This isn't an actual charger though, just a basic off the shelf switching power supply, low power AC -> 5V DC.
The actual battery charger chip is on the phone (which again, will use a ready made BMS IC, so not really complicated either, all the smarts are already done).
There's some things to consider when laying out a switcher (keep loop areas small, keep sensitive lines from noise ones, etc), but it's not that complicated, and once you've done a few of them, it becomes routine.
And of course to pass safety standards there are clearance and creepage rules and EMI/EMC to keep in mind.
Any junior level EE/hobbyist with a few years of tinkering should be able to put this together.
There's some things to consider when laying out a switcher (keep loop areas small, keep sensitive lines from noise ones, etc), but it's not that complicated, and once you've done a few of them, it becomes routine. And of course to pass safety standards there are clearance and creepage rules and EMI/EMC to keep in mind.
Any junior level EE/hobbyist with a few years of tinkering should be able to put this together.