A miniaturized electromagnetic generator with planar coils and its energy harvest circuit

Lun Deliao Liao, Chang-Po Chao, Jian Ting Chen, Wei Dar Chen, Wei Hsuan Hsu, Chi Wei Chiu, Chin-Teng Lin

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31 Scopus citations


This study presents design, analysis and ex;periment of a miniaturized rotary generator in size of 10 × 10 × 2 mm3 and its compact energy harvest circuit chip. The designed generator consists of patterned planar copper coils and a multipolar hard magnet ring made of NdFeB. To perform modeling, a harmonic-like magnetic field model along the circumferential path of each magnetic pole is assumed with the assistance from measured peak magnetic flux densities. This is followed by the application of Faraday's law to predict generated electromotive forces (EMFs) in terms of the relative rotational speed between the magnet ring and coils. The genetic algorithm (GA) is next applied to optimize the critical dimensions of the miniaturized generator. The theoretical model of this power microgenerator is evaluated and compared with experimental results, and it is found that the analytical simulation shows a good agreement with the experimental results. The optimized generator offers 4.5 V and 7.23 mW in root mean square (rms) at 10 000 r/min. With microgenerator successfully fabricated, a novel energy harvest circuit employing Dickson charge pump is designed and fabricated via the 0.35-um process offered by National Chip Implementation Center (CIC) of Taiwan. This charge pump circuit owns the merit of almost-zero thresholds of employed metal-oxide-semiconductor (MOS) transistors, enabling the conversion of low-power alternating current (ac) signals by the microgenerator to direct current (dc) ones.

Original languageEnglish
Article number5257120
Pages (from-to)4621-4627
Number of pages7
JournalIEEE Transactions on Magnetics
Issue number10
StatePublished - 1 Oct 2009


  • Electromotive forces (EMFs)
  • Energy harvest circuit
  • Miniaturized rotary generator
  • Self-power system


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