Method for creating a DC superposition model of a magnetic core for a noise filter and method for providing a DC superposition model of a magnetic core for a noise filter

Abstract

This document provides a method for creating a DC superposition model for simulation using SPICE (Simulation Program with Integrated Circuit Emphasis) when a magnetic core is used as a noise filter, and a method for providing that model. [Solution] The method for simulating the circuit characteristics when a DC superimposed current is applied to a magnetic core involves representing the magnetic core with an equivalent circuit using passive elements consisting of R, L, and C, measuring the frequency characteristics of the impedance by changing the DC current when a DC current is superimposed, calculating the resistance value of R, the inductance value of L, and the capacitance value of C from the frequency characteristics of the impedance at each current, constructing a DC superimposed model using a behavioral power supply based on the equivalent circuit, and setting table functions for R, L, and C as element constants of the elements used in the model, based on the obtained resistance, inductance, and capacitance values.

Description

Technical Field

[0001] The present invention relates to a method for creating a DC superposition model and a method for providing a DC superposition model for simulating the electrical characteristics of a magnetic core used in a noise filter using a circuit simulator such as SPICE (Simulation Program with Integrated Circuit Emphasis).

Background Art

[0002] As demands for electronic devices for higher speed, larger capacity, smaller size, lighter weight, and lower power consumption increase, shortening the development period and reducing costs of electronic devices have become essential for improving competitiveness. For this reason, a highly accurate simulation model is required to reduce the number of prototype experiments. In electronic circuit design, circuit simulators such as SPICE (Simulation Program with Integrated Circuit Emphasis) are used.

[0003] The inductance of a magnetic core used in a noise filter or the like changes depending on a DC bias voltage or a DC current applied in superposition, and this change cannot be ignored when performing circuit simulation for noise countermeasures.

[0004] Ferrites widely used in magnetic cores are ceramics mainly composed of iron oxide, and most magnetic cores are often used in a ring shape. By passing a conductor through the hole of the ring, an inductor is formed by the conductor and the ferrite core. This inductor has a higher impedance as the frequency becomes higher. Therefore, it acts as a low-pass filter that blocks high-frequency currents and can attenuate high-frequency noise. Also, a part of the noise current passing through the conductor is lost as magnetic loss, which has a noise removal effect.

[0005] The increasing digitalization and high-current capabilities of equipment are driving a growing demand for noise suppression in the high-frequency range. Setting the optimal magnetic core for noise suppression is a complex, time-consuming, and labor-intensive process, requiring highly accurate circuit simulation techniques. Therefore, SPICE simulations that consider DC superposition characteristics are also required for noise suppression.

[0006] Various simulation methods that take into account the DC superposition characteristics of capacitors and inductors have been developed, mainly by companies that manufacture and sell electronic components, and many of these methods are provided free of charge.

[0007] For example, the following method is disclosed as a method for constructing a superimposed equivalent circuit. This method constructs the superimposed equivalent circuit of a passive element in a superimposed state where current or voltage is superimposed, using the reference state equivalent circuit of the passive element in a reference state where no current or voltage is superimposed. This method includes the step of supplying a current or voltage corresponding to the difference between the non-superimposed characteristics in the reference state of the passive element and the superimposed characteristics in the superimposed state to correct the difference. More specifically, this method involves connecting a voltage source and a current sensor between the external terminals of the superimposed equivalent circuit, and connecting the reference state equivalent circuit, a current source, and a voltage sensor to an independent closed-loop circuit not connected between the external terminals of the superimposed equivalent circuit. The current between the external terminals is detected by the current sensor, and a current dependent on this detection result is supplied from the current source to the reference state equivalent circuit. The voltage generated in the reference state equivalent circuit by this supply of current is detected by the voltage sensor, and a voltage dependent on this result is output from the voltage source to perform the correction (see, for example, Patent Document 1).

