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 (
η
_E-E
) when the output power of PV cell (
P
_PV,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
μ
W. The measured
η
_E-E
at low
P
_PV,MAX
(13
μ
W) is 88%. The measured peak
η
_E-E
is 94.4% at 82
μ
W.