600 V electronic load

[Martinn]

Hi all, just showing this little electronic load modification. Like most designers, at some point I realized the significance of the term "DC SOA" and consequentely came across the IXYS linear FET range https://www.littelfuse.com/products/power-semiconductors/discrete-mosfets/n-channel-linear.aspx
Their product list has "Sample" buttons which actually work - so some time later I had a IXTN30N100L to play with. It is a 1000 V, 30 A, 800 W N channel FET. Even better, at case=90°C it has a DC SOA of 600 V, 0.5 A. Impressive!
I implanted this little monster in a "100W electronic load" module from ebay and changed shunt and voltage sense resistors for a 1 kV/1A full scale range. I also replaced the potentiometer with a 10 turn, as I intend to stay away from lethal power levels and more in the mA range.
Still usable current starts at about 5 mA with this setup, I'd have to change the shunt but would lose the 1A range. Anything else would need more complicated modifications and I'd be probably faster designing the whole thing from scratch.
Isolation is of course not sufficient for 1 kV operation, but I tested it with a (current limited) 400 V supply and it did not fall apart. I guess this thing will be fine for testing my nixie and scope clock power supplies.

- Martin

[JohanH]

Their product list has "Sample" buttons which actually work - so some time later I had a IXTN30N100L to play with. It is a 1000 V, 30 A, 800 W N channel FET. Even better, at case=90°C it has a DC SOA of 600 V, 0.5 A. Impressive!

That's generous of them, it seems to be an expensive part! I was looking at Onsemi FCH041N60E and FGH60N60SMD with similar DC SOA as the IXYS, but much cheaper (ordered the FGH60N60SMD IGBT and planning to test it).