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UCC28780: Abnormal output waveform vds

Eagle.Miao
Intellectual 910 points
Part Number: UCC28780


Blue: lower Vds; red: secondary winding current; green: primary winding current


Vin=230Vdc，Vo=16.5V，Io=3A

Vin=230Vdc，Vo=16.5V，Io=0.5A

Transformer turn ratio: primary side: secondary side: auxiliary winding = 20:3:10

Lm=150uH

How to Set Parameters R8？than you  

  • 0
    TI__Mastermind 27145 points

    Hi Eagle,

    It looks like the on time of Q16 is changing cycle to cycle. Are you able to measure the loop response of your converter? Perhaps it is not stable.

    Section 8.2.2.7 of the UCC28780 datasheet provides guidance for setting up the compensation network including R8.

    Best Regards,

    Ben Lough