I would like to know if it is necessary (or recommended) to add fuses at the inputs when using multiple DC-DC converters. I have attached a quick schematic to illustrate what the design would look like if fuses are involved.
I guess in principle the fuses are there to protect the other DC-DC converters in case one becomes shorted.
However the DC-DC converters I plan to use seem to advertise "continuous short protection" and various other protections as well (ex: PYB20-Q48-S12 from CUI Inc.).
Are fuses really necessary if there is already protection in place? Would I be doing potentially more harm than good by adding them to the circuit? (ie: if I end up selecting fuses with incorrect thresholds)
Cheers!
Best Answer
The answer depends on what you are trying to accomplish. The fuse should help protect the battery from driving a short circuit and protect the harness wiring, both of which could cause a fire.
At a minimum, a single fuse on the +28V coming from the battery before it branches out to the individual feeders is sufficient.
Branch fuses, as in your schematic, still achieves the goal of protecting the battery and wiring while providing additional redundancy since one blown fuse won't take down the other branches.
Although the DC/DC converters may have 'continuous short' protection, there are other reasons to have the fuse (wiring and battery protection).