iPhone charging adapter - how can it be so small? - Page 1
Forum section: electronics / general

author: shadewind
author_rank: Frequent Contributor
timestamp: March 09, 2011, 12:19:10 pm
content: 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

author: VIPR
author_rank: Contributor
timestamp: March 09, 2011, 12:23:08 pm
content: 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.

author: the_raptor
author_rank: Regular Contributor
timestamp: March 09, 2011, 01:23:52 pm
content: 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.

author: the_raptor
author_rank: Regular Contributor
timestamp: March 09, 2011, 02:14:49 pm
content: 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.

author: VIPR
author_rank: Contributor
timestamp: March 09, 2011, 03:11:18 pm
content: 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.

author: the_raptor
author_rank: Regular Contributor
timestamp: March 09, 2011, 04:33:38 pm
content: 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.

author: shadewind
author_rank: Frequent Contributor
timestamp: March 09, 2011, 06:29:48 pm
content: 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

author: Simon
author_rank: Unknown
timestamp: March 09, 2011, 07:27:29 pm
content: 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

author: Neilm
author_rank: Super Contributor
timestamp: March 09, 2011, 07:34:39 pm
content: 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.htmlNeil