Design of a Power Management Circuit for an Opto-Electro Stimulator

This paper presents the design of an integrated power management circuit for use in an implantable opto-electro stimulator. It features an active rectifier with pulse width modulation (PWM) regulation to generate a 3.3 V regulated output, and a 3-stage high voltage charge pump (CP) that generates a 12 V output from a 3.3 V input with a 20 MHz, two-phase non-overlapping clock generator. The circuits were designed in a 0.18-µm CMOS technology requiring a chip area of 0.048 mm 2 . Simulation results show that the regulating rectifier has a voltage conversion efficiency of 94.3% and 92.8% with an ac input magnitude of 3.5 V and 3.6 V, respectively. The peak power transfer efficiency of the regulated 3.3V output voltage is 70.7% with a maximum output power of 30.3 mW. The CP with an overall on-chip capacitance is 60 pF

High Efficiency Power Management Unit for Implantable Optical-Electrical Stimulators

Battery-less active implantable devices are of interest because they offer longer life span and eliminate costly battery replacement surgical interventions. This is possible as a result of advances in inductive power transfer and development of power management circuits to maximize the overall power transfer and provide various voltage levels for multi-functional implantable devices. Rehabilitation therapy using optical stimulation of genetically modified peripheral neurons requires high current loads. Standard rectification topologies are inefficient and have associated voltage drops unsuited for miniaturized implants. This paper presents an integrated power management unit (PMU) for an optical-electrical stimulator to be used in the treatment of motor neurone disease. It includes a power-efficient regulating rectifier with a novel body biased high-speed comparator providing 3.3 V for the operation of the stimulator, a 3-stage latch-up charge pump with 12 V output for the input stage of the optical-electrical stimulator, and 1.8 V for digital control logic. The chip was fabricated in a 0.18 μm CMOS process. Measured results show that for a regulated output of 3.3 V delivering 30.3 mW power, the peak power conversion efficiency is 84.2% at 6.78 MHz inductive link tunable frequency reducing to 70.3% at 13.56 MHz. The charge pump with on chip capacitors has 90.9% measured voltage conversion efficiency

WIRELESS POWER MANAGEMENT CIRCUITS FOR BIOMEDICAL IMPLANTABLE SYSTEMS

Ph.DDOCTOR OF PHILOSOPH

Un nuevo rectificador reconfigurable CMOS para recolectores de energía piezoeléctrica en dispositivos portables

Los recolectores de energía para dispositivos portables tienen una aplicación potencial en la conversión de la energía del movimiento humano en energía eléctrica para alimentar dispositivos inteligentes de monitoreo de la salud, de la industria textil, así como de relojes y lentes inteligentes. Estos recolectores de energía requieren circuitos rectificadores óptimos que maximicen sus eficiencias de carga. En este estudio se presenta el diseño de un novedoso rectificador reconfigurable metal óxido semiconductor complementario (CMOS) para recolectores de energía piezoeléctrica portables que puede aumentar sus eficiencias de carga. El rectificador diseñado se basa en la tecnología de proceso CMOS estándar de 0,18 µm considerando un patrón geométrico con un área total de silicio de . El circuito rectificador propuesto tiene dos puertas de transmisión (TG) que están compuestas por cuatro transistores rectificadores con una carga de 45 kΩ, un voltaje mínimo de entrada de 500 mV y un voltaje máximo de 3,3 V. Los resultados de las simulaciones numéricas del funcionamiento del rectificador indican una eficiencia de conversión de voltaje del 99,4 % y una eficiencia de conversión de potencia de hasta el 63,3 %. El rectificador propuesto puede utilizarse para aumentar la eficiencia de carga de los recolectores de energía piezoeléctrica portables.Wearable energy harvesters have potential application in the conversion of human-motion energy into electrical energy to power smart health-monitoring devices, the textile industry, smartwatches, and glasses. These energy harvesters require optimal rectifier circuits that maximize their charging efficiencies. In this study, we present the design of a novel complementary metal-oxide semiconductor (CMOS) reconfigurable rectifier for wearable piezoelectric energy harvesters that can increase their charging efficiencies. The designed rectifier is based on standard 0.18 µm CMOS process technology considering a geometrical pattern with a total silicon area of 54.765 µm x 86.355 µm. The proposed rectifier circuit has two transmission gates (TG) that are composed of four rectifier transistors with a charge of 45 kΩ, a minimum input voltage of 500 mV and a maximum voltage of 3.3 V. Results of numerical simulations of the rectifier performance indicate a voltage conversion efficiency of 99.4% and a power conversion efficiency up to 63.3%. The proposed rectifier can be used to increase the charging efficiency of wearable piezoelectric energy harvesters

