A 1.02 μW Autarkic Threshold-Based Sensing and Energy Harvesting Interface Using a Single Piezoelectric Element

A self-powered piezoelectric sensor interface employing part of the signal that is not intended for measurement to sustain its autonomous operation was designed using XH018 (180 nm) technology. The aim of the proposed circuit, besides the energy self-sufficiency of the sensor, is to provide an interface that eliminates the effect of the harvesting process on the piezoelectric output signal which contains context data. This is achieved by isolating part of the signal that is desirable for sensing from the harvesting process so that the former is not affected or distorted by the latter. Moreover, the circuit manages to self-start its operation, so no additional battery or pre-charged capacitor is needed. The circuit achieves a very low power consumption of 1.02 μW. As a proof of concept, the proposed interfacing circuit is implemented in order to be potentially used for weigh-in-motion applications

Σχεδιασμός ηλεκτρονικών κυκλωμάτων για εφαρμογές ΙοΤ

With the emergence of the Internet of Things (IoT) era, the development of an infinite number of services and applications has become achievable. The employment of a variety of sensors in IoT systems is widespread in applications involving healthcare, environmental monitoring, weather forecasting, traffic flow etc. Since most sensor systems are installed in remote and hard-to-reach environments, where they are expected to operate for extended periods without the frequent need of battery replacement, their energy efficiency is a critical parameter. Thus, various design techniques and improvements have been utilized to prolong the operation of these systems, such as an intermittent style of operation of the sensors, the utilization of energy harvesting from environmental power sources, as well as the minimization of the power consumption of the sensor electronics. It is essential that the energy efficiency aspect of design does not interfere with the effective operation of the sensing system, i.e., the low-noise operation is not traded off for the low-power operation. Therefore, a combination of these two typically counteractive design characteristics is attempted. As a case study, an electric field mill sensor, which is a sensor that is typically installed in remote areas and should operate for extended periods, is examined in a weather forecasting application. Additionally, the piezoelectric element, which is widely employed as a sensor in inaccessible environments (bridges, roads, building surfaces) is examined in applications where its ability to also act as an energy harvester is exploited to design self-powered IoT sensing systems. In the beginning of this dissertation, the description of the electric field mill sensor’s most significant design characteristics as well as its non-idealities which can affect its sensitivity, or its efficient operation is provided. Both a discrete and an integrated implementation of the prototype sensor’s interface circuitry are designed, taking into consideration the low-noise requirement for the preamplification stage and the low power consumption of the entire system. Next, an overview of Maximum Power Point Tracking (MPPT) techniques and algorithms employed in energy harvesting systems that can enable the energy-autonomous operation of sensing systems is provided and the design of circuits that are embedded in such systems is presented. An energy harvesting module that can supply the operation of a Wireless Sensor Node and a low-power field mill sensor and its analog readout is tested in real conditions. In addition, the capability of the piezoelectric transducer to be utilized both as a sensor and as an energy harvester is examined and tested in two applications; the first is a Weigh-in-Motion sensing circuit, where the transducer is also employed in an energy harvesting module and the second is a Maximum Power Point Tracking technique implementation for piezoelectric energy harvesters. Finally, the conclusions derived from this work as well as future research directions are discussed.