Large Duty Cycle Research Articles

A novel topology of a non‐isolated bidirectional multiphase single inductor DC–DC converter

AbstractThis paper introduces a novel topology for a non‐isolated bidirectional multiphase single inductor (BMPSIC) DC–DC converter. The proposed BMPSIC requires only a single inductor, irrespective of the number of arms, and features reduced volume and weight compared to the total magnetics needed for a conventional converter with similar ratings. The proposed BMPSIC advantages include a high DC voltage gain without operating on a large duty cycle, voltage stress on the power switches equal to that at the high‐voltage port, easy implementation, and a lower cost for application at high‐power densities. Furthermore, this topology requires only one current and voltage control loop. This paper thoroughly details the steady‐state operating principles of the inductor current continuous mode. It provides theoretical and mathematical analysis, including a comparative analysis of the proposed BMPSIC against earlier DC–DC converters, highlighting the superior performance and efficiency of the BMPSIC. An 8‐kW laboratory prototype, designed as a proof of concept, has been meticulously developed and tested, showcasing the performance of the converter across a broad range of load variations. The efficiency measured for the rated load exceeded 98.2% at the low‐voltage port of 250 V and the high‐voltage port of 400 V. Additionally, the article features Video S1, which illustrates the functioning of the converter.

Effect of Matching Algorithm and Profile Shape on Pulsar Pulse Time of Arrival Uncertainties

For high-precision pulsar timing analysis and low-frequency gravitational wave detection, it is essential to accurately determine pulsar pulse times of arrival (ToAs) and associated uncertainties. To measure the ToAs and their uncertainties, various cross-correlation-based techniques can be employed. We develop methodologies to investigate the impact of the template-matching method, profile shape, signal-to-noise ratio of both template and observation on ToA uncertainties. These methodologies are then applied to data from the International Pulsar Timing Array. We demonstrate that the Fourier domain Markov chain Monte Carlo method is generally superior to other methods, while the Gaussian interpolation shift method outperforms other methods in certain cases, such as profiles with large duty cycles or smooth profiles without sharp features. However, it is important to note that our study focuses solely on ToA uncertainty, and the optimal method for determining both ToA and ToA uncertainty may differ.

A Novel Three-Winding Coupled Inductor-Based High Step-Up DC-DC Converter for Renewable Energy Application

This paper presents a novel nonisolated high step-up dc-dc converter for renewable energy generation system. The converter combines a three-winding coupled inductor, voltage multiplier cells, and two power switches with simultaneous operation. Compared with existing high step-up converters, the proposed converter can achieve high voltage gain under a low number of turns ratio while avoiding a large duty cycle. Moreover, the passive clamp circuit recycles leakage inductor energy and reduces the voltage spike of switches. Continuity of input current and existence of a common ground between the input energy source and load make the converter suitable for renewable energy applications. Also, the proposed converter shares high voltage gain with low voltage stress on semiconductors (switches/diodes), improved compactness and high efficiency. The operating principles and steady-state analysis of the proposed converter are illustrated. Then the theoretical efficiency analysis, and performance comparison with other converters are discussed. Finally, a 200 W prototype with 380 V output voltage is established based on the design guidelines, and experimental results verify the accuracy of the theoretical analysis.

Numerical simulation and experimental analysis on nanosecond laser ablation of titanium alloy

Nanosecond lasers are widely used in the ablation of metal materials, and the exploration of the ablation mechanism has never stopped. In this study, a three-dimensional finite element model of heat transfer and flow coupling was established with Ti6Al4V alloy as the research object. The model simulated the heat transfer in the ablation process by setting heat conduction, convection, and radiation flux. The surface tension, recoil pressure, gravity, buoyancy, and thermocapillary force were used as driving forces to induce fluid flow in the molten pool. The results show that different scanning paths lead to different degrees of heat accumulation in the model. However, due to the large duty cycle used in the simulation, the model has enough cooling time. The effect of heat accumulation is limited. Among the reasons for inducing liquid flow in the molten pool, thermal capillary flow dominates. The maximum flow velocity appears at the edge of the molten pool, and the flow velocity gradually decreases from the surface to the inside. To study the interaction between laser parameters and groove size, the experimental parameters were designed by response surface methodology. The results show that the influence of scanning times, scanning speed, and repetition frequency on groove depth gradually decreases. The interaction between scanning speed and scanning times has an obvious effect on the groove width.

