PFC for constant voltage Supply
Posted by: jlhessler
on
Hello,
I am designing an 18V 1.8A power supply using a TOP-HX device operating from 85-265Vac. Is it possible to adapt the schematic from der-136 or der-167 which are constant current PFC corrected designs to this 18V design which is constant voltage and maintain PF? Will the slow loop response cause instability in a constant voltage design?
Thanks
Jason
๋๊ธ
the slow voltage loop response means you cannot get constant voltage output like a normal smps i am afraid.
though you can get it fairly smooth by having lots of output capacitance.
Your power rating is below 50w (EU limit) so you dont need great pfc....(as long as its not for lighting where the ,limit is 25w in europe)
so maybe you can modify your pfc cct so that the voltage loop is a bit faster giving you a compromise between pfc and voltage regulation.
To get a decenty voltage transient response you need a loop gain of some few KHz, so the 20Hz of a normal pfc is nowhere near your requiremnt.
Good answer Treez,
Thanks
PI-Chekov
