Design and comparison of IGBT-based switching modules for laser applications

This paper presents the design of IGBT-based switching modules for a nitrogen gas laser. Cascades with a 11-cell series connections based on different IGBT-chips (1700 V and 1200 V) have been built up and measured. The focus of the design is the development of a high speed synchronous gate drive for the IGBT-gates. The module equipped with the four parallel 1200 V/35 A-IGBTs per cell produces the highest switching power. Among the variants, the peak switch current is up to 700 A at blocking voltages of up to 13.2 kV in the real environment of the nitrogen laser. The switch current slope reaches up to 30 A ns^-1 and the laser tube current up to 1.8 kA. The variant with 1200 V/35 A-IGBTs produces an output energy which is about 15 % higher compared to the former MCT-based switch. Thus, the IGBT-based switches are able to replace the MCT-switches in this application. Between the different IGBT-based switches a tradeoff has to be done between high output energy and the effort for the assembly of the switch.