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UCC28950EVM-442: UCC27714EVM-551 choice of H-bridge switching frequency

Nitish Agrawal
Expert 1545 points
Part Number: UCC28950EVM-442
Other Parts Discussed in Thread: UCC28950

Hello,

Switching frequency of H-bridge in these evaluation boards appears to be set to ~100kHz.

1)  I am considering switching at a higher frequency (say 250kHz ~ 300kHz) to reduce magnetics size, while not sacrificing efficiency.  Would this be advisable at this power level?

2)  What factors were considered when choosing 100kHz for this eval board at the 600W power level?

Regards,

Nitish

  • 0
    TI__Genius 9140 points

    Hi Nitish,

    the engineer is on holiday this week, please allow the delay response of this post.

  • +1 in reply to David Huang33
    TI__Guru 70355 points

    Hello,

    Please note the EVM affective switching is 200 kHz (Secondary Frequency), the primary is only at 100 kHz.

    If the only thing you are doing is increasing the switching frequency the output inductor and transformer need to be changed.  However, you should double check the capacitors to see if they can handle the higher frequency RMS currents since the EVM was design for 100 kHz on the primary and 200 kHz on the secondary.

    The higher switching frequency's will cause higher gate drive losses and SR FET losses.  The primary FETs may not need to be changed but the secondary SRs might need to be changed.

    The following link will bring you to an application note that goes through the step by step design process of a PSFB using the UCC28950.  There are equations for estimating semiconductor losses based on switching frequency.  This should help in evaluating the design.

    https://www.ti.com/lit/pdf/slua560

    There is also an excel design tool based on the slua560 application note that you can use as well to check your design.

    https://www.ti.com/lit/zip/sluc222

    Regards,