Planar magnetic integrated transformer design method based on CLLC converter
Through the design of a planar magnetic integrated transformer based on CLLC converter, the problems of large volume weight, high loss and uneven heat distribution of traditional discrete magnetic components are solved, and the high power density and high efficiency of the converter are achieved.
Patent Information
- Application Number
- CN202510535511.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-25
- Publication Date
- 2025-08-08
AI Technical Summary
The traditional discrete magnetic component design has problems such as large volume weight, significant high-frequency parasitic parameters, increased resistance loss and uneven heat distribution. Especially in application scenarios with high power density requirements such as new energy vehicles and aerospace, it affects the miniaturization of the system and the improvement of efficiency.
The planar magnetic integrated transformer design method based on CLLC converter is adopted, and the core model and geometric parameters are determined through the minimum core structure constant method, the winding turns and spacing are calculated, the winding arrangement method and air gap length are optimized, the number of magnetic components is reduced, and the leakage inductance is used to replace the resonant inductance, and the loss is optimized.
It improves the power density of the converter, reduces losses, improves electromagnetic performance, and ensures safe operation efficiency.
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Figure CN120449567A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of converter design, and in particular to a design method of a planar magnetic integrated transformer based on a CLLC converter. Background Art
[0002] Traditional discrete magnetic component designs mostly use wound core structures. This type of structure has problems such as large size and weight, significant high-frequency parasitic parameters, and uneven three-dimensional magnetic and thermal distribution. Especially in application scenarios with strict power density requirements such as new energy vehicles and aerospace, discrete magnetic components will significantly restrict system miniaturization and efficiency improvement. With the development of high-frequency switching power supplies, the skin effect and proximity effect caused by traditional winding processes have intensified, which not only increases AC resistance loss but also causes reliability risks due to local hot spots. Planar magnetic integration technology integrates magnetic components such as transformers and inductors into a planar core structure, using a flat winding layout to reduce leakage inductance and parasitic capacitance, thereby improving electromagnetic performance under high-frequency conditions. Summary of the Invention
[0003] The purpose of the present invention is to provide a planar magnetic integrated transformer design method based on CLLC converter, which can design the planar transformer based on magnetic integration technology, reduce the number of magnetic components in the converter, and improve the power density of the converter.
[0004] To achieve the above object, the present invention provides the following solutions:
[0005] A design method for a planar magnetic integrated transformer based on a CLLC converter, comprising:
[0006] According to the design parameters of the CLLC converter, the minimum core structure constant method is used to determine the core model and core structure geometric parameters;
[0007] Based on the structure and design parameters of the planar transformer, the number of turns of the primary and secondary windings and the winding spacing are calculated. Based on the impact of different winding arrangements on leakage inductance and winding losses, the corresponding number of turns and arrangement of the windings in the corresponding side columns are determined.
[0008] Compare the effects of different air gap lengths on the magnetizing inductance and leakage inductance of planar transformers to determine the optimal air gap length;
[0009] The planar magnetic integrated transformer is wound using the designed winding arrangement and air gap length.
[0010] Optionally, the method of determining the core model and core structure geometric parameters using a minimum core structure constant method according to the CLLC converter design parameters specifically includes:
[0011] According to the design parameters of the CLLC converter, by searching the data sheets of different magnetic core models and comparing and screening multiple cores based on key parameters such as core magnetic permeability, saturation flux density, and core loss ratio, the minimum core structure constant method is used to calculate the minimum core size that meets the design parameter requirements of the CLLC converter.
[0012] Optionally, the number of turns and winding spacing of the primary and secondary windings are calculated based on the planar transformer structure and design parameters. Based on the impact of different winding arrangements on leakage inductance and winding loss, the corresponding number of turns and arrangement of the windings are determined in the corresponding side columns, specifically including:
[0013] Calculate the number of turns of the primary and secondary windings and the winding spacing, analyze the impact of different winding arrangements on leakage inductance and winding losses within the design requirements, and establish the relationship between leakage inductance and winding losses and different winding arrangements.
[0014] Optionally, the effects of different air gap lengths of the planar transformer on the magnetizing inductance and leakage inductance are compared to determine the optimal air gap length, specifically including:
[0015] Using the influence of the different air gap lengths on the excitation inductance and leakage inductance, a variation curve of the excitation inductance and leakage inductance at different air gap lengths is drawn;
[0016] Select the optimal air gap length based on the planar transformer design requirements.
