Series and Parallel Operation: More Voltage or More Current, Safely

Sometimes one supply will not reach the voltage or current you need. You can combine two — in series for more voltage, or parallel for more current — but each has rules worth following.

Series, for more voltage

Wire the positive of one supply to the negative of the next and you add their voltages (two 24 V units give 48 V). It is straightforward, but fit a reverse-protection diode across each output so that at switch-on, or if one unit fails, the other cannot drive current backwards through it. Check the isolation rating too — the lower supply now floats above ground.

Parallel, for more current

Connecting outputs together to share a load is trickier: tiny differences mean one unit tries to hog the load. Use supplies that are designed for parallel operation — they include current-sharing (droop or active share) so each takes its fair portion. For redundancy, add ORing diodes as well.

The safe summary

Series is easy with blocking diodes; parallel needs supplies built for it. If in doubt, a single higher-rated supply is simpler than combining two. Tell us your requirements and we may be able to recommend a suitable solution.