LLC Resonant Converter Utilizing Parallel-Series Transformers Connection

This paper presents a single-phase full bridge LLC resonant converter which utilizes parallel-series connected transformers. This converter can be used in onboard battery charger of electric vehicle. This circuit achieves zero turn on voltage switching (ZVS) of power switches as well as zero turn off current switching (ZCS) of rectifier diodes. In order to have a better heat dissipation, the large single transformer of conventional converter have been substituted with two equal transformers. Furthermore, a more compact structure is resulted. Additionally, parallel connection of transformers in the primary side reduces the turns of primary windings which leads to decrease the Joule loss of coils in high power applications. The principle of operation, steady state analysis and the design procedure of proposed converter have been described in detail. Finally, simulation results have been presented to verify the effectiveness of the proposed converter. The results show higher efficiency, lower output voltage ripple and better space utilization.