Circle-Based Criteria for Performance Evaluation of Controlled DC–DC Switching Converters

An experimental method is proposed to estimate all design specifications represented by circles in the Nyquist plane (e.g., phase margin, sensitivity, and closed-loop bandwidth) in case of closed-loop dc/dc switching converters. The method is based on the complete root contour (CRC) analysis in the root locus plane. All typical specifications for controller design are experimentally checked in case of a boost converter, using only input/output data. The main innovation of this paper is the automatic and systematic application of the CRC method to controlled dc-dc converters. The classic relay-based structure for an experimental estimation of the critical parameters (autotune variation) is compared with a different technique, called sinusoidal autotune variation, more efficient in the case of nonlow-pass systems