This paper proposes a highly efficient Time-Based Maximum-Power-Point-Tracking (TB-MPPT) integrated-circuit. Conventional TB-MPPT circuit shows unstable status (oscillation) near the Maximum Power Point (MPP), which causes the degradation of the overall power tracking efficiency. To overcome this critical issue, the proposed circuit separates the tracking operation into two periods, and it utilizes convergence range averaging technique with an adaptive perturbation step according to each control signal to accurately extract the current power level without oscillation problem. This work is fabricated in 180 nm CMOS process to demonstrate advantages of the proposed scheme. With 0.47V 12mW Photovoltaic (PV) cell, the measurement results show 94.2% of MPPT efficiency and 91.6% of power conversion efficiency (PCE). It occupies silicon chip area of 1.69 mm 2 .

This letter presents a highly efficient and wide input range maximum power point tracking (MPPT) circuit for energy harvesting systems (EHSs). The conventional MPPT circuit shows attenuation of the power conversion efficiency (PCE) at low input voltages due to insufficient distribution of conversion ratio (CR) in switched capacitor (SC) dc–dc converters. To overcome this critical issue, the proposed circuit implements coarse and fine stages to increase the number of CR. The proposed MPPT operation can be accurately achieved with CR tuning only (without switching frequencies), which results in high PCE. This work is fabricated in the 180‐nm CMOS process and measured with the commercial photovoltaic (PV) cells to demonstrate the advantages of the proposed circuit. The measurement results show that the EHS achieves a flat and improved PCE over a wide input range of 0.4 to 1.6 V. The PCE is as high as 88% for an output power below 50 μW and the active area occupies 1.2 mm2.

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