Efficient Conversion of 1 V peak AC to DC

[favrefan87]

Hey guys,

I am new here and had a question. I currently have a 1 V peak (2 Vpp) AC wave coming into my system and I want to find the most efficient way to convert it into DC. A simple bridge wouldn't work for me because too much of the voltage would be dropped across the diodes. The system is a small battery powered sensor and I am trying to use this 1 V input wave as a trickle charger. Any guidance or ideas?

Thanks

 

[skeptic2]

Can you connect it to the primary of a step up transformer and use a full wave rectifier on the secondary?

 

[favrefan87]

I haven't thought about that, but as I said the system is a small battery powered one and I am trying to find some way of doing this in a small physical manner.

 

[skeptic2]

You haven't mentioned what frequency your AC is and if you don't need isolation between the primary and secondary, it may be possible to make a small auto-transformer by winding turns on a suitable core.

 

[favrefan87]

Sorry about that, the frequency is around 75 Hz and no I don't need any isolation between primary and secondary.

 

[skeptic2]

You may be able to wrap a substantial number of turns of enameled wire around a nail with a tap for the primary.

 

[Okefenokee]

If you want this thing to be super tiny and cheap then you could use Schottky diodes for a bridge rectifier (forward voltage ~ 0.3) and then step up the DC voltage with a Buck booster to whatever level you need. One caveat, you said it was an instrument so, depending on how sensitive the instrument is, you may need to worry about the high frequency noise coming from the Buck booster . The efficiency wouldn't be too bad but certainly wouldn't be as good as the transformer set-up.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556570&k=DC%20-%20DC"

Don't worry, you can filter the results. Pro-tip: hold down the "Ctrl" button to select more than one specification in the filter list.

 

[skeptic2]

Another possibility but much more difficult would be to sense the polarity of the AC and open and close analog switches in an arrangement like that of a full wave rectifier to achieve rectification. By using mosfets, a lower voltage drop could be achieved than by diodes. This approach might make sense if you are already using a microcontroller or even a comparator.