Short-Circuit Protection for Resonant Switched-Capacitor Converter

Short-circuit protection is critical and indispensable for resonant switched-capacitor converter (RSCC) to improve the reliability. Based on comparison of frequency control, duty ratio control and traditional variable frequency variable duty ration control (VFVDC-I), a novel variable frequency variable duty ratio control (VFVDC-II) is proposed for RSCC to suppress the short-circuit current. By analyzing the operation principle and short-circuit mechanism, the RSCC steady-state characteristics as well as the soft switching conditions under four methods are discussed. Then, the resonant characteristics of four methods are compared through state trajectory analysis. At last, the experiments are carried out to verify the correctness of theoretical analysis and feasibility of proposal method. The experimental results demonstrate that the proposed VFVDC-II avoids the voltage oscillation caused by narrow pulse and achieves the shortest transient response and the lowest peak resonant current at short circuit. Moreover, zero voltage switching is realized during turning on, which helps reduce the switching loss.