An Approach to Exact Modeling of the PWM Switch

Large number of small-signal models of de-to-de power converters exists already. These models usually use two techniques. The first is the averaging technique, such as: volt-second and current-second balance, state space averaging, and the averaged modeling approach. The other technique focuses on the exact modeling approach, such as: the application of time varying systems theory to linearize networks. One of the methodologies to apply the above techniques, is to view the three-terminal systems as a two-port network. The aim of the work presented in this thesis is to develop a new approach, by the application of the two-port network methodology to the results of the exact system modeling using the theory of time varying systems, to develop an exact model of the nonlinear part of the switching converters, which is simply the pulse width modulation (PWM) switch. So, the aim of this new approach is focused towards obtaining an accurate and simple model of the PWM switch, over the previous inaccurate averaged models. This is achieved by the evaluation of the parameters of the two-port network, which is used to describe the PWM converter systems, through the use of the exact input-to-output and control-to-output transfer functions. The model of the PWM switch is then developed, and examined on the buck and the boost converters. A partial realization of the aim of this work has been achieved; the dynamic behaviors of the new PWM switch model is much accurate than the corresponding dynamic behaviors of the averaged models, yet the dynamic behaviors obtained for the PWM converters through the application of the new PWM switch model is less accurate than the corresponding exact dynamic behaviors of the PWM converters