Inductor noise optimization method based on multi-physics field simulation

Abstract

The invention discloses an inductor noise optimization method based on multi-physics field simulation, and belongs to the technical field of magnetic component simulation design. According to the method, COMSOL software is adopted to customize a solution domain equation to calculate three kinds of electromagnetic force coupling of Lorentz force, Maxwell force and magnetostriction force of the inductor, the coupling is converted into electromagnetic force in a frequency domain through Fourier transform, solid mechanical field simulation is carried out, and magnetostriction generated by an electromagnetic field is coupled to a solid mechanical field in a strain form; calculating the surface acceleration of the inductor in the frequency domain; and then simulating an external sound field of the inductor by taking the surface acceleration of the inductor in the frequency domain as an excitation source of pressure acoustics to obtain a change diagram of the sound pressure level at the noise point to be detected along with the frequency. By the adoption of the method, various electromagnetic forces borne by the inductor can be comprehensively considered, simulation time can be greatly shortened by conducting simulation of the solid mechanical field and the pressure acoustic field in the frequency domain, and therefore noise simulation of the inductor is accurately and efficiently completed.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic component simulation design, and in particular relates to an inductor noise optimization method based on multi-physics field simulation. Background Art

[0002] As the functionality of electronic devices continues to increase, power inductors in DC-DC converters have become a source of noise. DC-DC converters use switching devices to generate pulsed currents. When used under light load conditions, the DC-DC converter automatically switches from PWM (Pulse Width Modulation) to PFM (Pulse Frequency Modulation), reducing the switching frequency. Because switching losses are proportional to frequency, lowering the frequency can improve efficiency under light load conditions. However, this reduced frequency falls within the audible range of approximately 20 to 20 kHz, causing the power inductor to generate noise, known as whistling. This whistling can significantly impact the use of molded inductors. Therefore, using appropriate methods to simulate and predict the noise of molded inductors is crucial for their design.

[0003] Chinese invention patent publication number CN106599395A discloses a numerical simulation calculation method for the noise of oil-immersed transformers. This method can only be applied to the noise prediction of existing transformer products, while the noise of inductor products cannot be predicted and optimized by this method. Chinese invention patent publication number CN117473663A discloses a simulation prediction method for the eccentric noise of the traction motor rotor. This method reduces the calculation time of the noise excitation physical quantity and realizes the accurate prediction of the rotor eccentric noise. At present, the electromagnetic noise simulation methods for electronic components are mainly applied to transformers and motors, while there are fewer noise simulation methods for inductors. However, there are structural differences between inductors and other electronic components, so there is an urgent need for a simulation method for the electromagnetic noise of inductors.

[0004] Using COMSOL software, you can select the required modules to implement multi-physics coupling analysis, that is, establish partial differential equations for separate physical fields separately, and then solve these partial differential equations jointly. In order to achieve the joint solution, first select the model equation and determine the partial differential equation in COMSOL software, create or import the physical model, set the material properties, solve the domain and boundary conditions, mesh the model, select the appropriate solver to solve, and finally display the post-processing results. COMSOL can customize the solution domain equation to achieve arbitrary multi-physics coupling, while Ansys, Maxwell, Magnet, Flux and other software do not have this function. In view of the advantages of COMSOL software, the electromagnetic noise of the inductor can be effectively predicted by using the multi-physics coupling simulation method. Summary of the Invention

[0005] The purpose of the present invention is to address the problems existing in the background technology and propose an optimization method for inductor noise based on multi-physics field simulation.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for optimizing inductor noise based on multi-physics simulation includes the following steps:

[0008] Step 1: Establish a three-dimensional simulation model of the inductor based on the actual size and material of the inductor. The size parameters of the inductor include the size parameters of the core column and the magnetic shielding shell, the width and thickness of the copper coil, and the number of coil turns.

[0009] Detect the electromagnetic performance parameters of the inductor, including DC inductance, core permeability, core magnetostriction coefficient, BH curve, AC impedance and AC inductance, etc.;

[0010] Step 2: Assign electromagnetic properties to the inductor material based on the electromagnetic performance parameters measured in step 1, then perform magnetic field simulation on the three-dimensional simulation model of the inductor, input a sinusoidal AC excitation to the inductor under normal working conditions, and obtain the transient electromagnetic force on the inductor under the AC excitation. The transient electromagnetic force includes the Maxwell force and magnetostrictive force on the magnetic core, and the Lorentz force on the copper coil;

[0011] Step 3: Perform a fast Fourier transform (FFT) on the transient electromagnetic force on the inductor to obtain the electromagnetic force in the frequency domain; then, use the electromagnetic force in the frequency domain as the excitation source of the solid mechanics field to calculate the surface displacement of the inductor, and then calculate the surface acceleration of the inductor in the frequency domain;

[0012] Step 4: Use the surface acceleration of the inductor in the frequency domain as the excitation source for pressure acoustics to simulate the external sound field of the inductor. Select the noise test point above the inductor surface as the microphone point and calculate the change of the sound pressure level at this point with frequency.

