Recommendations from upcoming EU flight 2050 emission goals for fully electric aircrafts has lead to new design innovations such as superconducting power conversion and motor drives. This results in focus on operating future aircrafts at cryogenic temperatures. As a result, power electronic designers are implementing GaN based converters due to their improved performance at lower temperatures. Gate drivers being the most important component in these converters provide isolation and common mode transient immunity, this paper focuses on the design of an active clamp fly-back topology based auxiliary power supply. The converter topology was integrated with other components and tested successfully at 77 K for a double pulse test (DPT) platform. The implemented topology can be extended to other DC-DC conversion applications for auxiliary purposes.