Power electronics and discrete time system theory have been closely related to each other from the very beginning. This statement may seem surprising at first, but, if one thinks of switch mode power supplies as variable structure periodic systems, whose state is determined by logic signals, the connection becomes immediately clearer. A proof of this may also be found in the first, fundamental technical papers dealing with the analysis and modeling of pulse width modulated power supplies or peak current mode controlled dc–dc converters: they often provide a mathematical representation of both the switching converters and the related control circuits, resembling or identical to that of sampled data dynamic systems.
