A study of dynamic high voltage output charge measurement for 15 kV SiC MOSFET

摘要

Newly developed 15 kV silicon carbide (SiC) power MOSFETs with fast switching capability enable the reduction of size, weight and complexity of medium voltage power converters. In medium voltage and high frequency applications, zero voltage switching (ZVS) is necessary since significant amount of energy is stored in MOSFETs' parasitic output capacitors. Recovering these energy is important for high conversion efficiency while ZVS also reduces the dV/dt significantly in these devices. To guarantee complete ZVS, it is crucial to accurately characterize the output charge of devices. In this paper, existing high voltage capacitance and output charge measurement techniques are reviewed. A dynamic half-bridge test method for 15kV SiC MOSFETs' output charge measurement is thoroughly analyzed and experimentally verified up to 6 kV. Output capacitance model is then derived using the measured results. The test circuit not only reflects the realistic ZVS scenario, but also achieves high accuracy (<;1% error) without resorting to special equipment or complex configuration which are usually necessary in high voltage test. System level design consideration, error analysis and accuracy certification for this high voltage tester is also given in the paper.