Power management for ambient energy harvesting in passive integrated circuit

Loo, Ka Fei Vieri (2023) Power management for ambient energy harvesting in passive integrated circuit. Final Year Project, UTAR.

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Abstract

A sensor node plays a crucial role in the IoT network as it receives and transmits data from the environment to users. However, battery-powered sensor node can be bulky and requires frequent maintenance. The aforementioned issues can be solved by integrating ambient energy harvesting feature into the power management IC (PMIC) to eliminate the dependency on external power supply. PMIC is a unit that manages the power conversion from the harvested energies and provides stable power to other block units to operate within the sensor node. As the advancement in IoT field has led to the significant reduction in power consumption of sensor node, it becomes more practical to integrate ambient energy harvesting into the device. The objectives of this project include the design of a low-powered PMIC to support the power requirement of four commercial components typically found within a sensor node, which consist of a temperature sensor, an accelerometer, an A/D converter, and a microcontroller with transceiver. The PMIC will be designed to supply output voltage of 1 V to the loads, with total power demand of 906.32 µW. Reviews on ambient sources such as solar, radio frequency (RF), human motion and thermal are conducted to study their potential to be used for energy harvesting purposes. Furthermore, the next objective is to integrate the proposed PMIC with ambient energy harvesting feature. Such IC will be designed using 32 nm CMOS technology provided by the Predictive Technology Model (PTM). There are a total of eight blocks within the proposed PMIC, which include charge pump, cross-connected differential drive rectifier, bandgap core, comparator, voltage-controlled oscillator, ramp generator, switch controller unit and DC-DC converter with auxiliary unit. The PMIC will initially require RF (after rectification) to power the bandgap core which generates stable biasing voltage and reference current to other units. Harvested energy from solar, motion and thermal will be stored in primary storages. Those energy are allowed to flow into DC-DC converter when a minimum voltage of 0.1 V is measured across the storage. The boost topology-based converter steps up the harvested voltage to 1 V, aided with auxiliary unit as its feedback system. The simulation results showed the PMIC is capable of supplying an output power of 913.64 µW to the loads with a power consumption of 5 µW. Though its average output voltage was recorded at 898.17 mV with a ripply voltage of 33.73 mV. A low-dropout regulator and energy profile tracker unit are suggested to be included for future work improvements.

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