Theoretical and Experimental Investigation of Averaged Modeling of Non-ideal PWM DC-DC Converters Operating in DCM

State-space averaged modeling of PWM converters in discontinuous conduction mode (DCM) has received significant attention in the literature and several models have been developed. These models are given either in analytical form or as equivalent circuits, and can be classified into three categories: 1) reduced-order models, 2) full-order models, 3) corrected full-order models. In this paper various aspects of the representative models of each category have been investigated. Several previously established models are compared based on their predictions of parasitic effects as well as the small-signal frequency-domain characteristics. In order to further analyze their relative validity, these models are compared to a hardware prototype. A simple methodology of small signal-injection and subsequent frequency-response measurement is proposed and implemented to extract the small-signal control-to-output transfer function from a hardware prototype. Experimental effectiveness of this method has been demonstrated up to about one-third of the switching frequency. Theoretical and experimental results reveal that at higher frequencies corrected full-order models have shown improved accuracy; in particular they are capable of predicting high-frequency pole in DCM operation.