A Highly Efficient Time-Based MPPT Circuit With Extended Power Range and Minimized Tuning Switching Frequency

This paper presents a highly efficient time-based maximum power point tracking (TB-MPPT) circuit with an enhanced three-dimensional tuning method. In the proposed circuit, firstly, the reconfigurable switched capacitor dc-dc converter with three conversion ratios is used to extend power range. The conversion ratio is selected according to input voltage level to avoid large charge redistribution loss. Secondly, the proposed algorithm can find the maximum power point with the minimum tuning switching frequency and capacitance control knob to reduce power loss, which results in high power conversion efficiency (PCE). The TB-MPPT circuit is fabricated with a 180nm CMOS process and has an active area of 0.42mm. The measured results achieve a peak PCE of 90.4%, a peak power tracking efficiency of 99.6%, and the output power of
$52~\mu \text{W}$
in an energy harvesting system with four commercial PV cells.