PhD student Ryan Billings with Advisor A. Stillwell

Pulsed power is found in various applications, such as manufacturing, medical technology, and scientific research. These diverse applications motivate different improvements to pulsed power technologies, ranging from power density, pulse repetition rate, pulse width, or pulse rise time, to name a few. The Marx generator is a modular power converter capable of creating high voltage pulses by charging and discharging a network of capacitors in parallel and series, respectively. The Marx generator can come in many forms, depending on the desired pulse output, repetition rate, or reliability needed in the application. Figure 18 shows a version of the Marx generator using a resistor to limit the inrush current during charging. By charging the capacitors in parallel (by closing the switches labeled “d”) and discharging the capacitors in series (by closing the switches labeled “c”), a voltage pulse at the output load can be produced that is n*Vin, where n is the number of capacitors (n also corresponds to the number of Marx stages). The developments in wide band gap semiconductors, namely gallium nitride (GaN) and silicon carbide (SiC) devices, have enabled significantly faster rise times and higher power densities. Our research aims to expand on the traditional Marx generator topology and design a modular pulsed power converter that can produce a scalable output voltage pulse at high switching frequencies through the use of GaN devices, coupled with novel switched capacitor topologies and precise control. Work is currently underway to evaluate two topologies to realize improved power density and efficiency for the Marx generator, with a working prototype shown in Figure 19.

Figure 18. Traditional solid state Marx generator

Figure 19. Hardware prototype for a 4 stage Marx generator.