High-Frequency Integrated Magnetics Design for Onboard LLC Converter Utilizing 4-Layer PCB

In modern aircraft, High power step-down converters from 270V to 28V are in high demand. Matrix transformers used in these converters are desirable but challenging due to the special ratio. In this work, a matrix transformer used in 270/28V LLC converters is demonstrated, which leverages the well-established benefit in high output current conditions. To minimize the termination loss, the transformer used a 4-layer PCB structure with two layers for secondary-side winding and another two layers for primary-side planar-Litz winding. PCB stack-up and winding structure are discussed in order to equalize each secondary side output. A prototype of 270/28V LLC converter for aircraft application is built to verify the proposed design.