Does anyone have the experience the circuit really works at 20mV? Because i tried over and over again the minimum input voltage require at least 210mV ~ 250mV in order for it to work as expected. This is the schematic i used

 

Hello,

Here is an example simulation of the LTC3108:


Bertus

 

As shown above, 30mV in gets you 3.3V out.
20mV in gets you 2.98V out.

 

Are your results for a real circuit?
What transformer did you use?

 

Are your results for a real circuit?
What transformer did you use?

I use a normal mini transformer not the coilcraft (coupled inductor) as recommended by Linear Technology because i dont have one.

 

I use a normal mini transformer

That (and the low turns ratio) probably accounts for why you don't get the expected results. The LTC3108 switches at ~25kHz. The 'normal' transformer is presumably intended for 50/60Hz operation?

 

I use a normal mini transformer not the coilcraft (coupled inductor) as recommended by Linear Technology because i dont have one.

So how do you expect the circuit to work properly, if you substitute some random part for the one specified?

 

So how do you expect the circuit to work properly, if you substitute some random part for the one specified?

Yeah probably cause it's not easy to get those component and above all its very expensive just for a tiny component like that...

That (and the low turns ratio) probably accounts for why you don't get the expected results. The LTC3108 switches at ~25kHz. The 'normal' transformer is presumably intended for 50/60Hz operation?

The transformer is capable of going up to 3Khz step up using normal transistor / mosfets