Circuits for energy harvesting sensor signal processing

Abstract

The recent explosion in capability of embedded and portable electronics has not been matched by battery technology. The slow growth of battery energy density has limited device lifetime and added weight and volume. Passive energy harvesting from solar radiation, thermal sources, or mechanical vibration has potentially wide application in wearable and embedded sensors to complement batteries. The amount of energy from harvesting is typically small and highly variable, requiring circuits and architectures which are low power and can scale their power consumption with user requirements and available energy. We describe several circuit techniques for achieving these goals in signal processing applications for wireless sensor network nodes such as using Distributed Arithmetic to implement energy scalable signal processing algorithms. In addition, we propose increasing vibration energy harvesting efficiency by eliminating AC/DC conversion electronics, and have investigated self-timed circuits, poweron-reset circuitry, and memory for energy harvesting AC power supplies. These techniques can also be applied to energy harvesting from other sources. A chip will be fabricated to test the proposed circuits.

Subthreshold FIR Filter Architecture for Ultra Low Power Applications

“…In [3], [5] and [7] the authors have reported how such functions can be implemented using subthreshold designs. A standard FIR realization often employed in subthreshold designs is the transversal structure depicted in Fig.1.…”

AC Power Supply Circuits for Energy Harvesting

“…Memory cells for AC supplies must hold state while the supply is low without requiring frequent refreshes which can degrade system performance. A three-transistor DRAM cell with non-destructive read was used along with a singleended sense circuit consisting of two transmission gates, a precharge transistor, and a tri-state buffer [1]. To ensure correct operation, the POR voltage threshold detection can be made dependent on the DRAM as shown in Figure 3.…”

“…Off-chip power electronics increase system cost and volume and limit the effectiveness of vibration-based energy harvesting due to losses incurred when converting from AC to DC voltage (typical efficiencies are between 18%-65% [1]). Interfacing digital circuits directly to the rectified AC energy harvester output avoids the power and cost of complex power electronics.…”

Threshold Voltage Start-up Boost Converter for Sub-mA Applications

“…However, some sources such as solar cells vary dramatically with a 24-hour solar cycle for outdoor applications [5]. The power profile of a solar cell is fluctuating and is different from a regular battery.…”