Jean-Jacques Huselstein

Ageing and Failure Modes of IGBT Modules in High-Temperature Power Cycling

This paper presents an experimental study on the ageing of insulated-gate bipolar transistor (IGBT) power modules. The aim is to identify the effects of power cycling on these devices with high baseplate temperatures (60 °C to 90 °C) and wide temperature swings (60 °C to 100 °C). These values for thermal stresses have been defined according to automotive applications. The test conditions are provided by two types of test benches that will be described in this paper. The changes in electrical and thermal indicators are observed regularly by a monitoring system. At the end of the test (reaching damage criterion or failure), different analyses are performed (acoustic scanning and SEM imaging), and the damage is listed systematically. Nineteen samples of 600-V 200-A IGBT modules were thus aged using five different power-cycling protocols. The final summary of results shows that ageing mechanisms mainly concern wire bonds and emitter metallization, with gradual impact depending on protocol severity.

Frequency-Synchronized Resonant Converters for the Supply of Multiwinding Coils in Induction Cooking Appliances

The induction heating principle has been successfully introduced for about 20 years in domestic cooking appliances. The technical developments now concern the improvement of the current appliances and the introduction of new functions. So, one tendency is the design of multiwinding induction coils that are very adaptive concerning the shape and the power capability. This paper describes different original converter topologies designed to supply multiwinding coils, and, in addition, multicoil systems. The proposed topologies are based on particular use and associations of zero-voltage switching series-resonant converters. They are all characterized by a frequency-synchronized operating mode, in order to prevent any acoustic harm that could result from beating frequency-interferences

Evaluation of

The supervision of semiconductor power devices in operation demonstrates an obvious interest to improve the operating safety of electronic power converters used in critical applications. Unfortunately, this is a significant challenge due to the variability of stress conditions on the one hand and to the difficulty to implement accurate measurement systems in power stages on the other. Using VCE measurement as a real-time supervision method is evaluated here by using aging test results obtained on insulated gate bipolar transistor (IGBT) modules stressed by power cycling. These results are related to the aging of bond wires and metallization, on the top part of the module. Results were obtained in original test benches whose characteristics are overviewed briefly in the first part of this paper, along with a description of test conditions. The second part presents selected results extracted from a larger work and focusing on the VCE evolution with respect to degradations of the modules top part. Their analysis highlights the potential of VCE measurement. The last part proposes the principle of a specific system able to achieve real-time VCE supervision in the test benches in operation.

V_{\rm ce}

An original converter composed of interleaved flyback is presented. The cells are interconnected through intercell transformers replacing the standard multi-winding inductors used as insulation and storage magnetic device in the flyback. The combination of the interleaving effects and of the intercell transformer characteristics allows eliminating the mains limitations of the standard flyback due to the low performances of multiwindings inductors. In a first part, the different ways to interleave galvanic insulated converters as forward or flyback are briefly recalled. The second part presents the intercell transformers and shows that they can be used to interconnect interleaved converters cells. In the third and last part, this particular magnetic interconnection is applied to interleaved flyback cells and leads to create an ldquointercell transformer flybackrdquo. Its specific properties and advantages are described. Experimental results, obtained on a 2-kW test bench are finally presented.

Monitoring as a Real-Time Method to Estimate Aging of Bond Wire-IGBT Modules Stressed by Power Cycling

The test and the characterization of medium or high-power electronic converters, under nominal operating conditions, are made difficult by the requirement of high-power electrical source and load. In addition, the energy lost during the test may be very significant. The opposition method, which consists of an association of two identical converters supplied by the same source, one operating as a generator, the other as a receptor, can be a better way to do these test. Another advantage is the possibility to realize accurate measurements of the different losses in the converters under test. In the first part of this paper, the characteristics of the method concerning loss measurements are compared to those of the electrical or calorimetric methods, then it is shown how it can be applied to different types of power electronic converters, choppers, switched mode power supplies, and pulsewidth modulation inverters. In the second part, different examples of studies conducted by the authors, and using this method, are presented. They have varying goals, from the test of soft-switching inverters to the characterization of integrated gate-commutated thyristor (IGCT) devices mounted into 2-MW choppers.

