Half-bridge circuits are the core of many voltage converters. These converters are the link between voltage supply and consumers – and they are becoming more widespread due to the increase in the number of electrical devices. The energy transition and e-mobility are also increasing the demand for reliable and, above all, efficient and compact voltage converters of all kinds.

Technical innovations for half-bridge circuits

The half-bridge circuit developed by the Fraunhofer Institute for Applied Solid State Physics IAF is designed for the 600-volt class, which is a standard for various devices ranging from tablets and washing machines to the electric car. This circuit was the first time that several high voltage components could be combined monolithically on a single chip. This allows for particularly small and powerful voltage converters. In tests, it was possible to increase the switching frequency to up to 3 MHz at 400 V input voltage, which is about ten times the frequency of conventional circuits. This also considerably reduces the effort required for packaging. “This is very important in areas such as e-mobility, where many converters which are as efficient as possible have to be fitted in very little space,” says Richard Reiner, research associate at Fraunhofer IAF in the Power Electronics business unit.

The basic material, the semiconductor gallium nitride (GaN), is cost-effective to manufacture and offers excellent performance figures compared to the competing power semiconductor silicon carbide. The GaN technology used has already proved itself with powerful transistors, diodes, and monolithically integrated GaN circuits.

Potential uses in e-mobility

Based on the new half-bridge circuit, the smallest and most efficient on-board chargers possible are now to be developed. These will allow electric cars to be even lighter and more economical in the future – which is exactly what automobile manufacturers and users are looking for. The compact design also improves the electrical switching characteristics by, for example, reducing line impedances. Integrating additional sensors, such as thermal monitoring systems, also allows optimized operation.

“This innovative approach brings a new level of power density, efficiency, robustness, functionality, and reliability to e-mobility,” explains Dr. Patrick Waltereit, deputy head of the Power Electronics business unit at Fraunhofer IAF.

Fraunhofer IAF last publicly demonstrated its monolithically integrated half-bridge circuit at PCIM Europe in May.