Comprehensive Mode Analysis and Optimal Design Methodology of a Bidirectional CLLC Resonant Converter for E-Vehicles Applications

CLLC resonant converters are suitable for bidirectional power conversion applications, which demand small volume and high-power efficiency, such as on-board power supply systems for electric vehicles. Aside from its conventional topology, a modified CLLC resonant converter is here evaluated. A second low voltage bridge is added to the original circuit, so that the topology now works with two transformers, being connected in series on the high voltage side and in parallel on the low voltage side. Although the higher number of components, it is expected to achieve a design with higher efficiency, compactness and lower filter requirements. Due to the low accuracy of the first harmonic approximation when the proposed converter operates outside the series resonant frequency, this paper presents a detailed operation mode analysis for the bidirectional CLLC resonant converter in the time domain.