I am also facing the same problem to my raspberry pi 5 that need 5V,5A. And i have 48V continous dc supply and now i want to regulate it to 5V,5A i have tried LM2596 step down converter but the IC is burn out and i blew the raspberry pi so that's why i need the voltage regulator which gives me the 5V,5A. Please need the circuit diagram for this.

Moderator edit: New thread created from this.

 

Why do You need 5-Amps ?

Or, did You try your ~3-Amp-Regulator without proper Heat-Sinking ?

Did You use the EXACT part-numbers recommended by the manufacturer for the Filter-Section ?
You will probably need to double-up on the Output-Filtering, and add Input-Filtering as well,
( all Filter-Components can be the same values as recommended by the manufacturer ).

Have You tried a LT1074 ?, ( 5-Amps )
.
.
.

 

Instead of a fuse, which gets tedious when adjusting the trip point, you can use a light bulb, such as a six volt five watt bulb, or even a 12 volt backup light bulb, which will be much easier to find. THEN when the SCR starts conducting the bulb will light and its resistance will limit the current. And switching the power off will reset everything.

 

If it is that critical to protect the $199/210GBP (or more) Nano against accidental over-voltage then the suggestion of an ISOLATED dc-dc converter is the only sensible option IMHO.

It's not a cheap option however, A Traco THL 25-1211 25W, 5v/5A out, 9-18v in is $67/52GBP, the 15W version THL 15-2411, 5v/3A out 9-36v in is $31/25GBP (other manufacturers are available).

Mind you, by the time you've built your crowbar device you'll have spent at least that much and you'll still be wondering if it'll protect you....

 

Try one of these?
https://www.amazon.com/ALITOVE-Converter-5-5x2-1mm-100V-240V-Security/dp/B078RT3ZPS/ref=sr_1_1_sspa
Or
https://www.amazon.com/BTF-LIGHTING...ing-Transformer/dp/B0BNQ7721C/ref=sr_1_2_sspa
Why are you trying to use a 48V power supply? You're dropping over 40 volts just to get down to 5V. Seems like a big waste.

 

Tony makes a VERY GOOD POINT!!! why start with 48 volts?? For less that $30 USD you can buy a switcher delivering 5 volts at up to 3 amps, and power it from the 120/240 mains direct.