Research On Double-resonant DC/DC Converter System

With the development of science and technology,the aerospace industry has developed and progressed where the spacecrafts play an important role.Due to the increasing types and quantities of electronic equipment along with the power supply requirement of the communication and scientific research equipments,the solar aircraft power supply system has become one of the research hots in spacecraft energy system as the photovoltaic energy is in touch and inexhaustible.Traditional resonant DC/DC converters are used in photovoltaic applications with a wide input range,which have the defects of wide frequency range,low efficiency and low power density.To solve the above-mentioned problems,a fully resonant DC/DC converter ystem is proposed in this thesis.The proposed system adopts the structure with two-stage resonant converter.The primary-stage is the non-isolated LCLC resonant converter with Pulse Frequency Modulation(PFM).The variable excitation inductance is introduced realize the buck-boost conversion and extend the gain range while improve the system efficiency under high-voltage input.The latter-stage adpots a CLL direct current transformer(DCX)that can keep operating at the resonance point to maintain the optimal efficiency operation,for the output voltage under changeable latter-stage loads could be stabilized by adjusting the operating frequency of primary-stage converter.In addition,both the primary and latter stages can achieve the soft switching,which means the Zero Voltage Switch(ZVS)of primary switches and the Zero Current Switch(ZCS)of secondary switches and rectifier diodes.In this thesis,the beginning starts with the analysis of non-isolated LCLC resonant converter based on the analysis and design of the front-stage non-isolated LCLC resonant converters.The voltage gain characteristic is analyzed by fundamental equivalent method and detailed research of parallel branch characteristic,dead time and soft switching condition are provided.A prototype with36V-110 VDC input and 100VDC/200 W output is designed for latter experimental verification.Afterwards,the proposed fully resonant DC/DC converter is researched.The optimal bus voltage is firstly selected through the analysis of efficiency optimization considering the different characteristics of two stages,and the analysis of latter CLL-DCX converter is carried out along with the synchronous rectification technology and planar transformer technology.After the simulation of system,a prototype with 36V-110 VDC input and 12VDC/200 W output is designed for experimental verification.