Review of energy harvesting techniques and applications for microelectronics

The trends in technology allow the decrease in both size and power consumption of complex digital systems. This decrease in size and power gives rise to new paradigms of computing and use of electronics, with many small devices working collaboratively or at least with strong communication capabilities. Examples of these new paradigms are wearable devices and wireless sensor networks. Currently, these devices are powered by batteries. However, batteries present several disadvantages: the need to either replace or recharge them periodically and their big size and weight compared to high technology electronics. One possibility to overcome these power limitations is to extract (harvest) energy from the environment to either recharge a battery, or even to directly power the electronic device. This paper presents several methods to design an energy harvesting device depending on the type of energy available.Peer Reviewe

System-level simulation of a self-powered sensor with piezoelectric energy harvesting

This paper presents a complete system simulation of a self-powered communication module. The components are described with the Verilog-A language, that allows to merge the electrical and mechanical models of the system. The self-powered sensor system is composed by an energy harvesting piezoelectric generator that powers a RF transmitter. The simulations here presented compare between the case of a battery-less and battery-powered system. The results obtained with the simulation model implemented allow to show how design choices of the system change the periodicity of the transmission and the ability to recharge the battery.Peer Reviewe

Optimum piezoelectric bending beam structures for energy harvesting using shoe inserts

The small amount of power demanded by many present-day electronic devices opens up the possibility to convert part of the energy present in the environment into electrical energy, using several methods. One such method is to use piezoelectric film-bending beams inside a shoe, and use part of the mechanical energy employed during normal walking activity. This study analyzes several bending beam structures suitable for the intended application (shoe inserts and walking-type excitation) and obtains the resulting strain for each type as a function of their geometrical parameters and material properties. As a result, the optimum configuration can be selected.Peer Reviewe

Influència de les Interconnexions en Disseny Microelectrònic

Debido a los actuales niveles de integración que permite la tecnología de fabricación de circuitos integrados, las interconexiones juegan cada vez un papel más importante en el comportamiento de dichos circuitos introduciendo efectos que pueden causar errores en su funcionamiento.Los objetivos de esta tesis son por una parte la modelación adecuada de las interconexiones en circuitos integrados, y por otra parte un estudio del efecto de las señales espureas producidas por efectos parásitos de interconexiones. Se han considerado diferentes modelos de interconexiones con parámetros distribuidos y concentrados, para determinar el rango de validez de cada modelo en función de parámetros de diseño como son longitud de la línea y características de fuente y carga de la línea. Se han realizado medidas experimentales y simulaciones para el caso de líneas sobre sustrato semiconductor para una correcta modelación de estas, observándose que el efecto de la conductancia del sustrato no hace falta incluirlo en el modelo.Finalmente, se ha estudiado el efecto de señales espureas sobre circuitos digitales en base al concepto de curvas de propagación, que han sido calculadas teóricamente y obtenido experimentalmente para ciertos casos.Postprint (published version

Current balancing random body bias in FDSOI cryptosystems as a countermeasure to leakage power analysis attacks

This paper identifies vulnerabilities to recently proposed countermeasures to leakage power analysis attacks in FDSOI systems based on the application of a random body bias. The vulnerabilities are analyzed and the relative difficulty to obtain the secret key, once the vulnerabilities are taken into account, are compared to the original proposals. A new countermeasure, based on a new body bias scheme, is then proposed. The new countermeasure is based on the equalization of asymmetries in static power consumption dependent on data being stored in registers implemented in FDSOI technology. The countermeasure’s effectiveness is theoretically established through the development of a power model based on technological parameters, and further reinforced through numerical simulations of a dummy cryptosystem implementing part of an AES encrypting round.Postprint (published version