Η ανάδυση της εποχής του Διαδικτύου των Πραγμάτων (Internet of Things, IoT), καθιστά εφικτή την ανάπτυξη απεριόριστου αριθμού υπηρεσιών και εφαρμογών. Η χρήση ποικίλων αισθητήρων σε συστήματα IoT είναι διαδεδομένη σε εφαρμογές που αφορούν τους τομείς της υγείας, του περιβάλλοντος, της πρόγνωσης του καιρού, της κυκλοφοριακής ροής κλπ. Καθώς η πλειοψηφία των συστημάτων αισθητήρων εγκαθίσταται σε απομακρυσμένα και δυσπρόσιτα περιβάλλοντα, όπου αναμένεται να λειτουργούν για μεγάλα χρονικά διαστήματα χωρίς την ανάγκη συχνής αντικατάστασης μπαταριών, η ενεργειακά αποδοτική λειτουργία τους αποτελεί κρίσιμη παράμετρο. Ως εκ τούτου, χρησιμοποιούνται διάφορες τεχνικές και βελτιώσεις σχεδίασης ώστε να παρατείνεται η λειτουργία των συστημάτων αυτών, όπως ο διακοπτόμενος τρόπος λειτουργίας των αισθητήρων, η συγκομιδή ενέργειας από περιβάλλουσες πηγές ενέργειας, καθώς και η ελαχιστοποίηση της κατανάλωσης των ηλεκτρονικών του αισθητήρα. Είναι απαραίτητο η βελτιστοποίηση στην κατανάλωση της ενέργειας κατά τη σχεδίαση να μην επηρεάζει την αποδοτική λειτουργία του συστήματος αισθητήρα, δηλαδή η λειτουργία με χαμηλό θόρυβο να μην ανταλλάσσεται με τη λειτουργία χαμηλής κατανάλωσης. Επιλέχθηκε για μελέτη ο αισθητήρας μέτρησης ηλεκτρικού πεδίου (electric field mill) ως παράδειγμα αισθητήρα, ο οποίος τοποθετείται σε απομακρυσμένες περιοχές και λειτουργεί για μεγάλα χρονικά διαστήματα. Επιπρόσθετα, το πιεζοηλεκτρικό στοιχείο, το οποίο χρησιμοποιείται ευρέως ως αισθητήρας σε δυσπρόσιτα περιβάλλοντα (γέφυρες, οδώστρωμα, επιφάνειες κτιρίων), εξετάζεται σε εφαρμογές όπου αξιοποιείται η δυνατότητα χρήσης του και ως μετατροπέα ενέργειας για τη σχεδίαση αυτοτροφοδοτούμενων IoT συστημάτων αισθητήρων. Στο πρώτο σκέλος της διατριβής περιγράφονται τα σημαντικότερα δομικά χαρακτηριστικά του αισθητήρα ηλεκτρικού πεδίου, καθώς και οι παράμετροι που δύνανται να επηρεάσουν την ευαισθησία ή την αποδοτική λειτουργία του. Σχεδιάζεται μία υλοποίηση των κυκλωμάτων της διεπαφής του αισθητήρα με διακριτά στοιχεία, καθώς και μία ολοκληρωμένη υλοποίηση, αμφότερες με γνώμονα τις απαιτήσεις χαμηλού θορύβου του σταδίου προενίσχυσης και τη χαμηλή κατανάλωση του συνολικού συστήματος. Στη συνέχεια πραγματοποιείται μια επισκόπηση τεχνικών και αλγορίθμων εντοπισμού του σημείου λειτουργίας μέγιστης ισχύος (Maximum Power Point Tracking, MPPT) που χρησιμοποιούνται σε συστήματα συγκομιδής ενέργειας τα οποία παρέχουν τη δυνατότητα ενεργειακά αυτόνομης λειτουργίας των συστημάτων αισθητήρων και παρουσιάζονται κυκλώματα τα οποία μπορούν να ενσωματωθούν σε τέτοια συστήματα. Εξετάζεται ένα κύκλωμα συγκομιδής ενέργειας το οποίο μπορεί να τροφοδοτήσει με διακοπτόμενο τρόπο τη λειτουργία ενός ασύρματου κόμβου αισθητήρα (Wireless Sensor Node), καθώς και ενός αισθητήρα ηλεκτρικού πεδίου χαμηλής κατανάλωσης και των ηλεκτρονικών ανάγνωσής του. Επιπρόσθετα, εξετάζεται η δυνατότητα ταυτόχρονης χρήσης του πιεζοηλεκτρικού στοιχείου ως αισθητήρα και ως μετατροπέα ενέργειας και επαληθεύεται μέσω δύο εφαρμογών: η πρώτη αφορά τη μέτρηση ενός φορτίου σε κίνηση (Weigh-in-Motion), όπου το πιεζοηλεκτρικό στοιχείο εκτός από αισθητήρας χρησιμοποιείται και σε ένα σύστημα συγκομιδής ενέργειας και η δεύτερη αποτελεί μια υλοποίηση τεχνικής MPPT για πιεζοηλεκτρικούς μετατροπείς ενέργειας. Τέλος, παρατίθενται τα συμπεράσματα και οι μελλοντικές ερευνητικές κατευθύνσεις

