Innoscience and University of Bern develop multilevel topology reference demo

The three-level ANPC (Active Neutral Point Clamped) converter uses Innoscience's readily-available INN650D080BS 650V, 80mΩ HEMTs in the 8x8mm DFN package. No snubber capacitors or expensive SiC diodes are required, reducing system cost.

Prof. Timothé Delaforge of the BFH, who worked on this development with Prof. Sébastien Mariéthoz, also of the BFH, explains: "At higher voltages, classic two-level topologies such as a half-bridge are not practical as the 650V-rated HEMTs will fail. But there are many other topologies which mean that we can keep the operating voltage of the HEMT well below its rated voltage, while working with much higher DC bus voltages. In this case we chose the ANPC topology because it enables us to switch 850VDC without needing SiC. 850V is high enough for many industrial and e-mobility applications - even potentially EV drivetrains - if enough care is taken on the circuity design to minimise parasitics.

"We chose Innoscience's InnoGaN HEMTs as they are very high efficiency and reliable, whilst also being the most cost-effective devices available on the market." He concludes.

Dr Denis Marcon, Innoscience's General Manager, Europe, adds: "Although this design uses six HEMTs, because we are switching at much higher frequency, we can reduce the size of the filter and hence shrink the overall size of the converter. Also, with our InnoGaN HEMTs we can achieve inverter efficiencies of 99%, increasing system reliability and decreasing cost."