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Original question:

UCC256402: IC doesn't work below 26V

UCC256402: How to measure Resonance current

Jeff Xie
Intellectual 1780 points
Part Number: UCC256402

Hi all,

Customer want to know how to measure the resonance current, as they use current probe and noise is very big, thanks.

  • 0
    TI__Guru* 86166 points

    Hello,

    The should be able to measure the input current to the transformer with a current probe.  It should be a sine wave that tracks switching frequency.

    Figure 23 in the EVM user's guide shows what the current and it is quite clean.

    If they are having a noise issue maybe they don't have there current loop in the correct place.  Make sure they put it in series with the input of the LLC transformer/

    The other thing is make sure the current probe and/or wire is not on top switch node.  This could EMI coupling and could put noise on the circuit.

    They also should be able to see a representation of the resonant current at the ISNS pin.  This does not require a current sense probe.

    Regards,

    Mike