A Management Circuit with Upconversion Oscillation Technology for Electric-Field Energy Harvesting

Abstract

Traditional LC resonance circuit can continuously and efficiently accumulate energy from the harvester at optimal impedance matching. Due to electric-field frequency (50 Hz, in China) and small equivalent capacitance (tens or hundreds of picofarads) of electric-field capacitive harvester, it is difficult to manufacture a huge transformer with a large inductance (>10 000 H) to optimally match the capacitive harvester. An upconversion oscillation circuit with a smaller size transformer around high-voltage power line is proposed to achieve efficient electric-field energy harvesting in this paper. The power-frequency output signal is transformed into higher frequency oscillation signal in the upconversion circuit consisting of the switch and the transformer. In this case, optimal impedance matching with the smaller size transformer is realized. Therefore, weak energy from harvester is fast accumulated into the storage capacitor by using the upconversion oscillation circuit. For a 10-kV power line, the upconversion maximum charging power reaches 663 μW in experiment. Due to optimal impedance matching in the upconversion oscillation circuit, the maximum harvesting efficiency is increased from 3% to 90.5%, compared with the traditional harvesting method. While the voltage across the storing capacitor is 3.26 V, the instantaneous discharge circuit can drive a wireless sensor node with an output power of 110 mW.