Efficient Low Power Headphone Driver

In recent years, the consumer electronics market for battery-powered devices such as smartphones and tablets has been rapidly expanding. The requirements for audio CODEC in these portable devices have extended from merely supporting voice calls to high-fidelity music playback. As a result, audio driver performance has become one of the most important differentiating factors among products from different suppliers. There are three basic performance metrics that are typically used to benchmark audio modules: the maximum delivered output power, the audio fidelity measured in terms of dynamic range, THD+N, and finally the battery life. Maximizing all three of these performance metrics has proven to be an exceptionally hard task as portrayed by the research publications.This work presents an attempt to push all three of these metrics together and provide an acceptable balance which is achieved by selecting the right topology. Conventionally, headphone drivers are designed using a linear amplifier topology for many reasons- most prominently- to achieve a superior THD+N and PSRR requirement which in the past was essentially the only key performance metric needed. This came at the expense of realizing mediocre power efficiency targets, thereby wasting battery life. This picture changed dramatically over the last decade with smartphones and other portable devices becoming the first choice of the young generation. These devices are extremely power hungry due to the unlimited functions and features they provide and therefore battery life has come to the spotlight as a key resource that need to be preserved. As a result, in this work a headphone driver is based on a switching topology that is able to deliver more than 230mW of power (or equivalently 2Vrms) to a 16Ω load while achieving better than -98dB of THD+N , more than 108dB of SNR, and about 108dB PSRR while still maintaining a peak power efficiency of more than 84%

Smartphone based ubiquitous sensing platform leveraging audio jack for power and communication

With the popularization of smartphones, various smartphone centric ubiquitous sensing applications, which use a smartphone in conjunction with external sensors for data acquisition, processing, display, communication, and storage, have emerged. Because smartphones do not have a universal data interfaces, many ubiquitous sensing applications use the earphone and the microphone channels of the 3.5mm audio interface for data communications so that they can work with various types of smartphones. The earphone channels of the 3.5mm audio interface can only send AC signal out of a smartphone, hence DC power needs to be harvested from the earphone channels. In this research, based on frequency shift keying (FSK) modulation scheme, we have proposed a joint power harvesting and communication technology that can simultaneously harvest power and transfer data using the same earphone channels. The joint power harvesting and communication technology is demonstrated with a prototype system, which can power an external microcontroller and sensors through the 3.5mm audio interface of a smartphone, display sensor measurement results on a smartphone, and control the outputs of the microcontroller from a smartphone. The newly proposed smartphone sensing platform is expected to harvest double or more power from both earphone channels in comparison to single channel harvesting designs and hence has the potential to support more smartphone powered sensing applications. Furthermore, the sensing platform is expected to support a reliable communication with much higher data rate from a smartphone to external sensors than existing designs

Design and Analysis of a Dual Supply Class H Audio Amplifier

abstract: Efficiency of components is an ever increasing area of importance to portable applications, where a finite battery means finite operating time. Higher efficiency devices need to be designed that don't compromise on the performance that the consumer has come to expect. Class D amplifiers deliver on the goal of increased efficiency, but at the cost of distortion. Class AB amplifiers have low efficiency, but high linearity. By modulating the supply voltage of a Class AB amplifier to make a Class H amplifier, the efficiency can increase while still maintaining the Class AB level of linearity. A 92dB Power Supply Rejection Ratio (PSRR) Class AB amplifier and a Class H amplifier were designed in a 0.24um process for portable audio applications. Using a multiphase buck converter increased the efficiency of the Class H amplifier while still maintaining a fast response time to respond to audio frequencies. The Class H amplifier had an efficiency above the Class AB amplifier by 5-7% from 5-30mW of output power without affecting the total harmonic distortion (THD) at the design specifications. The Class H amplifier design met all design specifications and showed performance comparable to the designed Class AB amplifier across 1kHz-20kHz and 0.01mW-30mW. The Class H design was able to output 30mW into 16Ohms without any increase in THD. This design shows that Class H amplifiers merit more research into their potential for increasing efficiency of audio amplifiers and that even simple designs can give significant increases in efficiency without compromising linearity.Dissertation/ThesisM.S. Electrical Engineering 201

