In order to improve the dynamic response and steady-state characteristics of traveling wave tube high voltage converter in the load mutation condition

a sliding-mode and proportional plus integral（PI） control scheme is proposed

which will be adopted to meet the technical requirements of the high voltage power supply for traveling wave tube. Firstly

the full bridge LLC resonant converter with multiplier rectifier is designed

and the working principle of the LLC converter is analyzed based on self-sustained phase shift modulation. Secondly

the averaged large-signal model of LLC resonant converter is built by using averaged large-signal modeling method. Thirdly

a sliding-mode and PI control scheme is proposed based on the large-signal model

and the nonlinear switched function is introduced to implement the smooth transition between the sliding-mode control and PI control. Finally

the simulation results prove that the proposed control scheme possesses good dynamic characteristics and strong robustness from sliding mode control and good stability from PI control in the load mutation condition

and also possesses some advantages

such as small overshoot

fast response

high steady-state accuracy

and small output ripple. The simulation results show that the zero voltage switching of the proposed LLC converter can be implemented in the whole working condition.