Hybrid magnetic core transformer and optimized design method thereof

Abstract

The application provides a hybrid magnetic core transformer and an optimization design method thereof, and belongs to the technical field of power electronic magnetic devices. In view of the problems that the existing high-frequency transformer is prone to core saturation under the condition of existing DC bias and the single nanocrystalline core has a large loss under high-frequency conditions, the transformer comprises a ferrite center column magnetic core, a nanocrystalline yoke magnetic core frame, a winding assembly and an air gap component, the ferrite center column magnetic core and the nanocrystalline yoke magnetic core frame are combined to form a double-E type composite magnetic circuit, the winding assembly is sleeved on the outer side of the ferrite center column magnetic core, and the air gap component is arranged at the axial end of the ferrite center column magnetic core. The optimization design method determines the air gap parameters and assembly parameters by establishing an equivalent parallel magnetic circuit model and combining finite element simulation, so as to take into account high-frequency loss control and DC bias resistance, and is suitable for high-frequency power electronic conversion devices.

Description

Technical Field

[0001] This invention belongs to the field of power electronic magnetic components technology, and in particular relates to a hybrid magnetic core transformer and its optimized design method. Background Technology

[0002] In high-frequency power electronic converters, transformers not only perform energy transfer but also directly affect the overall size, efficiency, and temperature rise of the device, thus making them critical magnetic components. With increasing switching frequencies and power ratings, transformer design typically needs to balance loss control under high-frequency conditions with anti-saturation capability under bias conditions.

[0003] Most existing high-frequency transformers use ferrite cores. Ferrite materials have low core losses in the high-frequency range, making them suitable for high-frequency energy conversion applications; however, their saturation magnetic flux density is relatively low. When the transformer operates in a topology with DC bias or low-frequency bias components, the ferrite core is prone to localized magnetic flux density increases, leading to saturation risk and limiting the design margin of the transformer under high-power conditions. To avoid saturation, it is usually necessary to increase the core size or reduce the operating magnetic flux density, which further affects power density and efficiency.

[0004] Nanocrystalline materials possess high saturation magnetic induction and strong bias resistance. However, if the entire core is made of nanocrystalline material, its relatively high volumetric loss under high-frequency conditions can negatively impact overall efficiency. On the other hand, the traditional approach of simply adding an air gap to improve saturation resistance, while alleviating bias problems to some extent, can also introduce increased leakage inductance, enhanced edge effects, and aggravated magnetic field leakage. Therefore, improving the transformer's performance under DC bias conditions without significantly increasing high-frequency losses remains a key technical challenge in this field. Summary of the Invention

[0005] In view of this, the present invention aims to provide a hybrid core transformer and its optimized design method to at least solve one of the problems in the background art.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A hybrid core transformer includes a central core made of ferrite material, a side yoke core frame made of nanocrystalline material, a double-E type magnetic circuit formed by splicing the central core with the central core, a winding wound on the double-E type central core, and an air gap disposed on the E type central core, wherein the length of the air gap is... The design ensures that, when the transformer is operating, the amplitude of the AC magnetic flux density flowing through the ferrite core is... The DC magnetic flux density flowing through the ferrite column is within the optimal loss range of the ferrite material at the corresponding operating frequency. The total magnetic flux density flowing through the nanocrystalline edge pillars is suppressed below a preset safety threshold. () is lower than its saturation magnetic flux density; The nanocrystalline edge yoke core frame includes two edge pillars and a yoke connecting the two edge pillars. The ferrite central pillar core is disposed in the central region enclosed by the nanocrystalline edge yoke core frame and is assembled with the nanocrystalline edge yoke core frame to form a double E-type composite magnetic circuit. The winding assembly is sleeved on the outside of the ferrite core; The air gap component is disposed at the axial end of the ferrite core to form an air gap in the magnetic circuit where the ferrite core is located.

[0007] Furthermore, the winding assembly includes a frame, a primary winding, and a secondary winding. The frame is sleeved on the outside of the ferrite core, and the primary winding and the secondary winding are wound on the frame.

[0008] Furthermore, the nanocrystalline edge yoke core frame is formed by winding, annealing and processing nanocrystalline strip into an integral frame structure. The bonding surface between the ferrite central core and the nanocrystalline edge yoke core frame is connected by a thermally conductive insulating material. A clamping and fixing structure is provided on the outside of the ferrite central core and the nanocrystalline edge yoke core frame. The ratio of the sum of the effective cross-sectional areas of the two edge columns of the nanocrystalline edge yoke core frame to the effective cross-sectional area of ​​the ferrite E-type central core is between 0.8 and 1.2.

