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UCC28063: AC-Impulse Noise Test issue

KIM Andy
Expert 2530 points
Part Number: UCC28063
Other Parts Discussed in Thread: , UCC28061

HI

My client is designing 270W smps with ucc28063.

PFC IC TSET Nosie - Tset voltage increases during impulse test, and PFC operation is not performed.

AC-Impulse Noise Test

This test is applied for 5 minutes, and the AC input for the AC-line is for the high-voltage spikes ranging from 500 V to 2 kV at any phase angle, repetition rate, and polarity.

Could you explain the behavior of tset?

Could you tell me how to improve it?

ch3 : Vtset, ch4 : SW Voltage

  • 0
    TI__Mastermind 34465 points

    Hello Andy Kim,

    The TSET pin has a fault protection feature that may be triggered during an AC impulse test.

    This protective feature causes a COMP discharge latch and full soft start if the UCC28063 detects either a short circuit or open circuit on the TSETpin.

    The performance cqan be improved by :

    (1) Routing the TSET resistor on pin 3 directly to AGND and away from VSENSE on pin 2.

    Pin 2 is most likely to have some high impulse noise and this can be coupling into TSET.

    So minimize distance from RTSET to TSET and minimize trace length from RTST to AGND

    (2) It may be that the impulse noise is being capacitively coupled from the enclosure to TSET.

    In this case a shield around TSET or the UCC28063 will help.

    (3) The UCC28063A is similar to the UCC28063 except that it does not have this TSET protective latch.

    Please check operation with the UCC28063

    Also the UCC28061 does not have this latch

    1263.Doc1.docx

    Hope this helps

    Regards

    John

  • 0 in reply to John Griffin1
    Expert 2530 points
    HI John,
    TSET PINS requires correct factor value for TSET pin short circuit or open circuit detection.
    If you detect voltage or current levels, please check exactly what conditions the circuit will stop switching.
  • 0 in reply to KIM Andy
    TI__Mastermind 34465 points
    Hi Andy,
    As I explained TSET will pick up noise during the test that is most likely causing the pfc to turn off.
    Regards
    John