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Bharat Agrawal

Bio: Bharat Agrawal is an academic researcher from McMaster University. The author has contributed to research in topics: Inductor & Capacitor. The author has an hindex of 4, co-authored 5 publications receiving 71 citations.
Topics: Inductor, Capacitor, Power (physics), Voltage, MOSFET

Papers
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Journal ArticleDOI
Niloufar Keshmiri1, Deqiang Wang1, Bharat Agrawal1, Ruoyu Hou1, Ali Emadi1 
TL;DR: The detailed benefits of using GaN devices in transportation electrification applications are investigated, the material properties of GaN including the applications ofGaN HEMTs at different switch ratings are presented, and the challenges currently facing the transportation industry are introduced.
Abstract: Gallium Nitride High Electron Mobility Transistors (GaN HEMTs) enable higher efficiency, higher power density, and smaller passive components resulting in lighter, smaller and more efficient electrical systems as opposed to conventional Silicon (Si) based devices. This paper investigates the detailed benefits of using GaN devices in transportation electrification applications. The material properties of GaN including the applications of GaN HEMTs at different switch ratings are presented. The challenges currently facing the transportation industry are introduced and possible solutions are presented. A detailed review of the use of GaN in the Electric Vehicle (EV) powertrain is discussed. The implementation of GaN devices in aircraft, ships, rail vehicles and heavy-duty vehicles is briefly covered. Future trends of GaN devices in terms of cost, voltage level, gate driver design, thermal management and packaging are investigated.

82 citations

Proceedings ArticleDOI
26 Mar 2017
TL;DR: In this paper, the authors present a method to obtain an estimate of switching transition times and power losses, using datasheet parameters, for SiC MOSFETs with non-flat gate-plateau region.
Abstract: Power loss calculations are critical to a power converter design, helping with estimation of efficiency, switch selection and cooling system design. Moreover, power losses in a MOSFET may limit the maximum switching frequency in a power converter. Switching energy values aren't always available in MOSFET datasheets at all operating points, and calculation of voltage and current rise-time and fall-time is needed. This paper introduces a method to obtain an estimate of switching transition times and power losses, using datasheet parameters, for SiC MOSFETs with non-flat gate-plateau region. Three methods are discussed here, two existing and a proposed method. These methods are used to evaluate a certain MOSFET product, and calculated values are compared with results from PLECS simulation and double pulse test experiment. The proposed method is shown to yield improved accuracy.

34 citations

Journal ArticleDOI
TL;DR: Variable frequency critical soft switching control method is proposed with the constraints to maintain the maximum frequency within soft switching operation to prevent turn-on losses that are typically much larger than the turn-off losses in SiC and GaN FETs.
Abstract: This paper derives a variable-frequency critical soft-switching control method for nonisolated DC/DC converters using wide-bandgap devices. The critical soft switching control technique under maximum frequency trajectory is introduced to maintain zero voltage switching over a wide range of modulation ratios according to the load variation. The concept prevents turn-on losses that are typically much larger than the turn-off losses in SiC and GaN FETs and the latter can be further reduced by adding external drain-source capacitors. We have derived the boundary conditions for critical soft switching operation. For the reduction of inductor value and volume, a maximum available switching frequency is applied to the converter within the constraints of device requirement and soft switching boundary conditions. We demonstrate experimentally that the proposed concept reduces the power losses in the wide-bandgap devices by a factor of approximately 3, enables an increase of the switching frequency by a factor of about 5, and a decrease of the main inductance by a factor of about 10. Then variable frequency critical soft switching control method is proposed with the constraints to maintain the maximum frequency within soft switching operation. Since our test bench uses off-the-shelf inductors, the inductors are subject to significant high frequency losses. Despite this, the converter efficiency increases by 1%.

13 citations

Proceedings ArticleDOI
27 Jun 2016
TL;DR: In this article, a half-bridge DC/DC switching circuit is proposed for the balancing of lithium-ion cells, and highlights its advantages over existing cell balancing techniques, showing greater controllability and improvement in efficiency in comparison with existing systems.
Abstract: Cells in an electric vehicle battery pack tend to become out of balance after several charging and discharging cycles, resulting in capacity under-utilization and over-sizing of battery packs to achieve extended driving range. This makes it necessary to have a cell balancing mechanism onboard of the battery management system. This paper introduces a half-bridge DC/DC switching circuit for the balancing of lithium-ion cells, and highlights its advantages over existing cell balancing techniques. Furthermore, details on planar transformer design, control feedback, simulation results in MATLAB/Simulink, and experimental observations are included, showing greater controllability and improvement in efficiency in comparison with existing systems.

