A Charge Pump with MPPT Circuit Employed in Batteryless Photovoltaic IoT Tags

• Main Authors: Men, Guan-Yu, 門冠宇
• Other Authors: 趙昌博
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/7tm42s

碩士 === 國立交通大學 === 電控工程研究所 === 104 === A dc-dc regulator is proposed to attach to the battery-less solar tag applied in the Internet of Things (IoTs) market. Two main purposes in this design is to maximize the transfer efficiency and to provide a high enough supply voltage to the back-end circuit. The overall circuit consists of the cross-coupled charge pump, optimal power point tracking and timing control circuit. It is expected to boost the input voltage around 0.55-0.65V to the output 1-1.1V at 80-100μW condition. Gated PFM circuit is adopted in the optimal power point tracking system to modulate the input frequency of the charge pump to match the inner resistance of the solar cell. This system has been taped-out by TSMC 0.18UM 1P6M process twice and N-fab 0.35UM process once. The experimental results of 2nd chip show that the voltage conversion efficiency (VCE) is 97% and the power conversion efficiency (PCE) is 11.7% at 30μW input power condition. The reason of the low efficiency has been found and improved by enhancing the pumping capacitance. This has been proven by the hspice. The efficiency of the 3rd tape-out in N-fab has been improved to 81.2% according to the simulation results.