Light Load Operation Analysis for MHz GaN Based LLC Resonant Converter

LLC resonant converter is popular for dc-dc converter designs due to its simple topology, galvanic isolation and soft switching capability. Therefore, lots of researches have been performed for LLC converter design and optimization to pursue high efficiency and high power density with high switching frequency. However, relevant research about the analysis and ZVS model for LLC converter with light load condition under MHz switching is scarce. In this paper, detailed analysis for MHz GaN based LLC converter is provided with light load. Moreover, a simple and accurate ZVS model is proposed, which can help determine fully ZVS condition for primary side devices. To verify the analysis and the proposed ZVS model, a 1 MHz/300 W (10% load) GaN based LLC converter prototype is built and tested.