non isolated power supply breaking buck converter.

[Jnation]

Hello all, I am having an interesting problem, and cant seem to figure out whats going on.  I am designing a circuit (arduino clone that powers a small or large dc motor, schematic attached) that uses a dc/dc buck converter (digikey part# BP5277-50-ND). When I'm powering the device with my bench top power supply, or an isolated power supply I have no problem.  However once I use a Mean Well GS160A24-R7B  power supply (24V 6.67A 160W Max) it destroys the buck converter! The only thing I have noticed is that when I use my fluke to check polarity, the ground output of the Mean Well power supply is connected to mains ground which tells me its not a isolated power supply.  I'm going to switch to a isolated power supply, but I would still like to learn why this would break the buck converter. 

Any help would be greatly appreciated!

-Jim

[uncle_bob]

Hi

All wall wart style supplies that are not "medical" have a common ground. That's just the way they do it. The ground is not your problem unless there is a sneak path. Best guess, you are not holding off the startup of your converter long enough or you do not have big enough input capacitors on the converter.

Bob

[Jnation]

Thanks so much! I attached a 47uF and a 1uf ceramic capacitor to the input voltage of the converter, works perfectly now.

Thanks again,

-Jim

EDIT* I was using a micro symbol, however they posted as ?  so i replaced them with a u.

[uncle_bob]

Thanks so much! I attached a 47uF and a 1uf ceramic capacitor to the input voltage of the converter, works perfectly now.

Thanks again,

-Jim

EDIT* I was using a micro symbol, however they posted as ?  so i replaced them with a u.

Hi

The *input* capacitor requirements for switching supplies are something that messes up a *lot* of people. First time through, nobody ever expects it to be an issue.

Bob