Quickly Simulate DC-DC Converters with SIMPLIS-Based Tool

February 25, 2020

Brooks Robert Leman  By: Brooks Robert Leman
 Senior Principal Member of the Technical Staff, Applications, Maxim Integrated 


Looking for a way to enhance your DC-DC converter designs? The shortcut to this process is the online EE-Sim® Design and Simulation Tool, which quickly creates and verifies converter designs with pre-configured SIMPLIS simulations. For advanced analysis, download these schematics and use the free, SIMPLIS-based OASIS Simulation Tool to explore and optimize specific modes of operation.

Maxim's new OASIS (Offline Analog Simulator Including SIMPLIS) tool performs common as well as advanced analysis, such as complex time-domain simulations, Bode sub-plots, output impedance plots, multi-variable and Monte Carlo parameter sweeps, and Fourier analysis. All Maxim parts with EE-Sim models have SIMPLIS schematics downloadable into the OASIS simulator. EE-Sim schematics can also be easily downloaded to run in a fully licensed SIMPLIS version.

EE-Sim speeds the design of switching power convertersA SIMPLIS-based simulation tool, such as the EE-Sim OASIS Simulator, can accelerate the design of switching power converters.

SIMPLIS Versus SPICE: Which Is Better for Switching Converter Simulation?

SIMPLIS was initially developed because SPICE did not simulate switching converters effectively. SIMPLIS simulates switching power converters faster and avoids convergence issues commonly found in SPICE. SIMPLIS also has a built-in linearizing algorithm that quickly produces accurate frequency domain response curves (Bode plots) from the same model. SPICE requires much longer simulation times (or you have to take the time to generate a second linearized model yourself).

SIMPLIS Tips and Tricks

There are some basic SIMPLIS skills that can dramatically improve your productivity when you run simulations:

  • Start with a working schematic (several libraries available or download from EE-Sim)
  • Organize probes into waveform groups
  • Manage waveform viewer and schematic window placement
  • Use multiple grid and multiple axis constructs
  • Use multi-variable analysis for parameter sweeps
  • Use advanced Bode plot probe with measurements
  • Paste lab data into waveform viewer window for direct comparison

Getting the Most from Loop Gain and Output Impedance Bode Plot Analysis

Bode plots are simple to generate in SIMPLIS. The only caveat is to first run periodic operating point (POP) analysis to make sure the converter is operating in equilibrium (with no oscillation, cycle skipping, or limit cycles). Being able to simulate Bode plots delivers a number of benefits. You can:

  • Break the loop into smaller blocks and organize the curves for best clarity
  • Easily determine compensation gains and locations for poles and zeros
  • Generate closed-loop and open-loop output impedance simulations

Of course, SPICE simulators do not allow such easy Bode plot simulation and analysis! For a deeper dive on the differences between SIMPLIS and SPICE, read my application note, "Why SIMPLIS Is Better than SPICE for Power Circuits."

Give the OASIS Simulation Tool a try today to see how quickly and accurate you could simulate your circuit designs.