B. Boudart

Supercapacitor ageing at constant temperature and constant voltage and thermal shock

This paper presents supercapacitor ageing according to the voltage, the temperature and thermal shock tests. To investigate this effect, a test bench of accelerated supercapacitor calendar ageing was carried out. Experimental tests are realized at constant temperature when the supercapacitors are polarized at the maximum voltage. To quantify the supercapacitor ageing, the equivalent series resistance (ESR) and the equivalent capacitance (C) are measured using the DC and AC characterization. To lead to the determination of the supercapacitor lifetime, Arrhenius law, that describes the effect of temperature on the velocity of a chemical reaction, is considered. Finally, experimental results of supercapacitor thermal shock are presented.

Calendar and cycling ageing of activated carbon supercapacitor for automotive application

Abstract This paper presents supercapacitor ageing as a function of voltage, temperature and charge/discharge cycling solicitations. To investigate their effects, a test bench of accelerated supercapacitor calendar and cycling ageing was carried out. Experimental tests are performed at constant temperature when the supercapacitors are polarized at the maximum voltage in the case of calendar ageing. In the case of cycling test, supercapacitors are charged and discharged at constant current. It can be noted that when the supercapacitors are charged and discharged at constant current the temperature of the supercapacitor increases and that the average voltage is not zero. To quantify the supercapacitor ageing, the equivalent series resistance (ESR) and the equivalent capacitance (C) are measured.

Characterization of high-voltage IGBT module degradations under PWM power cycling test at high ambient temperature

The success of the high temperature power electronic applications depends on the power device reliability. The increasing thermal demands, like in hybrid electric cars, require power devices operating at junction temperatures above their common level of 125 °C. The thermal cycles generated in standard modules in such conditions induce several failure mechanisms in their package and chips. This article presents ageing tests of an EconoPIM IGBT module submitted to PWM power cycling at high ambient temperature. Several electrical and thermal parameters are monitored to detect failure onsets in the module components. Static and dynamic measurements are periodically made to reveal possible module characteristic drifts, and to better understand the effects of this kind of cycling test on the module static and switching behaviors. The follow-up of the dynamic parameter evolution represents the originality of this study.

Supercapacitors aging diagnosis using least square algorithm

Supercapacitor aging is mainly related to thermal and voltage constraints. This aging causes degradation in the supercapacitor performances which can lead to the failure of this component. To avoid this failure, it is necessary to determine the supercapacitor state of health. The aim of this study is the supercapacitor diagnosis. In this paper, aging tests of supercapacitor subjected to calendar aging constraints are presented. The supercapacitor is aged at constant temperature and constant bias voltage. During the aging process, the variations of the supercapacitor equivalent series resistance (ESR) and equivalent capacitance (C) are measured and analyzed. For diagnosis, a least square algorithm is used. This algorithm is used for ESR and C identification during the supercapacitor operation. For vehicle applications, the supercapacitor is considered as aged when the capacitance loss is in order of 20% of its initial value, or if the value of the equivalent series resistance increases by a factor of 2.

Characterization of the self-heating of AlGaN/GaN HEMTs during an electrical stress by using Raman spectroscopy

Abstract We report on the non-invasive measurements of the temperature in active AlGaN/GaN HEMTs grown on sapphire substrate during an electrical stress. The original study permits to highlight the drop of the self-heating in operando during the electrical stress by using Raman spectroscopy. Moreover, a correlation between the decrease of the self-heating and the fall of the drain current during the stress has been demonstrated. This study also highlights that the self-heating of the components and the influence of the ageing test on the self-heating are clearly linked to the position where temperature measurements are carried out.

Load impedance influence on the I/sub D/(Y/sub DS/) characteristics of AlGaN/GaN HEMTs in large signal regime at 4 GHz

A measurement system allowing one to put in evidence the trap effects on the power performance of Al/sub 0.1/Ga/sub 0.9/N/GaN high electron mobility transistors (HEMTs) made on sapphire substrate is presented in this paper. This setup permits simultaneous measurements of the output power supplied by the device under test (DUT) and the I/sub D/(V/sub DS/) characteristic in large signal regime at 4 GHz for different load impedances. It shows the traps influence on the maximum drain-current at 4 GHz for different load impedances under large signal operating conditions. The measurements carried out on a device (2/spl times/50/spl times/1 /spl mu/m/sup 2/) have shown a linear decrease of the maximum drain-current when the load impedance increases. These observations make it possible to determine the origin of the power performances difference obtained at microwave frequencies opposite to the static regime.

Annihilation of electrical trap effects by irradiating AlGaN/GaN HEMTs with low thermal neutrons radiation fluence

In this paper, we report on an original method, which permits to change the trap effects on the dc electrical performances of AlGaN/GaN HEMTs. In fact, electrical traps induced by an OFF-stress state on AlGaN/GaN transistors can be strongly reduced by using low thermalized neutrons radiation fluence. We also highlight that a neutron irradiation induces the creation of electrical traps, which act as acceptor. As a result, the electrical behaviour of devices under OFF-state stress is totally different if the component is irradiated or not before the ageing test because electrical traps induced by OFF-state stress can compensate the electrical traps involved by neutron irradiation. To our knowledge, it is the first time that such observation was made.

Influence of Thermal and Fast Neutron Irradiation on dc Electrical Performances of AlGaN/GaN Transistors

The influence of thermal neutron irradiation and fast neutron irradiation on the electrical properties of AlGaN/GaN HEMTs is investigated. An increase in the drain current and a decrease in the access resistances are observed when devices are irradiated with a thermalized neutrons fluence of 4.3 × 1010 neutrons.cm-2 while no evolution is observed with the same fluence of fast neutrons. However, the same phenomenon is observed when the fast neutron fluence is higher (1.8 × 1012 neutrons.cm-2). AlGaN/GaN heterojunctions are analyzed by gamma spectroscopy after thermalized or fast neutron irradiations to understand the physical mechanisms induced by irradiations. In fact, we have shown that the improvement of electrical properties of devices after thermal neutrons irradiation is linked to a Ga-Ge transmutation effect. Moreover, the evolution of the drain current and access resistance when the AlGaN/GaN heterojunctions are irradiated by fast neutrons can be induced by N vacancies creation and/or a change of the strain state of the layers and/or Ga-Ge transmutation effect.

Analysis of Commercial Punch-Through IGBTs Behavior Under

This paper deals with the effects of 60Co gamma irradiation on punch-through commercial insulated gate bipolar transistors turn-off switching behavior. The response of the threshold voltage, the gate-emitter leakage current, the collector leakage current, the collector-emitter breakdown voltage and the turn-off switching parameters under three different in situ gate biases are described. Charge trapping in the gate oxide causes the decrease of the threshold voltage. It is shown that the decrease of this parameter and the modifications in the Miller plateau level and width result in an increase of the turn-off delay time, the collector current fall-time, the collector-emitter voltage rise-time, and consequently an increase of the turn-off switching losses and a decrease of the turn-off overshoot collector-emitter voltage.

^{60}

Abstract This paper deals with the effects of 60 Co gamma irradiation on punch-through commercial insulated gate bipolar transistor turn-on switching behaviour. The response of the threshold voltage and the turn-on switching parameters under three different in situ gate biases are described. Charge trapping in the gate oxide causes the decrease of the threshold voltage. It is shown that the decrease of this parameter and the decrease of the Miller plateau level result in a decrease of the collector current rise-time, the collector–emitter voltage fall-time, the turn-on switching energy and in an increase of the peak of the turn-on switching instantaneous power and of the turn-on overshoot collector current.