20 mV input, 4.2 V output SIDO boost converter with low-power controller and adaptive switch size selector for thermoelectric energy harvesting

A low-input-voltage, highly efficient single-inductor-dual-output (SIDO) boost converter fabricated in 0.18 μm CMOS process is presented for thermoelectric energy harvesting. Two key technologies are implemented to accept input voltage down to 20 mV and to achieve 69 % conversion efficiency at 100 mV, which is the highest conversion efficiency reported to date for such a device. The first key is a low-voltage controller based on SIDO architecture with Priority Decision. An input-voltage-referred, novel adaptive switch size selection scheme is also demonstrated as the second key technology. The converter is designed to harvest human body heat using TEG with 20-120 mV open voltage range and to charge a 4.2 V Li-ion battery.