100 μW Coreless Flyback Converter for microbial fuel cells energy harvesting

摘要

The microbial fuel cells (MFCs) are emerging energy harvesters that are promising for the autonomous supply of seafloors remote sensors. Regarding the low voltage and power level delivered by MFC an electrical interface is required to condition the sensors needs. The flyback in discontinuous conduction mode appears to be the best candidate to extract the maximum power delivered by the MFC, to electrically isolate the sensor from the source and to boost the voltage to the one required by the energy buffering. Our work highlighted the significant impact of the magnetic core loss of coupled inductances on the power efficiency decrease, mainly due to the hysteresis and magnetic saturation even at μ-scale energy transfer. In this paper, we propose to remove the magnetic core to suppress these previously mentioned losses. The low density harvested power (100 μW for 10th cm~2 electrodes) and low-size constraint i.e. m~2-scale in seafloors remote sensors application allow to use 0.5 m~2 air-core inductance. By plugging a 20-cm~2 MFC delivering a maximum power of 90 μW at 0.3 V, the proposed air-core based flyback achieved 60% efficiency experimentally. This figure correctly matches simulations in which a model of the coreless coupled inductances, extracted from experimental characterizations, is used. This work is the first to validate the concept of a flyback with coreless coupled inductances harvesting 10th of μWs.