Power Supply Redundancy: N+1, Hot-Swap and ORing

In a process line, a server room or a safety system, an unplanned shutdown is expensive or dangerous. Redundancy keeps the load running even when one supply fails — and it relies on three ideas working together.

N+1

Run one more supply than the load strictly needs. If the load needs three units’ worth of power, fit four (N+1). Lose any one and the rest carry the load without a flicker. For the most critical systems, N+2 adds a second spare.

ORing

You cannot simply wire two supplies in parallel and hope — a failed unit could drag the others down. An ORing diode or controller lets each supply feed a shared output but blocks current flowing back into a failed one, isolating the fault automatically.

Hot-swap

Redundancy is only useful if you can replace the dead unit without downtime. Hot-swap supplies (often on a rack or shelf) pull out and slot back in live, so a fitter can change a failed module while the system keeps running.

Put the three together — N+1 sizing, ORing for fault isolation, hot-swap for repair — and a single failure becomes a non-event.

Tell us the load and how critical it is and we will help you size a redundant set.