Many clearance lengths needed for offline topswitch flyback
Hi,
Would you agree, if doing an offline isolated flyback of 90-265vac, then the minimum number of net class's that you can get away with , when laying out the PCB, is ten?
The net class's are necessary, ayk, so that you can get the correct clearancing between the various nets. Some nets will obviously be in 2 or more of the net class's.
(If you like , Take a 84/19 transformer, 20W and 24vout and 65khz, or therabouts.)
As you know, switching node is the highest voltage pin, but is after the fuse etc etc.....many different voltage class's...so many net class's needed...for doing the different spacings, woudl you agree?
https://www-eng.lbl.gov/~shuman/NEXT/CURRENT_DESIGN/TP/MATERIALS/IPC-2221A(L).pdf
...IPC2221A leaves so much to question regarding clearances, its unbelievable, would you agree?
Hello Treez,
Unfortunately, I’m not sure about the min. number of net class when laying out the PCB with regards to IPC2221A.
What I can share in terms of safety clearance for PCB, is you may also have to consider the spacing requirement according to the standard of the intended application of the power supply to be certified. For our case, although, our product is an IC component only, we used an IEC 62368-1 equipment standard as reference and such is a certification which we also obtained for our isolating products evaluated for Reinforced insulation as a prerequisite for the power supply or end system certification. For the spacing requirement after the fuse of the same primary circuit requires functional insulation only (insulation that is necessary only for the correct functioning of the equipment and does not protect against electric shock).
Regards,
Kazuya