Comparison of a 12V, 10A, 3MHz buck converter and a series capacitor buck converter

This paper presents a theoretical and experimental comparison of a two-phase buck converter and a two-phase, series capacitor buck converter. The challenges of a conventional buck converter in high current (10 A or more), high frequency (3-30 MHz) point-of-load voltage regulators with large voltage conversion ratios (10-to-1) are discussed. The series capacitor buck converter exhibits characteristics such as lower switching loss, less inductor current ripple, inherit current balancing, duty ratio extension, and soft charging of the series capacitor. Drawbacks include a maximum output voltage limit and the impracticality of phase shedding. Analysis of the topologies indicates that switching loss and inductor core loss can dominate at high frequency. Results from side-by-side 12 V input, 1.2 V output hardware prototypes demonstrate that the series capacitor buck converter has up to 12 percentage points higher efficiency at 3 MHz and reduces power loss by up to 33% at full load (10 A).