Efficient Archietecture for Effective Utilization of Harvested Power in Microscale Energy Harvesting

Recent developments in combining sensors, microprocessors, and radio frequency (RF) communications holds the potential to revolutionize the way we monitor and maintain critical systems. In the future, literally billions of wireless sensors may become deeply embedded within machines, structures, and the environment. Sensed information will be automatically collected, compressed, and forwarded for condition based maintenance. Energy Harvesting comprises a promising solution to one of the key problems faced by battery-powered Wireless Sensor Networks, namely the limited nature of the energy supply (finite battery capacity). By harvesting energy from the surrounding environment, the sensors can have a continuous lifetime without any needs for battery recharge or replacement

TOPOLOGY, ANALYSIS, AND CMOS IMPLEMENTATION OF SWITCHED-CAPACITOR DC-DC CONVERTERS

This review highlights various design and realization aspects of three commonly used charge pump topologies, namely, the linear, exponential, and the Fibonacci type of charge pumps. We shall outline the new methods developed recently for analyzing the steady and dynamic performances of these circuits. Some practical issues for the CMOS implementation of these charge pump structures will be critically discussed. Finally, some conventional voltage regulation methods for maintaining a stable output under a large range of loading current and supply voltage fluctuations will be proposed

Platform Independent, Illumination aware Reconfigurable Switch Capacitor based 3.3 Volt Energy Harvester IC

This dissertation presents a platform independent illumination aware fully on chip microscale energy harvester for powering 3.3V sensor nodes and smart IOT devices. The programmable switched capacitor DC-DC converter for fully on chip applications is discussed and implemented

A Charge-Recycling Scheme and Ultra Low Voltage Self-Startup Charge Pump for Highly Energy Efficient Mixed Signal Systems-On-A-Chip

The advent of battery operated sensor-based electronic systems has provided a pressing need to design energy-efficient, ultra-low power integrated circuits as a means to improve the battery lifetime. This dissertation describes a scheme to lower the power requirement of a digital circuit through the use of charge-recycling and dynamic supply-voltage scaling techniques. The novel charge-recycling scheme proposed in this research demonstrates the feasibility of operating digital circuits using the charge scavenged from the leakage and dynamic load currents inherent to digital design. The proposed scheme efficiently gathers the “ground-bound” charge into storage capacitor banks. This reclaimed charge is then subsequently recycled to power the source digital circuit. The charge-recycling methodology has been implemented on a 12-bit Gray-code counter operating at frequencies of less than 50 MHz. The circuit has been designed in a 90-nm process and measurement results reveal more than 41% reduction in the average energy consumption of the counter. The total energy savings including the power consumed for the generation of control signals aggregates to an average of 23%. The proposed methodology can be applied to an existing digital path without any design change to the circuit but with only small loss to the performance. Potential applications of this scheme are described, specifically in wide-temperature dynamic power reduction and as a source for energy harvesters. The second part of this dissertation deals with the design and development of a self-starting, ultra-low voltage, switched-capacitor (SC) DC-DC converter that is essential to an energy harvesting system. The proposed charge-pump based SC-converter operates from 125-mV input and thus enables battery-less operation in ultra-low voltage energy harvesters. The charge pump does not require any external components or expensive post-fabrication processing to enable low-voltage operation. This design has been implemented in a 130-nm CMOS process. While the proposed charge pump provides significant efficiency enhancement in energy harvesters, it can also be incorporated within charge recycling systems to facilitate adaptable charge-recycling levels. In total, this dissertation provides key components needed for highly energy-efficient mixed signal systems-on-a-chip