20 mV input, 4.2 V output boost converter with methodology of maximum output power for thermoelectric energy harvesting

This paper presents a low-input-voltage boost converter for thermoelectric energy harvesting. In environments with 1-2 K thermal difference, such as in the case of a body-wearable application, TEG generates several micro watts and tens of mV to the boost converter. For the low-input-voltage operation, the power consumption of the control circuit of the proposed boost converter is reduced by using a duty-cycle bandgap reference voltage circuit. In order to maximizing the output power, the input voltage of the boost converter is conventionally set to half of an open voltage of a thermoelectric generator (TEG). In this setting, however, conduction losses such as those of an inductor and a power switch are not considered. The conventional boost converter cannot output the maximum output power. We propose a methodology of the maximum output power considering the conduction losses in the boost converter. The boost converter was implemented in a 0.13 μm CMOS process. The output voltage can be boosted from 20 mV input which is the open voltage of TEG of 1.5 Ω source resistance. The measurement results show that the output power is increased by approximately 10% using the proposed methodology for the open voltage between 20 mV and 100 mV.