A Time-Based Direct MPPT Technique for Low-Power Photovoltaic Energy Harvesting

This letter introduces a maximum power point tracking (MPPT) technique for photovoltaic (PV) energy harvesting (EH) systems to enhance the end-to-end efficiency (eta(E-E)) when the output power of PV cell (P-PV,P-MAX) is low. A ripple-based PV cell current sensing and a time-domain multiplication are proposed to monitor the PV cell power delivered to the charger, which reduces the controller power consumption (P-CTR). The PV EH system with the proposed MPPT method is implemented in a 180-nm CMOS process. The P-CTR is 1.34 mu W. The measured eta(E-E) at low P-PV,P-MAX (13 mu W) is 88%. The measured peak eta(E-E) is 94.4% at 82 mu W.