Title page for etd-0913115-134153


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URN etd-0913115-134153
Author Rui-Hsiu Yu
Author's Email Address h1j41j41j4@yahoo.com.tw
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Department Electrical Engineering
Year 2015
Semester 1
Degree Master
Type of Document
Language English
Title A Piezoelectric Energy Harvester and MOS Floating Gate Memory towards Wearable Strain Metering
Date of Defense 2015-10-06
Page Count 71
Keyword
  • Energy Harvesting
  • Floating gate memory
  • Piezoelectric
  • Long-term wearable monitoring
  • Wearable circuits
  • Abstract With increasing levels of health awareness among people, the importance of long-term medical monitoring has increased along with the need for body detection at any given time and place. To serve these needs, wearable circuits, often in form of a body area network (BAN), are possible solutions. However, for long-term wearable monitoring the energy supply remains a critical issue. An energy harvesting circuit is studied in this thesis which extracts energy from a piezoelectric device. The device may eventually be energized by compression such as when worn under a shoe or by gravity oscillation when worn on the body. In this study a test circuit is built to measure the voltage rise on a storage capacitor in response to mechanically nudging the piezo device. The circuit is bench tested and compared with analytical results obtained for a model of this system showing close agreement. The harvested power is also measured. It depends on the actual strength and duration pattern of the piezoelectric compression. For the actual setup studied here, the harvested power is in the range of 1.46uW. Since this power is small, this study further investigates a potentially useful circuit that can be energized by the harvester. A candidate circuit is the MOS floating gate memory cell which is suitable to store an analog value corresponding to applied signal energy. A memory cell is realized in TSMC 0.35um integrated process technology with an active are of 136.375 µm*131.525 µm. Measured results are presented and show the response to a programming current. Erasure of the rewritable cell needs about 10 minutes using CMOS compatible voltage levels. According to the programmed voltage, an on-chip comparator can read the memory state and provide a binary logic output. Measurement shows that programming the cell with the energy of the piezoelectric device of this study enables battery-less piezo strain recording over a time period of about 100 minutes.
    Advisory Committee
  • Jia-Jin Chen - chair
  • Chung-Yao Kao - co-chair
  • Ing-Jer Huang - co-chair
  • Robert Rieger - advisor
  • Files
  • etd-0913115-134153.pdf
  • Indicate in-campus at 5 year and off-campus access at 5 year.
    Date of Submission 2015-10-13

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