I am using lt1248 in ltspice to do an equivalent one, but i cannot simulate ucc28070.
Incidentally, the UCC28070 is unuseable in our application because one simply cannot vary the output voltage of the ucc28070 based PFC...this is because if we do it like in post#1, then we will violate the requirement that the VINAC divider ratio be the same as the VSENSE divider ratio.......so our design has just been blown out of the window.
This is as per page 19 of the UCC28070 datasheet.
Serves us right for trying to use a multi-functional controller and "hack" it to have extra functionality....stupid of us, we should have just picked a dead simple 8 pin PFC controller in the first place.
UCC28070 datasheet
https://www.ti.com/lit/ds/symlink/ucc28070.pdf
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I reckon we might be able to use the FAN9672, which has a separate pin to vary vout. I believe this can be used with current sense transformers, which we would prefer as its less noisy especially when two interleaved stages are used.
FAN9672 PFC controller ic
https://www.mouser.com/ds/2/149/FAN9672-348136.pdf
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I wonder why the UCC28070 PFC controller needs to do inductor downslope synthesis , but the FAN9672 does the same job as UCC28070, and in the same way, but doesn't need to do inductor downslope synthesis?