A lowest voltage stage driven active diode full-wave charge pump with load selection has been developed at the University of Michigan for structural health monitoring applications. Bridge health monitoring sensors can be powered by vibration harvesters actuated by non-periodic low-acceleration suspension bridge movement. However, this type of harvester output requires an interface circuit that is capable of frequent cold start-ups.
The charge pump developed at the University of Michigan consists of an active diode IC-based full-wave charge pump that interfaces to vibration harvesters, with the active diode switching being controlled by the lowest voltage stage. In contrast to passive diode circuits that require input voltages greater than the diode turn-on voltage, the proposed architecture enables cold start-up with only one low voltage AC input (a passive start-up approach reduces the required input voltage).
After passive start-up, improved active sub-threshold operation boosts the DC output. The charge pump cold starts with low power (under 10μW) and low open circuit voltage (220 – 450mV) inputs near 100-130Hz. Further, the charge pump can boost the output to over 1.5V with periodic and non-periodic up-converted inputs from a vibration harvester. Overall, the circuit consumes between 0.6–1μW of active power at voltages over 1V, demonstrates approximately 50% circuit power efficiency, and only takes up 1.2 square mm of area in 180nm CMOS
- Vibration energy harvesters for structural health sensors
- High efficiency
- Low power consumption
- Low area overhead