The Design Of Low Frequency Wireless Power Transfer Coils And Wideband Low Frequency Inductors Using The Mixed Finite-Element Time-Domain Method

In computational electromagnetics,the low-frequency electrical small model refers to a model whose model size is much smaller than its wavelength,and it is widely found in various electronic designs,such as wireless power transfer coils and inductors.Between them,the inductor is widely used in various circuit designs.At present,the traditional electromagnetic simulator has the phenomenon of low frequency breakdown when simulating low frequency electrically small models.For example,when the frequency is low,the system matrix condition number of the traditional method is very large,indicating that the matrix is serious abnormality.This causes the calculation efficiency of traditional methods to be low,and the calculation results are often inaccurate or non-convergent.Therefore,the application of a method capable for overcoming low-frequency breakdown to simulate the design of low-frequency electrically small models such as inductors and wireless power transfer coils is of great significance.Computational electromagnetic methods are divided into frequency domain methods and time domain methods.Between them,the time domain method only needs to go through one simulation,and transform the results by Fourier,so as to obtain broadband simulation results,which is an effective method for broadband design.The most widely used time-domain methods for computational electromagnetics are the finite-difference time-domain method(FDTD)and the finite-element time-domain method(FETD).Since the finite difference time domain method(FDTD)uses a hexahedral mesh,the mesh density will be very large when the model surface is curved.The time domain finite element method uses a flexible tetrahedral mesh to divide the object,which can obtain a more accurate and simplified mesh model than the hexahedral mesh.In this work,we apply a recently developed mixed finite-element time-domain(mixed FETD)method to overcome such low-frequency breakdown difficulties in designing wireless power transfer coils and inductors.This method considers the divergence constraints of the electric field,improves the abnormal-condition of the system matrix,and makes the solution of the results faster and more stable.First,we design a WPT system with low frequency and high transmission efficiency.We explore the effect of different loads on the transmission efficiency of the system.Secondly,the mixed FETD is applied to the extraction of inductance parameters of inductors under broadband,and the change of inductance value from low frequency to high frequency is explored.