A high speed pulser thyristor

A pulse power thyristor (PPT), has features optimized for pulse power applications: high di/dt, compact size and high current densities >10⁴ A/cm². These features are enabled by enhancing the turn-on mechanism through field aided drift and a very high level of gate-cathode interdigitation. The technology allows high blocking voltage >5 kV in small, low cost packages. The device described in this paper is optimized for turn-on and, as such, is labeled a pulse power closing switch thyristor (PPCST). The device structure is briefly discussed along with details of field aided drift as a critical dynamic mechanism. A trade-off for fast turn-on shows that the dynamic resistance and leakage currents are higher than typical thyristors. A major attribute of the device design is to self limit the anode di/dt without self-destruction or having the requirement for series inductors. A dynamic test circuit was developed with the potential of greater than 110 kA/μs. Test results show that the di/dt is limited by the PPCST and not inductance. The current rise from 10% to 90% occurs within 260 ns to a peak current of 4.85 kA to yield a di/dt of 14.9 kA/μs. The 10% to 70% rise yields better than 20 kA/μs. During rapid di/dt of anode current the gate-to-cathode voltage became excessive. There, also, was an indication of possible current flow out of the gate during the same interval. Thus, an ultra-fast constant-current gate drive circuit was developed. The drive delivered 0 to 30 A in <400 ns and maintained the 30 A during the entire turn on interval. The excessive voltage was due to 5 nH of internal package inductance