Wide zero‐voltage switching range full‐bridge converter based on adjustable parallel current

AbstractAiming at the problems of narrow ZVS range, large duty cycle loss, and severe voltage oscillation of phase‐shift‐controlled full‐bridge converters, this paper proposes a converter that realizes ZVS by adjusting the parallel current. No additional series inductor is required, avoiding large duty cycle loss and weakening voltage oscillations on the secondary side. The converter with small duty cycle loss can use a transformer with a larger turns ratio, which can reduce the voltage stress of the secondary diodes and the filter inductor current ripple. The parallel current required to realize ZVS is analyzed theoretically considering the influence of leakage inductor energy on ZVS. A comparative experiment between the proposed converter and the conventional full‐bridge converter is carried out to verify the performance of the proposed converter.

Voltage controlled ring oscillator with large frequency range and variable duty cycle

Voltage controlled ring oscillator with large frequency range and variable duty cycle

Analytical evaluation of single‐input dual‐output based integrated luo‐buck converter for BLDC motor

AbstractA single‐input dual‐output (SIDO) converter is proposed in the research article for usage in electric vehicle (EV) applications. The main objectives of the proposed integrated Luo‐Buck converter (ILBC) based BLDC drive system are to develop a multi‐purpose converter with low complexity and high efficiency, as well as to reach the rated speed of BLDC‐based vehicles. The multi‐output converter is generally employed in EV applications because of the primary load and extra auxiliary loads like sensors, power steering, headlights, and so on. The proposed system achieves both of the aforementioned objectives. As there are just two switches, fewer gate driver circuits are required, which indirectly lowers the complexity of the circuit. Since they do not require large duty cycles, ILBC switches experience less voltage and current stress. The switches can only be used at duty cycles of 60% and 30%. For design purposes, output filter capacitor sizes are likewise maintained to a minimum. The 1.2 kW BLDC is powered by the ILBC, which has a maximum efficiency of 96.16%, in order to validate the suggested system using the hardware prototype model. The rated speed can be attained with the least amount of timing. Additionally, the suggested approach lessens voltage and torque ripple.

Interleaved converter with ultra-high voltage gain for DC microgrid application

ABSTRACT In this paper a new non-isolated converter with ultra-high voltage gain is presented. The proposed converter utilises coupled inductors, lift circuits and interleaved technique to convert low-level DC voltages to high-level DC voltages without high turn ratios or large duty cycles. Winding-cross-coupled inductors are employed to raise the voltage ratio. The voltage and current stress of semiconductors are reduced, which causes low conduction losses and improves the efficiency. The way the clamp circuit is used limits not only the spike voltages but also effect on the conversion ratio of the proposed converter and make it larger. The main features of this converter are high voltage gain, low voltage stress of semiconductors, low reverse recovery of diodes, low input current ripple, low conduction loss and high efficiency. A prototype of the proposed circuit is constructed in laboratory at 100 W converting 20 V to 450 V. The experimental results are compared with theoretical analysis which verifies them.

Temperature Sensing Characteristics of Two Fundamental Solitons in a Glycerin-Filled Microstructured Optical Fiber

In this paper, the temperature sensing characteristics of two fundamental solitons in a glycerin-filled six-hole microstructured optical fiber (MOF) were systematically exploited through experiment and simulation. The six-hole MOF has a large duty cycle, which can increase the space to fill the temperature-sensitive material glycerin for improving the temperature sensing sensitivity. By detecting the center wavelength shift of 3dB bandwidth of two fundamental solitons at 1050 nm, 390 mW, a maximum sensitivity of -0.601 nm/ °C was obtained based on the first fundamental soliton and -0.598 nm/ °C was obtained based on the second. Simulation results combined with the experimental results showed that the higher the average pump power, the higher the temperature sensitivity, and the temperature sensitivity of the first was slightly higher than that of the second. The difference in sensing characteristics between the two fundamental solitons discovered in this study could provide a novel solution to solve the cross-sensitivity of dual-parameter sensing. To the best of our knowledge, this is the first research about utilizing two fundamental solitons for temperature sensing, which broadens the boundary of the nonlinear-based sensors, and has promising prospects in the fields of national defense security, disease monitoring, agriculture production, etc.

