I'm curious if USB could be turning into the next electrical socket. Imagine if everything you plugged into a wall outlet used USB. Not only would it probably be safer, but it would probably mean the end of country-specific electrical adapters. Outlets like this are already becoming popular: http://www.amazon.com/Newer-Technology-Power2U-Outlet-Chargi...
Probably not. The 5v ones can't deliver enough power to do much, and if you have 20v you might as well have 120v - you anyway need to convert the voltage to whatever you use internally, and with 120v the wires are 1/5 the size (thickness).
I find that argument suspect when I look at all the laptops that run on 19 volts. Internal adapters are a lot messier for 120v. Most computing things love the 12 volt range, my screen uses 19 volts, a fancy light bulb is either LED and low voltage or CFL and gets no benefit from 120.
Higher voltage is better for distribution and for very high power loads (including heaters). But a lot of things like low voltage.
Why do you say that? Look at any USB charging plug - very simple inside. You only need "messy" electronics for high power or high (above 80%) efficiency.
Basically you would need 20v -> 5v vs 120v -> 5v - there isn't really a lot of difference. (There is some, but not enough to make changing everything worthwhile.)
Also, the double conversion isn't great (you would need a power supply in each plug), assuming typical 80% power supplies you would end up with end to end 64% efficiency.
>> Internal adapters are a lot messier for 120v.
>Why do you say that?
Well, for starters, most for-profit enterprises like to avoid liability. 20 V things are considered "low voltage" for regulatory purposes while 120 V things are considered "high voltage." That has certain implications for how you have to electrically insulate your portable device.
Then you also have to consider the difference between AC and DC. A power supply meant to connect to the wall has to have an energy storage device (usually a capacitor) for the 120 times per second that the wall delivers no energy.
Designing and manufacturing a device to power from 20 VDC (+/- 10% or so) is amazingly easier than one that must slurp 120 VAC.
>Basically you would need 20v -> 5v vs 120v -> 5v - there isn't really a lot of difference
This is completely wrong. 120 VAC is 120 V RMS, which has peaks of +/-170 V. Go to digikey and compare the price of 340V capacitors to 40V capacitors. Then consider the fact that your low voltage capacitors only need to filter relatively high-frequency ripple and occasional step-loads, while your high voltage caps need to supply energy when the wall isn't (so they needs to have much more capacity).
Having a centralized efficient 20v transformer could actually lead to better efficiency overall. A low voltage DC-DC converter can be far above 80% efficiency without any fancy components.
And when I called 120v adapters messy I meant for the kind of thing I see that runs off 20v. Relatively high-powered computers and game consoles and monitors.
A centralized transformer wouldn't work well. First you would have to run a lot of very fat wires in order to serve all the outlets.
But worse, power supplies have an optimum efficiency, usually at around the 75% usage point. If you have a power supply large enough to power everything, it's not efficient enough to power just a few things.
> And when I called 120v adapters messy I meant for the kind of thing I see that runs off 20v. Relatively high-powered computers and game consoles and monitors.
And I still don't see what's messy about it. Those things would anyway need a power supply to convert the 20v to whatever they use. You could just as easily put in a 120v power supply (and use thinner wires).
Those things tend to have bulky external power supplies that transform 120 volts into 20. 'whatever they use' is already 20 volts, with minimal internal components to get any other levels. You'd be able to eliminate a lot of awkward transformers.
It's probably not worth wiring a whole house with fat wires but in theory having nice safe universal plugs without dealing with external transformers would be nice.
I'm sure if someone wanted to design a supply that's efficient at different currents they could. Worst case would be 2-3 different supplies glued together with a management chip.
