New topologies of multi-level power converters for use of next-generation ultra high-speed switching devices

Next-generation power switching devices such as SiC-MOSFETs are very promising as future power converter components because their voltage rating and switching speed can dramatically be improved by approximately ten times of those of currently available Si devices without sacrificing ON-state resistance. However, they are likely to cause serious EMI noise problems due to their 10⁴-V/mus order switching speed. It is rather difficult to drive such devices by using conventional isolated gate-drive power supplies and optocouplers because noise currents generated by extremely high dV/dt can easily penetrate parasitic capacitance between their primary and the secondary circuits. This paper proposes novel multi-level power converters through investigation of unique different circuit topologies than conventional converters, which can substantially solve the problems mentioned above. The key feature of the proposed topologies is that all switching devices used in the converters are connected on an exactly identical potential level without isolation; hence the proposed converters require only a single gate-drive power supply to drive all the devices and are inherently free from the violent potential variation. Several experimental test results are presented in the paper, which demonstrates proper operations of the new topology based multi-level power converters.