Very High Frequency Resonant DC-DC Power Converter

The development of power electronics is demanding for the converting systems with high powerdensity. Increasing the switching frequency is an effective way to reduce the energy storage requirementsof the capacitors and the magnetic components, shrink the size and weight of the passive components andincrease the power density of the converter. Under this background, this thesis carries out a research onthe Very High Frequency (VHF,30MHz~300MHz) DC-DC power converters. Paper studies mainlyincludes following aspects: structural features, operating principles and design methods of the maincircuit. Besides, this thesis also makes research on the drive circuits and the control strategies.Experimental prototypes are built to verify the theoretical analysis.This thesis starts with the research on the single-switched VHF resonant Boost converter andgives the introduction and analysis of the operating principles and characteristics of the basic VHFDC-DC converters. So that the difference between VHF converters and traditional power converterscan be figured out as well as the design considerations. Then according to the characteristics of theVHF converter, the research on drive circuits and control strategies is carried out. An experimentalprototype is built to verify the validity of the conclusion and design methods summarized above. It isfound that most of the previous work on the VHF DC-DC converters focuses on the non-isolatedtopologies with the low power level. To change this situation, an isolated push-pull VHF resonant converteris proposed based on the above wrok. The benefits are summarized:1) the power isolation and extension ofthe power level can be achieved;2) Zero-Voltage-Switching (ZVS) for the main MOSFET with lowvoltage stress;3) Zero-Current-Switching (ZCS) of the rectifier diode;4) the ability to absorb parasiticparameters. The detailed analysis and design procedure are also given. Finally, an experimental prototypeis developed to desmonstrate the above merits.Two VHF converter prototypes are developed. The first desing is a30MHz/15W Boostresonant converter with15V input and30V output voltage. While the second design is a30MHz/50W isolated Push-Pull converter with36V input and24V output voltage. The experimental results areconsistent with the theory analysis and the simulation results which demonstrate the functionality ofthe VHF converter and effectiveness of the design method. The efficiency of the VHF Boost prototypeis72.3%and the VHF Push-Pull prototype73.4%at full load. The future work is to optimize theefficiency of the converter.