800V synchronous buck converter with series-connected GaN power transistors

Today's GaN on Si semiconductor technology enables power transistors with the maximum blocking voltage of 650V. However, for the majority of industrial converter applications 1200V blocking voltage of power transistors is desired. The approach to overcome this limited blocking capability is a series connection of two GaN devices. With this circuitry today's well-known two level topology can be used without the need of a more complex and cost-intensive multilevel solution. For the feasibility study a 80A, 650V single GaN device was used. With the realized synchronous configuration the switching behavior of the proposed circuitry is demonstrated at 800V DC-link voltage; the switched current is up to 100A. The measurements are compared to the switching performance of a conventional 1200V Si-IGBT.