A Dual-Frequency Thermal Energy Harvesting Interface With Real-Time-Calculation ZCD

This article presents a dual-frequency (DF) dual-input-dual-output interface based on a reconfigurable switching converter for thermoelectric energy harvesting. The DF operation decouples the rate of energy extraction at the input stage from the rate of energy distribution at the output stage. The interface automatically makes transitions among two energy-harvesting modes and one energy-recycling mode according to the load condition. The low-frequency harvesting together with the high-frequency recycling allows the interface to maintain high efficiency across a broad range of load. A zero-current detection (ZCD) approach based on real-time calculation turns off the power switches instantaneously and accurately to prevent synchronization loss. The interface is fabricated with a 0.13- μm CMOS process. From the measurement results, the input voltage is regulated in the range from 30 to 500 mV with the aid of maximum power point tracking (MPPT) and the output voltage is regulated at 1.2 V. The peak energy harvesting efficiency is 86% with 250-mV input voltage. Higher than 80% efficiency is achieved with 80-500 mV input voltages. The peak energy recycling efficiency is 94% and the power consumption of control circuits is 0.6 μW.