Current-Cancellation-Based Heterogeneous Integration of LLC-DCX With Ultralow-Voltage High-Current Output for Data Centers

The efficiency and power density of ultralow-voltage (<1 V) high-current output dc transformers (DCXs) are limited by the losses and footprint area of the high-current windings. High-frequency current cancellation and power switches and high-current winding heterogeneous integration methods are proposed to reduce the length, area, and losses of high-current windings. With the proposed current-cancellation-based heterogeneous integration method, most of the high-current printed circuit board (PCB) windings of the transformer are replaced by power switches and capacitors, and almost zero PCB winding is achieved for the high-current secondary windings of the DCX. As a result, both power density and efficiency are improved significantly. A 36-V-to-0.75-V/150-A output DCX with a 48:1 turns-ratio transformer is designed and implemented with the four-layer PCB. A peak efficiency of 94.1% is achieved, while the power density of the high-frequency transformer in the DCX is 0.66 A/mm
²
.