Model for non-linear load in Pspice?

Hi Shalini,

        Modeling non-linear resistors in SPICE can be a bit tricky, let start by splitting the problem in two steps:

1. Create a voltage resistor

2. Make the resistance of step one vary in a non-linear fashion with respect to the control voltage e.g. R(Vctrl) = a + b*Vctrl^2 + c*Vctrl^3 + ....

Okay, step one.  A voltage controlled resistor can be modeled in SPICE using a voltage controlled current source (G-element) controlled by its own voltage, this  is known as the source absorption theorem.

Below is the netlist for a 1k resistor

.SUBCKT  Vctrl_resistor  POS  NEG 

+ PARAMS: Rx = 1k

GmyResistor     POS NEG  VALUE = { V(POS,NEG)/(Rx) }

.ENDS

Step 2. Looking at the denominator  in the equation above (Rx*V(POS,NEG)) we observe that the resistance will vary linearly with the voltage across the resistor V(POS,NEG) however, this can be easily modified by fitting the resistor data using a Taylor polynomial, e.g. Rx*V(VCTRL) + a*PWR(V(POS,NEG),2) + ..... nthCoefficient*POW(V(POS,NEG),nth)

In this example I assumed your resistor exhibits non-linear behavior with respect to input voltage. Let me know if this answers your question, if you can provide a datasheet of the CFL that you are trying to model, perhaps we can help with step two.

Regards,

Macos.

Thank you so much for the response! I will try to work it and let you know in case I face any issue.