High-frequency, high-current transformer designs for Silicon Carbide based LLC converters

The introduction of 1200 V Silicon Carbide (SiC) based technologies has enabled the use of high performance LLC converters for high input voltage (>500 VDC) applications such as datacenter power conversion. In this paper, we describe performance of the magnetics for a 2 kW-level LLC converter, operating at 100 kHz with SiC devices. We present magnetics designed for high converter efficiencies (> 96%) at high-current outputs (65 A). We focus on the design considerations to minimize the leakage inductance of a center-tapped transformer with a high voltage transformation ratio. We present a variety of winding strategies and show the efficacy of a hybrid solution that combines foil windings with litz winding for the application described. We demonstrate the performance improvements through finite element simulations and measurements from several prototypes.