Design of a DC-DC Boost Converter of Hybrid Energy Harvester for IoT Devices

By energy harvesting, ambient energy from our environment can be converted into electrical energy, which can power small wireless devices and thus replacing batteries. The typically small amount of energy provided needs to be efficiently managed to be able to supply IoT devices. In a lot of cases one harvester is not sufficient. To overcome this issue energy converters need to be designed in a suitable manner fitting to the properties of ambient sources and combinations of converters in hybrid solutions can be implemented to boost the amount of converted energy. Combining different harvesters from multiple energy sources increases the reliability of the energy supply under fluctuations of ambient energy. This work reports about the design of a boost converter for an hybrid energy harvesting solution using three ambient sources, which are Radio Frequency, thermal energy and vibration for powering an IoT sensor system. The proposed boost converter is used to boost the small input voltage from thermal, radio frequency and vibration. To achieve the desired output range, the inductance in the boost converter is varied from 0.3 to 1.4μH I for thermal source and from 0.10 to 0.21 μH for the hybrid inputs. The optimum inductance value is 0.21 μH for the hybrid sources to achieve the required output voltage of 3.0 to 5.5 V. The converter consumes 0.28 mW of power, delivers 3.3 mW of output power, and is 91.6 % efficient for a 500 mV input. All circuits are designed and simulated using LTSPICE software.