Start-up Circuit for Synchronous Switched Energy Extraction from Triboelectric Energy Harvesters

Ambient triboelectric vibration energy harvesters used for self-powering IoT sensor nodes provide enhanced power output when interfaced with synchronous switched energy extraction circuits. However, these active interface circuits require overhead power for their switching actions and may suffer from cold-start issue, for example, in batteryless IoT system. This work develops a start-up circuit that initiates energy extraction via passive full-wave-rectification path and on accumulation of enough energy for control actions, autonomously toggles to an active synchronous switched optimal path, maximizing the energy extraction from the harvester. We integrate the here developed start-up circuit with our previously demonstrated multi-shot synchronous charge extraction (MS-SCE) circuit. The resultant self-starting end-to-end power management circuit is designed and simulated in TSMC 70V
$\boldsymbol{0.18}\mu \mathbf{m}$
BCD process and its operation is validated in a triboelectric energy harvester powered batteryless IoT setting. The transition from passive to active optimal steady-state mode is achieved in 41.1 seconds and the start-up circuit's overhead/parasitic-loss is only 3.43
$\mu \mathbf{W}$
or 6.7% of the harvested power in the steady-state.