High-power semiconductors are key components in electrical drives, as their characteristics influence the performance of the complete drive system. Main aspects for semiconductor switches are low losses, high switching power, simple and low-power gate drive, simple-to-use housings and, last but not least, high reliability of semiconductor, driver and housing.
After a presentation of the most important variants of thyristor-based semiconductors, the limiting influence of parasitics on the safe operating area is discussed in this thesis. A detailed analysis demonstrates the high demands imposed by unity-gain operation, especially on the stray inductance in the commutation loop. One major disadvantage of commercial IGCTs over IGBTs is the more complex gate driver. This aspect can be improved with the Internally Commutated Thyristor (ICT) that is introduced in this work. Compared with standard IGCTs, the key distinction is the integration of parts of the gate drive unit into the press-pack housing. The design process for these internal units, using DirectFET MOSFET and Multilayer Ceramic Capacitors, is given in this work. The theoretically derived excellent reliability of the internal gate drive parts could be verified by experiments with a purpose-built thermal-cycling test bench.
Two different ICT devices were realized and tested in this work. The controllable turn-off current is improved by up to 35% compared to standard IGCTs. Purpose-built gate drive units complete the ICT-based high-power switch, which support cable connection between device and GDU and optionally feature a novel short-circuit detection circuit.
Another device introduced in this thesis is the Dual GCT that consists of a parallel connection of two differently optimized GCTs on a single wafer and enables a significant performance increase.