[sdiy] Roman Filippov power supply design

[Guy McCusker]

Roman Filippov is selling PCBs for a power supply which he says is
enough for a Music Easel or 8 of his Buchla clone modules:
https://electricmusicstore.com/products/power-supply-unit-model-211

The board takes 12VDC input and produces +/-15V, +12V and +5V. Taking
a look at the BOM, I can see a 5V switching regulator, a boost
converter and a buck converter.

Presumably the 12V input is passed straight to the output, and the 5V
regulator does the obvious thing. For the +/-15V, do you think it
likely that he's using the boost to produce +15V, and then using the
buck converter to produce an inverted version of that for the -15v?

If so, then could someone check my reasoning and calculations for the
maximum current one could get out of this please? I am thinking this:

the boost converter has a thermal resistance of 166 deg/W. I see no
heatsinking and at 25C ambient and max operating temperature of 125 we
have about 100 degrees to play with, so can afford to dissipate 0.6W.

The device is up to 90% efficient, so that would mean we could get
5.4W out of it, dissipating the other 0.6W. So it can produce
something like 360mA of current, and this has to feed both the +15V
and -15V rails. You get a bit less because of the inefficiency of the
buck converter for the negative rail, so we're looking at about 150mA
per rail.

This does not seem enough. On the other hand I don't exactly know what
I am talking about here. Have I messed this up?

Cheers,
Guy.