Publications by Armin Jafari | EPFL Graph Search

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

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

Measurement of WBG-based power supplies

Elison de Nazareth Matioli, Armin Jafari, Hongkeng Zhu

This paper discusses different measurement methods to evaluate the efficiency of WBG-based power supply solutions, including electrical measurement methods and their verification with calorimetric methods, and compares the performance of Si-based and GaN-b ...

IEEE2023

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

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

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

Enhanced-DAB Converter: Comprehensive Design Evaluation

Elison de Nazareth Matioli, Armin Jafari, Mohammad Samizadeh Nikooytabalvandani, Furkan Karakaya

Soft switching in dual-active-bridge (DAB) converters enables their efficient operation at high frequencies, where the reduction in the size of magnetic components could result in ultra-high power densities. Nonetheless, losing soft-switching at high frequ ...

IEEE2021

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

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

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

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

Kilowatt-range Picosecond Switching Based on Microplasma Devices

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

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

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2021

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

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

Active-Device Losses in Resonant Power Converters: A Case Study with Class-E Inverters

Elison de Nazareth Matioli, Jessy Anthony Ançay, Armin Jafari, Palliyage Srilak Nirmana Perera, Remco Franciscus Peter van Erp

Recent research has reported an undesirable OFF-state loss in high-frequency soft-switching power converters, such as resonant converters. This loss is attributed to a hysteresis loss related to the charging-discharging process of the output capacitance of ...

IEEE2021

Impact of Embedded Liquid Cooling on the Electrical Characteristics of GaN-on-Si Power Transistors

Elison de Nazareth Matioli, Armin Jafari, Palliyage Srilak Nirmana Perera, Catherine Erine, Remco Franciscus Peter van Erp, Luca Nela

Wide-Band-Gap semiconductors have enabled considerable miniaturization of power devices, which requires, however, new thermal management solutions to handle the resulting high heat fluxes. Recently, embedded liquid cooling in GaN-on-Si devices was demonstr ...

Institute of Electrical and Electronics Engineers2021

Output-Capacitance Hysteresis Losses of Field-Effect Transistors

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

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

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

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

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

Efficient High Step-up Operation in Boost Converters Based on Impulse Rectification

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

Conventional boost converters, while having a high level of simplicity and robustness, are known to have poor efficiency at high step-up regime. More complicated topologies have been extensively explored to increase the step-up ratio while keeping a high-e ...

2020

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, Furkan Karakaya

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

Negative Resistance in Cascode Transistors

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

Cascode topology which includes a high-voltage GaN and a low-voltage Si transistor is an attractive device concept, which uses the low ON-resistance of GaN while still being compatible with Si gate drivers. It demonstrates the highest threshold voltage amo ...

2020

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

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

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, Enea Figini, Armin Jafari, Palliyage Srilak Nirmana Perera, Remco Franciscus Peter van Erp, Michaël Heijnemans, Furkan Karakaya

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 ...

IEEE2020

Nanoplasma-enabled picosecond switches for ultrafast electronics

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

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