iPhone charging adapter - how can it be so small?

[shadewind]

I'm a bit new to power supply design so all the mains powered designs I've seen so far have been using a transformer. But the iPhone charger that I have is so tiny and light. Can there really be a transformer in there or is it some other design? It supplies 1A @ 5V.

If I didn't need it for my phone, I'd take it apart

[VIPR]

Sounds like it implements a small switched mode using a high frequency so as to also use very small surface mount inductors. It's pretty easy to get an impressive power supply in a really small space with the newer technologies.

[the_raptor]

Most modern power supplies are switching style. Even "cheap chinese rubbish" products come with switching supplies these days. In general, to me, using non-switching power supplies marks the product out as old or really crap.

Also USB compatiable chargers are pretty generic and easy to get. In fact I have one for a radio that I don't need (it uses the same charger as my Nokia) that I will take apart and photograph tomorrow if I remember.

[the_raptor]

I got bored and cracked open my cheap chinese USB charger.



Wow this soldering is what I would describe as "fuck awful".



I am glad I never plugged this piece of shit in.

[VIPR]

Looks typical for a cheap Chinese product. They certainly could have done a better job of washing the board after the wave solder job. I've seen much worse though. However, I guess for the cheap price one can't complain too much.  I'm sure it works just fine.

[the_raptor]

Well the whole UHF radio was $30 with this charger so it was definitely cheap.

The radio was a great bargain but there is hardly any amateur UHF activity around here so I invested in a more expensive dual bander.

[shadewind]

That's it's a switching power supply I already assumed. But don't these need a transformer still? Is it just a very small transformer?

It's one of these: http://www.gadgetnuggets.com/wp-content/uploads/2010/02/iphone_charger.jpg

[Simon]

A switchmode works by making the mains AC into DC and then making it back into AC at a higher frequency and then putting it through a transformer. The higher frequency you use the smaller the transformer required. In phone chargers and the like the transformer is so small you can confuse it with an inductor or choke

[Neilm]

A switchmode power supply does not only have to take AC. They are also used in DC-Dc converters for example taking a battery votlage and providing a regulated supply from it. In this case the supply can be tiny. See this from Murata. http://www.murata.com/new/news_release/2010/1005/index.html

Neil