Electric-Energy Generation through Variable-Capacitive Resonator for Power-Free LSI

Masayuki MIYAZAKI  Hidetoshi TANAKA  Goichi ONO  Tomohiro NAGANO  Norio OHKUBO  Takayuki KAWAHARA  

IEICE TRANSACTIONS on Electronics   Vol.E87-C   No.4   pp.549-555
Publication Date: 2004/04/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Low-Power System LSI, IP and Related Technologies)
vibration energy,  resonance,  variable capacitance,  power generation,  on-chip battery,  

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A vibration-to-electric energy converter as a power generator through a variable-resonating capacitor is theoretically and experimentally demonstrated as a potential on-chip battery. The converter is constructed from three components: a mechanical-variable capacitor, a charge-transporter circuit and a timing-capture control circuit. An optimum design methodology is theoretically described to maximize the efficiency of the vibration-to-electric energy conversion. The energy-conversion efficiency is analyzed based on the following three factors: the mechanical-energy to electric-energy conversion loss, the parasitic elements loss in the charge-transporter circuit and the timing error in the timing-capture circuit. Through the mechanical-energy conversion analysis, the optimum condition for the resonance is found. The parasitic elements in the charge-transporter circuit and the timing management of the capture circuit dominate the output energy efficiency. These analyses enable the optimum design of the energy-conversion system. The converter is fabricated experimentally. The practical measured power is 0.12 µW, and the conversion efficiency is 21%. This efficiency is calculated from a 43% mechanical-energy conversion loss and a 63% charge-transportation loss. The timing-capture circuit is manually controlled in this experiment, so that the timing error is not considered in the efficiency. From our result, a new system LSI application with an embedded power source can be explored for the ubiquitous computing world.