# High-Power Wide-Bandwidth High-Quality Modular Pulse Synthesizer with Adaptive Voltage Asymmetry in Medical Power Electronics

## TL;DR

This paper introduces a novel high-power pulse synthesizer that uses adaptive voltage asymmetry to achieve high-resolution waveform shaping with fewer modules, significantly improving output quality in medical power electronics.

## Contribution

It presents the first asymmetric multilevel circuit for high-precision high-power synthesis and introduces adaptive voltage sequencing to optimize waveform quality.

## Key findings

- Reduces voltage distortion by 13.4% with three modules
- Achieves better performance with fewer modules compared to prior art
- First to implement adaptive asymmetric voltage sequences in modular power electronics

## Abstract

Noninvasive brain stimulation can write signals into neurons but requires power electronics with exceptionally high power in the mega-volt-ampere range and kilohertz usable bandwidth. Whereas oscillator circuits offered only one or very few pulse shapes, modular cascaded power electronics solved a long-standing problem for the first time and enabled arbitrary software-based synthesis of the temporal shape of stimuli. However, synthesizing arbitrary stimuli with a high output quality requires a large number of modules. We propose an alternative solution that achieves high-resolution pulse shaping with fewer modules by implementing high-power wide-bandwidth voltage asymmetry. Rather than equal voltage steps, our system strategically assigns different voltages to each module to achieve a near-exponential improvement in resolution. The module voltage sequence does also not use just a simple binary pattern other work might suggest but adapts it to the output. Additionally, we introduce a switched-capacitor charging mechanism that allows the modules to charge to different voltages through a single dc power supply. We validated our design in a head-to-head comparison with the state of the art on experimental prototypes. Our three-module prototype reduces total voltage distortion by 13.4% compared to prior art with three modules, and by 4.5% compared to prior art with six -- twice as many -- modules. This paper is the first asymmetric multilevel circuit as a high-precision high-power synthesizer, as well as the first to adaptively optimize asymmetric voltage sequence in modular power electronics.