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Actually I am working on a project to create an electronic load for power supplies, batteries... testing. The circuit is already designed but I am working now in the heat disipation of the mosfet in such conditions.

I want to make it able to simulate loads up to 100W, so the mosfet will have to disipate almost all the power (wich is a lot). Searching on internet I was able to calculate the requied max Rsa for the heatsink thanks to this formula:

Rsa = (Tj - Ta) / Pd - (Rjc + Rcs)

Now I know that I need a heatsink with an Rsa of less than 1ºC/W but the most of heatsinks I see doesn't provide that info, just the materials and sizes.

Someone can help me with info about how to calculate the Thermal Resistance of a HeatSink?.

Thanks!

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  • \$\begingroup\$ You'll probably have your question closed because questions seeking product recommendations are off-topic on this site so you might want to remove that part. Start by looking at the major supplier's catalogues. When you find an interesting heatsink then get its datasheet and see what you can learn from that. Bear in mind that a long heatsink will probably be rated for several components mounted along it's length. If you're just putting one great big heat source in the middle you're likely to be disappointed due to the thermal gradient along the device. \$\endgroup\$
    – Transistor
    Jan 19, 2021 at 23:00
  • \$\begingroup\$ I'm not searching for products recommendations, I'm looking for help for calculating/select the right size/materials of the heatsink, or by defaut, any book, article or similar with info about it... For products I have a lot of sites where to take a look, but I've seen that there are a lot of sites where there is no info about the Heatsink Rsa, just a datasheet of material and sizes, and that is my question, how to calculate the Rsa of those heatsinks to know if is the right choice. \$\endgroup\$
    – Daniel Carrasco Marín
    Jan 19, 2021 at 23:46
  • \$\begingroup\$ You should have listened ... Your looking for books and articles in your last paragraph. Fix the question and you should be able to get it reopened. \$\endgroup\$
    – Transistor
    Jan 19, 2021 at 23:58
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    \$\begingroup\$ Because the contributors to the site all want the site to be better and also want to help, combined with the complexity of the topics, we're constantly trying to make questions better, and also letting something slide in almost any question. When I see a high quality question that's within my expertise, I experience a much stronger motivation to write a high quality answer than if the motivation is just to help out. A low quality question is one that helps only one person or does not stand up over time. \$\endgroup\$
    – K H
    Jan 20, 2021 at 2:37
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    \$\begingroup\$ I think the problem here is that the vast majority of us don't even try to calculate the thermal resistance of a heatsink...the manufacturer of the heatsink should provide that information. If you aren't finding that specification, look at some other manufacturer's websites. Don't look at vendor websites, just the manufacturer's websites. \$\endgroup\$
    – Elliot Alderson
    Jan 20, 2021 at 20:35

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