A method for establishing an equivalent simulation model of a magnetic bead filter circuit under a DC bias environment

Abstract

The present invention discloses a method for establishing an equivalent simulation model of a magnetic bead filter circuit under a DC bias environment, and belongs to the field of simulation modeling. First, the impedance characteristic curve and the DC bias curve image are processed; if there is no DC bias in the actual application scenario of the magnetic bead filter circuit, go directly to the next step; if there is, adjust the impedance characteristic curve; then the impedance characteristic curve is linearized in sections; then sample and count reference points; calculate the average value of equivalent parameters; and finally establish an equivalent simulation model of the magnetic bead filter circuit. The present invention solves the problem that the accuracy of the equivalent model of the magnetic bead filter circuit is reduced due to impedance changes under the action of DC bias; at the same time, the equivalent model establishment method can be widely used in circuit simulation software such as Pspice, providing strong support for the design of magnetic bead filter circuits, component selection, performance prediction and other work, and has good practicality in the field of magnetic bead filter circuit simulation.

Description

Technical Field

[0001] The present invention relates to the technical field of simulation modeling, and in particular to a method for establishing an equivalent simulation model of a magnetic bead filter circuit under a direct current bias environment. Background Art

[0002] With the continuous development of electronic communication technology, the signal sampling frequency continues to increase, and the high-frequency noise in the circuit is more and more likely to cause resonance and harmonic current amplification. In the filter circuit, magnetic beads can be used to suppress high-frequency noise and spike interference on signal lines and power lines, and also have the function of absorbing static pulses. Usually, magnetic bead filter circuits are required in the power input part of RF (Radio Frequency) radio frequency circuits, PLL phase-locked loop circuits (Phase Locked Loop), and oscillation circuits.

[0003] Usually, magnetic beads are made of alloy materials with high magnetic permeability, which exhibit different impedance characteristics in different frequency ranges. In the low-frequency band, the impedance characteristics of magnetic beads are mainly manifested as inductance characteristics, while in the higher frequency band, the inductance characteristics are weakened due to the decrease in the magnetic permeability of the magnetic bead alloy material, and its impedance characteristics are manifested as complex impedance characteristics. Since magnetic beads exhibit different impedance characteristics in different frequency ranges, it is more difficult to establish an equivalent model for filtering circuit simulation. Although the paper "PCIe Electromagnetic Interference Analysis and Optimization Design Based on Field-Circuit Simulation" in the journal "High Power Laser and Ion Beam" in April 2020 mentioned the idea of ​​equivalent magnetic beads to RLC circuits, the paper did not give a method for obtaining the specific parameters of the magnetic bead equivalent model, nor did it consider the influence of DC bias on the simulation accuracy of the magnetic bead equivalent model.

[0004] Since the impedance characteristics of magnetic beads will change under the action of DC bias, the actual magnetic bead filter circuits are all used on power lines with DC bias, and the impedance curves in the magnetic bead product datasheet are all measured under the condition of no bias current. How to improve the accuracy of the simulation equivalent model of the magnetic bead filter circuit under the action of DC bias has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a method for establishing an equivalent simulation model of a magnetic bead filter circuit under a DC bias environment, so as to solve the problem that the accuracy of the equivalent model is reduced due to impedance changes of the magnetic bead filter circuit under the action of DC bias.

[0006] In order to solve the above technical problems, the present invention provides a method for establishing an equivalent simulation model of a magnetic bead filter circuit under a DC bias environment, comprising:

[0007] Step 1: Process the impedance characteristic curve and DC bias curve images;

[0008] Step 2: If there is no DC bias in the actual application scenario of the magnetic bead filter circuit, go directly to step 3; if there is, adjust the impedance characteristic curve;

[0009] Step 3: Piecewise linearization of the impedance characteristic curve;

[0010] Step 4: Sampling and statistical reference points;

[0011] Step 5: Calculate the average value of equivalent parameters;

[0012] Step 6: Establish an equivalent simulation model of the magnetic bead filter circuit.

[0013] Optionally, the impedance characteristic curve and the DC bias curve are obtained by consulting a magnetic bead product manual, and image processing software is used to clarify and unify the size of the obtained impedance characteristic curve and DC bias curve images.

[0014] Optionally, the image resolution of the impedance characteristic curve and the DC bias curve is greater than 600ppi and remains consistent, and the image aspect ratio of the impedance characteristic curve and the DC bias curve is fixed and remains consistent.

