Abstract: As an important part of power electronic power conversion device，auxiliary power supply is faced

with the application demand of high voltage and wide range in DC transmission，solar power station，wind power

station and other systems. Aiming at the problems of switch stress，cost and efficiency caused by high voltage and

wide range input，the principle analysis and parameter design were carried out based on the series switch flyback

converter，and a 100 W auxiliary power supply prototype with 300～900 V input and 24 V output was designed.

Compared with the traditional scheme，this topology can simply and effectively reduce the voltage stress of the

switch through the zener diode，broaden the selection range，improve the efficiency，and achieve stable operation

within the high voltage and wide range input. Finally，the results of the relevant experiments have been given to

verify the feasibility and correctness of the design of the high voltage and wide range auxiliary power supply

scheme. A low-cost wide input range and high stress efficient power conversion have been realized.

      Key words: auxiliary power supply（APS）；flyback converter；voltage stress