Charging device for wearable electromagnetic energy-harvesting textiles

Abstract

The study aims to develop charging devices for wearable electromagnetic energy harvesting textiles (WEHT). Electromagnetic energy through human movement can be easily and naturally generated and is not significantly affected by environmental factors, however, the electric current generated by the electromagnetic method of human movement is difficult to efficiently charge. Three charging circuits for use with wearable electromagnetic energy-harvesting textiles were developed. The three types of charging circuits developed are rectifier, voltage doubler, and voltage quadrupler circuits. The performances of the developed circuits were evaluated in comparison with a normal storage circuit, in which the generated energy is stored immediately. The results show that storage energy was generated from the WEHT in all the developed circuits, and the charging efficiency improved as the simulated walking frequency increased. Energy generated from wearable electromagnetic energy harvesting textiles has the highest storage efficiency when charged with a rectifier circuit. The rectifying circuit method showed a charging rate twice that of a normal storage circuit. The charging speed of the rectifier circuit was faster to reach 3.7 V, the nominal maximum barrier voltage of the single-cell lithium-ion batteries used in portable devices, than the normal charging circuit. In the voltage multiplier circuit, the voltage drop generated in the circuit was large, so the charging efficiency was not superior to the normal circuit or rectifier circuit. In conclusion, it is most effective to use a rectifier circuit for charging portable electronic devices using the energy harvested by wearable electromagnetic energy harvesting textiles.