Research And Application Of High Frequency Low Power Loss NiCuZn Ferrites

In modern industrial society,the demand for electronic devices is expanding,and small,efficient power supplies are becoming the mainstream of the market.However,magnetic components occupy the largest space size inside a small power supply module,so how to reduce the size of this module is one of the most important tasks today.By using the low temperature co-fired ceramic（LTCC）process,passive devices can be embedded inside a ferrite substrate to miniaturize power supplies,which provides a new solution for the future development of power devices while making them more reliable and less costly.The purpose of this thesis is to investigate the performance requirements of DC-DC converters and to investigate the preparation of a series of corresponding low power loss（Pcv）NiCuZn ferrite materials.Based on a fixed master formulation of Ni_0.325Zn_0.4Cu_0.275Fe_1.98O₄ and 0.25 wt%content of Bi₂O₃,we try to dope oxides such as Mn O₂,WO₃,and Co₂O₃ to reduce the power loss.The results show that all three oxides have different improvement effects on the power loss characteristics,but on the whole,Co₂O₃ has the best doping effect（52.9k W/m³,5MHz/10m T,25℃）.In the formulation with doping amount of 0.3 wt%Co₂O₃,we chose different contents of V₂O₅ for doping and firing aid,but we found that the doping effect of V₂O₅ was not satisfactory,and the permeability of its samples was only 50-60,and its effect of reducing loss was poor.Subsequently,we tried to compound doping Mn O₂ oxide with 0.25 wt%Bi₂O₃ and 0.3wt%Co₂O₃ in the main formulation of Ni_0.325Zn_0.4Cu_0.275Fe_1.98O₄ and found that the permeability of the material improved to 150 and the Pcv decreased again（40.8k W/m3,5MHz/10m T,25°C）.Finally,we determined the best formulation of the magnetic material and performed the design and simulation of the DC-DC converter to obtain a step-down regulated-conversion DC-DC converter,which successfully varies the input voltage from 3.6v-5v to 2V with a voltage ripple coefficient less than 1%.In addition,we also designed the LTCC planar power inductor in it using this material.