[0009] Furthermore, the air gap component is an insulating pad disposed at one or both ends of the ferrite core, and the total thickness of the insulating pad corresponds to the length of the air gap.

[0010] Furthermore, the length of the air gap Determined through the following steps: a. Based on the transformer's power ,frequency Estimating DC bias magnetomotive force based on input / output voltage and topology: ( (1) b. Establish an equivalent parallel magnetic circuit model for the hybrid magnetic core, wherein the magnetic reluctance of the ferrite core pillar branch is... Included by Determined air gap magnetic reluctance Nanocrystalline side pillar branch magnetoresistance It is determined by the magnetic permeability of nanocrystals under bias; c. Setting Constraints: (2) in, For the preset range, The first threshold, Using the second threshold, the required air gap length is determined through iterative calculation and finite element simulation to satisfy the given conditions. .

[0011] Furthermore, the insulating pad is made of polyimide, mica, or engineering plastic and is attached to the end face of the ferrite core.

[0012] Furthermore, this solution discloses an optimized design method for a hybrid core transformer, applicable to the aforementioned hybrid core transformer, comprising the following steps: S1. Determine the estimated value or range of the transformer's operating topology, rated power, operating frequency, input voltage, output voltage, and DC bias ampere-turns. S2. Based on the area product method, the overall size of the magnetic core is initially selected, and the effective cross-sectional area of ​​the ferrite core is determined. and magnetic circuit length and the effective cross-sectional area of ​​the nanocrystalline side pillars and magnetic circuit length ; S3. Establish an equivalent parallel magnetic circuit model consisting of ferrite branches and nanocrystalline branches, and calculate the initial value of the air gap length based on the estimated value or range of the DC bias ampere-turns, the magnetic circuit parameters of the ferrite core, and the magnetic circuit parameters of the nanocrystalline side pillars. S4. Establish a parameterized finite element model with air gap length as the variable. Apply an excitation containing DC bias and AC components to the parameterized finite element model and perform parameter scanning and transient field simulation to obtain the magnetic flux density waveforms of the ferrite core and nanocrystalline edge pillars corresponding to different air gap lengths. S5. Determine the target air gap length based on the magnetic flux density waveform, and accordingly determine the material and thickness of the insulating pad, as well as the assembly method, heat conduction method, and fixing method of the ferrite core and the nanocrystalline edge yoke core frame.

[0013] Furthermore, after step S4, a loss calculation step is included, which includes: Based on the magnetic flux density waveform of the ferrite core, the loss of the ferrite core is calculated using the improved Steinmetz formula. Based on the loss curves of the nanocrystalline edge pillars under the corresponding DC bias magnetic field strength and operating frequency, and combined with the AC magnetic flux density amplitude obtained from simulation, the loss of the nanocrystalline edge pillars is interpolated and calculated. And calculate the losses of the winding components.

[0014] Furthermore, in step S5, the bonding surface between the ferrite core and the nanocrystalline edge yoke core frame is bonded with thermally conductive insulating adhesive, and pressure is applied during the curing process.

[0015] Furthermore, this solution discloses a power electronic conversion device, including the aforementioned hybrid core transformer.

[0016] Compared with existing technologies, the hybrid core transformer and its optimized design method described in this invention have the following advantages: (1) The present invention uses a ferrite core and a nanocrystalline edge yoke core frame to form a double E-type composite magnetic circuit. In terms of structure, it combines high-frequency low-loss materials with high-saturation magnetic density materials, which can take into account both high-frequency operation requirements and bias load requirements in the same transformer, thereby improving the contradiction that a single material solution cannot simultaneously meet the requirements. (2) In this invention, an air gap component is set at the axial end of the ferrite core, and the air gap parameters are determined by equivalent parallel magnetic circuit modeling and finite element simulation. This allows the air gap to be designed by combining topological conditions, magnetic circuit parameters and simulation results, rather than relying solely on experience. This improves the design accuracy and engineering feasibility of the hybrid core transformer. (3) This invention not only provides the device structure of the hybrid magnetic core transformer, but also provides the corresponding optimization design method, which can systematically design the initial selection of magnetic core size, calculation of initial air gap value, acquisition of magnetic flux density waveform, loss calculation and determination of assembly and heat conduction scheme, which is conducive to shortening the development cycle and improving the consistency and reproducibility of design results; (4) This invention is applicable to power electronic converters with high frequency and DC bias conditions. It has good practical value under high frequency and high power application conditions and can provide support for improving the power density, operating efficiency and operating reliability of converters. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the hybrid core transformer structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the finite element simulation process for air gap optimization design as described in an embodiment of the present invention.

