A Time-to-Voltage Converter-Based MPPT With 440 μs Online Tracking Time, 99.7% Tracking Efficiency for a Battery-Less Harvesting Front-End With Cold-Startup and Over-Voltage Protection

This paper introduces a time-to-voltage converter-based maximum power point tracking (TVCB-MPPT) for harvesting photovoltaic energy into a super-capacitor using a single solar cell. In the proposed design, a time-to-voltage converter is used to achieve a fast and accurate tracking of the maximum power point (MPP) without using a time-averaging/time-integrating function as used in the conventional time-based MPPT design. Moreover, with the continuous monitoring of the MPP, the proposed converter responds immediately and maximizes the extracted energy under varying irradiance conditions as compared to the conventional intermittent MPPT topologies. The addition of the cold-start operation and the over-voltage protection increase the robustness and energy-autonomy of the overall system. The proposed TVCB-MPPT converter is fabricated in a 180 nm CMOS process. In the measured result, a fast online MPP tracking time of 440~\mu s is observed with an initial tracking time of 4.8 ms. It also shows a peak tracking efficiency of 99.7% with a power conversion efficiency >87% in the entire input power range.