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FLYBACK UCC3809 OrCAD/PSpice convergence problem

Lukasz Walus
Prodigy 30 points

hello

i'm tring to simulate flyback with UCCx809-2 controler and i have
some problems with simulation. i have convergence problems. i'm using OrCad 16.3:

These voltages failed to converge:

V(COLLECTOR) = 5.000V \ 4.147V
V(N50537) = 5.069V \ 4.623V
V(X_U1.clk) = 4.995V \ 4.549V
V(X_U1.13) = 4.545V \ 4.098V
V(X_U1.7) = 5.000V \ 4.554V
V(X_U1.ref5vint) = 5.000V \ 4.554V
V(X_U1.20) = 5.000V \ 4.147V
V(X_U1.24) = -10.00V \ -9.107V
V(X_U1.PWMq) = 5.000V \ 4.554V
V(X_U1.21) = 5.000V \ 4.147V
V(X_U1.22) = -10.00V \ -9.107V
V(X_U2.5) = 5.000V \ 4.147V
V(X_U2.6) = 192.37mV \ 191.82mV
V(NC) = 192.37mV \ 191.82mV
V(X_U2.7) = 1.039V \ 867.82mV
V(X_U3.8) = 1.643V \ 1.647V
V(X_U1.X1.Qint) = -343.51mV \ -320.94mV
V(X_U1.X1.Qqq) = -312.84mV \ -292.29mV
V(X_U1.X1.Qqqd1) = 2.498V \ 2.275V
V(X_U1.X2.Qint) = 4.897V \ 4.875V
V(X_U1.X2.Qqq) = 4.460V \ 4.440V
V(X_U1.X2.Qqqd1) = 5.000V \ 4.554V
V(X_U1.X_U1234.INP2) = 6.375V \ 5.806V
V(X_U1.X_U1234.1) = 5.000V \ 4.554V
V(X_U1.UVLO_INT) = 5.000V \ 4.554V
V(X_U1.X2.X3.YINT) = 5.000V \ 4.554V

These supply currents failed to converge:

I(X_U1.EBRegate) = -33.34uA \ -27.65uA
I(X_U1.X1.X3.E_ABMGATE) = 2.498A \ 2.275A
I(V_V1) = -10.00GA \ -10.00GA
I(X_U1.VMRef) = -33.34uA \ -27.65uA
I(X_U3.V4) = -1.014uA \ -924.24nA
I(X_U1.X2.V1) = 5.000A \ 4.554A

Almost all errors refers to UCCx809-2 controler (X_U1).
When i set autoconvergence i have less errors:


These voltages failed to converge:

V(X_U1.13) = 4.500V \ -500.00mV
V(X_U1.7) = 5.000V \ 0V
V(X_U1.ref5vint) = 5.000V \ 0V
V(X_U1.X1.Qbr) = 0V \ 5.000V
V(X_U1.X2.Qbr) = 0V \ 5.000V
V(X_U1.X_U1234.1) = 93.13nV \ 10.43mV
V(X_U1.UVLO_INT) = 5.000V \ 559.68KV
V(X_U1.X_U2345.YINT) = 0V \ 5.000V

These supply currents failed to converge:

I(X_U1.EBref) = -485.29uA \ -7.000uA
I(X_U1.X1.EQb) = 0A \ -5.000A
I(X_U1.X2.EQb) = 0A \ -5.000A
I(X_U1.X_U1234.EOUT) = -5.000A \ -559.68KA
I(X_U1.X_U2345.E_ABMGATE) = 0A \ -5.000A
I(V_V1) = -10.00GA \ -10.00GA
I(X_U1.VSS) = 478.29uA \ -693.32fA

These devices failed to converge:
X_U1.DSS X_U1.DVdd X_U1.X1.GQ X_U1.MBF X_U1.MTF

ERROR -- Convergence problem in transient analysis at Time = 11.64E-18
Time step = 11.64E-18, minimum allowable step size = 40.00E-18

These voltages failed to converge:

V(OUT) = 123.51V \ 144.07V
V(X_U1.24) = 113.51V \ 134.07V

These supply currents failed to converge:

I(X_U1.EBref) = -7.000uA \ -485.29uA
I(X_U1.EBout) = -1.135A \ -1.341A
I(V_V1) = -10.00GA \ -10.00GA
I(X_U1.VSS) = 4.510pA \ 478.29uA

These devices failed to converge:
X_U1.DVdd X_U1.MBF X_U1.MTF

Now errors refers only to controler.

When i simulate independently the power section and feedback loop with the same
values i don't have any problems

What should i do to run this simulation?

  • 0
    TI__Expert 5900 points

    Hi, 

    The convergence problem can be caused by a lot of reasons.

    I can only suggest you to try modifiy the simulation setting such as maximum steps.

    Or modify the initial value of components.

     

    Or maybe you can ask the question in simulation and models forum

    http://e2e.ti.com/support/development_tools/webench_design_center/f/234.aspx

     

    Regards