Mid-range transformer based wireless power transfer system for low power devices

Wireless power transfer technique for biomedical devices has drawn great interest from many researchers in the biomedical domain. Biomedical devices can be powered up either by an external power cord or by batteries. However an external power cord may limit the mobility of a patient and batteries tend to have a very limited power capacity and these methods may pose a high risk of infection towards the patient. Therefore, a wireless power transfer system is proposed to solve the problem. This study attempts to develop a mid-range transformer based wireless power transmission system which is suitable to power biomedical devices. This includes the develop of a transmitter circuit, receiver circuit, a pair of transmitter and receiver coils and transformers. This study demonstrates that magnetic coupling technique is a reliable wireless charging technique biomedical devices due to its mid-range transmission and satisfactory efficiency. In order to reduce power loss, an impedance matching method which incorporates a step-up and step-down transformers in the transmitter and receiver circuit is proposed. This study also develops a wireless power charging system that does not emit harmful radiation towards the human body. The frequency for the system is within the range of 700 kHz to 900 kHz which is in accordance to the ICNIRP regulation. Three pairs of round-shaped transmitter and receiver coils pair have been designed and fabricated with the diameter size of 30cm, 40cm, and 50cm. The power supply and frequency generator are connected to the transmitter circuit and an oscilloscope is connected to the load of the receiver circuit. The performance results are recorded using a range from 4 centimeters to 110 centimeters and based on the tabulated results, the mid-range wireless power transfer system managed to supply a transfer efficiency of 60% at a distance of 35cm for the 30cm diameter coil, 62% at a distance of 43cm for the 40cm diameter coil and 46% at a distance of 50cm for the 50cm diameter coil

Design of Power Management Integrated Circuits and High-Performance ADCs

A battery-powered system has widely expanded its applications to implantable medical devices (IMDs) and portable electronic devices. Since portable devices or IMDs operate in the energy-constrained environment, their low-power operations in combination with efficiently sourcing energy to them are key problems to extend device life. This research proposes novel circuit techniques for two essential functions of a power receiving unit (PRU) in the energy-constrained environment, which are power management and signal processing. The first part of this dissertation discusses power management integrated circuits for a PRU. From a power management perspective, the most critical two circuit blocks are a front-end rectifier and a battery charger. The front-end CMOS active rectifier converts transmitted AC power into DC power. High power conversion efficiency (PCE) is required to reduce power loss during the power transfer, and high voltage conversion ratio (VCR) is required for the rectifier to enable low-voltage operations. The proposed 13.56-MHz CMOS active rectifier presents low-power circuit techniques for comparators and controllers to reduce increasing power loss of an active diode with offset/delay calibration. It is implemented with 5-V devices of a 0.35 µm CMOS process to support high voltage. A peak PCE of 89.0%, a peak VCR of 90.1%, and a maximum output power of 126.7 mW are measured for 200Ω loading. The linear battery charger stores the converted DC power into a battery. Since even small power saving can be enough to run the low-power PRU, a battery charger with low IvQ is desirable. The presented battery charger is based on a single amplifier for regulation and the charging phase transition from the constant-current (CC) phase to the constant-voltage (CV) phase. The proposed unified amplifier is based on stacked differential pairs which share the bias current. Its current-steering property removes multiple amplifiers for regulation and the CC-CV transition, and achieves high unity-gain loop bandwidth for fast regulation. The charger with the maximum charging current of 25 mA is implemented in 0.35 µm CMOS. A peak charger efficiency of 94% and average charger efficiency of 88% are achieved with an 80-mAh Li-ion polymer battery. The second part of this dissertation focuses on analog-to-digital converters (ADCs). From a signal processing perspective, an ADC is one of the most important circuit blocks in the PRU. Hence, an energy-efficient ADC is essential in the energy-constrained environment. A pipelined successive approximation register (SAR) ADC has good energy efficiency in a design space of moderate-to-high speeds and resolutions. Process-Voltage-Temperature variations of a dynamic amplifier in the pipelined-SAR ADC is a key design issue. This research presents two dynamic amplifier architectures for temperature compensation. One is based on a voltage-to-time converter (VTC) and a time-to-voltage converter (TVC), and the other is based on a temperature-dependent common-mode detector. The former amplifier is adopted in a 13-bit 10-50 MS/s subranging pipelined-SAR ADC fabricated in 0.13-µm CMOS. The ADC can operate under the power supply voltage of 0.8-1.2 V. Figure-of-Merits (FoMs) of 4-11.3 fJ/conversion-step are achieved. The latter amplifier is also implemented in 0.13-µm CMOS, consuming 0.11 mW at 50 MS/s. Its measured gain variation is 2.1% across the temperature range of -20°C to 85 °C

