Power efficiency comparison for various MIM tile structures of fully integrated two-phase 2:1 SCVR for photovoltaic applications

Abstract

Fully integrated switched capacitor voltage regulators are evolved as promising devices for solar photovoltaic systems as they can efficiently convert one voltage level into another. This work introduces a novel approach for enhancing the power efficiency of fully integrated switched capacitor voltage regulators specifically designed for solar photovoltaic systems. A general steady-state performance model of switched capacitor converter is investigated using charge-multiplier approach. In order to improve the converter efficiency in the presence of parasitic losses, the basic switched capacitor converter analysis is extended to incorporate expressions for the lowest attainable power loss using on-die high-density capacitor. The novelty of this study lies in the investigation of integrated metal–insulator-metal capacitors with various tile structures, which are utilized to realize compact, fully integrated DC-DC converters with enhanced efficiency for photovoltaic applications. This work presents a comparative study of different MIM capacitor tile structures of a two-phase 2:1 series–parallel converter operating at an input voltage of 1.24 V. The efficiency of these structures is evaluated by considering various factors, including the impact of switch and pre-driver parasitic. The analysis is done to optimally select the component values, switch size, capacitance and switching frequency for a two-phase 2:1 series–parallel converter implemented in 22 nm tri-gate process technology. Through a comprehensive set of cross-corner PSpice simulations, the impact of different MIM capacitor tile structures on converter efficiency is investigated at current densities of 400 mA/mm² and 650 mA/mm², respectively. The results shows that MIM tile1 (corresponding to the core height) exhibits approximately 0.5 % lower efficiency than MIM tile2 (corresponding to half of the core height) at the lower current density of 400 mA/mm², with a slightly larger efficiency reduction of about 1 % observed at the higher current density of 650 mA/mm². The results are validated using MATLAB and PSpice simulation tools.