Abstract
This paper reports a fully integrated autonomous power management system for thermoelectric energy harvesting with application in batteryless IoT/Wearable devices. The novel maximum power point tracking (MPPT) algorithm does not require open circuit voltage measurement. The proposed system delivers 0.5 mA current with 1 V regulated output based on simulations, which is the highest output current for a fully integrated converter reported in the literature for ultra-low voltage applications, to the best knowledge of the authors. Regulated 1 V output can be achieved for load range >2 kΩ, and input voltage range >140 mV. The circuit has been implemented in UMC-180nm standard CMOS technology and simulated.
Highlights
Elimination of the battery is desirable in emerging applications such as internet of things (IoT) and wearable healthcare devices, due to considerable miniaturization and maintenance cost benefits [1]
maximum power point tracking (MPPT) algorithm presented in [3,9] measures TEG open circuit voltage, VTEG, for impedance matching, and causes system disruption when disconnected
When the output voltage drops below the target value, which can be a result of an increase in load or decrease in source voltage, MPPT block looks for a new optimum to reach the target voltage, by reducing the number of stages
Summary
Elimination of the battery is desirable in emerging applications such as internet of things (IoT) and wearable healthcare devices, due to considerable miniaturization and maintenance cost benefits [1]. Among various ambient energy sources, thermal energy is promising for wearable computing and similar applications, due to the availability of hundreds of microwatts of harvestable power. Our group has reported solutions with an input voltage as low as 200 mV, where the maximum output power of 400 μW is achieved with a 2.7 kΩ load, which is sufficient to meet the real-time demand of most ultra-low power IoT/Wearable circuits [7,8]. MPPT algorithm presented in [3,9] measures TEG open circuit voltage, VTEG, for impedance matching, and causes system disruption when disconnected. The method does not work well when the converter efficiency varies with input impedance values, as is the case for the LC-tank coupled charge pump topology.
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