iPhone Charger Teardown Shows Apple’s Attention to The Details
Submitted by lalit on May 23, 2012 - 11:42pm.
We all know the amount of emphasis Apple gives to design and quality while making devices like iPhones, iPads and Macs. However, Apple’s attention to the details doesn’t just end there, they focus on making everything related to the product perfect. And this is clearly shown in the design of iPhone charger, as revealed by a teardown done by Ken Shirriff’s blog. Ken concluded his iPhone charger teardown report by saying:
Apple's power adapter is clearly a high-quality power supply designed to produce carefully filtered power. 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.
The input AC is filtered through a tiny ferrite ring on the plastic case (see photo below). The diode bridge output is filtered by two large capacitors and an inductor. Two other R-C snubbers filter the diode bridge, which I've only seen elsewhere in audio power supplies to prevent 60Hz hum; perhaps this enhances the iTunes listening experience. Other chargers I disassembled don't use a ferrite ring and usually only a single filter capacitor. The primary circuit board has a grounded metal shield over the high-frequency components (see photo), which I haven't seen elsewhere. The transformer includes a shield winding to absorb EMI. The output circuit uses three capacitors including two relatively expensive tantalum ones and an inductor for filtering, when many supplies just use one capacitor. The Y capacitor is usually omitted from other designs. The resonant clamp circuit is highly innovative.
Apple's design provides extra safety in a few ways that were discussed earlier: the super-strong AC prongs, and the complex over-temperature / over-voltage shutdown circuit. Apple's isolation distance between primary and secondary appears to go beyond the regulations.
Apple's iPhone charger crams a lot of technology into a small space. Apple went to extra effort to provide higher quality and safety than other name-brand chargers, but this quality comes at a high cost.
Apple could have easily bought and shipped a third party charger with Apple’s logo on it for the iPhone, but they went one step further and designed the best USB charger available on the market for the iPhone. You can read the complete explanation about how the iPhone charger works and how Apple designed it on Ken Shirriff’s Blog.