[0008] Furthermore, a simulation model for an inductor is disclosed that ensures the simulation results of a circuit including an inductor do not deviate significantly from the actual operation of the circuit. Specifically, it is a simulation model for an inductor when a triangular wave current superimposed with a DC current flows through it, and the equivalent circuit of the inductor is a series circuit of the DC resistance and the apparent AC resistance and inductance adjusted for AC losses, and the DC resistance of the inductor is a first function of the amplitude of the triangular wave and the DC current superimposed on the triangular wave, the apparent AC resistance of the inductor is a second function of the amplitude of the triangular wave, the DC current superimposed on the triangular wave and the frequency of the triangular wave, and the inductance of the inductor is a second function of the amplitude of the triangular wave, the DC current superimposed on the triangular wave and the frequency of the triangular wave The third function is defined as a first behavioral current source controlled by a formula obtained by dividing the voltage across its terminals by the value obtained by the first function, the apparent AC resistance is defined as a second behavioral current source controlled by a formula obtained by dividing the voltage across the AC resistance by the value obtained by the second function, the inductance is defined as a third behavioral current source controlled by a formula obtained by dividing the integral of the voltage across its inductance by the value obtained by the third function, and the DC superimposed current of the triangular wave is obtained by smoothing the current flowing through the first behavioral current source using a smoothing circuit. This simulation model determines the amplitude of the triangular wave by subtracting the value of the superimposed current of the triangular wave from the current value flowing through the first behavioral current source and then peak-holding the result in a peak-hold circuit. The frequency of the triangular wave is determined by subtracting the value of the DC superimposed current of the triangular wave from the current value flowing through the first behavioral current source, converting the result into a pulse wave in a waveform conversion circuit, and then counting the pulse wave in a counter circuit (see, for example, Patent Document 2).

[0009] Furthermore, for example, a simulation method and a nonlinear equivalent circuit model for an inductor that can dynamically simulate the nonlinear characteristics of an inductor with high accuracy when a DC current is superimposed are disclosed. Specifically, the equivalent circuit of the inductor is represented using a passive circuit element, the rate of change of the characteristics of the passive circuit element when a DC current is superimposed is represented as an approximate function with current as a variable based on measured values, the current flowing through the inductor is referenced, and based on the rate of change of the characteristics calculated by the approximate function corresponding to the referenced current, and the voltage generated in the passive circuit element when no DC current is superimposed, a control voltage source connected in series with the passive circuit element whose characteristics change due to the superposition of a DC current generates a difference voltage between the superimposed voltage and the unsupervised voltage generated in the passive circuit element when a DC current is superimposed, and the nonlinear characteristics of the inductor when a DC current is superimposed are simulated by superimposing the difference voltage on the unsuperimposed voltage (see, for example, Patent Document 3).

[0010] Furthermore, for example, a method for analyzing the circuit constants of an equivalent circuit model is disclosed, aimed at effectively suppressing the occurrence of errors between circuit design using a circuit simulator and actual circuit performance. Specifically, a series circuit of inductance L1 and resistance R1, considering the skin effect of the internal conductor, is connected in parallel with the mutual inductance Lm between the DC inductance L0 and inductance L1, and the DC resistance Rdc1 of the internal conductor is connected in series to this. Next, the parasitic inductance Ls of the external electrode is connected in series with the equivalent inductance L0, and the DC resistance Rdc2 of the external electrode is connected in series with the DC resistance Rdc1 of the internal conductor. In addition, an equivalent circuit model is used in which a series circuit in which parasitic capacitance Cp and resistance Rp representing the loss of the dielectric constituting the chip are connected in series is connected in parallel inside the equivalent elements Ls and Rdc2 of the external electrode (see, for example, Patent Document 4). [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2018-160132 [Patent Document 2] Japanese Patent Publication No. 2017-091346 [Patent Document 3] International Publication Number WO2014 / 185294 [Patent Document 4] Japanese Patent Publication No. 2010-204869 [Overview of the project] [Problems that the invention aims to solve]

[0012] The invention described in Patent Document 1 is characterized by its ability to accurately represent the characteristics when current or voltage is superimposed, by adding a power supply circuit that represents the characteristic change when current or voltage is superimposed, based on an equivalent circuit where current or voltage is in a reference state. To achieve this, a current sensor or voltage sensor is used to make it dependent on the current of the current source or the voltage of the voltage source, resulting in a complex configuration.

[0013] The invention described in Patent Document 2 is a simulation model for an inductor when a triangular wave current superimposed with a DC current flows, and is intended for simulation when a large amplitude current flows under certain conditions, such as in a power inductor used in a DC-DC converter, and is difficult to apply to the field of noise filters using magnetic cores such as ferrite cores.

