A Low-Ripple DIDO DC–DC Hybrid Interface With Optimal-Hysteresis-Controlled MPPT for TEH

This article proposes a dual-input-dual-output (DIDO) dc-dc hybrid interface for thermoelectric energy harvesting (TEH) applications with high efficiency and low output ripple. A load-first ordered power distributive control (OPDC) strategy is used to recycle the excess thermoelectric energy (TE) in time. Utilizing the digital adaptive on-time (DAOT) technique, the output ripple can be reduced during battery (BAT) power supply. A hysteresis-controlled maximum power point tracking (MPPT) technique is proposed to track the variation of the internal resistance $\text {R}_{\text {TE}}$ of the thermoelectric generator (TEG), which achieves high tracking efficiency over a wide $\text {R}_{\text {TE}}$ range. By trading the tracking efficiency and loss off in the MPPT, an optimization method for hysteresis window is proposed. In addition, an analog zero-crossing detector (ZCD) without calibration is adopted to improve the end-to-end efficiency. The proposed hybrid interface is realized by 0.18- $\mu $ m standard CMOS process with a core area of $0.91 \times 0.61$ mm2. Measured results show that the proposed interface can harvest TE over the $\text {R}_{\text {TE}}$ variation range of 1– $1000 \; \Omega $ , with a peak tracking efficiency of 99.6% and an output ripple as low as 35 mV. It also achieves a peak end-to-end efficiency of 87% and an output power range of $1 \; \mu $ W −10 mW.