Power Supply Switch Circuit for Intermittent Energy Harvesting

Abstract

Energy harvesters generate power only when ambient energy is available, and power loss is significant when the harvester does not produce energy and its power management circuit is still turned on. This paper proposes a new high-efficiency power management circuit for intermittent vibration energy harvesting. The proposed circuit is unique in terms of autonomous power supply switch between harvester and storage device (battery), as well as self-start and control of the operation mode (between active and sleep modes). The self-start controller saves power during an inactive period and the impedance matching concept enables maximum power transfer to the storage device. The proposed circuit is prototyped and tested with an intermittent vibration energy harvester. Test results found that the daily energy consumption of the proposed circuit is smaller than that of the resistive matching circuit: 0.75 J less in sleep mode and 0.04 J less in active mode with self-start.To transfer the output power efficiently from PEH to a wireless sensor node (WSN), power management circuits have been actively researched [16][17][18][19][20][21]. Synchronized Switch Harvesting on Inductor (SSHI) is one of the popular options for PEH. SSHI can reduce the internal capacitance of PEH's effects so that PEH can continuously supply the power to the load. In [22], SSHI showed 85% of AC-DC conversion efficiency. However, SSHI can increase the efficiency of AC-DC conversion only when both electromechanical coupling factor k 2 and mechanical quality factor Q m are low [23]. Considering intermittent and random ambient vibration, maximum power point tracking (MPPT) was actively researched. When the vibration frequency of PEH is changed, the impedance of PEH is also changed. MPPT can adaptively match the impedance with the PEH's to maintain the maximum power transfer condition. Among the previous studies, Shim et al. [24] showed the highest MPPT efficiency (99%).Still, the research on the power management circuit considering intermittent and random input energy is in infancy. Gyorgy et al. [25] proposed a self-start circuit, but it has some drawbacks such as 340 s of cold-starting time for activating a power management circuit, and no sleep mode control. In [26][27][28], junction gate field-effect transistor (JFET) based start-up circuits were proposed for low voltage start-up, which can boost the several mV to the start-up voltage level (>1.5 V) for starting operation of power management circuit. However, this topology is only beneficial to energy harvesters that generate low voltage such as electromagnet and thermoelectric energy harvester. Our previous studies designed start-up circuits that are suitable to PEH with the intermittent and random input conditions [29][30][31] in which the controllers autonomously switch between sleep and active modes considering random and intermittent energy. In [29], the impedance matching circuit with sleep mode reduced the power loss using a controller powered by a storage device (e.g., battery) when there is n...

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