Wait, that exists. USB is the standard. The UPS with standardized DC-outs is a USB power bank with integrated pass-through charging.

USB is kind of a physical standard. I have a few things like an alarm clock that uses USB, but I feel like the lower build quality is way more obvious than if it just had a wall wart.

The problem with calling USB a DC power standard is that it often doesn't work. I have a lot of trouble trying to charge my PS4 controller using random USB cables when it's attached to my PS4--I'm not even introducing an a/c adapter. I've had things like Qi chargers where I had an insufficient a/c adapter so they behaved poorly. If I'm at an airport and need a quick charge on my phone I'm definitely not going to use their USB port because if it works it'll likely charge slowly.

USB-c is worse with all of this. With a/c power it's only an issue when traveling to other countries and in many cases a physical adapter is good enough.

Slightly OT, but have you managed to actually find an acceptable quality USB power bank (PD/Type C or otherwise) that actually supports this "UPS mode" of operation? Most of the one I have tried cannot simultaneously output and input, or introduce a second of switching delay in between.

Some discussion about pass through charging on the Anker forum boards [1]. Pretty much everyone I know who carries a power bank only remembers to charge it at the same time they want to use it, so pass through charging capitalizes upon this consumer behavior to use the power banks more frequently.

The possible dark pattern I see operating instead is manufacturers are opting to ship power banks charged up to the retail shelves, and likely don't mind if people keep buying more new units because they can't wait for the units they already have to charge up?

I tend to keep all my gear plugged into chargers whenever I'm stationary because I know all of them have charge protection circuits and I have a work profile closer to that of a digital nomad than an office-worker, so I'm an outlier with that common consumer behavior of only charging when one must.

[1] http://community.anker.com/t/any-powerbanks-that-allow-drain...

also POE

> A better solution would be to get everyone on board with a single DC voltage and connector

Why? For many things 6V is enough as it will downscale without too much loss to 5V/3V3 which is what most electronics run on... but everything that draws a boatload of power (computers, laptops, LED strips, ...) will go on 12V up to 24V, so if you want a standard it's either 12 or 24V which will introduce a lot of regulation waste in the form of heat in the device.

Why? Routers, switches, small embedded computers, and a myriad of devices already use 12-24V DC and step it down internally to 3.3V or less for chip use. Laptops and even phones/tablets are no different. And conversion losses don't increase with voltage so long as you design your DC-DC converter properly.

5-6V is fine for small loads of around 10 watts but you then have to deal with line losses. A 5 m / 16 foot 24 AWG usb cable will lose 38.5% of its power from line losses at 5V, 2.5A (a measly 15 watts). If you wanted to get a low 2-3% loss for 5V, 2.5A at 5m cable length you would need 12 AWG which is massive. 24V does better but if you wanted 50+ watts you again have voltage drop issues.

So in conclusion, low DC voltages are not very practical for power cable runs of over 2 meters. Though it would be nice if the last meter could be more unified with a single DC voltage and connector (my vote is for 24V). Then we can consolidate multiple devices to one strip/brick and call it a day.

That's true. My aging but still well-functioning WRT54G router had its 12V 2A wall wart die on me last year. At the same time, some USB cable had its micro B end accidentally ripped of.

So I thought, why not, opened the router,and lo and behold, the DC circuit is perfectly happy with 5V and 1.2A or so, and converts it down to I believe 3.3V.

So I drilled a hole in the router and soldered the working end of the damaged cable to the power input. Other end is pluggend into the useless USB TV port. Has been working fine ever since. Neither TV nor router runs hot, which I couldn't say about the old wall wart.

In theory, USB should negotiate the required amount of power It turns out the TV manufacturer decided to simply wire the port directly to the internal 5V rail connected to both USB ports, so it should be able to give at least 2x2A.

Yeah, it was probably cheaper to just buy a new router. Got a bit nerd-sniped there I guess ;-) .

Should've let this thing die. Do you actually have devices hooked up to this.. the speeds you're getting and the likely security holes you have (especially if you don't have this properly behind some other device) are concerning me.

