scholarly journals Three-Output Flyback Converter with Synchronous Rectification for Improving Cross-Regulation and Efficiency

Electronics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 430
Author(s):  
Chung-Ming Leng ◽  
Huang-Jen Chiu
Keyword(s):  
Maximum Efficiency ◽  
Heavy Load ◽  
Leakage Inductance ◽  
Flyback Converter ◽  
Conduction Loss ◽  
Analog Ic ◽  
Light Load ◽  
Load Imbalance ◽  
Extreme Load ◽  
Synchronous Rectification

This paper proposes a single stage alternating current/direct current (AC/DC) flyback converter which contains three output windings with synchronous rectification (SR) function to achieve better cross-regulation and efficiency. Because the three output windings are stacked in a series structure and use synchronous rectification instead of diode rectification, the forward conduction loss of the diode can be eliminated, and the current of each winding can flow bilaterally. Therefore, the energy of leakage inductance can be dissipated through heavy load winding without transient overvoltage in light load winding. Compared with existing methods in the literature, the proposed converter can be realized by simple analog IC with fewer winding turns. Finally, under the extreme load imbalance condition, the cross-regulation is still within ±2.26%. The maximum efficiency of the proposed converter reaches 87%, which is about 3% higher than the conventional Schottky diode solution’s efficiency. The circuit structure and operation principle are described. A practical prototype and experiment results are implemented to verify the feasibility of the proposed converter.

scholarly journals Association Control Based  Load Balancing in Wireless  Cellular Networks Using  Preamble Sequences

2021 ◽  
Author(s):  
◽  
Ankit Chopra
Keyword(s):  
Load Balancing ◽  
Cellular Networks ◽  
Network Capacity ◽  
Correlation Property ◽  
User Association ◽  
Heavy Load ◽  
Implicit Information ◽  
Light Load ◽  
Load Imbalance ◽  
Radio Resources

<p>The efficient allocation and use of radio resources is crucial for achieving the maximum possible throughput and capacity in wireless networks. The conventional strongest signal-based user association in cellular networks generally considers only the strength of the signal while selecting a BS, and ignores the level of congestion or load at it. As a consequence, some BSs tend to suffer from heavy load, while their adjacent BSs may carry only light load. This load imbalance severely hampers the network from fully utilizing the network capacity and providing fair services to users. In this thesis, we investigate the applicability of the preamble code sequence, which is mainly used for cell identification, as an implicit information indicator for load balancing in cellular networks. By exploiting the high auto-correlation and low cross-correlation property among preamble sequences, we propose distributed load balancing schemes that implicitly obtain information about the load status of BSs, for intelligent association control. This enables the new users to be attached to BSs with relatively low load in the long term, alleviating the problem of non-uniform user distribution and load imbalance across the network. Extensive simulations are performed with various user densities considering throughput fair and resource fair, as the resource allocation policies in each cell. It is observed that significant improvement in minimum throughput and fair user distribution is achieved by employing our proposed schemes, and preamble sequences can be effectively used as a leverage for better cell-site selection from the viewpoint of fairness provisioning. The load of the entire system is also observed to be balanced, which consequently enhances the capacity of the network, as evidenced by the simulation results.</p>

scholarly journals A Quasi-Resonant ZVZCS Phase-Shifted Full-Bridge Converter with an Active Clamp in the Secondary Side

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2868 ◽  
Author(s):  
Duong Tran ◽  
Nam Vu ◽  
Woojin Choi
Keyword(s):  
Pulse Width Modulation ◽  
Maximum Efficiency ◽  
Load Range ◽  
Leakage Inductance ◽  
Zero Voltage Switching ◽  
Turn On ◽  
Light Load ◽  
Zero Current Switching ◽  
Active Clamp ◽  
Secondary Side

