Marx-stacked IGBT modulators for high voltage, high power applications

A number of applications that require <1 μsec risetimes at high voltage and current cannot be easily satisfied with standard designs employing low voltage solid-state components driving a large step-up turns ratio transformer. North Star Research reports on the development of several products that employ the topological erection of voltages using a Marx generator stacking arrangement of lower voltage IGBT devices. The configuration does not place the semiconductors in a series arrangement, thereby eliminating a failure mode wherein the loss of a single device would over-stress the stack of IGBT parts. A plasma source ion implantation (PSII) modulator has been built using this technology development and provides 30 kV, 400 A, 1-50 μsec variable pulse widths, and operates at 7.5 kW of average power. Peak powers as high as 2.4 MW have been demonstrated.