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UCC28056: PFC for AC-DC Flyback

BRANDON WEATHERLY
Prodigy 60 points
Part Number: UCC28056
Other Parts Discussed in Thread: UCC28700

Tool/software:

Hi!

I am wanting to design an AC-DC converter with this chip that will have the following topology: 

AC IN (120V @ 60 HZ) > EMC FILTER > PFC (400V OUT) > FLYBACK (12V OUT)

Most flyback controller chips don't normally accept input voltages much higher than 75V. How is this voltage normally stepped down prior to the flyback stage?

  • 0
    TI__Mastermind 40580 points

    Hello Brandon, 

    You may be looking at a series of low-voltage flyback controllers with integrated switches. 

    There is also a series of flyback controllers designed to work "off-line" from either full-wave rectified and filtered AC or from a PFC output. 
    The controller doesn't see any of the high voltage directly, but it controls a switch (usually a MOSFET) that drives a transformer to step down the PFC output.
    Since your interest is more focused on selecting a suitable flyback controller, I suggest to close this thread and post a new E2E thread with "UCC28700" in the title to have your questions routed to the correct support group. 

    Note: if your AC input is only 120V (+/-X%), then it is not necessary to boost your PFC output all the way up to ~400V.  You can set it for < 200V and select lower voltage semiconductors, capacitors, and other components for your conversion.   
    The same flyback controllers will work at that voltage, too. 

    Regards,
    Ulrich