3 phase should be isolated units using L-L for lower current draw; 
	note N can be common! but not power grounds for PFC controllers


3 unit vsense control algo:

clock 600kHz divide by 3 into shift register;
apply to each supply via narrow pulse width one-shot into sync using isolated signal (opto?)

for each da,db,dc take difference of currents (and vsenses?) da=a-(b+c)/2, 
  multiply by G=2/3, add to current and/or vsense a (causing it to command decrease by da) 
  via isolated signal; opto? use op-amp to command linear current in emitter at Ve >=0.2V 
  resulting in linear current in phototransistor centered at Ip that yields desired voltage gain;
stable?


best would be to use a global fixed Vref for Vn feedback,
	but it must be slow compared to Vn feedback loop


actual load sharing: equalizing instantaneous work done by each;
        low-pass filter In to same timescale as Vn
	use Ptot=sum(In*Vn) as reference for Pn feedback control
        calc dPn = In*Vn - Ptot/3 --> 3*dPn = 3*In*Vn - Ptot
        is current command usable? not sure; need 
        current command: need dPn=0 --> 0 = (In+dIn)*Vn - Ptot/3
        --> dIn = (Ptot/3)/Vn - In
        equiv voltage command: need dPn=0 --> 0 = In*(Vn+dVn) - Ptot/3
        --> dVn = ( (Ptot/3) - In*Vn )/In = (Ptot/3)/In - Vn
        when loads are small, de-emphasize power correction; 
        perhaps gain is proportional to some function of total power/current



detect phase voltage deviations, beyond some threshold, disable load sharing


