Dual-loop geometric-based control of buck converters

Voltage mode and dual-loop current-mode linear controllers are widely used in buck converters due to their simple implementation and fixed frequency PWM operation. While the dynamic response can be improved by pushing the control bandwidth, lower stability margins may lead to unexpected peak deviations, leading to failures due to magnetic saturations or excessive overshoot. A dual-loop geometric compensator is introduced in this work by combining state-plane analysis with traditional linear controllers. The proposed geometric voltage loop tightly controls the time-domain evolution of the state variables, providing a reliable transient response by following a desired geometrical path to reach the target steady state operating point. Straight line and circular trajectories are implemented resulting in an outstanding, well defined, and reliable transient behaviour. Experimental results of dual-loop geometric-based controlled 50W platform validate the proposed control concept and highlight the strong contribution to the applied field made by this innovative controller.