An Ultra-low Power Automated Maximum Power Point Tracking Circuit with 99.9% Tracking Efficiency.

This paper presents a maximum power point tracking (MPPT) circuit for DC-DC converters which is well suited for DC energy harvesters. To save the power of the tracking circuit when there is no variation in the input power, a power change detector (PCD) circuit is also proposed in the MPPT circuit. With PCD, changes in the input power are detected, thereby activating the MPPT circuitry for tracking. When MPP is achieved, the proposed logic shuts down the MPPT-related circuits to save power. A modified hill-climbing (HC) technique is implemented for the tracking algorithm to address the speed/precision tradeoff. The MPPT circuit uses a power estimation method based on sensing and sampling of the inductor peak current, achieving a high tracking efficiency. The proposed MPPT system is designed in 65nm CMOS technology. Simulation shows a peak tracking efficiency (TE) of 99.9% is achieved without oscillation of the operating point. The power consumption of the proposed MPPT circuit is 125nW.