The 4.6GHz LHCD system is an important part of the auxiliary heating system on EAST tokamak. The cathode high voltage power supply(HVPS) is based on pulse step modulation (PSM) technology, in which 64 modules are used to output 50kVDC in series. The modulation frequency of single PSM module is 50Hz, it switch on and off every 20ms, so the regulation speed of system is limited. In the face of the interference caused by the voltage fluctuation of the grid side during the tokamak operation, the HVPS cannot make more rapid response. It means that a large fluctuation of the output voltage will be produced and output performance of microwave will be affected. In order to improve the regulation speed and anti-interference capability of system, the high frequency PSM module with 1kHz modulation frequency capability was designed to replace some of the original low frequency modules. The fluctuation of output voltage was reduced by the rapid regulation capability of the high frequency module. The experimental results show that the output voltage fluctuation rate of the upgraded power supply is reduced by 50%, which better meets the control requirements of klystron for voltage accuracy and stability, and the reliability of the system is guaranteed.

4.6GHz LHCD系统是EAST托卡马克上辅助加热系统的重要组成部分。阴极高压电源（HVPS）基于脉冲步进调制（PSM）技术，其中64个模块用于串联输出50kVDC。单个PSM模块的调制频率为50Hz，每20ms开关一次，因此系统的调节速度受到限制。面对托卡马克运行期间电网侧的电压波动引起的干扰，HVPS无法做出更快的响应。这意味着将产生很大的输出电压波动，并且会影响微波的输出性能。为了提高系统的调节速度和抗干扰能力，具有1kHz调制频率功能的高频PSM模块旨在替代某些原始的低频模块。高频模块的快速调节能力降低了输出电压的波动。实验结果表明，升级电源的输出电压波动率降低了50％，更好地满足了速调管对电压精度和稳定性的控制要求，保证了系统的可靠性。