I've been doing lots of research on designing a flyback converter for work (no, I cannot purchase an off-the-shelf one). In all of my research, it looks like nearly all design involves snubber/clamper circuits around the switch to reduce ringing followed by a carefully selected capacitor on the output to control Vout ripple. Why not put a voltage regulator on to reduce voltage ripple to 0? The regulator (in my mind) would be added on after the capacitor to help eliminate the ripple - not replace it all together. None of the texts or articles I read mention anything about including an OP Amp or Voltage Regulator and I am starting to figure there must be some important concept I am overlooking here.