Effects of parasitic capacitances on the small-signal frequency response of a regulated dc-to-dc converter designed for discontinuous-mmf operation

The presence of parasitic capacitances in the power stage of a dc-to-dc converter designed for discontinuous-mmf operation results in a ringing of the mmf during the time that the mmf is intended to be equal to zero. With a constant-frequency controller, this ringing is shown to result in a widely fluctuating small-signal loop gain for relatively small changes in operating conditions. This fluctuating loop gain, which cannot be predicted by present-day smal1-signal-modeling techniques, may result in instability if not allowed for in the design process.