Deconvolving Protected Signals

In advanced technology nodes, BEOL interconnect stack geometry has become a key lever for design enablement. The rapid increase of interconnect RC leads to not only performance loss from interconnect delay increase, but circuit power and area degradation as well. Thus, optimization of BEOL dimensions (i.e., wire width, spacing and thickness subject to a given layers pitch constraint) is crucial to achieve better product performance, power and area. However, it is not obvious how to optimize BEOL dimensions, especially in sub-10nm nodes. In this work, we study BEOL interconnect stack geometry by exploring wire aspect ratio (AR) and wire line-space duty cycle (DC). We perform SPICE-based analyses of timing path delays to find delay- or power-optimal (AR,DC) combinations, and also perform block-level studies with placed and routed designs. Based on our experimental results, we provide various insights on BEOL stack geometry: (i) optimal (AR,DC) for a given wire pitch with respect to power and delay; (ii) sensitivities of optimal (AR,DC) to circuit parameters (e.g., driver strength, input slew, output load, wirelength); (iii) optimal (AR,DC) when multiple interconnect layers are considered; and (iv) potential impacts of BEOL stack optimizations within future design-aware manufacturing and/or manufacturing-aware design methodologies.

Nanocrystalline copper coatings were jet electrodeposited using a square-wave pulse current with three duty cycles (30%, 50% and 70%) and a direct current condition. The effect of the duty cycle on the surface morphology, microstructure, grain growth and mechanical performance of the copper coatings was examined. The experimental results revealed that a decrease in the duty cycle significantly improved the coating surface morphology and microstructure. It was shown that a pulse current at a low duty cycle during jet electrodeposition effectively generated a nanocrystalline structure in the coating and improved the mechanical properties. At a low (30%) duty cycle during pulse current electrodeposition, coatings with a fine and smooth surface and dense microstructure were produced with a minimum grain size of 25 nm, microhardness of 2.37 GPa and tensile strength of 712 MPa.

The influence of duty cycle on ozone generation and discharge characteristics was investigated experimentally using volume dielectric barrier discharge in both synthetic air and pure oxygen at atmospheric pressure. The discharge was driven by an amplitude-modulated AC high voltage–power supply producing TON (a single AC cycle) and TOFF periods with a widely variable duty cycle. The experimental results show that the energy delivered to the discharge during each AC cycle remains roughly constant and is independent of feed gas, duty cycle and TOFF. Both average discharge power and ozone concentration show an initial linear increase with duty cycle, and deviate gradually from linearity owing to an increase in gas temperature at higher duty cycles. Nevertheless, ozone yield remains nearly constant (45.7 ± 3.5 g/kWh in synthetic air and 94.7 ± 3.1 g/kWh in pure oxygen) over a wide range of applied duty cycles (0.02–1). This property can be conveniently employed to develop a unique ozone generator with a widely adjustable ozone concentration and simultaneously a constant ozone yield. Additionally, the discharges in synthetic air and pure oxygen have similar electrical characteristics; however, there are observable differences in apparent luminosity, which is weak and white-toned for synthetic air discharge, and bright and blue-toned for pure oxygen discharge.

The application of wide band-gap power electronic devices brings more challenges to insulating packaging technology. Knowing the influence of applied voltage parameters on insulation performance is helpful to evaluate the insulation condition of electric power equipment. In this paper, the effect of repetitive square wave voltage duty cycle on the growth characteristics of electrical trees in epoxy resin was studied. The experimental results show that the square wave voltage duty cycle has a significant influence on treeing features. The electrical tree proportion initiation has shown a decreasing trend, and the shape of the electrical tree changes from pine-like to branch-like by increasing the duty cycles. The length and damaged area of electrical tree increased with the increase in the duty cycle up to 10% and then decrease by increasing the duty cycle higher than 30%. It indicates that a low duty cycle will enhance the electron injection and accumulate space charges and thus accelerate electrical tree development. Under short duty cycles, the electric field due to the shielding effect near the needle tip suppresses the electrical tree growth, which results in treeing growth stagnation. The obtained results are helpful to keep these parameters in mind during the design of epoxy-based insulation such high-voltage rotating machines and power electronic device packaging.

