Disassembling Apples 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.
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Cool! can you reverse engineer a circuit diagram out of that puppy? How many layers are in the PCB? Does it have a wound transformer – how does it achieve the voltage step down? Are there any chip / coding devices that mark the charger as being “Apple only?”
I wonder how much of this super-filtered design is because they had issues with the touchscreen on the 1st gen not being stable with normal supplies. I know that some of my laptops don’t deal well with 1st gen iPad charging (the touchscreen jitters around and on one registers phantom touches).
Richard: I included a circuit diagram in the original article. The PCBs (two of them) are two-layer. Yes, it has a flyback transformer – the article includes a complete transformer teardown. It uses the same Apple-proprietary D+/D- resistors to indicate that it’s an Apple charger that Adafruit discovered earlier.