Attention to Details: Quality of Apple iPhone Charger
Innovative engineering behind the iPhone charger explained by Ken Shirriff.
Is the Apple iPhone charger overpriced? Why is the Apple charger $30 while third party knockoff chargers can be bought for a few dollars?
Short answer: the Apple charger is not only designed for safety, durability, and power efficiency, it is also designed for interference reduction. It even uses a design normally used in audio power supplies to prevent 60Hz hum (aka ground loop interference).
In contrast, counterfeit chargers are shoddily constructed, cut corners on important safety regulations, and can cause touchscreen interference.
Ken Shirriff’s blog, arcfn: “Apple iPhone charger teardown: quality in a tiny expensive package” explains the engineering. Excerpts:
“Disassembling Apple’s diminutive inch-cube iPhone charger reveals a technologically advanced flyback switching power supply that goes beyond the typical charger. It simply takes AC input (anything between 100 and 240 volts) and produce 5 watts of smooth 5 volt power, but the circuit to do this is surprisingly complex and innovative.”
On efficiency of Apple charger:
“The iPhone power adapter is a switching power supply, where the input power is switched on and off about 70,000 times a second in order to get the exact output voltage required. Because of their design, switching power supplies are generally compact and efficient and generate little waste heat compared to simpler linear power supplies.”
On durability of Apple vs. Samsung vs. cheaper counterfeit charger:
“I tried pulling out the prongs of the Apple charger, a Samsung charger, and a counterfeit charger. The counterfeit prongs came out with a tug with pliers, as there’s basically nothing anchoring them but friction. The Samsung prongs took a lot of pulling and twisting with pliers, since they have little metal tabs holding them in place, but eventually they came out.
When I moved on to the Apple charger, the prongs didn’t budge, even with my hardest pulling with pliers.”
On a safety feature of the Apple charger:
“isolation boundary ensures that dangerous voltages cannot reach the output. [...]
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.”
On reducing interference:
“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.”
Incredible. We bet that Apple put in similar amount of engineering into a Mac charger and other components. The cheap knockoffs or the Samsung knockoff don’t even come close.
For the full tear down, schematic, estimated charger component cost, and lots of electrical engineering talk, head on over to Ken Shirriff’s blog, arcfn, linked above.
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