Sampled-Data Modeling and Analysis of Closed-Loop PWM DC-DC Converters

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1999

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Sampled-data analysis of converters has been a topic of investigationfor the past two decades. However, this powerful tool is not widelyused in control loop design or in closed-loop performance validation.Instead, averaged models are typically used for control loopdesign, while detailed simulations are used for validatingclosed-loop performance. This paper makes several contributions tothe sampled-data modeling and analysis of closed-loop PWM DC-DC converters,with the aim of increasing appreciation and use of the method.

General models are presented in a unified and simple manner, while removingsimplifying approximations present in previous work. These models applyboth for current mode control and voltage mode control.The general models are nonlinear. They are used toobtain {it analytical} linearized models, which are in turn employedto obtain local stability results.

Detailed examplesillustrate the modeling and analysis in the paper,and point to situations in which the sampled-data approachgives results superior to alternate methods.For instance, it is shownthat the sampled-data approach will reliablypredict the (local) stability of aconverter for which averaging or simulation predicts instability.

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