A low power impedance matching PWM generator for long distance energy harvesting from overhead power transmission lines

Energy harvesting from the magnetic field around overhead power lines is an effective approach to supply power for sensor nodes used for measuring weather conditions and power line monitoring. Due to the low intensity of the magnetic field at far distances from the overhead line, the power extracted by the energy harvester coil in this method is low and in the order of a few hundred mu Ws. Thus, it is necessary to use interface circuits including AC-DC voltage converters and power management circuits with low power consumption and high efficiency. In this paper, a rectifier-less single stage AC-DC voltage converter is used to convert the alternating magnetic field to a DC voltage, as well as providing matching conditions to transfer maximum power. In the proposed structure, a low power impedance matching PWM generator is presented which uses pulse width domain signal processing, and thus reduces power consumption. The performance of the proposed circuit is demonstrated using theoretical elaborations. In addition, the proposed structure is simulated using a 0.18 mu m standard CMOS technology, based on which the circuit power dissipation is about 7 mu W at 70 kHz and the proposed circuit efficiency is about 94.5%. The maximum power transferring efficiency is about 96% at 120 mu W input power.