Floyd L. Davidson wrote:
David Maynard wrote:

Floyd L. Davidson wrote:

That's true if it's unregulated but the voltage change with a
regulated supply is negligible.

That would depend on the regulation,

Not really. If the voltage significantly changes then it isn't
'regulated'. That's what the word means in this context.


Yes *really*.

No, 'really'.

"Regulation" is not specific enough. Some of
regulators are better than others. Just saying "regulated"
means zilch. And just saying the voltage changes means just
about as much! How well regulated can be specified, and how
much voltage changes can too.

Yes, it 'can be specified' but we're not talking about the Vcore regulator
to a processor. We're talking about a wall wort and it's nonsense to
contemplate an 'unregulated' regulated wall wort.

We could also discuss how much ripple the unregulated wall wort is
specified to put out at the specified current because there's the potential
for a heck of a lot more variance in that than there is in the typical
regulated wall wort.

but regardless... I've
never seen a regulated wall wort.

There are lots of 'em, even in the traditional 'wall wort' form
factor. Even more common in the brick form factor.


They are *rare* in the wall wort form, despite you knowing of an
exception. The vast majority of wall worts that readers of this
thread will ever see are *not* regulated.

First you claimed you hadn't ever seen any, implying they don't exist, and
now you want to argue 'percentages'.

Perhaps I missed it but I don't recall it being said that the 'ac adapter'
in question was even a 'wall wort'.

Here's the package outline for Power Stream's selection in 15 watt wall
wort switchers in both end and side mount plug, plus brick.

http://www.powerstream.com/Zdraw.htm

And the specs for them: http://www.powerstream.com/Zdraw.htm

A regulated wall wort in the power range being discussed would
likely be a switcher rather than linear.


Typically that isn't done. The switcher is inside the
equipment, and the wall wort amounts to little more than a
transformer with a diode bridge, and might even have a
capacitor.

That's certainly one way to do it. It's also not unusual to put a small
switcher in the wall wort because, as the power levels go up, it's plain
cheaper than a transformer. It's also more efficient with less weight, less
bulk, and less heat.

It's good engineering practice, as it allows a variety of
"power supplies" to be used.

It may or may not be an advantage to allow a 'variety of power supplies'
since a manufacturer usually knows what power supply they're providing.

Personally, I don't see why
anyone specifies a DC power supply anyway! They should move
the rectifier and capacitor the equipment, which allows the
wall wort to be AC or DC, and if DC it can be any polarity.
That's nice flexibility.

And some do it that way too. One could also argue that if you're moving
everything else into the unit then you might as well put the transformer in
it too.

It depends on what one is trying to accomplish and what the device is for.
If it's 'portable', as one example, then moving as much as possible into
the external adapter removes bulk and weight from the portable device and,
again using the portable example, there's little reason to carry around the
transformer, rectifier, filter, and regulator when it's running on batteries.

A fixed device, like a router, doesn't have that particular consideration
but there are others, such as case size and internal heat dissipation, but
I'm not going to debate the wisdom of D-Link design engineers as I don't
know what design criteria they were handed.

I don't feel like bringing the network down to put a meter to it
but I'd bet the 5V 2.5A wall wort to my D-link 614+ is a
switcher because I don't see any way a 12.5VA transformer could
fit in the 1.75x2.25x1 inch case, plus there's no weight to it,
and the model number, SMP-xxxxx, looks suspiciously like an
engineer's "Switch Mode Power" supply acronym.


However, the fact that one such unit exists doesn't make it
common,

In the first place, I checked that particular unit because I just happen to
have a D-Link (wireless/LAN) router and the device under question is, tada,
a D-Link router, albeit a different model so one cannot assume it's the
same. But it certainly shows that at least that one class of equipment, by
the same manufacturer, employs a regulated wall wort.

My D-Link 8 port switch uses a regulated adapter too, as do most notebooks
in brick form, and I'm sure I could find more if I wandered outside the one
room.

Oh wait, the PDA is on a 5V 2A wall wort switcher (clearly labeled as such).

nor does it mean using it as a general example to
describe the functionality of wall worts is a good idea.

My point was that your comments were too narrowly focused on
specific equipment

Well pardon me for looking at a piece of equipment of the same type and
manufacture as the one in question.

that did not represent a broad enough view of
what the OP, or others reading this thread via google searches
next year, might be actually seeing.

You're arguing a straw man as no claim was made about 'how many' wall worts
are regulated. Just that your absolute, 'they are all this way', statement
that voltage will universally increase as load decreases is not true with a
regulated power supply.

And "others reading this thread via google searches next year" had better
hear that regulated wall worts do, in fact, exist because replacing one
with an unregulated wall wort isn't going to work worth spit.