A circuit topology and frequency-variable inductor selection design method considering frequency-variable parameter influence for wide-band multi-order EMI filter

Abstract

The present application belongs to the technical field of electromagnetic compatibility design, and discloses a circuit topology and frequency-variable inductor selection design method for wide-band multi-order EMI filters considering the influence of frequency-variable parameters. The present application simultaneously considers the problem of EMI filter high-frequency insertion loss deformation failure caused by the frequency variation of actual source impedance, load impedance and filter branch impedance, and provides a method capable of quickly and concisely generating the insertion loss of various EMI filter topology structures, thereby accurately and quickly calculating the target inductance frequency spectrum at the frequency point exceeding the standard under different filter topologies; then, the required maximum design coefficient is calculated according to the high and wide frequency attenuation rate of the frequency-variable inductor relative permeability spectrum, the space structure and the number of turns of the filter inductor are designed, and the optimal filter topology is evaluated by comparing the maximum design coefficients under the same order and different topologies, thereby improving the accuracy of the topology selection and inductor design of the EMI filter, and finally reducing the development cost of the EMI filter.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetic compatibility design, and more particularly relates to a circuit topology and frequency-variable inductor selection design method considering the influence of frequency-variable parameters for a wide-band multi-order EMI filter. BACKGROUND

[0002] In recent years, various power electronic conversion power supplies have been widely used in power systems, consumer electronics and other fields. With the development of high integration and high frequency of power supply equipment, electromagnetic interference (EMI) has become an important problem that needs to be solved in power electronic conversion power supplies. Whether it is the EMI standard for military power supplies or the EMI standard for civilian power supplies, power supply manufacturers are required to effectively suppress electromagnetic interference in the wide frequency range of 10 kHz to 30 MHz. Therefore, there is an urgent need for EMI filters that can effectively attenuate in a wider frequency range.

[0003] Frequency-variable source impedance and load impedance will affect the accurate calculation of the insertion loss of the EMI filter and the accurate selection of the filter topology. Traditional EMI filter design methods are usually based on ideal circuit conditions for evaluation, that is, the input impedance and output impedance of the filter are assumed to be 50 ohms. However, this working condition is significantly different from the actual working environment. In actual working conditions, the source impedance of the suppression object and the load impedance of the test tool often deviate from the theoretical value of 50 ohms, resulting in that the traditional design method cannot accurately reflect the actual performance when evaluating the insertion loss of the filter. In addition, the source impedance and the load impedance may present different amplitude size relationships at different frequencies, which will cause the traditional filter topology selection method based on impedance mismatch to be no longer applicable to the case where the amplitudes vary greatly with frequency.

[0004] Frequency-variable capacitor and inductor branch impedance will affect the generation of high-frequency insertion loss of the EMI filter and the selection design of frequency-variable devices. In order to construct an EMI filter with high insertion loss, a ferrous nanocrystalline magnetic material with an initial magnetic permeability much higher than that of other magnetic materials is usually selected as the inductor material. However, this material has a problem of a significant decay of relative magnetic permeability in the high frequency band. The relative magnetic permeability of such a magnetic material decays from 100,000 at 1 kHz to 1,000 at 10 MHz, and the 100 kHz-1 MHz frequency band where the magnetic permeability drops the fastest is exactly the frequency band with the highest EMI amplitude of general power supply equipment. Therefore, the inductor constructed by nanocrystalline needs to be considered as a frequency-variable inductor. In addition, the parasitic inductance of the capacitor device inside the filter will significantly affect its bypass performance, making it difficult for such a frequency-variable EMI filter to suppress the electromagnetic interference generated by the power supply equipment to within the limit value in the high frequency band. This is also the main reason for the deformation of the insertion loss curve of the frequency-variable EMI filter in the high frequency band.

[0005] The above influencing factors make the filter inductance designed by the traditional method prone to over-design or under-design, thereby greatly increasing the subsequent EMI rectification cost and period. SUMMARY

[0006] In view of the above defects or improvement needs of the prior art, the purpose of the present application is to provide a circuit topology and frequency-variable inductor selection and design method considering the influence of frequency-variable parameters for a wide-band multi-order EMI filter, aiming to solve the problems of large insertion loss evaluation deviation, difficult filter topology determination and poor high-frequency performance of filter devices in the traditional EMI filter design method.

