Novel Pulse Generator for Advanced TMS Applications: A Multilevel Converter Approach

This paper presents the development and evaluation of a novel pulse generator, specifically designed for high-current pulse applications, such as in Transcranial Magnetic Stimulation (TMS). The system integrates a multilevel converter with six half-bridge Submodules (SMs), an external H-bridge Polarity Inverter (PI), and a dedicated charge circuit, thereby enabling the generation of 13 distinct voltage levels, including negative pulses.The optimal pulse profiles were determined through simulation studies and subsequently validated through hardware tests. The system achieved a maximum pulse current of 588 A, surpassing the targeted 560A without any damage. The effective parasitic inductances were calculated to be within the range of 0.73 nH to 2.45 nH for the SMs. In contrast, the H-bridge PI exhibited higher parasitic inductances, with a range of 320 nH to 360 nH. The elevated voltage overshoots observed in this system can be attributed to the higher inductance present in the PI.The pulse generator’s design allows for the generation of customisable pulse shapes and durations, enhancing its versatility for applications such as TMS. Future improvements will focus on optimising the layout, increasing voltage and current ratings, and further minimising parasitic effects.