Input-powered interface circuits for electrodynamic vibrational energy harvesting systems

Vibrational energy harvesting systems that convert ambient mechanical energy in the environment to usable electrical energy represent a promising emerging technology to achieve autonomous, self-renewable, and maintenance-free operation of wireless electronic devices and systems. Typical energy harvesting systems are composed of three components: an energy harvester that converts the mechanical vibrations into electrical energy, an interface circuit that conditions and regulates the energy, and an electronic load that uses or stores the harvested energy.;This dissertation specifically focuses on the development and experimental characterization of input-powered energy harvesting circuits, including ac/dc converters and a dc/dc converter, for electrodynamic vibrational energy harvesters. This inputpowered feature allows the active interface circuitry to automatically enter a zero-powerconsumption standby mode when the voltage from the harvester is below a threshold level, thus eliminating any energy drain between energy harvesting cycles. Implemented in a 0.5 mum CMOS technology, the interface circuit is bench-top characterized with a sine wave signal generator and also with real vibrational energy harvesters. The measurement result shows that the minimum input threshold voltage is 1 V at openload. When the ac input amplitude is 2.6 V and regulated dc output is 3.7 V, the interface circuit can achieve a peak net efficiency of 61% with 16.7 mW of output power delivered.;A simplified equivalent circuit model for a resonant-type electrodynamic energy harvesting system is developed including a lumped element model (LEM) for the resonant harvester, a simplified interface circuit model, and a load model. The overall system model is validated via comparison of circuit simulations with experimental measurements. Lastly, a complete and fully self-sufficient energy harvesting system is demonstrated using the input-powered interface circuit and a non-resonant electrodynamic harvester, designed specifically for harvesting energy from human movements. Tested under normal human activities (walking, jogging, cycling), the 70 cm3 system is shown to charge a 3.7 V rechargeable battery with an average power of 234 muW during jogging.