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Design recommendation pfc 5kw

yelsing torres
Intellectual 340 points
Other Parts Discussed in Thread: UCC28070, UCC28180, UCC25600

Hello
I need to design a pfc with an output of 5kw. The drawback is that I need a 110Vdc output, with an input of 120vrms. Having an output voltage lower than the input voltage, I can not use a boost converter as in the vast majority of cases. I can not use a buck converter either because its thd is higher than 5%. Could you give me some recommendation?
I have thought to raise the voltage to 400vdc with a boost converter, and then rerduce it with a 110vdc with a buck converter, but it could be expensive. I also thought about the possibility of using a sepic, but I have never used this type of converter, and I do not know if it is recommended for the power of 5kw.
Thank you very much

  • 0
    TI__Mastermind 25570 points
    Hi Yelsing

    I'm not familiar enough with the SEPIC topology to offer an analysis but I would say that the 'usual' way of doing what you intend is to build a 2 stage converter - an input Boost PFC and an output DC/DC. At this power level I'd suggest an interleaved Boost PFC using the UCC28070 CCM PFC although it is possible to built a single phase boost PFC using the UCC28180 for example. You just need to understand the currents in the system and choose components accordingly. For the DC/DC stage, if Vout does not vary very much (10% or so) you could use a full bridge LLC (UCC25600 or UC25630x). If Vout vary widely (2:1) then a phase shifted full bridge would probably be better. Both the FB-LLC and PSFB solutions could be built as a single stage but it is more usual to build two 2.5kW stages and parallel them - or 3 1.7kW stages in parallel

    If you are looking at the SEPIC then check the component stresses at the power level you are interested in and see if they are 'reasonable' when compared to the boost PFC / FB-LLC or PSFB solutions.

    Regards
    Colin