[0017] Optionally, the planar magnetic integrated transformer is wound using the designed winding arrangement and air gap length, specifically including:
[0018] By utilizing the optimal winding arrangement and air gap length, the planar magnetic integrated transformer loss is minimized within the operating range of the CLLC converter, thereby completing the planar transformer design.
[0019] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:
[0020] The present invention discloses a design method for a planar magnetic integrated transformer based on a CLLC converter, the method comprising: determining a core model and core structure geometric parameters using a minimum core structure constant method according to CLLC converter design parameters; calculating the number of turns of the primary and secondary windings and the winding spacing according to the planar transformer structure and design parameters, and determining the corresponding number of turns and arrangement of the windings in the corresponding side columns according to the influence of different winding arrangements on the leakage inductance and winding loss; comparing the influence of different air gap lengths of the planar transformer on the excitation inductance and leakage inductance to determine the optimal air gap length; and winding the planar magnetic integrated transformer using the designed winding arrangement and air gap length. The present invention applies the planar magnetic integrated transformer design method to the CLLC converter, can design the planar transformer based on magnetic integration technology, reduce the number of magnetic components in the converter, and improve the power density of the converter; at the same time, optimize the loss of the planar transformer, and improve the overall operating efficiency while ensuring safe operation. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0022] Figure 1 Schematic diagram of the flow of the design method of a planar magnetic integrated transformer based on a CLLC converter of the present invention;
[0023] Figure 2 CLLC converter topology diagram in this embodiment;
[0024] Figure 3 : is a structural diagram of the magnetic integrated transformer in this embodiment;
[0025] Figure 4 Schematic diagrams of different winding arrangements in this embodiment; among them, part (a) is a schematic diagram of a non-interwoven arrangement, part (b) is a schematic diagram of a fully interwoven arrangement; part (c) is a schematic diagram of a semi-symmetrical interwoven arrangement; part (d) is a schematic diagram of a semi-symmetrical staggered II arrangement; and part (e) is a schematic diagram of an anti-symmetrical staggered arrangement. DETAILED DESCRIPTION
[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.
[0027] The purpose of the present invention is to provide a planar magnetic integrated transformer design method based on CLLC converter, which can design the planar transformer based on magnetic integration technology, reduce the number of magnetic components in the converter, and improve the power density of the converter.
[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0029] like Figure 1 As shown, the present invention provides a design method for a planar magnetic integrated transformer based on a CLLC converter, comprising:
[0030] Step 100: Determine the core model and core structure geometric parameters using the minimum core structure constant method based on the CLLC converter design parameters. Specifically, the steps include:
[0031] According to the design parameters of the CLLC converter, by searching the data sheets of different magnetic core models and comparing and screening multiple cores based on key parameters such as core magnetic permeability, saturation flux density, and core loss ratio, the minimum core structure constant method is used to calculate the minimum core size that meets the design parameter requirements of the CLLC converter.
[0032] Step 200: Calculate the number of turns and winding spacing of the primary and secondary windings based on the planar transformer structure and design parameters, and determine the corresponding number of turns and arrangement of the windings in the corresponding side columns based on the impact of different winding arrangements on leakage inductance and winding losses. This specifically includes:
[0033] Calculate the number of turns of the primary and secondary windings and the winding spacing, analyze the impact of different winding arrangements on leakage inductance and winding losses within the design requirements, and establish the relationship between leakage inductance and winding losses and different winding arrangements.
[0034] Step 300: Comparing the effects of different air gap lengths on the magnetizing inductance and leakage inductance of the planar transformer to determine the optimal air gap length; specifically, including:
[0035] The influence of different air gap lengths on the excitation inductance and leakage inductance is used to draw the variation curves of the excitation inductance and leakage inductance at different air gap lengths; and the optimal air gap length is selected according to the design requirements of the planar transformer.
[0036] Step 400: Winding the planar magnetic integrated transformer using the designed winding arrangement and air gap length; specifically comprising:
[0037] By utilizing the optimal winding arrangement and air gap length, the planar magnetic integrated transformer loss is minimized within the operating range of the CLLC converter, thereby completing the planar transformer design.
[0038] Based on the above technical solution, the following embodiments are provided.