A novel Pulse-Width-Modulation (PWM) quasi-resonant active-clamp phase-shifted full-bridge converter is presented and analyzed in this paper. In the proposed topology, an active-clamp switch and a clamp capacitor that resonates with the leakage inductance of transformer are employed at the secondary side. The active-clamp circuit helps all of the primary switches in achieving both zero-voltage switching (ZVS) turn-on and nearly zero-current switching (ZCS) turn-off over the entire load range, and resets the primary current during the freewheeling interval. The operation of the active-clamp circuit eliminates voltage ringing across the rectifier. In addition, the secondary diodes can achieve ZCS turn-off, which removes the reverse recovery problem of diodes, and the active-clamp switch can achieve ZCS turn-on. A 3.5-kW prototype was built to verify the performance of the proposed converter. A maximum efficiency of 97.6% was achieved under a 2-kW load, and an efficiency of more than 96% was achieved even under a light load.

scholarly journals A PWM/PFM Dual-Mode DC-DC Buck Converter with Load-Dependent Efficiency-Controllable Scheme for Multi-Purpose IoT Applications

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 960
Author(s):  
Myeong Woo Kim ◽  
Jae Joon Kim
Keyword(s):  
Power Efficiency ◽  
Buck Converter ◽  
Maximum Efficiency ◽  
Switching Frequency ◽  
Cmos Process ◽  
Dual Mode ◽  
Pulse Frequency Modulation ◽  
Heavy Load ◽  
Iot Applications ◽  
Light Load

This paper presents a dual-mode DC-DC buck converter including a load-dependent, efficiency-controllable scheme to support multi-purpose IoT applications. For light-load applications, a selectable adaptive on-time pulse frequency modulation (PFM) control is proposed to achieve optimum power efficiency by selecting the optimum switching frequency according to the load current, thereby reducing unnecessary switching losses. When the inductor peak current value or converter output voltage ripple are considered in some applications, its on-time can be adjusted further. In heavy-load applications, a conventional pulse width modulation (PWM) control scheme is adopted, and its gate driver is structured to reduce dynamic current, preventing the current from shooting through the power switch. A proposed dual-mode buck converter prototype is fabricated in a 180 nm CMOS process, achieving its measured maximum efficiency of 95.7% and power density of 0.83 W/mm2.

scholarly journals Association Control Based  Load Balancing in Wireless  Cellular Networks Using  Preamble Sequences

2021 ◽  
Author(s):  
◽  
Ankit Chopra
Keyword(s):  
Load Balancing ◽  
Cellular Networks ◽  
Network Capacity ◽  
Correlation Property ◽  
User Association ◽  
Heavy Load ◽  
Implicit Information ◽  
Light Load ◽  
Load Imbalance ◽  
Radio Resources

<p>The efficient allocation and use of radio resources is crucial for achieving the maximum possible throughput and capacity in wireless networks. The conventional strongest signal-based user association in cellular networks generally considers only the strength of the signal while selecting a BS, and ignores the level of congestion or load at it. As a consequence, some BSs tend to suffer from heavy load, while their adjacent BSs may carry only light load. This load imbalance severely hampers the network from fully utilizing the network capacity and providing fair services to users. In this thesis, we investigate the applicability of the preamble code sequence, which is mainly used for cell identification, as an implicit information indicator for load balancing in cellular networks. By exploiting the high auto-correlation and low cross-correlation property among preamble sequences, we propose distributed load balancing schemes that implicitly obtain information about the load status of BSs, for intelligent association control. This enables the new users to be attached to BSs with relatively low load in the long term, alleviating the problem of non-uniform user distribution and load imbalance across the network. Extensive simulations are performed with various user densities considering throughput fair and resource fair, as the resource allocation policies in each cell. It is observed that significant improvement in minimum throughput and fair user distribution is achieved by employing our proposed schemes, and preamble sequences can be effectively used as a leverage for better cell-site selection from the viewpoint of fairness provisioning. The load of the entire system is also observed to be balanced, which consequently enhances the capacity of the network, as evidenced by the simulation results.</p>

