Subharmonic oscillations in converters with current-mode programming under large parameter variations

This paper presents analysis of subharmonic oscillations under large parameter and large signal variations in a converter with current-mode programming. Onset of oscillations is investigated through analysis of period-doubling bifurcation. The analysis is based on a nonlinear discrete-time model derived under the assumption of piecewise linearity of the system but without the usual linear-ripple approximation. Results are confirmed by measurements on an experimental converter and by simulations. It is also shown that a model based on the linear-ripple approximation gives erroneous results both quantitatively and qualitatively.