[0013] After connecting the inductor described in step 1 to AC power, place it in a silent box, and use noise testing equipment to test the sound pressure level at the noise test point. The measured data are compared with the data obtained by the above simulation to verify the reliability of the simulation method.

[0014] Furthermore, in step 4, the sound pressure value is calculated using the following formula:

[0015]

[0016] The coefficient ρ0 is the fluid density, P is the sound pressure, ω is the angular frequency, C C is the bulk modulus.

[0017] Furthermore, the actual size of the inductor in step 1 should meet the design objectives of the inductor, which include the voltage and operating frequency, package size, inductance, DC resistance, and AC resistance of the inductor under normal operating conditions.

[0018] Preferably, the inductor design goals for step 1 are: a sinusoidal AC current of 1-1.25A and an operating frequency of 1-3MHz under normal operating conditions; the inductor's magnetic core structure consists of a core center column and a core shell, with an inductance of 0.8-1.2μH, a DC resistance of less than 40mΩ, and an AC resistance of less than 100mΩ under operating conditions. The inductor is a one-piece molded inductor, comprising an elliptical core center column, two layers of racetrack-shaped spiral coils wound around the core, and a magnetic shielding material covering the core and copper coil. The spiral coil has two leads that serve as electrodes, which are stripped of their enamel coating and electroplated. The areas of the two electrodes exposed outside the magnetic shielding material serve as solder joints.

[0019] Preferably, the magnetic core material of the inductor in step 1 is iron silicon chromium powder core, the initial magnetic permeability is 34-38, and the saturation magnetic flux density M s The inductor structure parameters are as follows: the copper wire cross-section width is 0.20-0.30mm, the copper wire window width is 0.060-0.080mm, the number of copper wire winding turns is 6-8 turns, the enamel film thickness is 0.01-0.02mm, the core length dimension is 0.60-0.80mm, and the core width dimension is 0.2-0.3mm.

[0020] Furthermore, the simulation software used in step 2 is COMSOL. In the COMSOL simulation software, the material type and properties of the magnetic core, copper wire, and enamel film of the three-dimensional simulation model of the inductor are set, the three-dimensional simulation model of the inductor is meshed and AC excitation is applied, and the research time and time step of the transient solver are set.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention provides an inductor noise optimization method based on multi-physics field simulation. This method uses COMSOL software to solve custom domain equations to calculate the coupling of the inductor's three electromagnetic forces: the Lorentz force, the Maxwell force, and the magnetostrictive force. These equations are then converted into electromagnetic forces in the frequency domain through Fourier transform and then simulated using a solid mechanics field. The magnetostrictive force generated by the electromagnetic field is coupled to the solid mechanics field in the form of strain. This method comprehensively accounts for the various electromagnetic forces acting on the inductor and performs solid mechanics and pressure acoustic field simulations in the frequency domain, significantly reducing simulation time and enabling accurate and efficient inductor noise simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flowchart of the inductor noise optimization method based on multi-physics simulation of the present invention;

[0024] Figure 2 Meshing for the 3D simulation model of the inductor;

[0025] Figure 3 This is the magnetic flux density simulation diagram of the inductor in the electromagnetic field simulation;

[0026] Figure 4 This is the acoustic pressure simulation diagram of the external field of the inductor in the pressure acoustic simulation;

[0027] Figure 5 3 is a comparison chart of the simulation output results and the actual test results of the embodiment. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings, specific embodiments and comparative examples. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the present invention is not limited to the following embodiments.

[0029] A method for optimizing inductor noise based on multi-physics simulation includes the following steps:

[0030] Step 1: Establish a three-dimensional simulation model of the inductor based on the actual size and material type of the inductor. The dimensional parameters of the inductor include the dimensional parameters of the core column and the magnetic shielding shell, the width and thickness of the copper coil, and the number of coil turns.

