Multi-Input Single-Inductor MPPT Regulator with Sliding-Mode Controller

abstract: A Multi-input single inductor dual-output Boost based architecture for Multi-junction PV energy harvesting source is presented. The system works in Discontinuous Conduction Mode to achieve the independent input regulation for multi-junction PV source. A dual-output path is implemented to regulate the output at 3V as well as store the extra energy at light load condition. The dual-loop based sliding-mode MPPT for multi-junction PV is proposed to speed up the system response time for prompt irradiation change as well as maximize MPPT efficiency. The whole system achieves peak efficiency of 83% and MPPT efficiency of 95%. The whole system is designed, simulated in Cadence and implemented in PCB platform.Dissertation/ThesisMasters Thesis Electrical Engineering 201

GAN LIGHT EMISSION CONTROLLED DC-DC CONVERTER

This work demonstrates the very first implementation of electroluminescence from a gallium nitride vertical diode as a feedback mechanism for real-time current control of a power converter. Current estimation via electroluminescence provides a galvanically isolated sensor capability that is not susceptible to electromagnetic interference, which is inherently produced in switch mode power supplies. The light feedback is converted to an electrical signal that is further digitally filtered to construct a 3D current calibration surface. This surface converts duty cycle and light signal intensity into a real-time current estimation utilized as a feedback parameter in a buck converter control system. The accuracy of current estimation is shown to be within 5% of steady-state current over various load conditions. Transient-state response was also demonstrated for step changes in commanded current and voltage within the power converter. Methods of increasing accuracy and reducing current estimation delay time are discussed.Lieutenant, United States NavyApproved for public release. Distribution is unlimited

Robustness and durability aspects in the design of power management circuits for IoT applications

With the increasing interest in the heterogeneous world of the “Internet of Things” (IoT), new compelling challenges arise in the field of electronic design, especially concerning the development of innovative power management solutions. Being this diffusion a consolidated reality nowadays, emerging needs like lifetime, durability and robustness are becoming the new watchwords for power management, being a common ground which can dramatically improve service life and confidence in these devices. The possibility to design nodes which do not need external power supply is a crucial point in this scenario. Moreover, the development of autonomous nodes which are substantially maintenance free, and which therefore can be placed in unreachable or harsh environments is another enabling aspect for the exploitation of this technology. In this respect, the study of energy harvesting techniques is increasingly earning interest again. Along with efficiency aspects, degradation aspects are the other main research field with respect to lifetime, durability and robustness of IoT devices, especially related to aging mechanisms which are peculiar in power management and power conversion circuits, like for example battery wear during usage or hot-carrier degradation (HCD) in power MOSFETs. In this thesis different aspects related to lifetime, durability and robustness in the field of power management circuits are studied, leading to interesting contributions. Innovative designs of DC/DC power converters are studied and developed, especially related to reliability aspects of the use of electrochemical cells as power sources. Moreover, an advanced IoT node is proposed, based on energy harvesting techniques, which features an intelligent dynamically adaptive power management circuit. As a further contribution, a novel algorithm is proposed, which is able to effectively estimate the efficiency of a DC/DC converter for photovoltaic applications at runtime. Finally, an innovative DC/DC power converter with embedded monitoring of hot-carrier degradation in power MOSFETs is designed

Power Management ICs for Internet of Things, Energy Harvesting and Biomedical Devices

