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LM5021: Question about CCM mode and DCM mode

Part Number: LM5021

Hi, 

My Customer is using LM5021 as a Flyback controller in DCM Mode, but somehow it has some problem with a load about 30w. It seems that the LM5021 is switching between CCM and DCM mode. The yellow line in the picture is the voltage of the drain of Mosfet. Blue line is the current. what may cause this kind of problem ?  Thanks!

  • Hi Manu,

    you can check with the MOS VGS waveform , it looks like trigger the OCP after the leading edge blanking time.

    if the VGS on time is around 90ns , you can try to increase the CS pin filter.

    you can refer the datasheet 8.2.2.6 section.