Efficient direct ac-to-dc converters for vibration-based low voltage energy harvesting

In this paper two direct ac-to-dc power electronics converter topologies are proposed for efficient and optimum energy harvesting from low voltage microgenerators. The conventional power electronics converters used for such applications have two stages, a diode bridge rectifier at the front end followed by a dc-dc boost converter. However, the extremely low ouput voltage of electromagnetic microgenerators does not allow diode bridge rectification. Even if possible, the losses in the front end diode bridge make the conventional power electronic interfaces quite inefficient. The proposed single stage converters directly boost the microgenerator low ac voltage to usable dc voltage level, and hence, achieve higher efficiency. The single stage ac-to-dc power conversion is achieved by utilizing the bidirectional current conduction capability of MOSFETs. Moreover, for optimum energy harvesting the power converter should be able to control the load resistance as seen by a microgenerator. The conventional converters are not conducive for such control. With the proposed converter topologies the optimal energy harvesting can be successfully realized.