My concern about that approach is that those two voltages coming out of two different transformers may not be really symmetric. In order to get exact same voltage on both windings, I wind my secondary in bifilar fashion.
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120v SMPS without using input voltage doubler
- Thread starter hanair
- Start date
My concern about that approach is that those two voltages coming out of two different transformers may not be really symmetric. In order to get exact same voltage on both windings, I wind my secondary in bifilar fashion.
Margin width depends on creepage and clearance requirements of a standard document, which will have a table in it of different levels of insulation,and the environmental conditions in which it will be operated. It isn't as simple as always using 6mm creepage, 4mm is also a common one, especially in lower voltage telecoms which are popular for app notes. But yes, margins as in the diagram walls posted. Not 3mm thick between windings. 3 layers of thin tape between pri and sec.
Having multiple transformers with windings in series or parallel is certainly possible. There's something interesting I've read about but not seen where to get a very low profile, multiple transformers each with the same turns ratio have all their primaries in series and their secondarily in parallel, e.g 10 tiny transformers with a 1:1 ratio makes a 10:1 transformer. The power brick on my laptop is only about half an inch thick and 100W and I'm itching to destroy it to see if this is what they've done.
I don't know if you'd have to take measures to share current between them. You would have to do it in such a way that the flux is balanced in each transformer. This might concern you as I don't know how you're rectifying the secondaries, but the common centre tapped secondary with 2 diodes for rectification won't work if the 2 halves are on different cores for this reason.
Having multiple transformers with windings in series or parallel is certainly possible. There's something interesting I've read about but not seen where to get a very low profile, multiple transformers each with the same turns ratio have all their primaries in series and their secondarily in parallel, e.g 10 tiny transformers with a 1:1 ratio makes a 10:1 transformer. The power brick on my laptop is only about half an inch thick and 100W and I'm itching to destroy it to see if this is what they've done.
I don't know if you'd have to take measures to share current between them. You would have to do it in such a way that the flux is balanced in each transformer. This might concern you as I don't know how you're rectifying the secondaries, but the common centre tapped secondary with 2 diodes for rectification won't work if the 2 halves are on different cores for this reason.
Hanair, do you remember if the transformer was originally wound with margins and if so what they were.
I could not salvage the core, so I bought a few of EI33 and EI35 from Aliexpress.
"I could not salvage the core, so I bought a few of EI33 and EI35 from Aliexpress."
This was a surprise, i looked up the EI35 it has almost the same dimensions of the EI33 bobbin winding area. The EI35 core also has LESS Ae of .893, compared to EI33 of 1.18. This means you will need one or two more turns for your windings. This is the first example i have seen of going up one core size and being worse off.
This was a surprise, i looked up the EI35 it has almost the same dimensions of the EI33 bobbin winding area. The EI35 core also has LESS Ae of .893, compared to EI33 of 1.18. This means you will need one or two more turns for your windings. This is the first example i have seen of going up one core size and being worse off.
"I could not salvage the core, so I bought a few of EI33 and EI35 from Aliexpress."
This was a surprise, i looked up the EI35 it has almost the same dimensions of the EI33 bobbin winding area. The EI35 core also has LESS Ae of .893, compared to EI33 of 1.18. This means you will need one or two more turns for your windings. This is the first example i have seen of going up one core size and being worse off.
I was surprised too. EI33 looks bigger (thicker), but EI35 is a little taller (longer I). EI35 can accomodate a little more copper (more layer), I guess.
Having multiple transformers with windings in series or parallel is certainly possible. There's something interesting I've read about but not seen where to get a very low profile, multiple transformers each with the same turns ratio have all their primaries in series and their secondarily in parallel, e.g 10 tiny transformers with a 1:1 ratio makes a 10:1 transformer. The power brick on my laptop is only about half an inch thick and 100W and I'm itching to destroy it to see if this is what they've done.
I have seen those to. It seemed to me that there would be very poor coupling in each core.