The proposed circuit aims to harvest energy from AC powerlines with an ultra-wide current range. A buck-boost converter operating in discontinuous conduction mode (DCM) is adopted for impedance matching, as the input impedance of the converter is ideally independent of operating conditions to ensure impedance matching for various types of wireless sensors with different impedances. Measurement results show that the proposed power line energy harvesting system can harvest energy from AC powerlines with a wide current range of current from 10 A to 50 A, with the maximum efficiency of 88.78 %.