This thesis details the schematic-level design and functional analysis of a 4-kW mono-phase AC-DC converter developed using the Flying Capacitor Multilevel (FCML) topology and enhancement-mode Gallium Nitride (GaN) transistors. Initially, the converter was developed to address all relevant high-performance applications in grid-connected power supplies such as power factor correction (PFC) systems and electric vehicle infrastructure, as well as for renewable energy conversion applications. The complete implementation of GaN-based switching devices allows for high-frequency operation, low switching loss, and improved power density compared to silicon-based devices. The structure of the converter was based on a multilevel topology, which was able to create intermediate voltage levels using two flying capacitor stages.