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LM5156EVM-BST: PSPICE for TI Flyback circuit simulation won't run

Joy Gary
Prodigy 10 points
Part Number: LM5156EVM-BST
Other Parts Discussed in Thread: LM5156

Tool/software:

I'm trying to simulate the flyback topology for this chip but can't get the PSPICE simulation to run. The simulation is straight from TI and loaded into PSPICE for TI and the transient simulation for the flyback circuit will not run. The error message changes with each run but the startup circuit will simulate with no trouble. The main 2 errors are that there are shown below:

Are there any settings that need to be changed for this to run? Or is there an updated PSPICE file that has fixed this issue?

  • 0
    TI__Mastermind 22960 points

    Hi Joy,

    Thanks for using the e2e forum.

    I run the flyback testbench in PSpice for TI and got the same error.
    The problematic part here is the optocoupler. This part is not integrated in the TI part library and is therefore considered a third party model.
    Due to PSpice for TI restrictions, this limits the probe count to maximum 3 probes.

    I assume the flyback testbench was created in the full version of PSpice, so this error is PSpice for TI exclusive and was overlooked until now.

    The only two solutions I can suggest right now are:
    - Remove the 'external' optocoupler component U2 and look for a replacement that is part of the available part library
    - Change the simulation settings and only use maximum 3 probe signals

    I am very sorry for this inconvenience.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Prodigy 10 points

    Hi Niklas,

    Thank you for getting back to me. I'm working on these changes, but even with just 1 probe signal it still sometimes won't run. Would it be better to try to run this testbench in the full version of PSpice?

    Thanks,

    Joy

  • 0 in reply to Joy Gary
    TI__Mastermind 22960 points

    Hi Joy,

    I double checked the flyback testbench in PSpice for TI and full version and it seems like there actually is an issue with the testbench itself, that is not related to the simulator.

    The testbench has to be debugged and a new revision needs to be uploaded to the webpage with a new flyback testbench.

    In the meantime I would recommend to avoid this testbench schematic.
    Is there a design project for a LM5156 flyback you are working on?
    Please let us know if we can help with any other sort of design support while we work on a simulation testbench revision.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Prodigy 10 points

    Hi Niklas,

    Thank you for letting me know. How long does it normally take to get a new revision uploaded? 

    Thanks,

    Joy

  • 0 in reply to Joy Gary
    TI__Mastermind 22960 points

    Hi Joy,

    Our applications team is currently under high workload, so modeling progress is rather slow at the moment.
    Depending on how fast a fix can be implemented, I would expect a new version within 1-2 weeks.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Prodigy 10 points

    Hi Niklas,

    Understandable! I'll be on the lookout for the revision and look at other options until then. Thank you for all your help!

    Thanks,

    Joy

  • 0 in reply to Niklas Schwarz
    Prodigy 10 points

    Hi Niklas, 

    Is there any update on the the LM5156 flyback model being corrected?

    Thanks,

    Joy

  • 0 in reply to Joy Gary
    TI__Mastermind 22960 points

    Hi Joy,

    Thanks for checking on this.

    I looked for an alternative optocoupler parts, but I did not find any part from the TI library that fits without importing a third party model.
    The solution would be to use an ideal part, a current controlled current source.
    Of course, this slightly reduces the accuracy of the simulation, as the ideal part is less realistic than the initial optocoupler part, but the overall effect on the simulation behavior is barely visible.

    I have set up the testbench for this and it meets the simulation expectations.
    The model I was simulation with is attached below.

    LM5156-Q1_PSPICE_TRANS.zip

    Please let me know if you have additional questions on the model.
    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Prodigy 10 points

    Hi Niklas,

    Thank you for the update. The attached model seems to be working as expected on my machine. Thank you for your help with this circuit!

    Thanks,

    Joy