Fraunhofer IAF GaN power module drives compact bidirectional 800V off-board charger demo

The Fraunhofer Institute for Applied Solid State Physics (IAF) and its partners in the GaN4EmoBiL research project have developed a gallium nitride (GaN) power electronics module for 800 V-class bidirectional DC charging systems. It powers an off-board charger demonstrator.

Fraunhofer IAF, the University of Stuttgart, Bosch and Ambibox jointly developed semiconductor, device and system technologies for bidirectional charging in the 800 V class. The project focused on AC and DC chargers, bidirectionally blocking power switches and high-voltage GaN transistors on alternative substrates such as silicon, silicon carbide and sapphire, which are intended to reduce cost. Germany’s Federal Ministry for Economic Affairs and Energy (BMWE) funded the three-year project under its Elektro-Mobil program.

The project was based on using EV batteries as flexible electricity storage, to store surplus solar or wind power and feed it back into the grid when needed.

Fraunhofer IAF’s module uses 1,200 V-class GaN devices fabricated on an insulating substrate. Ambibox integrated the module into the demonstrator, a bidirectional, single-phase off-board charger with an output of up to 3 kW.

The demonstrator has a volume of 8.3 liters and weighs 5.7 kg, including connectors. Fraunhofer IAF says it is significantly more compact and portable than the on-board chargers installed in vehicles, although it charges more slowly than those more powerful systems. It connects through a CCS connector and a grounding-type plug.

“The demonstrator shows that even low-power external off-board chargers can be designed to be particularly compact and mobile while enabling bidirectional charging directly with DC via the CCS connector,” said Stefan Mönch, Coordinator of the GaN4EmoBiL Project. “GaN-based power electronics in the 1,200 V class offer significant potential for highly efficient and cost-effective charging systems.”

“Gallium nitride has long been largely limited to the 600 V class in commercial applications,” said Mönch. “In the GaN4EmoBiL project, we demonstrated an alternative technology pathway based on GaN on insulating substrates. This enables the development of devices with blocking voltages exceeding 1,200 V. In doing so, we are laying the foundation for the future use of GaN in 800 V power electronics for electric vehicles and their system integration.”

Source: Fraunhofer IAF