Denis Labrousse

Common-Mode Modeling of the Association of

The reliability of electronic systems is a major constraint depending on electromagnetic interference levels. Vehicle manufacturers are clearly concerned by electromagnetic compatibility studies and, especially, for electrical drive systems in which embedded power electronics is used and must, thus, be correctly designed. A global synthesis of common-mode disturbances of such equipment is pointed out in this paper and a generic model of a complex power-electronic device is presented and applied to a motor-drive system.

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This paper presents experimental robustness tests made on Silicon Carbide (SiC) MOSFETs and SiC Bipolar Junction Transistors (BJTs) submitted to short-circuit operations (SC) or current limitation modes. For SiC MOSFETs, a gate leakage current is detected before failure without being responsible for the immediate failure. Nevertheless this gate leakage current is not without effect on the integrity of the SiC MOSFETs. Based on several robustness tests performed on SiC MOSFETs and on the comparison with experimental results obtained with SiC BJTs, the paper points out two main failure modes for SiC MOSFETs. The first one results in a simultaneously short circuit between drain and gate and drain and source and the second one in a degradation of the insulation between gate and source leading to a short circuit between gate and source. For some tested devices, the failure appears in a very interesting open state mode between drain and source after physical short-circuit between gate and source with a mode of failure very similar to those observed for SiC BJT.

-Switching Cells: Application to an Electric-Vehicle-Drive System

This paper presents an original self-starting DC/DC converter for low-power and low-voltage applications such as energy harvesting from microbial fuel cells to supply low-power electronic devices. Design is performed according to specifications issued from the stringent characteristics of microbial fuel cells. The harvested power reaches 10 mW under 0.3 V input voltage for the ten 1.3-liter experimental microbial fuel cells connected in parallel. The converter is adapted from a boost topology. It includes a self-oscillating sub-circuit for autonomous operation and a simple analog input-voltage control to harvest maximum energy from the source. The paper presents experimental results from a discrete and low-cost prototype. A global efficiency of more than 73% is achieved for 0.3 V input-voltage and under realistic harvesting conditions for the MFCs and the converter prototype.

Study of short-circuit robustness of SiC MOSFETs, analysis of the failure modes and comparison with BJTs

This study aims to assess the reliability of smart converters for applications using 24 V batteries. It compares degradation effects and lifetime durations for similar dissipated energies when these smart power switches are subjected to normal and extreme protection test conditions. Three experimental ageing tests have been performed: (i) ageing tests under normal protection mode, (ii) ageing tests under repetitive inductive avalanche switching and (iii) ageing tests under repetitive short-circuit. Evolution of several electrical parameters such as on-state resistance; threshold voltage and saturation current have been monitored. Tested devices under normal condition and under repetitive inductive avalanche have failed after about the same number of cycles with the same dissipated energy. However, several results show a significant decrease of the lifetime under repetitive short-circuit tests for a similar dissipated energy.

A 140 mV Self-Starting 10 mW DC/DC Converter for Powering Low-Power Electronic Devices from Low-Voltage Microbial Fuel Cells

This article presents a resonant DC-DC converter suitable for ultra-low power and low voltage sources. This original topology allows a self-starting and a self-operation under harsh conditions of input voltage and power without any additional start-up assistance. A global theoretical modeling of the converter which includes start-up and steady-state phases is presented and a methodology for optimal design is detailed. It is based on the combination of both theoretical calculations and circuit simulations. Experimental tests based on discrete prototypes are carried out in order to demonstrate the good operation of the converter. Experimental tests have been achieved using an RF energy harvesting source. Ultra-low power and low voltage conditions as low as 3 μW and 100 mV respectively can be achieved as demonstrated by the experimental measurements. The input low voltage is stepped-up to a conventional level of some volts, what allows to power autonomously and solely low power circuits from energy harvesting sources.

Reliability of power MOSFET-based smart switches under normal and extreme conditions for 24 V battery system applications

Toward the aim of advanced integration in power electronic, the properties of Multicell interleaved converters are of prime interest. Among these properties, the EMC behavior is interesting and the dynamic performances are excellent. However their implementation requires the monitoring and balancing of intercell currents. On one hand, the converter control must ensure a satisfying balanced distribution of currents among switching cells outputs, so that magnetic components are used optimally. On the other hand, this control must also ensure the regulation loop of the output current. To achieve these goals, we decided to work on a direct matrix model, which allows to highlight the fast eigenmode related to the power (common mode) and the slow magnetizing eigenmodes (differential modes). The synthesis of the control and the calculus of corrector parameters are performed using inversion of this direct model. A digital control based on this method has been implemented, and the measurement results that we present confirm its efficiency on current balancing.

Ultra-Low Power, Low Voltage, Self-Powered Resonant DC-DC Converter for Energy Harvesting

Bond wire liftoff and metallization reconstruction are two of the most frequent failures observed during power semiconductor module operation. Aging of the top-level power dies, which occurs due to power cycling, results in the redistribution of the current in the metallization layer and the elementary cells of the power dies (MOSFET-Metal Oxide Semiconductor Field Effect Transistor, or IGBT-Insulated Gate Bipolar Transistor), leading to a risk of critical failure when either the local current density or the local temperature reaches a critical value. This paper reports on the experimental estimation of the distribution of dc flowing in the power dies and investigates the effect of the local degradation of aluminum sheet resistance and bond wire liftoff on the current distribution. The local distribution of the current flowing in the metallization layer and in the power dies was estimated by mapping the electric potential of the source metallization. The obtained results facilitate the identification of failure risks that result from the aging process (which occurs due to current redistribution) of top-level power dies and provide an understanding of the physical origins of failures.

Control for the currents balancing of a multicell interleaved converter with ICT

This paper proposes a method to synthesize a full wave control applied to a multilevel modular converter (MMC). This method guarantees the output waveform and the balancing of the capacitors. Numerical simulations and experiments are used to check the validity of the approach.

Estimating Current Distributions in Power Semiconductor Dies Under Aging Conditions: Bond Wire Liftoff and Aluminum Reconstruction

This paper explores the application of the Variable Delay Frequency Modulation (VDFM) to an Interleaved Multicellular Parallel converter. VDFM is a modulation technique specially intended to reduce conducted EMI generated by parallel converters. This technique combines interleaving and frequency modulation in such a way that provides the best attenuation. On the other hand, Coupled Interleaved Multicelular Parallel Converters (CIMPC) needs a perfect current sharing among phases. In this paper we consider the effect of VDFM nonidealities on the EMI attenuation in order to consider the application of this technique to CIMPC.

Use of a full wave correct-by-design command to control a multilevel modular converter

This paper deals with time domain simulation of common mode (CM) conducted disturbances in power electronics. This study proposes a proof of concept of a fast reconstruction method (FRM), which allows to compute the spectrum of a current based on the knowledge of a single pulse of current (i.e., the knowledge of the disturbances on a small fraction of time) and of the switching instants (i.e., the control strategy of the structure). The first parts of the paper demonstrate the reliability of the method using data measurements of a CM current generated by a PWM half-bridge converter and then by a three phase inverter. The simulation time saved thanks to the FRM is then quantified by comparing the simulation durations with or without using the FRM. In our example, the FRM allows to divide the simulation time by about 10. This analysis points out that the complex information of a CM current is contained in a small time interval. As a consequence the complete spectrum can be predicted with only a very fast simulation. The mathematical techniques developed here forecast promising reduction of simulation durations.