Ultra-low power electronics for energy harvesting node
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Apart from providing detailed insight about the energy harvesting system as a whole, this work tackles the challenges of efficient control of the interface circuit of an electrostatic vibration energy harvester, with severely limited power consumption allowance for the controlling electronics. Used interface circuit consists of double charge-pump topology, comprising a storage element (pre-charged reservoir capacitance), dual antiphase variable capacitance and an intermediate storage element, with an inductive flyback return path. Since high voltages are expected in the long term operation, switch component of the interface circuit is realized as a high-voltage PMOS device from AMSH35 process by AMS. Concerning the interface circuit, theoretical analysis was introduced, to demonstrate the requirement for precise synchronization of the switch with the circuit voltage levels, with the purpose of optimizing the harvested energy. Previous work was addressed, and this work was built upon it. For decreasing the power consumption of the critical component, a low power clock-signal generator was designed, with power consumption of approximately 0.35nW, and accompanying stable current reference with constant power consumption of 0.57nW, and 4.7%/V current deviation caused by variations in the supply voltage. Additionally, issues accompanying the long term operation, and thus increase in the pre-charge voltage, were discussed in details, and subject of interest for further research and promising possible improvements were suggested.