Design and Analysis of Novel Cascaded Topology with LD Cell for Micro-source Grids

This paper focus on DC-DC converter called Novel Cascaded topology. This converter lies in the category of Non-Isolated DC-DC boost converters with upgraded voltage gain based on conventional topology with LD cell for micro-source grids. The proposed novel cascaded topology increases the voltage boost ability. There are some merits of our proposed topology that includes small voltages stresses across the switch, as well as upgraded gain. We prefered to use switch having small voltage rating as well as small resistance in ON-mode (RDS-ON), it leads to provide high efficiency. In our cascaded topology with LD cell,we did not use large duty cycle, coupling inductors as well as transformer.We will utilize the Continuous Conduction Mode (CCM) for the analysis of proposed novel cascaded topology. This topology is designed to operated on 12V supplying voltage, 55% duty cycle, 265W output power and frequency of 12KHz. The continous conduction mode (CCM) has been analyzed theoretically as well as practically based derived equations. The novel cascaded converter has been simulated in PSIM as well as MATLAB/SIMULINK, while explanations of the overall results are provided based on PSIM.

A New Fifth-Order Boost Converter With Dual Operating Modes and Wider Conversion Ratios for Renewable Energy Applications

Conventional DC-DC converters for renewable energy systems work in large duty cycle conditions, which will lead to the inductor saturations and decrease the system efficiencies and stabilities. In this brief, a new fifth-order boost converter, which can work in dual operating modes when different control technologies are adopted, is proposed. To obtain a wider conversion ratio, the required duty cycle for the proposed converter with synchronous controller is smaller than 0.333 while with interleaved controller is smaller than 0.5. Also, dual modes of this converter both have lower switches voltage stress. Then, the inductor saturation issues can be avoided and the system efficiencies and stabilities can be improved. Besides, the lower topological order and simple grounded structure of this converter are benefit to reduce the modeling complexity, topology volume and system noises. Detailed analyses, comparisons and prototype are implemented to study the improved conversion ratio, efficiency and power density of the proposed converter in-depth, and to validate its feasibilities for renewable energy applications.

New Multi-Leg Converter for DC Microgrid with Two Duty Cycles

In recent times, important contributions and the incorporation of renewable sources, such as photovoltaic, fuel cells, etc., are the main reasons for the popularity of DC microgrids. Integrating renewable sources into the microgrid requires high-voltage, high-efficiency DC-to-DC converters. Without modification, traditional converters are not suitable for achieving the required voltage in microgrid applications, due to the requirement for a large duty cycle, inductor resistance, voltage rating of switches, reverse recovery of the diode, high current rating inductors, etc. Various converters based on the circuitry of voltage multipliers, switched inductors/capacitors, coupled inductors, transformers, etc., have been proposed in the literature and have their drawbacks. In this paper, to realize significant voltage gain with two duty cycle controls, a new multi-leg (ML) converter is recommended as a solution for use in DC microgrids. The converter is designed by incorporating multiple legs into the boost converter. The implications of the proposed converter are reduced device voltage stress, small inductors and capacitors, two-duty cycle control, triple mode operation, single-stage conversion, etc. The proposed converter’s power circuits, mode of operation, and design equations of the converter are presented. The non-ideal model of the proposed converter is discussed, and efficiency is analyzed. The effect of unequal insurance on the operation of the converter is discussed. Comparative studies of converters are provided to draw attention to the benefits of the converter. The results of the experiments are shown to prove that the analysis and performance of the converter are correct. The discontinuous mode of operation and unequal inductance case of the converter are studied with the help of a simulation model.

Structural Optimization of Graphene Triangular Lattice Phononic Crystal Based on Dissipation Dilution Theory.

Nanomechanical resonators offer brilliant mass and force sensitivity applied in many fields, owing to a low mass m and high-quality factor Q. However, in vibrating process, resonant energy is inevitably dissipated. Typically, quality factor does not surpass the inverse of the material loss angle φ. Recently, some exceptions emerged in the use of highly stressed silicon nitride material. As yet, it is interpreted that the pre-stress seems to “dilute” the intrinsic energy dissipation according to the Zener model. Is there any other material that could further break the 1/φ limit and achieve higher quality factors? In our previous research, through theoretical calculation and finite element simulation, we have proved that graphene’s quality factor is two orders of magnitude larger than silicon nitride, on account of the extremely thin thickness of graphene. Based on this, we further optimize the structure of phononic crystals to achieve higher quality factors, in terms of duty cycle and cell size. Through simulation analysis, the quality factor could improve with a larger duty cycle and bigger cell size of triangular lattice phononic crystal. Unexpectedly, the Q amplification coefficient of the 3 × 5-cell structure, which is the least number to compose a phononic crystal with a central defect area, is the highest. In contrast, the minimal cell-number structure in hexagonal lattice could not achieve the brilliant dissipation dilution effect as well as the triangular one. Then we consider how overall size and stress influence quality factor and, furthermore, compare theoretical calculation and finite simulation. Lastly, we start from the primitive 3 × 5 cells, constantly adding cells to the periphery. Through simulation, to our surprise, the largest Q amplification coefficient does not belong to the largest structure, instead originating from the moderate one consisting of 7 × 13 cells.

