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Design Optimization of PCB-Winding Matrix Transformer for 400V/12V Unregulated LLC Converter

Isolated high-output-current DC/DC converters are critical technologies for future datacenter power architecture. LLC converters with matrix transformers are suitable for these applications due to their high efficiency and high power density. Previously, The Center for Power Electronics Systems (CPES) proposed a PCB-winding based matrix transformer for a 400V/12V 1MHz unregulated LLC converter. This paper aims to further improve the efficiency of the converter, without compromising on the power density, by optimizing the switching frequency of the converter, and mitigating the current sharing issues associated with center-tap rectifiers and shielding in matrix transformers with multiple outputs. The elimination of these issues is critical because they can lead to non-uniform increases in device temperatures and a reduction in the overall efficiency of the converter. The proposed improvements are verified by developing a 1 kW prototype with a peak efficiency of 98.05% and a power density of 940 W/in3