[0031] Detect the electromagnetic performance parameters of the inductor, including DC inductance, core permeability, core magnetostriction coefficient, BH curve, AC impedance and AC inductance, etc.;

[0032] Step 2: Assign electromagnetic properties to the inductor material using the electromagnetic performance parameters measured in Step 1, input a sinusoidal AC excitation to the inductor under normal working conditions (applying a sinusoidal AC current with a frequency of 1-3 MHz and a current of 1-1.25 A to the coil), perform a transient electromagnetic field simulation on the three-dimensional simulation model of the inductor, and calculate the transient electromagnetic force acting on the inductor under the AC excitation. The transient electromagnetic force includes the Maxwell force and magnetostrictive force acting on the magnetic core, and the Lorentz force acting on the copper coil;

[0033] Step 3. In the three-dimensional simulation model of the inductor, a boundary ordinary differential and a differential algebraic equation are customized for the boundary of the magnetic core to express the Maxwell force on the magnetic core described in step 2, a domain ordinary differential and a differential algebraic equation are customized for the domain where the coil is located to express the Lorentz force on the coil described in step 2, and a domain ordinary differential and a differential algebraic equation are customized for the domain where the magnetic core is located to express the magnetostrictive force on the magnetic core described in step 2;

[0034] Step 4: Perform a Fast Fourier Transform (FFT) on the transient electromagnetic force acting on the inductor to obtain the electromagnetic force in the frequency domain. Input the Young's modulus and Poisson's ratio of the core material, use the electromagnetic force in the frequency domain as the excitation source of the solid mechanics field, and calculate the surface displacement of the inductor according to the following formula. Then, calculate the surface acceleration of the inductor in the frequency domain.

[0035]

[0036] Where M is the mass matrix, C is the damping matrix, and D is the stiffness matrix. u is the node displacement, P(t) is the electromagnetic force on the inductor;

[0037] Step 5: Use the surface acceleration of the inductor in the frequency domain as the excitation source for pressure acoustics to simulate the external sound field of the inductor. Select the noise test point above the inductor surface as the microphone point and calculate the change of the sound pressure level at this point with frequency.

[0038] After connecting the inductor described in step 1 to AC power, place it in a silent box, and use noise testing equipment to test the sound pressure level at the noise test point. The measured data are compared with the data obtained by the above simulation to verify the reliability of the simulation method.

[0039] Example

[0040] like Figure 1 As shown in FIG, a method for optimizing inductor noise based on multi-physics simulation includes the following steps:

[0041] Step 1: Create a simplified three-dimensional inductor simulation model based on the actual size and material type of the inductor. The inductor's dimensional parameters include the core size, the width and thickness of the copper coil, and the number of turns. The core material's BH curve is used as the core material input property, and frequency-dependent electromagnetic properties are assigned to the core material in a magnetic field. In this embodiment, the inductor's normal operating state has a sinusoidal AC current of 1-1.25A and an operating frequency of 1-3MHz. The inductor's core structure consists of a core core and a core shell, with an inductance of 0.8-1.2μH, a DC resistance of less than 50mΩ, and an AC resistance of less than 100mΩ under operating conditions. The inductor is a one-piece inductor, consisting of an elliptical core, two layers of racetrack-shaped spiral coils wound around the core, and a magnetic shielding material covering the core and copper coils. The spiral coils have two leads that serve as electrodes. The electrodes are stripped of their enamel coating and electroplated. The areas of the two electrodes exposed outside the magnetic shielding material serve as solder joints. The core material is iron silicon chromium powder core, the initial magnetic permeability is 34-38, the saturation magnetic flux density M s The inductor structure parameters are as follows: the copper wire cross-section width is 0.20-0.30mm, the copper wire window width is 0.060-0.080mm, the number of copper wire winding turns is 6-8 turns, the enamel film thickness is 0.01-0.02mm, the core length dimension is 0.60-0.80mm, and the core width dimension is 0.2-0.3mm.

[0042] Step 2: Perform transient electromagnetic field simulation on the three-dimensional simulation model of the inductor to calculate the transient electromagnetic force on the inductor under AC excitation. The transient electromagnetic force includes the Maxwell force and magnetostrictive force on the magnetic core and the Lorentz force on the copper coil. In the embodiment:

[0043] (1) Mesh the physical model of the inductor in COMSOL, as follows: Figure 2 As shown, the magnetic core is divided into free tetrahedral meshes, the coil is divided into finer free tetrahedral meshes, and the air bag is divided into coarser meshes, which simplifies the calculation while ensuring the accuracy of the calculation.

