Research On Active Rectifier Circuit For Energy Harvesting System

Internet of Things(IoT)is developing rapidly as an important part of the new generation of information technology,in recent years.The maturity of 5G technology is accelerating the arrival of Internet of All Things.Wireless sensor networks(WSN)based on a huge number of wireless sensor nodes with communication functions play a vital role in the development and application of IoT.Once batteries of the nodes is exhausted,it will have a serious impact on the operation of the WSN even the IoT.Harvesting environmental energy as a supplement or replacement of the batteries for WSN nodes become an effective solution.The piezoelectric(PE)vibration energy is favored by the academia and industry because of the advantages of high energy density,widespread in the environment,and easy harvesting,ect.According to the problems of the load-dependent characteristics and the overall low efficiency of the PE energy harvesting system,a high-efficiency rectifier is proposed in this dissertation.It is based on an ultra-low voltage drop active rectifier with a cross-coupled pair of PMOS transistors and a pair of comparator controlled NMOS transistors.The adaptive P-SSHI is added to improve the energy harvesting efficiency further.The comparators in the active rectifier act as zero current detection of the rectifier and provide the turn-on signal for the synchronous switch in adaptive PSSHI circuit.And the zero current detection in L-C resonant circuit provide the turn-off signal.The adaptive control of synchronous switch is realized,with a better follow of the end time of the L-C resonance,a reduced time error,and an improvement of the efficiency.The simulations and the experiments are done and the results show that the adaptive control of the synchronous switch in PSSHI is implemented,and the overall efficiency of the PE energy harvesting circuit is improved.Under the same conditions,when the load resistance is 100 K?,the output power of the proposed circuit is 232% compared with a full-bridge rectifier circuit.In order to get a better performance the adaptive control of synchronous switch in P-SSHI is optimized.Four PMOS transistors with unique connection is used to implement the self-turn-off synchronous switch,so that it can be turned off automatically without any detection circuit when the L-C resonant of the P-SSHI is finished.Additionally,the turn-on control circuit of the synchronous switch is simplified.The simulations results of the self-turn off synchronous switch control circuit shows,when the load resistance is 100??,the circuit can increased output power to113% compared with the adaptive P-SSHI active rectifier circuit,and is 240% compared to a fullbridge rectifier.