Designing maximum length sequence signal for frequency response measurement of switched mode converters

Abstract

Switched mode power converters are extensively used in powering consumer products. Requirements of short time-to-market and low bill of materials set new challenges to designers. The designers should efficiently create stable and robust designs using low-cost components with high parameter variations. Methods to test statistically the dynamical properties of final design would enable the designers to evaluate control design before production ramp-up. However, currently available testing methods require intervention into internal circuitry or are time consuming and too laborious. This paper describes how Maximum Length Binary Sequences can be used to obtain a high through-put frequency response measurement method to analyze the dynamics of switched mode converters. Some well known computational methods for the frequency response calculation are listed and the design of an appropriate maximum length excitation signal is presented. The proposed signal design procedure takes time-aliasing effect, noise reduction, and the disturbing harmonics generated by pulse width modulation of the converter controller into consideration. The results are verified by experimental measurements from a high-frequency switched mode converter.