Abstract

This paper presents a multi-channel phase-shift LLC resonant converter that was specially optimized for fuel-cell applications and has a wide input and output voltage range. The worst-case minimum stack voltage and the battery voltage range were used to find the optimal parameters of the LLC converter. The voltage gain of the converter operating at a constant power was considered, and the algorithm for such a calculation was proposed. Current balancing was implemented using channel temperature measurements instead of expensive current measurements. A natural self-balancing mechanism was investigated for converters operating at high frequencies above the series resonance of a resonant converter. Recommendations for the converter's transformer turn ratio were illustrated for efficiency optimization. The multi-object optimization is implemented to reach the optimized design so the minimum and maximum voltage gains can be reached and, at the same time, the transformer turn ratio is kept at the minimum to reach high efficiency. An experimental prototype of a four-channel converter was presented and tested at a 5 kW power level. Active content and C-language code files for converter calculations are provided as well with this work.