Efficient low voltage direct AC/DC converters for self-powered wireless sensor nodes and mobile electronics

The conventional power electronics converters used in the microgenerator based energy harvesting applications have two stages: a diode bridge rectifier and a DC-DC converter. However, in the case of electromagnetic microgenerators, the diode bridge rectification is not normally feasible due to the extreme low output voltage of the microgenerators. Even if possible, the losses in the diode bridge rectifier make the conventional power electronic interfaces very inefficient. In this paper two direct ac-to-dc power electronics converter topologies are proposed for efficient and maximum energy harvesting from low voltage microgenerators. The proposed single stage converters directly boost the microgenerator low ac voltage to usable higher dc voltage, and hence, achieve higher efficiency. The single stage ac-to-dc power conversion is achieved by utilizing the bidirectional conduction capability of MOSFETs. Furthermore, with the proposed converters, the maximum energy harvesting can be successfully realized by controlling the effective load resistance offered to the microgenerators. The conventional power converters are not conducive for implementation of such control. Simulation and experimental results are presented for verification of the proposed converters.