UCC27511: Ref. Design PMP3162: What is the function of R3 (O.1R) connected across the primary winding of the current sense transformer T2?

Fraser Lawson1

Prodigy 240 points

Part Number: UCC27511
Other Parts Discussed in Thread: PMP9656, PMP3162, PMP8861

Tool/software:

Hello, Texas team.

Background

I am considering the reference design PMP3162 (and also PMP9656) for a possible new application.

Both of these reference designs have a 0.1R resistor (R3) across the current sense transformer's (T2) primary winding.

Other active clamp forward converter reference designs don't have this resistor, e.g. PMP8861.

Question: Could you please explain what the function of R3 is please?

Best regards,

Fraser

1 month ago

0 Annabelle Alemand 1 month ago

TI__Prodigy 670 points

Hello Fraser,

Thank you for your question. R3 helps damp any high frequency spikes that occur during turn off of the primary FETs. PMP3162 and PMP9656 are higher power reference designs than PMP8861, which is why they have R3.

Thanks,

Annabelle

0 Fraser Lawson1 1 month ago in reply to Annabelle Alemand

Prodigy 240 points

Thanks, Annabelle.

Much appreciated.

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UCC27511: Ref. Design PMP3162: What is the function of R3 (O.1R) connected across the primary winding of the current sense transformer T2?