LLC planar magnetic integration method for space navigation

Abstract

The invention discloses an astronavigation-used LLC planar magnetic integration method, which comprises the steps of selecting an EE-type magnetic core, designing three magnetic columns, and ensuring uniform magnetic flux distribution due to the fact that air gaps between a middle column and side columns are equal; the resonant inductor and the transformer of the LLC circuit are integrated on the same EE-type magnetic core, so that the functions of the resonant inductor and the transformer can be realized through the same magnetic core; through the design principle that side column magnetic flux counteracts in a middle column, a magnetic flux path is optimized, and magnetic hysteresis loss is reduced; establishing an equivalent magnetic circuit of LLC planar magnetic integration by applying a magnetic circuit Ohm law, calculating a key inductance value, and converting a magnetic circuit model into a circuit equivalent model through a dual theorem; and designing and optimizing the working mode of the LLC circuit according to the established equivalent circuit model so as to ensure high efficiency and high power density. The resonant inductor and the transformer of the LLC circuit are integrated on the same EE-type magnetic core, so that the size of a magnetic element is effectively reduced, the power density of a power supply is improved, the hysteresis loss is reduced, and the overall efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and in particular relates to a planar magnetic integration method for aerospace LLC. Background Technology

[0002] High power density and miniaturization are the main trends in aerospace power supply design. To achieve miniaturization, the switching frequency is typically increased; however, high frequencies can lead to increased switching losses and exacerbated electromagnetic interference. Therefore, in aerospace applications, high switching frequencies are often combined with soft-switching circuits to ensure power supply efficiency and reliability. Commonly used soft-switching circuits include asymmetrical half-bridges, LLC resonant circuits, phase-shifted full-bridges, and their combinations. Among these, LLC circuits offer cost and size advantages suitable for circuits below 300W because their primary-side switches can achieve ZVS (Zero-Voltage Switching), their secondary-side switches can achieve ZCS (Zero-Coherent Switching), and their transformers have no DC bias.

[0003] In existing technologies, the magnetic components of LLC circuits typically include resonant inductors and transformers. To improve power density and reduce size, various magnetic integration methods have been proposed both domestically and internationally. For example, using the leakage inductance of the transformer as the resonant inductor requires simultaneous control of both leakage inductance and inductance ratio, making engineering implementation difficult. External core integration, while achieving some degree of magnetic integration, faces challenges in meeting the requirements for installation and mechanical response in aerospace applications. Furthermore, while combining multiple magnetic cores and decoupling the magnetic circuit can separate the functions of the resonant inductor and transformer, it requires two magnetic cores, hindering further improvements in power density.

[0004] Therefore, existing technologies have the following problems: First, the magnetic components are large in size and have limited integration; second, some methods increase structural complexity, and the installation and mechanical reliability are difficult to meet aerospace requirements; third, there is a lack of systematic magnetic integration design methods and quantitative analysis tools, which leads to the design process relying on experience and making it difficult to achieve optimal magnetic flux distribution and loss control. Summary of the Invention

[0005] This invention provides a planar magnetic integration method for aerospace LLC to solve existing technical problems.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] A planar magnetic integration method for aerospace LLC includes the following steps:

[0008] S1. Select an EE type magnetic core and design three magnetic pillars, with equal air gaps between the middle pillar and the side pillars to ensure uniform magnetic flux distribution;

[0009] S2. Integrate the resonant inductor and transformer of the LLC circuit onto the same EE-type magnetic core, so that the functions of both can be achieved through the same magnetic core;

[0010] S3. By utilizing the design principle of canceling out the magnetic flux in the middle column from the side column, the magnetic flux path is optimized and hysteresis loss is reduced;

[0011] S4. Apply Ohm's law for magnetic circuits to establish the equivalent magnetic circuit of LLC planar magnetic integration, calculate the key inductance value, and transform the magnetic circuit model into an equivalent circuit model through the duality theorem;

[0012] S5. Based on the established equivalent circuit model, design and optimize the operating mode of the LLC circuit to ensure high efficiency and high power density.

