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UCC2819A: UCC2819A question ( IAC pin)

Masazumi Ishii
Genius 3945 points
Part Number: UCC2819A
Other Parts Discussed in Thread: UCC2818

Hello.

I have a question about UCC2819A.

UCC2819A During evaluation, the input voltage and current oscillated, and the PFC coil sounded.
Symptoms disappeared by attaching a capacitor to the IAC terminal of UCC2818.
When such symptoms occur, are there countermeasures cases?
Is there anything to note about adding capacity to the IAC terminal?

thank you.

  • 0
    TI__Mastermind 34465 points

    Hello Masazumi,

    You don't give any information on when this problem occurs.
    Is it at full load or light load, high line, low line or just all the time ?

    The IAC input is the line frequency input to the multiplier.
    What may be happening is that some switching frequency noise is getting into this pin and causing problems. It may be that the capacitor on the DC side of the bridge is too small perhaps. Or you can sense IAC before the bridge rectifier and add two separate diodes on IAC if the main bridge is not used.
    Or you can add a small capacitor on IAC provided the time constant is much less than the rectified line frequency.

    Regards

    John