I just had a terrible idea that, much to my relief, others have already tried out. I couldn't find any instances of house fires or serious injuries related to this so I'll take that as a good sign
Using an old fashioned 555 timer as the pulse trigger for a switched mode power supply
In fact, here's a pretty nice project on using the 555 timer as a variable power supply for a nixie tube https://github.com/tardate/LittleArduinoProjects/blob/master/Electronics101/555Timer/NixiePowerSupply/README.md
This is a very simple and straightforward explanation of a SEPIC converter topology for a power supply
This is good for when the power can be lower or higher than the voltage you need (as in maybe a solar panel supplying a battery and circuit). MPPT charge controllers work similar to this
For my ATmega328 power source, I'll probably do this since, most of the time, it will also probably spend a lot of time connected to a solar panel for simple outdoor projects
https://www.youtube.com/watch?v=dV-LRAUZ_AA
This is a very simple and straightforward explanation of a SEPIC converter topology for a power supply
This is good for when the power can be lower or higher than the voltage you need (as in maybe a solar panel supplying a battery and circuit). MPPT charge controllers work similar to this
For my ATmega328 power source, I'll probably do this since, most of the time, it will also probably spend a lot of time connected to a solar panel for simple outdoor projects