Maria R. Rogina

Auxiliary power supply based on a modular ISOP flyback configuration with very high input voltage

This paper proposes a Flyback-based Input-Series Output-Parallel (ISOP) Auxiliary Power Supply (APS), intended to feed the control system of the cells of a Solid-State Transformer (SST). The SST topology is based on a modular Multiport Multilevel Converter (MMC). Energization of the cells auxiliary circuitry is not trivial due to the high voltages involved (tens of kV for the electric power distribution system), most of the commercially available control and driving circuitry not being usable due to the isolation requirements. It is possible to energize the control circuitry from an APS, connected to the cell capacitor voltage. However, in the SST under consideration, cells target DC voltage is in the range of 1.5kV to 2.5kV. Design of an APS capable of feeding the auxiliary circuitry from such high voltage and the required isolation is not trivial. A modular APS using autonomous Flyback converters in Continuous Conduction Mode (CCM) and based on commercial AC adapters is proposed in this paper. The solution is scalable and therefore applicable to cells with larger DC voltages.

Series-connected GaN transistors for ultra-fast high-voltage switch (>1kV)

The feasibility of a 1.2kV GaN switch based on two series-connected 650V GaN transistors is demonstrated in this paper. Aside to achieve ultra-fast transitions and reduced switching energy loss, stacking GaN transistors enables compatibility with high-voltage GaN-on-Silicon technologies. A proof-of-concept is provided by electrical characterization and hard-switching operation of a GaN Super-Cascode built with discrete components. Further investigations to enhance stability with auxiliary components are carried out by simulations and co-integrated prototypes are proven at wafer level.

Switching performance comparison of a power switch in a cascode configuration using a SuperJunction MOSFET

This paper is focused on the analysis of the cascode connection of Superjunction MOSFETs (SJ-FET) working as a high voltage normally-off power switch, based on Silicon technologies. In order to carry out this analysis, it will compare the cascode structure with the standalone connection, in which only one SJ-FET is used. The comparison is carried out in terms of switching behaviour, in order to verify if the cascode has a faster switching than a directly controlled SJ-FET. Experimental measurements are presented for both topologies working on a boost converter with an input voltage of 150 V, output voltage of 400 V, power range between 100 W and 400 W and a switching frequency range between 100 kHz and 400 kHz. Finally, an analysis of losses on the boost converter for both topologies is included.

Gate impedance characterization and performance evaluation of 3.3kV Silicon Carbide MOSFETs

For the development of new wide bandgap high voltage semiconductors, it is necessary to carry out a thorough characterization of their behavior towards their future use in real applications. In this document a basic characterization of new 3.3 kV SiC MOSFET prototypes is presented, both static and dynamic. While the static characterization provides quite good figures of merit of the prototype under test, in the dynamic characterization, slow transitions are detected and they will be explained proposing a model for the configuration of the gate cell inner connections of the presented prototype.