Self-Powered Smart Devices: Storage-Less and Converter-Less Maximum Power Point Tracking and SmartPatch

Speaker : Prof. Naehyuck Chang

(Korea Advanced Institute of Science and Technology)

Date : 2018/08/14 (Tue.)

Time : 14:00

Location :R525, Delta Bldg.  

Host : Prof. Tsung-Yi Ho

Abstract

Scavenging energy from photovoltaic (PV) cells is one of the most practical solutions for self-powered smart devices, in terms of power density among existing energy harvesting sources. PV power systems mandate the maximum power point tracking (MPPT) to scavenge the maximum possible solar energy. In general, a switching-mode power converter, an MPPT charger, controls the charging current to the energy storage element (a battery or equivalent), and the energy storage element provides power to the load device. The mismatch between the maximum power point (MPP) current and the load current is managed by the energy storage element.

However, such architecture causes significant energy loss (typically over 20%) and a significant weight/volume and a high cost due to the cascaded power converters and the energy storage element. This talk introduces a pioneering solar energy harvesting: a storage-less and converter-less PV power system with the MPPT that directly supplies power to the load without the power converters or the energy storage element. The proposed system uses an extremely fine-grain dynamic power management in a few hundred microseconds and makes it possible to match the load current with the MPP current. We present detailed modeling, simulation, and optimization of the proposed energy harvesting system including the radio frequency transceiver. Experiments show that the proposed setup achieves an 87.1% of overall system efficiency during a day, 30.6% higher than the conventional MPPT methods in actual measurements, and thus a significantly higher duty cycle under a weak solar irradiance.

As a well-matched application to a smart device, this talk also introduce a SmartPatch for cumulative UV irradiance. Caring ultraviolet irradiation is very important for human because it affects human body positively and negatively at the same time. In this talk, we introduce SmartPatch, a patchable and self-powered smart UV level meter supported by the two key technologies; storage-less and converter-less energy harvesting and switch-less interface. Unlike existing UV level meters, SmartPatch provides more scientific measures to avoid skin damages with extremely low-cost solution, and can efficiently cooperate with various Sun protection factor (SPF) sunscreen lotions and skin types which are varying on each person.

Biography

Naehyuck Chang is a Full Professor at the Department of Electrical Engineering, KAIST (Korea Advanced Institute of Science and Technology) from 2014. Before he joined KAIST, he was with the Department of Computer Science and Engineering, Seoul National University from 1997 to 2014. Dr. Chang also served as a Vice Dean of College of Engineering, Seoul National University from 2011 to 2013. His current research interests include low-power embedded systems and Design Automation of Things such as systematic design and optimization of Cyber-Physical Systems.

Dr. Chang is an ACM Fellow and an IEEE Fellow for contribution to low-power systems. He was the Chair of the ACM SIGDA (Special Interest Group on Design Automation) and now the Past Chair of ACM SIGDA. Dr. Chang is the Editor-in-Chief of the ACM (Association for Computing Machinery) Transactions on Design Automation of Electronics Systems, and an Associate Editor of IEEE Transactions on Very Large Scale Integration Systems. He also served for IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, IEEE Embedded Systems Letters, ACM Transactions on Embedded Computing Systems, and so on, as an Associate Editor.

Dr. Chang is (was) the General Co-Chair of VLSI-SoC (Very Large Scale Integration) 2015, ICCD (International Conference on Computer Design) 2014 and 2015, ISLPED (International Symposium on Low-Power Electronics and Design) 2011, etc. Dr. Chang is the Technical Program Chair of DAC (Design Automation Conference) 2016. He was the Technical Program (Co-)Chair of ASP-DAC (Asia and South Pacific Design Automation Conference) 2015, ICCD 2014, CODES+ISSS (Hardware Software Codesign and System Synthesis) 2012, ISLPED 2009, etc.

Dr. Chang is the winner of the 2014 ISLPED Best Paper Award, 2011 SAE Vincent Bendix Automotive Electronics Engineering Award, 2011 Sinyang Academic Award, 2009 IEEE SSCS International SoC Design Conference Seoul Chapter Award, and several ISLPED Low-Power Design Contest Awards in 2002, 2003, 2004, 2007, 2012, 2014, and 2017.

Dr. Chang and his colleague introduced the world’s first extreme off-road electric Jeep Wrangler and recently finished the Rubicon Trail run for the first time in the history by an electric Jeep Wrangler with just a single recharging at the Rubicon Springs Basecamp. Dr. Chang is a co-founder of EMVcon, Inc. ( www.emvcon.com .)