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UCC28070: Current sense transformer reset network

Matteo Labadini
Prodigy 20 points
Part Number: UCC28070

Hi all,

I am designing an interleaved pfc and as controller I will use the UCC28070.

I have a question about the current sense transformer reset network:

I know the common solution suggested on the TI datasheet made with a diode and a resistor on the secondary side of the current sense transformer, but do you know if it is possible to design a reset network on the primary side made just with a diode? Would this have any advantages respect to the standard solution made on the secondary side? I ask this because the power module I will use for the pfc is equipped with a diode thought just for this purpose and I wonder if it worths trying to use it.

Thanks in advance for any suggestion ot comment.  

Matteo

  • 0
    TI__Genius 11350 points

    I think it could work in theory, but the ultimate goal is to achieve V-s balance.  It will work if you can guarantee that the V-s product of the diode Vf on the primary reflected through to the secondary during the off-time is > or = the maximum V-s product on the secondary during the on-time.  However, this is tricky because the off time will be very narrow at max D and also high temperature will reduce Vf of the diode.

    If a wide off time (<50% D) can be guaranteed, it may work but I'm not sure it's practical with a PFC controller which can run up to D ~95%.