System-level Early-stage Modeling and Evaluation of IVR-assisted Processor Power Delivery System

Despite being employed in numerous efforts to improve power delivery efficiency, the integrated voltage regulator (IVR) approach has yet to be evaluated rigorously and quantitatively in a full power delivery system (PDS) setting. To fulfill this need, we present a system-level modeling and design space exploration framework called Ivory for IVR-assisted power delivery systems. Using a novel modeling methodology, it can accurately estimate power delivery efficiency, static performance characteristics, and dynamic transient responses under different load variations and external voltage/frequency scaling conditions. We validate the model over a wide range of IVR topologies with silicon measurement and SPICE simulation. Finally, we present two case studies using architecture-level performance and power simulators. The first case study focuses on optimal PDS design for multi-core systems, which achieves 8.6% power efficiency improvement over conventional off-chip voltage regulator module– (VRM) based PDS. The second case study explores the design tradeoffs for IVR-assisted PDSs in CPU and GPU systems with fast per-core dynamic voltage and frequency scaling (DVFS). We find 2 μs to be the optimal DVFS timescale, which not only reaps energy benefits (12.5% improvement in CPU and 50.0% improvement in GPU) but also avoids costly IVR overheads.

Augmented Transcutaneous Stimulation Using an Injectable Electrode: A Computational Study

Minimally invasive neuromodulation technologies seek to marry the neural selectivity of implantable devices with the low-cost and non-invasive nature of transcutaneous electrical stimulation (TES). The Injectrode® is a needle-delivered electrode that is injected onto neural structures under image guidance. Power is then transcutaneously delivered to the Injectrode using surface electrodes. The Injectrode serves as a low-impedance conduit to guide current to the deep on-target nerve, reducing activation thresholds by an order of magnitude compared to using only surface stimulation electrodes. To minimize off-target recruitment of cutaneous fibers, the energy transfer efficiency from the surface electrodes to the Injectrode must be optimized. TES energy is transferred to the Injectrode through both capacitive and resistive mechanisms. Electrostatic finite element models generally used in TES research consider only the resistive means of energy transfer by defining tissue conductivities. Here, we present an electroquasistatic model, taking into consideration both the conductivity and permittivity of tissue, to understand transcutaneous power delivery to the Injectrode. The model was validated with measurements taken from (n = 4) swine cadavers. We used the validated model to investigate system and anatomic parameters that influence the coupling efficiency of the Injectrode energy delivery system. Our work suggests the relevance of electroquasistatic models to account for capacitive charge transfer mechanisms when studying TES, particularly when high-frequency voltage components are present, such as those used for voltage-controlled pulses and sinusoidal nerve blocks.

Fundamental Responsiveness in European Electricity Prices

We estimate fundamental pricing relationships in selected European day-ahead electricity markets. Using a fractionally integrated panel data model with unobserved common effects, we quantify the responsiveness of hourly electricity prices to two fundamental leading indicators of day-ahead markets: the predicted load and renewable generation. The application of fractional cointegration analysis techniques gives further insight into the pricing mechanism of power delivery contracts, enabling us to measure the persistence of fundamental shocks.

Alignment-Free Wireless Charging of Smart Garments with Embroidered Coils

Wireless power transfer (WPT) technologies have been adopted by many products. The capability of charging multiple devices and the design flexibility of charging coils make WPT a good solution for charging smart garments. The use of an embroidered receiver (RX) coil makes the smart garment more breathable and comfortable than using a flexible printed circuit board (FPCB). In order to charge smart garments as part of normal daily routines, two types of wireless-charging systems operating at 400 kHz have been designed. The one-to-one hanger system is desired to have a constant charging current despite misalignment so that users do not need to pay much attention when they hang the garment. For the one-to-multiple-drawer system, the power delivery ability must not change with multiple garments. Additionally, the system should be able to charge folded garments in most of the folding scenarios. This paper analyses the two WPT systems for charging smart garments and provides design approaches to meet the abovementioned goals. The wireless-charging hanger is able to charge a smart garment over a coupling variance with only 21% charging current variation. The wireless-charging drawer is able to charge a smart garment with at least 20 mA under most folding scenarios and three garments with stable power delivery ability.