Design and Development of a Wireless Lamp Charging System

Wireless is a technology of transmitting power through an air gap to electrical devices for the purpose of energy replenishment. The recent progress in wireless charging techniques and development of commercial products has provided a promising alternative way to address the energy tailback of unadventurously portable-power devices. This work is an innovative application of Faraday’s laws of electromagnetic induction. A charging station sends energy through inductive coupling to an electrical device, which stores the energy in the batteries. Because there is a small gap between the two coils, inductive charging is one kind of short-distance wireless energy transfer. Induction coils are attached to transmitter and the portable device, so that the device receives power from the electromagnetic field created by the transmitting unit and stores the energy in the battery

Procjena učinkovitosti mosnog MOSFET ispravljača za napajanje LED rasvjete korištenjem piezoelektričkog sustava za prikupljanje energije

Harvesting energy from the renewable energy sources plays a very important role in recent days. Researchers are using various methods to capture the energy for different sources. One of the most prominent methods of energy harvesting from vibrations is by using piezo-electric material. Piezo-electric vibration harvesting is smart mainly due to the simplicity of piezoelectric transduction and the piezoelectric systems can be easily implemented into a wide variety of applications. Due to wide range of AC output voltage and low power, the piezo-electric generator cannot directly prop up the AC or DC electrical appliances. Hence in the majority applications the AC signal created by this generator needs to be rectified. In this paper a new highly efficient MOSFET full bridge AC to DC converter for piezoelectric energy harvesting is planned, which enhances the power extracted from the piezo-electric crystal. The proposed AC to DC converter reduces the voltage drop along the conduction path and thereby increases the power extraction and conversion capability. The proposed circuit is replicated in PSpice software package and then in the experimental setup. The performance is evaluated and compared.Prikupljanje energije iz obnovljivih izvora odigralo je važnu ulogu u recentnoj povijesti. Istraživači danas koriste različite metode za prikupljanje različitih oblika energije. Jedna je od najistaknutijih metoda prikupljanje energije vibracijama korištenjem piezoelektričkih materijala. Ovaj način ističe se jednostavnošću piezoelektrične vodljivosti, a sustavi se mogu jednostavno implementirati u široki opseg primjena. Zbog širokog raspona AC izlaznog napona i male snage, piezoelektrički generator ne može se direktno spojiti na AC ili DC električne uređaje. Stoga je za većinu aplikacija AC signal ovakvog generatora potrebno ispraviti. U radu se prikazuje planiranje nove visoko-efikasne topologije punog mosnog spoja MOSFET-a AC/DC pretvarača za piezoelektričko prikupljanje energije, koje pojačava prikupljenu energiju iz piezoelektričnog kristala. Predloženi AC/DC pretvarač smanjuje propad napona duž puta vođenja i time povećava prikupljanje energije i sposobnost konverzije. Predloženi sklop izrađen je u PSpice programskom paketu, a zatim na eksperimentalnom postavu. Svojstva sklopa procijenjena su i uspoređena