This dissertation focuses on the power management unit (PMU) and integrated circuits (ICs) for the internet of things (IoT), energy harvesting and biomedical devices. Three monolithic power harvesting methods are studied for different challenges of smart nodes of IoT networks. Firstly, we propose that an impedance tuning approach is implemented with a capacitor value modulation to eliminate the quiescent power consumption. Secondly, we develop a hill-climbing MPPT mechanism that reuses and processes the information of the hysteresis controller in the time-domain and is free of power hungry analog circuits. Furthermore, the typical power-performance tradeoff of the hysteresis controller is solved by a self-triggered one-shot mechanism. Thus, the output regulation achieves high-performance and yet low-power operations as low as 12 µW. Thirdly, we introduce a reconfigurable charge pump to provide the hybrid conversion ratios (CRs) as 1⅓× up to 8× for minimizing the charge redistribution loss. The reconfigurable feature also dynamically tunes to maximum power point tracking (MPPT) with the frequency modulation, resulting in a two-dimensional MPPT. Therefore, the voltage conversion efficiency (VCE) and the power conversion efficiency (PCE) are enhanced and flattened across a wide harvesting range as 0.45 to 3 V. In a conclusion, we successfully develop an energy harvesting method for the IoT smart nodes with lower cost, smaller size, higher conversion efficiency, and better applicability. For the biomedical devices, this dissertation presents a novel cost-effective automatic resonance tracking method with maximum power transfer (MPT) for piezoelectric transducers (PT). The proposed tracking method is based on a band-pass filter (BPF) oscillator, exploiting the PT’s intrinsic resonance point through a sensing bridge. It guarantees automatic resonance tracking and maximum electrical power converted into mechanical motion regardless of process variations and environmental interferences. Thus, the proposed BPF oscillator-based scheme was designed for an ultrasonic vessel sealing and dissecting (UVSD) system. The sealing and dissecting functions were verified experimentally in chicken tissue and glycerin. Furthermore, a combined sensing scheme circuit allows multiple surgical tissue debulking, vessel sealer and dissector (VSD) technologies to operate from the same sensing scheme board. Its advantage is that a single driver controller could be used for both systems simplifying the complexity and design cost. In a conclusion, we successfully develop an ultrasonic scalpel to replace the other electrosurgical counterparts and the conventional scalpels with lower cost and better functionality

Efficient power management circuits for energy harvesting applications

Low power IoT devices are growing in numbers and by 2020 there will be more than 25 Billion of those in areas such as wearables, smart homes, remote surveillance, transportation and industrial systems, including many others. Many IoT electronics either will operate from stand-alone energy supply (e.g., battery) or be self-powered by harvesting from ambient energy sources or have both options. Harvesting sustainable energy from ambient environment plays significant role in extending the operation lifetime of these devices and hence, lower the maintenance cost of the system, which in turn help make them integral to simpler systems. Both for battery-powered and harvesting capable systems, efficient power delivery unit remains an essential component for maximizing energy efficiency. The goal of this research is to investigate the challenges of energy delivery for low power electronics considering both energy harvesting as well as battery-powered conditions and to address those challenges. Different challenges of energy harvesting from low voltage energy sources based on the limitations of the sources, the type of the regulator used and the pattern of the load demands have been investigated. Different aspects of the each challenges are further investigated to seek optimized solutions for both load specific and generalized applications. A voltage boost mechanism is chosen as the primary mechanism to investigate and to addressing those challenges, befitting the need for low power applications which often rely on battery voltage or on low voltage energy harvesting sources. Additionally, a multiple output buck regulator is also discussed. The challenges analyzed include very low voltage start up issues for an inductive boost regulator, cascading of boost regulator stages, and reduction of the number of external component through reusing those. Design techniques for very high conversion ratio, bias current reduction with autonomous bias gating, battery-less cold start, component and power stage multiplexing for reconfigurable and multi-domain regulators are presented. Measurement results from several silicon prototypes are also presented.Ph.D

Design Space Evaluation for Resonant and Hard-charged Switched Capacitor Converters

USB Power Delivery enables a fixed ratio converter to operate over a wider range of output voltages by varying the input voltage. Of the DC/DC step-down converters powered from this type of USB, the hard-charged Switched Capacitor circuit is of interest to industry for its potential high power density. However implementation can be limited by circuit efficiency. In fully resonant mode, the efficiency can be improved while also enabling current regulation. This expands the possible applications into battery chargers and eliminates the need for a two-stage converter.In this work, the trade-off in power loss and area between the hard-charged and fully resonant switched capacitor circuit is explored using a technique that remains agnostic to inductor technology. The loss model for each converter is presented as well as discussion on the restrained design space due to parasitics in the passive components. The results are validated experimentally using GaN-based prototype converters and the respective design spaces are analyzed

