High frequency dc/dc power converter with galvanic isolation

• Main Authors: Van Der Kogel, André, Österlund, Niklas
• Format: Others
• Language: English
• Published: Linköpings universitet, Fysik och elektroteknik 2016
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-128831

There is a steady demand to increase the efficiency and raise the power density of power converters. This trend is desired since it leads to reduced size of the converter. The purpose of this thesis is to investigate materials, topologies, core structure and then build a prototype to demonstrate the result. Two core materials have been compared, Fair-Rite material 68 and Ferroxcube 4F1. The goal was to have 50 V input and 30 V output with 80 % efficiency of the converter. The converter with the Fair-Rite material 68 accomplished a peak efficiency at 11 MHz with 54 % efficiency. The core material Ferroxcube 4F1, reached an efficiency of 52 % at 7 MHz. These results were however with 5 V input and 3 V output. The converter had a low efficiency at 50 V input, which lead to ripple in the circuit. One reason for this behaviour was because the design of the PCB was not optimized for MHz operation. The focus of the PCB was that it should be easy to work with instead of achieving peak performance. Also, from the beginning it was decided that no PCB should be made. The focus was instead on the theory and simulations of the converter so no thoroughly investigation of PCB design was done. The leakage inductance of the transformer core was about 10 % of the primary inductance for both materials. The high leakage inductance is believed to further reduce the efficiency of the converter.