energy harvesting circuit input voltage

[naeim29]

Hi all,

I should design a energy harvesting circuit for a wireless sensor nodes, I would so appreciate if someone helps me by replying question below:

* What is the lowest limit on amplitude level of input voltage for an energy harvesting circuit? For example, is it possible to rectify and multiply an input voltage of 1 mv to 5 v DC (output voltage)?

If I am not wrong voltage multiplier can increase the input voltage level just a few times so I don't think so I can get 5 v at the output with just employing multiplier!

On the other hand it is too difficult to bias transistors in DC/DC boost converter just with 1 mv! so I think it can't be applicable also!

I am really confused how can I get 5 v at the output of energy harvesting circuit just with 1 mv inputvoltage!

Thanks for your help in advance

 

[FvM]

LTC3108 is e.g. working from minimum 20 mV input voltage, dedicated to thermoelectric generators and similar low voltage energy sources. I don't know which practical energy harvesting applications will work with only 1 mV? In any case, energy harvesting is bound by conservation of energy law. This means, that the input power must be higher than the deliveres output power. A low input voltage will refer to a respective high input current and low circuit impedance.

LTC3108 is using a step-up transformer and self oscillating depletion mode FET inverter to allow start-up from millivolt level.

 

[naeim29]

LTC3108 is e.g. working from minimum 20 mV input voltage, dedicated to thermoelectric generators and similar low voltage energy sources. I don't know which practical energy harvesting applications will work with only 1 mV? In any case, energy harvesting is bound by conservation of energy law. This means, that the input power must be higher than the deliveres output power. A low input voltage will refer to a respective high input current and low circuit impedance.

LTC3108 is using a step-up transformer and self oscillating depletion mode FET inverter to allow start-up from millivolt level.

Thank you very much for your help. About the energy law as you said, for sure the output energy can not be more than input, otherwise the power efficiency will be more than 100%! (just the voltage and current level can be changed at the output).

regarding 1mv input it is just an assumption, it can be for ex. 20mv as you mentioned. I was wondering how I can increase such a low voltage level without using boost transformer since it occupies so much area. But it seems there is no way as it is employed also in LTC3108.

Again thank you for your time