GaN-resonant – Efficient, Highly Compact High-Frequency Power Electronics with GaN Transistors

Duration: July 2013 - September 2016
Contracting Authority/ Sponsors: Efficient, highly compact high-frequency power electronics with GaN transistors (BMBF)  
Project Partners: SUMIDA Components & Modules GmbH, Obernzell; Liebherr Elektronik GmbH, Lindau
Project Focus:
resonant DC/DC converter
© Fraunhofer ISE
New materials enable high speed frequencies: developed resonant DC/DC converter with 2.5 MHz as demonstrator for aviation applications.
© Fraunhofer ISE
Efficiency measurements for different power outputs of the highly compact DC/DC converter (V_out = 28 V_DC, f_sw = 1.8-2.5 MHz).

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) enable the operation of power electronics circuits with significantly higher switching frequencies. This can increase the power density and reduce material costs at the system level. A compact technology demonstrator was developed together with the project partners in order to show how these materials can be used to make power electronic systems in aviation applications more efficient.

The primary objective of the “GaN-resonant” research project was to develop a resonant DC/DC converter with GaN transistors, with switching frequencies significantly above 1 MHz and a nominal power of 3 kW. The project consortium achieved this goals by implementing power transistors made of gallium nitride and by the development of innovative inductive components in order to increase switching frequency while reducing weight and volume as well as production costs of DC converters. It was possible to increase the currently common switching frequencies of up to 350 kHz for resonance converters to 2.5 MHz. Thanks to the comparatively high frequencies, a large part of the weight of the 3 kW DC/DC converter could be appreciably reduced. For this reason, high-frequency power electronics systems are ideally suited for applications requiring highest power densities with low weight. The reduction in passive components also results in less copper and ferrite consumption during production and limited resources can be saved. The electrical properties of the used GaN‑transistors allows high efficiency in spite of the high switching frequency. The presented converter features a power density of approx. 3.8 kW/liter. A comparatively high maximum efficiency of 94.5 % can be achieved by the converter at a nominal load of 50 % and a switching frequency of 2 MHz. At such high frequencies, however special attention had to be paid to the printed circuit board design, the measurement and control technology and the electromagnetic compatibility.