I have read the #slua287 technical article detailing the basic operation and relevant waveforms of Control-Driven SR... but I still cannot grasp the concept.
I see that the currents in the output circuit are rather complex. But for starters, the current paths illustrated (even in the "easier method") do not make sense. They indicate that the current flow (in either half cycle) appears to enter the source terminal of the mosfet and leave the drain. Therefore the current is through the body diode, as it is forward biased. This would be the case for passive rectification as well, in other words, by just using "plain" diodes. (The FET appears to be doing nothing.)
So what benefit does replacing diodes (FRED's) with MOSFETs actually have, if the body diode in the FETs appears to be doing all the work?
Apparently there is more nuanced operation I am not seeing as yet. So is there a more detailed article that explains exactly how this scheme works, and how the MOSFETs achieve better efficiency than diodes?
I assumed that the main current would flow through the FET itself, and not through the body diode. This would obviously replace the forward drop of the diode with the low Rds-on of a FET, thereby reducing conduction losses. As far as switching losses, I obviously don't see what function the FETs are serving and therefore have no idea as to how a benefit is realized.
1. Does forward current flow into the drain of the FET at all?
2. Or does the N-channel FET operate in "reverse-biased" mode (with the drain being negative with respect to the source), thereby "shorting out" the diode when it should be conducting anyway? At least that would make sense to me, although I've never seen anyone operate a MOSFET that way....
I apologize for the lengthy inquiry, and thank you in advance for a "layman's" answer to this rather puzzling question!