11 citations

Proceedings ArticleDOI
01 Mar 2017
TL;DR: This paper introduces a soft-switching technique for power converters using wide bandgap devices to replace the larger turn-on losses with smaller turn-off losses and thus reduce the power dissipation of the overall system.
Abstract: The advent of Silicon-Carbide and Gallium-Nitride MOSFETs offers potential to realize higher energy density power converters operating at increased switching frequencies. The maximum switching frequency in a power converter is limited by the ability of the switching device package to dissipate its switching and conduction losses. At a given value of drain-source voltage and current, the turn-on losses in a MOSFET are usually greater than the turn-off losses. This paper introduces a soft-switching technique for power converters using wide bandgap devices to replace the larger turn-on losses with smaller turn-off losses and thus reduce the power dissipation of the overall system. The turn-off losses are further reduced with use of additional capacitance across the MOSFET drain-source terminals. Results from an analytical model, LTSpice simulation and experimentation are shown to match closely, with a significant reduction in overall system losses.

7 citations


Cited by
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01 Jan 2016
TL;DR: This power electronics converters applications and design helps people to enjoy a good book with a cup of tea in the afternoon, instead they cope with some malicious virus inside their desktop computer.
Abstract: Thank you for downloading power electronics converters applications and design. Maybe you have knowledge that, people have look numerous times for their favorite readings like this power electronics converters applications and design, but end up in harmful downloads. Rather than enjoying a good book with a cup of tea in the afternoon, instead they cope with some malicious virus inside their desktop computer.

754 citations

Journal ArticleDOI
TL;DR: The effects correlations and possible solutions are explained to provide a detailed, yet broader understanding of the Li-ion batteries low-temperature operating scenarios.
Abstract: The purpose of this paper is to review the recent literature regarding the effects of low temperatures on Lithium ion (Li-ion) batteries for electric vehicle, plug-in hybrid electric vehicle, and hybrid electric vehicle applications. Special consideration is given to nine major effects that directly or indirectly impact the battery use at low temperatures and it is presented that they are correlated to each other. The main discussions in this paper are capacity loss, power loss, life degradation, safety hazard, unbalanced capacity, charging difficulty, thermal management system complexity, battery model and state estimation method complexity, and incremental cost. The effects correlations and possible solutions are explained to provide a detailed, yet broader understanding of the Li-ion batteries low-temperature operating scenarios.

90 citations

Journal ArticleDOI
TL;DR: In this article, the authors provide a glimpse of future GaN device technologies and advanced modeling approaches that can push the boundaries of these applications in terms of performance and reliability, which is a key missing piece to realize the full GaN platform with integrated digital, power, and RF electronics technologies.
Abstract: GaN technology is not only gaining traction in power and RF electronics but is also rapidly expanding into other application areas including digital and quantum computing electronics. This paper provides a glimpse of future GaN device technologies and advanced modeling approaches that can push the boundaries of these applications in terms of performance and reliability. While GaN power devices have recently been commercialized in the 15–900 V classes, new GaN devices are greatly desirable to explore both higher-voltage and ultra-low-voltage power applications. Moving into the RF domain, ultra-high frequency GaN devices are being used to implement digitized power amplifier circuits, and further advances using the hardware–software co-design approach can be expected. On the horizon is the GaN CMOS technology, a key missing piece to realize the full-GaN platform with integrated digital, power, and RF electronics technologies. Although currently a challenge, high-performance p-type GaN technology will be crucial to realize high-performance GaN CMOS circuits. Due to its excellent transport characteristics and ability to generate free carriers via polarization doping, GaN is expected to be an important technology for ultra-low temperature and quantum computing electronics. Finally, given the increasing cost of hardware prototyping of new devices and circuits, the use of high-fidelity device models and data-driven modeling approaches for technology-circuit co-design are projected to be the trends of the future. In this regard, physically inspired, mathematically robust, less computationally taxing, and predictive modeling approaches are indispensable. With all these and future efforts, we envision GaN to become the next Si for electronics.

83 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the present-day traction drive systems in the industry, control and modulation techniques for multilevel structures in the inverters, as well as the principal challenges that need to be addressed in the control stage of the multi-level traction inverter.
Abstract: Traction inverter has been the subject of many studies due to its essential role in the proper performance of the drive system. With the recent trend in increasing the input voltage in battery-powered electric vehicles, multilevel inverters have been proposed in the literature as a promising substitute for conventional two-level traction inverters. A critical aspect of utilizing multilevel structures is employing proper control and modulation techniques. The control system structure must be capable of handling a number of key issues, like capacitor voltage balancing and equal power loss sharing, which arise in multilevel topologies. This paper presents a review of the present-day traction drive systems in the industry, control and modulation techniques for multilevel structures in the inverters, as well as the principal challenges that need to be addressed in the control stage of the multilevel traction inverter. A comparison has been made between different methods based on the most important criteria and requirements of the traction drive system. Finally, future trends in this application are presented and some suggestions have been made for the next generation of traction drives.

67 citations