A 1-mW Solar-Energy-Harvesting Circuit Using an Adaptive MPPT With a SAR and a Counter

This brief presents an energy-harvesting system that uses an adaptive maximum power point tracking (MPPT) circuit for 1-mW solar-powered wireless sensor networks. The proposed MPPT circuit exploits a successive approximation register and a counter to solve the tradeoff problem between a fast transient response and a small steady-state oscillation with low-power consumption. The proposed energy-harvesting circuit is fabricated using a 0.35-μm CMOS process. The MPPT circuit reduces the transient response time by 76.6%, dissipates only 110 μW , and shows MPPT efficiency of 99.6%.