Tutorial #3:
3-1: EXECUTION OF A PARAMETRIC SWEEP OPTION
3-2: EXAMPLE of MAXIMUM POWER TRANSFER TEST
GETTING RESTARTED:
Step #1: Invoke pSPICE by double-click of the left mouse button (DCL) on the pSPICE ‘design manager’ icon as was done for startup under tutorial #1. The double-click left (DCL)on the schematics icon for which the blank pSpice schematics screen will appear.
Step #2: Click (SCL) on the File > Open button sequence and restart the schematic ‘pwr_xfer’ that you created once upon a time.
Of course if you have gone directly from tutorial #1 thru tutorial #2 to this tutorial (tutorial #3), you are already there, and steps #1 and #2 are unnecessary.
You should end up with the following screen:
Now we will do something different. We will change the value of R2 (shown as 9k) to one that is symbolic. To do so, we double-click (DCL) on the value ‘9k’, which pulls up the screen
For this screen we will change the ‘9k’ to ‘{Rx}’. The resulting screen will appear as:
The curly brackets tell us that the value is symbolic, and we will need to tell pSPICE what the value for Rx will be. This command is accomplished by call-up of a special part, the ‘PARAM’ part. On the schematics window go to the Parts icon and pull up
Parts > PARAM (as shown)
Do a place and close of one of these parts, for which you should see a screen
The PARAM part can be placed anywhere, since it is a specification table. Double-click on the PARAMETERS name and its specifications screen will appear, as follows:
We will give NAME1 the ‘value’ Rx.
We also need to specify a ‘default’ VALUE1 for this part, which we might as well let be = 9k
You will find, in each case, that the ‘Save Attr’ button must be clicked in order to confirm the name and value that you have designated/assigned.
And once you close out this screen you will see:
And now the part R2 has the value 9k, except specified by a ‘parametric’ option.
We will make use of the fact that the value of resistance R2 is symbolic by invoking a different option under the Analysis > Setup menu. Doing so what we should see is the usual screen
and we will invoke the ‘DC Sweep’ option for which you should see:
-except this time we will invoke the ‘Global Parameter’ option under the Swept Var. Type. And in this case we will make the following changes:
Name: Rx
Start Value: 0.1k
Stop Value: 10k
Increment: .01k
If we go ahead with an OK and close sequence we will have now told pSPICE that we will sweep the value of Rx (which is the value of resistance R2) from 0.1k to 20k. We would start at Rx = 0, except that pSPICE is not able to undertake a nodal analysis when R = 0 (since its conductance is infinity) and will give an error. If we invoke pSPICE with R = 0, pSPICE will give us an error message and refuse to proceed further. This inaction is typical of any fatal error.
So if we now invoke a simulation, (hotkey = F-11) pSPICE will undertake a nodal analysis computational process and we will then see the usual Probe screen. In this case we desire to determine more than just a simple select of currents and voltages; we wish to ascertain the power dissipated in resistance R2.
This requirement can be accomplished by calling up the Trace >Add screen and making the specification for power as shown by the ‘Trace Expression’ window. Notice that we make use of ‘*’ for multiply and ‘/’ for divide, to define the power dissipated in the resistance R2 as indicated.
Once we ‘OK’ this screen the trace of this expression will appear as follows:
And we see that the maximum power results when Rx = 1k, (which should be no great surprise since this exercise is a test of the max power transfer theorem). Maximum power is transferred to the ‘load’ R2 when R2 is of the same value as R1 (for R1 =’source’ resistance).
We can confirm the value by use of the cursor:
Since the cursor cannot be resolved to any better accuracy, it shows load resistance for maximum power transfer as only approximately 1.0k. But the theorem is still confirmed OK, as expected.
This concludes tutorial #3.
Almost: You can print out this screen result by use of the File> Print button sequence, and pSPICE will then alert you of the available printers.