from electric field coupling between conductors (between turns, between layers, and to ground), and is related to potential difference and dielectric properties. Slotted design breaks down the concentrated winding into multiple physically isolated small units, resulting in: 1) Reduced potential difference between conductors: The average voltage gradient between conductors in adjacent slots decreases (e.g., each segment in a segmented winding only bears a portion of the total voltage), directly reducing inter-turn capacitance; 2) Dispersed electric field distribution: The spatial distribution of the potential, determined by the Poisson equation, is more uniform, and the edge electric field strength is weakened, reducing capacitance to ground. For example, when high-frequency transformers use layered slotted winding, inter-layer capacitance can be reduced by 30%-50%.

[0041] (3) Changes in leakage inductance characteristics.

[0042] Leakage inductance is determined by the energy of the leakage magnetic field not coupled to the common magnetic circuit, and can be obtained by integrating the magnetic field energy. Analysis: Extended leakage flux path: The slotted design increases the spatial distance between windings, forcing the leakage flux B to be extended. leak A longer path leads to increased magnetic reluctance and increased leakage inductance L. leak Increase. Local flux cancellation: Distributed windings (such as short-pitch windings in AC motors) can partially cancel harmonic magnetic fields through phase difference, reducing the high-frequency components of leakage flux.

[0043] (4) Design trade-offs and optimization

[0044] The trade-off between parasitic capacitance and leakage inductance: Slotting reduces capacitance but increases leakage inductance, requiring a trade-off based on the application. For example, in high-frequency applications: prioritize reducing capacitance (to reduce switching losses), while a moderate increase in leakage inductance is acceptable.

[0045] Efficiency first: Leakage inductance (affects voltage regulation) and capacitance (affects EMI) need to be balanced.

[0046] Advanced methods: Combine conductor stranding (Litz wire, enameled wire, fully insulated wire, etc.) and optimization of in-slot insulation materials to further control electromagnetic parameters.

[0047] In summary, the winding slot design significantly alters the parasitic parameters of the system by reconstructing the spatial distribution of the magnetic field.

[0048] (1) Reduce parasitic capacitance: This is achieved by dispersing the electric field and reducing the local potential difference.

[0049] (2) Increase leakage inductance: due to the increased magnetic resistance of the leakage magnetic path and the weakening of magnetic field coupling.

[0050] This effect can be quantitatively verified through finite element simulation (such as ANSYS Maxwell) or analytical models (such as the winding function method), providing key degrees of freedom for the high-frequency and high-efficiency design of electromagnetic equipment.

[0051] In high-frequency power electronic equipment (such as high-frequency transformers, motors, and inductors), the slotted design of windings not only affects electromagnetic performance but also directly relates to thermal management efficiency. Heat generation primarily originates from Joule losses and high-frequency additional losses (eddy current losses, hysteresis losses, etc.), while heat dissipation capacity depends on the heat conduction path and the uniformity of temperature distribution. The following section analyzes in detail how slotted design optimizes thermal management from the perspective of combining electromagnetic theory and thermodynamics:

[0052] (1) Theoretical analysis of the heat source.

[0053] 1) Reduction of Joule loss.

[0054] Current distribution optimization: According to Ampere's law, slot design can reduce the skin depth and proximity effect of conductors by dispersing the conductors (such as splitting a single large winding into multiple small slot windings).

[0055] Skin effect suppression: At high frequencies, the current tends to be on the conductor surface. After slotting, the cross-sectional area of ​​a single conductor is reduced, effectively utilizing the conductor cross-sectional area and reducing AC resistance.

[0056] Neighborhood effect reduction: The magnetic field coupling between adjacent conductors is reduced, thus reducing the additional eddy current losses caused by the proximity effect.

[0057] 2) Suppression of high-frequency additional losses.

[0058] Eddy current loss: According to Faraday's law of electromagnetic induction, slotted design can reduce the rate of change of local magnetic field. Distributed windings reduce the amplitude of magnetic flux density in the slots, thus significantly reducing eddy current loss.

[0059] Hysteresis loss: After slotting, the magnetic field harmonics are reduced (verified by Fourier decomposition), and the core material operates in a more stable loop region, thus reducing hysteresis loss.

[0060] (2) Optimization mechanism for heat dissipation performance of slotted compartments.

[0061] 1) Improvement of heat conduction path.

