A modified high gain single switch high-voltage converter is presented in this paper. The proposed converter is a blend of a voltage tripler and a SEPIC-boost mode converter. Its operational modes are presented in detail. This converter has advantages that include a single switch, reduced component stress and size, and reduced ripple output voltage and input ripple current. The simulation results of the suggested converter and a conventional multilevel SEPIC converter are presented. The prototype of a 30 V to 400 V input, 400 W output is developed and the performance of the designed topology is evaluated. The theoretical and experimental results conclude that this converter is suitable for high-voltage applications. © 2019 IOP Publishing Ltd. All rights reserved.