An output feedback-based start-up technique with automatic disabling for battery-less energy harvesters

This paper presents a start-up circuit based upon output voltage feedback for thermal energy harvesting. The feedback loop consisting of an output load, a boost converter core, a charge-pump-based doubler and a CMOS inverter switch to track the output voltage and generate a reset signal to kickstart the boost converter. The proposed start-up circuit shows a remarkably improved start-up time of 35μs at the input voltage of 290mV. The start-up circuit is automatically disabled after the boost converter reaches steady-state. Only one off-chip component is required, improving the cost efficiency. The proposed start-up circuit consumes 3.2nW during the steady state, aiding the boost converter to achieve an efficiency of 77% at input voltage of 290mV. It was designed in standard 65-nm CMOS process technology and occupies the area of 0.072mm².