Analysis of nonlinear dynamic characteristic of a planetary gear system considering tooth surface friction

2021 ◽  
pp. 135065012199174
Author(s):  
Jingyue Wang ◽  
Ning Liu ◽  
Haotian Wang ◽  
Jiaqiang E
Keyword(s):  
Damping Ratio ◽  
Excitation Frequency ◽  
Planetary Gear ◽  
Gear System ◽  
Tooth Surface ◽  
Lumped Mass ◽  
Heavy Load ◽  
Light Load ◽  
Planetary Gear System ◽  
Bifurcation Behavior

Based on the lumped mass method, a torsional vibration model of the planetary gear system is established considering the nonlinear factors such as friction, time-varying meshing stiffness, backlash, and comprehensive error. The Runge–Kutta numerical method is used to analyze the motion characteristics of the system with various parameters and the influence of tooth friction on the bifurcation and chaos characteristics of the system. The numerical simulation results show that the system has rich bifurcation behavior with the excitation frequency, damping ratio, comprehensive error amplitude, load and backlash, and experiences multiple periodic motion and chaotic motion. Tooth friction makes the bifurcation behavior of the system fuzzy in the high frequency and heavy load areas, makes the chaos of the system restrained in the low-damping ratio and light load areas, advances the bifurcation point of the system in the small comprehensive error amplitude area, and makes the period window of the chaos area larger in the large-backlash area, which makes the bifurcation behavior of the system more complex.

Acute Physiological Response to Light- and Heavy-load Power-oriented Exercise in Older Adults

2021 ◽  
Author(s):  
Carlos Rodriguez-Lopez ◽  
Julian Alcazar ◽  
Jose Losa-Reyna ◽  
JuanManuel Carmona-Torres ◽  
Aurora Maria Cruz-Santaella ◽  
...  
Keyword(s):  
Older Adults ◽  
Creatine Kinase ◽  
Resistance Training ◽  
Isometric Force ◽  
Rate Of Force Development ◽  
Heavy Load ◽  
Force Development ◽  
Sit To Stand ◽  
Light Load ◽  
Maximal Isometric Force

AbstractThis study investigated the acute responses to volume-load-matched heavy-load (80% 1RM) versus light-load (40% 1RM) power-oriented resistance training sessions in well-functioning older adults. Using a randomized cross-over design, 15 volunteers completed each condition on a leg press. Neuromuscular (maximal isometric force and rate of force development) and functional performance (power during sit-to-stand test), lactate, and muscle damage biochemistry (creatine kinase, lactate dehydrogenase and C-reactive protein serum concentration) were assessed pre- and post-exercise. Performance declines were found after heavy-load (Cohen’s d effect size (d); maximal isometric force=0.95 d; rate of force development=1.17 d; sit-to-stand power =0.38 d, all p<0.05) and light-load (maximal isometric force=0.45 d; rate of force development=0.9 d; sit-to-stand power=1.17 d, all p<0.05), while lactate concentration increased only after light-load (1.7 d, p=0.001). However, no differences were found between conditions (all p>0.05). Both conditions increased creatine kinase the day after exercise (marginal effect=0.75 d, p<0.001), but no other blood markers increased (all, p>0.05). Irrespective of the load used, power training induced non-clinically significant decreases in sit-to-stand performance, moderate declines in maximal isometric force, but pronounced decreases in the rate of force development. Furthermore, the metabolic stress and muscle damage were minor; both sessions were generally well tolerated by well-functioning older adults without previous experience in resistance training.

