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In this paper, a new fifth-order boost point of load converter is proposed, and then, a digital controller is designed using a Tchebyshev polynomial approach. The proposed converter has a reduced source ripple current together with a better boosting capability at lower duty ratios. Discrete-time models of the converter are formulated and then used in the identification of the direct digital controller stabilizing region. These discrete-time transfer functions are transformed into a Tchebyshev representation, consisting of converter control-to-output and controller transfer functions, which are then used to ascertain the existence of a stabilizing controller, and if stabilization is possible, then the entire set of gains is constructively determined. Using this method, the controller gain range is obtained as a set of inequalities in two variables for a fixed third variable. By sweeping the third variable over its entire range, the complete stabilizing sets are obtained. Within these ranges, the optimal digital controller parameters are obtained through a constrained optimization problem using a genetic algorithm. An integral time absolute error performance index is used in the optimization. A 30-W, 12- to 28-V, and 100-kHz laboratory prototype closed-loop converter has been developed and then tested, both as a simulation and experimentally, for its voltage regulation capability against source and load perturbations. Both the simulated and experimental results confirm the effectiveness of the proposed design.
Date of Publication: Jan. 2014