Design, Analysis and Optimization of Magnetic-Core Solenoid Inductor for On-Chip Multi-Phase Buck Converter

Abstract

Due to heterogeneous integration, there is an increased demand for on-chip DC-DC converters to provide multiple voltage domains for efficient operation of the system. Towards this, planar magnetic-core based inductors gained popularity due to their increased inductance density for on-chip buck converter realization. To ensure proper operation of the converter, the magnetic-core should not saturate, and over-design of the inductor decreases the converter efficiency significantly. Also, the magnetic-core area budget is limited for on-chip design. This paper proposes an optimization framework to design an efficient multi-phase buck converter with the magnetic-core solenoid inductor for the given specifications. We investigate two cost-functions for optimization where Cost function <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> considers only power loss reduction, whereas Cost function <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> considers both power loss and inductor footprint. Full-wave simulations on commercial tool show that the optimized multi-phase buck converter with 500 mA load current achieves 88.13% and 88.06% efficiency for Cost function <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and Cost function <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , respectively. The footprint for the optimized inductor with Cost function <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has a 10% reduction compared with the optimized inductor with Cost function <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> .