Integrated Inductor-Transformer Design Using a Concentric Pillar Structure - PlanarTrans 800V/54V

Isolated DC-DC converters intentionally require a certain amount of leakage inductance to regulate power flow and enable soft-switching operation. This work presents a concentric pillar-based integrated inductor-transformer design that provides a controlled leakage flux path between transformer windings. The proposed magnetic structure is applicable to dual-port and multiport transformer configurations. The integrated inductor-transformer employs two sets of inner pillars, where the primary winding is wound around both sets of pillars, while the secondary winding is wound only around the central pillar. Consequently, the pillars linked exclusively by the primary winding establish a controlled leakage flux path, allowing the leakage inductance to be precisely tailored. The proposed design achieves high leakage inductance, making it suitable for soft-switching converter applications. Furthermore, the proposed structure is highly manufacturable, requiring only two core pieces and a single printed circuit board (PCB) for integrating the windings and converter circuitry. A prototype was developed with target magnetizing and leakage inductances of 260 μH and 60 μH, respectively, and achieved measured values of 214 μH and 59 μH.