电场能量采集器的最大输出功率追踪电路设计*

本文采用频率变换原理采集输电线周围电场能量,设计了一种能量采集电路,对超级电容充电。负载阻抗呈电容性,为非线性负载,充电过程中阻抗不断变化。为实现最大输出功率传输,设计了低功耗的最大输出功率追踪(MPPT)电路,采用频率值为32.768 k Hz石英晶体构成方波振荡电路,因电容电压不能突变,通过充电电流控制开关导通时间,构成电流反馈最大输出功率点追踪系统。最大输出功率追踪电路的工作电流为1.2 u A,工作电压为5 V,功耗为6 u W。实验结果表明,在充电36min时达到最大功率输出,储能电容电压的大小为0.32 V,输出功率最大为18 u W。相比于直接充电电路,最大输出功率电路的能量采集效率提高了50%。

Design of maximum power point tracking circuit for electric field energy harvester

This paper adopts frequency conversion principle to perform the energy harvesting from the electric field of overhead power line. An energy harvesting circuit is designed to charge the supercapacitor. The load impedance is a capacitive and non-linear load, and the load impedance changes in the charging process. In order to achieve maximum output power transmission, a maximum power point tracking (MPPT) circuit with low-power consumption is designed, which uses a 32.768 kHz quartz crystal to form a square wave oscillating circuit. Because the capacitor voltage cannot change suddenly, the current feedback MPPT system is constructed through controlling the switch turn-on time with the charging current. The MPPT circuit is tested at an operating current of 1.2uA, an operating voltage of 5V, and a power consumption of 6uW. Experiment results show that the charging voltage across the energy storing supercapacitor is 0.32V, and the output power reaches a maximum value of 18uW at the charging time of 36min. Compared with the direct charging circuit, the energy harvesting efficiency of the MPPT circuit increases by 50%.