Abstract：In order to solve the problem of overvoltage and overcurrent in the process of load sudden change

for ion thruster screen grid power supply，the phase shift pulse frequency modulation（PS-PFM）was used to

stabilize the output voltage of the LLC resonant converter. When the sampling voltage is lower than the lower limit

of the set value，it enters into the frequency control mode，and when the sampling voltage is higher than the upper

limit of the set value，it enters into the phase shift control mode. The experiment proves that，compared with the

common frequency control，the addition of phase shift control can solve the problem of high voltage drift in light

load or no-load mode，and through the adjustment of PID parameters，it can achieve stable and fast adjustment

when the load jumps，so that the output voltage remains at the set value. Through the PCB layout and magnetic

components optimization design，the developed principle prototype efficiency reaches 98.9% under rated

conditions，and the power density reaches 6.47 × 106 W/m3，which is advantageous in the same level of power

supply products.

      Key words：ion thruster；screen grid power supply；phase shift pulse frequency modulation（PS-PFM）；fullbridge LLC resonant converter；load sudden change