Tiny Power Box: Part 2 - System Design for a High Density Isolated Bidirectional OBC with Integrated DCDC

Referent: Ismail Recepi, Research Engineer, Silicon Austria Labs

This paper presents an 11 kW three-phase On-Board Charger (OBC) integrating a 4.2 kW HV/LV DC–DC converter. It features galvanic isolation for safety, bidirectional power transfer, and compatibility with single- and three-phase inputs. Liquid-cooled thermal management and optimized component layout enable ~4 kW/L power density (including housing). The HV/LV stage delivers 300 A @ 14 V using an ultra-wide-range LLC with a novel quarter-turn core, achieving compact multifunctional EV integration.