Low-Loss Integrated Inductor and Transformer Structure and Application in Regulated LLC Converter for 48-V Bus Converter

In this article, an LLC converter using gallium nitride (GaN) transistors is proposed for a 48-V regulated and isolated bus converter. Compared with pulsewidth modulation (PWM)-based topologies, the soft switching capability of an LLC allows operation at very high frequencies. In addition, the size of the magnetic components is reduced without sacrificing the efficiency. In this article, a novel magnetic structure that integrates a matrix transformer and inductor with minimum winding and a single magnetic core is proposed, to allow a high-density and high-efficiency LLC converter design for a bus converter. A 40-60-V input and regulated 12-V output converter is developed to deliver a 1-kW output power in a quarter brick form factor. The designed converter can achieve a power density of 700 W/in
³
with a maximum efficiency of 97.82% at half-load, dropping to 97.7% at full-load operation.