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LM5022-Q1: Convergence issue with Orcad-Capture

GERARDO SAGGESE
Prodigy 150 points
Part Number: LM5022-Q1

Hi Support Team,

I designed a DC/DC Boost converter with the following specifications:

- Vin 30-40 V

-Vout 325 V

- Iout 600 mA

Q1. The simulation stops and shows a convergence problem in transient analysis. How can I solve this problem?

Q2. Is it possible use a voltage drop higher than 7 V on VCC pin to get a higher Vgs. How can I do that?

I hope you can help me to fix these issues. 

Thank you in advance.

Gerardo Saggese

  • 0
    TI__Mastermind 21720 points
    Hi Gerardo,

    Thanks for reaching out with your questions.

    Regarding the convergence issue, I suggest removing L3. 1uH of parasitic inductance is a very large number. On the same note I recommend removing R4 and D3 to help simplify the circuit.

    The VCC pin can be externally supplied with a voltage larger then 7V to increase the MOSFET drive voltage. Please ensure that the VCC voltage doesn't exceed 16V as this is the absolute maximum voltage rating.

    Please let me know if you have any questions.

    Thanks,

    Garrett
  • 0 in reply to Garrett Roecker
    Prodigy 150 points
    Hi Garret,
    Thank you for your reply. I followed your tips but I have not solved the convergence problem yet.
    Do you have other suggestions?

    Thanks,
    Gerardo
  • 0 in reply to GERARDO SAGGESE
    TI__Mastermind 21720 points
    Hello Gerardo,

    Is the simulation throwing any errors or warnings at you? Anything you might have can help.

    Did you check the loop stability before you started the simulations?

    -Garrett
  • 0 in reply to Garrett Roecker
    Prodigy 150 points
    Hello Garrett,
    Yes, I did check the loop stability.
    The simulation shows that 5 devices fail to converge:
    "
    ERROR(ORPSIM-15660): These devices failed to converge
    X_U1.XVCOA1.XU5.D1
    X_X2.G_miller
    X_U1.QSS1X
    X_U1.QSS2X
    X_U1.QSS1
    "
    a part of log file:
    "
    These devices failed to converge:
    X_U1.XVCOA1.XU5.D1 X_X2.G_miller X_X2.G_millera X_U1.QSS1X X_U1.QSS2X
    X_U1.QSS1 X_U1.QSS2

    ERROR(ORPSIM-15138): Convergence problem in transient analysis at Time = 4.768E-15.
    Time step = 4.768E-15, minimum allowable step size = 20.00E-15

    These voltages failed to converge:

    V(N16783185) = 87.97mV \ 80.55mV
    V(N16786506) = 87.97mV \ 80.55mV
    V(N16783502) = 87.97mV \ 80.55mV
    V(X_U1.53) = -388.32mV \ -414.17mV
    V(X_U1.XVCOA1.3) = 115.30mV \ 2.030uV

    These supply currents failed to converge:

    I(X_X2.E1xxx) = -10.75mA \ 295.40mA
    I(X_X2.Edev) = 50.85uA \ 13.40mA
    I(X_X2.Edevc) = -711.31nA \ 19.55uA
    I(X_X2.E_Eds) = -254.70uA \ -291.63uA
    I(X_X2.Edeva) = 249.51uA \ -18.59mA
    I(X_U1.XVCOA1.XU2.E1) = -3.022MA \ -53.20A
    I(X_X2.VLs) = -10.75mA \ 295.40mA
    I(X_X2.V1xx) = 10.75mA \ -295.40mA
    I(X_X2.V_miller) = -50.85uA \ -13.40mA
    I(X_X2.V_millerc) = 711.31nA \ -19.55uA
    I(X_X2.V_millera) = -249.51uA \ 18.59mA
    "
    These are the errors in the simulation.
    If you need any else informations, let me know.

    Thank for your time.
    -Gerardo
  • 0 in reply to GERARDO SAGGESE
    TI__Intellectual 2680 points

    Hi Gerardo,


    Please share your PSpice project (with OPJ,DSN,OLBand LIB files). You can zip the folder and upload it here.

    We will simulate it at our end and get back to you.

  • 0 in reply to Saket
    Prodigy 150 points

    BOOST.rarHi Saket,

    You may find enclosed the files you asked. There are some changes I made because I need an external power supply to have a larger Mosfet drive voltage ( at least 10V-15V).

    I hope I share all the files you need.

    Thank you in advance for your help and regards,

    Gerardo Saggese

  • 0 in reply to GERARDO SAGGESE
    TI__Intellectual 2680 points

    Hi Gerardo,

    I got the files and was able to replicate the same issue at my end as well. I am looking into it and get back to you.

  • 0 in reply to Saket
    Prodigy 150 points
    I am loking forward.
    Thank you & Regards,
    GERARDO SAGGESE
  • 0 in reply to GERARDO SAGGESE
    TI__Intellectual 2680 points

    Hi Gerardo,

    There is no issue with schematic and I am able to run simulation with simulation settings as per published model (at website).

    Below are the images for you reference. Please update your simulation settings and let me know if you still face convergence issue.

    Also, note that SKIPBP is ticked in simulation settings to Skip initial bias point calculation.

    Simulation Results:

    Steady State

  • 0 in reply to Saket
    Prodigy 150 points

    Hi SAKET,

    Thank you.

    It works. I mean, I ve just solved the convergence problem but now, I have another problem on the Output (should be 325V). So, I am gonna check and I hope to figure out what is wrong. 

    Anyway, Thank for your time.

    Regards,

    GERARDO SAGGESE