[0039] When the switching frequency of the CLLC converter based on traditional discrete magnetic components increases, especially at high frequencies, the skin effect and proximity effect of the traditional discrete magnetic components are intensified, which increases the AC resistance loss and seriously reduces the efficiency of the converter.
[0040] Therefore, this embodiment is intended to solve the following problems: 1. The problem of large size and weight of CLLC converter under traditional discrete magnetic components; 2. The problem of aggravated AC resistance loss under high frequency of traditional discrete magnetic components; 3. The problem of uneven heat distribution of traditional discrete magnetic components.
[0041] This embodiment discloses a design method for a planar magnetic integrated transformer based on a CLLC converter. The CLLC topology consists of a primary full bridge, a secondary full bridge, a primary-secondary resonant capacitor, a primary-secondary resonant inductor, a magnetizing inductor, a high-frequency isolation transformer, and three bypass capacitors. Both the primary and secondary full bridges are composed of four switching transistors and anti-parallel diodes. This topology reduces the voltage stress on the switching transistors and improves the converter's flexibility, enabling its application in higher voltage applications, such as solid-state transformers, electric vehicles, and medium-voltage DC power grids.
[0042] Typically, converters use traditional discrete magnetic component designs as transformer design methods. However, this design increases transformer loss design difficulty during high-frequency operation and leads to disadvantages such as reduced converter efficiency and uneven magnetic and thermal distribution. To improve this situation, this embodiment adopts a design method using planar magnetic integration technology. Compared to traditional discrete magnetic component designs, the planar magnetic integration technology of this embodiment generates a certain amount of large leakage inductance in the transformer, which is used instead of the resonant inductance, thereby reducing the number of magnetic components.
[0043] First, according to the design parameters of the CLLC converter, the minimum core structure constant method is used to determine the core model and core structure geometric parameters; according to the planar transformer structure and design parameters, the number of primary and secondary winding turns and the winding spacing are calculated, and according to the influence of different winding arrangements on the leakage inductance and winding loss, the corresponding number of winding turns and arrangement methods are determined in the corresponding side columns; the influence of different air gap lengths of the planar transformer on the excitation inductance and leakage inductance is compared to determine the optimal air gap length; and the designed winding arrangement and air gap length are used to wind the planar magnetic integrated transformer.
[0044] In the above solution, the planar transformer is designed based on magnetic integration technology to reduce the number of magnetic components in the converter and improve the power density of the converter; at the same time, the loss of the planar transformer is optimized to improve the overall operating efficiency while ensuring safe operation.
[0045] In addition, as shown in the transformer design process, the steps are:
[0046] S1: Based on the design parameters of the CLLC converter, the minimum core structure constant method is used to determine the core model and core structure geometric parameters;
[0047] S2: Based on the planar transformer structure and design parameters, calculate the number of turns and winding spacing of the primary and secondary windings. Based on the impact of different winding arrangements on leakage inductance and winding losses, determine the corresponding number of winding turns and arrangement in the corresponding side column.
[0048] S3: Compare the effects of different air gap lengths on the magnetizing inductance and leakage inductance of the planar transformer to determine the optimal air gap length;
[0049] S4: Winding the planar magnetic integrated transformer using the designed winding arrangement and air gap length.
[0050] The design method proposed in this example uses leakage inductance instead of resonant inductance in traditional discrete magnetic components. Under this premise, the above scheme operates the converter at high frequency to address the problems of reduced converter efficiency and uneven magnetic and thermal distribution. Based on the structure and design parameters of the planar transformer, the number of turns and winding spacing of the primary and secondary windings are calculated. Based on the impact of different winding arrangements on leakage inductance and winding losses, the corresponding number of winding turns and arrangement within the corresponding side column are determined. The effects of different air gap lengths on the excitation inductance and leakage inductance of the planar transformer are compared to determine the optimal air gap length. Finally, the planar magnetic integrated transformer is wound using the designed winding arrangement and air gap length.
[0051] In this example, a planar transformer is designed based on magnetic integration technology to reduce the number of magnetic components in the converter and increase the converter's power density. At the same time, the planar transformer's losses are optimized to improve overall operating efficiency while ensuring safe operation. Furthermore, in this implementation patent, the transformer design based on planar magnetic integration technology can improve the transformer's large size and weight, as well as its low power density, by replacing the resonant inductor with leakage inductance. The arrangement of the windings improves the transformer's distributed parameters, optimizing the planar transformer's losses and improving overall operating efficiency while ensuring safe operation.
