Embedded Current Sensor for SiC Die Current Measurement

Abstract:
A common challenge when designing compact fast switching multichip power modules based on wide bandgap semiconductors is imbalanced current sharing between the parallel dies. The issue arises in asymmetric layouts where different parasitic inductance values will be present in the individual power or gate loops for the parallel connected dies. Experimental verification of the current sharing between the dies in a multichip power module is limited by the lack of current sensing strategies suitable for performing accurate drain current measurements of each individual die. This paper proposes a two-stage current sensor consisting of a customizable current transformer and a Pearson current monitor. The current transformer can be embedded into a multichip power module with its core encircling a single die to provide measurements of the die’s drain current. The concept is verified with a double pulse test performed at 200 V and 17.7 A of an asymmetric power module with four parallel connected silicon carbide dies. The measured die currents are compared to the total switch current measured with a 30MHz Rogowski coil where the current imbalance due to the asymmetric layout is clearly seen.