LPF-Based Critically Damped Output-Feedback Systems for DC/DC Power Converters via Second-Order Active Damping Design Approach

The proposed observer-based controller stabilizes the output voltage of dc/dc converters, without without any high-model dependence, including a low-pass filter (LPF) for the output voltage measurement as a part of the main feedback system. Considering additional LPF dynamics makes the closed-loop design process complicated and increases number of tuning factors. To address this challenge, the combination of second-order active damping terms and nonlinearly designed feedback gains for both the controller and observer invokes the second-order pole-zero cancellation (PZC) to lower the increased feedback system order owing to the consideration of LPF dynamics. The model-free observer robustly finds the correct output voltage derivative information based on the second-order PZC technique to remove the necessity of incorporating the current feedback. On the basis of the observer, the output-feedback technique forming proportional-integral-derivative controller assigns the critically damped output voltage response to the controlled system without the singularity problem, including the second-order active damping terms and the disturbance observer as the auxiliary system. A 3-kW prototype dc/dc converter experimentally validated the practical benefits of the closed-loop design.