High Power Density 48–12 V DCX With 3-D PCB Winding Transformer

Planar transformer has been used in high frequency high power density dc–dc converters for its low profile. With the packaging technology development of the power devices, their footprints become smaller and smaller. However, the reduction in the core loss density of high frequency soft ferrite materials is slow, which results in an insensible reduction of the cross area of the transformer magnetic core. Hence, the transformer becomes the highest component in many high-density brick dc–dc converters, which restrict the improvement of power density. This letter proposes a three-dimensional (3-D) PCB winding structure, which surrounds the flat magnetic core. By mounting the components to the top and bottom layers of PCB windings, the transformer volume is reduced and the power density can be improved significantly. A 1.6 MHz 48–12 V 300 W DCX prototype with GaN device is built up to verify the 3-D PCB winding concept. The peak efficiency 97.3% and power density 1380 W/in
³
are achieved by using the proposed 3-D PCB winding transformer and integrated layout.