A modeling method for the TL buck DC-DC converter with input and output sharing the ground

For the improved three-level (TL) buck direct current-direct current (DC-DC) switching converter which is a high-order, discrete, non-linear, and time-variant dynamic system, the work multi-modalities and principle are analyzed, and the state space equation model is established by introducing the switch cycle averaging operator under low-frequency, small ripple, and small-signal assumption. The transfer function from control to output that is needed by closed-loop feedback system is deduced by introducing small-signal perturbation. The closed-loop control system is designed based on the transfer function model by applying feedback control theory. The experiment results show that closed-loop system has good dynamic and static performance, and further indicates that the mathematic models are reasonable.