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by Neywiny 47 days ago
Yes for a few reasons: more components, more noise filtering needed for sensitive devices, and more design theory and analysis is needed. A linear supply is nothing more than a high current op-amp. A switching supply requires understanding currents in the time domain to choose or design the right inductor. It's just more.

However, they don't need the same heatsinking as linear supplies, so they're less expensive in that regard. If designing an optimal heatsink (which has the second order effect of determining what else around the part will heat up because of the regulator) is a lot of work, then maybe the NRE will be the same. But overall linear regulators are fewer and simpler components so the BoM cost is a lot lower.
1 comments
xyzzy123 47 days ago
The materials in a 60hz transformer I think are the main BOM cost for linears? Relatively, transformers are say 2x cheaper than in 1970 (steel and copper are relatively MORE expensive than they used to be but the manufacturing improved) - but chips are more like 100x or 1000x cheaper. The high frequencies of switchers let you shrink the transformer (less materials) so its a big win.

Also the waste heat of linears constrains your design in terms of weight, power density, how big you need to make the enclosure, etc.

For reference I looked at what I'd need to buy on AliExpress to power my laptop off the cheapest linear PSU I could find (say 20v 5A), something like: https://www.aliexpress.com/item/1005003397909174.html - it weighs 4kg vs 300g for the charger I have. Apparently there ARE audio people who put their NAS on a linear PSU (I did not realise that was a thing!) but I'm going to try to forget I saw that.

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dragontamer 46 days ago
Switchers in the 80s were only 80% efficient at best. The chips just weren't fast enough for much better.

Switching from maybe 70% efficient linear to 80% efficient switcher means only a 30% reduction to copper or transformers.

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Today, a switcher is maybe 95% to 99% efficient. So switching from 70% efficient linear to 97% efficient switcher is a 90% reduction in coils/heat sinks.

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kens 46 days ago
Switchers have much smaller transformers because the frequency is much higher, >20 kHz vs 60 Hz. (This is the same reason that avionics use 400 Hz power instead of 60 Hz.)
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