[0015] Optionally, adjusting the impedance characteristic curve in step 2 includes: extracting a Z curve, an XL curve and an R curve from the impedance characteristic curve of the magnetic bead, moving the three extracted curves to the image of the DC bias curve, and ensuring that the Z curve corresponding to the DC bias value is consistent with the starting point of the extracted curve; the low-frequency band of the newly constructed Z curve is composed of an impedance curve with no bias current, and the high-frequency band is composed of an impedance curve with a DC bias.

[0016] Optionally, the step three is: dividing the part of the impedance characteristic curve obtained in the step two related to the extraction of equivalent parameters into an inductive segment and a complex impedance segment; wherein the inductive segment is defined as a frequency band included in the frequency value from the frequency of 1 MHz to the frequency value at the position where the deviation of the tangent slope of the Z curve and the XL curve is equal to 5%; and the complex impedance segment is defined as a frequency band included in the frequency value at the position where the deviation of the tangent slope of the Z curve and the XL curve is equal to 5% to the frequency value at the intersection of the R curve and the XL curve.

[0017] Optionally, the step four is: using a random sampling statistical algorithm to extract n frequency points from the inductive segment and the complex impedance segment obtained in step three, respectively, where n≥10.

[0018] Optionally, the random sampling statistical algorithm includes a simple random sampling algorithm, an equidistant random sampling algorithm, and a Monte Carlo random sampling algorithm.

[0019] Optionally, the step five is: calculating the equivalent inductance value l corresponding to each frequency point according to the sampled frequency points. iAnd the equivalent capacitance value C i , and then calculate the average equivalent inductance l and the average equivalent capacitance C par .

[0020] Optionally, the step six is: the magnetic bead filter circuit equivalent model consists of two parts: a magnetic bead equivalent module and a filter capacitor; the magnetic bead equivalent module consists of a DC equivalent resistor R DC and the average equivalent inductance l in series, and then connected to the AC equivalent resistance R AC and the average equivalent capacitance C par The filter capacitors are connected in parallel and selected according to the actual design requirements.

[0021] In the method for establishing an equivalent simulation model of a magnetic bead filter circuit under a DC bias environment provided by the present invention, firstly, the impedance characteristic curve and the DC bias curve image are processed; if there is no DC bias in the actual application scenario of the magnetic bead filter circuit, go directly to the next step; if there is, adjust the impedance characteristic curve; then the impedance characteristic curve is segmented linearized; then sample and count reference points; calculate the average value of equivalent parameters; and finally establish an equivalent simulation model of a magnetic bead filter circuit. The present invention solves the problem that the accuracy of the equivalent model of the magnetic bead filter circuit is reduced due to impedance changes under the action of DC bias; at the same time, the equivalent model establishment method can be widely used in circuit simulation software such as Pspice, providing strong support for the design of magnetic bead filter circuits, component selection, performance prediction, etc., and has good practicality in the field of magnetic bead filter circuit simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the circuit diagram of the equivalent model of the magnetic bead filter circuit;

[0023] Figure 2 A flow chart of a method for establishing an equivalent simulation model of a magnetic bead filter circuit provided by the present invention;

[0024] Figure 3 This is the impedance characteristic curve of the magnetic bead without bias current;

[0025] Figure 4 It is the curve diagram of DC bias of magnetic beads;

[0026] Figure 5 The impedance characteristic curve diagram with 2A bias current;

[0027] Figure 6 This is the result diagram of piecewise linearization of impedance characteristic curve;

[0028] Figure 7 The figure is a comparison chart of the amplitude-frequency characteristic curves between the equivalent model simulation results and the actual test results. DETAILED DESCRIPTION

[0029] The following is a further detailed description of a method for establishing an equivalent simulation model of a magnetic bead filter circuit under a DC bias environment proposed by the present invention in combination with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following description and claims. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0030] This paper takes the ferrite bead with product number 78279225101 produced by Wurth Elektronik as an example to establish a Pspice bead filter circuit equivalent simulation model. The equivalent model of the bead filter circuit is as follows: Figure 1 As shown in the figure, it consists of two parts: a magnetic bead equivalent module and a filter capacitor. The magnetic bead equivalent module consists of a DC equivalent resistor R DC After being connected in series with the equivalent inductor l, they are respectively connected with the AC equivalent resistance R AC and equivalent capacitance C par The filter capacitor C1 is selected according to the actual design requirements. The modeling process of the equivalent simulation model of the above magnetic bead filter circuit is as follows: Figure 2 As shown, the specific steps are as follows:

[0031] 1) Image processing of impedance characteristic curve and DC bias curve. Look up the data sheet of the ferrite bead with product number 78279225101 from Wurth Elektronik and obtain the impedance characteristic curve without bias current, such as Figure 3 As shown, and the DC bias curve of the magnetic bead is as follows Figure 4 Use image processing software to adjust Figure 3 and Figure 4 The resolution is 600ppi, adjusted Figure 3 and Figure 4 The aspect ratio is fixed at 1:1.