Impact of homodyne receiver bandwidth and signal modulation patterns on the continuous-variable quantum key distribution.

In continuous-variable quantum key distribution (CV-QKD), the key information are encoded on quadratures of the optical field, which are measured via balanced homodyne detector (BHD). The bandwidth of the BHD is one of key parameters for precise characterization of quantum states. We establish a theoretical model to analyze the impact of the BHD bandwidth and signal modulation patterns on the channel parameters estimation of CV-QKD systems. Based on the proposed model, the secure key rate of a practical CV-QKD system under different BHD bandwidths and signal modulation patterns are investigated. Our results show that insufficient BHD bandwidth will result in wrong estimate of the transmission loss and excess noise, which significantly affects the performance of CV-QKD systems. Given the BHD bandwidth, there exists an optimal signal repetition rate that maximizes the secure key rate. The BHD bandwidth requirement of the QKD system increases with the transmission distance for large duty cycle pulse. Furthermore, the root raised-cosine pulse signal modulation performs better than the square pulse signal modulation in general.

A Three-Leg-Based Full-Bridge Converter With Wide Input Voltage Range

Traditional phase-shift full-bridge converters are popular in industrial applications due to the advantages of simple design, fixed-frequency control and soft switching. However, a large duty cycle variation range is required in applications with a wide input voltage range, which can cause loss of soft switching range, excessive circulating currents and output current ripple. This article introduces a three-leg converter that is a hybrid combination of two full-bridges. The current and power of the two transformers in the converter are shared automatically by adopting the symmetrical structure and modulation, and output current ripple is suppressed by the superposition of the two transformer voltages. The circulating current is minimized in the proposed converter that the conduction loss is reduced. By adding two auxiliary switches on the secondary side, zero-voltage switching and zero-current switching of all switches can be achieved to maintain high efficiency in a wide range. An experimental prototype rated at 1 kW is designed to convert 220–460 V input to 100 V output. The experimental results show that the proposed converter can achieve high efficiency over a wide input voltage and load range.

99%—Efficient, interleaved bidirectional DC‐DC converter with new interleaved PWM method of parallel‐connected Mosfets

AbstractA new high efficiency interleaved pulse‐width modulation (HE‐IPWM) method using parallel‐connected Mosfets is presented. The IPWM is evaluated using a bidirectional DC‐DC converter for charging and discharging a battery. The results show an excellent DC voltage gain without an extremely large duty cycle. Compared with conventional pulse‐width modulation (CPWM), the IPWM reduces by half the ripple of the battery current. The current ripple of IPWM is four times higher of the switching frequency, while CPWM is two times higher. The proposed interleaved strategy also double the inductor current ripple frequency, whereas in general, is equal to the switching frequency. As a result, the use of the IPWM reduces the weight and size of inductor design. Furthermore, IPWM provides the best battery current ripple at the duty cycle close to 25%. The operating stage, mathematical analyses, and design guidelines of the two proposed modulations are explained in detail. The IPWM experimental results of a 250‐W prototype confirmed the circuit performance. The maximum efficiency of 98.9% is obtained at 250 W for boost mode and 99% for buck mode.

A 15 mV-input and 71%-efficiency boost converter with 22 mV output ripple for thermoelectric energy harvesting application

This paper presents a self-startup and ultra-low-voltage boost DC–DC converter for the thermoelectric energy harvesting application. A two-stage auxiliary boost startup circuit with a multi-stage voltage multiplier and a large duty cycle circuit is adopted to achieve a minimum self-startup voltage of 155 mV. And the system can sustain the operation at a 15 mV input. The maximum power point tracking (MPPT) with a combination of coarse and fine frequency tuning is proposed to improve the tracking accuracy with small output ripples of 22 mV. Moreover, the zero current switching (ZCS) scheme combined with the MPPT achieves a peak end-to-end efficiency of 71%, providing a regulated 1.25V output with a maximum power of 540 μW.

