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Original question:

LM5035: what circumstances the chip will output this waveform.

LM5035: Soft-start not work

Gabriel Wang1
Genius 4715 points
Part Number: LM5035

Tool/software:

Dear Expert

The application is input 160V to 576V AC and output is 24V 200W .

When the low voltage is 160V input, there is no soft start process, and the width of the switch is always around 1.6uS, not gradually increasing. There is a soft start process when the high voltage is 280V input.Could u give us some suggestion why there is no soft-start?

  • 0
    TI__Mastermind 32895 points

    If the SS is not operating correctly at low input line (highest input current), check to make sure the converter is not starting in a overload condition. Make sure the converter is not entering a hiccup mode during 160V startup. Check the waveforms at RES, CS, SS and LO (measure directly at IC pins) during 160V input compared to 280V input.

    Steve