ABSTRACT
In the preceding chapters, analyses of switching converter topologies have so far been performed under the steady state condition. Predicting its dynamic characteristics has not been easy, due to the complexity of the operation of the switching converter. The dynamic characteristic of the switching converter can be used to predict (a) the margin of stability of the switching converter, (b) the input supply ripple rejection and the transient response due to input supply perturbation, (c) the output impedance and the transient response due to load perturbation, and (d) the compatibility with the input EMI filter [13]. Thus, dynamic or small-signal analysis of the switching converter enables designers to predict the dynamic performance of the switching converter to reduce prototyping cost and design cycle time. Generally, dynamic analysis can be either numerical or analytical. Numerical methods can be useful for computer simulations, but they cannot reveal basic relationships among circuit elements in the switching converter. Switching converters are nonlinear time-variant circuits. Nevertheless, it is possible to derive a continuous time-invariant linear model to represent a switching converter. Different linear models have been developed to describe the small-signal behavior of the switching converters ([57], [58], [59], [60], [61], [62], [63]). Continuous-time models are easier to handle, but not very accurate. Since a switching converter is a sampled system, a discrete model gives a higher level of accuracy, and also models some aspects of the converter (like subharmonic oscillations) that are not covered by a continuous model. A discrete-time modeling technique, such as sampled and nonlinear data modeling ([64], [47], [65]) must be used for this last case, or when more accurate results are needed.