[0014] The invention described in Patent Document 3 is a simulation method for inductors, specifically for inductors used in power supply circuits such as DC-DC converters. Therefore, its application to the noise filter field is difficult. The invention described in Patent Document 4 concerns a simulation method for multilayer chip inductors, and is difficult to apply to the field of noise filters.

[0015] When using magnetic cores such as ferrite cores as noise filters, an inductor is constructed by passing or winding wires around the magnetic core. It is known that the inductance of an inductor rapidly decreases when the DC saturation current is exceeded. When used as a noise filter, not only can the noise level and noise frequency not be set in advance, but the inductance (L) decreases as the current increases (DC superposition characteristic), and the core's permeability (μ) and saturation magnetic flux density (Bs) also change due to heat generation.

[0016] The present invention aims to provide a method for creating a DC superposition model for simulation using SPICE when a magnetic core including a ferrite core is used as a noise filter, and a method for providing the DC superposition model to the user. [Means for solving the problem]

[0017] To solve the above-mentioned conventional problems, the present invention provides a method for creating a DC superposition model, which is a method for simulating the circuit characteristics when a DC superposition current is applied to a magnetic core used as a noise filter using SPICE (Simulation Program with Integrated Circuit Emphasis), and is characterized by comprising: a first step of representing the magnetic core with an equivalent circuit using passive elements consisting of a resistor (R), an inductor (L), and a capacitor (C); a second step of measuring the frequency characteristics of the impedance by changing the DC current when a DC current is superimposed, and calculating the resistance value, inductance value, and capacitance value of the resistor (R), inductor (L), and capacitor (C) from the frequency characteristics of the impedance at each DC current; and a third step of constructing a DC superposition model using a behavioral power supply based on the equivalent circuit, and setting table functions for the resistor (R), inductor (L), and capacitor (C) as element constants of the elements used in the DC superposition model, based on the resistance value, inductance value, and capacitance value obtained above.

[0018] Furthermore, in the second step of the above method, the resistance value may be calculated from the resistance value at the resonant frequency, the inductance value from the slope on the low-frequency side of the resonant frequency, and the capacitance value from the resonant frequency. Note that the method for determining the resistance value, inductance value, and capacitance value is not limited to the above and other methods may be used.

[0019] Furthermore, in the above method, the magnetic cores may be composed of different materials and / or shapes, and the second and third steps may be performed for each magnetic core composed of different materials and / or shapes to create a DC superposition model for each magnetic core made of different materials and / or shapes. In the above, the expression "different materials and / or shapes" refers to cases where the materials are different, where the shapes are different, and where the materials and shapes are each different.

[0020] While ferrite is commonly used as the material for magnetic cores, other materials such as dust materials, amorphous materials, and nanocrystals are also used. Since each of these materials has different magnetic properties, it is necessary to create individual DC superposition models, particularly table functions, for each. Furthermore, the magnetic properties of a magnetic core also differ depending on its shape, such as ring diameter and width, so it may be necessary to create individual DC superposition models, particularly table functions, for these as well. However, if nearly the same resistance, inductance, and capacitance values ​​can be used even with different shapes, the same DC superposition model may be used.

[0021] The inductance of a magnetic core decreases as the current increases; this is known as the DC superposition characteristic. Furthermore, as the current increases and heat is generated, the permeability and saturation magnetic flux density of the core change. Therefore, high accuracy cannot be obtained with static simulation methods. However, in the DC superposition model of the present invention, the table functions of resistance, inductance, and capacitance are set for the magnetic core based on measured data, making high-accuracy simulation possible even when the DC superposition current changes.

[0022] Next, a method for providing a DC superposition model of the present invention is a method for simulating circuit characteristics when a DC superposition current is applied to a magnetic core used as a noise filter using SPICE. The provider of the magnetic core represents the magnetic core by an equivalent circuit using passive elements consisting of a resistor (R), an inductor (L), and a capacitor (C), measures the frequency characteristics of impedance by changing the DC current during DC current superposition, calculates the resistance value, inductance value, and capacitance value from the frequency characteristics of impedance at each DC current, constructs a DC superposition model using a behavioral power supply based on the above equivalent circuit, and sets a table function for the resistor (R), inductor (L), and capacitor (C) based on the resistance value, inductance value, and capacitance value calculated above as the element constants of the elements used in the DC superposition model to create a DC superposition model. A first step, a second step of storing information on the DC superposition model and the magnetic core in a computer, and a third step of publicly releasing information on the magnetic core via the Internet by the computer are performed. When a user who performs noise countermeasures using the magnetic core accesses the information on the magnetic core via the Internet and wishes to obtain the information, the provider of the magnetic core permits the user to download the information on the magnetic core including the DC superposition model.

