Planar Rogowski Coil-Based Switch Current Measurement for a 1.2 kV SiC MOSFET Embedded Die PCB

This paper introduces the integration of a small footprint planar Rogowski coil into an 1.2 kV embedded die PCB for the switch transient current measurement thereof. Due to the high-density integration of embedded die PCBs, measuring switch transient currents has been challenging. The planar Rogowski coil enables the current measurement with a small impact on the commutation loop design and parasitic stray inductance. The geometry of the 106 mm² small coil increases the stray inductance in the commutation loop by 298 pH. The 187 MHz bandwidth current sensor allows measuring the fast switch transient currents of the 1.2 kV SiC MOSFETs. The planar Rogowski coil is first compared to alternative high-bandwidth current measurement technologies. Double pulse tests are conducted at a dc-bus voltage of 600 V and a drain current of 150 A. The overshoot voltage during the turn-off switch transient for embedded die PCBs with and without the planar Rogowski coil at a current slope of −48.2 A/ns are 646.1 V and 657.6 V, respectively. The small overshoot voltage highlights the minimal added insertion stray inductance of the current sensor into the commutation loop.