Low Power High Efficiency Integrated Class-D Amplifier Circuits for Mobile Devices

The consumer’s demand for state-of-the-art multimedia devices such as smart phones and tablet computers has forced manufacturers to provide more system features to compete for a larger portion of the market share. The added features increase the power consumption and heat dissipation of integrated circuits, depleting the battery charge faster. Therefore, low-power high-efficiency circuits, such as the class-D audio amplifier, are needed to reduce heat dissipation and extend battery life in mobile devices. This dissertation focuses on new design techniques to create high performance class-D audio amplifiers that have low power consumption and occupy less space. The first part of this dissertation introduces the research motivation and fundamentals of audio amplification. The loudspeaker’s operation and main audio performance metrics are examined to explain the limitations in the amplification process. Moreover, the operating principle and design procedure of the main class-D amplifier architectures are reviewed to provide the performance tradeoffs involved. The second part of this dissertation presents two new circuit designs to improve the audio performance, power consumption, and efficiency of standard class-D audio amplifiers. The first work proposes a feed-forward power-supply noise cancellation technique for single-ended class-D amplifier architectures to improve the power-supply rejection ratio across the entire audio frequency range. The design methodology, implementation, and tradeoffs of the proposed technique are clearly delineated to demonstrate its simplicity and effectiveness. The second work introduces a new class-D output stage design for piezoelectric speakers. The proposed design uses stacked-cascode thick-oxide CMOS transistors at the output stage that makes possible to handle high voltages in a low voltage standard CMOS technology. The design tradeoffs in efficiency, linearity, and electromagnetic interference are discussed. Finally, the open problems in audio amplification for mobile devices are discussed to delineate the possible future work to improve the performance of class-D amplifiers. For all the presented works, proof-of-concept prototypes are fabricated, and the measured results are used to verify the correct operation of the proposed solutions

High efficiency delta-sigma modulation data converters

Enabled by continued device scaling in CMOS technology, more and more functions that were previously realized in separate chips are getting integrated on a single chip nowadays. Integration on silicon has opened the door to new portable wireless applications, and initiated a widespread use of these devices in our common everyday life. Wide signal bandwidth, high linearity and dynamic range, and low power dissipation are required of embedded data converters that are the performance-limiting key building blocks of those systems. Thus, power-efficient and highly-linear data conversion over wide range of signal bands is essential to get the full benefits from device scaling. This continued trend keeps innovation in the design of data converter continuing. Traditionally, delta-sigma modulation data converters proved to be very effective in applications where high resolution was necessary in a relatively narrow signal band. There have been active research efforts across academia and industry on the extension of achievable signal bandwidth without compromising the performance of these data converters. In this dissertation, architectural innovations, combined with effective design techniques for delta-sigma modulation data converters, are presented to overcome the associated limitations. The effectiveness of the proposed approaches is demonstrated by test results for the following state-of-the-art prototype designs: (1) a 0.8 V, 2.6 mW, 88 dB dual-channel audio delta-sigma modulation D/A converter with headphone driver; (2) an 88 dB ring-coupled delta-sigma ADC with 1.9 MHz bandwidth and -102.4 dB THD; (3) a multi-cell noise-coupled delta-sigma ADC with 1.9 MHz bandwidth, 88 dB DR, and -98 dB THD; (4) an 8.1 mW, 82 dB self-coupled delta-sigma ADC with 1.9 MHz bandwidth and -97 dB THD; (5) a noise-coupled time-interleaved delta-sigma ADC with 4.2 MHz bandwidth, -98 dB THD, and 79 dB SNDR; (6) a noise-coupled time-interleaved delta-sigma ADC with 2.5 MHz bandwidth, -104 dB THD, and 81 dB SNDR. As an extension of this research, two novel architectures for efficient double-sampling delta-sigma ADCs and improved low-distortion delta-sigma ADC are proposed, and validated by extensive simulations.Keywords: improved low-distortion modulator, time interleaving, data converter, multi-cell ADC, efficient double sampling, noise coupling, delta-sigma modulatio

