Thanks for you replay.
Yes, the IRFP90N20D is one of the best replacements for the mosfet that the manufacturer supplies and has a little more power which is good, but I invite you to look at two things carefully:
1 - is the mosfet they sent you original?
I can give you two simple ways to check if it is with 95% certainty. The easiest thing is the weight. An original Mosfet such as IRFP90N20D must weigh about 5.5 g if it weighs 4.4 g it is a fake. Another thing you can try is RDS-ON; follow the diagram in the figure and if the value is close to that of the specifications or 0.03 ohm the mosfet will be original if instead it will be 0.1 ohm or worse it will be a fake.
![](https://i.ibb.co/nP8yTfG/TEST-MOSFET-RDSON.jpg)
if you need more details about this test ask and i will give you more information
2 - the second thing I want to tell you is that for this application the most important specification of the mosfet is that of the graph generally called "Maximum Safe Operating Area". I report the two images and you will see that the difference between the mosfet supplied by the manufacturer and the one you bought is less than what could appear from the maximum current and dissipated power
La prima immagine si riferisce al tuo nuovo Mosfet IRFP90N20D
[/url]
![](https://i.ibb.co/cYKPYFH/Cattura.jpg)
la seconda invece al mosfet che in questo periodo arriva già montato sulla board ovvero IRFP264
![](https://i.ibb.co/ZYm87z7/Cattura.jpg)
The first thing you can notice is that both graphs lack the curve in "DC" and the closest possible one is the one at 10 msec. This is because both mosfets, unfortunately, are not designed for a linear application like this one of the DL24. But unfortunately we know that linear ones are difficult to find, especially in this period, and cost a lot, generally between €30 and €40.
We can therefore think of an imaginary line that has the same distance between the 1 msec line and the 10 msec one.
The operating area is the one at the bottom under the dotted line. As you can see in first image referred to IRFP90N20D at 1 volt you can apply max 30A (the line is the same for the various times) between 4 and 5 volts you have the maximum value that we can imagine equal to the maximum of the Mosfet of 90A, but at 10 volts you will have already dropped to 30A and at 100v you will only have 1A of current.
The same reasoning about the IRFP264 mosfet leads you to:
with one volt you have about 10A, at 3 volts you have a peak of about 25A, at 10V you will have about 70A (better than the IRFP90N20D) and at 100V you will also have only 1A for this
As you can see, the IRFP90N20D does better but not always and not as much as could be expected from the value of the maximum current and dissipated power.
to conclude, keep in mind that the heatsink that I see, even if it has a wider fan, I'm not sure can reach values of 180W; If you have experience with heatsinks used in PCs you can agree with my fear.
For the rest, if you stay under 100-max120W this is a really nice object