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Armin Jafari

Cette personne a quitté l’EPFL

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Publications associées (31)

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Nanoplasma-enabled picosecond switches for ultrafast electronics

Elison de Nazareth Matioli, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani, Palliyage Srilak Nirmana Perera, Minghua Zhu, Giovanni Santoruvo

The broad applications of ultrawide-band signals and terahertz waves in quantum measurements, imaging and sensing techniques, advanced biological treatments, and very-high-data-rate communications have drawn extensive attention to ultrafast electronics. In ...

2020

Pushing the Limits of Efficiency and Power Density in High-Frequency Power Conversion Based on Wide-Band-Gap Technologies

Armin Jafari

The emergence of wide-band-gap (WBG) power transistors with low conduction losses and high-speed switching speeds has paved the way for more-than-ever efficient power electronics systems and huge energy saving potentials. Likewise, power density- the ratio ...

EPFL2021

Small-Signal Approach for Precise Evaluation of Gate Losses in Soft-Switched Wide-Band-Gap Transistors

Elison de Nazareth Matioli, Armin Jafari, Palliyage Srilak Nirmana Perera

High-frequency switching is favorable for fast transient response, small size of passive components and superior power density, especially in soft-switching topologies. At high frequencies, power dissipation due to consecutive charging/discharging of gate ...

IEEE2020

Switching losses in power devices: From dynamic on resistance to output capacitance hysteresis

Elison de Nazareth Matioli, Remco Franciscus Peter van Erp, Armin Jafari, Palliyage Srilak Nirmana Perera, Hongkeng Zhu

In this paper, we review some of the main methods to characterize on-state and off-state losses in wide-band-gap devices under switching conditions. In the off-state, we will discuss about losses related to charging and discharging the output capacitance i ...

IEEE2023

97.4%-Efficient All-GaN Dual-Active-Bridge Converter with High Step-up High-Frequency Matrix Transformer

Elison de Nazareth Matioli, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani, Palliyage Srilak Nirmana Perera

In this work, we demonstrate a state-of-the-art high step-up/down dual-active-bridge (DAB) converter designed with GaN transistors, to achieve a high efficiency and large power-density. A quasi-planar matrix transformer with high step-up/down ratio is demo ...

2020

Measurement of Large-Signal Coss and Coss Losses of Transistors Based on Nonlinear Resonance

Elison de Nazareth Matioli, Armin Jafari, Palliyage Srilak Nirmana Perera

In this letter, we present a new measurement technique to evaluate the large-signal output capacitance ( COSS ) of transistors as well as the COSS energy dissipation ( EDISS ), based on the nonlinear resonance between a known inductor and the output capaci ...

2019

On-Chip High-Voltage Sensors Based on Trap-Assisted 2DEG Channel Control

Elison de Nazareth Matioli, Armin Jafari

In this work, we present a new device concept for compact high-voltage sensing with high-impedance input port, consisting of an AlGaN/GaN high-electron-mobility channel controlled by trapped carriers generated by a metallic electrode. The high-voltage appl ...

Institute of Electrical and Electronics Engineers2019

Investigation on Output Capacitance Losses in Superjunction and GaN-on-Si Power Transistors

Elison de Nazareth Matioli, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani, Palliyage Srilak Nirmana Perera, Halil Kerim Yildirim

Low ON-resistance of advanced superjunction (SJ) and GaN-on-Si transistors is of great importance in power converters, however, the anomalous loss in their output capacitance (C OSS ) severely limits their performance. In this work, we use an energy-orient ...

IEEE2021

Output-Capacitance Hysteresis Losses of Field-Effect Transistors

Elison de Nazareth Matioli, Armin Jafari, Luca Nela, Palliyage Srilak Nirmana Perera, Georgios Kampitsis

Resonant-type power converters are supposed to generate zero switching losses during soft-switching operation. In recent research, unexpected switching losses were reported in these converters, which were attributed to a large-signal hysteresis observed in ...

IEEE2020

Optimized kW-Range Boost Converter Based on Impulse Rectification with 52 kW/l and 98.6% Efficiency

Elison de Nazareth Matioli, Armin Jafari, Remco Franciscus Peter van Erp

Maximizing the efficiency and power density of dc-dc converters demands parallel optimizations in design and control, especially for variable-frequency converters operating over wide frequency ranges. This work presents the full-scale optimization of a kil ...