Research on Multi-Mode Controller of Switching Power Supply

2014 ◽  
Vol 568-570 ◽  
pp. 1217-1220
Author(s):  
Shu Lin Liu ◽  
Li Li Qi
Keyword(s):  
Power Supply ◽  
Switching Frequency ◽  
Switching Power Supply ◽  
Load Range ◽  
Heavy Load ◽  
Operating Modes ◽  
Switching Power ◽  
Advantages And Disadvantages ◽  
Switching Losses ◽  
Light Load

In order to improve the efficiency of the switching power supply in whole load range, the controller with PWM, PFM and BURST operating modes is designed in this paper, which changes the operation mode automatically according to the load. The operating principle and the advantages and disadvantages of the three operating modes are analyzed and compared. PWM mode is used in heavy load; PFM mode is used in light load to reduce switching losses by reducing the switching frequency and BURST mode is used at the standby time to further reduce switching losses. The main control module is designed and simulation results verify the feasibility of the designed circuit.

scholarly journals Optimized hip-knee-ankle exoskeleton assistance reduces the metabolic cost of walking with worn loads

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Gwendolyn M. Bryan ◽  
Patrick W. Franks ◽  
Seungmoon Song ◽  
Ricardo Reyes ◽  
Meghan P. O’Donovan ◽  
...  
Keyword(s):  
Body Weight ◽  
Muscle Activity ◽  
Metabolic Cost ◽  
Load Carriage ◽  
Heavy Load ◽  
Human In The Loop ◽  
Light Load ◽  
Wide Range ◽  
Ankle Exoskeleton ◽  
The Individual

Abstract Background Load carriage is common in a wide range of professions, but prolonged load carriage is associated with increased fatigue and overuse injuries. Exoskeletons could improve the quality of life of these professionals by reducing metabolic cost to combat fatigue and reducing muscle activity to prevent injuries. Current exoskeletons have reduced the metabolic cost of loaded walking by up to 22% relative to walking in the device with no assistance when assisting one or two joints. Greater metabolic reductions may be possible with optimized assistance of the entire leg. Methods We used human-in the-loop optimization to optimize hip-knee-ankle exoskeleton assistance with no additional load, a light load (15% of body weight), and a heavy load (30% of body weight) for three participants. All loads were applied through a weight vest with an attached waist belt. We measured metabolic cost, exoskeleton assistance, kinematics, and muscle activity. We performed Friedman’s tests to analyze trends across worn loads and paired t-tests to determine whether changes from the unassisted conditions to the assisted conditions were significant. Results Exoskeleton assistance reduced the metabolic cost of walking relative to walking in the device without assistance for all tested conditions. Exoskeleton assistance reduced the metabolic cost of walking by 48% with no load (p = 0.05), 41% with the light load (p = 0.01), and 43% with the heavy load (p = 0.04). The smaller metabolic reduction with the light load may be due to insufficient participant training or lack of optimizer convergence. The total applied positive power was similar for all tested conditions, and the positive knee power decreased slightly as load increased. Optimized torque timing parameters were consistent across participants and load conditions while optimized magnitude parameters varied. Conclusions Whole-leg exoskeleton assistance can reduce the metabolic cost of walking while carrying a range of loads. The consistent optimized timing parameters across participants and conditions suggest that metabolic cost reductions are sensitive to torque timing. The variable torque magnitude parameters could imply that torque magnitude should be customized to the individual, or that there is a range of useful torque magnitudes. Future work should test whether applying the load to the exoskeleton rather than the person’s torso results in larger benefits.

scholarly journals High-Volume Light-Load Strength Training, but Not Low-Volume Heavy-Load Strength Training Increases Corticospinal Excitability

2020 ◽  
Vol 2 (3) ◽  
pp. 1-12
Author(s):  
Rhys Painter ◽  
Simin Rahman ◽  
Woo Kim ◽  
Ummatul Siddique ◽  
Ashlyn Frazer ◽  
...  
Keyword(s):  
Strength Training ◽  
Short Interval ◽  
High Volume ◽  
Intracortical Inhibition ◽  
Corticospinal Excitability ◽  
Control Group ◽  
Heavy Load ◽  
Post Exercise ◽  
Light Load ◽  
Low Volume

