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An Engineer in Wonderland – Supercap guy replies

supercap-circuit-thumb.jpgFrom Pierre Mars of CAP-XX

Just responding to your comment in the blog An Engineer in Wonderland – Energy harvesting and supercapacitors.

You are quite right, the final circuit would need 2 x MAX9015, you can’t use both op amps in the dual version MAX9107.

Since then I have done some more work… 

The Perpetuum microgenerator can supply current into a short circuit.

It is more efficient to charge a supercapacitor from 0V using short cct current if the energy harvester can do this (such as microgenerators or solar cells) and not worry about peak power tracking.

All you need is over-voltage protection for the supercap.

I have attached a circuit from a presentation I gave at IDTechEx Europe this year which covers this.

supercap-circuit-web.jpgNote that I use shunt regulators for over voltage protection for simplicity, since once the supercap is fully charged, any energy delivered by the energy harvesting source must be discarded.

Cheers – Pierre

V-p applications engineering
CAP-XX
NSW Australia

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Tags: dual version, marketing, nsw australia, op amps, Wonderland

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1 Comment

  1. Sage Radachowsky
    July 17, 2010 11:33

    Now that makes a lot more sense. Thank you for the question and for posting the reply. I did not understand the “peak power tracking” of the previous circuit. It did not make conceptual sens… I kept looking for the buck converter or boost or charge pump, but there was none.
    I love the balancing circuit. It is so elegant and works at ultra low power now that there are good op amps available for 1 uA quiescent current.