A highly efficient compact 200 MHz GaN buck converter module for point-of-load applications
Fig. 1. Realized VHF converter module; size: 20 x 20 x 3 mm3.
Fig. 2. Fabricated GaN converter chip in demonstrator with bond-wires and on-chip soldered SMD components; chip area: 2.5 x 1.7 mm2.
The introduction of the new 5G or even 6G communication standards, together with the shift towards Industry 4.0 and the Internet of Things (IoT), is leading to a massive increase in data that needs to be managed and processed. This trend is fueling demand for ever-larger data centres and, consequently, immensely higher energy consumption. Moreover, the demand for greater compactness and higher performance has risen massively. One of the most critical components in the distributed power architectures of data centres are the DC/DC (buck) converters to supply the point-of-load (PoL).
To meet these demands, we realized a novel, highly efficient and compact GaN-based buck converter operating in the very high frequency (VHF) range up to 200 MHz. The module includes a GaN half-bridge converter monolithic microwave integrated circuit (MMIC) with integrated drivers, on-chip soldered SMD caps, and inductors to maintain shortest connections. Together with the hybrid low-pass output network (air-core inductor, SMD cap), the chip forms a buck converter with synchronous rectifier for efficient and compact power supply of points-of-load in data centers.
The very compact GaN buck converter MMIC (which drives the integrated 10 mm half-bridge power stage GaN-HEMTs) and the hybrid output network are mounted on an AlN single-layer carrier heatsink for optimized power management. Both the GaN chip and the AlN carrier were fabricated in FBH’s cleanroom. In addition, we have introduced new mounting technologies – like 3D integration of a “capacitor bridge” across the power stage or SMD soldering on the GaN chip to minimize inductive loops – enabling reliable operation at the unusually high frequency of 200 MHz for power converters.
At 200 MHz switching frequency, the buck converter achieves a power conversion efficiency (PCE) up to 71 % for 32 V DC input voltage (Vdc_in) operation. At 22 W DC output power, an output voltage of 13 V has been reached. At 100 MHz, the PCE peaks at 80 % for 29 W conversion from 35 V to 14.5 V. For the maximum 38 W conversion to 19 V (48 Vdc_in), the PCE still reaches 75 %.
Our GaN VHF buck converter module is an important first step towards optimized power supplies for points-of-load in future big data centers.
This work was funded by the Deutsche Forschungsgemeinschaft (DFG) in the framework of the focused program on Energy-efficient Power Electronics “GaNius” (SPP2312) under grant no. WE6288/7-1. Further, it was partly funded by the German BMBF within the “Forschungsfabrik Mikroelektronik Deutschland (FMD)” framework under ref. 16FMD02 as well as within the project “GreenICT@FMD” under ref. 16ME0505.
Publication
T. Hoffmann, D. Sun, S. A. Chevtchenko, M. Wolf, L. Schellhase, A. Wentzel, “A Highly Efficient Compact 200 MHz GaN Buck Converter Module,“ in: Proc. 54th European Microwave Conference (EuMC) 2024, pp. 1046 - 1049, Paris, France.