Multicell Interleaved Flyback Using Intercell Transformers

Power-factor-corrector (PFC) converters are now commonly used in low-power supply systems connected to AC networks. In addition to their basic PFC properties, they constitute the best technical solution to directly obtain the compatibility with a large range of AC voltages provided by different distribution networks around the world (typically, from 85 to 265 V rms). It is the main application of these converters. This function is achieved with an additional cost and volume, and this extra price to pay needs to be minimized. In this context, we first recall the main approaches of the design of conventional PFCs based on the boost converter topology. We emphasize the different critical points of the sizing that mainly concern the input choke and the silicon devices, in regard with the choice of the switching frequency. Few ways of improvement are then presented for these conventional PFCs. In a second part, always in the context of a large input voltage range, we consider the possibility to introduce the multi-level concept to reduce the input choke and filters. A solution using a multi-level flying capacitor two-cell converter is presented. It is shown that it can lead to a significant increase of the performances, with several options of sizing which can be suited to different requirements of the applications.

Use of opposition method in the test of high-power electronic converters

A low-input voltage high-power realization is presented with the aim to demonstrate the feasibility and the interest of topologies using intercell transformer. They constitute a promising option to interleave converter stages, and therefore, can answer to the specifications considered in this paper. These specifications require a galvanic insulation and the chosen topology is the Intercell Transformer (ICT) flyback converter, previously proposed by the authors. In a first part, the operating principle of the ICT flyback converter is recalled. The second part presents briefly the main features of the intercell transformer design, more precisely described in a previous paper. This part includes a discussion about the choice of the cell number. The last part presents the design and the implementation of the complete flyback converter using eight cells. A preliminary work concerns the choice, the design, and the test of each cell elements, mainly the transformer and the primary switching stage. In the end, the experimental results are presented and discussed. They demonstrate the potential of this original topology that needs only one level of magnetic components. Considering the suitability of the converter interleaving for the high-power-low-voltage applications, the ICT flyback converter constitutes a good candidate in that field.

Using the multilevel imbricated cells topologies in the design of low-power power-factor-corrector converters

This paper presents the developments and the results of an analytic method elaborated to design isolated intercell transformers. These particular magnetic components are intended for multicell interleaved flyback converters recently proposed and well-suited to low-voltage, high-power applications. A specific 2-D model to evaluate the winding losses is included in the design process. The results, obtained for standard core shapes, allow defining the ranges of the main parameters, number of cells, and switching frequency, required for future realizations.

Design of a 28 V-to-300 V/12 kW Multicell Interleaved Flyback Converter Using Intercell Transformers

Recent uninterruptible power supply (UPS) systems, in the medium power range (a few 100 kW), are based on a three-power stage topology including a rectifier, an inverter, and a dc-dc converter. The dc-dc converter ensures the charger/discharger function necessary for battery management. The monolithic intercell transformer (ICT) described in this paper is dedicated to such a charger/discharger, of which the nominal power is 137 kW. This dc-dc converter is comprised of eight interleaved cells that are interconnected by the ICT. The first part of this paper briefly presents the full UPS system and the topology of the eight-cell charger/discharger arranged around the eight-phase monolithic ICT. The second part suggests a model and emphasizes the design specificities of the monolithic ICT. The final design is provided by an optimization routine, checked in the end by different 2-D and 3-D finite-element simulations, both electromagnetic and thermal. The third part describes the construction of the ICT prototype. It is then placed in a test bench that reproduces the conditions of future operations and provides current balance conditions. Finally, the experimental results obtained for the 137-kW nominal power validate design parameters and confirm the interest of the ICT solution.

Design of Intercell Transformers for High-Power Multicell Interleaved Flyback Converter

This paper proposes a converter topology dedicated to the interconnection between low voltage and high voltage networks or power sources. This topology uses the interleaving principle whose advantages are well known at this point. Its originality stems from the implementation of an isolating intercell transformer (ICT) that provides isolation, filtering, and intercell coupling through a single magnetic stage. The first section of this paper presents two ways to build bidirectional multicell converters, based on classic buck (or boost) cells on one hand, and buck-boost cells on the other. From the nonisolated versions of these two families, the synthesis of isolated versions is achieved by introducing classic two-winding coupled-inductors or transformers. A nonbidirectional isolated ICT version derived from the buck-boost family, the multicell ICT flyback converter, has already been studied and tested. Therefore, the second section describes the isolated multicell ICT converter derived from the buck (or boost) family and constitutes the main contribution of this paper. Its very interesting features regarding high step-up ratio requirements are emphasized, particularly by considering some limitations of the ICT flyback converter. Finally, a 10-kW test bench is presented. This test bench includes eight cells and an ICT created with separated transformers, making it possible to validate converter operations under realistic power conditions.