If I remember correctly,
there was a way of wiring power MOSFets in such a way (gate to drain, or gate to source; can't remember which) which made it basically into a diode, but with a very low Vf.
It shouldn't be too hard to design a piece of electronics, that basically samples your incoming sinewave, and turns on and off (I think 4) the MOSFets (in a bridge?), to get pulsed DC. Haven't looked yet, but am pretty sure such circuit designs exists.
However, the question is, do the costs plus the added complexity weigh up against the benefits (1.5V less powerloss, at ?? A). There's more things that can go wrong with active rectifiers than with diode-bridges. I don't think I would bother with them (unless the design was very simple and reliable), but there may be applications where this may a better solution than your standard diode bridge.
I did have a look at powerful Schottky diodes (Vforward = .2-.3V, instead of the .7-.8V of Silicon diodes), but so far (in my 2000 Farnell catalog) haven't been able to find any. This may be a much simpler solution than active rectifiers, but with a bit more loss.
Just some ideas that come to mind.
Peter,
The Netherlands.
