Module 1 - Overview of the SIMPLIS Environment / 1.0 SIMPLIS Basics |
SIMPLIS is a time-domain simulator optimized for switching power converters. Most users come to SIMPLIS with some experience using SPICE simulators, which work on an entirely different set of principles. This topic introduces an important difference between SIMPLIS and SPICE. SIMPLIS is exclusively a time-domain simulator, even though it can present its time-domain results very accurately in frequency-domain plots.
In this topic:
This topic addresses the following key concepts:
In this topic, you will learn the following:
How SIMPLIS analyzes circuits exclusively in the time domain. This includes the SIMPLIS AC analysis, which is carried out in the time domain.
In this exercise, you will simulate a synchronous buck converter in the each of the three SIMPLIS analyses, Periodic Operating Point, AC analysis and Transient Analysis.
After running the simulation, the waveform viewer contains a number of graphs. The left-most tab has the gain and phase of the converter control loop taken from the AC Analysis. The other tabs have the results of the transient analysis.
SIMPLIS runs these three analyses in the following order:
Each of these analyses are executed in the time domain, which is exactly what happens on the lab bench. The Periodic Operating Point analysis is discussed in detail in section 1.0.5 POP Analysis, for now think of the POP analysis as a way to accelerate the process of getting to steady state. A key point to remember is that without the Periodic Operating Point, you cannot run an AC analysis on the circuit.
The AC analysis is carried out on the time domain model by first finding the Periodic Operating Point, then injecting a single time-domain sinusoidal perturbation signal into the circuit. The AC results are then calculated from the time domain response to the perturbation signal. Then the injected signal is stepped to the next frequency to be analyzed and the measurement process is repeated until the entire requested frequency range is covered. No averaged model is used. All AC analysis results are derived from the time-domain response of the full nonlinear system.
The time domain POP waveforms and the frequency-domain loop response of the Synchronous Buck Converter are shown below. The frequency response of the circuit is valid at the steady-state condition found during the POP analysis.
Time Domain Waveforms | Frequency Response of Time Domain Model |
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The transient analysis is similar to a transient analysis in other simulators, except it typically runs much faster.
SIMPLIS operates just like your circuit in the laboratory - in the time domain.