Institute of Robust Power Semiconductor systems

Power Semiconductor Integrated Circuits and Modules

The ILH conducts research in High power density power modules for switched-mode converters in eMobility and renewable energies.

The Trend in Power Electronics

Power electronics enables applications such as electromobility or renewable energy conversion. In particular, high electrical efficiency (low losses) in combination with high power density (compact size) and low cost are crucial. A further requirement for power electronic systems is a high degree of robustness with respect to EMC and reliability. For these reasons, the trend is towards higher switching frequencies, more compact systems and efficiency optimization. This is made possible by the use of novel semiconductor materials having a large band gap, for example silicon carbide (SiC) and gallium nitride (GaN). In order to promote this trend, the research at the ILH focuses on areas as outlined in the following.

Full bridge consisting of 1200V SiC MOSFETs integrated with gate drivers and bootstrap supply on an AlN DBC for low inductive DC / DC converters up to 2kVA. (Cooperations: Rogers Germany GmbH, Robert Bosch GmbH)

Characterization and Modeling

Characterization is the first step to properly design power electronic circuits. A good knowledge of the semiconductor devices enables the optimal utilization of the devices capabilities in the application. The work at ILH in the field of characterization is focused on semiconductor devices based on novel wide-bandgap materials such as GaN and SiC.

Modeling is an important aspect to predict the behavior of electronic systems in simulations. This enables the optimization of the circuit during its design phase prior to the first prototype building.

An accurate simulation requires a detailed model which describes the transistor behavior in all operation regions. Moreover, transistor models must also ease the circuit simulators' convergence and be computational efficient. The ILH concentrates research on development of equivalent circuit based transistor models for SiC and GaN power devices.

Temperature dependent measurements of the static and dynamic current/voltage (IV), capacitance/voltage (CV) and charge/voltage (QV) characteristics up to 2kV and 2 kA are the base for parameter extraction for circuit-oriented modeling of power semiconductor transistors.

Integration, Packaging and Assembly Technology

High power density and high switching frequencies impose stringent requirements on packaging technologies. By appropriate approaches such as 3D packaging, parasitic effects that are caused by packages, substrates and layouts, can be systematically influenced and reduced. Due to compact hot spots, heat spreading and heat dissipation are more important than ever.

2kVA SiC MOSFET full bridge DBC module soldered on a PCB for low-inductive connection of the DC link targeting higher switching frequencies. (Cooperations: Rogers Germany GmbH, Robert Bosch GmbH)

Efficiency, Power Density and Robustness

Increasing the electrical efficiency of power electronic systems enables e.g. increased ranges in electromobility or higher profits in renewable energy conversion. One approach to reduce losses is the usage of novel semiconductor materials (e.g. GaN, SiC). These materials have superior physical properties compared to silicon-based power semiconductors. Another approach is to increase the slew-rates in power converters to reduce switching losses.

Increasing the power density results in smaller passive components, smaller system components and thereby in potential weight, size and cost advantages. Approaches to increase the power density are the hybrid and monolithic integration of gate-driver and power converter circuits, as well as active and passive components.

To ensure robustness of the systems, the thermal behavior and EMC of power modules is studied and optimized.

Gallium nitride based quasi-normally-off gate driver and boost converter (300V/12A) with 600V AlGaN/GaN HEMTs, AlGaN/GaN Schottky-diodes and buffer capacitors- hybrid integrated on DBC power module. [link] (Cooperation: Fraunhofer IAF)
This image shows Ingmar Kallfass
Prof. Dr.-Ing.

Ingmar Kallfass

Institute Director

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