Design Of High Efficiency DC-DC Boost Converter For Dual-source Energy Harvesting

To solve the issues that most traditional energy harvesting systems have a single input source,and the existing multi-source energy harvesting systems have low tracking efficiency and narrow input power range,this paper proposes a dual-source synchronous maximum power point tracking(DSS-MPPT)circuit.The proposed MPPT which is used to track the maximum output power of two ambient sources in real time is based on the comparator structure.The input energy sources can be properly switched by the digital control circuit.Thus,there is only needed one inductor in the system,thereby reducing the size of the energy harvesting system and the complexity of the circuit.Because the power conversion efficiency of traditional single comparator structure maximum power point tracking(MPPT)circuit would suffer drastically decreasing as the internal resistance of the energy sources increases.This limits their value for portable energy harvesting applications whose internal resistance have a wide range.To address this issue,after analysing the effect of delay duration of comparator on efficiency,an internal-resistance-adaptive(IRA)MPPT circuit for the micropower harvesting system from ambient sources is presented.The IRA circuit and delay synthesize circuit in this IRA-MPPT can track the dynamic changes of internal resistance of the energy source in real time and transmit optimized switching times to the switching transistors.The proposed IRA-MPPT circuit are designed with a standard 180 nm CMOS process and its power conversion efficiency can be increased by up to 33.2%compared to the classical MPPT circuits without IRA circuit.Its peak power conversion efficiency reaches 92.53% and the internal resistance range is as wider as 5? to 5K?.Mathematical analysis and simulation verification show that the proposed system can be well applied to wearable energy harvesting systems.