High-efficiency high-power-density 48/1V sigma converter voltage regulator module

A high efficiency and high power density sigma converter for 48/1V voltage regulator module (VRM) is proposed in this paper. The Sigma converter is a quasi-parallel converter that uses a high efficiency unregulated converter to deliver most power to the load with small power flowing through buck converter responsible for regulating the output voltage. The unregulated isolated converter is LLC converter designed with matrix transformer structure integrating 4 transformers in one core structure with integrating the Synchronous Rectifiers (SRs) with the winding to minimize the termination losses of the transformer so a high efficiency can be achieved. The buck converter is designed with discrete GaN devices and PCB winding inductor to regulate the output voltage. The designed Sigma converter is 48/1V-80A achieving a power density of 420W/in³ and maximum efficiency of 93.4%.