Development and Optimization of a Phase-Shifted Full-Bridge Converter

Abstract

Abstract Power electronic converters have become an essential part of modern-day electronics. Switching converters dominate the industry, with switching speeds going up while physical dimensions are shrinking. Out of all available converter topologies, the phase-shifted full-bridge converter has emerged as a promising option when dealing with higher power levels, partly due to its ability to perform zero voltage switching to increase efficiency. This thesis explores the development of such a converter at a power level of 500 W, with a focus on small form factor and the use of discrete components to ensure full design freedom. In order to decrease the size of the magnetics the switching frequency has been greatly increased. The magnetics includes the transformer, which has been constructed as a planar transformer to better suit the high frequency operation of the converter and enable good thermal management. After designing the converter and sourcing components, the converter was assembled and put through a series of tests. Full output power was achieved at a total system efficiency of 90 %, while maximum regulated output power reached 300W due to instability in the control loop. The transformer worked and proved the possibility to decrease total converter size, but parasitics caused ringing which ended up thermally limiting the converter. A thermal model of the converter and mainly the transformer was implemented and used successfully to predict real-life temperature under load.