Two flyback diodes in parallel across a relay coil

flybackpcb-designrelay

I'm using relays that contain a flyback diode internally, so no need to add an external flyback diode. However, I want to provide a place on my PCB to possibly stuff a flyback diode in case I would have to replace the relay with a version that does not have the internal flyback diode.

But I was wondering: suppose the relay has a flyback diode built-in and I still do stuff the external flyback diode so the flyback diodes are put in parallel. Will that do any harm?

Best Answer

Two flyback diodes in parallel do no harm at all. Depending on diode type, either of those diodes takes the load, or both share the load. Two flyback diodes in anti-parallel are a very bad idea, though, because one of those diodes will be conducting when you try to power the coil.