[0018] Figure 3 This is a schematic diagram of the LLC resonant converter circuit of the hybrid magnetic core transformer according to an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures: 1. Ferrite core; 2. Nanocrystalline edge yoke core frame; 3. Spacer; 4. Primary winding; 5. Secondary winding. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] First, regarding the structure of hybrid core transformers, such as Figure 1 As shown, the hybrid core transformer in this embodiment mainly includes a ferrite core 1, a nanocrystalline edge yoke core frame 2, an air gap pad 3, a primary winding 4, and a secondary winding 5.

[0025] The ferrite core 1 is made of a high-frequency, low-loss material. The nanocrystalline edge yoke core frame 2 is made of high-saturation magnetic density nanocrystalline ribbon wound and annealed, forming an integral frame including two edge pillars and a connecting yoke. The air gap pad 3 is made of high-precision polyimide film and is attached to the upper and lower ends of the ferrite core; its total thickness is the required air gap length. During assembly, first wind the winding onto the frame, then insert the ferrite core 1 with the air gap pad 3 already attached into the frame, and finally fasten the nanocrystalline frame 2 from both sides so that the side posts and yoke of the ferrite core are tightly surrounded by the nanocrystalline frame. Finally, use high-temperature tape to bind and fix it, and apply a small amount of high thermal conductivity silicone grease to the mating surface to improve heat dissipation.

[0026] Secondly, regarding the optimization design method, this embodiment is based on the above-mentioned hybrid core transformer structure and details its systematic design method. This method is particularly suitable for high-frequency, high-power application scenarios with significant DC bias, such as LLC resonant converters and active clamp forward converters.

[0027] Furthermore, the application topology, rated power, operating frequency range, input and output voltage of the transformer, as well as the estimated value or range of the DC bias magnetomotive force caused by the topology characteristics, are clearly defined.

[0028] Furthermore, the overall dimensions of the magnetic core were initially selected based on the general area product method, and the effective cross-sectional area of ​​the ferrite cylinders was determined. and magnetic circuit length and the effective cross-sectional area of ​​the nanocrystalline side pillars and magnetic circuit length To ensure magnetic flux continuity, the total cross-sectional area of ​​the nanocrystalline side pillars is matched with the cross-sectional area of ​​the ferrite center pillars.

[0029] Furthermore, an equivalent parallel magnetic circuit model is established. This ensures the AC working magnetic flux density of the ferrite core is... The material is within its low-loss optimization range at the corresponding operating frequency; by adjusting the air gap, the DC magnetic flux density of the ferrite core is reduced. Suppressed at a safe level far below its saturation magnetic flux density; ensuring the total magnetic flux density borne by the nanocrystalline edge pillars. While making full use of its high saturation characteristics, sufficient margin is left.

[0030] Furthermore, based on the estimated DC bias magnetomotive force, the air gap length is initially estimated using the magnetic circuit formula (1). The magnitude.

[0031] (1) A parametric simulation model of the transformer was established using electromagnetic field finite element analysis software. The air gap length was determined. As a key variable, an excitation including rated DC bias and AC components is applied to the model. Different parameters are observed through parameter sweeps and transient field simulations. The magnetic flux density waveforms of the ferrite central pillar and the nanocrystalline edge pillar.

[0032] Through iterative analysis, an optimal [method / mechanism] is selected. The value is set such that the simulation results simultaneously satisfy all the above magnetic flux density constraints. Figure 2 This is a schematic diagram of the optimization design process for this step.

[0033] Furthermore, based on the simulation, the precise magnetic flux density waveforms acting on each part of the magnetic core are obtained. Loss calculations are performed.

[0034] For ferrite cores, the high-frequency core loss is calculated using the improved Steinmetz equation (such as the iGSE model) which is applicable to non-sinusoidal waveforms.

[0035] For nanocrystalline edge pillars, the DC bias magnetic field strength is extracted based on simulation. and AC magnetic flux density amplitude Query the family of core loss curves provided by the material supplier under specific bias and frequency, and obtain its loss value by interpolation.

[0036] Based on the above core losses and the winding losses optimized according to the high-frequency effect, thermal simulation is performed to evaluate the hot spot temperature rise of the transformer under the expected worst operating conditions, ensuring that it operates within a safe temperature range.

[0037] Furthermore, based on the determined The design of the air gap implementation scheme should be considered, such as selecting polyimide material and precision gaskets of appropriate thickness. The assembly sequence of the ferrite core and nanocrystalline frame, the coating process of the thermally conductive interface material at the mating surfaces, and the overall mechanical fixing method should be planned to ensure product reliability and heat dissipation performance.

