Modeling and analysis of a self-oscillating peak-current controlled flyback converter

The modeling of a self-oscillating peak-current controlled flyback power converter is presented. Transfer functions describing the output dynamics of a flyback converter are obtained by applying partial derivatives to the nonlinear state equations that are derived using proposed modeling method. The loop gain of a practical 3-W flyback converter was measured and compared to predictions. The time delay in boundary mode showed not significant influence on the converter dynamics in the load range of interest. The nonminimum phase characteristics of a flyback converter will limit the achievable controller bandwidth also in a variable-frequency operation similar to the fixed-frequency operation in CICM and DICM.