A 115× Conversion-Ratio Thermoelectric Energy-Harvesting Battery Charger for the Internet of Things

摘要

This article presents a high-conversion-ratio (HCR), high-voltage-tolerant (HVT) energy-harvesting battery charger using 0.18- $mu ext{m}$ standard CMOS for Internet of Things (IoT). To reduce conversion ratio (CR) of inductive power converter and optimize overall power efficiency, the proposed charger cascades a boost converter and reconfigurable charge pump. Different from the high-voltage device, the standard CMOS process has lower parasitic capacitance and on-resistance; therefore, it can reduce switching and conduction loss. The reconfigurable charge pump dynamically changes the number of pumping stages according to the output voltage ( $V_{{OUT}}$ ) by automatic configuration selector (ACS). To manage the limited power from a thermoelectric generator (TEG), the converter works under the discontinuous conduction mode (DCM). The zero-current detector (ZCD) employs an analog comparator with digital offset compensator and digital comparator to control off-time ( $T_{{OFF}}$ ) quickly and accurately. The self-idle constant on-time (SI-COT) and idle mode both control the mechanism, helping to further reduce static power dissipation. As a result, the proposed converter can achieve peak efficiency of up to 76% at a $92imes $ conversion ratio with output power ranging from $10~mu ext{W}$ to 1.9 mW. The available input voltage ranges are 40 to 400 mV, and the dual output voltage ranges are 1 to 1.6 V and 2 to 4.6 V for $V_{{BOOST}}$ and $V_{{OUT}}$ , respectively.