[0032] 2) DC bias judgment. In the actual application scenario of the magnetic bead filter circuit, there is a 2A DC current bias, and the impedance characteristic curve needs to be adjusted. Figure 3 Extract the Z curve, XL curve and R curve from the Figure 4 and ensure Figure 3 Extraction curve (hereinafter referred to as curve 1) and Figure 4 The impedance curve of 2A DC bias (hereinafter referred to as curve 2) has the same starting point. After adjustment, the impedance characteristic curve of 2A bias current is as follows Figure 5 As shown, Figure 5 In the impedance characteristic curve, the low frequency section of the Z curve is composed of the low frequency section of curve 1, the high frequency section of the Z curve is composed of the high frequency section of curve 2, and the XL curve is composed of the R curve. Figure 3 Be consistent.

[0033] 3) Segmental linearization of the impedance characteristic curve. After adjusting the impedance characteristic curve in step 2), Figure 5 The part of the impedance characteristic curve related to equivalent parameter extraction is divided into the inductive section and the complex impedance section, such as Figure 6 As shown. The inductive segment is defined as the frequency range from 1MHz to the frequency value where the deviation of the tangent slope between the Z curve and the XL curve is equal to 5%. In this example, the inductive segment frequency is 1MHz to 13MHz; the complex impedance segment is defined as the frequency range from the frequency value where the deviation of the tangent slope between the Z curve and the XL curve is equal to 5% to the frequency value where the intersection of the R curve and the XL curve is located. In this example, the complex impedance segment frequency is 13MHz to 65MHz.

[0034] 4) Sampling and statistical reference points. A simple random sampling algorithm is used to extract 10 frequency points from the inductive segment and the complex impedance segment obtained in step 3). The frequency value statistics are shown in Table 1.

[0035]

[0036] Table 1 Statistical sampling frequency values

[0037] 5) Calculate the average value of equivalent parameters. First, calculate the equivalent inductance value l of the magnetic bead at the i-th sampling (1≤i≤10) according to the sampling frequency points of the inductive segment in Table 1. i , using the formula:

[0038] Xl i =2πf i l i

[0039] where f i is the frequency value of the ith extraction point in the inductive segment in step 4), xl i For the inductive segment f i The inductive reactance value corresponding to the frequency, l i is the equivalent inductance value calculated after the i-th sampling (retain 2 significant digits), and the calculation results are shown in Table 2.

[0040] <![CDATA[Frequency f i (MHz)]]> <![CDATA[Inductive reactance XL i (Ω)]]> <![CDATA[Equivalent inductance value l i (μH)]]> 1st time 3.6 3.9 0.17 2nd time 2.6 2.7 0.17 3rd 7.1 8.1 0.18 4th 1.1 1.2 0.17 5th 8.7 10.3 0.19 6th 11.3 13.0 0.18 7th 12.2 15.5 0.20 8th 10.6 12.4 0.19 9th 5.2 6.0 0.18 10th 9.7 11.5 0.19

[0041] Table 2 1 i Calculation results table

[0042] The average equivalent inductance value l is calculated using the formula:

[0043]

[0044] The calculated average equivalent inductance value l is 0.18μH.

[0045] According to the sampling frequency points of the complex impedance segment in Table 1, calculate the equivalent capacitance value C of the magnetic bead at the i-th sampling (1≤i≤10) i , using the formula:

[0046]

[0047] Among them, F i is the frequency value of the i-th extraction point of the complex impedance segment in step 4), l is the average equivalent inductance value, j is a negative number, R i is the complex impedance segment F i The resistance value corresponding to the frequency, Z i is the complex impedance segment F i The complex impedance value corresponding to the frequency and the calculation results are shown in Table 3.