[0052] It should be noted that the CLLC converter topology is as follows Figure 2 The primary full bridge is composed of 4 switch tubes (S1-S4), the secondary full bridge is composed of 4 switch tubes (S5-S8), the primary and secondary resonant capacitors (C r1 , C r2 ), primary and secondary side resonant inductance (L r1 , L r2 ), excitation inductance (L m ), high frequency isolation transformer T and two bypass capacitors (C1, C2). The input side DC voltage source is V in , the output side DC voltage source is V out , the transformer ratio is n:1.
[0053] The design method of a planar magnetic integrated transformer based on a CLLC converter specifically includes the following steps:
[0054] In the first step, the minimum core structure constant method is used to determine the core model and core structure geometric parameters based on the CLLC converter design parameters.
[0055] According to the design parameters of the CLLC converter, by searching the data sheets of different magnetic core models and comparing and screening multiple cores based on key parameters such as core magnetic permeability, saturation flux density, and core loss ratio, the minimum core structure constant method is used to calculate the minimum core size that meets the design parameter requirements of the CLLC converter.
[0056] In this example, the transformer design parameters are used as the initial input of the present invention. The transformer design parameters include the turns ratio of the primary and secondary windings n:1, the primary winding current i r1 , secondary winding coil current i r2 , primary resonant inductance value L r1 , secondary side resonant inductance value L r2 , transformer primary excitation inductance L m , switching frequency f.
[0057] The core model is the specific model of the selected EE core. Please refer to Figure 3 The structure of the magnetic integrated transformer proposed by the present invention is as follows Figure 3 As shown, the transformer core adopts an EE-type core structure, the primary winding coil and the secondary winding coil are wound on the left and right side columns of the core, and the air gap is evenly distributed on the middle column and side columns of the core.
[0058] The preset area product method is the minimum core structure constant method.
[0059]
[0060] Where k h is the height coefficient, which is a constant considering the spacing between the layers and has a value between 1.1 and 1.3; t is the thickness of the PCB board; η is the transformer efficiency; k f is the waveform factor. In the CLLC converter, the primary and secondary voltages of the transformer are both square waves, so k f is 4; B m is the maximum working magnetic flux density; f is the minimum working frequency; J is the current density; H c P is the copper thickness of PCB printed wire; o is the transformer power; U p and U s are the peak voltages of the primary and secondary sides of the transformer respectively; w dp and w ds are the turn spacings of the primary and secondary windings respectively.
[0061] The second step is to calculate the number of turns and winding spacing of the primary and secondary windings based on the planar transformer structure and design parameters. Based on the impact of different winding arrangements on the leakage inductance and winding losses, the corresponding number of winding turns and arrangement methods are determined in the corresponding side columns.
[0062] In this example, five winding layout structures are analyzed. Figure 4 shown.
[0063] Structure (a): The primary and secondary windings are distributed on both sides of the winding, forming a non-interwoven arrangement. The windings from top to bottom are: P1-P2-P3-P4-P5-S1-S2-S3-S4-S5;
[0064] Structure (b): The primary and secondary windings are completely interlaced to form a fully interwoven arrangement. The windings from top to bottom are: P1-S1-P2-S2-P3-S3-P4-S4-P5-S5;
[0065] Structure (c): The primary winding is arranged on the outside, and the primary winding and the secondary winding are not completely staggered, forming a semi-symmetrical interlaced arrangement. The winding order from top to bottom is: P1-S1-S2-P2-P3-S3-P4-S4-S5-P5;
[0066] Structure (d): The primary winding is arranged on the outside, and the primary and secondary windings are not completely staggered, forming a semi-symmetrical staggered II arrangement. The windings from top to bottom are: P1-P2-S1-S2-P3-S3-S4-S5-P4-P5;
[0067] Structure (e): The primary winding is placed on the outside, and the primary and secondary windings are arranged in an antisymmetrical staggered arrangement. The windings from top to bottom are: P1-P2-S1-S2-S3-P3-P4-P5-S4-S5.
[0068] Analysis of winding losses for different winding methods, taking into account skin effect and proximity effect, the loss of single-layer copper foil winding is:
[0069]
[0070] Where H2 is the magnetic field strength on the upper surface of the winding; H1 is the magnetic field strength on the lower surface of the winding; σ is the conductivity of the winding material; W is the winding width; λ = h / δ, where δ is the skin depth and h is the winding thickness.