All-digital self-adaptive PVTA variation aware clock generation system for DFS

An all-digital self-adaptive clock generation system capable of adapt the clock frequency to compensate the effects of PVTA variations on the IC propagation delay and satisfy an externally set propagation length condition is presented. The design uses time-to-digital converters (TDCs) to measure the propagation length and a variable length ring oscillator (VLRO) to synthesize the clock signal. The VLRO naturally adapts its frequency to the PVTA variations suffered by its logic gates while the TDCs are used to track these variations across the chip and modify the VLRO length in order to adapt the clock frequency to them. The system measurements, for a 45nm FPGA, show that it adapts the VLRO length, and therefore the clock frequency, to satisfy the propagation length condition. Measurements also prove the system capabilities to act as a dynamic frequency scaling clock source since the propagation length condition value act as a frequency selection input and a strong linear relation between the input value and the resultant clock period is present.Peer ReviewedPostprint (author’s final draft

A battery-less, self-sustaining RF energy harvesting circuit with TFETs for µW power applications

This paper proposes a Tunnel FET (TFET) power management circuit for RF energy harvesting applications. In contrast with conventional MOSFET technologies, the improved electrical characteristics of TFETs promise a better behavior in the process of rectification and conversion at ultra-low power (µW) and voltage (sub-0.25 V) levels. RF powered systems can not only benefit from TFETs in front-end rectifiers by harvesting the surrounding energy at levels where conventional technologies cannot operate but also in the minimization of energy required by the power management circuit. In this work we present an energy harvesting circuit for RF sources designed with TFETs. The TFET controller emulates an adequate impedance at the output of the rectifier in order to allow maximum transfer of power from the RF source to the input of the boost converter. The output load is activated once the output capacitor reaches a voltage value of 0.5 V. The results show an efficiency boost of 89 % for an output load consuming 1 µW with an available RF power of -25 dBm.Postprint (published version

Insights into tunnel FET-based charge pumps and rectifiers for energy harvesting applications

In this paper, the electrical characteristics of tunnel field-effect transistor (TFET) devices are explored for energy harvesting front-end circuits with ultralow power consumption. Compared with conventional thermionic technologies, the improved electrical characteristics of TFET devices are expected to increase the power conversion efficiency of front-end charge pumps and rectifiers powered at sub-µW power levels. However, under reverse bias conditions the TFET device presents particular electrical characteristics due to its different carrier injection mechanism. In this paper, it is shown that reverse losses in TFET-based circuits can be attenuated by changing the gate-to-source voltage of reverse-biased TFETs. Therefore, in order to take full advantage of the TFETs in front-end energy harvesting circuits, different circuit approaches are required. In this paper, we propose and discuss different topologies for TFET-based charge pumps and rectifiers for energy harvesting applications.Peer ReviewedPostprint (author's final draft

Linear, time-invariant model of the dynamics of a CMOS CC-CP

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper presents the development of a linear dynamic model of a MOS Cross Coupled Charge Pump (CC-CP) suitable for low voltage energy harvesting systems in the form of a Discrete-Time State-Space set of equations considering the resistive behavior of transistor switches. The dynamic model, easily extendable to a CC-CP of an arbitrary number of stages, includes parasitic elements without loss of generality. The validity of the dynamic model is evaluated through the comparison of Matlab simulations of the model to circuit simulations of an ideal CC-CP.Postprint (author's final draft

Analysis of random body bias application in FDSOI cryptosystems as a countermeasure to leakage-based power analysis attacks

This paper analyses a novel countermeasure to Leakage Power Analysis Attacks based on the application of a random Body Bias voltage level at the beginning of the encryption process. The countermeasure effectiveness is established through the development of a theoretical model of the Pearson correlation coefficient in the presence of a varying body bias under both noiseless assumptions and in the presence of algorithmic noise, and through simulations on a partial cryptosystem implemented in 28 nm FDSOI technology. A study of the effect of averaging power measurements is also developed and contrasted against Monte Carlo simulations of the countermeasure scheme, effectively providing a floor for the increase in required measurements to identify the secret key.Postprint (published version