Low-Profile and High-Efficiency 3 kW 400 V-48 V LLC Converter with a Matrix of Four Transformers and Inductors for 48V Power Architecture for Data Centers

Power consumption of data centers has increased rapidly over recent years. Of late, 48 V power architecture has attracted more interest in data centers as it offers more efficient architecture. This paper focuses on the implementation of the DC-DC stage of the power supply unit for narrow range 48 V datacenter bus architecture. The paper presents a nearly 99% efficient 400 V-48 V LLC with a very high power density and low profile fully integrated on PCB. The LLC topology is chosen as it can achieve soft-switching, allowing one to push the switching frequency and increase the power density. A matrix of four transformers is used to reduce the termination loss of the secondary synchronous rectifier and achieve better thermal management. The number of secondary turns is optimized to achieve the best trade-off between winding loss, core loss, and power density. A matrix of four resonant inductors is also designed to reduce the proximity effect between inductor windings and reduce inductor PCB winding loss. The converter integrates a matrix of four transformers and resonant inductors on a 6-layer PCB and single-core for easier manufacturability and lower cost. A prototype is tested for the proposed converter at 250 kHz with 98.8% efficiency and 600 W/in3 power density with an 11 mm profile.