[0007] To achieve the above purpose, the present application provides a circuit topology and frequency-variable inductor selection and design method considering the influence of frequency-variable parameters for a wide-band multi-order EMI filter, wherein the circuit topology of the EMI filter is divided into two types A and B according to the positional relationship of capacitance and inductance, comprising the following steps:

[0008] According to the order of the EMI filter to be designed, a corresponding insertion loss calculation model is selected;

[0009] The difference spectrum is obtained by subtracting the standard limit spectrum from the measured interference spectrum under a preset margin, the insertion loss values of the frequency points greater than zero in the difference spectrum are retained, and the insertion loss values of the frequency points less than or equal to zero are empty, forming a target insertion loss spectrum;

[0010] Starting from the first frequency point of the target insertion loss spectrum, the inductance inductance is stepped, starting from the upper limit of the inductance inductance search downward, and based on the insertion loss calculation model, the minimum inductance inductance required by each exceeding frequency point is found out, forming a minimum inductance spectrum;

[0011] The minimum inductance spectrum of the two topological type EMI filters is divided by the relative permeability spectrum of the magnetic material used by the designed inductance under the preset attenuation margin to obtain an inductance design coefficient spectrum, the maximum design coefficients under the two topological types are selected from the inductance design coefficient spectrum, and the smaller value is compared from the two maximum design coefficients as the target design coefficient, and the topological type corresponding to the target design coefficient is the target topology, and then the structure size selection and winding turn number design of the designed inductance are performed according to the target design coefficient.

[0012] The present application also provides an electronic device, comprising: a computer readable storage medium and a processor;

[0013] The computer readable storage medium is used to store executable instructions;

[0014] The processor is used to read the executable instructions stored in the computer readable storage medium, and execute the above method.

[0015] The application further provides a computer readable storage medium storing computer instructions for causing a processor to execute the above method.

[0016] The application further provides a computer program product comprising computer programs or instructions which, when executed by a processor, implement the above method.

[0017] Compared with the prior art, the above technical scheme conceived by the application can achieve the following beneficial effects:

[0018] 1. The method for generating an insertion loss calculation mathematical model of various multi-order EMI filters considering frequency-variable parameters is fast and accurate. The insertion loss calculation mathematical model generation method provided by the application can simultaneously consider the influence of source impedance, load impedance, filter capacitor impedance and filter inductor impedance under a single frequency point on the real insertion loss, improve the calculation accuracy of the insertion loss, and combine the variation law of the insertion loss of filters of different orders constructed under different filter topologies to quickly and simply generate the insertion loss mathematical model of the mainstream multi-order EMI filter topology structure, which is universal.

[0019] 2. The frequency-variable inductor is more finely selected and designed to meet the wideband insertion loss requirement. The frequency-variable inductor selection method provided by the application focuses on the problem of insertion loss failure of EMI filters constructed by iron-based nanocrystalline and other magnetic materials with high initial magnetic permeability and high wideband attenuation rate at high frequencies. The method first finds the minimum inductance required at each out-of-specification frequency point through a large-to-small, multi-round iteration method to form a target inductance frequency spectrum. Compared with the traditional method of finding a tangent sensitive frequency point based on an insertion loss slope, the method is more comprehensive and more practical. Further, by dividing the target inductance frequency spectrum by the relative permeability spectrum of the magnetic material at the corresponding frequency point, a design coefficient that does not change with frequency can be obtained. Taking the maximum value of the coefficient in the frequency spectrum as a design reference for the filter inductor can avoid the influence of the attenuation of the frequency-variable inductor at high frequencies on the insertion loss of the EMI filter, thereby improving the accuracy of the selection and design of the filter inductor in the EMI filter and reducing the development cost of the EMI filter.

