A Multiinput Bridgeless Resonant AC-DC Converter for Electromagnetic Energy Harvesting

Flapping electromagnetic-reed generators are investigated to harvest wind energy, even at low cutoff wind speeds. Power electronic interfaces are intended to address ac-dc conversion and power conditioning for single-or multiple-channel systems. However, the generated voltage of each generator reed at low wind speed is usually below the threshold voltage of power electronic semiconductor devices, increasing the difficulty and inefficiency of rectification, particularly at relatively low output powers. This paper proposes a multiinput bridgeless resonant ac-dc converter to achieve ac-dc conversion, step-up voltage and match optimal impedance for a multichannel electromagnetic energy harvesting system. Alternating voltage of each generator is stepped up through the switching LC network and then rectified by a freewheeling diode. Its resonant operation enhances efficiency and enables miniaturization through high frequency switching. The optimal electrical impedance can be adjusted through resonance impedance matching and pulse-frequency-modulation control. A 5 cm x 3 cm, six-input standalone prototype is fabricated to address power conditioning for a six-channel wind panel.