CMOS Active Gate Driver for Closed-Loop dv/dt Control of Wide Bandgap Power Transistors

Wide bandgap (WBG) power transistors such as SiC MOSFETs and GaN HEMTs are a real breakthrough in power electronics. These power semiconductor devices have lower conduction and switching losses than their Silicon competitors. However, the fast switching transients can be an issue in terms of Electromagnetic Interferences (EMI). Consequently, one must slow down the switching speeds of WBG transistors to comply with EMI limitations, which reduces their advantages in terms of higher switching frequencies and lower total losses. In this work, an active gate driver is proposed to control the switching speed of wide bandgap semiconductor power transistors. An innovative closed-loop control circuit makes it possible to adjust separately the dv/dt and di/dt during the switching sequences. Overall, the dv/dt values can be reduced to comply with system-level limits of EMI, with less switching losses than existing methods. The proposed method is thoroughly investigated, with analytic and numerical models to assess the key performances: feedback loop bandwidth, optimal circuit design, area consumption. Selected and optimal designs are implemented in two integrated circuits in CMOS technology which demonstrate delay times below the nanosecond. With such performances, it has been shown experimentally that it is possible to actively control switching speeds higher than 100 V/ns under voltages of 400 V.