Hi
I did your flyback in LTSPICE. It is attached for you….This is the free sim from analog.com…..you can run it by simply converting it to .asc instead of .txt
I gave you a vac input of 180-240vac so apologies if this is not what you have?
Your transformer seems ok, as long as you have it clamped together properly.
I did it for you with 38 turns of swg22 in two “sandwich layers” for the primary…for the sec I gave you your 11 turns made up of two strands of TEX-ELZ 7/0.15.
I used your efd25/13/7…the flyback and transformer design calcs are attached.
As to your not getting max power……well, you don’t need slope compensation, so take that off...…….then youll get more power through on the same sense resistor.
Also, I haven’t been through your startup circuit yet……also, I haven’t done it with opto isolation as this was just a basic checker.
I also changed your RCD clamp as yours looks too dissipative…see the sim for what I gave you there. (again this is based on my assumption of 180-240vac input)
You are obviously having trouble……so in the first instance…connect pri and secondary grounds and get rid of your opto…just set it up with a straight resistive divider feedback.……….like I do in the sim……then when you have that working…go back and sub in the opto etc
Be careful with live non-isolated mains….and use a diff probe just in case…do you have an isolated AC source?
BTW what is your exact vac input?....i assumed 180-240vac for you..
EFD25/13/9 TDK EPCOS.
https://www.tdk-electronics.tdk.com/inf/80/db/fer/efd_25_13_9.pdf
- - - Updated - - -
Actually I re-did the excel calc for your transformer turns ratio (as attached) ……..you are in CCM even at 339vdc on the HV bus…….to be honest, your transformer turns ratio is too high…ie NS/NP is too high….
CCM is bad for offline low power flybacks due to the reverse recovery of the secondary diode.
In the words of the Chief Engineer of a huge global electric drives company in the North East of England…”All Offline flybacks should be in DCM (or BCM)”
- - - Updated - - -
Oh heck sorry, I am having a bad day…I accidentally did the sim at 135khz…..and then left the incorrect 66khz annotation on there……here it is corrected and re-attached for 100khz…woops!
- - - Updated - - -
Also, have you got an isolated DC supply?...if so...just in the first place use that to power the uc3843 with...dont use the aux or the rc startup circuit.
Get it down to the bare bones and get that working..then start to put the rest in.
Did you use multi strands for the sec?...did you interleave wind?