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Converter and method for extracting maximum power from piezo vibration harvester

  • US 8,674,663 B2
  • Filed: 03/19/2010
  • Issued: 03/18/2014
  • Est. Priority Date: 03/19/2010
  • Status: Active Grant
First Claim
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1. A system for efficiently transferring harvested vibration energy to an energy storage device including:

  • (a) piezo harvester means for receiving vibration energy and generating an AC output voltage and an AC output current that together constitute the harvested vibration energy;

    (b) means for coupling the AC output voltage and AC output current to active rectifier means for rectifying the AC output voltage and AC output current to produce a harvested DC output voltage and a harvested DC output current;

    (c) means for conducting the harvested DC output current into a capacitance to charge the capacitance until the harvested DC output voltage reaches a level at which a direction of the AC output current reverses;

    (d) means for detecting the direction reversal;

    (e) means for enabling a DC-DC converter in response to the detecting to cause discharging of the capacitance into an inductor of the DC-DC converter in response to the direction reversal; and

    (f) means for disabling the DC-DC converter in response to a comparison of the harvested DC output voltage with a reference voltage wherein the harvested DC output voltage is less than the reference voltage,wherein the means for coupling comprise an active rectifier including first and second switches coupled in series between a harvester output conductor and a first reference voltage, third and fourth switches coupled in series between the harvester output conductor and the first reference voltage, a first comparator for controlling the third and fourth switches, and a second comparator for controlling the first and second switches, a first terminal of the piezo harvester being coupled to a junction between the first and second switches and a first input of the first comparator, and a second terminal of the piezo harvester being coupled to a junction between the third and fourth switches and a first input of the second comparator, wherein the first and second comparators control the rectifying of the harvester output current to charge a capacitance coupled between the harvester output conductor and the first reference voltage, and wherein the first and second comparators also generate output signals indicative of direction reversals of the output current of the piezo harvester.

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