so I figured out where the buzzing is coming from in my circuit, and I think I'm starting to see the problem with it.

Here is a schematic I have: Schematic made in altium

The DC/DC step down converter I'm using: http://www.ti.com/lit/ds/symlink/tps54531.pdf

So what this is doing is charging up a super capacitor fairly quickly at 5.6V on the output, and since my feedback is after the current-limiting resistors, I realized now that when the capacitors are fully discharged, I'm essentially shorting the post-resistor node.

So the converter is trying to upkeep a 5.6V after the current-limiting resistors (which at that point is basically ground) which makes it run at full throttle. Not good!

My question is, would moving the feedback before the current-limiting resistors help? What I'm kindof unsure about is since the capacitors are essentially a short to ground at no-charge, would the capacitors initially see no voltage on the input, since it is all dropping across the current-limiting resistors?

Or, would this be compensated by residual charge and the capacitors still charging with some small current and raising the voltage?

Thanks :) If there is some other solution please let me know!!


1 Answer 1


Well, since it sounds like the supercap and its associated limiting resistors are the load (or at least part of it), then yes, I think your feedback should occur before the resistors, not after them.


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