Split Planar Transformer based Auxiliary Power Supply for High Voltage Isolation

This paper presents the design of an ultra-low power Series Resonant Converter-based auxiliary power supply for a sensing application with high isolation requirements. A split planar high-frequency transformer design is utilized to achieve a high isolation voltage of $25 \mathrm{kV}_{\text {pk }}$. High isolation requirements are met by physically isolating the primary and secondary PCB-based coils and using a resin to encapsulate the entire transformer. The converter is switched at 400 kHz. The design considerations for the converter and that for the split planar transformer are presented. Finite element electrostatic and magnetostatic simulations have been performed to validate the analytical models. A hardware prototype is developed, and hardware-based experimental results are provided to validate the converter operation. High potential $\left(25 \mathrm{kV}_{\mathrm{pk}}\right)$ tests have been performed on the prototype for 60 s, and the high isolation capability of the designed split planar transformer has been verified.