Open-loop power conditioning for vibration energy harvesters

Energy harvesters feature a high impedance output that complicates subsequent power conditioning because operation in the peak power region violates the stability criterion for converters with voltage regulation. By using a flyback converter in open-loop discontinuous mode and a shunt voltage regulator, it is demonstrated that a harvester can be operated in an optimal manner whilst ensuring stability. A circuit is described that draws the unity power factor from the harvester, provides output voltage regulation and consumes 180 muW of quiescent power.