Design and verification of a cascaded nanosecond rise time high-voltage positive-polarity square wave power supply topology

Abstract

High-voltage SiC devices operate under repetitive positive polarity square wave voltages with rise times ranging from tens to hundreds of nanoseconds. Under these conditions, the partial discharge and withstand voltage characteristics differ significantly from those observed in traditional AC and DC tests. Therefore, there is an urgent need to conduct insulation assessments for devices under square wave conditions, which necessitates the development of a high-voltage positive polarity square wave power supply with flexible nanosecond rise times suitable for SiC applications. This paper addresses the need to simulate the actual voltage conditions experienced by SiC devices and proposes a high-voltage positive polarity square wave power supply topology using cascaded low-voltage square wave generation units. The working principle is explained in detail, along with the main hardware design and parameter selection methods. Transient simulation models for both normal and single-stage fault conditions were established, verifying the proposed topology's ability to flexibly adjust square wave output parameters such as frequency, rise time, and duty cycle, as well as its ability to continue operating in fault conditions even with single or multiple switch failures. Finally, a 5-stage cascaded high-voltage positive polarity square wave power supply prototype was developed, achieving flexible and independent control of all switching devices through a field-programmable gate array. The prototype achieved performance parameters of 4 kV voltage level, repetition frequency of DC to 5 kHz, duty cycle of 0% to 100%, and voltage rise time of 80 to 300 ns, validating the overall feasibility and reliability of the proposed topology. The research findings in this paper provide new design ideas for the development of square wave power supplies and offer a power source for the insulation assessment of SiC devices.