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UCC28070: UCC28070

Tapajit Mondal
Prodigy 185 points

Part Number: UCC28070

Tool/software:

I am designing a power supply of specifications are Input: 230VAC 50Hz and Output: 180VDC 15A.

I want to confirm my design for the EMI/EMC and PFC. and want guidance for  the values of component selection for PFC IC UCC28070 

  • 0
    TI__Mastermind 40580 points

    Hello Tapajit, 

    Thank you for your interest in the UCC28070 PFC controller. 

    I cannot advise you on the effectiveness of your specific EMI filter, but I can suggest that the connections for CY2 and CY3 don't make sense to me.  

    Since your design is for high-line input only (230Vac with some +/- tolerance), I recommend that you follow the design procedure shown in the applications section of the UCC28070A datasheet: https://www.ti.com/lit/gpn/ucc28070a  (starting page 33).  The UCC28070 datasheet and the Excel calculator tool have not yet been updated to the latest design procedure as is provided in the UCC28070A datasheet.  The non-updated documents will give you incorrect results for a high-line only design such as yours.  

    Regards,
    Ulrich

  • 0
    Prodigy 185 points

    Dear Ulrich,

    We have design the circuit same as mentioned in the UCC28070A  datasheet. i want your guidance for choosing the right frequency value for the PWM Frequency, Dithering Frequency and External Clock Synchronization frequency.

  • 0 in reply to Tapajit Mondal
    TI__Mastermind 40580 points

    Hello Tapajit, 

    If you are going to synchronize the UCC28070A switching frequency to an external clock, the UCC28070A datasheet describes how to do it in Section 6.3.4 on page 18.  When using the external SYNC function, frequency dithering is also accomplished by the SYNC signal. 
    In other words, your SYNC clock must vary by the magnitude and rate of desired dithering.  

    Please note that the RT setting must be low enough to accommodate the lowest SYNC frequency when dithering is active.  

    I'm not sure how to advise you of what center frequency to choose.  That depends on several trade-offs to be made.
    Lower frequency (< 75kHz) can have lower switching losses and may have an EMI advantage, but requires larger inductors. 
    Higher frequency (> 200kHz) can reduce inductor size and also may have EMI benefits, but will have higher switching losses unless you use GaN or SiC MOSFETs. 
    Middle frequencies operate in the middle of the tradeoffs. 

    Unfortunately I can't be more specific than that.  This is a choice that you will have to make, based on your evaluation of the tradeoffs of one frequency versus another. 

    Regards,
    Ulrich