A systematic graphing technique for small-signal low-frequency characterization of PWM DC/DC converters

This paper presents a systematic graphing technique for the small-signal low-frequency characterization of pulsewidthmodulated (PWM) DC/DC power converters. The methodology starts with using a discrete-time state-space description to formulate a small-signal sensitivity graph for each circuit topology. Each graph correlates state-variable sensitivities with the topology duration, input source and state vector at the beginning of the topology. The overall converter sensitivities in one switching cycle are obtained by cascading the respective graphs in accordance with the sequence of the topologies. As the proposed method integrates with original algorithms for obtaining the time-domain responses and the steady-state operating point of converters, it is unnecessary to have a priori understanding of the converter operation and is possible to obtain actual circuit waveforms within one switching cycle. The proposed method is exemplified by analyzing a PWM boost converter operating in continuous conduction mode and discontinuous conduction mode under open-loop and closed-loop control, respectively. Theoretical predictions are verified with experimental measurements.