Might as well post some synchronous rectifier circuits
June 5, 2007
I’m pretty sure these will work. Their main innovation is that they are self-powered, using the amazing op-amps that appeared while I was napping for 20 years.
I realized, in the middle of a trip to Silicon Valley a couple of months ago, that I was thinking about this circuit wrong, and that I needed to be careful about just how the op-amps would behave (within the limits of the power supply). The main problem was that I needed to remember the assumption “zero volts across the inputs to the op-amp” once I had put the negative feedback in place. Thus, the 8-volt zener diodes. One thing missing from this diagram are the V+ and V- connections to the op-amp itself; those come from the DC power supply itself. The Shottky diodes in parallel with the MOSFets are intended to help the circuit get bootstrapped at low voltages — a better op-amp would allow lower voltages, yet.
I’m not working in surface mount, because I am a Neanderthal with big clunky fingers, even though the surface mount parts are better. Assuming this circuit works as it is supposed to, I’ll look into that next.