High amp diode for high pressure pump


#1

Friends,

I am having trouble, this could be as a result of how novice I am, finding a kickback diode for a pump i am trying to control using a MOSFET. The pump is rated for 12V and 6 amp at its highest draw, it can be found here. It is being powered with an N-Channel MOSFET, here.

I cant seem to find a diode rated for (12 x 6) ~100 watts. I have a feeling I could be missing something. Any insight is greatly appreciated.


#2

Hi @jjlee32

You did not say where you had looked already, but you might not find a high amperage diode at the hobbyist electronics places. You can certainly find them at the professional distributors.

Here is the data sheet for 10A diode available for $0.59 each at Avnet. You will want to buy some other stuff to get a minimum order but they are readily available.


#3

Thanks for the help!


#4

You dont need a 100W diode. A standard silicon diode will have a Vf of ~0.7V. At 6A it will only dissipate roughly 4W. If you use a Schottky diode, Vf will be ~0.4V and you will only drop 2.5W. Schottky’s generally switch faster than standard rectifier diodes.
In your case I’d pick a Schottky diode rated at around 10A, 25V (or higher) with a power rating of about 10W. That should give you plenty of safety margin. Digikey or Mouser will have a bewildering array of choices in that range.

I am assuming that by ‘kickback diode’ you mean you are putting a diode reverse biased across the pump, to protect the mosfet? Is this a PWM for speed control, or simple on/off?


#5

I already got a few of the diodes suggested above :hushed:. Other than the, I presume, slight delay in switch is their any other benefits to using a Schotky diode.

This isn’t for PWM just simple on/off, and yes Ill have the pump wired across the diode to protect against any emf spikes. Thanks for the insight


#6

For a simple on/off there’s no benefit in using a Schottky - you are not switching often so switching losses will be tiny. The diodes you have should be just fine. I’d add about 10nF - 100nF across the diode too - this will slow the risetime of the reverse pulse, rectifier diodes are not particularly fast at turning on.