A general sampled-data model of PWM DC-DC converters is employed tostudy types of loss of stability of the nominal (periodic)operating condition andtheir connection with local bifurcations.In this work, the nominal solution's periodic natureis accounted for via the sampled-data model.This results in moreaccurate predictions of instability and bifurcation than can be obtained using the averaging approach.The local bifurcations of the nominal operating conditionstudied here are period-doublingbifurcation, saddle-node bifurcation, and Neimark bifurcation.Examples of bifurcations associated with instabilities in PWM DC-DC convertersare given.In particular, input filter instability is shown to be closely related tothe Neimark bifurcation.