[0023] Furthermore, in the calculation of the resistance value, inductance value, and capacitance value, the resistance value may be calculated from the resistance value at the resonance frequency, the inductance value may be calculated from the slope on the low-frequency side of the resonance frequency, and the capacitance value may be calculated from the resonance frequency.

[0024] Also, when the magnetic core is composed of different materials and / or shapes, the provider of the magnetic core may calculate the resistance value, inductance value, and capacitance value for each magnetic core composed of different materials and / or shapes in the above first step, create a DC superposition model for each magnetic core composed of different materials and / or shapes, and store these DC superposition models and information related to the magnetic core in a computer.

[0025] By adopting the above-provided method, the provider of the magnetic core represents the magnetic core that functions as an inductor with a behavioral power source, and sets a table function based on the measured values for the resistance, inductor, and capacitor represented by an equivalent circuit. Therefore, even when the DC superposition current changes, high-precision simulation can be performed. As a result, the user can easily perform circuit simulation using SPICE in the simulation for using the magnetic core.

Advantages of the Invention

[0026] The method for providing the simulation model of the magnetic core of the present invention can be widely used by users who perform noise countermeasures using the magnetic core, and has a great effect in various noise countermeasure fields.

Brief Description of the Drawings

[0027] [Figure 1] It is a diagram showing an equivalent circuit of the magnetic core according to the present embodiment. [Figure 2] It is a diagram showing a basic circuit configuration of a magnetic core that functions as an inductor. [Figure 3] It is a diagram showing a first basic model for showing by mathematical formula that the DC superposition model shown in FIG. 5 is established. [Figure 4] It is a diagram showing a second basic model for showing by mathematical formula that the DC superposition model shown in FIG. 5 is established. [Figure 5]This diagram illustrates a method for determining the table function of a DC superposition model. (a) shows the resistance, inductance, and capacitance values ​​that change with the DC superposition current in the equivalent circuit, and (b) is a diagram illustrating the DC superposition model and its table function. [Figure 6] Figure 5 shows the frequency characteristics of each impedance in the equivalent circuit and the simulation results of the impedance frequency characteristics obtained by setting a table function in the DC superposition model. (a) is the simulation result obtained in Figure 5(a), and (b) is the simulation result obtained using the DC superposition model in Figure 5(b). [Figure 7] This is the result of determining the correlation between frequency and impedance using the DC superposition model of the present invention, with the DC superposition current as a parameter. [Figure 8] Figure 7 shows the device configuration used to obtain the measured values. [Figure 9] This shows the result of determining the change in inductance (Ls) due to DC superimposed current when using a MnZn core (E04RM251512: manufactured by Seiwa Electric Co., Ltd.) as the magnetic core. [Figure 10] This shows the result of determining the change in inductance (Ls) due to DC superimposed current when using a nanocrystal core (E04RK254015: manufactured by Seiwa Electric Co., Ltd.). [Figure 11] This is a simple diagram illustrating a configuration in which a user places a magnetic core model between an inverter (INV) and a motor (Motor) as a noise countermeasure in a power circuit and evaluates its noise characteristics. [Figure 12] This diagram shows the steps for a user to download a DC superposition model of a magnetic core, incorporate it into a circuit they are designing, and simulate it. [Modes for carrying out the invention]

[0028] (Embodiment) A method for creating a DC superposition model and a method for providing a DC superposition model according to embodiments of the present invention will be described in detail.

[0029] Figure 1 shows the equivalent circuit of the magnetic core according to this embodiment. In Figure 1, L1 is the inductor of the magnetic core, C1 is the capacitor representing the parasitic capacitance of the magnetic core, and R1 and R2 are the resistive components of the magnetic core. Figure 2 shows the basic circuit configuration of a magnetic core that functions as an inductor. Figure 3 shows the first basic model used to mathematically demonstrate that the DC superposition model shown in Figure 5 is valid. Figure 4 shows a second basic model used to mathematically demonstrate that the DC superposition model shown in Figure 5 is valid.

