Introduction of Simplis

Ming Sun

Ming Sun / November 18, 2022

6 min read––– views


In Ref. [1], you can find more information about Simplis.

SIMPLIS (SIMulation of Piecewise LInear Systems) is a circuit simulator specifically designed to handle the simulation challenges of switching power systems. Like SPICE, SIMPLIS works at the component level but typically can perform a transient analysis of a switching circuit 10 to 50 times faster. For switching power systems, the piecewise linear (PWL) modeling and simulation techniques employed by SIMPLIS result in qualitatively superior convergence behavior compared to SPICE.

Simplis is widely used in the industry for switching mode power supply design. If you ever used Cadence/Spectre, you are going to know that in Spectre, we can use AC analysis and STB analysis to simulation the loop charactistics in terms of magnitude, phase, phase margin, gain margin, etc.

However, for a switched mode power supply, it is not the case. The switching mode regulators have switching event. In order to simulate its stability and design the corresponding controller and compensator, we can either:

  • Perturbe and linearize the power stage. Basically, we remove all the switching event from the circuits so that we can run AC and STB analysis.
  • Or, we run PSS, PSTB and PAC. If you ever run those analysis before, you can quite easily to tell that to make the PSS and PSTB converge is super painful. Some of the components such as Verilog-A with delays does not really support the PSS and PSTB analysis. And even PSS converges, sometimes PSTB just gives you some unpredicted result. What we have to do is that we have to use tstab and PAC to debug and find where the break happens.

Besides that, the simulation speed for PSS and PSTB is not very fast, ~30mins.

In Simplis, the POP simulation can be used to analyze the stability and design the compensation network. The simulation speed is typically very fast. For a typical Buck converter, it may just take less than 10 seconds to finish the simulation and get the phase margin/gain margin results.

Simplis is widely used in the industry for DC/DC converter design, such as TI, Maxim, ADI, Qualcomm, etc. Typically, system engineers or designers use Simplis to design the controller, verify the concept and pour the design from Simplis into Cadence Spectre into macro model. After that, designers can replace the ideal macro model components with transistor level schematic step by step.

This post is the very first blog posts in the Simplis - 101 series. Please refer to Ref. [2] for more detailed information.

References and materials

[1] What is SIMPLIS?

[2] SIMPLIS Tutorial

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