Smart Devices and Systems for Wearable Applications

Wearable technologies need a smooth and unobtrusive integration of electronics and smart materials into textiles. The integration of sensors, actuators and computing technologies able to sense, react and adapt to external stimuli, is the expression of a new generation of wearable devices. The vision of wearable computing describes a system made by embedded, low power and wireless electronics coupled with smart and reliable sensors - as an integrated part of textile structure or directly in contact with the human body. Therefore, such system must maintain its sensing capabilities under the demand of normal clothing or textile substrate, which can impose severe mechanical deformation to the underlying garment/substrate. The objective of this thesis is to introduce a novel technological contribution for the next generation of wearable devices adopting a multidisciplinary approach in which knowledge of circuit design with Ultra-Wide Band and Bluetooth Low Energy technology, realization of smart piezoresistive / piezocapacitive and electro-active material, electro-mechanical characterization, design of read-out circuits and system integration find a fundamental and necessary synergy. The context and the results presented in this thesis follow an “applications driven” method in terms of wearable technology. A proof of concept has been designed and developed for each addressed issue. The solutions proposed are aimed to demonstrate the integration of a touch/pressure sensor into a fabric for space debris detection (CApture DEorbiting Target project), the effectiveness of the Ultra-Wide Band technology as an ultra-low power data transmission option compared with well known Bluetooth (IR-UWB data transmission project) and to solve issues concerning human proximity estimation (IR-UWB Face-to-Face Interaction and Proximity Sensor), wearable actuator for medical applications (EAPtics project) and aerospace physiology countermeasure (Gravity Loading Countermeasure Skinsuit project)

Development of an Underground Mine Scout Robot

Despite increased safety and improved technology in the mining industry, fatal disasters still occur. Robots have the potential to be an invaluable resource for search and rescue teams to scout dangerous or difficult situations. Existing underground mine search and rescue robots have demonstrated limited success. Identified through literature, the two primary concerns are unreliable locomotion systems and a lack of underground mine environment consideration. HADES, an underground mine disaster scout, addresses these issues with a unique chassis and novel locomotion. A system level design is carried out, addressing the difficulties of underground mine environments. To operate in an explosive atmosphere, a purge and pressurisation system is applied to a fibre glass chassis, with intrinsic safety incorporated into the sensor design. To prevent dust, dirt and water damaging the electronics, ingress protection is applied through sealing. The chassis is invertible, with a low centre of gravity and a roll-axis pivot. This chassis design, in combination with spoked-wheels allows traversal of the debris and rubble of a disaster site. Electrochemical gas sensors are incorporated, along with RGB-D cameras, two-way audio and various other environment sensors. A communication system combining a tether and mesh network is designed, with wireless nodes to increase wireless range and reliability. Electronic hardware and software control are implemented to produce an operational scout robot. HADES is 0.7 × 0.6 × 0.4 m, with a sealed IP65 chassis. The locomotion system is robust and effective, able to traverse most debris and rubble, as tested on the university grounds and at a clean landfill. Bottoming out is the only problem encountered, but can be avoided by approaching obstacles correctly. The motor drive system is able to drive HADES at walking speed (1.4 m/s) and it provides more torque than traction allows. Six Lithium-Polymer batteries enable 2 hours 28 minutes of continuous operation. At 20 kg and ~$7000, HADES is a portable, inexpensive scout robot for underground mine disasters

IoT Applications Computing

The evolution of emerging and innovative technologies based on Industry 4.0 concepts are transforming society and industry into a fully digitized and networked globe. Sensing, communications, and computing embedded with ambient intelligence are at the heart of the Internet of Things (IoT), the Industrial Internet of Things (IIoT), and Industry 4.0 technologies with expanding applications in manufacturing, transportation, health, building automation, agriculture, and the environment. It is expected that the emerging technology clusters of ambient intelligence computing will not only transform modern industry but also advance societal health and wellness, as well as and make the environment more sustainable. This book uses an interdisciplinary approach to explain the complex issue of scientific and technological innovations largely based on intelligent computing