Optimal Self-Tuning Control for Data-Centers’ 48V-12V ZCS-STC

Abstract

This paper presents a zero-current-switching (ZCS) control method with self-tuning capabilities employed on a 4-to-1 switched-tank converter (STC) for Google’s and associated OCP standard data-centers. The control scheme ensures ZCS operation of each of the STC’s resonant tanks individually, regardless of components mismatch, and adjusts the switching period upon variations of the components’ values. The switching-state of the STC’s resonators is evaluated at the turn-off instance by dedicated zero-current-detection indicator. Two approaches have been developed for the sensor’s data acquisition, accounting for the inherent delay between the digital-controller gating command and the actual turn-off of the switches. The operation of the control has been validated experimentally on 650W 4-to-1 STC with PCB area of 5cmX2cmX0.6cm, demonstrating exceptional self-tuning capabilities over the entire load range and for various component mismatch scenarios. Peak efficiency of 98.6% is achieved at 200W.