The most important characteristics of aircraft power system are power density, reliability, availability and power quality. The traditional more electric aircraft (MEA) 28 VDC network is used to power the core electronic system. However, the 28 VDC network in modern MEAs such as B787 or A380 is a centralised power network obtained by transformer rectifier unit (TRU), battery charge and rectifier unit (BCRU) or two-stage power conversion (AC/DC + DC/DC) from 230 VAC, 400–800 Hz variable frequency input. The traditional centralised architecture is of low-power density and low fault tolerance. Furthermore, compared to distributed power network, the centralised architecture is of less availability inherently, therefore a single-stage, isolated, low-power and high-power density power supply is required to achieve the distributed 28 VDC network. In this study, a three-phase single-switch discontinuous mode AC–DC flyback converter is proposed. The converter directly rectifies a three-phase, 400–800 Hz, 230 VAC network into a 28 VDC network. The operation modes of the converter are analysed. A prototype is carefully designed and implemented using high-frequency planner transformer and SiC MOSFET techniques, aiming at higher performance. Experimental results demonstrate the practicability and high performance of the proposed power supply system.