LM51561: Inductor calculations for wide input range sepic converter

Thanks for the reply, yes i know about all the design tools, and i have been using them so far already, as well as WeBench but that doesn't clarify my issue. Delta IL seems to be taken for the maximum in most calculations that is see. Your design tools all take Vin(min) and D(Max) but when i look at multiple SEPIC reference designs they use Vin(max) and D(min)

Here it says to use Vin(min) and D(max)

https://www.ti.com/lit/an/slyt309/slyt309.pdf?ts=1706696842642&ref_url=https%253A%252F%252Fwww.google.be%252F

But here it says to use Vin(max) and D(min)

https://www.ti.com/lit/an/snvaa43/snvaa43.pdf?ts=1706712598906&ref_url=https%253A%252F%252Fwww.google.com%252F

and here it also says to use Vin(max) and D(min)

https://www.ti.com/lit/an/slva516a/slva516a.pdf

Hi Stefan,

Thanks for clarifying the question.
I fully agree that this is confusing, as this will also lead to several different inductance results.

The inductance defines under which load threshold the design will switch from CCM to DCM. It has to be defined by the user in which mode the design should run, and under which percentage of max load the device will switch from CCM to DCM operation.

The calculated inductance will be different depending on where the CCM-DCM threshold is set, and whether this is calculated for the worst case input voltage conditions, or for the average input voltage.

A visualization of this can be seen in the power stage designer tool, when double clicking on the inductor in the schematic to see the current ripple behavior.

Best regards,
Niklas

Hi Niklas, thanks for the clarification. I actually didn't know about that feature of power stage designer, so that is very helpful. Also i will look into the different mode and there thresholds, Thanks for the help!