[0030] Figure 5 illustrates a method for determining the table function of the DC superposition model. (a) shows the resistance, inductance, and capacitance values ​​that change with the DC superposition current in the equivalent circuit, and (b) is a diagram illustrating the DC superposition model and the table function. The method for creating a DC superposition model according to this embodiment will be described in detail below using these figures.

[0031] The DC superposition model creation method according to this embodiment is a method for creating a model for simulating the circuit characteristics when a DC superposition current is applied to a magnetic core used as a noise filter, using SPICE, and is characterized by including: a first step of representing the magnetic core as an equivalent circuit using passive elements consisting of a resistor (R), an inductor (L), and a capacitor (C); a second step of measuring the frequency characteristics of the impedance by changing the DC current when a DC current is superimposed, and calculating the resistance value, inductance value, and capacitance value from the frequency characteristics of the impedance at each DC current; and a third step of constructing a DC superposition model using a behavioral power supply based on the equivalent circuit, and setting table functions for the resistor (R), inductor (L), and capacitor (C) as element constants of the elements used in the DC superposition model, based on the resistance value, inductance value, and capacitance value obtained above.

[0032] In this embodiment, in the second step of the method described above, the resistance value is calculated from the resistance value at the resonant frequency, the inductance value is calculated from the slope on the low-frequency side of the resonant frequency, and the capacitance value is calculated from the resonant frequency. However, the method for determining the resistance value, inductance value, and capacitance value is not limited to the above and other methods may be used. Also, although there are various types of magnetic cores with different materials and shapes, this embodiment will describe the case using a ferrite core as an example. The following explains in detail how to create and provide the simulation model. (Equivalent circuit of a magnetic core)

[0033] The characteristics of a magnetic core can be represented by an equivalent circuit using passive elements R, L, and C, as shown in Figure 1. However, even if a simulation is performed using LT-SPICE with DC superimposed on the magnetic core using such an equivalent circuit, only static characteristics can be represented if the constants of the R, L, and C elements are set to constant values. However, since the characteristics of a magnetic core change with current, this equivalent circuit cannot provide an accurate evaluation.

[0034] Therefore, as shown in Figure 5(b), we constructed a DC superposition model incorporating a behavioral power supply and decided to use a table function with measured values ​​for the element constants of the passive elements. Below, the validity of this DC superposition model will be explained using mathematical formulas based on the first basic model shown in Figure 3. (First basic model)

[0035] The magnetic core used for noise suppression acts as an inductor, either by passing a wire through it or winding it around it. The basic circuit configuration is shown in Figure 2. Figure 3 shows the first basic model of the DC superposition model shown in Figure 5(b). In the DC superposition model shown in Figure 5(b), a behavioral voltage source (V0) is placed and used as an ammeter, so that the table function does not contain undefined variables, eliminating the need for the user to set variables each time. In addition, the inductor, which is the magnetic core, is represented as a behavioral current source, so that the user can respond to the DC current superposition by using the set table function without having to worry about variables.

[0036] In Figure 2, when DC is applied to the inductor (L1), the voltage (VL) across the inductor is proportional to the rate of change of the current (ΔIL / Δt), and is expressed by Equation 1.

[0037]

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[0038] In Figure 3, B1 and B2 are behavioral voltage sources; B1 outputs VL, and B2 outputs v2 depending on V. B3 is a behavioral current source. In this case, VL is represented by equation 2.

[0039]

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[0042] Here, R3 in Figure 3 is set to 1 mΩ, which is a very small value, so it can be approximated as 0. In that case, R3iL can be considered as 0. Also, since L1 is set to a constant of 1 (H), 1 / L1 = 1 in equation 4. Therefore, equation 4 is finally obtained. Next, since i and iL shown in Figure 3 are the same, equation 5 holds true.

[0043]

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[0048] From the above results, we can make equation 3 true by outputting the value obtained from B2 using equation 10. Therefore, we can simulate the magnetic core constituting the inductor using the first basic model shown in Figure 3.

[0049]

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[0050] The second basic model is shown in Figure 4. Compared to the first basic model shown in Figure 3, the second basic model shown in Figure 4 consists of a behavioral voltage source B3 and a behavioral current source B2. The output VL1 of the behavioral power supply B1 can be expressed in the same way as in the first basic model. This is shown in Equation 11.

