A Family of Ladder Multi-resonant Switched-capacitor Converters with Extended Voltage Gain Range and Complete Soft Charging

In this paper, a family of Ladder multi-resonant switched-capacitor converters (MRSCC) is proposed to deal with the issues of a high transient current spike, inherent capacitor charge sharing loss, hard-switched operation, and inability for lossless voltage regulation for traditional Ladder switched-capacitor converters (SCC). By incorporating a multi-resonant core (MRC) and adopting the on-time fixed frequency modulation, a “charge balance” state with overlapped resonant currents is introduced. Consequently, the conversion ratio of the Ladder MRSCC can be regulated continuously, widely, and efficiently, even at light load conditions. In addition, all transistors achieve zero-current-switching (ZCS) turn-on, and all diodes obtain ZCS turn-off. The complete soft-charging operation between capacitors is obtained, eliminating the high transient current spike and charge-sharing loss effectively. In addition, the synchronous Ladder MRSCC with a clamp circuit is proposed to further eliminate the high-frequency ringing and reduce the conduction loss, which makes it potentially applicable to compact applications, including power supplies for portable devices and panel-level photovoltaic systems. A comprehensive analysis of different operation modes, boundary conditions, component stress, topology implementation, and topology comparison is presented to assist converter operation and hardware design. A 55W prototype with the 3X Ladder MRSCC was developed to verify the effectiveness of the proposed topology, modulation strategy, and circuits.