Voltage–Resistance-Adaptive MPPT Circuit for Energy Harvesting

This paper presents a voltage-resistance-adaptive (VRA) maximum power point tracking (MPPT) technique for energy harvesting systems. The VRA circuit is capable of handling large-scale changes in both voltage and resistance of thermoelectric generators (TEG), thereby improving energy conversion efficiency. Specifically, the VRA circuit in the VRA-MPPT can track realtime changes in voltage and internal resistance of the TEG and adaptively adjust the on-time of the transistor to obtain higher conversion efficiency under different input voltages and internal resistances. The circuit is designed and tested using the SMIC 0.18μm CMOS process. Test results show that with input power from 20μW to 50mW, energy harvesting systems using VRA-MPPT technology have high conversion efficiency, and the conversion efficiency can be increased by up to 30%. In addition, the test results show that an efficiency higher than 32.84% (R _S =400Ω, V _S =0.1V) efficiency can be achieved over the input resistance (R _S ) range of 50Ω-1KΩ and the input voltage (V _S ) range of 0.1V-1V, with a peak efficiency of 87.91% (R _S =100Ω, V _S =1V).