A 95mV-startup step-up converter with Vth-tuned oscillator by fixed-charge programming and capacitor pass-on scheme

Harvesting energy from the environment by using a thermoelectric generator (TEG) or photovoltaic cells provides a solution for battery-free sensor networks or electronic healthcare systems. In these systems, the harvested energy is supplied at a very low voltages, requiring a low-startup-voltage power circuit for kick-start from low voltage. A previous sub-100mV-startup-voltage boost converter was implemented by using a mechanically assisted step-up process that needs vibration at startup and the application is rather limited. In this paper, a 95mV startup voltage step-up converter without any mechanical stimulus extends the applicability of energy harvesting. The circuit converts a 100mV input to a 0.9V output with 72% conversion efficiency without any external clocks or mechanical switches. A capacitor pass-on scheme eliminates an additional external output capacitor that functions only at the startup.