Study on the soft-start process of PSM high voltage power supply for ECRH Jian Zhang, Rui Guan, Fei Guo, Yu Zhou, Haozhang Sun, Junjiang Wang and Yiyun Huang EPJ Web Conf., 203 (2019) 04019 Published online: 25 March 2019 DOI: 10.1051/epjconf/201920304019