DC/DC Converter Module Implementation And Process Design

In recent years,various smartphones,tablet PCs,laptops and other portable electronic devices are constantly being updated.Due to the miniaturisation and lightweighting of electronic components and the multi-functionality of internal components of electronic products,many electronic products are thin and light,thus attracting a large number of users to buy and use them.The power supply system is an essential part of all kinds of electronic equipment,and its performance determines the efficiency of the electronic equipment as well as supplying energy to the equipment.In order to meet the current requirements of highly integrated electronic devices,the miniaturisation of power supply modules has become an issue that cannot be ignored.Generally speaking in conventional switching DC/DC converters,surface-mounted magnetic devices take up most of the area,especially inductors.LTCC technology offers the advantages of miniaturisation,design flexibility,low cost and high integration.By using LTCC technology to embed inductors inside the LTCC substrate,the size of the inductor in the DC/DC converter module can be significantly reduced,facilitating the miniaturisation of the power supply system.Generally speaking,inductors are large in size in circuits.In order to design an inductor with good performance and small size,when using LTCC technology for DC/DC converter substrates,the performance of the magnetic material of the inductor LTCC substrate is taken into account,and an inductor is chosen to be independently developed to fit this DC/DC converter circuit itself,with a corresponding magnetic permeability and able to match the silver electrode（961°C）for co-fired,and to maintain good performance below 10 MHz.Ni Cu Zn ferrite has a low sintering temperature and can be used for low temperature co-firing of electronic components.Firstly,the effect of Bi₂O₃ doping at low concentration on the microstructure and electromagnetic properties of Ni Cu Zn ferrite materials under different temperature conditions was investigated,and then a quantitative amount of Bi₂O₃（0.3 wt%）was chosen to compound doping of Ni Cu Zn ferrite using Mo₂O₃,Co₂O₃ and V₂O₅ dopants to further investigate the microstructure and electromagnetic properties of the materials under different temperature conditions.Finally,a quantitative amount of Bi₂O₃（0.25 wt%）was selected and different amounts of Sb₂O₃ were added as dopants for the low temperature sintering of Ni Cu Zn ferrite at900°C.The effects of Sb₂O₃ on its phase composition,microstructure and electromagnetic properties（dielectric loss tanδε,permeabilityμ’and cut-off frequency fr）were systematically investigated.A Ni Cu Zn ferrite material with a permeability ofμ’=63 and a cut-off frequency fr=134 MHz was finally obtained.These excellent parameters not only meet the design specifications of the LTCC embedded inductor substrate material in this thesis,but also expected to be a candidate material for the fabrication of high frequency electronic components.The aim of this thesis is to design and simulate a DC/DC converter based on low temperature co-fired ceramic（LTCC）technology and firstly to analyse how to miniaturise the power supply based on the circuit operating principle of the DC/DC converter.In switching power supplies,there are Buck-type DC/DC converters as well as Boost-type converters respectively.Altium Designer 20 software was used to draw the peripheral circuits of the Buck DC/DC converter and the Boost DC/DC converter,to obtain the corresponding PCB layout and to make circuit boards,to complete the soldering of the peripheral circuits and to carry out the corresponding tests.The two DC/DC converter circuits were optimised and simulated to produce two PCBs,both measuring 3 mm×3mm.The input voltage of the Buck DC/DC converter is 3-5.75 V and the output voltage is 3 V.The input voltage of the Boost DC/DC converter is 0.8-3.7 V and the output voltage is 5 V.The operating frequency of the switches is 2.4 MHz.Finally,according to the LTCC process design guidelines,HFSS 15.0 and Maxwell software were used to simulate and design the LTCC embedded inductor substrate,adding the characteristics of the new self-developed Ni Cu Zn ferrite material to obtain two types of LTCC embedded inductor substrates with dimensions of 3 mm×3 mm×1.6 mm,the actual inductance was 0.43μH and 2.29μH and the maximum operating current is 1 A.