A 99.9% Efficient, Ultra-Low Power Automated On/Off Adaptive MPPT Circuit for RF, PV, and TEG Sources From 1 μW to 4 mW

This paper presents a high-efficiency, ultra-low-power automated on/off adaptive MPPT (AOA-MPPT) system for microscale energy harvesters. It is designed to extract the maximum available power from photovoltaic (PV), radio frequency (RF), and thermoelectric generator (TEG) energy sources. AOA-MPPT combines a power-change detector (PCD) that activates tracking only when input power changes (auto-on) with an auto-off convergence detector that halts perturbation at lock and powers down MPPT circuitry, eliminating steady-state dither and lowering controller power. Input power is estimated from a single sample of the inductor peak current, enabling duty-cycled sensing with low sensitivity to converter gain. A low-power, wide-range PWM control (LS-PWM) provides broad duty-cycle adjustment of the inductor charge time, enabling input impedance matching for maximum power transfer. The AOA-MPPT circuit is designed along with a boost converter and fabricated in 65nm CMOS technology. It achieves a peak tracking efficiency of 99.9%, a peak converter efficiency of 87%, and a power consumption of only 112nW.