Purpose: To determine whether corticospinal excitability (CSE) and inhibition are differentially modulated following high-volume light-load strength training compared to low-volume heavy-load strength training. We hypothesised high-volume light-load strength training would increase CSE and low-volume heavy-load strength training would reduce intracortical inhibition. Methods: Transcranial magnetic stimulation (TMS) was used to assess CSE, short-interval intracortical inhibition (SICI), and silent period duration (SP) following high-volume light-load strength training (n = 9), low-volume heavy-load strength training (n = 8) compared to a control group (n = 10). Twenty-seven participants completed either (1) low-volume heavy-load strength training (80% one-repetition maximum [1RM]); (2) high-volume light-load strength training (20% 1-RM) or (3) a control condition. CSE, SICI and SP were measured using TMS at baseline and four time-points over a 60 min post-exercise period. Results: CSE increased rapidly (within 5 min post-exercise) for high-volume light-load strength training and remained elevated for 60 min compared to low-volume heavy-load strength training and control groups. There were no differences following any training for reduced SICI or SP. Conclusion: These results suggest that high-volume light-load strength training increases the excitability of corticospinal neurons and this increase is likely to be the predominant mechanism for increasing CSE for up to 60 min post training. It may be possible that a greater number of ST sessions are required to observe any differences in the excitability of the intrinsic inhibitory motor-network following high-volume light-load strength training and low-volume heavy-load strength training.

scholarly journals Article Retracted 22/07/2011 - GuST: Guaranteed Services Token Protocol for Real-Time Communications

1970 ◽  
Vol 8 (1-2) ◽  
pp. 197-210
Author(s):  
Simeon Ozuomba ◽  
Gloria A. Chukwudebe
Keyword(s):  
Access Control ◽  
Real Time ◽  
Integrated Services ◽  
Multimedia Applications ◽  
Media Access Control ◽  
Heavy Load ◽  
Integrated Services Networks ◽  
Real Time Traffic ◽  
Light Load ◽  
Guaranteed Services

This Article was RETRACTED on 22/07/2011 at the request of the authors because the paper has already been published in another journal in Nigeria. - Editor, JIEIn this paper, Guaranteed Services Token (GuST) protocol for integrated services networks which can efficiently support diverse traffic consisting of hard and soft real-time traffic along with non-real-time traffic is proposed. This is to meet the increasing demand for better performance of real time communications required by distributed multimedia applications, process control, factory automation, etc.For some time now, timed-token protocols have become the preferred Medium Access Control (MAC) protocol for supporting modern real-time systems. However, the existing timed-token protocols have been studied, and inefficiencies discovered with the way asynchronous traffic is handled. GuST employs the timed-token mechanisms in the Timely-Token protocol along with that of Budget Sharing Token (BuST) protocol. We discussed some bounds on the behavior of GuST protocol. In particular, we show that the token is never late, and the transmission of asynchronous traffic is guaranteed. We also compared GuST protocol against the Timely-Token protocol and the BuST protocol. Our comparison focuses on the ability of those protocols to support synchronous and asynchronous traffic. We demonstrated that the performance achieved by GuST is better than Timely-Toke n and BuST protocols especially for a system with light load of real-time traffic but with heavy load of non-real-time traffic. GuST protocol can be incorporated into the Ethernet network to provide real-time performance guarantees to multimedia applications. It can also be used to improve on the throughput of the Profibus which is a Fieldbus network standard.Keywords: Timed-Token Protocol; Ethernet; Timely-Token Protocol; Budget Sharing Token Protocol; Integrated Services Networks; Real-Time Traffic; Non-Real-Time Traffic; Media Access Control (MAC); GuST: Guaranteed; Services Token protocolDOI: http://dx.doi.org/10.3126/jie.v8i1-2.5112Journal of the Institute of Engineering Vol. 8, No. 1&2, 2010/2011Page: 197-210Uploaded Date: 20 July, 2011

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