How to efficiently isolate an optional power source from main power circuit?

[player80]

Hi,

I'm using some chipset via USB which allows an input voltage between 4 - 20V

In order to block 12V from injecting to the 5V power circuit I'm using a diode on the 5V supply.
While this works fine with 12V (since the current is low), when I power the chipset with 5V the current is quite high which results that this diode is heating up quite a lot.

Does anyone know any better way to isolate the main input voltage?

 

[KlausST]

Hi,

Please show your schematic, and add some current informations.

Klaus

 

[player80]

I just put something together using schemeit

https://snag.gy/JZMoZ.jpg

if 1A is passed through the 5V diode it will get quite hot

 

[player80]

https://www.linear.com/product/LTC4412

I will try this one.

There has been a post about this earlier already in another Forum (years ago):
https://forums.bit-tech.net/showthread.php?t=130910