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Direct Light-Triggered Solid-State Switches For Pulsed Power Applications

For pulsed power applications solid-state switches are required. Because of their easy series connection in stack assemblies and the reliable way of triggering direct light- triggered thyristors should be preferred as solid-state switches. Furthermore, such high-power light-triggered thyristors enable the integration of protection functions like, e.g., overvoltage protection and dv/dt protection. Direct Light-Triggered Thyristors (LTTs) are well known since the 1960s. At the beginning of this development the main problem was the availability of a powerful and cheap light source for triggering. Because of the demand for a powerful and cheap light source for communication, suitable laser diodes became available. In 1995, eupec developed a 4-inch 8 kV direct light- triggered thyristor suitable for solid state switches. Because of the target market of High Voltage Direct Current transmission (HVDC), the LTTs are provided with overvoltage and dv/dt protection functions, both directly integrated into the thyristor. The thyristors are fabricated like electrically-triggered thyristors (ETTs) by well-established technologies. The only difference between ETTs and LTTs is the light sensitive gate area containing the integrated protection functions in the center of the thyristor.

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• 11/02/2014