Vibration Energy Harvesting Circuit with Impedance Matching and Wake-up for Freight Railcars

This paper presents a circuit for vibration energy harvesting from freight railcars, and it aims to power wireless sensor nodes (WSNs). An electromagnetic generator (EMG) converts vibration energy of a fright railcar into electrical energy. The proposed circuit adopts impedance matching to extract maximum power from the EMG and a wake-up circuit to save power when the fright railcar is not moving. A buck-boost converter running in discontinuous conduction mode is used for impedance matching. When the railcar is in motion, the wake-up circuit senses the EMG voltage and activates the buck-boost converter. Otherwise, the converter is deactivated to save power. The proposed circuit generates two regulated output voltages, 1.8 V and 3.3 V, to power WSNs. It is prototyped with discrete components. Experimental results show that the EMG attached on a freight railcar generates 7.07 V rms and has the source impedance of 300 Ω. The proposed circuit harvests peak power of 28.4 mW delivered to the load and achieves the efficiency of 67.6%.