Abstract: In order to reduce the mass of the spacecraft，improve the service life，and meet the needs of commercial aerospace small satellite electric propulsion systems，the digital design requirements of the PPU and the design scheme of the beam power supply were summarized.The BUCK scheme and the full-bridge circuit were adopted to design beam power supply according to the requirements of high precision，high stability，and fast response of the PPU.With STM32 microcontroller as the core，digital heating power supply and beam power supply were designed to realize data acquisition and telemetry of satellite platform/ground detection equipment，and the change of output voltage parameters of power supply.The experimental results show that the control accuracy of the three digital power supplies is less than 3%，and that the digitally controlled PPU has the characteristics of flexible adjustment，which can effectively reduce the volume of the control board.

Key words: ion electric propulsion, digital power supply, power processing unit（PPU）, beam power supply, control unit