This paper addresses the analysis and optimization techniques for the magnetics employed in a 2 MHz, 12V / 600mA, GaN-based Active-Clamped Isolated SEPIC Converter (ACISC) supporting full ZVS throughout the 9V-18V automotive range and intended to provide isolation and power interface between the 12V battery and the low-power subnet. Since the low-power isolated converter leverages the high switching frequency enabled by GaN devices, it is crucial to create ad-hoc PCBs for the planar transformer with the aim of reducing both its main largest loss contribution and the inter-winding capacitance which is a critical parasitic capacitance of the converter in the common mode (CM) noise perspective. The basics of the proposed design procedure for the realization of different efficient high-frequency planar transformers are highlighted, along with preliminary experimental results, focusing on reducing both the ac winding resistance and the inter-winding capacitance.
