Series–Parallel Connection of Thyristors Triggered in Impact-Ionization Wave Mode

This article demonstrates the impact-ionization switching of standard thyristors in a series-parallel configuration. The series–parallel triggering of thyristors holds a substantial promise for enhancing both voltage blocking and current capacity of the switch simultaneously. Nevertheless, the key obstacle in this context revolves around acquiring a suitable trigger generator, primarily because this trigger necessitates a combination of high
$dV/dt$
and low post-triggering energy to be applied to the thyristor assembly. Thus, a novel trigger circuit is developed to test a setup with two parallel branches, each having two series-connected thyristors (with a wafer diameter of Ø24 mm and a rated blocking voltage of 1.8 kV). These thyristors were tested in the impact-ionization switching mode using a single Marx generator. We conducted experiments in a current flow phase, where energy switching occurred by connecting an
$RLC$
discharge circuit. These experiments revealed that the thyristors transitioned from a blocking to a conducting state around
$\sim$
400 ps, enabling the switching of a current pulse with an amplitude of
$\sim$
17.5 kA and a
$dI/dt$
of
$\sim$
8.5 kA/
$\mu$
s (limited by the circuit). Notably, the current imbalance between the thyristor parallel branches remained under 2%. To the best of our knowledge, this is the first reported instance of successfully triggering high-voltage thyristors connected in series–parallel in the impact-ionization wave mode.