Analysis and Design of the Ladder Resonant Switched-Capacitor Converters for Regulated Output Voltage Applications

The traditional Ladder switched-capacitor converters have the issues of hard-switching operation and poor line regulation capability. By adding a resonant inductor and substituting a bulky capacitor bank with a small resonant capacitor, its resonant configuration can be obtained and the aforementioned issues could be solved. In addition, by operating the Ladder resonant switched-capacitor converters (RSCs) above the resonance, the optimized operation region is found and some transformational changes can be obtained: the transistors can be operated with zero voltage switching turn-on and diodes are zero current switching turned on/off; the line regulation range is increased significantly for regulated output voltage applications; the instability issue of transition between discontinuous current mode and continuous current mode can be avoided with closed loop; and the voltage/current stress of the resonant tank is reduced. Extensive analysis above and below the resonance is presented to reveal the converter operation modes, voltage-gain curves, output characteristics, and voltage/current stress of the resonant tank. A 3X Ladder RSC prototype for an electronic fuel injection application with maximum output voltage 150 V, maximum power 140 W and peak efficiency 97.6% was designed to be operating in the optimized operation region. The analysis is verified by experimental results.