ITU suggests replaceable cables for power supplies

Obvious answer.

USB. Mandate USB power, power block terminates in a USB A socket, device cable is USB A plug to whatever.

Quite common already and thus pretty much the de facto standard. All that's required is USB supplies capable of chucking out sufficient oof to satisfy larger devices.

USB power delivery spec allows up to 100W, which should be enough for phones, tablets and laptops.

USB power delivery spec allows up to 100W, which should be enough for phones, tablets and laptops

What???????

"The Battery Charging Specification 1.2 of 2010 [12] makes clear, that there are safety limits to the rated current at 5 A coming from USB 2.0. On the other hand several changes are made and limits are increasing including allowing 1.5 A on charging ports for unconfigured devices, allowing high speed communication while having a current up to 1.5 A and allowing a maximum current of 5 A."

Now at 5v that ain't gonna give you 100watts

PSUs

Nice idea; most of us have boxes of Wall-Warts for dead equipment. We are able to wield soldering irons better than many, I expect. Some good work has been done already in adopting figure-8 for input and now we need a standard for DC output cables. But not USB, precisely because it already has a power rating too low to be good. Then what to do about the current rating at each voltage? Mustn't overheat them. ??

USB @ 100W (maybe) vs Power over Ethernet at 25W (maybe 50W)

There's an overcomplicated 2012 proposal for USB to be extended to provide up to 100W, as reported in various places e.g.

http://www.theregister.co.uk/2012/07/23/100w_usb_power_delivery_specification/

For 25W or so, which covers a great many things, surely power over Ethernet is tried, tested, proven, and could be cheap as chips? 25W you can do using industry standards, some vendors claim 50W using proprietary extensions but that way lies danger.

While they're at it...

How about the other end of the connection? It's a sod of a job to sort out a laptop where someone has used the "Wiggle the cable until it works or something crunches," technique and snapped off a jack directly soldered to the main board. Imagine my joy when I got at the guts of my elderly Tosh laptop the other day and found not only that it was on a tail, but also had a pair of redundant wires.

This WON'T be popular. Certain laptop vendors I can think of, like selling laptop power supplies with a healthy mark-up.

I hope it happens however.

As Mr Fuzzy points out too, sort out the charging port end on the low voltage side. I echo the joyous sentiment of ordering a replacement laptop DC jack and finding that it has a tail and connector rather than requiring soldering. My own idea is that the plugs on laptop power supplies come away from the leads easily. Somewhat like the multi-voltage power supplies you can buy with the 2 small pins making the connection to the plug of choice.

Then when your hapless victim kicks the low voltage portion of the power supply, the plug is left in the charging port and the lead falls to the floor/

I suppose magnets could be used for this too, unless someone has patented that idea of course!

With EU support, this could be a runner.

Careful design of the DC output connector would be required to support different voltages, single and double-ended, maybe communicate the required voltage and current limit to the brick.

A new market in universal power supplies could be born, devices shipping with just the cable. One 8-way brick on the charging table at home, portable single-way for mobile use, power out socket in you car...

forget the itu

This needs to be mandated by the EU.

there's no need for all the different voltages we have now just have 2 or 3. Small devices like phones, cameras and tablets can use 5V which can be supplied via a USB plug. Larger devices like laptops can use 19V with a large coax connector. If a large coax connector isn't the best design make something flat but make sure it fits in both ways round. Maybe have a middle voltage like 12V for routers, battery chargers and anything else.

Make all cables detachable, make all PSUs sold meet strict efficiency requirements. Make the PSUs universal, sell them as single, dual or tri voltage. Tri voltage PSUs can do all 3 voltages, single can just do 5V. For the multi voltage PSUs make them able to automatically choose the correct voltage based on the attached cable.

what about tablets

The ITU and EU should force a standard plug and socket for tablets also!

We' had EU standads for mobiles...

Unless you are Apple, in which case

* All connectors have to be at least 25% smaller than the standard

* They can only have one prong.

"But using a physical USB connector for supplying a non-standard voltage and current is just asking for trouble."

Not really - the PSU supplied with the Asus Transformer range of tablets has a USB 3 socket on the wall wart - if it detects a Transformer it supplies 15V, fails to detect a Transformer the same socket supplies 5V.

The only trap for young players is that if you want to insert a USB extension lead in the middle it needs to be a USB 3 cable to support the Transformer detection process, otherwise you just get 5V out.

Loupes, loops, and RF noise

All part of sensible product design. For many years -- a couple of dozen, anyway -- leading Japanese Amateur Radio makers used the same 6-pin power connectors for HF radio transceivers..Granted, "wall warts" don't have to deliver 25 Amperes, it'd be d*mned useful not to need a jewelers loupe* to see what polarity and voltage thw PS label shows. *(And how about letters more than 0.3mm tall?)

I'd insist, however, with efficiency standards now pretty much mandating switch-mode power supplies, that RF emission (>9 KHz) be kept well below the EN 55022 and FCC Part 15 limits; what is the sense of a power supply that renders a radio it powers (and others nearby) unable to hear radio stations?

For examples of testing, limits and design tips see www.analogzone.com/pwrt0628.pdf