help in analyzing

Discussion in 'General Electronics Chat' started by grad-student, Dec 25, 2014.

  1. grad-student

    Thread Starter New Member

    Nov 19, 2014
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    Attached are two circuits with their output voltage waveforms. These circuits are working under range of temperature (25-200 °C). The 2nd and 4th attached waveforms show the output voltages under the different temperatures.
    I am trying to analyze why am I getting these kind of waveforms. Why the temperature is breaking the the output voltage but not for the second one. I will appreciate any kind of help.
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
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    I could not get it to act like yours, but I didn't have your FET Model. Maybe something wrong with the model?
    PS.
    I think you want the snubber on the other side of the inductor.
    And the power is very high In the FET.
     
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  3. ronv

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    Can you post your .acs file?
     
  4. ronv

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    I think it may have something to do with this statement from the sub file:
    G_G_Rd d2 d1 VALUE
    + {V(d2,d1)/(
    + (1-fpar17)
    + *((dRd*0.5*(1+SQRT(1+4*(MAX(V(d2,d1),0)/fpar15)**(LIMIT(2+fpar16*(V(t1)+Tref-fpar29),0,3)))))
    + *((Tref+LIMIT(V(t1),-200,999))/fpar29)**fpar10)
    + + (fpar17)*((dRd*0.5*(1+SQRT(1+4*(MAX(V(d2,d1),0)/fpar15)**(LIMIT(2+fpar16*(V(t1)+Tref-fpar29),0,3)))))))}

    You could try raising the 200 to 300. I don't know spice well enough to offer more. Maybe someone at yahoo groups or ltwiki could help.
     
  5. grad-student

    Thread Starter New Member

    Nov 19, 2014
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    Ok ronv. Thanks for your help.
    Just a question regarding to what you have suggested. Do I need to add those to sub file or how can I do that?
     
  6. ronv

    AAC Fanatic!

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    I think you can open the .lib file with notepad then change this line. I would try changing -200,999 to -500,9999.

    + *((Tref+LIMIT(V(t1),-200,999))/fpar29)**fpar10)
     
  7. ronv

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    Holy cow does that run slow,
    Anyway to maybe answer your question. One is a boost converter, 2 is a buck converter so the current in #1 is much higher in the FETs.
    It is to high to actually work in anything but the model.
     
  8. grad-student

    Thread Starter New Member

    Nov 19, 2014
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    Yes. It is actually very slow in the first design.
    I appreciate your help.
     
  9. ronv

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    Maybe this would help in changing the sub circuit. It fails when the temp is 300, but runs at 200.
    Runs fast
     
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