[0044] (2) Set the material properties of the inductor core, copper wire, and enamel film in COMSOL, such as conductivity, magnetic permeability, density, etc.

[0045] (3) Apply a sinusoidal alternating current with a frequency of 1-3 MHz and a peak current of 1-1.25 A to the coil of the inductor model, with the cross section of any end of the copper coil as the input surface and the other side as the output surface;

[0046] (4) Set the research time and time step of the transient solver to calculate the excitation source of the structural field under AC operation. Set the research time to 0.0003s and the time step to 0.00000005s-0.0000001s. Add coil geometry analysis before the transient study of the magnetic field, and then calculate the transient field. The magnetic flux density simulation diagram in the electromagnetic field simulation when the inductor is running is as follows Figure 3 shown.

[0047] Step 3. In the 3D simulation model of the inductor:

[0048] (1) Customize the boundary ordinary differential and differential algebraic equations for the core to inherit the Maxwell force on the core described in step 2. The source terms of the expression are (a) Ffx-mf.nTx, (b) Ffy-mf.nTy, and (c) Ffz-mf.nTz.

[0049] (2) Customize the domain ordinary differential and differential algebraic equations for the domain where the coil is located to inherit the Lorentz force on the coil described in step 2. The source term input of the expression is (a) Fvx-mf.FLtzx, (b) Fvy-mf.FLtzy, (c) Fvz-mf.FLtzz;

[0050] (3) Customize the domain ordinary differential and differential algebraic equations for the domain where the core is located to inherit the magnetostrictive force on the core described in step 2; the source term input of its expression is:

[0051] (a)epx-1.5*mf.Mx*mf.Mx*Ys / Ms / Ms, (b)epy-1.5*mf.My*mf.My*Ys / Ms / Ms,

[0052] (c)epz-1.5*mf.Mz*mf.Mz*Ys / Ms / Ms, (d)epxy-1.5*mf.Mx*mf.My*Ys / Ms / Ms,

[0053] (e)epxz-1.5*mf.Mx*mf.Mz*Ys / Ms / Ms, (f)epyz-1.5*mf.My*mf.Mz*Ys / Ms / Ms.

[0054] Step 4: Perform a Fast Fourier Transform (FFT) on the transient electromagnetic force described in Step 3 to obtain the electromagnetic force in the frequency domain. The Young's modulus and Poisson's ratio of the core material are input, and the electromagnetic force in the frequency domain is used as the excitation source of the solid mechanics field to calculate the surface displacement of the inductor. The surface acceleration of the inductor in the frequency domain is then calculated. This process includes the following steps:

[0055] (1) Input the Young's modulus of the core material 2×10 11Pa and Poisson's ratio 0.4, density 7000kg / m 3 .

[0056] (2) Continue to use the simplified three-dimensional inductor model established in the electromagnetic field to divide the grid.

[0057] (3) Setting initial and boundary conditions: In this embodiment, the core is set to be a magnetostrictive material, the magnetostrictive model adopts nonlinear isotropic magnetoelastic properties, and the lower boundary of the core is set to a fixed constraint.

[0058] (4) The electromagnetic force in the frequency domain is used as the excitation source of the solid mechanics field through the generalized stretching operator, and the vibration displacement of the core surface is obtained by transient calculation of the structural field.

[0059] Step 5. Set the speed of sound in air to 340 m / s. Use the surface acceleration of the inductor in the frequency domain as the excitation source for pressure acoustics, simulate the external sound field of the inductor, and obtain the sound pressure diagram of the external field, as shown in the following figure: Figure 4 As shown in the figure, a position 10 mm to 50 mm above the origin of the three-dimensional inductor and 10 mm to 50 mm from the surface of the inductor is selected as the microphone point, and the sound pressure level at the microphone point is calculated as a function of frequency.

[0060] The inductor described in step 1 is connected to a sinusoidal alternating current with a frequency of 1-3 MHz and a peak current of 1-1.25 A and then placed in a silent box. The sound pressure level at the position corresponding to the microphone point in the simulation model is tested using a noise test device. The processed measured data is compared with the simulation data, as shown in FIG. Figure 5 As shown in the figure, the error between the measured data and the simulated data of the sound power level at the peak is less than 8.0%, which verifies the reliability of the simulation method.

