High Power Density Three-Phase LLC DC/DC Converter with Coupled Resonant Inductor and Wye-Delta Transformer for Aircraft Applications

In applications with a high step-down voltage as in aircraft applications, finding a topology able to achieve high power density and high efficiency while begin EMI-friendly is crucial. Gallium Nitride devices enable high frequency switching, allowing the shrinkage of the magnetic components. The drawback however is the lower efficiency due to switching losses and electromagnetic interference constraints. The focus of this research work is the evaluation of a Three-Phase LLC converter, which, due to its inherent step-down nature (wye-delta transformer), integration capability, low input and output current ripple and high efficiency (ZVS on the entire load conditions), may be a promising solution for a high power density and modular DC/DC converter. Specifications in avionics are very challenging and include a wide input voltage range (235–300 V), a large step-down to the fully controlled 28 V in a half-brick form factor (47 cm3) for a nominal output power of 1 kW leading to a power density of 20 kW/L.