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LM3481-Q1: LM3481 Lm calculation check

Part Number: LM3481-Q1

Hi Team,

Based on LM34xx How to Design Flyback Converter with LM3481 Boost Controller (Rev. A) (ti.com.cn), my calculation of Lm is about 110uH as below.

VIN=32V Vout=12V. others are same as below. 

However, in chapter 4, it says it is 12uH. 

Could you please help to check if anything wrong with my calculation?

BRs, 

  • Dear team,

    Could you please check this question when convenient? 

    BRs. 

  • Hi Daniel,

    Thanks for using the e2e forum.
    The formula in the app note look okay to me, so there should not be any error here.
    The inductance choice highly depends on the calculation for CCM or for DCM operation, and where the desired load setpoint for a switch between CCM and DCM is set.

    Let me summarize the general calculations for a Flyback controller:

    There are different ways to calculate the inductance for a flyback.
    The appnote calculates based on CCM operation, for typical load. For light loads, the device will switch to DCM operation.
    For another example, the following equation returns a inductance where the flyback will operate in CCM down to a load of 10%.

    To visualize when the device will switch from CCM to DCM operation, you can use our Power Stage Designer tool.
    https://www.ti.com/tool/POWERSTAGE-DESIGNER
    Simply click on the Flyback topology, enter all parameters an double click und the inductor in the schematic to see the current waveforms.

    Please let me know if there are open questions on this topic.

    Best regards,
    Niklas