DIYbanter - View Single Post - Why 3-prong plugs

Ralph Mowery

In article ,
says...

On Tue, 07 Mar 2017 20:27:10 -0500, wrote:

If the power supply were to short power could get through the
laptop, and out the USB or headphone, or whatever jacks.?
Anyway, some require grounding by code, others don'r.

It's a good question, since the OP is right that a power supply seems
pretty well isolated by all that plastic encasement, and the output is low
DC at relatively low amps ( 10 or so amps most of the time).

There's no power transformers anymore due to the switching power supply
design.

And yet ... ... ...

I wonder if the electronics of the switching power supply require a really
good ground?

The switchers do have transformers in them. They are usually after some
of the switching circuit and are very small compaired to what they are
if they were on the 60 HZ side.

The electronics will work fine without a ground. The ground is for
safety, and it does help with the filtering of the hash the switchers
generate that is fed back on the power wires.
It may also pay a small part to help prevent surges coming in from the
AC line.