Three-Phase Interleaved LLC Resonant Converter with Integrated Planar Magnetics for Telecom and Server Application

The LLC converter is considered the most efficient topology in server and telecom applications. And, it has been demonstrated that three interleaved LLC converters can achieve further efficiency improvement at the 3KW power level. However, the magnetic components for multiphase LLC are complex, bulky, and difficult to manufacture in a cost-effective manner. In this paper, a high-frequency GaN based three-phase LLC converter is utilized to attempt to address these challenges. With GaN operating at 1 megahertz, all magnetic components, namely three inductors and three transformers, can be integrated in one common structure while all magnetic windings are contained in a compact 4-layer PCB with 3 oz. copper. The proposed structure can be easily and cost effectively manufactured in high quantities. Furthermore, up to a 20db reduction of common-mode noise, from 150KHz up to 30MHz, can be realized if 2 additional PCB layers are employed for proposed CM noise shielding. A 3kW 400V/48V 3-phase prototype is demonstrated, with an expected peak efficiency of 97.4% and a power density of 450W/in3 (28 kW/L).