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# low frequency PM

I have an energy harvester that generates impulses at frequency as low as 25Hz.  Each impulse has a positive and negative parts.  The width of each impulse is ~8ms (positive+negative).  The PTP amplitude is ~5V.  I can use a bridge rectifier but in order to fully rectify the signal I'll need a very large capacitor, something I would like to avoid because of size and weight.

Is there a suitable PM that can handle such an input?

Thank you!

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• Thank you!

I assume you mean just rectifying bridge, without a capacitor.  My concern is that the energy is in a form of impulse with relative large time in-between.  Can the buck-boost solution handle such large time between impulses?

• Thank you!

I assume you refer to a bridge without smoothing capacitor.  Can these buck-boost solutions handle the large time between impulses?

• I think that you will still need bit of capacitance after the bridge rectifier.

• Thank you Fil,

If the frequency is 25Hz and the matched resistance is say ~20 ohm then for 10% ripple the capacitor is ~20mF.  These are typically super-capacitor.  Do they behave the same as standard capacitors?

If I understand what you are saying, we don't need a 10% smoothness at the input to the PM in order to get stable voltage at the output of the PM.  Maybe 30% ripple is still good enough.  Is this what you have in mind?

• The ripple should be able to go by how much the buck-boost can take as low voltage as possible. You have to check that when the voltage goes to minimum, the current goes high & rating of the parts are still ok.