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 <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small>-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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {R}_{\text {TE}}$ </tex-math></inline-formula> of the thermoelectric generator (TEG), which achieves high tracking efficiency over a wide <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {R}_{\text {TE}}$ </tex-math></inline-formula> 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-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m standard CMOS process with a core area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.91 \times 0.61$ </tex-math></inline-formula> mm2. Measured results show that the proposed interface can harvest TE over the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {R}_{\text {TE}}$ </tex-math></inline-formula> variation range of 1–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1000 \; \Omega $ </tex-math></inline-formula>, 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 \; \mu $ </tex-math></inline-formula>W −10 mW.