Analog Sensor Interface for Field Mill Sensors in Atmospheric Applications

An overview of the electric field mill sensor specifications in applications related to the measurement of the atmospheric electric field was conducted. The different design approaches of the field mill sensor interface are presented and analyzed, while the sensitivity-related parameters of a field mill are discussed. The design of a non-complex analog sensor interface that can be employed for the measurement of the electric field in both fair and foul weather conditions, such as thunderstorms, is implemented using discrete components for experimental validation and is optimized in an integrated version in terms of noise and power consumption. Advanced noise simulations are conducted in a 180 nm CMOS process (XH018 XFAB). The energy-autonomous operation of the sensor for extended periods of time is made feasible due to the low power consumption of the front-end circuitry (165 μW at 3 V) as well as the proposed intermittent style of operation of the motor. The total sensing system is low power, and its realization is simple and cost-effective, while also offering adequate sensitivity (45 mV/kV/m), making it comparable to the existing works

Integrated Filter Design for Analog Field Mill Sensor Interface

The design process of an integrated bandpass filter targeted for the noise filtering stage of the synchronous demodulation unit of an electric field mill sensor interface is presented. The purpose of this study of filter integration techniques is to avoid the challenging and, in some cases, impossible passive element integration process and to incorporate the final filter design in an entirely integrated field mill sensing system with superior performance and an optimized silicon-to-cost ratio. Four different CMOS filter implementations in the 0.18 μm process of XFAB, using OTA (Operational Transconductance Amplifier)-based configurations for passive element replacement in cascaded filter topologies and leapfrog techniques, are compared in terms of noise performance, total harmonic distortion, dynamic range, and power consumption, as well as in terms of integrability, silicon area, and performance degradation at process corners/mismatches. The optimum filter design performance-wise and process-wise is included in the final design of the integrated analog readout of a field mill sensor, and post-layout simulation results of the total circuit are presented

Experimental study of a low-voltage PV cell-level DC/AC converter

Summarization: This paper focuses on the design of a low-voltage power converter for an on-chip PV cell-level inverter. Various topologies are discussed for the DC/DC stage, whereas the ZVS quasi-resonant boost and the synchronous boost are considered the most appropriate for this application. Both the aforementioned topologies are modeled and evaluated in terms of efficiency, by the aid of PSpice simulations. Due to requirements and limitations of the available 0.18 μm CMOS process technology, the synchronous boost is finally chosen as the most appropriate solution. As for the DC/AC stage, the H-bridge inverter configuration is selected, as a simple, compact and cost-effective solution. A prototype converter is designed and constructed with discrete components, so as to validate the functionality and performance of the proposed system. Finally, experimental results are presented, indicating the high efficiency that can be achieved.Παρουσιάστηκε στο: 2021 10th International Conference on Modern Circuits and Systems Technologie

Analysis, design and simulation of an on-chip DC/DC/AC conversion system for PV applications

Summarization: This paper presents the analysis and design procedure of a low voltage, reconfigurable, on-chip DC/DC - DC/AC power conversion system for PV applications. The whole work is carried out in the context of a novel smart PV system development, which is based on integrated PV cell inverters. Various power converter topologies are investigated in order the most appropriate for the DC/DC and DC/AC power stages to be selected. The synchronous boost DC/DC converter and the H-bridge inverter are the preferred solution, in terms of complexity, efficiency and cost. The specifications of the power conversion system are given, along with the theoretical analysis for the synchronous boost converter and H-bridge inverter operation. Moreover, the chip design process is presented, highlighting the design constraints and limitations obtained. Finally, in order the functionality of the above concept to be validated, PSpice simulations are carried out, indicating the high efficiency and low complexity of the proposed power conversion system.Παρουσιάστηκε στο: 5th Panhellenic Conference on Electronics and Telecommunication

Design considerations for a DC-DC boost converter in standard CMOS technology

Summarization: In this paper, the challenges of designing a boost converter in standard CMOS technology are discussed. Based on theoretical calculations, which take into consideration the characteristics of the technology used, efficient solutions are proposed to overcome the current-stress limitations as well as the power dissipation issues. Following these guidelines, a test DC-DC converter, designed and fabricated in a standard 0.18um CMOS process is presented, along with experimental results.Παρουσιάστηκε στο: 2021 10th International Conference on Modern Circuits and Systems Technologie