Analysis of Oscillation Mechanism during Turn-on of SiC MOSFET

Silicon Carbide Metal Oxide Semiconductor Field Effect Transistor (SiC MOSFET) has recently been found to exhibit better electrical and thermal performance than the traditional Silicon devices due to superior material properties of SiC coupled with the fast switching speed of MOSFETs. Its application to power electronic systems is however accompanied by high switching ringing aggravated by its very fast switching speed. The analysis in this paper focuses on three aspects of turn-on oscillation: determination of dominant transition causing oscillations, derivation of transient and complete turn-on frequency and influence of voltage trajectory change on oscillations after complete turn-on. The ringing of SiC MOSFET during turn-on transient is analyzed and its influence on oscillations after complete turn-on investigated. It is found that the frequency of the turn-on transient oscillations is influenced by the rate of rise of drain current. It is further revealed that a high transient frequency can lead to a change in the trajectory of the falling drain voltage which consequently leads to a lower oscillation magnitude after complete turn-on. Furthermore, the voltage edge is found to be dominant over current edge in triggering oscillations after both complete turn-on and turn-off.