Nonsmooth Current-Constrained Control for a DC-DC Synchronous Buck Converter with Disturbances via Finite-Time-Convergent Extended State Observers

This study investigates the problem of overlarge current protection for a DC-DC synchronous buck converter with the existence of uncertainties and disturbances. Aiming to deal with the hardware damage in the electric circuit of a DC-DC buck that may be caused by overlarge transient current, a new nonsmooth current-constrained control (NCC) algorithm is proposed to replace the traditional ones, which use conservative coefficients to satisfy current constraint, leading to a sacrifice of dynamic performance. Based on the homogeneous system technique, a nonsmooth state feedback controller is improved by adding a penalty term that prompts the adaptive gain of the controller according to the inductor current and current constraint. Then by using two finite-time extended state observers (FTESO), the unmatched disturbances and matched disturbances can be compensated to enhance the robustness of the DC-DC synchronous buck converter. The effect of proposed scheme has been verified by experimental results.