LLC charger using matrix core coupling for power transfer to electric vehicle

An LLC charger for Level-one electric vehicle charger is proposed using matrix core transformer (MCT) to power transfer through resonant magnetic-induction coupling (RMIC). The MCT consists of multiple low-cost ferrite cores, which is used to distribute the input power in multiple primary windings of the sub-transformers and share the output current in multiple secondary windings. A less-than-one turns-ratio in MCT is explored, which can reduce the magnetizing current and core loss, and improve the charging ability for high-voltage battery pack by increasing ampere-turns in the secondary winding. Particularly, the LLC charger can provide desired current for a current source by simply tuning the operation frequency. Besides, a transconductance G_m(jω) response instead of the usual voltage gain G_v(jω) response is revealed that can depict the LLC load trace continuously throughout Region 1 and Region 2 without interruption. The modeling of the MCT transformer is conducted in detail for describing the system and power transfer behavior. A scale-down 600-W LLC charger is designed and experimented to assess the charging behavior and the self-regulation ability that stabilizes the state of charging.