DC/DC Converters

We develop all kinds of insulating DC/DC converters for mobile applications. This includes e.g. insulating high voltage (up to 850 V) to low voltage (commonly 14 V, 24 V or 48 V) converters in the power range from 10 W up to approx. 5 kW. With efficiencies of up to 97% and power densities up to 10 kW/dm³, they can be easily integrated into a small car, directly inside the high voltage battery system or the drive inverter. The photo to the left gives a closer look at how by using modern power devices, full digital control techniques, and mechatronic approaches, outstanding power densities and efficiencies are reached.

As with other Fraunhofer IISB vehicle electronics prototypes, insulating DC/DC converters can be developed for plug-and-play installation.

As an example of a fully housed, insulated 5 kW DC/DC converter with automotive qualified connectors shows. It could be used within two different voltage ranges for applications in light or heavy trucks and can be controlled via CAN interface. Due to the serial connectable phases on the primary side, the use of automotive qualified Si power semiconductors with 600/650 V blocking voltage is possible to reach a DC-Link voltage up to 800 V.

Our high voltage, non-insulating, bidirectional converters are mainly used for traction energy management in case of recuperation, boost, the management of different power sources (e.g., fuel cell and battery), and fast charging. The converter covers a power range up to about 600 kW with efficiencies up to 99%.

Combining the converter with drive inverters in terms of system integration is just as possible as an integration into the electrical energy storage. The type of cooling (air, water, or oil) is generally tailored to the specific application. A fully digital control and a CAN bus interface for the communication with a vehicle control unit is standard.  

We make use of the latest Si, SiC, and GaN devices. Our multi-phase concept makes it possible to shift the fundamental frequency of the DC link ripple voltage in the megahertz range, resulting in a considerable reduction of weight and volume of the passive components.

Robust and High-Speed 250 A, 450 V buck / boost DC/DC Converter for universal drive train applications.

Within the latest high power, high voltage DC/DC converter development projects power densities of more than 80 kW per litre are achieved in 850 V high voltage full SiC technology.

We build complete systems for our industrial partners, including high power and bus connectors. Integrated in a sealed housing, these robust compact devices are used in R&D hybrid cars for evaluating the electric power train.

Efficiencies of up to 99% over a wide range of load can be realized via a load-adaptive management of the number of active phases. All converter components including EMI filters, the control electronics, and the fluid cooler are generally included in our power density figures. The high power density and low power to weight ratio of our DC/DC converters make them especially suitable for demanding motor sports (KERS) and aircraft applications.

A central component of many electrified vehicles is the traction DC-DC converter. Its task is to connect and convert energy between different energy storages, battery chargers (AC chargers, fast DC chargers), drive inverters and range extending sources. In modern car architecture, weight and volume are determinant factors. To take a look beyond state-of-the art, power electronic cores based on SiC and GaN can show the highest power densities and lowest weight of DC-DC converters. These devices allow a high switching frequency of 200 kHz and in the same way a high efficiency of more than 98.5%. The high switching frequency has allowed for a dramatic size reduction of passive components leading to a record-breaking power density of up to 143 kW / dm³

Typical challenges of High Power Density Prototypes:

•     Low inductive commutation cell for fast switching
•     Integrated power modules
•     Extremely flat, small and high dV/dt driver
•     Multi phase operation for reduced ripple current
•     High performance ceramic highside capacitor
•     Small, accurate and EMI-immune current sensing
•     Low-volume, high energy power inductors
•     Integrated and optimized water cooling

In many electrical configurations, a DC-DC converter stabilizes or boosts the energy from a battery or fuel cell to the HV power net. For motor sport applications or prototype vehicles, a robust but very small and light weight power electronic is essential. Within a very short time, the IISB develops and builds up A and B style grade prototypes. These are typically controlled by CAN and provide all basic safety and power conversation functions like active discharge, basic and reinforced isolation, voltage and current control loops and status feedback.

As novel power devices emerge from research to industry, the characterization of these novel devices and their application in power electronic converters is essential in order to assess the future potential. By taking into account comprehensive characterization results for the system development, record values of 200 kW/l power density, efficiencies above 99 % and switching frequencies up to 1 MHz are not uncommon anymore.

Be our partner for innovative solutions with wide bandgap power semiconductors and participate in the future of power electronics!

Objectives:

•     Evaluation of novel devices in highly efficient power electronic systems
•     Cost reduction by system integration
•     Innovative solutions for automotive and energy transfer applications
•     Comprehensive system concepts through expertise in materials, devices, modules, and systems
•     Electrically and thermally optimized die attach technologies