[0013] As a further improvement to the above technical solution:

[0014] In S1, by selecting an appropriate number of winding turns, the balance between magnetic induction intensity and power transmission efficiency is optimized.

[0015] In S2, the leakage inductance of the transformer is used as the resonant inductance.

[0016] In S2, the LLC circuit operates using zero-voltage switching of the primary-side MOSFET and zero-current switching of the secondary-side MOSFET to ensure optimal performance under different load conditions, reduce switching losses, and improve efficiency.

[0017] In S4, the equivalent circuit analysis method is used to further analyze the input-output relationship of the circuit equivalent model and optimize the design parameters.

[0018] The equivalent circuit analysis method verifies the operating mode of the LLC circuit using Kirchhoff's voltage and current laws to provide accurate input-output relationships.

[0019] Formulas for resonant inductance and magnetizing inductance obtained through equivalent circuit analysis are used to optimize circuit design.

[0020] The equivalent circuit analysis method employs the duality theorem and scaling transformation to calculate the inductance value under different operating modes, ensuring the adaptability and adjustability of the design.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] By integrating the resonant inductor and transformer of the LLC circuit onto the same EE-type magnetic core, both functional integration and effective reduction of the size of magnetic components are achieved. This design not only improves power density but also optimizes the layout of magnetic components, reducing system size and cost. In particular, the magnetic flux of the two side posts cancels each other out in the core, effectively reducing hysteresis loss and thus improving the overall efficiency of the converter. Furthermore, equivalent circuit analysis was used to conduct an in-depth analysis of the magnetic integration design, further ensuring the accuracy of the input-output relationship and optimizing the design of the resonant inductor and magnetizing inductor. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the aerospace-grade LLC planar magnetic integrated structure of the present invention.

[0025] Figure 2 This is a schematic diagram of the equivalent magnetic circuit of the LLC planar magnetic integration according to the present invention.

[0026] Figure 3 This is a schematic diagram of the equivalent circuit of the LCC planar magnetic integration of the present invention.

[0027] Figure 4 This is a schematic diagram of the LLC circuit operating mode 1 of the present invention.

[0028] Figure 5 This is a schematic diagram of the LLC circuit operating mode 2 of the present invention.

[0029] Figure 6 This is a schematic diagram of the magnetic integrated equivalent circuit under LLC operating mode 1 of the present invention.

[0030] Figure 7 This is a schematic block diagram of an aerospace LLC magnetic integrated circuit designed using the LLC planar magnetic integration method of the present invention.

[0031] Figure 8 The curve shown is the voltage transfer ratio function curve of the LLC planar magnetic integrated circuit of the present invention.

[0032] Figure 9 This is a schematic diagram of an experimental platform for an aerospace LLC magnetic integrated circuit designed using the LLC planar magnetic integration method of the present invention.

[0033] Figure 10The waveform of an aerospace LLC magnetic integrated circuit under the condition of 100V input and 12V / 120W output.

[0034] Figure 11 Efficiency test curves of aerospace LLC magnetic integrated circuits designed using the LLC planar magnetic integration method of the present invention.

[0035] Figure 12 The simulation waveform of the Saber core for aerospace LLC magnetic integrated circuits designed using the LLC planar magnetic integration method of the present invention. Detailed Implementation

[0036] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0038] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods. Example

[0039] like Figure 1 As shown, an aerospace-grade LLC planar magnetic integration design integrates the resonant inductor and transformer of an LLC circuit onto a single EE-type magnetic core, achieving a unified function of the resonant inductor and transformer. The EE-type magnetic core contains three magnetic pillars and employs an equal air gap design. n1, n2, and n3 represent the number of turns in the winding, and i1, i2, and i3 represent the current flowing through the winding. , , These represent the magnetic flux of the three magnetic columns.

[0040] Applying Ohm's law for magnetic circuits, an equivalent magnetic circuit for LLC planar magnetic integration was established and analyzed, such as... Figure 2 As shown. The magnetic flux of the two side pillars cancels out in the middle pillar, thus effectively reducing the hysteresis loss of the magnetic core. The reluctance expression for the three magnetic pillars is:

[0041]

[0042] Where R1 and R2 are the magnetic reluctances of the two side pillars of the magnetic core, and R0 is the magnetic reluctance of the middle pillar of the magnetic core. gap A is the air gap of the magnetic core, A1 is the cross-sectional area of ​​the magnetic core side post, A C Let be the cross-sectional area of ​​the cylinder in the magnetic core, and μ be the permeability of free space.

