A Dual-Stage Boost Converter Using Two-Dimensional Adaptive Input-Sampling MPPT for Thermoelectric Energy Harvesting

Herein, we present a dual-stage boost converter (DSBC) for ultra-low power (ULP) thermoelectric energy harvesting applications. The proposed DSBC provides improved efficiency over a wide input range by effectively combining inductor-based boost converter (IBC) and transformer-based boost converter (TBC) modes. The converter supports self-startup by using a transformer-based oscillating mode (TOM) and reuses otherwise wasted leakage through energy regenerative recovery. To provide efficient power extraction, we propose a two-dimensional (2D) adaptive input-sampling maximum power point tracking (MPPT) technique. Input sampling is performed adaptively when a relatively large change in the input is detected. Otherwise, the input is finely tracked by 2D MPPT, which controls the on-time of a power switch. The proposed approach provides two main advantages: 1) adaptive sampling prevents unnecessary periodic detachment of the thermoelectric generator (TEG) from the converter and 2) in addition to enhanced tracking resolution, the 2D MPPT controller achieves both MPPT and output regulation simultaneously. To support the DSBC, we present a synchronized zero current switching (S-ZCS) controller. The S-ZCS controller achieves fine tracking and optimization of the on-times of the two power switches for TBC and IBC. The converter was fabricated via a 180-nm CMOS process with a thick top-metal option. Measurements show that the converter achieves energy harvesting with an efficiency of 81.5%. Over a wide input range, from 70 to 450 mV, the efficiency remains higher than 75%, thereby demonstrating the effectiveness of the proposed DSBC with the S-ZCS and 2D MPPT techniques. Self-startup is achieved at a low input voltage of 38 mV.