# Compact Design and Impact Ionization: Utilizing Small-Sized Thyristors in a 4-Stage Marx Generator
[16] explored the feasibility of triggering commercial, low-frequency thyristors within sub-nanosecond time frames by applying a high-speed, sub-nanosecond pulse directly to their main electrodes via a compact solid-state generator. Further expanding on this concept, [PERSON]. [17] investigated the parallel switching of high-voltage thyristors under the impact-ionization wave mode, employing a Marx generator with a peaking module to ensure the required steep voltage rise. This approach successfully controlled high current pulses while mitigating current imbalances between devices. With these findings affirming the viability of inducing impact ionization in commercial thyristors, attention then shifted toward identifying the most efficient triggering strategy. The potential of fast-opening switches for triggering in impact-ionization mode has been explored in prior studies [18], specifically with drift step recovery diodes (DSRDs) and SOS diodes as pulse-generating components. Despite their advantages, these devices suffer from several drawbacks, including limited commercial availability, bulky designs, and pre-charging phases of several hundred nanoseconds, leading to pulse-triggering delays exceeding 500 ns [19]. Both DSRDs and SOS diodes operate as opening switches, rapidly restoring their blocking state once the pre-charged plasma dissipates from their structure--an effect akin to the reverse recovery process observed in conventional diodes [20]. However, this mechanism imposes a crucial challenge, that is, plasma must first be generated and sustained before triggering can occur--a requirement that significantly complicates system implementation and demands substantial resources. In contrast, using a spiral generator to trigger hyristors in impact-ionization wave mode, as demonstrated in Ref. [21], involves utilizing a compact design based on the spiral/vector inversion principle. This generator charges a spiral stripline to a high voltage, which is subsequently discharged upon activation, reversing the electric field direction and effectively amplifying the output voltage. While the compact design of the spiral stripline's design offers advantages over other high-voltage generators, adapting this design to different scales poses significant challenges. Similarly, difficulties arise when attempting to boost performance while preserving efficiency and preventing any expansion of the physical footprint. Building upon prior developments, [22] explored the application of a Marx generator for initiating hyristors in shock-ionization (impact-ionization) wave mode. To achieve the required trigger voltage, researchers employed a 60-stage avalanche transistor Marx generator, demonstrating its capability in driving the ionization process effectively. Likewise, our earlier research incorporated a Marx generator into an ultra-fast gate-boosting driver designed for high-voltage SiC MOSFETs. This system, utilizing six SiC MOSFETs rated at 1.7 kV, successfully generated output pulses reaching 1.45 kV with a peak slew rate of approximately 2.5 kV/ns ([23]). This current paper details the enhancements made to this design, where the output signal is amplified and sharpened using a Marx generator constructed from small-package thyristors. These improvements aim to boost the output voltage, slew rate, and current, thereby making it suitable for application in the impact-ionization wave mode of thyristors, as demonstrated in [17; 24]. The primary motivation behind our research is the replacement of thyratrons in high-power, fast-pulsed applications. In such systems, trigger precision is critical, as misfiring events can lead to severe operational issues. Our ultimate goal is to minimize the delay between the trigger signal and energy dumping, ensuring that the transition occurs as rapidly as possible. While alternative methods exist--such as spiral generators or opening switch-based architectures--our comparative analysis shows that they are not suitable for our specific application.