What is SIMPLIS?

SIMPLIS is a circuit simulator designed for rapid modelling of switching power systems. An acronym for "SIMulation for Piecewise LInear System", it is supplied with our SIMetrix/SIMPLIS product range.

SIMPLIS is a component level simulator like SPICE but is typically 10 to 50 times faster when simulating switching circuits. It achieves its speed by modelling devices using a series of straight-line segments rather than solving non-linear equations as SPICE does. By modelling devices in this way, SIMPLIS can characterise a complete system as a cyclical sequence of linear circuit topologies. This is an accurate representation of a typical switching power system where the semiconductor devices function as switches. However, a linear system can be solved very much more rapidly than the non-linear systems that SPICE handles. The end result is accurate, but extremely fast simulations, allowing the modelling of complex topologies that would not be viable with SPICE.

SIMPLIS has three analysis modes: Transient, Periodic Operating Point and AC. Transient analysis is similar to the SPICE equivalent but is typically 10-50 times faster. Periodic Operating Point is a unique analysis mode that finds the steady-state operating waveforms of switching systems. AC analysis finds the frequency response of a switching system without needing to use averaged models. This is especially useful for what-if studies on new circuit topologies or control schemes where the small-signal averaged model has not yet been derived.

Because non-linear devices are defined using a sequence of straight line segments, models for such devices are quite different from SPICE models. There are of course many SPICE models available and so in order to retain compatibility with these, SIMetrix/SIMPLIS has the ability to convert models for some types of device into SIMPLIS format. This conversion is performed when the device is placed on the schematic. Devices currently supported are MOSFETs, BJTs and diodes. In the case of MOSFETs and Zener diodes, the conversion is achieved by performing a sequence of simulations using the SIMetrix-SPICE simulator. This method is independent of the method of implementation of the device.