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Comment by xxs | Hacker News Reader

48V -> 1V (for the cpu) would be super extra funny, though. The power stages would need to be high voltage mosfets. No idea if a single conversion 48 ->1V at 400A+ would make any sense.

Also the capacitive coupling for 48v is quite more dangerous.

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https://www.princeton.edu/~minjie/files/jaeil_apec20_paper.p... People are waaaay ahead of you. The 48V -> 12V -> ~1V is apparently less efficient than a 48V -> 1V even with the really high step down ratio.

Note that the paper you linked is still doing a two-step conversion - they essentially just removed the capacitors between the two steps. It doesn't do 48V -> 1.5V, it does 48V -> 8V -> 1.5V. They even specifically point out the downsides of single-stage conversion topologies.

"It leverages the high performance of low voltage DrMOS devices and multiphase buck control", drmos is driver and mosfet.

Like mentioned (by a sibling comment), it's not a single conversion, but the efficiency is not the prime issue regardless - it's the reaction time and the voltage sag. Load insertion causes the voltage at the CPU (inside) to drop and be significantly lower than the one measure at at the VRM, due to losses at such high currents.

The lack of voltage simply causes the systems to crash.

DC has zero capacitive (or inductive) coupling.

You convert it to a lower voltage by switching it on and off very rapidly and smoothing out the result. That's going to behave a lot more like AC than DC.

The VRMs work at 100KHz-1MHz, they are not pure DC. When it comes to "reactance", it's orders of magnitude worse than the well-known 50/60Hz AC.

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