Delete comment from: Ken Shirriff's blog
Thanks everyone for the comments!
For the European chargers, my guess is the circuit is similar but with a low-profile transformer. The US adapter takes 100-240 volts, so they could reuse the circuit. If anyone has a dead one lying around, let me know, since I'm unlikely to spend $30 to buy one.
Doug with the squealing charger: Chargers are designed to use frequencies above normal hearing range, but if you're relatively young, you may have better high frequency hearing. One other factor: some chargers pulse on and off when there's no load to save energy, which makes it more likely to be audible.
The iPhone charger uses about .25 watts when idle, according to Apple's environmental report. This is low, but about three times the power of the Samsung charger or the $2 knockoff chargers.
The iPad charger is bigger because it's 10 watts instead of 5.
Thanks again for all the thoughtful comments!
May 22, 2012, 1:22:52 AM
Posted to Apple iPhone charger teardown: quality in a tiny expensive package