[0051]

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[0052] For the behavioral power supply B3 shown in Figure 4 to behave as an inductor with inductance (f(i)), it is required to satisfy equation 12 from equation 1. This is the same as the first SPICE model.

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[0054] Next, we will explain how using the second basic model yields a formula equivalent to equation 12. Using equation 1 obtained from Figure 2, the inductor (L1) can be represented by equation 13.

[0055]

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[0060] As shown in Figure 1, the magnetic core was represented by an equivalent circuit using passive elements consisting of a resistor (R), an inductor (L), and a capacitor (C). Next, the frequency characteristics of the impedance were measured by varying the DC current when a DC current was superimposed on the magnetic core, and the resistance, inductance, and capacitance values ​​were calculated from the frequency characteristics of the impedance at each DC current. In this embodiment, the resistance value was calculated from the resistance value at the resonant frequency, the inductance value was calculated from the slope on the low-frequency side of the resonant frequency, and the capacitance value was calculated from the resonant frequency.

[0061] Figure 5 shows specific examples of resistance, inductance, and capacitance values ​​calculated according to the superimposed DC current. In Figure 5, (a-1) is the case when the superimposed DC current is 0A, (a-2) is the case when the superimposed DC current is 1A, (a-3) is the case when the superimposed DC current is 5A, and (a-4) is the case when the superimposed DC current is 10A. For example, in (a-1) when the superimposed DC current is 0A, R1=37.8Ω, R2=41.3Ω, C1 (capacitance value)=1.3nF, and L1 (inductance value)=6.7μH. In (a-4) when the superimposed DC current is 10A, R7=17.3Ω, R8=22.6Ω, C4 (capacitance value)=1.5nF, and L1 (inductance value)=0.16μH. Thus, as the DC superimposed current increases, the resistance and inductance values ​​decrease, but the capacitance value does not change much. Note that the equivalent circuits for resistance, inductance, and capacitance are the same, but their values ​​differ depending on the DC superimposed current, so they are distinguished by their signs.

[0062] Figure 5(b) is a DC superposition model based on the first basic model. In this DC superposition model, the table function is set based on the values ​​obtained in Figure 5(a). The capacitance value of C5 is shown in Equation 18. The values ​​of R9 and R10 are shown in Equations 19 and 20. The output of B1 is shown in Equation 21.

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[0067] By determining the values ​​for each DC current based on the equivalent circuit, creating table functions using these values, and setting table functions (Equations 18-21) when running this DC superposition model in SPICE, it became possible to perform accurate simulations even when a DC superposition current is applied.

[0068] Figure 6 shows the simulation results for the frequency characteristics of each impedance in the equivalent circuit shown in Figure 5, and the frequency characteristics of the impedance obtained by setting a table function in the DC superposition model. Figure 6(a) shows the simulation results obtained in Figure 5(a), and Figure 6(b) shows the simulation results obtained using the DC superposition model in Figure 5(b). Both show similar behavior, and it was confirmed that the DC superposition model can provide sufficiently high-accuracy simulations even when the DC superposition current changes.

[0069] In Figure 5(a), the DC currents are set to 0A, 1A, 5A, and 10A, but in practice, it is preferable to apply a wider range of current values ​​to obtain the values ​​and reflect them in the table function. Furthermore, it is preferable to extend the maximum current value to an even wider range. (Comparison of simulation results and actual measurements)

[0070] Figure 7 shows the results of determining the correlation between frequency and impedance using the DC superposition model of the present invention, with the DC superposition current as a parameter. A MnZn core (E04RM251512: manufactured by Seiwa Electric Co., Ltd.) was used as the magnetic core. The simulation is displayed using SIM, and the measured values ​​are displayed using MEAS. (a) shows the results when the DC superposition current is 0A, (b) is 1A, (c) is 5A, (d) is 8A, (e) is 10A, and (f) is 15A. It can be seen that the measured values ​​and the simulation values ​​using the DC superposition model agree well even when the DC superposition current changes from 1A to 15A. The measured values ​​were measured using the apparatus configuration shown in Figure 8.

[0071] Figure 9 shows the results of determining the change in inductance (Ls) due to DC superimposed current when using a MnZn core (E04RM251512: manufactured by Seiwa Electric Co., Ltd.) as the magnetic core. (a) shows the case when the frequency is 10 kHz, and (b) shows the case when the frequency is 100 kHz. The simulation is displayed using SIM, and the measured values ​​are displayed using MEAS. As can be seen from the figure, the simulation data and measured values ​​show good agreement up to a DC superimposed current of 15 A.

