An exhaustive analysis of the iPhone charger was conducted by Ken Shirriff (via Gizmodo), revealing that Apple utilizes a "surprisingly complex and innovative" circuit to convert AC input between 100 and 240 volts to 5 watts of smooth 5 volt power.
""Apple's power adapter is clearly a high-quality power supply designed to produce carefully filtered power," he wrote. "Apple has obviously gone to extra effort to reduce EMI interference, probably to keep the charger from interfering with the touchscreen.
"When I opened the charger up, I expected to find a standard design, but I've compared the charger to the Samsung charger and several other high-quality industry designs, and Apple goes beyond these designs in several ways."
One of Apple's main concerns with the design of its charger is safety. Shirriff found that Apple employs "super-strong AC prongs," as well as a "complex over-temperature / over-voltage shutdown circuit."
In particular, the strong charger prongs were likely prompted by a recall Apple initiated in 2008 for iPhone 3G USB power adapters. The recall began after Apple found that "certain conditions" could cause the prongs to snap off when the adapter is pulled from a wall outlet, potentially creating a shock for those who might touch an exposed connection.
Shirriff found that Apple's new and improve prongs are considerably more difficult to remove than counterfeit devices and even Samsung's chargers. Apple's prongs refused to budge even when they were pulled using pliers.
"They have large metal flanges embedded in the plastic of the case, so there's no way a prong can come loose short of the destruction of the charter," he said, adding: "I'm impressed with the effort Apple put into making the charger more safe after the recall."
The teardown also found that Apple's charging circuits pack an impressive amount of complexity into a size smaller than one inch. In all, the charger crams most of the components into a printed circuit board that is about the size of a quarter.
Even with superior components and greater safety, Shirriff speculated that Apple's charger is still sold for "almost all profit." Apple's higher-quality parts probably cost the company about a dollar extra, but the charger sells for about $20 more than similar competing options.