@KedasProbe:Hey thank you. I made an annotation in the video about the typing mistake.
@Firewalker: Yeah it's actually quiet easy to build up buck, boost and inverting converters in the way you described it. You can also use astable multivibrators, or the NE 555 timer to build a square wave oscillator with variable duty cyle.
But micro controllers can of course produce a good PWM too.
But to really build up "all DC to DC converters" You have to consider the following: As I mentioned a couple of times in the video, there are some other Dc to Dc topologies, like the charge pump and the transformer based topologies like flyback, forward and push pull converters. They are more complicated to experiment with, because you need the different kinds of transformers for that. I will deal with those in upcoming video though.