3.1 SIMPLIS Multi-Step Analysis

How The Multi-Step Analysis Works

You may recall from the topic 3.0.1 What Happens When You Press F9? that the RLoad variable is set in the F11 window:

.var RLoad=2.5

When you ran the Multi-Step Analysis, the RLoad value defined in the F11 window was overwritten by the step value defined in the Define SIMPLIS Multi-Step Analysis dialog. For each step value, the netlist preprocessor:

• Includes the stepped parameter value, in this case RLoad.
• Pre-processes the netlist
• Launches the SIMPLIS simulator on the resulting deck.

In this example, three individual deck files were created, and each new deck file over-writes the previous deck file. This example steps the RLoad parameter over three values in the order - 5 , 2.5, 4.2. In the last deck file, R3 will have a value of 4.2Ω. In the next exercise you will verify the last value of R3 is 4.2Ω.

Exercise #1: Verify R3 Value

1. From the menu bar, select Simulator > Edit Netlist (after preprocess).
   Result: The Deck file opens in the netlist editor.
2. To search for the text 4.2, follow these steps:
   1. Use the shortcut key Ctrl+F to open the search dialog.
   2. Type 4.2
      Result: the deck file scrolls to line 108 where the value of R3 is 4.2 Ω.

      107	R2 35 0 1.5
      108	R3 41 0 4.2
      109	R2 0 28 150

Exercise #2: Enable Multi-Core

This exercise assumes your computer has more than one physical core and that you are using a SIMetrix/SIMPLIS Pro license.

1. Close the waveform viewer.
2. From the schematic menu, select Simulator > Setup Multi-step....
   Result: The Define SIMPLIS Multi-Step Analysis dialog opens:
   
3. Change the Number of cores to 4, the maximum allowed by the Pro license.
   Note: If your machine has either a single core or two cores, the dialog will limit your Number of cores entry. If you have a single core, you can skip this exercise.
4. Click Run.
   Result: The Multi-Step simulation runs on the maximum number of physical cores. Assuming you have a 4 Core machine, all 3 step values are executed simultaneously using 3 SIMPLIS processes, one per processor core. The SIMPLIS Status window has four tabs, one for each SIMPLIS process. The fourth tab is empty as no step value was run on this process:
   

In this exercise, a very small circuit was simulated, yet you probably noticed a significant speed improvement in the time required to execute the Multi-Step Analysis. As circuit size grows, this effect becomes dramatic, and in experiments, speed improvements of approximately 3.5 times when using 4 cores vs. a single core have been found.

Exercise #3: Stepping Multiple Parameters in the Multi-Step Analysis

1. Right click on the gray bar at the top of the schematic:
   Result: The context menu appears with options for this window.
2. Select the Open Containing Folder menu option.
   Result: a Windows Explorer window opens to the schematic directory.
3. Select the 3.1_SelfOscillatingConverter_POP.sxscf file, and drag it into the SIMetrix/SIMPLIS Main Window.
   Result: The file opens in the netlist editor. This file contains the commands which the program interprets when executing a Multi-Step Analysis. The second line has the RLoad parameter information.
4. To step the Vin parameter, you will copy the second line and enter the copied line on the third line of this file, following these steps:
   1. Select all the text on line 2.
   2. Copy to the windows clipboard with the keyboard shortcut Ctrl+C.
   3. Move the cursor to line 3.
   4. Paste the data using the keyboard shortcut Ctrl+V.
      Result: The text file now has three lines. Line 3 is a duplicate of line 2.
      
5. To edit Line #3:
   1. Change RLoad to Vin.
   2. Change the values at the end of the line from 5,2.5,4.2 to 300,310,320.
      Result: The final text file should appear exactly as follows:
      
6. Save the file using the keyboard shortcut Ctrl+S.
7. Close the waveform viewer.
8. In SIMetrix/SIMPLIS, run the Multi-Step Analysis with the menu Simulator > Run Multi-step.
   Result: The Multi-Step Analysis executes and curves for the 9 step value combinations are output to the waveform viewer. As three probes are enabled, 27 curves are output to the waveform viewer.
   

Discussion: Exercise #3

As you can see, multi-step analyses with multiple parameters increases the number of simulation runs geometrically. You can easily fill up the waveform viewer legend with curve information to the point where it is hardly navigable. You can reduce the cluttered graph legend by telling the program to "Group" the curves that each probe outputs into a single curve with a single color. In the next exercise you will edit the Multi-Step Configuration file to group the output curves into a single curve for each probe.

Exercise #4: Group Output Curves

1. In the text editor window, find the groupCurves=False text on the first line:
2. Change the groupCurves=False text to groupCurves=True. The final file will appear exactly as follows:
3. Save the file using the keyboard shortcut Ctrl+S.
   Result: the disk icon turns from red to light blue indicating the file has been saved.
4. Close the waveform viewer.
5. In SIMetrix/SIMPLIS, run the Multi-Step Analysis with the menu Simulator > Run Multi-step.
   Result: The Multi-Step Analysis executes as before, but three curves are output, each curve has nine traces representing the nine stepped values.
   

Discussion: Exercise #4

Each curve listed in the graph legend depicts data generated by the 9 steps of Multi-Step data. The nine steps use the same color and a single entry in the graph legend. A few points should be made:

1. The grouped data presented in the graph above is written to a Multi-Division data group. Analysis of Multi-Division data is extremely challenging, and has to be performed using custom scripts via the SIMetrix/SIMPLIS script language. The built-in measurement system used by the waveform viewer was not designed to handle Multi-Division data.
2. The Design Verification Module, which was specifically designed to analyze and present data from multiple single-step simulations in which more than one parameter is stepped, outputs multiple single step data files, one for each combination of parameter values. The analysis of this data is both trivial, and supported by the built-in measurement system.

Exercise #5: Use DVM to Make Multi-Step Measurements

The Design Verification Module (DVM) makes running multi-step simulations on multiple parameters very easy. In this exercise you will run a DVM testplan which runs the same multi-step simulation as in the previous section.

The DVM schematic 3.2_SelfOscillatingConverter_POP_DVM_basic.sxsch is electrically identical to the schematic used in the earlier example. The differences between this schematic and 3.1_SelfOscillatingConverter_POP.sxsch are:

• The DVM Control Symbol has been added to the schematic. This symbol stores basic information on the circuit, as well as the multi-step parameter information.
• The POP Trigger, Inductor Current and Vout probes have been renamed with a DVM prefix, for example, DVM Inductor Current and DVM Vout. Probes whose names start with DVM will be output to the DVM report.
• Fixed probe measurements have been added to the probes. DVM automatically makes these measurements on each parameter step and outputs the measurements to the DVM report. Again, the probe name must start with DVM.

DVM Control Symbol

The DVM control symbol stores specification information for the schematic. While the DVM control symbol has several forms, the one used in this example is the most basic version. The key specifications used in this example are the multi-step parameters shown in the image below. These parameters are exactly the same as the parameters used in the previous section.