Does anyone have an easy to understand primer

[Bas Horneman]

on how to calculate the "cooling" demands for a solid state part.

For instance I'm planning on using the IX20N50D as a CCS in the tail of an output stage. Thus it should sink around 120mA. How can I calculate if I need heatsinks. And how big the heatsinks should be.

Thank you in advance.

[Steve Dunlap]

Originally Posted by Bas Horneman

on how to calculate the "cooling" demands for a solid state part.

For instance I'm planning on using the IXN20N50D as a CCS in the tail of an output stage. Thus it should sink around 120mA. How can I calculate if I need heatsinks. And how big the heatsinks should be.

Thank you in advance.

Do you have a spec sheet for that part? When I Goggled it, your post was the only hit.

The power dissipation will be 120ma X voltage drop across CCS.

[Bas Horneman]

Here it is:

Sorry about the spelling error.

[Bas Horneman]

voltage drop

I'll be able to calculate the dissipation once I measure the voltage drop. But how can you read in the datasheet what the thing can handle? With tubes it's easy. They just state maximum dissipation of the plate.

In this device's datasheet they say 400W. But that is obviously just theoretically?

[SY]

Basically, it's set up just like an Ohm's Law problem. You start with the power the device will dissipate (voltage across it times current), then use the various thermal resistances multiplied by the power to see what the temperature is likely to be. What's the voltage across the device expected to be?

[SY]

Aha, here's a note on how to do it.

http://www.ixysrf.com/pdf/switch_mod...issipation.pdf

Frankly, for what's likely to be 5-6W, a small bolt-on heatsink will probably work fine. If the heatsink is rater 10°/W, the 5-6 watts will raise the temperature to about 75°, which is fairly hot but no-where near danger. The junction temp will be sitting a few degrees hotter because of unction to case and case to heatsink thermal resistances. But anything under 100°C is no real issue.

[Bas Horneman]

Frankly, for what's likely to be 5-6W, a small bolt-on heatsink will probably work fine. If the heatsink is rater 10°/W, the 5-6 watts will raise the temperature to about 75°, which is fairly hot but no-where near danger. The junction temp will be sitting a few degrees hotter because of unction to case and case to heatsink thermal resistances. But anything under 100°C is no real issue.

Thanks Stuart!

What's the voltage across the device expected to be?

I don't know. Since the ccs will drop less voltage then say a resistor I think? It will be used in a PP 6N3C-e for one of my sons.

But like you said. A bolt on type should suffice. I was hoping these would suffice.

Maße: B X H X T: ca. (25mm, 25mm, 43mm)
Zum einlöten (RA 26mm)
für Gehäuse TO220
Gewicht: 0,100Kg.

They mention TO220. But the TO-249's fit too.

[Steve Dunlap]

That should work.

[Bas Horneman]

That should work.

Thanks Steve.

[PeteMcK]

Semiconductor Safe Operating Area