[0061] Compared with the existing technology, the beneficial effects of the inductor noise simulation method based on COMSOL's multi-physics field simulation are as follows: based on the finite element method, electromagnetics, structural mechanics and acoustic theory, the COMSOL software is used to customize the solution domain equation to calculate the coupling of the three electromagnetic forces of the inductor, namely the Lorentz force, Maxwell force, and magnetostriction force, and transform them into electromagnetic forces in the frequency domain through Fourier transformation and perform solid mechanics field simulation, wherein the magnetostriction generated by the electromagnetic field is coupled to the solid mechanics field in the form of strain. This method can comprehensively take into account the various electromagnetic forces to which the inductor is subjected, and simulating the solid mechanics field and pressure acoustic field in the frequency domain can greatly reduce the simulation time, thereby completing the noise simulation of the inductor accurately and efficiently. Combined with experimental verification, it shows that this method is more accurate and the simulation time is greatly reduced.

[0062] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. Those skilled in the art will recognize that several equivalent substitutions or obvious variations can be made without departing from the scope of the present invention, and that any equivalent performance or application should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for optimizing inductor noise based on multi-physics simulation, characterized in that: The following steps are involved: Step 1: Establish a three-dimensional simulation model of the inductor based on the actual size and material of the inductor; and detect the electromagnetic performance parameters of the inductor; Step 2: Assign electromagnetic properties to the inductor material based on the electromagnetic performance parameters measured in step 1, then perform magnetic field simulation on the three-dimensional simulation model of the inductor, input a sinusoidal AC excitation to the inductor under normal working conditions, and obtain the transient electromagnetic force on the inductor under the AC excitation. The transient electromagnetic force includes the Maxwell force and magnetostrictive force on the magnetic core, and the Lorentz force on the copper coil; Step 3: Perform a fast Fourier transform (FFT) on the transient electromagnetic force on the inductor to obtain the electromagnetic force in the frequency domain; then, use the electromagnetic force in the frequency domain as the excitation source of the solid mechanics field to calculate the surface displacement of the inductor, and then calculate the surface acceleration of the inductor in the frequency domain; Step 4: Use the surface acceleration of the inductor in the frequency domain as the excitation source for pressure acoustics to simulate the external sound field of the inductor. Select the noise test point above the inductor surface as the microphone point and calculate the change of the sound pressure level at this point with frequency.

2. The inductor noise optimization method based on multi-physics field simulation according to claim 1, characterized in that: In step 1, the dimensional parameters of the inductor include the dimensional parameters of the core center column and the magnetic shielding shell, the width and thickness of the copper coil, and the number of coil turns; the electromagnetic performance parameters include DC inductance, core magnetic permeability, magnetostriction coefficient of the core, BH curve, AC impedance, and AC inductance.

3. The inductor noise optimization method based on multi-physics field simulation according to claim 1, characterized in that: The actual size of the inductor described in step 1 should meet the design objectives of the inductor, which include the voltage and operating frequency, package size, inductance, DC resistance, and AC resistance of the inductor under normal operating conditions.

4. The inductor noise optimization method based on multi-physics field simulation according to claim 3, characterized in that: The inductor design goals for Step 1 are: a sinusoidal AC current of 1-1.25A and an operating frequency of 1-3MHz under normal operating conditions; the inductor's magnetic core structure consists of a core center column and a core shell, with an inductance of 0.8-1.2μH, a DC resistance of less than 40mΩ, and an AC resistance of less than 100mΩ under operating conditions; the inductor is a one-piece molded inductor, consisting of an elliptical core center column, two layers of racetrack-shaped spiral coils wound around the core, and a magnetic shielding material covering the core and copper coils.

5. The inductor noise optimization method based on multi-physics field simulation according to claim 4, characterized in that: The core material of the inductor in step 1 is iron silicon chromium powder core, with an initial magnetic permeability of 34-38 and a saturation magnetic flux density M s 1.5-2.0T.

6. The inductor noise optimization method based on multi-physics field simulation according to claim 4, characterized in that: Inductor structural parameters: copper wire cross-sectional width is 0.20-0.30mm, copper wire window width is 0.060-0.080mm, copper wire winding turns are 6-8 turns, enamel film thickness is 0.01-0.02mm, core length dimension is 0.60-0.80mm, core width dimension is 0.2-0.3mm.

7. The inductor noise optimization method based on multi-physics field simulation according to claim 1, characterized in that: The simulation software used in step 2 is COMSOL. In the COMSOL simulation software, the material type and properties of the magnetic core, copper wire, and enamel film of the three-dimensional simulation model of the inductor are set, the three-dimensional simulation model of the inductor is meshed and AC excitation is applied, and the research time and time step of the transient solver are set.

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