Vibration-Based Energy-Harvesting Integrated Circuits

Abstract

Wireless microsensors that monitor and detect activity in factories, farms, military camps, vehicles, hospitals, and the human body can save money, energy, and lives. Unfortunately, miniaturized batteries exhaust easily, so deploying these tiny devices outside a few niche markets is difficult. Luckily, harnessing ambient energy, especially of the kinetic kind, offers hope because environmental motion is often abundant and consistent. The challenge is that tiny transducers convert only a small fraction of the available energy into the electrical domain, and the circuits that transfer and condition power dissipate some if not most of that energy. As a result, increasing the power drawn from the transducer and reducing the energy losses in the system are of paramount importance. This chapter therefore begins by evaluating how circuits transfer and consume power. Then, because electrostatic and piezoelectric transducers normally derive considerably more power per unit volume than their electromagnetic counterparts, the chapter focuses on how the former two technologies harness ambient kinetic energy. The ensuing discussion details how transducers, integrated circuits, and sample prototype integrated-circuit (IC) implementations of these circuits draw energy from ambient vibration to generate power with which to continually replenish a small on-board battery.