[0020] 3. A more comprehensive comparison and evaluation of the optimal EMI filter topology at the same order. The optimal filter topology evaluation method provided by this invention breaks away from the traditional filter topology evaluation process based on impedance mismatch, which compares the amplitude of source impedance and load impedance at a single frequency point. By calculating the maximum design coefficient of the two types of filter topologies at the same order, the filter topology corresponding to the smaller one is selected as the optimal topology. This method comprehensively considers the magnitude relationship between source impedance and load impedance over a wide frequency band, as well as the insertion loss effect brought by various filtering devices. It provides a more comprehensive comparison of the difference in the required inductance of the two types of filter topologies at the same order, further improving the accuracy of EMI filter topology selection. Attached Figure Description

[0021] Figure 1 This is a flowchart of a circuit topology and frequency-varying inductor selection design method for a wideband multi-stage EMI filter that considers the influence of frequency-varying parameters, provided by the present invention.

[0022] Figure 2 This is the flowchart of the over-frequency traversal algorithm A1;

[0023] Figure 3 This is the flowchart of the minimum total sensitivity multi-round search algorithm A2;

[0024] Figure 4 This is the target insertion loss spectrum.

[0025] Figure 5 It is the search result for the minimum total inductance of 2nd to 4th order filters;

[0026] Figure 6 It is the relative permeability spectrum of the selected nanocrystalline magnetic core material;

[0027] Figure 7 These are the calculated results of the design coefficient spectra of 2nd to 4th order filters;

[0028] Figure 8 This is a comparison chart of the simulated insertion loss results under the optimal topology and the target insertion loss. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] The application provides a circuit topology and frequency-variable inductor selection design method considering frequency-variable parameter influence for a wide-band multi-order EMI filter. Figure 1 The method comprises the following steps:

[0031] According to the order of the EMI filter to be designed, a corresponding insertion loss calculation model is selected;

[0032] The measured interference spectrum is subtracted from the standard limit spectrum under a preset margin to obtain a difference spectrum, the insertion loss values of the frequency points greater than zero in the difference spectrum are reserved, and the insertion loss values of the frequency points less than or equal to zero are emptied to form a target insertion loss spectrum;

[0033] Starting from the first frequency point of the target insertion loss spectrum, the inductance inductance is stepped, and the inductance inductance is searched downward from the upper limit of the inductance inductance, and the minimum inductance inductance required by each exceeding frequency point is found out based on the insertion loss calculation model to form a minimum inductance spectrum;

[0034] The minimum inductance spectrum of the two topological type EMI filters is divided by the relative permeability spectrum of the magnetic material used by the inductor under a preset attenuation margin to obtain an inductor design coefficient spectrum, the maximum design coefficients under the two topological types are screened out, and the smaller value is compared from the two maximum design coefficients as a target design coefficient, and the topological type corresponding to the target design coefficient is a target topology, and the structure size selection and winding turn number design of the inductor to be designed are performed according to the target design coefficient.

[0035] Embodiment 1

[0036] The application needs to input the order of the EMI filter to be designed. Considering that general EMI filters need to rely on the joint action of inductor branches and capacitor branches to achieve effective filtering, the application discusses the EMI filters of two orders and above, and in order to improve the insertion loss performance of the filter at high frequencies as much as possible, the application discusses the EMI filters with all inductor branches and capacitor branches being the same. In order to facilitate the performance comparison of different filter topologies under the same order and filter branch parameters, the application classifies the current mainstream filter topologies into A-type filter topologies and B-type filter topologies, and the specific filter topology structures are shown in Table 1.

[0037]

[0038] When the input order is even E, the A-type filter circuit at this time can be equivalent to the filter form of n = E / 2 LC circuit cascaded. By analyzing and summarizing the characteristics of the circuit topology and the iterative calculation rule of the insertion loss, for an n-stage LC filter circuit, the insertion loss calculation mathematical model at a single frequency point can be expressed as:

[0039]

[0040] wherein Z S (f0) and Z L (f0) are the complex forms of the measured source impedance of the power supply device and the load impedance of the test tool at the frequency f0, K Ai (f0) and Z ALn (f0) are parameters that need to be calculated by iteration, and n is the number of stages of the filter, which is expressed as:

[0041]

