20.9 An energy-recycling three-switch single-inductor dual-input buck/boost DC-DC converter with 93% peak conversion efficiency and 0.5mm2 active area for light energy harvesting

Energy harvesting (EH) can be used in wireless sensor networks (WSNs) since the sensors can be powered by ambient energy in conjunction with rechargeable batteries to achieve near-perpetual operation [1-4]. One common solution is to harvest energy from ambient light through photovoltaic (PV) modules. In such a system, a battery supplements energy when the power provided by the environment is insufficient or when the WSN is active, and stores surplus energy for future use when the WSN is inactive. Accordingly, power management in an EH system involves a balance among the PV module, battery and load. Previous work [1] has implemented an EH system for moving vehicles and portable devices, but it is not suitable for indoor light energy harvesting. Although a single-inductor multi-input multi-output (SIMIMO) topology is one solution, the efficiencies of existing implementations [2-4] are degraded by additional conduction and switching losses due to the inductor-sharing switches in series with the inductor. In response, this paper proposes an energy-recycling strategy and implements the corresponding power converter with fewer switches.