| Abstract |
In this paper, the impact of using parallel SiC MOSFETs as the switching device is investigated. Mea-surement considerations for a double pulse test are discussed, and the influence of the load inductorcharacteristic and the voltage measurement technique on the measurement results is demonstrated. It isshown that the inductor load can produce high frequency oscillations of up to 10 \% of the load currentin the switching current, which can wrongly be associated with the switching device. It is also shownthat the standard earth connection of passive voltage probes can induce an extra stray inductance in themeasurement loop, which can lead to a measurement of an extra overvoltage of up to 50 V, which is notdue to the actual switching.Moreover, the dependency of turn-on and turn-off losses on the load current and the dc-link voltageis presented. It is shown that doubling the load current would increase the switching losses more than thedouble amount. Therefore, use of two parallel MOSFETs instead of a single one would decrease the totalswitching losses for a given load current. On the other hand, the parallel configuration is shown to havea higher overvoltage than one single MOSFET for a similar load current. This, however, can be reducedby a higher gate resistance which will eventually keep the total switching loss of parallel configurationequal to the single MOSFET configuration for a given load current.Finally, it is also shown that switching losses can be greatly decreased by decreasing the gate resis-tance, but this leads to a higher overvoltage on the device. Therefore, the final choice for design is acompromise between the switching losses and the overvoltage. |
