Analysis and optimization in design of randomized PWM switching patterns in DC/DC converters

The paper addresses synthesis aspects of randomized modulation. While this switching technique attracted considerable interest of power electronic engineers over the last fifteen years, a large majority of references addresses the analysis aspect of randomization - given a randomization procedure the task is to quantify its effects on the power spectrum. The paper addresses the dual problem in which an objective function for the power spectrum is specified first, and then the task is to select the best randomization scheme from a given family. The synthesis problem is difficult because spectral formulas are nonlinear and quite involved. We concentrate on randomized PWM for DC/DC converters, and introduce analytical and optimization tools that lead to a novel representation of tradeoffs involved. The paper points out fundamental limitations in achieving total spectrum reduction over wide frequency bands, presents numerical results for various duty ratios, and develops a heuristic that well approximates the feasible operating region for all values of the duty ratio.