Hybrid Switched-Capacitor Circuits and Magnetics Co-Design for Vertical Power Delivery

Abstract

The increasing demands of high-performance computing, driven by widespread adoption of artificial intelligence, necessitate power electronics that are energy efficient, have high power densities, and respond quickly to load transients. Power architectures must leverage advances in semiconductors, passive components, and heterogeneous integration for high density, efficiency, and speed. Vertical power delivery is a promising approach to improving end-to-end efficiency in power conversion for high density loads by reducing interconnect resistance, electromagnetic interference, and converter area. This thesis introduces the challenges of vertical power delivery for microprocessor applications, which require high efficiency, power density, and control bandwidth. These metrics are crucial for thermal performance, power and signal integrity, and packaging. A vertical stacked heterogeneous packaging model is proposed for vertical-stacked converters, optimizing the function of the capacitor, switch, and magnetics layers, exploiting their scaling laws for compact packaging. Next, a hybrid switched-capacitor magnetics architecture is introduced that addresses the necessary tradeoffs for vertical power delivery – the Linearly-Extendable Group-Operated Point-of-Load (LEGO-PoL) architecture – together with multiple critical techniques to achieve high performance. The LEGO-PoL architecture uses a hybrid switched-capacitor topology together with coupled magnetics and vertical-stacked packaging to deliver high output currents within a small area with low height and high efficiency. Two LEGO-PoL prototypes are built and tested to validate the architecture for vertical power delivery. The first LEGO-PoL prototype has a height of 16.65 mm and delivers 450 A of current for 48-V-to-1-V conversion with 88.4% peak efficiency and 294 W/in^3 power density. The second prototype, Mini-LEGO, re-designs the converter with a height of 8.4 mm and a peak efficiency of 84.1%, trading off some efficiency for a significant improvement in power density to 1390 W/in^3. Lastly, by merging and coupling multiple magnetic components into one, benefits in size reduction, performance improvement, and control bandwidth are achieved. This thesis quantifies the benefits of coupled magnetics and introduces geometries and optimization methods for vertical power delivery coupled inductors. Three inductors are fabricated to demonstrate the magnetics design methodology for vertical coupled inductors at frequencies of 1 MHz, 1.5 MHz, and 2 MHz. The pinwheel coupled inductor design presented for 2 MHz underscores the vision for vertical magnetics with power-via interconnects that deliver high current with low profile and low impedance. The LEGO-PoL architecture and the development of vertical coupled magnetics pave the way for vertical power delivery as a promising approach to resolving the tradeoffs of performance, size, and speed, and meeting the growing energy demands of future high power density applications.