17.6 A Reconfigurable DC-DC Converter for Maximum TEG Energy Harvesting in a Battery-Powered Wireless Sensor Node

Energy harvesting is an attractive solution to extend battery lifetime in a wireless sensor node (WSN). However, energy harvesting resources are inherently sporadic and critically affected by their environment, mandating energy storage elements (e.g., battery or super-capacitor) to guarantee a reliable operation. Recent studies that use energy storage elements mainly focus on efficient power extraction from the harvesting sources [1] -[5]. With many WSNs, the required amount of power during the sensing mode is small but increases significantly, often much higher than the instantaneous harvesting power, during the wireless data transmission. Therefore, the WSN cannot function properly with a simple boost converter topology with a limited output capacitor, and even it wastes energy under light load condition [1]. Thus, a storage element is required in the cases of remaining topologies [2] -[5]. In a 2-stage cascaded boost and buck converter topology, the boost converter harvests continuously to the storage element and load is supplied from the storage element, but the cascaded operation of the boost and buck converter leads to a poor overall efficiency [2]. A discontinuous energy harvesting mode is introduced in [4], [5] to address the above issues. However, during the storage element powered mode, the output voltage could be seriously unregulated when the stored energy is directly transferred to the output [4]. Besides, there still remains an inefficiency concern as the system stops collecting energy from the harvesters during the storage element powered mode [4], [5]. This work presents a reconfigurable DC-DC converter for maximum thermoelectric generator (TEG) energy harvesting in a battery-powered WSN. The converter operates in single-input dual-output (SIDO) boost and battery-supplied buck modes with a single inductor achieving 88.5% peak end-to-end and 93.3% efficiencies, respectively. Battery-TEG pile-up buck (BTPB) and dual-phase buck/boost (DPBB) modes are proposed to maximize the TEG power extraction during the battery-powered operation, resulting in up to 44% saving in the battery power.