Optimal Design of Electronic Bouncers for Long-Pulse High-Power Modulators

Modern high-voltage high-power pulsed modulators typically generate pulses by discharging energy stored in one or more capacitor banks into the load. The capacitor discharge manifests itself as output pulse droop which must be compensated for. To eliminate such droop, modulators utilizing pulse transformers require external circuitry and, typically, passive resonant bouncer circuits are used. For long-pulse applications, however, electronic bouncer circuits operated in closed loop are preferred due to their compactness, efficiency, precision, and resilience to aging effects. Electronic bouncers may also be used in applications with varying pulselength and/or pulse repetition rate. In this article, design models are developed for both the modulator capacitor bank as well as each electronic bouncer circuit component. The design models are integrated in a global optimization routine used to study design tradeoffs between the modulator capacitor bank and the electronic bouncer, as well as between system efficiency and system volume. An optimization case study based on European Spallation Source modulator requirements (pulse amplitude 115 kV/100 A, pulselength 3.5 ms, pulse repetition rate 14 Hz, combined pulse flat top ripple and droop < 0.15%) is provided, and an optimal design solution is selected and validated through characterization in both circuit simulation and 3-D finite element analysis. Finally, the performance of the chosen electronic bouncer solution is compared to that of an optimized design based on the conventional passive resonant bouncer circuit.