[0042] wherein P L (f0) and P C (f0) are the complex impedances of each inductance branch and each capacitance branch in an n-stage LC filter circuit at the frequency f0, assuming that the total inductance L n and the total capacitance C n provided by the filter are known, and the high-frequency equivalent resistance ESR C and the high-frequency equivalent inductance ESL C of each capacitance branch are estimated, then the number of filter inductances m L and the number of filter capacitances m C in the filter circuit can be easily calculated according to the filter topology, and can be expressed as:

[0043]

[0044] When the input order is even E, the A-type filter circuit at this time can be equivalent to the filter form of n = E / 2 LC circuit cascaded. By analyzing and summarizing the characteristics of the circuit topology and the iterative calculation rule of the insertion loss, for an n-stage LC filter circuit, the insertion loss calculation mathematical model at a single frequency point can be expressed as:

[0045]

[0046] It can be seen that formula (4) is basically the same as formula (1), but K Bi (f0) and Z BLn (f0) need to be redefined as:

[0047]

[0048] When the input order is odd O, the A-type filter circuit at this time can be equivalent to a n=(O-1) / 2 order π-type filter, which can be regarded as an LC-type circuit with n stages in parallel with a capacitor branch near the source impedance in analysis. Therefore, the insertion loss iterative calculation rule can be further analyzed on the basis of formula (1), and the insertion loss calculation mathematical model of the n-stage π-type filter circuit at a single frequency point f0 can be expressed as:

[0049]

[0050] Under the condition that the parameters of the newly added capacitor branch are unchanged, K Ah (f0) and Z Ah (f0) are intermediate expressions added additionally, and the number of filter inductors and filter capacitors in the filter circuit needs to be redefined, which is expressed as:

[0051]

[0052] When the input order is odd O, the B-type filter circuit at this time can be equivalent to a n=(O-1) / 2 order T-type filter, which can be regarded as an CL-type circuit with n stages in series with an inductor branch near the source impedance in analysis. Therefore, the insertion loss iterative calculation rule can be further analyzed on the basis of formula (4), and the insertion loss calculation mathematical model of the n-stage T-type filter circuit at a single frequency point f0 can be expressed as:

[0053]

[0054] Under the condition that the parameters of the newly added capacitor branch are unchanged, Z Bh (f0) is an intermediate expression added additionally, and the number of filter inductors and filter capacitors in the filter circuit needs to be redefined, which is expressed as:

[0055]

[0056] The present application needs to input the measured interference spectrum Mag EMI (f) and the standard limit spectrum Lim EMI (f). In order to improve the reliability of the EMI filter design, the difference diff(f) between the two spectra can be calculated under the consideration of a 6dB design margin, as shown in formula (10). Since the actual interference spectrum Mag EMI(f) Not all frequency points will exceed the standard, in order to simplify the design process, the difference value greater than zero of the frequency point is reserved in the difference spectrum, and the difference value less than or equal to zero is considered to be a standard point, and the insertion loss value is set to zero, as shown in formula (11). The frequency point, the measured interference spectrum and the standard limit spectrum are plotted in the same two-dimensional spectrum diagram to output as the filter design target reference.

[0057]

[0058]

[0059] In order to calculate the insertion loss on each corresponding exceeding frequency point, the present application provides an exceeding frequency point traversal algorithm A1, which can skip the standard frequency point, read only the estimated capacitance branch and its high frequency parameters, and the source impedance of the measured power supply equipment and the load impedance of the test tool on the exceeding frequency point, and input to the minimum total inductance multi-round search algorithm A2 for insertion loss calculation and minimum total inductance search under two types of filter topologies. Finally, the two calculation and search results are plotted in the same two-dimensional spectrum diagram to output, so as to compare the difference of the minimum total inductance of the two types of filter topologies.

[0060] Benefiting from the fact that formulas (1), (4), (6) and (8) form a monotonically increasing function with inductance after the turning frequency under the condition that other parameters are unchanged, in order to find the minimum total inductance required on each exceeding frequency point, the present application provides a multi-round minimum total inductance search algorithm A2 which is traversed from large to small.

[0061] The program block diagram of algorithm A1 and algorithm A2 is shown in Figure 2 and Figure 3 When the inductance value cannot be found in the search range (the upper limit of the search is reached) or the inductance value is too large on some frequency points, it should be considered to increase the filter order or replace the filter topology.

