Circuit topology and control principle for a first magnetic stimulator with fully controllable waveform

Abstract

Magnetic stimulation pulse sources are very inflexible high-power devices. The incorporated circuit topology is usually limited to a single pulse type. However, experimental and theoretical work shows that more freedom in choosing or even designing waveforms could notably enhance existing methods. Beyond that, it even allows entering new fields of application. We propose a technology that can solve the problem. Even in very high frequency ranges, the circuitry is very flexible and is able generate almost every waveform with unrivaled accuracy. This technology can dynamically change between different pulse shapes without any reconfiguration, recharging or other changes; thus the waveform can be modified also during a high-frequency repetitive pulse train. In addition to the option of online design and generation of still unknown waveforms, it amalgamates all existing device types with their specific pulse shapes, which have been leading an independent existence in the past years. These advantages were achieved by giving up the common basis of all magnetic stimulation devices so far, i.e., the high-voltage oscillator. Distributed electronics handle the high power dividing the high voltage and the required switching rate into small portions.

Enhancement of Neuromodulation with Novel Pulse Shapes Generated by Controllable Pulse Parameter Transcranial Magnetic Stimulation

“…Alternative approaches could involve device developments that would allow the generation of unidirectional monophasic pulses at high repetition rates. In principle, the cTMS device power supply could be modified to accomplish this, or a novel circuit topology that allows the efficient generation of virtually any pulse shape could be deployed (42,45,46,72). …”

Pulse width dependence of motor threshold and input–output curve characterized with controllable pulse parameter transcranial magnetic stimulation

“…As demonstrated in this study and in prior papers (Barker et al, 1991; Peterchev, 2011; Peterchev et al, 2008a; Peterchev et al, 2011a), longer pulses, especially as they approach and exceed the strength–duration time constant, consume more energy, require a larger capacitor, produce more heating, and have higher peak coil current compared to shorter pulses. An alternative device topology for flexible pulse shaping (Goetz et al, 2012a) could potentially minimize the required capacitor size and energy storage, making the device smaller and safer compared to cTMS devices, but even with this approach the energy storage and peak coil current would increase for longer pulses.…”

Controllable pulse parameter transcranial magnetic stimulator with enhanced circuit topology and pulse shaping

“…However, the flexTMS device has limitations including a single controllable coil voltage level due to the use of only one energy storage capacitor, restricted pulse width control due to the relatively small energy storage capacitor (66 µF—approximately an order of magnitude smaller than the capacitors in the cTMS devices), and large ringing artifacts in the pulses. Magnetic stimulation devices that potentially allow even greater pulse shaping flexibility have so far been demonstrated only at low pulse energies that are well below the range used for TMS [18, 19]. …”