[0072] Figure 10 shows the results of determining the change in inductance (Ls) due to DC superimposed current when using a nanocrystal core (E04RK254015: manufactured by Seiwa Electric Co., Ltd.). (a) shows the case when the frequency is 10 kHz, and (b) shows the case when the frequency is 100 kHz. The simulation is displayed using SIM, and the measured values ​​are displayed using MEAS. As can be seen from the figure, the simulation data and measured values ​​show good agreement up to a DC superimposed current of 2 A. As described above, the simulation model of the present invention shows good agreement with measured values ​​for a magnetic core superimposed with a DC current. (Method for providing a DC superposition model)

[0073] The method for providing a DC superposition model for magnetic cores is a method for simulating the circuit characteristics when a DC superposition current is applied to a magnetic core used as a noise filter, using SPICE.

[0074] Specifically, the provider of the magnetic core represents the magnetic core as an equivalent circuit using passive elements consisting of a resistor (R), an inductor (L), and a capacitor (C). They measure the frequency characteristics of the impedance by changing the DC current when a DC current is superimposed, and calculate the resistance, inductance, and capacitance values ​​from the frequency characteristics of the impedance at each DC current. Next, they construct a DC superposition model using a behavioral power supply based on the above equivalent circuit, and create the DC superposition model by setting table functions for the resistor (R), inductor (L), and capacitor (C) based on the resistance, inductance, and capacitance values ​​calculated above as the element constants of the elements used in the DC superposition model. Next, the created DC superposition model and information about the magnetic core are stored in the computer.

[0075] Furthermore, information about magnetic cores will be made publicly available via the internet using computers. In this case, the information about magnetic cores includes data necessary for users to select a magnetic core, such as frequency bandwidth, availability of a DC superposition model compatible with SPICE, impedance map, applicable cable diameter, and product shape.

[0076] Next, if a user who uses magnetic cores for noise reduction accesses information about magnetic cores via the internet and wishes to obtain such information, the provider of the magnetic cores allows the user to download information about the magnetic cores, including a DC superposition model. In this case, it is preferable that when a user wishes to obtain the DC superposition model, the provider requests user registration, and only allows the download after user registration is complete.

[0077] This allows the user to select the optimal magnetic core from the information related to the magnetic core, download the DC superposition model for that magnetic core, incorporate it into the circuit they intend to design, and perform a simulation. The DC superposition model of the magnetic core in this invention has a table function set up, and since there is no need to deal with undefined variables, simulation can be easily performed.

[0078] The computer used in this embodiment may be a regular personal computer. However, in this case, since it is necessary to store a large amount of information about magnetic cores, it is preferable to store this information on a server and allow the computer to access the server. A regular personal computer can also be used by the user.

[0079] This document describes an example of using the DC superposition model of the present invention using SPICE. Figure 11 is a simple configuration diagram in which a user places a magnetic core model between an inverter (INV) and a motor (Motor) as a noise countermeasure in a power circuit and evaluates its noise characteristics. In such a case, the user downloads the DC superposition model of the magnetic core using the procedure shown in Figure 12, incorporates it into the circuit to be designed, and simulates it. First, the user downloads the SPICE software from the internet. Next, the downloaded SPICE software and symbols are stored in a designated folder in LTspice. Then, the DC superposition model of the present invention is placed in the circuit to be simulated. After this state is reached, the circuit simulation is started. This allows the user to very easily simulate noise countermeasures using a magnetic core.

[0080] Furthermore, in calculating resistance, inductance, and capacitance values, the resistance value may be calculated from the resistance value at the resonant frequency, the inductance value from the slope on the low-frequency side of the resonant frequency, and the capacitance value from the resonant frequency. However, this is not the only way to do so.

[0081] Furthermore, if the magnetic cores are composed of different materials and / or shapes, the provider of the magnetic cores may calculate the resistance, inductance, and capacitance values ​​for each magnetic core composed of different materials and / or shapes in the first step described above, create a DC superposition model for each magnetic core composed of different materials and / or shapes, and store these DC superposition models and information about the magnetic cores in a computer.