Dont worry, there is a decent enough firewall built in to the ISP modem. And my ISP is more than slow enough that the speed of the router doesnt matter much. And when all my computers are off, so are the router, the modem, the TV and all the other stuff.

Assuming you mean 5V or 3V DC, there will have to be a baseline level, then it will have to be upconverted or downconverted from the wall AC is (to whatever their baseline standard is in DC), then converted back to AC by X-converting then converting to something in AC, then downconverting to DC OR using semiconductors that used to be expensive (don't know if they still are). Seems complicated. Why not just stick with (in the US AC @ 110V - it's not like it isn't wide spread) and let all the device power adapters take care of themselves?

Or, you know, have better silicon components give us SDVC (Software Defined Voltage Control). I'm joking, but I also don't think you will save what you thik you will in TCO - Energy Savings + Device Cost differential.

I could be wrong. I have been before. And I am operating on almost zero sleep for over a day, so odds are, I could be doing to again at greater than my average error rate.

The problem with starting from a low voltage is that even low power levels result in significant current requiring the use of large conductors - or at least a connector capable of supporting those conductors when needed.

Every device has a high efficiency switching regulator in it now. Regulator drop is not the issue.

Wouldn't it be more efficient to have e.g. one DC power supply for the house that can power everything that needs DC power, instead of lots of individual (and likely cheap/inefficient) power supplies?

Most electronic devices require low voltage DC, so resistance losses in cabling across even quite short distances (10+ metres) would be significant. This is why DC distribution in data centres if it is used is normally 48V.

It’s also more difficult do do straight transformation on DC voltages, it can be done but the reason our power grid settled on AC was getting high voltage transmission levels down to reasonable ones for use is simple with some wound coils.

It’s really easiest to just keep everything AC until the point of use, putting a transformer and a bridge rectifier in most devices is a better solution than needing switching power supplies everywhere to convert DC voltages (or wise options like linear regulators).

Switched mode power supplies also have EMI to deal with due to the higher switching frequencies, an AC transformer runs at line frequency (50/60Hz).

Dumb DC supplies using just a bridge rectifier and filter cap(s) isn't really ideal if you need a stable voltage. If the mains voltage sags, so does output. Then factor in ripple from the cap bank under higher loads and the associated nonlinear harmonics and power factor issues from the rectification. You could add a linear regulator and increase the transformer output and burn the excess off as heat but efficiency goes down the toilet.

Switchers, for all their complexity, are pretty damn clean in terms of output and input PF correction. Even in audio and sensitive analog applications where dumb supplies were preferred have been replaced by switchers. A good design goes a long way and it's unfortunately easy to design junk switchers because of the complexity involved.

EDIT: Most consumer appliances will still need there own power supplies. You would still want a last step DC transform to house at a high voltage. If the appliance operates at the voltage DC then it would need no power supply.

Yes, and cheaper to build!

You can achieve the same efficiency with DC and AC do not directly effect efficiency across the line contrary to popular belief. It is simple about what the voltage across the line is.

AC was in because it allowed us to build transformers to up and down voltages to provide efficient across the line.

Nowadays, we can build DC transformers with Power MOSFETs which are cheaper, and more efficient then there AC counter parts (old [magnets and inductors] and new [You can do AC transformers with MOSFETS with some extra steps/components]).

Additionally, since most consumer appliances first step is to rectify the voltages most build in the past two decades are DC compatible. Additionally, newer ones could then drop the rectifier stage and become cheaper and more efficient.

>Yes, and cheaper to build! You can achieve the same efficiency with DC and AC do not directly effect efficiency across the line contrary to popular belief.

In fact there are higher loses with AC power transport (specially in long distances) due to the parasitic capacitance of the lines, that’s why some countries use DC power transport lines now.

Line losses, see my reply below. Once you go beyond needing 10-15 watts and cable lengths beyond a few meters you start losing a lot of power through the wire.

The problem is the resistance of the wires which causes a measurable voltage drop. Try extending a USB cable 10 meters to have an idea.