Buck-boost switched-capacitor DC-DC voltage regulator using delta-sigma control loop

This paper presents a delta-sigma control loop for a buck-boost dc-dc converter with fractional gains. The charge pump used to convert the input voltage acts as a D/A converter in the loop, and its output ripple is frequency shaped by the loop, which also provides the pulse- frequency modulation needed for the conversion. A test chip realised in a 0.72-μm CMOS process and clocked at 1MHz provided suppression of tones up to 50dB in the 0-500kHz range. The target output voltage may be from 1.8V to 4V for loads up to 150mA. The input voltage range is 3V to 5V. 1

Power Management Circuits for Energy Harvesting Applications

Energy harvesting is the process of converting ambient available energy into usable electrical energy. Multiple types of sources are can be used to harness environmental energy: solar cells, kinetic transducers, thermal energy, and electromagnetic waves. This dissertation proposal focuses on the design of high efficiency, ultra-low power, power management units for DC energy harvesting sources. New architectures and design techniques are introduced to achieve high efficiency and performance while achieving maximum power extraction from the sources. The first part of the dissertation focuses on the application of inductive switching regulators and their use in energy harvesting applications. The second implements capacitive switching regulators to minimize the use of external components and present a minimal footprint solution for energy harvesting power management. Analysis and theoretical background for all switching regulators and linear regulators are described in detail. Both solutions demonstrate how low power, high efficiency design allows for a self-sustaining, operational device which can tackle the two main concerns for energy harvesting: maximum power extraction and voltage regulation. Furthermore, a practical demonstration with an Internet of Things type node is tested and positive results shown by a fully powered device from harvested energy. All systems were designed, implemented and tested to demonstrate proof-of-concept prototypes