Optimal Design Methodology for High Frequency GaN Based Step-up LLC Resonant Converter

LLC resonant converter is widely used due to its high efficiency and high power density capability. The design methodology for it has been addressed in many literatures. However, most of them focus on the step-down LLC converter due to its high-output current applications such as data center. In this paper, the optimal design methodology for high frequency GaN based step-up LLC converter for solid-state transformer application is discussed. An accurate model for deadtime operation is derived. From the model, the approach for device selection for both primary and secondary sides and the magnetizing inductance design to have zero-voltage-switching (ZVS) are presented. To verify the design methodology, LTSPICE simulation is performed. Besides, a 1 MHz 1.8 kW step-up LLC converter prototype is designed and tested. With the proposed design methods, the efficiency can achieve 98.75%.