On-Board Converters

We are specialized in top tier DC/DC converters: galvanically isolating, bidirectional, and single-stage. This enables us to offer solutions with high power density and a high power-to-weight ratio. Our developments are ideal for safety-relevant applications such as autonomous driving or electric flying. For current projects, we use our iisb² (integrated, galvanically insulated, separated buck/boost) circuit topology as the basis.

Aircraft On-Board DC/DC - Project GETpower2

© Amelie Schardt / Fraunhofer IISB
© Elisabeth Iglhaut / Fraunhofer IISB

Demonstrator from the BMWi GETpower2 project

  • HV voltage: 540 V to 840 V
  • 12/24/48 V versions
  • max. 11.2 kW / 400 A @ 28 V
  • approx. 4 dm³ construction volume / approx. 7 kg.
  • Design for aviation sector: e.g. factor 2 voltage reserve for HV SiC MOSFETs, increased clearance and creepage distances, special housing for protective glass filling

On-Board DC/DC Converter

Isolated high voltage DC/DC converter for auxiliary power supply

© Fraunhofer IISB
  • Two input voltage and three output voltage versions for 12 V, 24 V or 48 V auxiliary power supply
  • Full digital control
  • Communication via CAN
  • 85 °C max. coolant temperature
  • The serial connectable phases on the primary side allow the use of cost efficient semiconductors with only 600 V blocking voltage up to 800 V DC-Link voltage


Bidirectional HV - 48 V - 12V DC/DC Converter

© Fraunhofer IISB

The customer-oriented on-board DC/DC converter has three independent bidirectional ports to connect all future available on-board grids: HV, 48 V and 12 V. With the converter, complex automotive on-board energy management tasks can be fulfilled, like boosting energy between the 48 V and 12 V grid, size reduction of the 12 V battery, replacement by supercaps or transferring energy between the high voltage grid and the low voltage grids. For safety reasons, the12 V as well as the 48 V port are galvanically isolated from the HV port. The converter can be fully controlled via CAN and is characterized by its extremely low height of just 49 mm. Due to the well chosen circuit topology and the advanced design and packaging, a very high power density is achieved for a converter with the described high functionality.


  • Three independent, bidirectional ports (HV, 48 V, 12 V)
  • All three ports useable at the same time
  • Galvanic isolation between HV and 48 V
  • Galvanic isolation between HV and 12 V
  • Wide input/output voltage ranges
  • Over voltage / current protection / temperature control
  • Voltage & current control modes for all ports
  • High partial load efficiency through phase shedding
  • CAN communication
  • Water cooling
  • High power density
  • Ultra-low profile
  • Without electrolytic capacitors
  • Usable for different electric energy storages (LiIo-batteries, lead acid batteries, supercaps)
  • Designed for complex automotive on-board energy management tasks