Introduction to the Series Capacitor Buck Converter (Rev. A)

The series capacitor buck converter is a dc-dc converter topology that uniquely merges a switched capacitor circuit and a multiphase buck converter. Many of the challenges faced by conventional buck converters are overcome by this converter topology. This enables efficient, high frequency operation and significantly smaller solution size. The series capacitor buck converter has beneficial characteristics such as lower switching loss, less inductor current ripple, automatic inductor current balancing, duty ratio extension, and soft charging of the series capacitor. Drawbacks include a maximum output voltage (or minimum input voltage) limit and the impracticality of phase shedding. This application report analyzes the topology and presents example experimental results from the TPS54A20 voltage regulator designed for 12 V input, 1.2 V output with 10 A full load current.