3KW PFC topology

[mrinalmani]

Hi
We have to design PFC with multiple power outputs ranging from 3KW to 10KW. Input voltage range 160V to 280V and output voltage = 400V. Up till now I have only designed and tested between 200W to 800W. I especially liked CrM topology over CCM, they simply run very smooth and cool.
I was thinking of using an interleaved architecture with roughly 1KW to 1.5KW per channel. This would mean close to 8 channels for a 10KW PF. There are controllers like the UCC28070 that can accommodate several channels( phases) with the help of external phase shifted synchronization signal. But this is CCM not CrM.
- Should I prefer CrM for >1KW PFC?
- Instead of increasing channels as the power increases, would be nice to just stick to say 3 channels and increase inductor and switch size? What is generally done? Increasing channels or increasing component size?

Thank you

 

[treez]

BCM (=CrCM) used to be good before SiC diodes came along. It has high switching frequency at lighter loads.
Power Integrations are now doing highly efficient CCM PFC control chips with their HiperPFS range....even as low as 100w..showing that CCM is the new hero of PFC....if you look at their efficiencys they are very very good , and from CCM operation.....Just need to use SiC diodes, or soft diodes eg Qspeed.
The UCC28070 doesnt have to be done in CCM, but its best to do so because at higher powers the delta B in the ferrite is very high...also, their is much more need for Litz in BCM PFC inductors at higher powers.

We reverse engineered a good offtheshelf 3kW offline battery charger....it had a PFC which was controlled by a single controller, but it was two PFCs...and they were 10ms ON, 10ms OFF, interleaving......they used torroid inductors, and i guess they were some kind of non linear magnetic material like sendust etc.

 

[Easy peasy]

SiC diodes do allow 1.5kW and bigger in CCM these days - a lot less noise from the diode/mosfet at switch on...

we have done 2 channel CrCM to 1.5kW and it was very good - RFI quiet, and low stresses on the mosfet - and we could use any old low Vf 600V diodes for the boost diodes (even 50nS Trr ) - the only drawback was good quality caps were needed on the rectified mains to supply the pulse currents - I would happily go to 2kW with this, then 5 modules gives you 10kW - happy hunting ...!