title: Tutorial 104: Running Simulations¶

Tutorial 104: Running Simulations¶

Overview¶

Master the simulation settings in GeckoCIRCUITS. Learn about solver options, time step configuration, convergence issues, and how to optimize simulations for accuracy and speed.

Level: Beginner/Intermediate (⅔)

Duration: 25-30 minutes

Series: Getting Started

Learning Objectives¶

By the end of this tutorial, you will: - [ ] Configure simulation time and time step - [ ] Understand different solver algorithms - [ ] Diagnose and fix convergence problems - [ ] Optimize simulations for speed vs. accuracy - [ ] Use the oscilloscope (SCOPE) effectively - [ ] Export simulation data

Prerequisites¶

• Complete Tutorial 101-103
• Basic understanding of differential equations (helpful but not required)

Simulation Settings Overview¶

Access settings via Simulation > Settings or press F9.

Main Parameters¶

Time Step Configuration¶

Automatic vs. Fixed Time Step¶

Automatic (Recommended for beginners): - GeckoCIRCUITS adjusts dt based on circuit dynamics - Smaller dt during fast transients, larger during steady-state - Good balance of speed and accuracy

Fixed Time Step: - You specify exact dt value - Useful for: deterministic timing, FFT analysis, comparison studies - Risk: too large → inaccuracy, too small → slow simulation

Choosing Time Step¶

Rule of thumb:

dt < Ts / 100    (switching period / 100)

Example: fs = 100 kHz → Ts = 10 μs → dt < 100 ns

Time Step Too Large¶

Symptoms: - Waveforms look choppy/aliased - Incorrect average values - Missing fast transients - Simulation completes but results are wrong

Time Step Too Small¶

Symptoms: - Simulation runs very slowly - Excessive data storage - No improvement in accuracy (diminishing returns)

Solver Selection¶

GeckoCIRCUITS offers multiple numerical solvers:

Trapezoidal (TRZ) - Default¶

x(t+dt) = x(t) + dt/2 × [f(t) + f(t+dt)]

• Accuracy: Second-order, no numerical damping
• Stability: A-stable for linear circuits
• Best for: Most power electronics circuits
• Issue: May show ringing on discontinuities

Backward Euler (BE)¶

x(t+dt) = x(t) + dt × f(t+dt)

• Accuracy: First-order, introduces numerical damping
• Stability: Very stable, L-stable
• Best for: Stiff circuits, initial debugging
• Issue: Over-damps high-frequency oscillations

Gear-Shichman (GS)¶

• Accuracy: Higher-order, multi-step method
• Best for: Circuits with multiple time scales
• Issue: More complex, may have startup transients

Solver Comparison¶

Simulation Workflow¶

Step 1: Initial Setup¶

1. Set simulation time: 5-10 fundamental periods
2. Start with automatic time step
3. Use TRZ solver
4. Run simulation

Step 2: Check Results¶

1. View waveforms in SCOPE
2. Verify expected behavior
3. Look for: oscillations, convergence issues, unrealistic values

Step 3: Refine Settings¶

If results look wrong: - Try smaller time step - Switch to BE solver temporarily - Check circuit for errors

If simulation is too slow: - Increase time step (if accuracy allows) - Reduce simulation time - Simplify circuit model

Oscilloscope (SCOPE) Usage¶

Adding Signals¶

1. Connect circuit nodes to SCOPE inputs
2. Use current probes for current measurement
3. Multiple channels available (different colors)

Measurement Tools¶

SCOPE Settings¶

1. Double-click SCOPE component
2. Configure:
3. Channels: Enable/disable, colors
4. Scale: Manual or auto
5. Trigger: Level, edge, mode
6. Time base: Samples per division

Data Export¶

Exporting Waveforms¶

1. File > Export Data after simulation
2. Choose format:
3. CSV: For Excel, MATLAB, Python
4. Text: Tab-separated values
5. Select signals to export

Export Format¶

Time,Channel1,Channel2,Channel3
0.0000,0.00,10.00,0.00
0.0001,5.23,10.00,0.52
0.0002,9.87,10.00,0.99
...

Using Exported Data¶

MATLAB:

data = readmatrix('simulation_data.csv');
t = data(:,1);
v = data(:,2);
plot(t, v);

Python:

import pandas as pd
import matplotlib.pyplot as plt

data = pd.read_csv('simulation_data.csv')
plt.plot(data['Time'], data['Channel1'])
plt.show()

Troubleshooting¶

Simulation Won't Start¶

Simulation Diverges¶

Slow Simulation¶

Oscillations in Results¶

Advanced Settings¶

Initial Conditions¶

For faster convergence: 1. Set initial capacitor voltages 2. Set initial inductor currents 3. Avoids long startup transients

Steady-State Detection¶

GeckoCIRCUITS can detect when circuit reaches steady state: 1. Enable in Simulation > Settings 2. Simulation stops when periodic steady state achieved 3. Useful for efficiency calculations

Parametric Sweeps¶

Run multiple simulations with varying parameters: 1. Use GeckoSCRIPT or MATLAB integration 2. Sweep: duty cycle, load, frequency 3. Automatically collect results

Checkpoint¶

At this point, you should be able to: - [ ] Configure simulation time and time step appropriately - [ ] Choose the right solver for your circuit - [ ] Diagnose and fix common simulation issues - [ ] Use SCOPE measurement tools effectively - [ ] Export data for external analysis

Exercises¶

Exercise 1: Time Step Sensitivity¶

1. Open a buck converter circuit
2. Run with dt = 1 μs, record output voltage
3. Run with dt = 100 ns, record output voltage
4. Run with dt = 10 ns, record output voltage
5. Compare: At what dt does accuracy stabilize?

Exercise 2: Solver Comparison¶

1. Create an LC circuit (L=1mH, C=1μF)
2. Run with TRZ solver, observe ringing
3. Run with BE solver, observe damping
4. Question: Which is more physically accurate?

Exercise 3: Data Export¶

1. Run any simulation
2. Export data as CSV
3. Plot in Excel/MATLAB/Python
4. Calculate: average, RMS, ripple

Exercise 4: Convergence Debugging¶

1. Create a circuit that diverges (e.g., very large L, very small C)
2. Try to fix it using:
3. Smaller time step
4. BE solver
5. Adding damping resistor
6. Document: What worked?

Summary¶

In this tutorial, you learned: 1. How simulation time and time step affect results 2. Different solver algorithms and when to use them 3. Troubleshooting common simulation problems 4. Using SCOPE for measurements 5. Exporting data for external analysis

Quick Reference¶

Next Steps¶

You've completed the Getting Started series! Continue with: - DC-DC Converters: 2xx Series - Rectifiers: 3xx Series - Examples: Basic Topologies

Tutorial Version: 1.0 Last updated: 2026-02 Compatible with GeckoCIRCUITS v1.0+