Robust current mode control of switching DC-DC converters

Abstract

Summary form only given. The authors propose an approach that results in a controller and filter design that is optimal and robust and in which the interacting effects (coupling) of the filter and the controller are used as extra degrees of freedom in the selection of the controller gains and filter components. In particular, the controller and filter design methodology is based on a linear quadratic formulation that accounts for the different constraints on design specifications. The resulting controller structure has the following components: (1) feedforward gains that provide anticipative response control to all nonexciting and limited-time-exciting commands and disturbances in the input voltage and that also alter the zeros of the resulting closed-loop system; (2) a servocompensator positioned in the forward loop path of the converter model to ensure asymptotic tracking of the commanded voltage and rejection of all disturbances; (3) state feedback and a filter to enforce the desired high gain at low frequency and low gain at high frequency and approximately -20-dB/s/dec slope at the crossover frequency in order to attain satisfactory phase margin. A proportional integral (PI) observer, instead of using a hardware current sensor, is used to estimate the inductor current. The controller and filter of a 50-W, DC-DC buck converter that supplies a load with a constant output voltage of 5 V have been designed and implemented in hardware.<>