High-Efficiency Low-Voltage Rectifiers for Power Scavenging Systems

Abstract Rectifiers are commonly used in electrical energy conversion chains to transform the energy obtained from an AC signal source to a DC level. Conventional bridge and gate cross-coupled rectifier topologies are not sufficiently power efficient, particularly when input amplitudes are low. Depending on their rectifying element, their power efficiency is constrained by either the forward-bias voltage drop of a diode or the threshold voltage of a diode-connected MOS transistor. Advanced passive rectifiers use threshold cancellation techniques to effectively reduce the threshold voltage of MOS diodes. Active rectifiers use active circuits to control the conduction angle of low-loss MOS switches. In this thesis, an active rectifier with a gate cross-coupled topology is proposed, which replaces the diode-connected MOS transistors of a conventional rectifier with low-loss MOS switches. Using the inherent characteristics of MOS transistors as comparators, dynamic biasing of the bulks of main switches and small pull-up transistors, the proposed self-supplied active rectifier exhibits smaller voltage drop across the main switches leading to a higher power efficiency compared to conventional rectifier structures for a wide range of operating frequencies in the MHz range. Delivery of high load currents is another feature of the proposed rectifier. Using the bootstrapping technique, single- and double-reservoir based rectifiers are proposed. They present higher power and voltage conversion efficiencies compared to conventional rectifier structures. With a source amplitude of 3.3 V, when compared to the gate cross-coupled topology, the proposed active rectifier offers power and voltage conversion efficiencies improved by up to 10% and 16% respectively. The proposed rectifier using the bootstrap technique, including double- and single-reservoir schemes, are well suited for very low input amplitudes. They present power and voltage conversion efficiencies of 75% and 76% at input amplitude of 1.0 V and maintain their high efficiencies over input amplitudes greater than 1.0V. Single-reservoir bootstrap rectifier also reduces die area by 70% compared to its double-reservoir counterpart.---------Résumé Les redresseurs sont couramment utilisés dans de nombreux systèmes afin de transformer l'énergie électrique obtenue à partir d'une source alternative en une alimentation continue. Les topologies traditionnelles telles que les ponts de diodes et les redresseurs se servant de transistors à grilles croisées-couplées ne sont pas suffisamment efficaces en terme d’énergie, en particulier pour des signaux à faibles amplitudes. Dépendamment de leur élément de redressement, leur efficacité en termes de consommation d’énergie est limitée soit par la chute de tension de polarisation directe d'une diode, soit par la tension de seuil du transistor MOS. Les redresseurs passifs avancés utilisent une technique de conception pour réduire la tension de seuil des diodes MOS. Les redresseurs actifs utilisent des circuits actifs pour contrôler l'angle de conduction des commutateurs MOS à faible perte. Dans cette thèse, nous avons proposé un redresseur actif avec une topologie en grille croisée-couplée. Elle utilise des commutateurs MOS à faible perte à la place des transistors MOS connectés en diode comme redresseurs. Le circuit proposé utilise: des caractéristiques intrinsèques des transistors MOS pour les montages comparateurs et une polarisation dynamique des substrats des commutateurs principaux supportés par de petits transistors de rappel. Le redresseur proposé présente des faibles chutes de tension à travers le commutateur principal menant à une efficacité de puissance plus élevée par rapport aux structures d’un redresseur conventionnel pour une large gamme de fréquences de fonctionnement de l’ordre des MHz. La conduction des courants de charge élevée est une autre caractéristique du redresseur proposé. En utilisant la méthode de bootstrap, des redresseurs à simple et à double réservoir sont proposés. Ils présentent une efficacité de puissance et un rapport de conversion de tension élevés en comparaison avec les structures des redresseurs conventionnels. Avec une amplitude de source de 3,3 V, le redresseur proposé offre des efficacités de puissance et de conversion de tension améliorées par rapport au circuit à transistors croisés couplés. Ces améliorations atteignent 10% et 16% respectivement. Les redresseurs proposés utilisent la technique de bootstrap. Ils sont bien adaptés pour des amplitudes d'entrée très basses. À une amplitude d'entrée de 1,0 V, ces derniers redresseurs présentent des rendements de conversion de puissance et de tension de 75% et 76%. Le redresseur à simple réservoir réduit également l’aire de silicium requise de 70% par rapport à la version à double-réservoir

A self-powered single-chip wireless sensor platform

Internet of things” require a large array of low-cost sensor nodes, wireless connectivity, low power operation and system intelligence. On the other hand, wireless biomedical implants demand additional specifications including small form factor, a choice of wireless operating frequencies within the window for minimum tissue loss and bio-compatibility This thesis describes a low power and low-cost internet of things system suitable for implant applications that is implemented in its entirety on a single standard CMOS chip with an area smaller than 0.5 mm2. The chip includes integrated sensors, ultra-low-power transceivers, and additional interface and digital control electronics while it does not require a battery or complex packaging schemes. It is powered through electromagnetic (EM) radiation using its on-chip miniature antenna that also assists with transmit and receive functions. The chip can operate at a short distance (a few centimeters) from an EM source that also serves as its wireless link. Design methodology, system simulation and optimization and early measurement results are presented