[0071] The finite element analysis tool ANSYS Maxwell software is used to simulate and analyze the transformer under different parallel winding layouts. The eddy current field is used to simulate the influence of proximity effect on winding loss at high frequency and the transformer winding loss under different parallel winding layouts.
[0072] The third step is to compare the effects of different air gap lengths on the excitation inductance and leakage inductance of the planar transformer to determine the optimal air gap length.
[0073] The magnitude of the transformer leakage inductance is determined by the magnetic field strength of each winding layer. Therefore, different winding layouts will lead to significant differences in leakage inductance due to different magnetic field strength distributions. According to the magnetic field strength distribution diagram of the planar transformer winding, the magnetic field strength on each winding layer can be obtained. The energy stored in the leakage magnetic field should be equal to the sum of the energy stored in each layer of the medium in the core window. Therefore, the energy stored in the leakage magnetic field E leakage for:
[0074]
[0075] The transformer primary leakage inductance L can be obtained lp for:
[0076]
[0077] The finite element analysis tool ANSYS Maxwell software was used to simulate and analyze the transformer under different parallel winding layouts, and the leakage inductance of the transformer under different parallel winding layouts was obtained using two-dimensional eddy current field simulation.
[0078] The fourth step is to wind the planar magnetic integrated transformer using the designed winding arrangement and air gap length.
[0079] Finally, the PCB winding that implements this design method is proofed, the PCB winding is placed on the side column of the magnetic core and the air gap length is controlled, and the design method of the planar magnetic integrated transformer based on the CLLC converter is realized.
[0080] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.
[0081] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.
Claims
1. A design method for a planar magnetic integrated transformer based on a CLLC converter, characterized in that: include: According to the design parameters of the CLLC converter, the minimum core structure constant method is used to determine the core model and core structure geometric parameters; Based on the structure and design parameters of the planar transformer, the number of turns of the primary and secondary windings and the winding spacing are calculated. Based on the impact of different winding arrangements on leakage inductance and winding losses, the corresponding number of turns and arrangement of the windings in the corresponding side columns are determined. Compare the effects of different air gap lengths on the magnetizing inductance and leakage inductance of planar transformers to determine the optimal air gap length; The planar magnetic integrated transformer is wound using the designed winding arrangement and air gap length.
2. The design method of a planar magnetic integrated transformer based on a CLLC converter according to claim 1, characterized in that: According to the design parameters of the CLLC converter, the minimum core structure constant method is used to determine the core model and core structure geometric parameters, including: According to the design parameters of the CLLC converter, by searching the data sheets of different magnetic core models and comparing and screening multiple cores based on key parameters such as core magnetic permeability, saturation flux density, and core loss ratio, the minimum core structure constant method is used to calculate the minimum core size that meets the design parameter requirements of the CLLC converter.
3. The design method of a planar magnetic integrated transformer based on a CLLC converter according to claim 1, characterized in that: Based on the planar transformer structure and design parameters, the number of turns and winding spacing of the primary and secondary windings are calculated. Based on the impact of different winding arrangements on leakage inductance and winding losses, the corresponding number of turns and arrangement of windings in the corresponding side columns are determined. Specifically, the following are included: Calculate the number of turns of the primary and secondary windings and the winding spacing, analyze the impact of different winding arrangements on leakage inductance and winding losses within the design requirements, and establish the relationship between leakage inductance and winding losses and different winding arrangements.
4. The design method of a planar magnetic integrated transformer based on a CLLC converter according to claim 1, characterized in that: Compare the effects of different air gap lengths on the magnetizing inductance and leakage inductance of planar transformers to determine the optimal air gap length, specifically including: Using the influence of the different air gap lengths on the excitation inductance and leakage inductance, a variation curve of the excitation inductance and leakage inductance at different air gap lengths is drawn; Select the optimal air gap length based on the planar transformer design requirements.
5. The design method of a planar magnetic integrated transformer based on a CLLC converter according to claim 1, wherein: The planar magnetic integrated transformer is wound using the designed winding arrangement and air gap length, specifically including: By utilizing the optimal winding arrangement and air gap length, the loss of the planar magnetic integrated transformer is minimized within the operating range of the CLLC converter, thereby completing the design of the planar transformer.