Analysis of ripple effects on frequency response characteristics of boost converter

In this paper we clarify for the boost converter that the ripple effect is not ignorable for the frequency response, and reveal that it causes the unexpected characteristics where either the phase lag or the phase lead appears depending on the shape of the ramp generator. Eventually the phase margin for the stability drastically changes depending on the slope direction (normal or reverse) of the ramp generator even in the same circuit configuration. For these ripple effects we propose the general analysis model and analyze them on the frequency response characteristics by applying the state-space averaging technique. As the result we identify that the ripple effects are caused mainly by the variation of the slope and average of the ripple, and reveal that the boost converter has the asymmetry characteristic for the slope direction of the ramp generator and there is more advantage for the stability in case of the reverse slope direction than in case of the normal slope direction. The proposed analysis method can also treat the compensation circuit in the control circuit and is validated by the experiments and simulations.