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RESEARCH

A WBG Based 400/48V LLC Converter Operating at 500 KHz with 99 % Efficiency

Circuit
Fig. 1: (a) Circuit;
  The new generation of processors for CPU, GPU, and AI demand a significantly higher current level at 500 A-1000 A. To accommodate this much-increased power demand, the data center server rack must deliver 25- 30 KW to server processors with a 48V backplane power bus. The state-of-the-art, silicon-based power module is demonstrated at 96 % efficiency and power density around 40-50W/in3. In this paper, a WBG-based LLC converter is demonstrated with significantly improved efficiency and power density. Operating at 500 KHz switching frequency, the circuit topology and design practice is not without significant departure from the current practice.
  For example, a complicated transformer structure is broken down into three simple transformer structures that can easily be implemented using a form of 4-layer PCB. Furthermore, these magnetic components are integrated into a compact structure that is easy to manufacture. By adding two additional shielding layers into the 4-layer PCB, a 20db reduction of common-mode noises is realized in the entire frequency spectrum of interest, from 150 KHz up to 30 MHz. A 3 kW 400/48V dc-dc converter is demonstrated with a peak efficiency of 99 % and a power density of 450 W/in3 (28 kW/L) as shown in Fig. 1.
Hardware prototype
(b) Hardware prototype;
Tested efficiency
(c) Tested efficiency.


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