Enhanced Maximum Power Point Reaching Method for Passive Magnetic Energy Harvesters Operating Under Low Primary Currents

The letter concerns a clamped-type passive magnetic energy harvester (MEH), supplying power to a general load via a diode bridge rectifier (DBR). It is known that a certain value of output MEH voltage (referred to as optimal) maximizes harvested power. Under high primary current magnitudes, the optimal voltage value is constant, i.e., current-independent. Consequently, it was recently proposed to interface a passive MEH to a general load via a switching power converter whose input (i.e., MEH-side) voltage is regulated to a corresponding constant voltage reference, realizing the maximum power point reaching (MPPR) method. However, optimal voltage value becomes current-dependent under low primary current magnitudes. As a result, the power harvested by MPPR-operated MEH becomes suboptimal if the MEH-side voltage reference of the converter remains unchanged. Hence, the brief suggests allowing the converter input voltage reference value to be adjusted (by, e.g., a maximum power point tracking loop) to maximize harvested MEH power under low primary currents as well. Experimental results comparing the harvested power of a passive MEH under classical and enhanced MPPR methods validate the proposed enhancement.