I thought about what is the easiest way to build up a low power buck converter with discrete components I have at hand. This is what I came up with (LTSpice model):
While being prone to explode on first startup it offers, with non-ideal inductor and capacitor a efficiency of about 76%. It lacks a current limit for Q1, which could be introduced with an oscillator and a flip-flop to store the current switch state to avoid high frequency oscillation. Maybe this the point i should order a 34063…