120% Harvesting Energy Improvement by Maximum Power Extracting Control for High Sustainability Magnetic Power Monitoring and Harvesting System

The magnetic energy harvesting (MEH) circuit and the power monitoring system are proposed in this paper to enlarge the system sustainability on wireless sensing or the monitoring system. The proposed MEH circuit harvests magnetic power on power wires through a power sensing current transformer (CT) and charges power monitoring system. The MEH circuit includes the direct ac-dc rectifier and the maximum power extracting (MPE) control circuit. The direct ac-dc rectifier can directly rectify ac input to the dc output current. The proposed MPE control fits the characteristic of magnetic energy source compared to the conventional resistor emulation maximum power point tracking method. Owing to continuous tracking the maximum power of the CT, 120% harvesting power improvement can be achieved under the same CT´s sensing current. Peak efficiency of 82% can be achieved under the sensing current of 8 A. The test chip is fabricated in 0.25 μm CMOS process with an active area of 0.98 mm².