Series-Capacitor Buck Converter with Soft Turn-On for Datacenters
to 3 MHz.
The resonant series capacitor buck (RSCB) converter with soft turn-on is synthesized by adding a parallel resonant tank next to the series-capacitor Cs, as demonstrated in Fig. 1. All switches turn on into zero-voltage (ZVOn), and low-side switches turn off from zero- current (ZCOff). No snubber is needed to keep the switches stresses within the input voltage. A 2 MHz prototype with 48 V at the input, and 7V - 20 A at the output, was built to verify the design.
The peak efficiency of the RSCB prototype is 98.5%, and the full load efficiency is 97.3%, as shown in Fig. 2. The measured drain- source voltages of all switches at nominal conditions are shown. All switches turn on into zero-voltage.