I have designed a simple circuit that harvests energy that is generated from an electromagnetic generator.

I would like to know tips I could use to improve efficiency and minimize the losses I may have by using this design. I have drawn h the circuit for more clarity.

enter image description here

Please note the MOSFETs act like a diode bridge. This circuit has been tested and it works. I am interested in improving the efficiency including any other options that may even be costly.


The following are requested information as per comments.

The voltages peaks generated from the harvester has about 7v Pk-Pk. This depends on speed. I have mentioned the average.

The purpose of the zener is only to protect the BQ25505 from receiving beyond 5.5V. That is the maximum input voltage of the BQ IC.

High Spikes of 6V are reduced because of the capacitors charging effect. We have tested this and its true.

Currently i want to more efficiently harvest the energy bursts coming off the harvester. With lowest dropout voltage.

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    \$\begingroup\$ What FET's? At low amplitude from coil, will there be enough voltage to turn the Fet's on hard. (minimum resistance). And is the zener only for protection or does it typically conduct? \$\endgroup\$ – George Herold Dec 9 '15 at 17:37
  • 1
    \$\begingroup\$ So what do you currently measure as your efficiency? It's tried and tested so if you want to know about improvements you have to tell us where the defficiences are. \$\endgroup\$ – Andy aka Dec 9 '15 at 17:46
  • \$\begingroup\$ Dear all, please see the updated question. Thank you for help. \$\endgroup\$ – Denis Dec 10 '15 at 1:51

Your mosfet bridge will waste less voltage than diodes like you intended.You need enough Volts to drive the gates like george herold stated in comment. In fact at low input volts you will be worse off than diodes because the parasitic diode in all normal powermos is poor in terms of voltage drop and recovery.If you place shottkeys across the DS of each fet you will secure better performance at low voltages .Once you have done this there is still room for improvement.The voltage on C2 is more steady than the voltage on C1 .This voltage could be employed for running a gate drive circuit for the fets.I have done a circuit with 4 shottkeys and no pchannels ,just keeping the 2 nchannels .This could work better for you than what you have .

  • \$\begingroup\$ Thank you for the schotkey diode idea. It a great idea. Yes voltage on C2 is steady! Although we havent measured that yet. But Im sure its going to be because that is our system power. As you suggested, I am willing to spend a little energy at the cost of earning more in future. That is a great suggestion. If its possible could you please show me a schematic how I can employ a gate driver circuit? please. I have marked as answer as you already have answered the question. \$\endgroup\$ – Denis Dec 10 '15 at 1:55
  • \$\begingroup\$ Dear @Autistic If you could, please share a schematic. \$\endgroup\$ – Denis Feb 29 '16 at 5:11

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