I have done DC converters before, both the curious way (AVRing it) and the lazy engineer's way (applying a datasheet formula) but it was always from nice DC sources with a fairly big filter cap.

Now, just for the reason of size, I'd like to go with a much smaller filter cap on the input, so the DC will have much ripple on it. I imagine this is going to muddle common buck-converter designs.

I'm looking for advice from people who did such a stunt before. What to look for to select a buck converter chip which behaves tame in such a situation?

EDIT: I found it's worth to note, these are many tiny boards needing +5V, and supplied 24VAC from a central distribution.

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  • \$\begingroup\$ To lower C, you must consider raising f. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 13 '18 at 19:11
  • \$\begingroup\$ I thought about that, Tony, but my flawed thinking lead me into the completely different direction. Could you please elaborate it in an answer? \$\endgroup\$ – Janka Aug 13 '18 at 19:12
  • \$\begingroup\$ Perhaps you should list all acceptance criteria and assumptions for source impedance \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 13 '18 at 19:14
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    \$\begingroup\$ Uh, I wasn't prepared for that. \$\endgroup\$ – Janka Aug 13 '18 at 19:15
  • \$\begingroup\$ Who said even with no input cap it will be such a mess? Is it based on something or just a guess? \$\endgroup\$ – Gregory Kornblum Aug 13 '18 at 19:17

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