Design of fully integrated switched-capacitor DC-DC converters for low-power applications

Abstract

To ensure the reliability and sustainability of IoT systems, the integration of on-chip voltage regulators with high power conversion efficiency and compact form factors is imperative, given the inherent limitations of power sources like batteries. Among the various options, switched-capacitor (SC) DC-DC converters emerge as favorable choices due to their high power density and efficiency. This thesis introduces novel topologies of Switched Capacitor (SC) DC-DC converters tailored for low power applications, focusing on two key aspects: Dynamic Voltage Scaling (DVS) and energy harvesting. DVS enhances power efficiency in small IoT devices with limited power sources. SC DC-DC converters prove advantageous for implementing DVS due to their high integrability and cost-effectiveness. This thesis presents a single/dual-output SC DC-DC converter featuring simplified inter-stage connections made in a 2D array topology, enabling voltage conversion ratio (VCR) transitions without charge redistribution loss. This converter achieves high VCR reconfigurability by geometrically arranging bias voltage on flying capacitors within the array. It has the capacity to switch between two VCRs without internal losses. This enables dual outputs with independent control over VCRs and load currents, while still maintaining the ability for soft VCR transitions on both outputs. Energy harvesting has attracted considerable interest as a way to powering IoT devices, extending battery life and enabling self-sustained operations. The challenge lies in designing converters that can adapt to voltage fluctuations from diverse ambient conditions. This thesis introduces a novel topology that strikes a balance between a broad range of VCRs and enhanced conversion efficiency, while minimizing overall circuit complexity. Additionally, it enables multi-mode operations, encompassing both conventional SC topologies and the newly introduced ones, ensuring converters operate effectively across diverse operating conditions.