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TPS40210 Average Model used in a Fly-back application

Patrick50702
Prodigy 240 points
Other Parts Discussed in Thread: TPS40210

Hello:

 

Does anyone know of any documentation on how to use the TPS40210 PSPICE average model in a fly-back application?  I've been able to successfully use in for boost-configurations, but I'm at a loss for how to modify it for a fly-back configuration.

I tried scaling the input voltage, inductor and sense resistor to correspond to the output of the transformer, but it doesn't simulate correctly. 

Thanks

Patrick

  • 0
    TI__Prodigy 430 points

    Patrick,

    Did you put an inductor in parallel with the primary of the transformer representive of the transformer magnetizing inductance?  You also have to size the "burden resistor" Rb in the model to be represenitive of the current sense resistor you are using.  Rburden = 5.8*Rcs.  How/where are you injecting the pertibation into the loop?

    JR

  • 0 in reply to John Rice
    Prodigy 240 points

    John:

    Thanks for the reply. Somehow I didn't see there actually was a reply until today. 

    I put an inductance in series with the IND pin (like in the example file that comes with the model), and made it equal to the transformer secondary inductance.  I then scaled the burden resistor as if it were on the output winding and then multiplied it by 5.8x. I make the power source equal to the output voltage (i.e. 15V). This didn't really seem right but I wasn't sure what else to do. 

    I was injecting the AC into the voltage feedback divider, via the large L and C thing, whereby the AC source isn't included in the loop for the bias calcs (i.e. C is open and L is short), but in AC analysis it's coupled in (i.e. C is short) and the system goes open loop (i.e. L is high Z).

    The simulation didn't have the DC gain I expected, and in addition it didn't seem to work if the power source was over 10V. The simulator would actually crash with certain voltages (not convergence errors, but actually crash).

    Ultimately I gave up on that model wound up using the PWMCM average model I got from a Christophe Basso book, along with his DC transformer model (i.e. XFMR1) .  Those models were pretty easy to use and they had similar results to my calculations so I went with that.

    Thanks for the help

    Patrick