[0038] like Figure 3 As shown, the hybrid core transformer of the present invention Applied to LLC resonant converters. Due to the transformer... It has excellent DC bias resistance, which allows LLC circuits to operate over a wider range of input voltages and loads without worrying about core saturation caused by magnetizing current, thereby improving the power density and reliability of the whole machine.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hybrid magnetic core transformer, characterized in that, This includes a ferrite core, a nanocrystalline edge yoke core frame, winding assemblies, and air gap components; The nanocrystalline edge yoke core frame includes two edge pillars and a yoke connecting the two edge pillars. The ferrite central pillar core is disposed in the central region enclosed by the nanocrystalline edge yoke core frame and is assembled with the nanocrystalline edge yoke core frame to form a double E-type composite magnetic circuit. The winding assembly is sleeved on the outside of the ferrite core; The air gap component is disposed at the axial end of the ferrite core to form an air gap in the magnetic circuit where the ferrite core is located.

2. The hybrid core transformer according to claim 1, characterized in that, The winding assembly includes a frame, a primary winding, and a secondary winding. The frame is sleeved on the outside of the ferrite core, and the primary winding and the secondary winding are wound on the frame.

3. The hybrid core transformer according to claim 1, characterized in that, The nanocrystalline edge yoke core frame is formed by winding, annealing and processing nanocrystalline strip into an integral frame structure. The joint surface between the ferrite central core and the nanocrystalline edge yoke core frame is connected by a thermally conductive insulating material, and a clamping and fixing structure is provided on the outside of the ferrite central core and the nanocrystalline edge yoke core frame.

4. The hybrid core transformer according to claim 1, characterized in that, The air gap component is an insulating pad disposed at one or both ends of the ferrite core, and the total thickness of the insulating pad corresponds to the length of the air gap.

5. The hybrid core transformer according to claim 4, characterized in that, The length of the air gap Determined through the following steps: a. Based on the transformer's power ,frequency Estimating DC bias magnetomotive force based on input / output voltage and topology: （ ）(1) b. Establish an equivalent parallel magnetic circuit model for the hybrid magnetic core, wherein the magnetic reluctance of the ferrite core pillar branch is... Included by Determined air gap magnetic reluctance Nanocrystalline side pillar branch magnetoresistance It is determined by the magnetic permeability of nanocrystals under bias; c. Setting Constraints: (2) in, For the preset range, The first threshold, Using the second threshold, the required air gap length is determined through iterative calculation and finite element simulation to satisfy the given conditions. .

6. The hybrid core transformer according to claim 4, characterized in that, The insulating pad is made of polyimide, mica or engineering plastic and is attached to the end face of the ferrite core.

7. An optimized design method for a hybrid magnetic core transformer, characterized in that, The hybrid core transformer according to any one of claims 1 to 6 comprises the following steps: S1. Determine the estimated value or range of the transformer's operating topology, rated power, operating frequency, input voltage, output voltage, and DC bias ampere-turns. S2. Based on the area product method, the overall size of the magnetic core is initially selected, and the effective cross-sectional area and magnetic circuit length of the ferrite central core, as well as the effective cross-sectional area and magnetic circuit length of the nanocrystalline edge core are determined respectively. S3. Establish an equivalent parallel magnetic circuit model consisting of ferrite branches and nanocrystalline branches, and calculate the initial value of the air gap length based on the estimated value or range of the DC bias ampere-turns, the magnetic circuit parameters of the ferrite core, and the magnetic circuit parameters of the nanocrystalline side pillars. S4. Establish a parameterized finite element model with air gap length as the variable. Apply an excitation containing DC bias and AC components to the parameterized finite element model and perform parameter scanning and transient field simulation to obtain the magnetic flux density waveforms of the ferrite core and nanocrystalline edge pillars corresponding to different air gap lengths. S5. Determine the target air gap length based on the magnetic flux density waveform, and accordingly determine the material and thickness of the insulating pad, as well as the assembly method, heat conduction method, and fixing method of the ferrite core and the nanocrystalline edge yoke core frame.

8. The optimization design method according to claim 7, characterized in that, Following step S4, a loss calculation step is also included, which includes: Based on the magnetic flux density waveform of the ferrite core, the loss of the ferrite core is calculated using the improved Steinmetz formula. Based on the loss curves of the nanocrystalline edge pillars under the corresponding DC bias magnetic field strength and operating frequency, and combined with the AC magnetic flux density amplitude obtained from simulation, the loss of the nanocrystalline edge pillars is interpolated and calculated. And calculate the losses of the winding components.

9. The optimization design method according to claim 7 or 8, characterized in that, In step S5, the bonding surfaces of the ferrite core and the nanocrystalline edge yoke core frame are bonded with thermally conductive insulating adhesive, and pressure is applied during the curing process.

10. A power electronic conversion device, characterized in that, Including the hybrid core transformer as described in any one of claims 1 to 6.

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