Electronics > Beginners

Flyback Diode

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Chet T16:
I'm building a quick and simple fuel injector pulser for a friend that will drive up to 4 low impedance injectors at once but i'm not sure what diode i need to put in parallel with the output.

From what i have read the induced voltage is around 90V. The max output current 28A @12V

So, what rating diode do i need? (or more importantly, teach me what i need to know!)

on the whole a diode rated for about the same current as the coils consumption is ok giving emphasis on the peak/instantaneous current capability if you have a choice of parts

The diode will only see the supply voltage applied (28 vdc), and the current will be the coil current, max.  Generally diodes are available in 50 or 100 volts as a minimum.  The only real factor is how fast you want the diode.  A standard diode is likely OKay, and perhaps a fast recovery type may be better.  Depends on how fast you will cycle the coil.


Chet T16:
So the 90v is irrelevant? Once i have a diode rated >12v (i assume you meant 12) and >28A i'm fine?

I'm not sure how fast its possible to cycle under i get some testing done and see how fast they open. No more than 130Hz anyway

your diode must have a reverse voltage of at least the supply (2x recomended) 130 Hz is not too fast so no need to worry too much about speed but you require decent recovery time as it is being pulsed and is not a once now and then pulse


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