A LLM‐Guided Approach for Active‐Clamped Flyback Converter of Power Processing Units in Electric Propulsion

Electric propulsion (EP), recognised for its high efficiency compared to chemical alternatives, plays an indispensable role in modern spacecraft. Within EP systems, the power processing unit (PPU) serves as a critical interface that conditions electrical energy from the power source to drive the thruster, enabling propellant acceleration. The stringent mass and volume constraints aboard spacecraft demand PPUs with exceptional efficiency and power density, objectives that conventional design approaches often struggle to meet under EP‐specific operating conditions. To address this gap, this paper presents a structured large language model (LLM)‐guided design methodology for an active‐clamped flyback converter in satellite EP‐PPUs. Employing gallium nitride (GaN) devices and critical conduction mode (CrCM) operation, the converter achieves zero‐voltage switching across the full load range, thereby enhancing both power density and efficiency. The proposed LLM framework automates topology analysis, operational mode selection, parameter constraint derivation and iterative SPICE simulation, establishing a collaborative and interactive design workflow. Experimental validation using a 24‐V‐to‐1.68‐kV and 400‐kHz prototype demonstrates consistent soft‐switching across all loads, a peak efficiency of 86.8% and a power density of approximately 16.1 W/. Moreover, the front‐end design cycle is reduced by about 76%, confirming the potential of LLMs to act as physics‐informed simulation‐capable co‐designers for high‐frequency high‐step‐up space power converters.