System-Level Design Approach for LLC Converters

Abstract

LLC resonant converters are designed with a specified resonant frequency that is usually determined based on the experience of the designers while impacting the losses and the dimension of the converter. In this paper, a systematic design framework is proposed that attempts to determine the resonance frequency by considering system loss, volume and cost. To achieve smaller sized transformer, this paper considers series connected primary and parallel connected secondary windings with a multi-core configuration. The proposed algorithm aids designers to optimally size the LLC and has been demonstrated on a 3700W 48V design.