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UCC25630-1EVM-291: Slow start time at no burst

Hiroshi Doi35
Expert 2845 points
Part Number: UCC25630-1EVM-291
Other Parts Discussed in Thread: UCC256301,

Dear all,

My critical customer does not want burst mode because of high ripple output.

I think he will remove the RLLUpper.

My customer asking me;

1. Slow start time ? ms  ( at no load and max.10A load)

2. Does slow start time relate to another factor such as AC input voltage, and so on?

3. Does ZCS detection and keep safety function alive all time during soft start with a moment?

Thank you,

  • 0
    TI__Mastermind 27145 points
    Hi Hiroshi san,

    Thank you for your interest in UCC256301.

    1. On UCC25630-1EVM-291, the startup time looks to be close to 30mS. Startup waveforms at no load and full load are shown on page 13 of the EVM user guide:www.ti.com/.../sluubq8a.pdf

    2. Soft start time is related to the charging current and the capacitance placed on the SS pin. The smaller the capacitance of the SS pin, the faster the capacitor is charged up and the shorter the startup time will be.

    3. I will need to check with the design team if ZCS detection is active during startup.

    Best Regards,
    Ben Lough
  • 0
    TI__Expert 7310 points

    Hi Hiroshi,

    1, You can reduce C17(the capacitor on SS pin) to make the start up faster

    2, No

    3, yes, ZCS detection is always there even during start up.

    Regards,

    Bosheng