What does all this circuitry do in here?

My daughter’s USB charger broke and we decided to dissect it. What does all this circuitry do in a charger?

It is probably used to implement various USB charging standards. This is to ensure you get the correct voltage requested by the device and avoid overcharging once the battery is full.

Additional details can be found here.


Ask Google about “USB teardown” and you’ll find more info and videos than you’ll ever want to see.

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In such a charger (SMPS) you have:

  • (input) rectifier/filter
  • MOSFET transistor
  • voltage conversion
  • output smoothing
  • regulation
    Getting from 115V-230V AC to constant DC requires:
  • get the voltage down
  • “turn” half of the sinusoidal AC (+ and -) to DC (+ and +)
  • regulate (input can be 115 or 230)
  • smoothe from sinusoidal or whatever “curvy” current you have to a constant line
  • filter out crap
  • don’t interfere (filtering)

The big difference between high-quality and crap chargers is that at least one of the stages something is missing or not done right.

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