Body Diode Soft Reverse Recovery Control with Active Miller Clamping for Improved SiC MOSFET Dynamic Characteristics

Silicon carbide (SiC) devices are becoming widely used in emerging power electronics application such as aerospace and automotive traction inverters due to their power density and efficient energy conversion capabilities. Nevertheless, one of the major drawbacks of the SiC MOSFET is that the drain-source voltage of this device presents a strong dependency on the body diode reverse conduction increasing switching losses and ultimately reducing efficiency. The use of an external antiparallel junction barrier Schottky (JBS) diode may partially resolve this problem, but it is costly and takes extra surface area. Current efforts to overcome this problem are aiming to reduce the bodydiode conduction time at a minimum while still on safe operation. However, this approach introduces another challenge of developing active dead-time control circuits. This paper first presents a detailed analysis of dynamic characteristics and body diode reverse recovery effect on the SiC MOSFET drain-source voltage at the inverter terminal including impact of parasitic impedances in the switching loop. Second, a modulated active Miller clamp technique is newly proposed to minimize reverse recovery body diode current slew rate reducing switching power losses by 25% when compared to Miller clamp techniques without modulation.