UC San Diego

Amid the surge in advanced technologies such as consumer electronics, the Internet of Things (IoTs), and data centers, the demands on DC-DC converters have become unprecedentedly stringent, driven by the need for miniaturized converters with enhanced performance. This requirement for high performance in a compact design presents significant challenges to current technologies, necessitating novel control strategies, materials, and topologies. For instance, voltage regulator modules (VRMs) in recent data center applications require outputs of several hundred amperes at sub-1V scales, with stringent load transient requirements where the slew rate can be as fast as 1A/ns. This demands the implementation of fast-transient, multiple-phase control strategies to support system operations. On the other hand, for miniature DC-DC converters, the strategy typically involves increasing the operation frequency with zero-voltage switching (ZVS) technique to reduce the size of passive components, particularly magnetic components, which are recognized as the major obstacle in miniaturizing converters. However, magnetic components exhibit sub-linear volume/frequency scaling, implying limitations in minimizing converter size. Thus, the development of new materials for energy storage/processing devices, which act like magnetic components, with favorable scaling properties is desired. This thesis introduces a novel constant on-time (COT) control strategy based on the conventional step-down converter, specifically Buck converter, for which supports multi-phase operation and delivers a fast load transient response without the need for additional ramp compensation, unlike traditional COT control schemes. Subsequently, the uses of piezoelectric materials, particularly piezoelectric resonators (PRs) are explored. The piezoelectric materials have been widely used in ultrasonic sensors, actuators, and energy harvesting applications and have recently been incorporated into power converters due to their excellent volume/frequency scaling properties, which facilitate compact DC-DC converter designs. Following the introduction of the materials, this thesis proposes and compares various hybrid PR-based DC-DC topologies across both discrete and integrated circuit (IC) implementations.