[0062] The present application needs to provide the relative permeability spectrum μ r (f) of the magnetic material used for the inductance to be designed, and divide it by the target minimum inductance spectrum of the two types of filter topologies obtained by algorithm A1 to obtain the inductance design coefficient spectrum Ks(f). In addition, considering that the relative permeability of the actually manufactured filter inductance also has a decay problem caused by the manufacturing process compared with the relative permeability referred to during inductance design, it is necessary to input the permeability decay margin K M according to the production experience of the magnetic material manufacturer, as shown in formula (12). Finally, the two calculation results are plotted in the same two-dimensional spectrum diagram to output, so as to compare the difference of the required design coefficients of the two types of filter topologies.

[0063]

[0064] Two maximum design coefficients Ks that should be met under two filter topologies are respectively screened out from the design coefficient spectrum calculated in the foregoing end The smaller one is compared from the two maximum design coefficients, and is taken as a target design coefficient to guide the spatial structure and turn number design of the frequency-variable inductance, as shown in equation (13). In addition, the filter topology structure corresponding to the smaller one is the target topology of the EMI filter.

[0065]

[0066] It should be noted that the design coefficient Ks is a coefficient defined in the present application. Since the design coefficient is obtained by dividing the frequency-variable inductance of the frequency-variable inductance by the frequency-variable relative magnetic permeability, its physical meaning is the product of all parameters in the filter inductance that do not change with frequency but affect the inductance. It is only related to the spatial size and winding turn number of the filter inductance, so this coefficient can be used as a design basis for the filter inductance. Assuming that the effective core cross-sectional area Ae and the average magnetic path length Le of the magnetic ring can be known when the magnetic ring is selected, the required winding turn number N of the EMI filter can be calculated by equation (14), where μ0 is the absolute magnetic permeability, m L is the total number of filter inductances required in the multi-stage EMI filter.

[0067]

[0068] Suppose that the high-frequency interference of a power supply device needs to meet the requirements of GJB151B-2013: CE102, and the interference spectrum and standard limit value are input into the algorithm program of the present application, the target insertion loss is shown by the blue line as Figure 4 .

[0069] According to the above insertion loss spectrum, the minimum total inductance at each exceeding frequency point can be calculated. In order to show the design effect of the present application, 2, 3 and 4 order EMI filters are selected for design respectively. Considering the leakage current requirement, the total capacitance value of the EMI filter is 800 nF. Since the capacitor is installed on the PCB, the high-frequency stray parameters can be controlled to be very small. Therefore, the high-frequency parameters are set as: ESL C = 50 nH, ESR C = 0.1 Ω; when searching for the minimum total inductance, the search range is set as: (1~10000) uH, and the search accuracy is 0.1 uH. The minimum total inductance search result is shown in Figure 5 , (a), (b) and (c) are the minimum total inductance search results of the 2, 3 and 4 order filters respectively.

[0070] According to the above minimum total inductance spectrum, the design coefficient is calculated in combination with the relative permeability spectrum of the selected nanocrystalline magnetic core material. Considering that the relative permeability of the actual produced magnetic ring may deviate from the reference relative permeability spectrum, the permeability attenuation margin is set to 0.7. The relative permeability spectrum of the selected nanocrystalline magnetic core material is shown in Figure 6 The calculation result of the design coefficient spectrum is shown in Figure 7 (a), (b) and (c) are the design coefficient spectra of 2nd, 3rd and 4th order filters, respectively. The maximum design coefficient in the design coefficient spectrum can be extracted, and the results are summarized in Table 2.

[0071]

[0072] According to the actual application scenario, a 2nd order EMI filter needs to be selected. Therefore, the topology of the EMI filter should be selected as a B-type, i.e. a CL-type filter, and the target inductance design coefficient is 5.2e-8. According to the product manual of the magnetic ring manufacturer, a magnetic ring with an effective magnetic core cross-sectional area Ae of 3e-4m 2 and an average magnetic circuit length Le of 0.3451m can be selected. To meet the design coefficient requirement, the number of turns N can be calculated as 7 turns. The design parameters of the nanocrystalline magnetic ring to be constructed are input into the insertion loss calculation mathematical model, and the simulated insertion loss result under the optimal topology can be obtained. The comparison diagram of the simulated insertion loss result and the target insertion loss is shown in Figure 8 .

