The best way to power a Jetson Nano 4 GB dev board is by using a center positive, 5 V and at least 4 A barrel connector type power adapter. However, these are often bulky and not the best travel companion - while USB C power bricks are becoming more common and the relevant USB C sockets are getting build into nearly every device (maybe yours too, Apple?).
So I set out to build a USB C power adapter for the Jetson board.
By using an inexpensive USB C "trigger" combined with two 5V@3A step-down converters this did actually work.
The trick is setting the USB C trigger to request 20 V and using the 5 V converters in parallel to step-down the 20 V to 5 V - and then feeding the resulting voltage again in parallel to the barrel plug, like so.
For the curios among you now asking why I did not just set the trigger to 5 V and used it all alone: I tried this first, but it did not work. It was not able to provide enough current to support the operation of the Jetson at "MAXN mode" - it was constantly coming up with Overcurrent protection messages if pushed too hard.
I am happy with the result and shortend the wires after testing, putting everything into a neat small form factor.
With this change I can finally replace my old Jetson Nano power supply with something smaller than this chunky unit which I was gifted back in the day by the awesome Morlac :).