switching regulator control

[ruma]

Why is it that inductor-based switching regulators use PWM (or PFM, for low load) where as, inductor-less regulators are regulated by varying switch on resistance ? Are there any papers discussing causes/relative merits&demerits of various regulation schemes ?

 

[dick_freebird]

Varying on-resistance to anything but minimum or maximum (off)
makes the regulator lossy, inefficient. This is not desired,
only tolerated in the interest of other things (like noise,
simplicity). But if thermal extraction is a problem, power
output is high, battery life is king, etc. you will be learning
to like the switcher.