Virginia Polytechnic Institute and State University
This work presents the design and optimization of a PCB-based matrix transformer with integrated controllable leakage inductance for an 11 kW, 250 kHz bidirectional DC/DC CLLC resonant converter. To improve modeling, non-air-gapped core legs are incorporated into the reluctance model, and an x-direction extension parameter is introduced to enable reluctance variation while minimizing peak flux density for 3UI-based transformers. At 11kW, a 2UI-based matrix transformer is shown to achieve superior flux distribution and lower losses over a 3UI-based matrix transformer under the same footprint. Furthermore, a novel Circular Orthogonal Parallel (C.O.P) core structure is proposed, positioning airgaps above PCB traces to mitigate current crowding found in Traditional Parallel (T.P) core structures. Experimental validation on an SiC-based prototype shows a peak efficiency of 98.3% for the C.O.P core structure versus 97.9% for T.P core structure, both achieving all gain requirements and confirming the C.O.P design's advantage in the application of high-density matrix transformers.
