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Original question:

LM51551-Q1: Cross regulation of flyback

LM51551-Q1: LM51551-Q1

song.lin
Prodigy 150 points
Part Number: LM51551-Q1

For the application of flyback, there is an issue. When the flyback's load is light, the transformer whistling.

Then I measure the SW of LM51551-Q1, the duty cycle is one big, one small.How can I handle this issue? Thanks!

Is that related to the balance of loop. Can we optimize the Comp circuit? How?

  • 0
    TI__Mastermind 19650 points

    Hi Song,

    Thanks for using the e2e forum.

    I would recommend to check both the loop compensation at COMP and the slope compensation at CS.
    We have a quickstart calculator tool to check if the chosen compensation should lead to a stable operation and also tells if external slope compensation is necessary:
    https://www.ti.com/tool/download/SNVC240

    The schematic also shows that there is no RC filter at the CS pin, which can also add additional stability to the system.

    Best regards,
    Niklas