Near Time Optimal Dynamics in PWM DC-DC Converters: Dual-Loop Geometric Control

Traditional voltage-mode and dual-loop current-mode linear schemes are widely used for controlling the fundamental dc–dc converters due to their simple implementation and fixed-frequency. Pulse-Width-Modulation (PWM) operation. While the dynamic response can be improved by pushing the control bandwidth, lower stability margins may lead to unexpected peak deviations in the inductor current and capacitor voltage, causing failures due to magnetic saturation or excessive voltage overshoot. The concept of dual-loop geometric-based control is introduced in this article by combining geometric state-plane analysis for the outer voltage loop with traditional current-control techniques for the inner loop. The traditional linear voltage compensator is replaced by a geometric alternative that can control the time-domain evolution of the state variables, providing a fast and reliable transient response by following a desired geometrical path to reach the steady-state operating point. In this way, stringent dynamic requirements can be successfully addressed by shaping the state variables’ time evolution by employing a simple geometric equation to define the voltage compensator. Circular trajectories are implemented using simple parametric equations resulting in remarkably well-defined, reliable transient behavior. Experimental results of dual-loop geometric controlled platforms validate the proposed control concept and highlight the strong contribution to the applied field made by this innovative controller.