[eksu]

this is a computer not a car, 48v seems overkill and dangerous.

components use 12v, 5v, or 3.3v in pcs currently. why do the step down from 48->12 instead of running 12v naturally? 12v is also what is used by the most power hungry components of a PC (GPU).

[epcoa]

> 48v seems overkill and dangerous.

In fact the exact opposite is true, it is safer in practice. In a true fault condition into flesh the currents involved aren’t substantially less safe (4x microamps is still microamps). With protection circuitry and current limiting, the permitted currents are that much lower, which is easier to deal with.

[hulitu]

> With protection circuitry and current limiting

which are cut because of costs.

[jauntywundrkind]

48v seems vastly safer. There's 1/4 the thermal heating for equivalent power. The new high density 12VHPWR connector for GPUs has been melting down & had to get basically redesigned. That would not have been a problem at all on 48V.

There shouldn't be an intermediary step down to 12V. Google's been doing direct step down from 48V->~1V with GaN fets for half a decade, which is vastly more power efficient than the two step 277V->12->1V that many server systems go through.

It'd also be amazing to have usb-c extended power (48v) be something we could just add for free, essentially. (Alas this is complicated by needing to step down to lower voltages too, necessities some semiconductors in the delivery path to usb-c, which would have some voltage drop. This strongly implies to me something more like 52V or 54V would be ideal instead of 48V.)

For anything that typically runs under 100W, I agree that 48V is ridiculous. But I would love love love to see some motherboards for ThreadRipper that have GaN fet for direct conversion from 48V, or stuff like that. It'd be pretty niche. But it should be an option!

One of the big potential winners could be people with solar; being able to run your system directly off your solar bank would save double digits percent of power, versus inverting then converting back.

You're right that in the immediate term we'd see a lot of intermediary conversions. I'd love to have a better game plan, for not just motherboards but other components to expect either 48v or wider voltage inputs. Non-trivial to support 10-60V but if that was a market expectation & not a niche need we'd see very affordable solutions spring up practically overnight. There's already a range of usb-c focused power converters that are exceedingly cheap that could step in for this need!

Edit: seems like Google is using two stage conversion primarily, but not necessarily 4:1 48V:12V. Their fixed ratio converter seems to have a 6:1 mode (8V) target as well, or be configurable for even bigger ratio (they said up to 12:1 in their talk). As of 2019, a bit of change of tune from original 2016 ambitions. Good talk? https://youtu.be/aBkz2JR4UVs

[cactacea]

48V DC is completely safe and not dangerous whatsoever

[hulitu]

As a computer, i find your trust in technology, amusing. /s

It depends on the current. Your 48 V suppply won't supply microamps, but Amps.

[dist-epoch]

The most power hungry component, the CPU, uses 1-1.5v.

The GPU voltage is also step down to 1-1.5v by graphics cards VRMs.

[connicpu]

Power regulators that can efficiently produce the 1-1.5v output with the most minimal noise generally have lower maximums on their input voltage as well. In designing some of my own IoT devices I've looked into a fair number of power regulator ICs and 36V is a common maximum input voltage. The efficiency curves on the datasheets also usually show the efficiency gets lower the higher the input DC voltage. In a power regulator, inefficiency means even more heat you have to dissipate, not great in a GPU. I'm sure the GPU would love to take even lower voltage if it could, but 12V is the compromise we've decided on to get decent efficiency without requiring insanely thick conductors.

[photonbeam]

usbc can do 48v, its not that dangerous