I wouldn't call the UC384x "vintage"; they are still in production today. Likewise, the TL494/KA7500 was very common in PC PSUs and is still in production too --- perhaps you could analyse its die circuitry for comparison.<p><i>For schematics of power supplies using this UC3842 chip, see this site, near the bottom of the page.</i><p>Before looking at the URL I guessed it would be <i>that</i> site. The author is also on YouTube under the name DiodeGoneWild, and not surprisingly posts videos about SMPS electronics too.
It surprises me that even today nearly every power supply has a dedicated chip in like this whose task is switching a transistor on and off with the correct timings to regulate an output voltage, using mostly analogue components.<p>It surprises me that this role hasn't been replaced with a tiny ARM core running some firmware to do the same. The benefit is the core can be self-tuning. It can detect components going out of spec and warn and/or compensate. It can have digital comms with the rest of the system to set all kinds of parameters, allowing a more flexible design and allowing bug fixes in the field. It can have lookup tables to tune efficiency for input/output voltage, load, etc, in a way an analogue design never could.<p>Considering a tiny microcontroller has a BOM cost of just 4 cents, in the same region as dedicated power supply chips, I don't see why software-controller-switched-mode-supplies aren't common.