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Old 10th April 2005, 03:15 PM   #31
Alme is offline Alme  Ukraine
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Let me join this interesting discussion and share my modest PFC and converter design experience here
Chocoholic, I have tried fixed-frequency continuous mode PFC based on L4981A a few times and this is what I recommend for higher power application, especially that you will desire to synchronize it with next stage converter.
Here is additional info on it by STM.
http://www.st.com/stonline/books/toc/an/1212.htm
I made my 500W PFC just like they suggest in their application note, with smaller additional inductor (this seems to be similar way as Eva suggests here).
What do you think about this chip?
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Old 11th April 2005, 03:29 AM   #32
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Default L4891a

Alme - Eva,

WOW! This chip looks pretty cool! I will try and get some samples to play with. I very much like the idea of synchronization.

While on ST's website, I noticed an application note about an L4891A-based "Bridgeless" PFC rated at 800W. The two lower bridge diodes are replaced with two N-Channel MOSFETs and driven synchronously by the PFC chip. The boost inductor is placed ahead of the MOSFET-diode "bridge", and according to ST, is very useful for Hi-power PFCs, where power disspiation in the diode bridge becomes a concern. Here is the link to that PDF file:

http://www.st.com/stonline/books/pdf/docs/9119.pdf


Just goes to show ya': spmeone is always thinking outside the box!

Steve
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Old 11th April 2005, 09:35 AM   #33
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Yes, quite cool circuits....
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Old 22nd December 2005, 10:04 PM   #34
mzzj is offline mzzj  Finland
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Quote:
Originally posted by Eva

The input diode bridge is placed in an external heatsink and the EMI filter is not shown. I've successfully tested it up to 1.7KW continuous with proper cooling at 450V output and 160V AC input, however the board has space for additional components in order to get up to 4KW theoretical maximum output. Currently I'm using SKP20N60 IGBTs and MUR860 diodes combined with a coupled inductor that works as a magnetic snubber and contols the dI/dt at turn-on [and also at turn-off as a side effect]
UP we go.
two IGBT's and diodes parallei or how?

Do you have you any fiqures for effiency at 1.7kW?

I have been wondering similar project, ie 4kw PFC stage for a while now. Availlability of MPP cores just bugs me off
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