[0062] The slotted design physically increases the contact area between the windings and the cooling medium (such as air, oil, or radiator). According to Fourier's law of heat conduction, the thermal conductivity and thickness of the inter-slot insulation material (such as epoxy resin, bakelite skeleton PM9823, 9630, T375, etc.) need to be optimized to balance electrical insulation and heat conduction.

[0063] Example: Using high thermal conductivity insulating materials (such as aluminum nitride-filled epoxy resin) can reduce inter-slot thermal resistance.

[0064] 2) Temperature distribution is made more uniform.

[0065] Concentrated windings can lead to localized hot spots, while slotted design disperses heat sources, resulting in a more uniform temperature distribution.

[0066] The Poisson heat equation can be used to quantitatively analyze that the heat source density decreases after the slots are divided, and the temperature rise gradient decreases.

[0067] 3) Improved cooling efficiency.

[0068] The slotted structure forms a natural air duct or liquid cooling channel, enhancing the convective heat transfer coefficient.

[0069] Example of a high-frequency transformer with magnetic components: segmented windings combined with oil-cooled pipes improve heat dissipation efficiency by more than 30%.

[0070] (4) Comprehensive consideration of high frequency reliability.

[0071] At high frequencies, rising temperatures increase the resistivity of the conductor, further exacerbating heat generation. The slotted design breaks this positive feedback loop by controlling the temperature rise.

[0072] The Arrhenius model shows that for every 10°C decrease in temperature, the lifespan of insulation materials doubles. Slotted design can reduce hotspot temperatures by 15-30°C, significantly improving equipment MTBF (Mean Time Between Failures).

[0073] In summary, the winding slot design improves high-frequency reliability through electromagnetic-thermal synergistic optimization:

[0074] (1) Reduce heat generation: suppress skin / proximity effect, reduce eddy current and hysteresis loss.

[0075] (2) Enhance heat dissipation: optimize heat conduction path, homogenize temperature field, and adapt to efficient cooling methods.

[0076] In practical design, it is necessary to combine finite element thermal simulation (such as ANSYS Fluent) and electromagnetic simulation (such as JMAG) to find the optimal solution between minimizing losses and maximizing heat dissipation. For example, after adopting slotted windings, the peak temperature rise of the drive motor of an electric vehicle can be reduced by 20%-40% while maintaining high efficiency and high power density.

[0077] The magnetic device provided in this embodiment can also be applied to the following scenarios:

[0078] High-frequency power supplies: such as 48V-12V DC / DC converters (1-3MHz) for data centers, and on-board chargers (OBCs) for vehicles.

[0079] Resonant converter: The LLC topology uses high leakage inductance as the resonant inductor to simplify the circuit structure.

[0080] RF power applications: such as the power supply network for 5G base station PAs, which requires ultra-low capacitance and inductance.

[0081] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0082] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A magnetic device used in a switching converter, characterized in that, include: The system comprises a frame, a main magnetic core, a leakage magnetic core, and two or more windings; the frame is provided with a main magnetic core receiving slot, a leakage magnetic core receiving slot, and two or more winding receiving slots; the winding receiving slots include multiple sub-slots; the main magnetic core is installed in the main magnetic core receiving slot; the leakage magnetic core is installed in the leakage magnetic core receiving slot; different windings are wound in different winding receiving slots, and the same winding is wound in at least two sub-slots of the same winding receiving slot.

2. The magnetic device applied to a switching converter according to claim 1, characterized in that, The central column of the main magnetic core passes through each winding, forming a common magnetic circuit.

3. The magnetic device applied to a switching converter according to claim 2, characterized in that, The leakage magnetic core is located in the gap between adjacent windings, forming an independent leakage magnetic circuit.

4. The magnetic device applied to a switching converter according to claim 3, characterized in that, The leakage inductance of the leakage inductance magnetic circuit is determined by the leakage magnetic field energy that is not coupled to the common magnetic circuit.

5. The magnetic device applied to a switching converter according to claim 3, characterized in that, When the leakage inductance of the leakage inductance magnetic circuit is 3mH, the air gap length in the leakage inductance magnetic circuit is 1.4mm.

6. The magnetic device applied to a switching converter according to claim 1, characterized in that, The average voltage gradient between conductors in adjacent slots decreases.

7. The magnetic device applied to a switching converter according to claim 1, characterized in that, The leakage magnetic core is made of a low magnetic resistance material.

8. The magnetic device applied to a switching converter according to claim 1, characterized in that, Insulating material is installed between adjacent compartments.

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