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PMP8740: Current Sense Transformer Selection Procedure

Nishant S
Prodigy 51 points
Part Number: PMP8740
Other Parts Discussed in Thread: UCC28950, UCC28070

Hello,

Can anyone please share the step-by-step calculation and selection procedure for current sense transformer T1 used in PMP8740?

Also, please explain the significance of Volt-microsecond rating of the current sense transformer in the selection procedure. Is there any other parameter that must be considered in design of current sense circuit?

This has not been explained in the application note of UCC28950.

Thanks

Regards, 

Nishant

  • +1
    TI__Expert 5875 points

    Hello Nishant,

    The calculation about the current sense transformer for PMP8740 is very similar to the case of the UCC28070 300-W interleaved PFC; the guide to this EVM is available here:

    https://www.ti.com/lit/an/slua479b/slua479b.pdf

    On page 7, section 6, the calculations about CT turns ratio, magnetizing inductance and demagnetizing voltage are also discussed.

    The similarity comes from the fact that both phase shift full bridge and CCM PFC must demagnetize the CT during minimum off time (therefore at maximum duty cycle).

    Please let me know if that helps.

    Regards,

    Roberto