[0048]

[0049] Table 3C i Calculation results statistics table

[0050] Average equivalent capacitance C par The calculation formula is:

[0051]

[0052] The average equivalent capacitance C is calculated par is 1.9nF.

[0053] 6) Establish an equivalent simulation model of the magnetic bead filter circuit. The equivalent simulation model of the magnetic bead filter circuit established is as follows: Figure 1 As shown in FIG. 1 , the equivalent model of the magnetic bead filter circuit consists of two parts: a magnetic bead equivalent module and a filter capacitor. The magnetic bead equivalent module consists of a DC equivalent resistor R DC and average equivalent inductance After connecting in series, they are respectively connected with the AC equivalent resistance R AC and the average equivalent capacitance C par The average equivalent inductance l and the average equivalent capacitance C par The values ​​of have been obtained through step 5), the average equivalent inductance value l is 0.18μH, and the average equivalent capacitance value C par is 1.9nF. Check the datasheet to get the DC equivalent resistance R DC The AC equivalent resistance R is 160Ω AC The filter capacitor C1 is 2.2μF according to the actual design requirements. The circuit diagram of the equivalent model of the magnetic bead filter circuit is constructed using Pspice simulation software, and simulation work such as frequency sweep analysis is carried out according to specific design requirements. Figure 7This is a comparison chart of the equivalent model of the magnetic bead filter circuit and the frequency sweep curve obtained by the digital frequency characteristic tester. The frequency sweep curves of the two are similar. The low-frequency resonance peak frequency values ​​obtained by simulation and actual test are 228.6kHz and 249.8kHz respectively, with an error of only 8.5%.

[0054] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for establishing an equivalent simulation model of a magnetic bead filter circuit under a DC bias environment, characterized in that: include: Step 1: Process the impedance characteristic curve and the DC bias curve images; the impedance characteristic curve and the DC bias curve are obtained by querying the magnetic bead product manual, and the obtained impedance characteristic curve and DC bias curve images are clarified and sized using image processing software; the image resolution of the impedance characteristic curve and the DC bias curve is greater than 600ppi and remains consistent, and the image aspect ratio of the impedance characteristic curve and the DC bias curve is fixed and remains consistent; Step 2: If there is no DC bias in the actual application scenario of the magnetic bead filter circuit, go directly to step 3; if there is, adjust the impedance characteristic curve; the adjustment of the impedance characteristic curve in step 2 includes: extracting the Z curve, XL curve and R curve from the impedance characteristic curve of the magnetic bead, moving the three extracted curves to the picture of the DC bias curve, and ensuring that the Z curve corresponding to the DC bias value is consistent with the starting point of the extracted curve; the low-frequency band of the newly constructed Z curve is composed of the impedance curve without bias current, and the high-frequency band is composed of the impedance curve with DC bias; Step 3: Segmented linearization of the impedance characteristic curve; the step 3 is: dividing the portion of the impedance characteristic curve obtained in the step 2 related to the extraction of equivalent parameters into an inductive segment and a complex impedance segment; wherein the inductive segment is defined as a frequency band from 1 MHz to the frequency value at the position where the deviation of the tangent slope of the Z curve and the XL curve is equal to 5%; the complex impedance segment is defined as a frequency band from the frequency value at the position where the deviation of the tangent slope of the Z curve and the XL curve is equal to 5% to the frequency value at the intersection of the R curve and the XL curve; Step 4: sampling statistical reference points; the step 4 is: using a random sampling statistical algorithm to extract n frequency points from the inductive segment and the complex impedance segment obtained in step 3, where n≥10; the random sampling statistical algorithm includes a simple random sampling algorithm, an equidistant random sampling algorithm, and a Monte Carlo random sampling algorithm; Step 5: Calculate the average value of equivalent parameters; Step 5 is: calculate the equivalent inductance value corresponding to each frequency point according to the sampled frequency points And the equivalent capacitance value , and then calculate the average equivalent inductance And the average equivalent capacitance value ; Step 6: Establish an equivalent simulation model of a magnetic bead filter circuit; the step 6 is: the equivalent model of the magnetic bead filter circuit consists of two parts: a magnetic bead equivalent module and a filter capacitor; the magnetic bead equivalent module consists of a DC equivalent resistor R DC and average equivalent inductance After connecting in series, they are respectively connected with the AC equivalent resistance R AC and average equivalent capacitance The filter capacitors are connected in parallel and selected according to the actual design requirements.

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