Implementation Of AC-DC Conveter For Low Frequency Electromagnetic Energy Harvesting Application

As one of the key technologies of the Internet of Things,sensor networks have been widely used in radio frequency identification,medical monitoring systems,smart offices,industry and military in recent years,and have become a research hotspot.Energy harvesting systems are taking place of traditional battery-powered systems to meet the requirements of wireless sensor networks including wide distribution,long life,and low cost.However,technologies that convert distributed energy around the environment into usable electrical energy need to address many design challenges.This thesis mainly focuses on the harvesting of low-frequency weak energy such as vibration energy and electromagnetic energy and designs an AC-DC high-efficiency low-voltage conversion circuit involving design challenges including low voltage start-up,energy efficient conversion,and output voltage regulation.The conversion circuit mainly consists of three parts: a low-voltage self-starting rectifier circuit,an asynchronous DC-DC boost circuit,and a feedback regulation circuit.Compared with the state of the art,the main innovations of this paper are as follows: First,the system adopts the Cold-Start technology,which avoids the extra external battery and can realize low voltage startup.Second,the system adopts asynchronous DC-DC boost circuit removing the clock generation circuit and the operational amplifier.The control circuit only requires two comparators,t thus avoiding the power losses related to the driving clock as well as eliminating the requirements of high driving voltage.Third,the feedback regulation circuit enables the system to give out an stable DC voltage which protects the following circuit from overload voltage,thus improving the practicality of the system.This converter was designed in the XFAB 0.18μm CMOS process.Simulation shows that with a 0.3 Vpeak input voltage the converter is capable of harvesting > 100μW power with more than 1V output voltage and over 90% efficiency.The system can start within 0.2 Vpeak input voltage.With modulation circuit,the output voltage can be stabilized at 1V and the ripple voltage is 15 mV.By adopting a low-voltage self-starting rectifier circuit and an asynchronous DC boost circuit,the system achieves efficient AC-DC voltage conversion,and greatly reduces the requirements on the input source,and can be widely applied in the power supply system of the wireless sensor node.