[0043] according to Figure 2 The equivalent magnetic circuit of the LLC planar magnetic integration shown, further applied to the duality theorem and after scaling transformation, yields the following: Figure 3 The magnetic integrated equivalent circuit is shown. The expressions for the three equivalent inductors are:

[0044]

[0045] Figure 4 and Figure 5 The two operating modes of the LLC circuit are shown respectively. Figure 4 Mode 1 is the operating mode in which energy is transferred from the primary side to the output side. Using Kirchhoff's voltage and current laws, the equivalent circuit of the magnetically integrated circuit in LLC operating mode 1 is analyzed, such as... Figure 6 As shown. The relationship between input and output is expressed as follows:

[0046]

[0047] Among them, v in and i in These are the input voltage and current, respectively, V o For the output voltage, n a With resonant inductor L r The expression is:

[0048] ,

[0049] Magnetizing inductance L m The expression is:

[0050]

[0051] Specific solution: An aerospace-grade half-bridge LLC magnetic integrated circuit using an LLC planar magnetic integrated design, consisting of a main power circuit and a control circuit, the principle of which is as follows: Figure 7 As shown. V o V is the output voltage. * o1 To compensate for the reference voltage of the circuit, i cs For sampling the primary current, i * cs V serves as the reference for the overcurrent protection circuit. * o2 The reference voltage for the light-load mode control circuit, and the resonant capacitor C r =C r1 +C r2 Diodes D1 and D2 are connected in parallel across the resonant capacitor, respectively. L It is an equivalent resistive load.

[0052] The main power circuit uses LLC planar magnetic integrated circuits, integrating the resonant inductor and transformer onto a single EE-type magnetic core through magnetic integration, thus simultaneously realizing the functions of both a resonant inductor and a transformer. The control circuit includes frequency conversion control, overcurrent protection, and light-load operation control mode.

[0053] LLC planar magnetic integrated circuits, in addition to possessing all the advantages of traditional LLC circuits, offer the following benefits: the topology itself can achieve cycle-by-cycle current limiting without any control intervention; it can reduce input current ripple; it can limit the voltage stress of resonant capacitors; it can improve circuit integration; and it can improve power density.

[0054] The first resonant point f of the LLC planar magnetic integrated circuit o Second resonant point f p The expressions are as follows:

[0055] ,

[0056] The voltage transfer ratio M of the LLC planar magnetic integrated circuit is expressed as follows using the fundamental frequency analysis method:

[0057]

[0058] Figure 8 The voltage transfer ratio function curve is shown. The two resonant points divide the LLC planar magnetic integrated circuit into three regions. Switching frequency f... s < f p The circuit operates capacitively in region 3 and cannot achieve ZVS; p ≤ f s < f o The circuit operates inductively in region 2, enabling ZVS for the primary-side MOSFET and ZCS for the secondary-side switch; s = f o This is called the critical mode; f o ≤ f s The circuit operates inductively in region 1, achieving only ZVS for the primary-side MOSFET. Typically, the operating region is controlled within region 2 to maximize efficiency.

[0059] The primary-side MOSFET of the LLC planar magnetic integrated circuit always operates with a duty cycle of 50%. Closed-loop control is achieved by changing the voltage transfer ratio through frequency conversion. The control process is as follows: The output voltage and reference voltage are processed by a compensator to generate an EA signal. This EA signal is then limited and sent to the VCO circuit. The VCO circuit converts the voltage signal into a frequency signal, controlling the operating frequency of the PWM control chip. Finally, the output signal of the PWM chip drives the primary-side MOSFET of the LLC circuit via an isolation driver, achieving closed-loop regulation.

