Observer based stabilization techniques for dc dc converters using pole placement and linear quadratic optimal regulator methods

Abstract

The Buck converters are widely used in low power portable newlineelectronic devices, which require control circuits to obtain overload newlineprotection, improved dynamic performance and increased efficiency. The newlinecontrol circuits can be implemented using Observer controller which acts as a newlinesensorless current mode controller to reduce the circuit complexity and newlineprovides a solution for the current imbalances caused mainly due to the newlineintrinsic device parameter variations. A state feedback gain matrix is derived newlineusing Pole Placement method for the Buck converter under continuous time newlinedomain, to achieve the stability of the converter and to ensure the robustness newlineof the controller. The characteristics of the digital controller are low newlinesensitivity to variations, robustness to ageing and environmental changes, newlinenoise immunity and ease of programming. In order to utilize the digital system, a digital state feedback matrix has been derived for the Buck newlineconverter using Pole Placement method. Load estimator for the Buck newlineconverter is designed under both continuous and discrete time domain to newlineestimate the unmeasurable state variables and to obtain zero output voltage newlineerror. Using Separation Principle the state feedback matrices and the load newlineestimators obtained for the Buck converter under both continuous and discrete newlinetime domain are combined together to design an Observer Controller. The Boost converters exhibit the complex dynamic behaviour by newlinetoggling between two different sets of linear and non linear characteristics which require a stronger and an effective feedback control action. The newlinerequired Observer based controller has been designed for the Boost converter newlineunder both continuous and discrete time domain in two steps. In the first step, newlinethe state feedback gain matrix is derived using the pole placement method and newlinein the second step, a load estimator is derived in order to ensure the newlinerobustness of the state feedback control and also to estimate the unmeasurable newlinestate variables.