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400-800Hz 115VAC PFC (100w, 28vout) with dual interleaved flyback (isolated)
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ocset:
Hello,
We are thinking of doing an isolated dual interleaved Flyback PFC on 400-800Hz 115VAC input.
Its 28Vout +/-2V at 100W. (so that’s 50W for each of the flybacks of the dual)
We are certain that due to peak charging and poor cross regulation, we will not be able to do the vout regulation by regulating the voltage of a low power (<300mW) bias coil on the primary side….instead an isolated TL431/opto type feedback will be needed.
UCC28064A
http://www.ti.com/lit/ds/symlink/ucc28064a.pdf
…so We are going to have to drop a divider down from the primary side Vcc rail and pour the opto collector out into this, and then the divider point into the VSENSE pin of the UCC28064A.
This is more components than wanted, do you know why nobody does a dual interleaved flyback controller IC with a typical common emitter opto coupler connection?
Both flybacks will dump out into the same 28v output.
dmills:
Treez does aviation electronics? (28V DC, 400Hz AC is classic in that space)!
You are aware that anything going into that market has something of a gnarly development and quality process (And is actually expected to pass fairly stringent EMC for real).
:o :palm:
Someone:
--- Quote from: dmills on May 21, 2019, 08:23:57 pm ---Treez does aviation electronics? (28V DC, 400Hz AC is classic in that space)!
--- End quote ---
Military use 400Hz for some of their power standards too.
Its the brave new world, no need to hire engineers, just ask for their work/advice for free. The music industry went down this route too many years ago.
MagicSmoker:
--- Quote from: treez on May 21, 2019, 07:00:15 pm ---We are thinking of doing an isolated dual interleaved Flyback PFC on 400-800Hz 115VAC input.
Its 28Vout +/-2V at 100W. (so that’s 50W for each of the flybacks of the dual)
We are certain that due to peak charging and poor cross regulation, we will not be able to do the vout regulation by regulating the voltage of a low power (<300mW) bias coil on the primary side….instead an isolated TL431/opto type feedback will be needed.
...
Both flybacks will dump out into the same 28v output.
--- End quote ---
Why in the world would you resort to a dual, interleaved flyback for a mere 100W?! Interleaving flybacks only makes sense above 400-500W, and even then there needs to be a very compelling reason to use the flybacks vs. a boost PFC stage followed by a single two-switch forward (arguably the most economical and robust choice up to around 500W).
That said, the DCM flyback can automatically do PFC all on its own, so any conventional interleaved controller IC with an appropriate duty cycle range could work. I am rather partial to controller ICs from OnSemi and IR (now swallowed up by Infineon) and avoid TI like the plague; I've just had too many bad experiences with their recent chip designs and have sworn them off entirely as a result.
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