It's more of a curiosity question than a real problem, but since I've run out of wall sockets again, I'd like to ask you - is there any particular reason or use case in which "wall wart" AC adapter design, like:

enter image description here

is better than a power brick, like:

enter image description here

I see those wall wart plugs almost everywhere, and they're notoriously difficult to arrange in power strips. Meanwhile, I've only seen the power bricks on laptops and one or two old gaming consoles.

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    \$\begingroup\$ Why is this being downvoted? It's a legitimate question, especially if rephrased as "if I were designing a system, which should I use and why?" \$\endgroup\$ – pjc50 Apr 2 '14 at 10:14
  • \$\begingroup\$ Please don't simply dump hyperlinks into your question. Use Markdown to properly inline images (as I've done on your behalf.) \$\endgroup\$ – Adam Lawrence Apr 2 '14 at 12:25
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    \$\begingroup\$ In the UK, some of the wall warts (e.g. uk.farnell.com/jsp/search/productdetail.jsp?sku=2289558 ) are smaller that a plug for the power brick, it's only older or higher power ones which are too big for power strips. \$\endgroup\$ – Pete Kirkham Apr 2 '14 at 12:40
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    \$\begingroup\$ @PeteKirkham: That is more a function of the size of the UK plugs, than of the size the wallwarts. \$\endgroup\$ – dotancohen Apr 2 '14 at 13:50
  • \$\begingroup\$ Duplicate of What's the reason to make power supplies external? \$\endgroup\$ – Olin Lathrop Apr 2 '14 at 14:27

They cost less to produce (1 fewer cable and connector)

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    \$\begingroup\$ Downside : they are harder to globalize : witness the odd arrangement of loose slide-on/snap-on adapter bits supplied with so many. \$\endgroup\$ – Brian Drummond Apr 2 '14 at 10:24
  • \$\begingroup\$ @BrianDrummond - Less elegant to globalise, but I'd wager still cheaper & easier to package. \$\endgroup\$ – John U Apr 2 '14 at 12:32

The wall warts are cheaper in the low watt range. That's the main reason. If you need more than "x" watts, the brick is required to get all the bit in there and to have enough surface area to dissipate the heat.

The number "x" has changed over the years, the original Commodore VIC20 used a linear brick. Linear wall plug adapters (unregulated) were limited to a few watts.

Fast forward to 2014 and we have 10W or more of regulated output easily available in a wall wart. Laptops tend to need many tens of watts, so a brick is the only way. The safety-agency-approved power cord is heavy, costs money and is relatively bulky, whereas a low voltage output cord can be thin and light.

Bulk is an important factor in electronics because sea shipping cost is inversely proportional to the number that can be stuffed into a sea shipment container (cost is not determined by weight for low density items). Lower unit cost is even more important- I have sourced wall warts in volume, but not yet bricks, but I think the bricks would increase retail price by at least several dollars.

The globalization Brian mentions is easier with bricks, but if the package is stuffed with the everything needed for a given market the cord difference still has to be accounted for at the factory. For expensive stuff, the cord may be a separate line item on the order, but that's for companies like Tektronix and Leica (two I've run into) not mass market products.

  • \$\begingroup\$ Acer at least supply wall warts with some of their smaller laptops - 40W. The one I have (for a newbook) takes advantage of the snap-in (actually a sort of bayonet fitting) country adaptor to enable rotating the rather large wall wart about the axis of the mains plug to allow the cable to come out up, down, left or right. \$\endgroup\$ – Chris H Apr 2 '14 at 13:36
  • \$\begingroup\$ I've gotten those snap on changers with a few devices now.. Handy for travel use when the entire set is supplied. \$\endgroup\$ – Spehro Pefhany Apr 2 '14 at 13:49
  • \$\begingroup\$ Yes, though sometimes they're intentionally hard to remove (Palm used to supply one that was meant to be one-time configured, the tools to change it took more space than a spare adaptor!) \$\endgroup\$ – Chris H Apr 2 '14 at 14:04
  • \$\begingroup\$ It probably took a few iterations before they figured out how to make the plug part of the adapters safe if they came off the body of the wall wart. Obvious potential for shock. The folding plug pins (eg. Apple iPad) took forever to get adopted too- they were available in unapproved form years earlier). \$\endgroup\$ – Spehro Pefhany Apr 2 '14 at 14:07
  • \$\begingroup\$ That's a charitable interpretation! Especially as they could be plugged in as supplied. I'm actually inclined to agree with you though - you would want to be 100% sure that removing the plug from a particularly tight socket wouldn't break it leaving a live part sticking out. \$\endgroup\$ – Chris H Apr 2 '14 at 14:18

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