Comparison of 100V-28V Switched-Capacitor DC-DC Converters Based on Cascaded Buck, Boost and 3-Level Buck Topologies for Space Application

Hybrid switched-capacitor converters for power delivery in space applications are rare. However, in other sectors they are popular due to the size reduction compared with conventional topologies such as the buck. This paper reviews the state of the art of non-isolated step down DC-DC converters based on switched-capacitors. It then analyses several multi-stage solutions based on cascaded buck, boost and 3-level buck (resonant and non-resonant) converters, for a 1 kW, 100 V to 28 V space application. The three-level buck topology halves the total size of the traditional buck converter, maintaining efficiencies above 97 %. It is also shown that in this application, for a switching frequency of 300 kHz, transistor losses in boundary conduction mode can be above two times smaller than in continuous conduction mode using GaN. The final result of the theoretical comparison concludes that the analysed hybrid converter offers great performance enhancement, accepting the more complicated topology design. In addition, it is shown a preliminar prototype of the selected converter, as well as the design considerations for its inductor.