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Original question:

[FAQ] TPSF12C1 and TPSF12C3 power-supply filter IC FAQs

TPSF12C3-Q1: Inject on live

Christopher Risse
Prodigy 10 points
Part Number: TPSF12C3-Q1

Hey Tim,

I have a question about the connecton of the Inj-Cap. Normally the AEF injects the current on the neutral line. 

It should also be possible to inject on any phase (e.g. L1), or does this reduce the effect of the AEF?

This question comes up due to touch current measurements. We saw an big impact on using the AEF while running the unit in normal operation. But if the neutral and live gets swapped the touch current measurement was worst than the original measurements (Should be worst because of the inject cap in parallel to the sense cap on neutral)

We have a bigger space to the limit in running the unit in normal operation. So we are thinking about to inject on the live, so the normal measurement gets a little bit worst and the worst case measurement (L1 and N swapped) gets better.

Maybe you can help me with my question.

Best regards 

Christopher

  • 0
    TI__Guru 73502 points

    Hi Christopher,

    It shouldn't really matter to inject on Live or Neutral. In general, we recommend the power line that's easiest in the layout. Note also that you can split the inject cap into two and inject onto both live and neutral. This maintains a balanced system.

    It would be good to review your touch current measurement schematic. My understanding was that Live and Neutral were equally applicable for that measurement. The sense caps of 680pF shouldn't make a big difference, unless your touch current spec is super low.

    Regards,

    Tim