An improved transformer-grid inductor magnetic integration for single-stage on-board charger

This article proposes an improved integrated magnetic structure for the single-stage interleaved totem-pole AC-DC converter, which is applicable for on-board chargers (OBCs). The grid inductors are integrated into the high-frequency transformer, which eliminates the core and winding of grid inductors. This results in a reduction in the magnetic loss, core material volume, and total volume. The analytical comparison among three core candidates to implement the integrated magnetic structure is discussed. The four-leg integrated magnetic, whose total volume is 11% smaller than that of the prior art integration, is selected for further design. An optimized design based on the Figure of Merit (FoM) method is carried out to design the proposed magnetic. A single-phase 3.7kW single-stage OBC prototype with both discrete and integrated magnetic structures is assembled and tested. Compared to the discrete structure, the converter efficiency with the integrated one is 1% higher at light load, and 0.1% higher at full load. In addition, the integrated magnetic volume is 35% smaller than the discrete one. The designed module achieves 97.3% peak efficiency.