2021

Resonances on GaN-on-Si Epitaxies: A Source of Output Capacitance Losses in Power HEMTs

Elison de Nazareth Matioli, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani, Riyaz Mohammed Abdul Khadar, Minghua Zhu

GaN-on-Si high-electron-mobility transistors (HEMTs) exhibit excellent properties for efficient power conversion. Nevertheless, a considerable energy loss associated with the charging and discharging of the output capacitance (COSS) in these transistors se ...

Institute of Electrical and Electronics Engineers2021

Output Capacitance Losses in Wide-Band-Gap Transistors: A Small-Signal Modeling Approach

Elison de Nazareth Matioli, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani, Palliyage Srilak Nirmana Perera

Wide-band-gap (WBG) power semiconductor devices are gaining an increasing interest in power circuits, as they exhibit a low specific ON-resistance (RON) while providing a high blocking voltage. The energy dissipation corresponding to resonantly charging an ...

IEEE2020

Analysis of Large-Signal Output Capacitance of Transistors using Sawyer–Tower Circuit

Elison de Nazareth Matioli, Remco Franciscus Peter van Erp, Armin Jafari, Palliyage Srilak Nirmana Perera, Georgios Kampitsis

A detailed analysis on the Sawyer–Tower method used in the measurement of large-signal output capacitance (Co) of power transistors is presented, followed by important design recommendations to obtain accurate results. Key factors affecting the proper impl ...

2020

Hard-Switching Losses in Power FETs: The Role of Output Capacitance

Elison de Nazareth Matioli, Armin Jafari, Palliyage Srilak Nirmana Perera, Reza Soleiman Zadeh Ardebili

For certain field-effect transistors (FETs) in soft-switching operation, the large-signal behavior of their output capacitance ( Co ) has shown to deviate considerably from the datasheet values. This can have a significant effect on hard-switching losses i ...

2021

High-Accuracy Calibration-Free Calorimeter for the Measurement of Low Power Losses

Elison de Nazareth Matioli, Remco Franciscus Peter van Erp, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani, Reza Soleiman Zadeh Ardebili, Enea Figini

Wide-band-gap technologies enable ultra-high efficiencies in high-frequency power conversion. However, inadequate accuracies in electrical measurements could lead to spurious efficiency measurements, even above 100%. Furthermore, bandwidth limitations, par ...

2020

Calibration-Free Calorimeter for Sensitive Loss Measurements: Case of High-Frequency Inductors

Elison de Nazareth Matioli, Remco Franciscus Peter van Erp, Armin Jafari, Palliyage Srilak Nirmana Perera, Enea Figini

IEEE2020

Kilowatt-range Picosecond Switching Based on Microplasma Devices

Elison de Nazareth Matioli, Remco Franciscus Peter van Erp, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani

Plasma formation in micro- and nano-scales enables an ultrahigh-dv/dt picosecond switching in an integrated circuit form factor. Such on-chip plasma devices could provide a transformative approach to achieving high-power levels at very high frequencies, fa ...

Institute of Electrical and Electronics Engineers2021

Comparison of Wide-Band-Gap Technologies for Soft-Switching Losses at High Frequencies (vol 35, pg 12595, 2020)

Elison de Nazareth Matioli, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani, Palliyage Srilak Nirmana Perera, Reza Soleiman Zadeh Ardebili, Halil Kerim Yildirim

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2021

On the Dynamic Performance of Laterally Gated Transistors

Elison de Nazareth Matioli, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani, Catherine Erine, Giovanni Santoruvo

Laterally gated transistors have been proposed as an innovative device architecture in which a semiconducting channel is controlled by side gates. In this sense, the gate can either be in contact with the sidewalls or be separated by a gap. In the latter c ...

Institute of Electrical and Electronics Engineers2019

Coss Loss Tangent of Field-Effect Transistors: Generalizing High-Frequency Soft-Switching Losses

Elison de Nazareth Matioli, Luca Nela, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani, Palliyage Srilak Nirmana Perera

The dissipated energy (Ediss) related to the resonant charging/discharging of a transistor output capacitance, becomes a dominant loss factor for power converters operating in the MHz range. A recent work has introduced a small-signal measurement method to ...

2020