Noninvasive measurement of chip currents in IGBT modules

Abstract

Modern IGBT modules employ a number of die connected in parallel. Measurement of the effects of layout topology and variations in chip parameters and temperatures requires a noninvasive current measurement system. This paper describes a method for the noninvasive measurement of currents in modern power devices. It discusses methods for incorporating the system into test modules and shows results obtained from measurements on IGBTs. The system consists of miniature magnetic field probes and active wide bandwidth integrators. The probes are small (6 mm), immune to stray fields and are insulated up to several kV. This system has been used to show current redistribution between IGBT chips in a module at turn off and temperature dependent switching of IGBT chips. Furthermore, switching-loss distribution in parallel IGBT chips and gate topology effects were investigated.