Page 24 - PEN eBook December 2022

Design POWER SUPPLIES

a 48-V architecture. In particular, the combination of GaN technology featuring chip-scale packaging,
such as those of eGaN transistors, and carefully designed magnetics allows 1-kW load capability at
1-MHz frequency with peak efficiencies and full-load efficiency of 96.3% and 93.8%, respectively.

References

▶ de Rooij, M. and Negahdari, A. (2022). “Beyond 4 kW/in3 Power-Density for
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48 V to 12 V Conversion using eGaN FETs in an LLC DC-DC Bus Converter.”
PCIM Europe 2022; International Exhibition and Conference for Power

Electronics, Intelligent Motion, Renewable Energy and Energy Management,
pp. 1–9, doi: 10.30420/565822013. Putting the Power

▶ de Rooij et al. (2021). “A 1 kW eGaN FET-based LLC Resonant Converter
2
in them 1/8th Power Brick Size for 48 V Server Applications.” PCIM Europe Supply User in Control

digital days 2021; International Exhibition and Conference for Power
By Caleb Lander, senior product manager at XP Power
Electronics, Intelligent Motion, Renewable Energy and Energy Management,
pp. 1–8.
Traditionally, AC/DC power supply designs could only be optimized for specific load and line conditions.
▶ Ahmed, M.H., Lee, F.C., and Li, Q. (February 2021). “Two-Stage 48-V VRM This stems from classic analog control and simple pulse-width–modulation techniques at a fixed
3
With Intermediate Bus Voltage Optimization for Data Centers.” IEEE Journal of frequency that has been commonly used, and those constraints typically result in higher component
stresses at the extremes of operating ranges. Datasheets for PSUs often showed heavy derating with
Emerging and Selected Topics in Power Electronics, Vol. 9, No. 1, pp. 702–715,
low input voltages, and outputs were limited to fixed values that could be adjusted by perhaps ±10%
doi: 10.1109/JESTPE.2020.2976107.
at best. Operation adjustable down to zero output voltage and true, accurate constant-current output
▶ Huang, D., Ji, S., and Lee, F.C. (August 2014). “LLC Resonant Converter With were typically confined to expensive laboratory supplies that did not have to be particularly compact
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or efficient. Similarly, characteristics like control-loop response, reaction to overloads, and thresholds
Matrix Transformer.” IEEE Transactions on Power Electronics, Vol. 29, No. 8,
of fault detection were “baked into” the design along with any control and monitoring signal levels,
pp. 4339–4347, doi: 10.1109/TPEL.2013.2292676. functionality, and polarities.

▶ EPC. (2021). “EPC2218 datasheet.”
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The result of this has been that users have had to work around available power supplies, find the
▶ uPI SEMI. (2021). “uP1966E datasheet.” best compromise, then stock various types for different products. For established end products,
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upgrades and changes could be limited to what the power supply would allow; even the need for a
▶ EPC. (2021). “EPC2067 datasheet.”
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small adjustment to output voltage could entail a major re-specification of the power system design.
▶ Texas Instruments. (2018). “LMG1020 datasheet.” Many applications also specifically require the PSU to be variable in some way, LED constant-current
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loads often need to be dimmable, or the output voltage to an electrolysis process might need to be
▶ Hitachi. Material characteristics of ML91S.
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programmable to determine a reaction rate. In these cases, the solution has often been an expensive
custom design.

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