Nonlinear SMPS AC Analysis - Buck Converter - V3p1

This is the same buck converter Mike Donnelly used to demonstrate TDFS Loop Stability Analysis. I have replaced the switch assembly with an equivalent circuit derived by the methodology Vatche Vorperian documented in his May 1990 paper [1]. I drive the switch with a PWM modulator that sources the Fourier transform of the pulse sequence. This is not an averaged model and is, therefore, not constrained to frequencies below half the switching frequency.

The key to coding the models is the use of VHDL-AMS spectral source quantities to formulate Fourier transforms involving products and ratios of waveforms. By this mechanism the models present all the characteristics of the non-linear components in the DC-DC converter.

V3p1 extends V3p0 by introducing a closed form expression of the steady-state modulator output and by deriving a theoretically correct formulation of the switch outputs, the voltage at the common terminal and the current sourced out of the active terminal.

Work remaining includes modeling the transient perturbation of the modulator output due to perturbations in the control voltage (starting with single frequency perturbations) and verification vs, time domain simulations.

[1] See Vorperian's "Simplified Analysis of PWM Converters Using Model of PWM Switch Part 1" in the May 1990 issue (Vol. 26, No. 3) of the IEEE Transactions on Aerospace and Electronic Systems.

Norm's picture




Joined April 18, 2016
Design added Friday, June 7, 2019 | 4:08 pm PDT