Mohammed Ismail

A Low-Power, High-Resolution ZCS Control for Inductor-Based Converters

This chapter presents an improved zero current switching (ZCS) control for high-gain inductor-based DC-DC converter targeting thermoelectric generator (TEG) for wearable electronics. The proposed ZCS control is an all-digital circuit that utilizes a simple finite state machine (FSM) and a 3-bit counter to locate the zero current point. In addition, an efficient push-pull circuit along with delay capacitance banks is used to tune the delay near the zero current point to reduce the estimated error. The proposed control circuit achieves 56 delay steps using 3 control bits while having a high resolution, which helps in maintaining the efficiency of the converter. The prototype chip is fabricated in 65 nm CMOS and occupies an area of less than 0.04 mm(^{2}). Measured results of the converter confirm 81(%) peak efficiency at 55 (upmu )W output power and 50 mV input voltage.

Self-Powered SoC Platform for Wearable Health Care

This chapter presents a top-level design of the first self-powered SoC platform that can predict, with high accuracy, ventricular arrhythmia before it occurs. The system provides a very high level of integration in a single chip of mainstream modules that are typically needed to build biomedical devices. Hence, the platform could help in reducing the cost in designing not only for ECG monitoring systems, but for generic low-power health care devices. The platform consists of a graphene-based sensors to acquire ECG signals, an analog front-end to amplify and digitize the ECG, a custom processor to perform feature extraction and classification, a wireless transmitter to send the data to a point of care, and an energy harvesting unit to power the whole system. The platform consumes very low power that can be completely powered by the thermal energy generated from the human body. The system is imagined to be integrated within a necklace which can be worn by a patient comfortably. Hence, it can provide a continuous monitoring of the patient’s condition and connect him directly to his doctor for immediate attention if necessary.

Introduction to Ultra-Low Power ECG Processor

This chapter introduces the book. It gives the main highlights about motivation, objectives, and challenges for ultra-low power ECG processors.

Reconfigurable, Switched-Capacitor Power Converter for IoT

This chapter introduces an efficient reconfigurable, multiple voltage gain switched-capacitor DC–DC buck converter as part of a power management unit for wearable IoTs. The switched-capacitor converter has an input voltage of 0.6–1.2 V generated from an energy harvesting source. The switched-capacitor converter utilizes pulse frequency modulation to generate multiple regulated output voltage levels, namely 1, 0.8 and 0.6 V based on two reconfigurable bits over a wide range of load currents from 10 (upmu )A to 800 (upmu )A. The switched-capacitor converter is designed and fabricated in 65 nm low-power CMOS technology and occupies an area of 0.493 mm(^2). The design utilizes a stack of MIM and MOS capacitances to optimize the circuit area and efficiency. The measured peak efficiency is 80(%) at a load current of 800 (upmu )A and regulated load voltage of 1 V.

ACLT-Based QRS Detection and ECG Compression Architecture

In this chapter, a QRS detection architecture based on absolute value curve length transform is presented. Ultra-low power and optimized architectures are crucial for IoT devices. Moreover, optimized ECG processing architectures with an adequate level of accuracy is a necessity for IoT medical wearable devices. This chapter presents a real-time QRS detector and ECG compression architecture for energy constrained IoT healthcare wearable devices. The implementation of the proposed architectures requires adders, shifters, and comparators only, and removes the need for any multipliers. QRS detections are accomplished by using adaptive thresholds in the ACLT-transformed ECG-signal. The proposed QRS detector achieved a sensitivity of 99.37% and a predictivity of 99.38% when validated using databases acquired from Physionet. Furthermore, a lossless compression technique was incorporated into the proposed architecture that uses the ECG signal first derivative and variable-bit-length encoding. An average compression ratio of 2.05 was achieved when evaluated using the MIT-BIH database. The proposed QRS architecture was implemented using a 65 nm GF low-power process, it consumed an ultra-low power of 6.5 nW when operated at a supply of 1 V and at a frequency of 250 Hz.

Interface Circuits for Thermoelectric Generator

In this chapter, recent work is presented on different interface circuits for TEG energy harvesting systems. Further, the inductor-based boost converter is introduced as the main interface circuit for TEG harvesting systems. After that, different digital control circuits are explored for inductor-based boost converter. This includes zero current control, TEG polarity circuits, maximum power point tracking methods, and startup circuits.

Energy Combiner and Power Manager for Multi-Source Energy Harvesting

In this chapter, recent work in multi-source energy harvesting system is compared. This includes different energy combining techniques used to deliver the energy from multiple energy harvesting sources to the load. In addition, the design of an efficient energy combiner is proposed with power manager to form a complete energy harvesting system. Furthermore, a sleep mode operation for low power processor is explained which is necessary when the input energy is variable.

Polarity Mechanism for Thermoelectric Harvester

In this chapter, polarity circuits for thermoelectric generator are demonstrated. These circuits are important since it monitors the polarity status of the TEG voltage and flips it when a negative voltage is encountered. Several auto-polarity circuits are reported in the literature which are explained and compared. A novel technique is proposed and supported by measurement results. This technique is simple yet effective, fully integrated on chip, all digital with low overhead.

Energy Harvesting Sources, Models, and Circuits

In this chapter, common energy harvesting sources are discussed, namely thermoelectric generators, piezoelectric harvester, RF harvesting, and solar. The operating principle of each energy source is explained in detail, along with the electrical model for each which is essential for designing the interface circuits. Further, different power conversion circuits are presented that are commonly used in energy harvesting application. This includes linear drop out regulator, switch capacitor circuits, and inductor-based converters.

Zero Crossing Switching Control for L-Based DC–DC Converters

In this chapter, ZCS control techniques for inductor-based boost converters are presented. The ZCS circuit controls the high side switch of the synchronous inductor converter to maintain the output voltage and hence the efficiency. In the first section, several reported ZCS techniques are explained and compared in regard to design, complexity, and efficiency. Then, an example of an efficient ZCS method is introduced which is designed to enhance the dynamics of the inductor converter as well as the efficiency. Measurement results are presented which confirm the operation of the ZCS circuit.