Design of low-power RF energy harvester for IoT sensors

Rapid technological advancement in CMOS technologies has resulted in increased deployment of low-power Internet-of-Things (IoT) devices. As batteries, used to power-up these devices, suffer from limited lifespan, powering up numerous devices have become a major concern. Radio frequency (RF) is ubiquitous in the surroundings from which energy can be harvested and utilized to increase battery lifetime. Even for low-power sensors, RF energy harvesters can be utilized as primary power sources. However, power density of RF signals is very low and therefore building blocks of RF energy harvester need to be designed carefully to maximize efficiency to gain suitable output power. This research is focused on the design of an RF energy harvesting system in standard CMOS technology. The main goal of this research is to design an RF energy harvesting system with high power conversion efficiency (PCE) and adequate output voltage for low input power. The proposed dynamic voltage compensated cross-coupled fully differential rectifier is capable of providing very high PCE. The synchronous DC-DC boost converter provides stable DC output voltage. Rectifier and DC-DC converter of the system have been designed by using low-power transistors to ensure operation at very low input power. In order to maximize the power transfer through the system, matching network and maximum power point tracking (MPPT) controller has been implemented. In order to cope with rapid input power variation, a machine learning (ML) based MPPT controller has been designed and implemented into FPGA. The proposed ML based MPPT controller has demonstrated fast response time. To further enhance the performance of the RF energy harvesting system, a self-compensated rectifier integrated energy harvesting system is also presented. The energy extracted by using the proposed RF energy harvesting systems can easily be stored and utilized to fully power up low-power sensors used for IoT devices. Integration of RF energy harvester with these devices will significantly reduce the maintenance cost and result in energy-effluent IoT technologies.Includes bibliographical references

Energy Harvesting Systems for the Internet of Things with Applications to Smart Agriculture

The Internet of Things is the interconnection of everyday objects to the web, with the purpose of exchanging information to enable smarter actions and potentially make a process more efficient. However, how power is provided and stored in remote sensing applications is still one of the main modern electronics challenges of such technology and can become one of the main constraints to prevent its mass adoption. Energy Harvesting is an emerging technology that can transform energy in the environment into usable energy, among such environmental energy are electromagnetic waves, thermal, solar, kinesthetic transducers, fuel cells, to name a few. Because this technology makes use of the available ambient energy, it has the potential to increase the power readiness for battery-operated electronics and more importantly, it can become the technology that fully powers the next generation of internet-enabled agricultural solutions. This dissertation centers around the design and development of high-efficient power management systems for AC and DC energy harvesting sources. The proposed architectures not only consider circuits, systems and algorithms that make a more efficient power extraction but also focuses on providing inherent sensing functionalities at no extra system complexity, which in turn not only achieves the goal of extending the battery life of proposed smart sensor applications but also proposes new charge extraction methods to permanently power an electronic device. The work presented in this dissertation demonstrates that energy harvesting, and internet of things devices can be implemented in multiple smart agriculture scenarios by proposing algorithms, circuits and systems capable of performing energy harvesting operations while providing reliable data to the end user. The analysis of the design of such proof-of-concept prototypes are provided in this dissertation along with its implementation and testing. The first part of this dissertation proposes novel algorithms for maximum power extraction and new power measurement techniques. The second part focuses on front-end circuits for AC energy harvesting sources and circuits that can provide sensing capabilities along with energy harvesting operations

Emerging Power Electronics Technologies for Sustainable Energy Conversion

This Special Issue summarizes, in a single reference, timely emerging topics related to power electronics for sustainable energy conversion. Furthermore, at the same time, it provides the reader with valuable information related to open research opportunity niches