[0082] In addition to LTspice (Analog Devices), which was used in this invention, other circuit simulators such as Pspice (Texas Instruments), ADC (Keysight Advanced Design Systems), CST (AET), Ansys (Ansys), QucsStudio (developer: Michael Margraf), and MicroCAP (Toyo Technica) are also available, and this invention can be applied to these as well. [Industrial applicability]

[0083] The method for creating a simulation model of a magnetic core and the method for providing such a simulation model according to the present invention will have a significant effect on electrical and electronic fields where noise countermeasures are required, such as power supply circuits, motor drive circuits, and high-frequency circuits. [Explanation of symbols]

[0084] C1 Capacitor R1, R2, R resistance L1 Inductor (1H) SW Switch IL current VL Voltage B1, B2, B3 Behavioral Power Supply i, iL current R3 resistance (1mΩ) C1, C2, C3, C4, C5 Capacitors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10 resistance L1, L2, L3, L4 Inductors L6 Inductor (1H) INV Inverter Motor

Claims

1. A method for creating a DC superposition model for simulating the circuit characteristics when a DC superposition current is applied to a magnetic core used as a noise filter, using SPICE (Simulation Program with Integrated Circuit Emphasis), The first step is to represent the magnetic core with an equivalent circuit using passive elements consisting of a resistor (R), an inductor (L), and a capacitor (C), A second step involves varying the DC current when a DC current is superimposed and measuring the frequency characteristics of the impedance, and calculating the resistance value of the resistor (R), the inductance value of the inductor (L), and the capacitance value of the capacitor (C) from the frequency characteristics of the impedance at each DC current. A method for creating a DC superposition model, characterized by comprising: a third step of constructing a DC superposition model using a behavioral power supply based on the equivalent circuit described above; and setting table functions for the resistor (R), inductor (L), and capacitor (C) based on the resistance value, inductance value, and capacitance value, as element constants for the elements used in the DC superposition model.

2. In the second step described above, A method for creating a DC superposition model, characterized in that the resistance value is calculated from the resistance value at the resonant frequency, the inductance value is calculated from the slope on the low-frequency side of the resonant frequency, and the capacitance value is calculated from the resonant frequency.

3. The method for creating a DC superposition model according to claim 1, characterized in that the magnetic cores are made of different materials and / or shapes, and the second step and the third step are performed for each magnetic core made of different materials and / or shapes to create a DC superposition model for each magnetic core made of different materials and / or shapes.

4. A method for providing a DC superposition model for simulating the circuit characteristics when a DC superposition current is applied to a magnetic core used as a noise filter, using SPICE (Simulation Program with Integrated Circuit Emphasis), The provider of the magnetic core said, The magnetic core is represented by an equivalent circuit using passive elements consisting of a resistor (R), an inductor (L), and a capacitor (C). The frequency characteristics of the impedance are measured by changing the DC current when a DC current is superimposed, and the resistance value of the resistor (R), the inductance value of the inductor (L), and the capacitance value of the capacitor (C) are calculated from the frequency characteristics of the impedance at each DC current. The first step is to construct a DC superposition model using a behavioral power supply based on the equivalent circuit, and then create the DC superposition model by setting table functions for the resistor (R), inductor (L), and capacitor (C) based on the calculated resistance, inductance, and capacitance values ​​as element constants for the elements used in the DC superposition model, A second step involves storing the DC superposition model and the information relating to the magnetic core in a computer. The computer then performs a third step of making information regarding the magnetic core publicly available via the internet. A method for providing a DC superposition model for a magnetic core, characterized in that when a user who performs noise countermeasures using the magnetic core accesses information about the magnetic core via the internet and wishes to obtain such information, the provider of the magnetic core allows the user to download information about the magnetic core, including the DC superposition model.

5. A method for providing a DC superposition model, characterized in that, in calculating the resistance value, inductance value, and capacitance value, the resistance value is calculated from the resistance value at the resonant frequency, the inductance value is calculated from the slope on the low-frequency side of the resonant frequency, and the capacitance value is calculated from the resonant frequency.

6. If the magnetic core is composed of different materials and / or shapes, In the first step, the provider of the magnetic core calculates the resistance value, inductance value, and capacitance value for each different material and / or magnetic core. Create DC superposition models for different materials and / or for each of the magnetic cores, A method for providing a DC superposition model of a magnetic core, characterized by storing information relating to the DC superposition model and the magnetic core in a computer.

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