i have designed a 30W Led driver (33V@1.05A) based on DER-286 and i am having some issues to make it work properly.
In the first prototype, i have used a transformer based in an old EER28L NICERA core i have at home, but for production those cores are not very easy to find here in Argentina; so i decided to use the COSMO CF-139.
The issue is that the first prototype (exactly the same pcb as DER-286, but only RFB changed to 100K) was working with the prototype transformer and now the same pcb is not working with the final version of it.
On the other hand, the second prototype (attached image, only the layout was changed to fit inside our box) seems to have something different since the RFB needed is 151K instead of 100K and also it is harder to make it work avoiding the protection status.
I have used the tunning seccion in the PIXLS spreadsheet trying to adjust RFB, RV1 and RV2 without success.
With RFB=151K is not protecting and the measured values are:
Playing with the RFB values the better i can get is Iout=0.78A but i can't reach the 1.05 Amps needed.
Has it something to do with the differences in the losses or permeability between Nicera and CF139?
Is there any way to change the core material properties and recalculate the transformer in PIXLs?
What am i missing? What do you reccomend me to do?
Attached are the PIXLs design, the schematic, the pcb, CF139 datasheet and some pictures of the second prototype board.
Thank you very much in advance,