A method to control the duty cycle of a time-of-flight mass spectrometer is described. The method relies on one or more ion gates placed in the beam path that have the function to transmit or stop the beam. These ion gates can switch from the open state to the closed state in tens of nanoseconds and effectively select portions of the mass range. The method is useful in circumstances where recording the complete mass spectrum is not an essential requirement, for example, in the analysis of known compounds where sensitivity and speed of operation are more important. It will be of benefit for applications in separation sciences with techniques involving fast chromatographic separations, where hundreds of mass spectra may be required per second. In such circumstances analytical identification may require only a limited number of masses (or mass regions) to be continuously monitored. Improvement of the duty cycle is particularly important for orthogonal-acceleration time-of-flight (oa-TOF) mass spectrometry instruments whose performance suffers from a low duty cycle. The duty cycle is not a constant for an instrument design but is a mass-dependent function and is least for smaller masses. The method described here is capable of raising the duty cycle to 100%. A theory is developed for one or more ion gate arrangements, for both linear- and reflectron-TOF systems. For a two-gate system the relationship between the positions of the first and second gates is described by a '2/3 rule'. Experimental results are shown for one-gate and two-gate operation, both in linear and in reflectron modes of operation, on an oa-TOF system built in-house.

Ni–SiCp composite coatings were synthesised by pulse electrocodeposition with different duty cycles. The grain size and the SiC particle content were found to increase with increasing duty cycle, and a maximum microhardness value was obtained at a duty cycle of 50%. Based on the results of electrochemical impedance spectroscopy, an equivalent circuit model was used to estimate the charge transfer current of the electrodeposition process at different duty cycles. The peak charge transfer current was found to decrease with increasing duty cycle. An analytical volume fraction equation was also applied to predict the content of embedded SiC particles in the composite coatings. The trend of the predictions was in consistent with the experimental results.

Experiments and simulations of QCW Yb:YAG laser with consideration of transient temperature

Under unbalanced dc links, the control of a three-phase Vienna rectifier is challenging. To deal with the unbalanced dc links, the optimal switching sequence model predictive control (MPC) regulates the neutral-point (NP) voltage through preselecting a redundant vector and grid current by reconstructing duty cycles of the optimal switching sequence. However, its one-redundant-vector-per-control-interval characteristic leads to large NP voltage ripple. To solve this problem, in this article, a model predictive duty cycle control method is proposed for three-phase Vienna rectifiers under unbalanced dc links. First, we study the impacts of duty cycles on the variations of instantaneous current, and then, the three-phase duty cycles are derived by predefined objective function minimization. Second, considering both the operational characteristics and unbalanced dc links of the Vienna rectifier, a new modification method for duty cycles is presented. This method ensures the grid current quality and decouples the control of grid current and NP voltage. Finally, an MPC-based NP voltage control strategy is proposed to reduce the NP voltage ripple. Experimental results demonstrate that the presented method can effectively reduce the NP voltage ripple.

In this paper, a novel nonisolated interleaved high step-up DC-DC converter is proposed based on the coupled inductor and voltage multiplier cell (VMC) methods. Due to the interleaved structure, its input current ripple is low. The low input current ripple and also high power efficiency make the proposed converter suitable for renewable energy applications like photovoltaic (PV) and fuel cell (FC) power generation systems. The windings of the coupled inductors are combined with VMCs to further increase the output voltage with a low power switch’s duty cycle. This combination also leads to obtaining a flexible voltage gain that can be adjusted by coupled inductors’ turns ratio and power switches’ duty cycle. The voltage peaks over semiconductors are much lower than the output voltage. Therefore, low-rated semiconductors can be used for the implementation of the proposed converter, which can reduce the cost and volume. Generally, high voltage gain, low voltage, current stress of power switches, low input current ripple, high efficiency, common ground between the input and output ports, and a low number of elements are the main benefits of the suggested structure. The operation principle, steady-state analysis, and comparison with other converters are presented to show the advantages of the suggested converter. Also, a prototype is built, and the experimental results are presented to prove the theoretical analysis. This prototype is implemented with 200 W rated power, 25 V∼400 V voltage conversion, and 50 kHz switching frequency. Additionally, the efficiency is measured at 95.3% at the rated power.

In this paper, a field programmable gate arrays (FPGA) technique applied to a forward converter with synchronous rectification (SR) is utilized to design a pulse-width-modulation (PWM) proportional-integral-derivative (PID) controller, along with protection peripherals. With only one comparator and without any analog-to-digital converter (ADC), the information on the feedback output voltage is entirely obtained according to a counter. In the continuous current mode (CCM), the next duty cycle is determined by the present duty cycle, and in the discontinuous current mode (DCM) used to reduce power dissipated at light load, the next duty cycle is also decided by the present duty cycle but with some modifications which reduce the effect of variations on the calculated duty cycle. In this paper, the detailed operation of this control topology is illustrated, along with some experimental results to verify its effectiveness.

