Energy-Efficient Circuits and Systems for Powering, Sensing and Actuating the Motions in Internet of Things

The Internet-of-Things (IoT) has long been considered the next major computing class that has significant societal benefits on people’s lives. With the miniaturization of the sensor nodes, the acquisition and analysis of data can be achieved in a broader range of environments, enabling applications such as precision healthcare, smart buildings, intelligent agriculture, and more. Motions are ubiquitous in these applications and can be utilized as an energy source to mitigate the power constraints associated with the sensor node scaling. Besides, many sensor nodes also acquire motion signals to reveal the information from the ambience, and some may even actively produce motions to achieve a more complex interaction with the environment (e.g., micro-robot). This thesis introduces three major topics on low-power circuit and system designs for IoTs related to motions. The first topic is to harvest kinetic energy from motions with piezoelectric energy harvesters (PEHs). To address the challenges in the impedance matching to PEHs, we present a sense-and-set (SaS) circuit that achieves the optimal energy extraction from the transducer and adapts to environmental variations. The SaS circuit is implemented with a single chip design, achieving a 5× power improvement in energy harvesting under periodic and random vibrations. The second topic is about sensing motions with ultra-low power MEMS capacitive accelerometers. To improve the critical trade-off between power and noise in MEMS accelerometers, we present a high-voltage biasing technique that significantly increase the MEMS sensing signal while maintaining mechanical stability with a novel technique called electrostatic mismatch compensation. The proposed accelerometer is implemented with 1 MEMS and 2 CMOS ICs, showing a 15× power-noise improvement over the prior state of the art. The third topic is about generating motions with micro-robot design to achieve the Programmable Matter (PM) that can be configured into any arbitrary 3-D shapes with a program. The motion generation is achieved by the high-voltage electrostatic actuation, and we present a high-voltage generation and multiplexing (HVGM) chip to enable a 100V actuation with 200nW range power. We further integrate HVGM with several other ICs into a complete bare-die system that is placed in each PM unit, and controls its communication, computation, powering and actuation in a PM system. A second version controller is also proposed and implemented to be fully integrated on-chip but maintains the multi-functions that enables an intelligent PM system.PHDElectrical and Computer EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/175666/1/pyimai_1.pd

27.2 An Adiabatic Sense and Set Rectifier for Improved Maximum-Power-Point Tracking in Piezoelectric Harvesting with 541% Energy Extraction Gain

Piezoelectric energy harvesters (PEHs) convert mechanical energy from vibrations into electrical energy. They have become popular in energy-autonomous IoT systems. However, the total energy extracted by a PEH is highly sensitive to matching between the PEH impedance and the energy extraction circuit. Prior solutions include the use of a full-bridge rectifier (FBR) and a so-called synchronous electric-charge extraction (SECE) [1], and are suitable for non-periodic vibrations. However, their extraction efficiency is low since the large internal capacitance C p (usually 10's of nF) of the PEH (Fig. 27.2.1) prevents the output voltage from reaching its maximum power point (MPP) under a typical sinusoidal and transient excitation (V MPP = 1/2·I p R p ). A recently proposed technique [2,3,4], called bias-flip, achieves a higher extraction efficiency by forcing a predetermined constant voltage at the PEH output, V p , which is then flipped every half-period of the assumed sinusoidal excitation (Fig. 27.2.1, top left). To flip V p , the energy in capacitor C p is extracted using either a large external inductor [2,3] or capacitor arrays [4]. It is then restored with the opposite polarity (Fig. 27.2.1, top). However, V MPP of the PEH varies with sinusoidal current I p ; hence, the two fixed values of V p in the flip-bias technique either over or underestimate V MPP for much of the oscillation cycle (pattern filled regions in Fig. 27.2.1, top right). In addition, none of the prior approaches compensate for V MPP -waveform amplitude changes, due to input intensity variations or decaying oscillations after an impulse, further degrading efficiency

A 286nW, 103V High Voltage Generator and Multiplexer for Electrostatic Actuation in Programmable Matter

International audienceWe present a high-voltage-generation-and-multiplexing (HVGM) chip, specifically designed for electrostatic actuation of micro-robots. It can individually control 12 pairs of +/- electrodes using a positive and negative charge pump and mux-structure, consumes 286nW in steady state and 533nW when transitioning a 10pF electrode at 155V/s, and produces a differential voltage of 103V (29× voltage gain from 3.6V) in measurement. We also show a complete microsystem of stacked die, measuring 3×1.4×1.1mm, including HVGM, processor, radio, and harvester for energy autonomous operation

An Efficient Piezoelectric Energy Harvesting Interface Circuit Using a Sense-and-Set Rectifier

Piezoelectric energy harvesters (PEHs) are widely deployed in many self-sustaining systems, and proper rectifier circuits can significantly improve the energy conversion efficiency and, thus, increase the harvested energy. Various active rectifiers have been proposed in the past decade, such as synchronized switch harvesting on inductor (SSHI) and synchronous electric charge extraction (SECE). This article presents a sense-andset (SaS) rectifier that achieves maximum-power-point-tracking (MPPT) of PEHs and maintains optimal energy extraction for different input excitation levels and output voltages. The proposed circuit is fabricated in the 0.18-μm CMOS process with a 0.47-mm 2 core area, a 230-nW active power, and a 7-nW leakage power. Measured with a commercial PEH device (Mide PPA-1022) at 85and 60-Hz vibration frequency, the proposed circuit shows 512% and 541% power extraction improvement [figure of merit (FoM)] compared with an ideal full-bridge rectifier (FBR) for ON-resonance and OFF-resonance vibrations, respectively, while maintaining high efficiency across different input levels and PEH parameters.MSIC-LA