Mickael Petit

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

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.

Numerical and Experimental Investigations of the Thermal Management of Power Electronics With Liquid Metal Mini-Channel Coolers

Thermal management became a limiting factor in the development of high-power electronic devices, and new methods of cooling are required. Therefore, the use of liquid gallium alloys, whose thermal conductivity (approximately 28 W/m/K) is 40 times greater than thermal conductivity of water, is introduced. In the first part of this paper, we present a numerical modeling and an experimental study of a mini-channel liquid metal cooler. In these experiments, the working fluid is moved via an electromagnetic pump. Numerical and experimental results are compared. Then, a numerical study dealing with the influence of the thermal conductivity of the cooler material is conducted, and a discussion on the use of classical convective heat transfer correlations is presented. In the last part, a numerical study of the cooling of a silicon chip is carried out. The cooling capacity of the liquid metal is compared with that of the water cooling, and very attractive results are obtained. The concept discussed in this paper is expected to provide a powerful cooling strategy for high-power-density electronic devices.

Study and realization of a high power density electronics device cooling loop using a liquid metal coolant

Thermal management became the limiting factor in the development of high power electronic devices and new methods of cooling are required. Due to the low thermal conductivity of classical liquids (water, alcohols, dielectric fluids…), in many cases, the standard liquid cooling techniques cannot achieve the required cooling performances. Therefore the use of liquid gallium alloys whose thermal conductivity (approx. 28W/m/K) is 40 times greater than thermal conductivity of water, is introduced. In the first part of this paper, we present a numerical modeling and an experimental study of a minichannel liquid metal cooler. In these experiments, the working fluid is moved via an electromagnetic pump. Numerical and the experimental results are compared. Then we present a numerical study showing that the cooler performances depend largely on the thermal conductivity of its constitutive material. In the last part we present a numerical study of a silicon chip cooling. Simulations with different flow rates and heat powers were performed. The cooling capacity of the liquid metal is compared with that of the water cooling and very attractive results were obtained. The concept discussed in this paper is expected to provide a powerful cooling strategy for high power density electronic devices.

Decoupled PQ control applied to a multicellular parallel inverter for grid-connected photovoltaic system

This paper presents the decoupled active and reactive power control (PQ control), using a Phase-Locked Loop (PLL) for synchronization, and applied to the control of Multicellular Parallel Inverter (MPI) for a grid-connected Photovoltaic (PV) system. We explain the value of this multicellular structure of inverter compared to a conventional inverter. We also present and discuss the simulation results obtained using the Matlab software (Simulink and simpowersystems).

Instrumented chip dedicated to semiconductor temperature measurements in power electronic converters

Temperature measurement of semiconductor components is essential, in particular to evaluate performances and to propose health monitoring of power modules. ThermoSensitive Electrical Parameters (TSEPs) are widely used to estimate a representative temperature of these components, mainly in non-operating conditions, different from the real environment of the latter (offline measurements). Nevertheless, some TSEPs may be adapted to online temperature measurements, in operating conditions of power converters. It is however difficult to evaluate the accuracy of those TSEPs. This paper presents an instrumented chip dedicated to estimate the temperature in power electronic modules under functional constraints. Thus, it offers a reliable and robust tool for temperature measurements in power electronic converters. Preliminary results presented in this paper concern the technological process of realization and demonstrate the good functioning of this instrumented chip under power dissipation and switching conditions.

Experimental investigation on heat transfer enhancements in laminar flow with ferrofluids — Application to power electronics cooling

This paper presents an experimental investigation on forced convective heat transfers in a ferrofluid with the presence of a magnetic field. The duct is square, the flow is laminar and the wall heat flux is uniform. The effects of the direction of the magnetic field and of the thermal entrance region are studied. The results show that a better enhancement is made when the magnetic field and the heat flux are perpendicular. Moreover, the effect of the magnetic field seems to be more interesting for a fully developed flow. In the end of the paper, the thermal characterization of a 3D power electronics module cooled by the same ferrofluid is carried out.

Experimental investigation of the reliability of Printed Circuit Board (PCB)-embedded power dies with pressed contact made of metal foam

Abstract A Printed Circuit Board (PCB)-embedding process using pressed metal foam to connect the top-side pads of power dies is considered. The manufacturing process, simple and highly cost-effective, is described in detail; samples are manufactured and their reliability and robustness are characterised. It is shown that thermally cycled prototypes exhibit reliability close to that of Direct Bounded Copper (DBC) substrates. Samples submitted to 150 A-surges have highly scattered reliability. SiC MOSFETs submitted to destructive current limiting tests and repetitive short-circuit tests performed similarly to dies reported in TO247 packages. A discussion on the development of reliability-assessment-methods, especially suited for PCB-embedding processes, is proposed.

Balanced Active and Reactive Control Applied to a Grid Connected Five Level Inverter

This paper presents a balanced active and reactive power control, using a Phase Locked Loop for synchronization, and applied to a grid connected Five Level Inverter. The energy source of the system can be a photovoltaic generator or a wind turbine. We size the passive elements of the system and explain the value of the system architecture using a Five Level Inverter when compared to a classical grid connected system. We also compare the balanced active and reactive power control to an unbalanced active and reactive power control. The simulation results obtained by using Matlab Simulink and Simpowersystems are presented and discussed in this paper.

Using Laminated Metal Foam as the Top-Side Contact of a PCB-Embedded Power Die

The proposed innovative manufacturing process—described in detail—uses metal foam to create a pressed contact between the top side of a printed circuit board-embedded power die and the rest of the circuit. Initial prototypes were constructed using diodes with die dimensions of 4 mm

Realization and characterization of instrumented power diode with aluminum RTD sensor – application to thermal impedance evaluation

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