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UC3843: High current spike during start up

Brian Wang0
Expert 5310 points
Part Number: UC3843

Hi team,

Here is a question from customer. Basically they are driving a Buck converter with UC3843, but the start-up current is very large, even with soft-start circuit.

The scope is as attached. Please kindly suggest what might be the design defect. I could also share schematics internally via Email.

UC3843 large start up current.docx

Regards,

Brian

  • 0
    TI__Mastermind 31580 points

    Hi Brian,

    The first pulse is much wider than the other pulses. Can we have a look at the current sense pin waveform. Maybe the output inductor is saturating during start-up?

    Have they checked the current limit performance under short circuit, it could be similar.

    Regards

    Peter