[egg on face] My digital background is showing again. I am accustomed to using spiffy new power mosfets as switches and making transistors do the hot, sweaty work of linear regulation so I saw Q2 as a switch to remove power from the output if the voltage or current settings were ever exceeded and kept expecting to see a power transistor just beyond Vin. That was why I thought VFeedback might be only a digital input to the voltage regulating function of the micro, or to some other analog circuit also just beyond Vin. Now I understand some of what didn’t make sense before.
I can’t find any listings for 1F34AD but I did find one for FDA38N30 with a 312W max rating. I assume Q2 is a power mosfet designed to operate in the linear region without thermal runaway (current focusing?). And now I agree completely with 1.21Gigawatts about keeping VFeedback on the same side of the fuse as the device it is controlling. And I take it that Q4 is not an over current crowbar switch that shorts out the voltage feedback whenever the current is exceeded but actually modifies the output of U5B to lower the output voltage until the current drops back down to the limit setting? I still tend to think of them as switches and if you used them in a feedback setting like this they would oscillate until they found their resonant frequency. Still hard for me to think of them as only operating in linear mode under their safe operating area.
Which leads me back to one of the other concerns us digital guys try to avoid. With the direct feedback and only two 47uF caps to dampen things out, isn’t there some concern that this could start a high frequency oscillation in either voltage or current regulation mode? Especially with the two driver op amps being operated at full gain with no feedback? I am guessing that a small, high frequency cap from VFeedback and IFeedback to ground to short out a high frequency AC component and still allow the DC regulation to operate unchanged would help with that. Or is that just something the analog guys would tell us in class to scare us and keep us in line ?
One more feature I would suggest considering since you already have Vset, Iset, a rough estimate of Vin, and an LCD display is to compute the maximum power dissipation for (Vin - Vset) * Iset and compare that with your derated power rating given your heat sink and fan combination and warn the user if it might lead to overheating before the fans reach top speed. Might as well show off all those fancy things you have already included!