A MPPT Circuit With 25 $\mu\text{W}$ Power Consumption and 99.7% Tracking Efficiency for PV Systems

A Maximum Power Point Tracking (MPPT) circuit for a 0.7-W photovoltaic (PV) system is proposed. The circuit employs a modified hill-climbing algorithm based on a 3-points comparison instead of the traditional 2-points comparison. The adopted algorithm simplifies the detection of the Maximum Power Point (MPP) and enables the implementation of a periodic sleep-mode to reduce the overall power consumption without compromising effective tracking of irradiance variations. Moreover, to achieve high MPP tracking efficiency, a low-power linear analog multiplier is implemented to accurately compute the instantaneous power of the PV source from its sensed voltage and current levels. This power-metering function is realized in the analog domain to eliminate the need for data converters and to minimize the MPPT circuit's power consumption. A complete design of the proposed circuit is implemented in 0.18-μm BiCMOS process in less than 1.55 mm
²
and consumes less than 25 μW with the digital core running at 500 kHz and a measured peak MPP tracking efficiency of 99.7%.