Investigation of boiling behaviors in vapor chambers in response to transient heat input profiles

Vapor chambers are being increasingly utilized as passive heat spreaders in various high-power density thermal management architectures. Particularly, in applications involving power electronics packaging, there is a need to understand and predict thermal performance of vapor chambers under different transient heat loads. It is known that boiling could occur in the wick structure of a vapor chamber at the location of heat input if sufficiently high heat fluxes are directly imposed on the chamber wall. Prior experimental studies that characterize the steady state thermal resistance of vapor chambers versus input power can only identify the behavior before and after the transition to boiling. However, because the initiation of boiling is a discrete event that occurs during the transient powering up, it is critical to understand how boiling behaviors will affect the performance of the vapor chamber in response to the transient heat input profile characteristics. Furthermore, currently available transient vapor chamber modeling efforts do not consider the occurrence of nucleate boiling, precluding their usage for applications where boiling is likely to occur. In this paper, we experimentally characterize the occurrence and effect of nucleate boiling in a vapor chamber coupled with an air-cooled heat sink, subject to various transient heat input profiles. The long-time step response behaviors are first studied for ten on–off cycles, at different on-powers, to illustrate the complete temperature response to a steady state in each cycle. For a range of intermediate powers, an interesting phenomenon is observed, where boiling occurs in every alternate cycle; we identify this range as the transition regime of boiling incipience in the vapor chamber. We further investigate the transient response to a pulsed heat input for various on-times ranging three orders of magnitude from 0.1 s to 400 s, and with two duty cycles (0.25 and 0.5), while keeping either the on-power or the average power constant. For a fixed on-power, lower on-times (0.1 s – 2 s) do not cause any boiling, but for longer on-times (≥ 20 s), cases with lower duty cycles led to occurrences of boiling incipience. Furthermore, for a fixed average power, a higher on-power at a lower duty cycle is more likely to cause boiling, which interestingly leads to an even lower mean steady temperature compared to cases with lower on-power and larger duty cycle. These studies provide insights into the nature of boiling incipience in vapor chambers for their usage under realistic transient input powers mimicking power electronics.

Full Soft-Switching Ultra-High Gain DC/DC Converter Using Three-Winding Coupled-Inductor with Modular Scalability for Renewable Energy Applications

This paper proposes a new non-isolated single-switch DC/DC converter with an ultra-high voltage gain, low input current ripple, low voltage stress, soft-switching operation, and modular scalability for renewable sources applications. Here, with the help of a Three-Winding Coupled-Inductor (TWCI) and Voltage Multipliers circuits, ultra-high voltage gains can be achieved without needing a large duty cycle. A regenerative clamp capacitor recycles the energy stored in the leakage inductor; thus, the maximum voltage across the single power switch is restricted. Moreover, at the turn-on instant of the power switch, a Zero Current Switching (ZCS) condition is achieved. By designing a resonant tank, the switched current value of the main switch at the turn-off instant is reduced significantly. Also, the leakage inductor of the TWCI helps all converter diodes to operate under the ZCS condition. Due to full soft-switching performance, the introduced topology can provide a wide output voltage range under a high conversion efficiency. The steady-state analysis and comprehensive comparisons are provided in this paper. A 160 W prototype with 24 V input and 250 V output voltage is developed to validate the theoretical analysis. Due to ZCS operation and low voltage stress (VDS ≈ 40 V), the power loss portion of the MOSFET is low. Moreover, the maximum voltage stresses of the diodes are measured 40 V, 60 V, 90 V, and 110 V that are well below the output voltage. Furthermore, at the full-load condition, the input current ripple is about 20 % and the measured efficiency is about 96.3%.

Soft-switched high step-up DC/DC boost converter for distributed generation

Conventional boost converters are practically operated with maximum voltage gain of 5, as an extremely large duty cycle in excess of 80% results in reverse recovery problem of boost diode and large conduction losses in power devices, inductors and filter capacitors. High step-up boost converters, as required in distributed generation systems using green energy sources, are nowadays drawing prime attention of power electronics engineers. In recent years, wide research is going on to operate the switching devices under soft-switched condition, so that, the converters can be made more compact by operating at high switching frequency and simultaneously maintaining high efficiency. In present work, a new soft-switched high step-up coupled-inductor boost converter is proposed to meet the demands of distributed generation systems. Performance of the proposed converter is verified by a prototype laboratory model and behaviour of the converter is found to confirm the theoretical analysis.