The modeling and control strategies for proton exchange membrane (PEM) fuel cells are presented. Two different pulsing methodologies were designed and implemented in Fuel Cell Laboratory at Florida Atlantic University in order to increase the efficiency and performance of PEM fuel cells. The schedule experiments for each method comprised of varying the pulse amplitude, the frequency and the duty cycles. The amplitude variations were controlled by a pressure regulator on the pulsed air source; frequency and duty cycle changes were implemented using computer software in conjunction with A/D, D/A, timer and electronic circuits. The experimental results are promising. Further experimental work to improve the efficiency of PEM fuel cells based on an intelligent hybrid control strategy is under investigation.

Abrasive Flow Machining (AFM) process has been a useful technique for deburring and polishing of the surface and edges through the abrasive laden media. The surface material has been removed in form of micro chips due to abrasion action of sharp cutting edges abrasive particles. A large amount of force and energy has been lost due to frictional forces between the surface and abrasive particles in AFM process. A new hybrid form of AFM process named as thermal additive centrifugal abrasive flow machining (TACAFM) has been discussed in the present investigation, which utilized the spark energy to melt the surface material. A lesser amount of force has been required by the abrasive particles to remove the molten material from the surface and also minimized the energy loss. In the present investigation central composite design response surface methodology has been used to plan and conduct the experiments using Design Expert® 11 software. Experiments have been performed to analyze the effect of input process variables such as current intensity, duty cycle, abrasive concentration, rotational speed of the electrode and extrusion pressure on scatter of surface roughness, micro hardness and % improvement in Ra of the workpiece. Also the finished surface of the brass work piece has been characterized for the microstructure study using SEM and XRD analysis. From the experimental results it has been found that duty cycle has the most significant effect towards Scatter of surface roughness with a contribution of 17.5 % while current has been contributed largest as 85.17 % towards micro hardness. Also it has been observed that current has contributed largest as 21.88% against the % improvement in Ra. The optimum scatter of surface roughness, micro hardness and % improvement in Ra has been observed as 0.15 µm, 345.95 HV and 39.52 % respectively.

The modularized equalizers use additional components among the modules in the long series-connected lithium-ion battery string. In these approaches, the overall systems are heavy, bulky, and high-priced. Furthermore, the losses related to additional components decrease the system efficiency. To avoid these problems, a modularized equalizer, which has no additional components among the modules, is required. This paper proposes a novel control scheme using the magnetizing energy of the multi-winding transformer for the module equalization. In this scheme, the high duty cycle is applied to the module where the voltage is higher than the reference voltage and the low duty cycle is applied to the module where the voltage is lower than the reference voltage. Due to the different duty cycle, more electric charges are transferred from high voltage module to the low voltage module during the turn-off switching interval. Using the proposed control scheme, the equalizer system does not suffer from the size, cost, and loss related to the modularization. The experimental results are provided to verify the effectiveness of the proposed modularized equalizer.

Capacitor voltage imbalance is a well-recognized issue for neutral-point-clamped (NPC) converters. Hardware solutions increase the system cost and complexity, while existing software solutions generally involve sophisticated algorithms, making it difficult to extend them for more voltage levels and full power-factor range. In this article, a new control method, termed direct-switch duty-cycle control (DSDCC), is proposed and generalized for the grid-connected <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -level NPC converter. This method has the advantage of balancing the capacitor voltages for the full range of power factors on the ac side. The main significance of the DSDCC is that it can achieve near-optimal performance with simple and fast control implementation for two reasons. First, the DSDCC is based on the model directly concerning switches’ duty cycles, which can easily generate gating signals for the converter with only one carrier. Second, instead of searching for an optimal control solution, near-optimal switch duty cycles are derived such that the controller design can be greatly simplified. The extremely fast execution time of the proposed control algorithm is only about 3% of that of model predictive control for five-level NPC (5L-NPC) converters. Experimental results are included to validate the proposed method with a 5L-NPC converter.

This paper analyses the LLC resonant converter below its resonant frequency, because ZVS in MOSFETs and ZCS in output diodes can be achieved in this area and also the converter operates like BOOST converter. Simultaneous switching frequency and pulse width modulation techniques in steadey state are applied for controlling of this converter. In this approach, two control variables are used, which gives designers one more degree of freedom in comparison to the conventional techniques. finally the voltage gain of this converter is defined based on swithing frequency and duty cycle and quality factor. To verify the given analysis the LLC resonant converter has been simulated under the wide output power range of 20–200 W. To regulate the output voltage at 100 V, input voltage has been choosen at 400V and its switching frequency varies in 200–400 kHz and duty cycle in 0.1–0.9. more over experimental results have been presented.