Modelling and simulation of a non-linear circuit

Abstract

Device Represented of Averaged Fourier Transforms (DRAFT) has been proved to be fruitful in generating SPICE macromodels for series, parallel and series-parallel resonant converters. However, The macromodels are inaccurate when state variables are not sinusoidal and the more accurate version of the models lead to convergence problems in a simulator. In this thesis, a novel macromodel and a new SPICE simulation program are presented. An algorithm of the new macromodel is extended from the averaged Fourier transforms. The algorithm uses actual solutions of state variables. A SPICE macromodel for a resonant converter is generated by the algorithm. The simulated results of the new macromodel are much more accurate than those given by the previous macromodels. A new nonlinear dependent source is proposed to enhance SPICE. The new source can solve equations of the form f (x)=0 with no convergence problems. The implementation of the new source is presented. A macromodel for a resonant converter is taken as an example to demonstrate the application of the new source. In addition, a new SPICE simulation program is written based on SPICE3 using object-oriented programming paradigms. The internal structure of the new SPICE simulation program is outlined. The object-oriented programming paradigms provide a set of features to simplify the internal structure of the new SPICE. When comparing with SPICE3, the new SPICE has many advantages for further development and maintenance.