A hybrid micro vibration energy harvester with power management circuit

• A hybrid micro vibration energy harvester with power management circuit is developed and tested.
• A mathematical model is established to calculate output power from the hybrid energy harvester.
• The output power of hybrid energy harvester is improved by using a damping matching method.
• The output voltage of piezoelectric transducer is increased by using MEMS PZT cantilever arrays architecture.
• A complete solution of self-powered micro vibration power supply for wireless sensor node is proposed.

In this paper, a hybrid micro vibration energy harvester based on piezoelectric and electromagnetic transduction mechanisms is developed and tested, which improves total output power and voltage in low frequency and small amplitude vibration environment. It contains a MEMS piezoelectric (PZT) cantilever array with an integrated Si proof mass, an NdFeB magnet attached to the free end of the cantilever beam, and one multi-layer micro coil fabricated using standard PCB technology placed on the fixed bottom. A mathematical model is established to calculate the output power from the hybrid energy harvester. The optimum size of the device’s structure is obtained based on the finite element analysis. Experimental test results show that the maximum output power of 40.62 μW can be drawn from the hybrid energy harvester with the optimal load resistance under the vibration of 0.2 g acceleration at the resonant frequency of 55.9 Hz. The more power output can be generated than a stand-alone piezoelectric or electromagnetic device, and the output voltage is increased by using the MEMS PZT cantilever array architecture. In order to regulate the output voltage of energy transducer, a low power consumption power management circuit integrated with AC–DC rectifier and DC–DC buck converter is designed and applied in wireless sensor nodes. The test results prove that the hybrid energy harvester can provide a stable output power supply voltage of 3.6 V for wireless sensor node.

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