Real-time current-waveform sensor with plugless energy harvesting from AC power lines for home/building energy-management systems

Abstract

Home/building energy-management systems (EMSs) driven by information technology are expected to be key to the achievement of an upgraded energy infrastructure, such as Smart Grid. While EMS may offer monitoring, reporting, and control of energy usage, these functions simply track intermittently the energy consumption and operational states of certain appliances and equipments. Further, since their sensing devices are not small, they cannot be attached to every appliance or piece of equipment. Some EMSs gather information, rather, at the power-distribution-board level or the multi-output-tap level. We report here a TX-integrated battery-free real-time current-waveform sensor. It is small enough to be attached to any piece of equipment for continuous power-consumption monitoring. Its key features are : 1) plugless energy harvesting (EH) from AC power lines, 2) real-time sensing and transmitting that use a half-cycle time-to-digital converter (TDC) to detect detailed information on current-wave forms with the precise time-resolution, and 3) asymmetrical power consumption, which helps to achieve high-power RF transmission with a limited EH power supply. Our sensor provides the 1mW power supply from an EH unit, as well as the -5.5dBm RF output power at the 50kS/s sampling with a 1mW EH power supply. We also demonstrate transmission of sensed current-waveform information of several appliances such as a hair dryer, a TV, a notebook PC.