Hi,
here is the case:
Switch powered by 100-230VAC/48DC-1A adapter with earthed plug. At 48V side,
"Vcc-" is connected through resistor directly to Earth ground.
This switch has PoE port, which is used to power external device (PD, powered
device), when there is a laptop connected through RS232 port to this PD.
Laptop has his own power adapter, I assume grounded as well.
In certain scenario, powered device in the middle, will get smoked. One claims
it is due to the ground loop, based on Vcc- of power adapter being directly
tied to chassis ground.
Problem goes away after the connection is cut.
Few questions:
1. are where any 60950 issues which could prevent tying DC(-) output to
earth
ground? (adapter has UL, TUV/CB certificates)
2. assuming the answer to #1 is "no", would this scenario require switch
adapter and laptop adapter to be connected to different grounds? in order to
create different potentials? and thus will make powered device in the middle
the weakest point in the system?
Thanks in advance for your suggestions.
Mark
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