High-Gain High-Frequency Three-Phase LLC Resonant Converter Design Based on the Wye-Delta Transformer for Aircraft Applications

The requirements for small form-factor power supplies drive the need for high-frequency small magnetic components and high efficiency to obtain thermal stability. When combined with high output power, magnetic optimization becomes crucial in the pushing of the boundaries of magnetic shrinkage. Among those applications in need of power dense systems, aircraft is considered one of the most restrictive due to its ultrahigh reliability and miniaturization in both volume and mass. On-board equipment transfers the responsability to the power stage classifying it as mission-critical. The selection of a multiphase converter enables the desired magnetic components' shrinkage. With these objectives in mind, a three-phase $LLC$ based on the wye-delta transformer is selected as a promising topology to fulfill high efficiency, small form factor, effective power density, and high voltage step-down in aircraft applications. The focus of this work is the listing of the guidelines on the design of three-phase magnetic components with the compensation of an asymmetric structure (EE/EI cores) to match its magnetic coupling. The multiple sources of power losses are analyzed and optimized, including high-amplitude high-frequency currents traveling around the printed circuit board. This article presents the design of a unidirectional dc-dc converter with an input voltage range of 235-285 V to 28 V at the output, controlled by a frequency range of 15% for a nominal output power of 1 kW reaching an efficiency of 96%.