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.

 

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.

 

Can you post your .acs file?

 

Can you post your .acs file?

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.

 

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.

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?

 

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)

 

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.

 

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.

Yes. It is actually very slow in the first design.
I appreciate your help.

 

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