Unveiling Dielectric Interface Charge Dynamics Under Unipolar Repetitive Pulses with the In-Situ Pockels Effect Technique

Unipolar repetitive pulse (URP) is one of the factors that jeopardize power electronic devices. Failures induced by URP often occur at the interface between two different dielectrics, and this location's inaccessibility makes detection challenging. In this paper, the Pockels effect is utilized for noninvasive monitoring, for the first time allowing the dynamic evolution of interface charges to be observed during the URP interface discharge process, thereby achieving visualization of power modules packaging interface charges that were previously undetectable. The URP interface discharge is updated to include two stages: propagation and persistence. The former is marked by the simultaneous conclusion of interface charge propagation and pulse current, while the latter indicates the persistent activity of interface charges. Furthermore, the evolution of interface charges over multiple URP cycles is defined into different stages based on distribution characteristics. Ultimately, the interface charge density is used to assess interface insulation damage.