Research project investigates bidirectional charging with GaN semiconductors

In order to be able to use bidirectional charging of electric cars »on a broad scale,« a consortium led by the Fraunhofer Institute for Applied Solid State Physics IAF in Freiburg, Germany, wants to advance the development of suitable technologies in the project »GaN4EmoBiL – GaN power semiconductors for electromobility and system integration through bidirectional charging.« The focus here, as the name of the project suggests, is on the use of gallium nitride (GaN) semiconductors in charging stations.
Medium-power bidirectional DC wallboxes for batteries up to 800 V that are available today, according to a release on the project, »use power semiconductor devices which are not yet optimal for this application: They are either efficient but expensive (silicon carbide) or low-cost but less efficient (silicon).« In contrast, low-cost 650 V gallium nitride-on-silicon (GaN-on-Si) transistors available today required complex circuitry because of their insufficient dielectric strength.
The project consortium, which includes the University of Stuttgart, Robert Bosch GmbH and Ambibox GmbH, therefore aims »to realize a new cost-effective GaN technology on alternative substrates (for example sapphire), which enables low-cost and efficient 1200 V transistors.« On this basis, a bidirectional charging cable and charger are to be developed and tested for reliability.

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