Bias-resistant Low Temperature Sintered Ferrite Material And Its Application In Chip Power Supply

In recent years,the rapid development of the electronic information industry has promoted the development of various electronic devices toward miniaturization,portability,and multifunction.Power supply systems,as an integral part of electronic equipment,also follow this trend.As an indispensable component in the power supply system,the inductive device occupies a large space in the entire circuit,which limits the miniaturization design of the switching power supply.With the maturity of low temperature co-fired ceramic?LTCC?process technology,inductors can be integrated with other magnetic devices in the same substrate by stacking.However,at the same time of miniaturization,the inductance device also needs to meet the stability and reliability of maintaining the inductance value under the condition of applying a large bias current.Meeting the above goals can be accomplished by changing the way of the inductor base material and inductor structure.Therefore,the main work of this thesis is to prepare ferrite materials with good resistance to DC bias for the design of laminated chip inductor substrates to achieve the miniaturization design of switching power supply systems.In the first part of the thesis,we studied the differences between NiCuZn ferrite and MgCuZn ferrite under low Bi₂O₃ doping and high Bi₂O₃ doping.The comparison results show that under low Bi₂O₃ doping,NiCuZn ferrite has higher saturation magnetic induction B_s,MgCuZn ferrite has higher coercive force H_c and better DC-bias superposition.In the case of high Bi₂O₃ doping,NiCuZn ferrite still has a higher saturation magnetic induction B_s,and has better resistance to DC bias than MgCuZn ferrite.And the comparison of Curie temperature of the materials of the two systems in both cases shows that NiCuZn ferrites perform better.In combination with the application of material design,NiCuZn ferrite was selected as the main material system.Then,the influence of MgO doping on the magnetic properties of low-temperature sintered NiCuZn ferrites,especially DC-bias superposition,was investigated.The study found that the doping of MgO did not introduce heterophase and did not significantly change the grain size of the sample,but it had a significant effect on the material's magnetic permeability,B_s,H_c and DC-bias superposition.When the MgO material was doped at 2.5 wt%,the corresponding initial magnetic permeability was 70,and H_70%was 846 A/m.For the design of the switching power supply circuit,this paper selects the TPS62090 chip as the switching control chip for the power system.By understanding the theoretical knowledge of its BUCK topology and its peripheral circuits,the design of the entire DC-DC converter circuit was completed.In order to verify the design,Feasibility.This article used orCAD capture software to simulate its design.Finally,a circuit design with an input voltage of 3.8-5 V and an output of 3.6 V and a ripple of less than 100 mV is obtained.Then based on the characteristics of the LTCC process,the magnetic inductance device in the circuit is designed and simulated,and the NiCuZn ferrite parameters doped with 2.5 wt%MgO are input to Anosft Maxwel software for simulation.A multilayer chip inductor substrate with a rated current of 5.2 A was obtained,which meets the circuit design index of 3 A.Finally,the design steps of the chip power supply substrate are introduced.