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WEBENCH-POWER-DESIGNER: Efficiency calculation

Youhei Miyaoka
Expert 4855 points
Part Number: WEBENCH-POWER-DESIGNER
Other Parts Discussed in Thread: LMR43610

Hi team,

My customer use WEBENCH for DCDC converter simulation (LMR43610). 

They got 2 differential efficiency data from WEBENCH.

1. 91.8%, set output 5V first, then change resistance for 3V output

2. 80.9%, set output 3V first, then change resistance for 3V output

The parameters of the circuit are all the same in the end, just by the way they are set up differently. 

Why do we get such a different result? I'm not sure the internal  calculation, but I guess the calculation is based on data corresponding to each output voltage. 

Regards,

Youhei MIYAOKA

  • 0
    TI__Guru* 78775 points

    Hi Youhei,

    Thank you for posting.  Somehow I cannot find the Webench model for LMR43610. I will check with the Webench group.

    By the way, I think the background calculation was not updated.  See the title, it still shows 5V output.

    Thanks,

    Youhao

  • 0
    TI__Expert 3190 points

    Hi Youhei,

    Could you share webench design link for both the cases as i'm unable to replicate the issue?

    Please find an example below :

    Step 1- Create the design by plugging in the desired operating values.
    Step 2-Click on “Share Design” from the top left dropdown option.

    Step 3- Get the public link under ‘Share the design ‘ option.

  • 0 in reply to Shaheen Makandar
    Prodigy 20 points

    Hi

    I share my LM63610 design.

    Could you chack my design?

    1. 91.8%, set output 5V first, then change resistance for 3V output

    https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=EA426ED11F45D5E1

    2.80.9%, set output 3V first, then change resistance for 3V output

    https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=C2C5E7A295DF76E8

  • 0 in reply to ? ??
    TI__Expert 3190 points

    Thank you for sharing the above links,

    We will look into the issue and get back to you tentatively  by next week with the updates

    Shaheen

  • 0 in reply to ? ??
    TI__Expert 3190 points

    Hi User,

    Thanks for sharing the above links,

    Upon checking the above designs, we observe that even though feedback resistors are getting updated in the schematic, as the user input is still 5V vout, WEBENCH modal will consider user inputs for efficiency calculations.

    Here updating feedback resistor will only update few operating params. As you can check in below operating points, based on resistors Vout Actual is getting updated, However operating Vout is still 5V.

    Unfortunately, this is WEBENCH infrastructure limitation. Kindly let us know if you have any other queries