Implementation and investigation of the dynamic active clamping for silicon carbide MOSFETs

摘要

Silicon carbide (SiC) devices are known for their fast switching transients. The combination of stray inductances in the load circuit and high di/dt values can lead to very high transient overvoltages. Therefore, the reduction of the stray inductance is one of the most important steps to utilise the full potential of SiC devices. However, in some applications the stray inductance cannot be reduced further and high overvoltages are unavoidable. Since protective circuitries like the Dynamic Voltage Rise Control (DVRC) and the “classical” Active Clamping (AC) do not sufficiently work for discrete SiC transistors, the interaction of a SiC MOSFET and the more promising Dynamic Active Clamping (DAC) is investigated to reduce overvoltages. As a consequence of parasitic elements, which affect the switching process, an improved version of the DAC is proposed. Beside the comparison of switching energies and overvoltages, the dependence on the MOSFET junction temperature is analysed to get a better understanding, how different operation conditions influence the efficiency of the DAC.