[0073] Embodiment 2

[0074] The application also relates to an electronic device comprising a memory and a processor, the memory storing a computer program, and the processor implementing the steps of the above method when executing the computer program.

[0075] The electronic device can be a desktop computer, a notebook computer, a palm computer, a cloud server and the like. The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, and the like. The memory can be used to store computer programs and / or modules, and the processor can execute or implement the computer programs and / or modules stored in the memory, and call data stored in the memory, so as to realize various functions of the electronic device.

[0076] Embodiment 3

[0077] The application also relates to a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps of the above method.

[0078] Specifically, the memory can include a high-speed random access memory, and can also include a non-volatile memory, for example, a hard disk, a memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, at least one disk storage device, a flash memory device, or other volatile solid-state memory devices.

[0079] Embodiment 4

[0080] The embodiment of the application provides a computer program product or a computer program, which comprises computer instructions stored in a computer readable storage medium. A processor of a computer device reads the computer instructions from the computer readable storage medium, and the processor executes the computer instructions, so that the computer device executes the steps of the method of the above embodiment of the application.

[0081] The technical features of the above embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, it should be considered that they are within the scope of the present application. It should be noted that the "in an embodiment of the present application", "for example", "for example" and the like in the present application are intended to illustrate the present application, and are not used to limit the present application.

[0082] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A design method of circuit topology and frequency-dependent inductor selection considering the impact of frequency-dependent parameters for wide-band multi-order EMI filters, wherein the circuit topology of the EMI filter is divided into two categories A and B according to the positional relationship of capacitors and inductors, characterized in that, The method comprises the following steps: According to the order of the EMI filter to be designed, a corresponding insertion loss calculation model is selected; The measured interference spectrum is subtracted from the standard limit spectrum under a preset margin to obtain a difference spectrum, the insertion loss values of the frequency points greater than zero in the difference spectrum are retained, and the insertion loss values of the frequency points less than or equal to zero are emptied to form a target insertion loss frequency spectrum; Starting from the first frequency point of the target insertion loss frequency spectrum, the inductance inductance is set to step down, and the inductance inductance is searched from the upper limit of the inductance inductance to find the minimum inductance inductance required by each exceeding frequency point based on the insertion loss calculation model to form a minimum inductance spectrum; The minimum inductance spectrum of the two topological type EMI filters is divided by the relative permeability frequency spectrum of the magnetic material used by the designed inductor under a preset attenuation margin to obtain an inductor design coefficient spectrum, the maximum design coefficients under the two topological types are screened from the inductor design coefficient spectrum, the smaller value is compared from the two maximum design coefficients, and the smaller value is taken as the target design coefficient. The topological type corresponding to the target design coefficient is the target topology, and the structure size selection and the number of turns of the designed inductor are designed according to the target design coefficient.

