zhang-async11 - 2011 17th IEEE International Symposium on...

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A Novel Power Delivery Method for Asynchronous Loads in Energy Harvesting Systems Xuefu Zhang, Delong Shang, Fei Xia and Alex Yakovlev School of Electrical, Electronic & Computer Engineering Newcastle University upon Tyne Newcastle upon Tyne, United Kingdom {xuefu.zhang, delong.shang, fei.xia, alex.yakovlev}@ncl.ac.uk Abstract DC/DC conversion has been an integral part of the power delivery chain in energy harvesting systems because the conventionally targeted synchronous computation load demands stable Vdd, which cannot in general be supplied by power harvesters directly. However, asynchronous computation loads, in addition to their potential power-saving capabilities, can be made tolerant to a much wider range of Vdd variance. This may open up opportunities for much more energy efficient methods of power delivery to be adopted. This paper presents in-depth investigations into the behavior and performance of different power delivery methods driving both asynchronous and synchronous load for the first time. A novel power delivery method, which employs a capacitor bank for adaptively storing the energy from power harvesters depending on load and source conditions, is developed. Its advantages, especially when driving asynchronous loads, are demonstrated through comprehensive comparative analysis. Keywords-Switched Capacitor DC/DC converter; Capacitor Bank; Energy Harvesting; Piezoelectric Element. I. INTRODUCTION Energy Harvesting (EH) is becoming a more popular method of generating energy for computation systems, especially in the case of remote and mobile systems [1], with diverse energy conversion methods investigated [2]. EH and the reality that computation is becoming more energy-bounded are some of the inspirations for the concept of energy- modulated computing [3]. EH and other energy sources employed in energy-modulated computing systems can be fundamentally different from conventional power supply methods. For instance, in these systems the available energy may be viewed as infinite, with newer energy always available during system lifetimes but instantaneous power often unpredictable and nondeterministic, depending on the environment [3]. This has motivated various techniques in trying to smooth the power flow, including temporarily storing harvested energy in components such as rechargeable batteries and off-chip supercapacitors [4], which have a number of disadvantages [5]. Therefore, directly delivering energy generated by harvesters to the computational load might be an alternative in some applications [6]. In this work, we focus on the case where power from the EH device is directly delivered to the load on-chip without or bypassing off-chip storage, targeting extreme miniaturization for future applications.
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This note was uploaded on 11/28/2011 for the course COMP 790 taught by Professor Staff during the Fall '08 term at UNC.

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zhang-async11 - 2011 17th IEEE International Symposium on...

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