[0060] The worst-case operating condition of the LLC circuit is low input voltage and full output load. Therefore, the voltage compensator is designed based on the small-signal characteristics of the worst-case operating condition. According to the worst-case operating condition, the transfer function Gvc(s) of the LLC resonant converter has the characteristics of two poles and one zero. Therefore, a voltage compensator with two poles and two zeros is selected.

[0061] Figure 9 This is an experimental platform for aerospace-grade LLC magnetic integrated circuits designed using planar LLC magnetic integration. The input uses aerospace-grade 100V bus voltage, and the rated output is 12V / 10A. All circuit components meet aerospace-grade standards. The planar integrated magnetic core selected is EE26, A. e =159 mm 2 The specific circuit parameters are shown in Table 1. Figure 10 The efficiency test curve of the LLC magnetic integrated circuit under the conditions of 100V input voltage and 10A output current is shown. It can be seen that the switching frequency f of the circuit... s =136 kHz, operating in region 2, achieving maximum efficiency.

[0062] Table 1 Parameters of LLC Magnetic Integrated Circuit Experimental Platform

[0063] Figure 11 The circuit efficiency test curve shows that under the same load conditions, the higher the input voltage, the higher the efficiency. The efficiency under rated conditions can reach 91.04%, and the circuit achieves the highest efficiency of 91.96% when operating at the resonant point, thus realizing high power density.

[0064] Simulate the magnetic components using Saber software. The simulation input is 100V, the output is 12V / 10A, and the B-value curves of the three magnetic pillars in the core are shown below. Figure 12 As shown, the ΔB values ​​for the side columns are 0.2165 T and 0.161 T, respectively, while the ΔB value for the middle column is 0.082 T. The magnetic fluxes of the two side columns cancel each other out in the middle column, effectively reducing the hysteresis loss of the magnetic core.

Claims

1. A planar magnetic integration method for aerospace LLC applications, characterized in that, Includes the following steps: S1. Select an EE type magnetic core and design three magnetic pillars, with equal air gaps between the middle pillar and the side pillars to ensure uniform magnetic flux distribution; S2. Integrate the resonant inductor and transformer of the LLC circuit onto the same EE-type magnetic core, so that the functions of both can be achieved through the same magnetic core; S3. By utilizing the design principle of canceling out the magnetic flux in the middle column from the side column, the magnetic flux path is optimized and hysteresis loss is reduced; S4. Apply Ohm's law for magnetic circuits to establish the equivalent magnetic circuit of LLC planar magnetic integration, calculate the key inductance value, and transform the magnetic circuit model into an equivalent circuit model through the duality theorem; S5. Based on the established equivalent circuit model, design and optimize the operating mode of the LLC circuit to ensure high efficiency and high power density.

2. The aerospace LLC planar magnetic integration method according to claim 1, characterized in that, In S1, by selecting an appropriate number of winding turns, the balance between magnetic induction intensity and power transmission efficiency is optimized.

3. The aerospace LLC planar magnetic integration method according to claim 2, characterized in that, In S2, the leakage inductance of the transformer is used as the resonant inductance.

4. The aerospace LLC planar magnetic integration method according to claim 3, characterized in that, In S2, the LLC circuit operates using zero-voltage switching of the primary-side MOSFET and zero-current switching of the secondary-side MOSFET to ensure optimal performance under different load conditions, reduce switching losses, and improve efficiency.

5. The aerospace LLC planar magnetic integration method according to any one of claims 1-4, characterized in that, In S4, the equivalent circuit analysis method is used to further analyze the input-output relationship of the circuit equivalent model and optimize the design parameters.

6. The aerospace LLC planar magnetic integration method according to claim 5, characterized in that, The equivalent circuit analysis method verifies the operating mode of the LLC circuit using Kirchhoff's voltage and current laws to provide accurate input-output relationships.

7. The aerospace LLC planar magnetic integration method according to claim 6, characterized in that, Formulas for resonant inductance and magnetizing inductance obtained through equivalent circuit analysis are used to optimize circuit design.

8. The aerospace LLC planar magnetic integration method according to claim 7, characterized in that, The equivalent circuit analysis method employs the duality theorem and scaling transformation to calculate the inductance value under different operating modes, ensuring the adaptability and adjustability of the design.

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