> I started with various sizes of buck converters, but it seems that they are too noisy and get blown out by voltage spikes or dips when the inverter kicks in or cuts off.
Dips shouldn't kill it (unless it's inherently unstable) but spikes definitely can.
Spikes can be addressed with appropriate input protection. A big, low-value resistor with a TVS behind it should take care of spikes.
But this shouldn't be a difficult problem to solve. Converting 48V to ~5V is extremely common in PoE equipment. There are numerous off the shelf designs designed for it. It's likely you were looking in the wrong place (e.g. searching for "buck" instead of "flyback").
Dips shouldn't kill it (unless it's inherently unstable) but spikes definitely can.
Spikes can be addressed with appropriate input protection. A big, low-value resistor with a TVS behind it should take care of spikes.
But this shouldn't be a difficult problem to solve. Converting 48V to ~5V is extremely common in PoE equipment. There are numerous off the shelf designs designed for it. It's likely you were looking in the wrong place (e.g. searching for "buck" instead of "flyback").