A Self-Powered Synchronous Switch Energy Extraction Circuit for Electromagnetic Energy Harvesting Enhancement

Previous studies have shown that the synchronous switch energy extraction (SSEE) solutions could enhance the energy harvesting capability of vibration energy harvesters with capacitive output impedance, such as piezoelectric ones. These circuits use a synchronous switch inductive branch to compensate for the capacitive source. Some studies have also shown that an inductive source can be compensated by a synchronous switch capacitive branch. Yet, the controls were all carried out by external bulky and power-hungry controllers, which is unrealistic in a self-contained and self-sustainable system. This article proposes a self-powered SSEE (SP-SSEE) circuit for inductive electromagnetic energy harvesting sources. The sampling, synchronization, and switch control are implemented with a small series sampling inductor, a comparator, and some digital gates, respectively. The SSEE circuit carries out two rounds of the switch
on
/
off
actions in each vibration cycle to make the current through the induced equivalent voltage source in phase with its voltage. By improving the power factor of the induced voltage source, it enlarges the harvested power under the same excitation. It uses fewer switching actions than the conventional pulse-width modulation ac–dc rectifier designs. Moreover, the self-powered design makes the SSEE solution a passive ac–dc rectifier, which is more convenient to be utilized in real applications. The detailed working principle and experimental validation of the SP-SSEE circuit are provided in this article. The results show that, under the tested frequencies, SP-SSEE outperforms the benchmark standard energy harvesting diode-bridge rectifier by 62.1%–96.4% under different excitation frequencies, in terms of harvested power.