Suppose I have something like 50 independent switching regulators all tied a single load and ideally sharing current. I could provide isolation for each regulator using a diode.
simulate this circuit – Schematic created using CircuitLab
Or I could provide GND isolation using a transformer.
For such a large number of power supplies in parallel, is there a risk of having massive GND noise on the shared GND plane from all the switching components? Would GND isolation help address this issue? If GND isolation is not required, what design considerations should be taken into account when sharing the GND?
Best Answer
In general you do not need or want to isolate the grounds.
However you can't usually just parallel power supplies. They will not share the load equally.
There are power supply module that are designed for being placed in parallel. Often they are intended to not only increase output but allow "hot-swap" repair. They are often referred to as being in an "N+1" load sharing configuration where there is one more power supply than is actually needed so that when one fails the remaining good ones can power the load while the failed one can be unplugged and replaced with a good one. These are used large rack-based server systems and for telecom applications.
The power output and grounds of all the supplies are connected directly together and often there is a load sharing signal that also connects to all the supplies.
Why do you want to put many power supplies in parallel?