2. The design method of claim 1, wherein, The insertion loss calculation model is: When the order is even E, the insertion loss of the A-type EMI filter at a single frequency point f0 is: wherein Z S (f0) and Z L (f0) are the complex forms of the source impedance of the power supply device and the load impedance of the test fixture, respectively, measured at a frequency f0, K Ai (f0) and Z ALn (f0) are parameters that require iterative calculations in a loop, and n is the number of stages of the filter, which is expressed as: where P L (f0) and P C (f0) are the complex impedances of each inductive branch and capacitive branch, respectively, of the A-class EMI filter circuit at frequency f0, and are given by: where Ltot n is the total inductance in the filter circuit, Ctot n is the total capacitance in the filter circuit, ESR C is the estimated high-frequency equivalent resistance of each capacitance branch, ESL C is the estimated high-frequency equivalent inductance of each capacitance branch, m L is the number of filter inductances in the filter circuit, m C is the number of filter capacitances in the filter circuit; When the order is even E, the insertion loss of the B-type EMI filter at a single frequency point f0 is: K Bi (f0) and Z BLn (f0) are parameters that require iterative loop calculations and are expressed as: where P L (f0), P C (f0), m L and m C are defined as in the A-class EMI filter circuit with an even order. When the order is odd O, the insertion loss of the A-type EMI filter at a single frequency point f0 is: where K Ai (f0), Z ALn (f0), P L (f0) and P C The expression of (f0) is consistent with the expression result when the order is even, K Ah (f0) and Z Ah (f0) are additional intermediate expressions, the number of filter inductors and filter capacitors in the filter circuit needs to be redefined, which is represented as: When the order is odd O, the insertion loss of the B-type EMI filter at a single frequency point f0 is: where K Ai (f0), Z ALn (f0), P L (f0) and P C The expression of (f0) is consistent with the expression result when the order is even, Z Bh (f0) is an additional intermediate expression, the number of filter inductors and filter capacitors in the filter circuit needs to be redefined, which is represented as: 。 3. The design method of claim 1, wherein, The target insertion loss frequency spectrum is expressed as: where diff(f) = Mag EMI (f) + 6 - Lim EMI (f) is the difference spectrum, Mag EMI (f) is the interference spectrum, Lim EMI (f) is the standard limit spectrum.

4. The design method of claim 1, wherein, The minimum inductance spectrum is formed by starting from the first frequency point of the target insertion loss frequency spectrum, setting the inductance inductance to step down, searching the inductance inductance from the upper limit of the inductance inductance, and finding the minimum inductance inductance required by each frequency point based on the insertion loss calculation model. By traversing the frequency points, the frequency points with non-empty insertion loss values are recorded as exceeding frequency points, the source impedance of the measured power supply equipment and the load impedance of the test tool are read at each exceeding frequency point, and the impedance of a single capacitor branch is calculated according to the estimated total capacitance and high-frequency parameters. According to the frequency value of the current exceeding frequency point, the target insertion loss at the current frequency, the source impedance at the current frequency, the load impedance at the current frequency, the estimated capacitor branch impedance, and the preset inductance search upper limit, search round and search step, the minimum total inductance of the A and B type topologies under the same order is calculated, and then the minimum total inductance at the current exceeding frequency point is stored in the corresponding target inductance spectrum. After traversing and analyzing the last frequency point, the two target inductance spectra are plotted in the same two-dimensional graph to form a minimum inductance spectrum.

5. The design method of claim 4, wherein, The minimum total inductance of the A and B type topologies under the same order is calculated simultaneously, and comprises: The inductance search lower limit is brought into the inductance search upper limit based on the insertion loss calculation model to perform insertion loss calculation on a single frequency point and compare with the target insertion loss. If the calculated insertion loss is greater than the target insertion loss, the current inductance inductance is reduced by the current step value, and the next calculation and comparison are performed. If the calculated insertion loss is less than the target insertion loss, the current minimum inductance inductance is taken as the new inductance search lower limit, the current minimum inductance inductance is added to the search step as the new inductance search upper limit, the current step is reduced by 10 times as the new search step, and a new round of minimum total inductance search is performed until the minimum total inductance search under the minimum search precision is completed. The upper limit of the final search range is taken as the minimum target total inductance.

6. The design method of claim 1, wherein, The inductance design coefficient spectrum is expressed as: where L A (f) is the target inductance spectrum for the same order A-type filter topology, L B (f) is the target inductance spectrum for the same order B-type filter topology, K M is the permeability attenuation margin, μ r (f) is the relative permeability spectrum.

7. The design method of claim 1, wherein, The relationship between the target design coefficient and the inductance design parameter is expressed as wherein Ae is the effective core cross-sectional area of the magnetic ring, Le is the average magnetic path length, N is the number of windings required for the EMI filter, μ0 is the absolute permeability, m L is the total number of filter inductors required in the multi-stage EMI filter. 8.An electronic device comprising a memory and a processor, the memory storing a computer program, wherein, The processor implements the steps of the method of any one of claims 1 to 7 when executing the computer program.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method of any one of claims 1 to 7.

10. A computer program product comprising computer programs or instructions, characterized in that, The computer program or instructions are executed by the processor to implement the steps of the method of any one of claims 1 to 7.

Images