A thermoelectric energy harvesting converter with very low voltage self-startup and transformer-reuse technique

Abstract

This paper presents transformer-based self-starting boost converter architecture with low-power maximum power point tracking (MPPT) control for low-voltage thermoelectric generator applications. The minimum working voltage of the proposed boost converter is 40 mV with oscillation through a positive feed-back loop formed by a native MOS and transformer. The oscillation autonomously starts up by thermal noise and VOUT is charged up to 1.2 V by the oscillation so that the control block can operate. After that, the transformer for start-up is reused as an inductor, and the normal boost converter mode is enabled for better energy transfer efficiency. An improved MPPT sensing method is also proposed to simplify the circuit. The prototype chip is implemented in a 0.13-um CMOS process. It operates with an input voltage range of 40 mV to 300 mV and provides a maximum output power of 2.7 mW with a maximum efficiency of 61% at an output voltage of 2 V.In Chapter 1, the purpose and necessity of the Energy Harvesting are explained through a variety of electronics and telecommunications application systems, and three issues of the thermoelectric energy harvesting DC-DC converter, Self-Startup, MPPT and Efficiency are presented. And then, the key ideas of the previous design works are introduced.In Chapter 2, to solve the three issues of the thermoelectric energy harvesting converter, the proposed overall converter topology is introduced. First, both noise triggering and positive feedback loop structure which is composed of native MOS transistor and transformer enable DC-DC converter to start up autonomously, at very low TEG voltage level, 40mV, which is obtained by low temperature difference (1~2/K). Second, the transformer for start-up is reused as an inductor by the proposed structure, so that the normal boost converter mode is enabled for better energy transfer efficiency through overall input voltage range. Finally, the proposed MPPT control scheme can obtain the open c...