Fraunhofer IAF GaN Module Powers Bidirectional Off-Board Charger Demonstrator
The 3 kW single-phase demonstrator weighs 5.7 kg and uses 1,200 V-class GaN devices on an insulating substrate.
Researchers at the Fraunhofer Institute for Applied Solid State Physics (IAF) and industry partners have developed a gallium nitride (GaN) power electronics module designed for 800 V-class bidirectional DC charging systems. The technology powers a compact off-board charger demonstrator capable of interacting directly with vehicle batteries via the CCS connector.
What Happened
The development stems from the GaN4EmoBiL research project, a three-year initiative funded by Germany’s Federal Ministry for Economic Affairs and Energy (BMWE) under its Elektro-Mobil program. Partners including the University of Stuttgart, Bosch, and Ambibox collaborated to create semiconductor, device, and system technologies for bidirectional charging in the 800 V class. The project explored high-voltage GaN transistors on alternative substrates such as silicon, silicon carbide, and sapphire to reduce costs, alongside bidirectionally blocking power switches for AC and DC chargers.
Ambibox integrated Fraunhofer IAF’s module, which utilizes 1,200 V-class GaN devices fabricated on an insulating substrate, into a single-phase off-board charger demonstrator. The unit delivers an output of up to 3 kW, measures 8.3 liters in volume, and weighs 5.7 kg including connectors. It connects to vehicles through a standard CCS connector and a grounding-type plug.
Why It Matters
The demonstrator illustrates a potential pathway for highly efficient and cost-effective charging systems by leveraging GaN technology beyond its traditional 600 V commercial limits. Stefan Mönch, coordinator of the GaN4EmoBiL project, stated that the team demonstrated an alternative technology pathway enabling devices with blocking voltages exceeding 1,200 V. This advancement lays the foundation for future GaN use in 800 V power electronics for electric vehicles.
The project’s underlying goal is to treat EV batteries as flexible electricity storage, allowing vehicles to store surplus solar or wind power and feed it back into the grid when needed. While the 3 kW demonstrator charges more slowly than powerful on-board chargers, Fraunhofer IAF notes it is significantly more compact and portable. The ability to enable bidirectional charging directly with DC via the CCS connector in a mobile, low-power form factor could expand access to vehicle-to-grid (V2G) capabilities for users without high-power home infrastructure.
The Bottom Line
Fraunhofer IAF and its partners have validated a compact, 5.7 kg bidirectional off-board charger using 1,200 V-class GaN devices. While currently limited to 3 kW output, the demonstrator proves the viability of GaN in 800 V systems for future cost-effective, portable vehicle-to-grid applications.
