Filippo Chimento

A Physics-Based Model for a SiC JFET Accounting for Electric-Field-Dependent Mobility

In this paper, a physical model for a SiC Junction Field Effect Transistor (JFET) is presented. The novel feature of the model is that the mobility dependence on both temperature and electric field is taken into account. This is particularly important for high-current power devices where the maximum conduction current is limited by drift velocity saturation in the channel. The model equations are described in detail, emphasizing the differences introduced by the field-dependent mobility model. The model is then implemented in Pspice. Both static and dynamic simulation results are given. The results are validated with experimental results under static conditions and under resistive and inductive switching conditions.

Dynamic Characterization of Parallel-Connected High-Power IGBT Modules

In high-power converter design, insulated gate bipolar transistor (IGBT) modules are often operated in parallel to reach high output currents. Evaluating the electrical and thermal behavior of the parallel IGBTs is crucial for the design and reliable operation of converter systems. This paper investigates the static and dynamic characterization of parallel IGBTs and the influence of the electrical parameters on the IGBT behavior. Si-based IGBT power modules with voltage rating of 4.5 kV and current rating of 1 kA are used for the experimental evaluation of module parallel connections. Parallel-connected modules have been driven by several commercial IGBT gate units at various dc-link voltages and current levels and with different temperatures. The tested IGBT gate units show good current sharing performance between the two parallel modules. Other important influencing factors such as busbar design layout, stray inductance variation, and gate driving are also investigated for parallel connections of IGBT modules. Finally, the switching energy of the parallel modules is extracted for IGBTs and diodes under different conditions.

A Physics-Based Model for a SiC JFET Device Accounting for the Mobility Dependence on Temperature and Electric Field

In this work a physical model for a SiC Junction Field Effect Transistor (JFET) is presented. The novel feature of the model is that the mobility dependence on both temperature and electric field is taken into account. This is particularly important for high-current power devices, where the maximum conduction current is limited by drift velocity saturation in the channel. The model equations are described in detail, emphasizing the differences introduced by the field-dependent mobility model. The model is then implemented in Pspice. Both static and dynamic simulation results are given. The results are validated with experimental results under static conditions and under resistive switching conditions.

Super-Junction MOSFET and SiC Diode Application for the Efficiency Improvement in a Boost PFC Converter

This paper deals with the use of the last generation of super-junction (SJ) power MOSFET devices together with silicon carbide (SiC) Schottky diodes in an actual converter application. The main technological issues on the used devices are described and discussed. The impact of the particular features of the devices are analyzed and quantified in a case study regarding a DC-DC boost converter, which is used in a power factor corrector (PFC) converter. The switching transients have been carried out looking for actual applications, and the advantages of the devices are discussed in terms of energy saving and performance improvement. Moreover a comparison between the proposed solution and a traditional one, with reference to the electrical characteristics and the switching performances in a continuous mode 200 W PFC converter, has been carried out. Furthermore some considerations have been presented on the obtainable efficiency improvement of the converter by using the two proposed devices

Electrolyser in H2 Self-Producing Systems Connected to DC Link with Dedicated Phase Shift Converter

In this paper the converter requirements for an optimum control of an electrolyser linked with a DC bus are analyzed and discussed. The hydrogen generating device is part of a complex system constituted by a supplying photovoltaic plant, the grid and a fuel cell battery. The characterization in several operative conditions of an actual industrial electrolyser is carried out in order to design and optimize the DC/DC converter. A dedicated zero voltage switching DC/DC converter is presented and simulated inside the context of the distributed energy production and storage system. The proposed supplying converter gives a stable output voltage and high circuit efficiency in all the proposed simulated scenarios. The adopted DC/DC converter is realized in a full-bridge topology with phase-shift PWM technique in order to achieve zero voltage switching for the power switches and to regulate the output voltage. Furthermore, in order to increase the converter efficiency at the transformer secondary side, a current doubler rectifier is implemented.

A Phase-Shift Full Bridge Converter for the Energy Management of Electrolyzer Systems

The purpose of this work has been the development of the supplying system for an industrial electrolyzer. The hydrogen generating device is part of a complex system constituted by a supplying photovoltaic plant, the grid and a fuel cell battery. The main aim of this electrical system is the hydrogen storage devoted to the suitable load supplying in order to obtain an optimum load profile in case of domestic consumers. The converter is linked to a maximum power point tracking (MPPT) algorithm which enables a converter to extract the maximum power from the photovoltaic plant. The energy is supplied to the electrolyzer or the storage system according to the load profile. A phase-shift control strategy has been adopted and the ZVS at turn on driving strategy, in order to increase the efficiency and thus lowering the power consumption for the whole system. The system has been developed looking for the realization of a dedicated integrated circuits utilization where the control strategy has been implemented.

Robustness Evaluation of High-Voltage Press-Pack IGBT Modules in Enhanced Short-Circuit Test

This paper deals with the evaluation of robustness of high-power press-pack insulated-gate bipolar transistor modules under short-circuit conditions. The severity of the tests is usually related to the achievement of the real failure mode which drives the device to withstand a big amount of energy. The most well-known methods to evaluate the robustness of the devices have been analyzed and improved in order to operate with the highest achievable di/dt and to consequently emulate the real circuit setup and failure mode. Experimental tests will be shown and evaluated under different voltage and temperature conditions. The tests described in this paper have been targeted to evaluate the capability of the device to withstand extremely severe conditions when they are used in a high-power converter. A driving protection feature dealing with the target of improving the functionality of protection against failure will be also described.

Static and dynamic performance assessment of commercial SiC MOSFET power modules

This paper deals with static and dynamic measurements performed with full SiC MOSFET power modules. The voltage rating of the power modules is 1200 V and the current rating is 800 A. The on-resistances (RON) of the power modules were measured to be 6.0-10.0 mΩ, the measured blocking voltages were 1300-1400 V, and the threshold voltages were found to be around 3.0-3.5 V at 300 K. Evaluation of the dynamic performance has been carried out in a double-pulse tester with the use of commercially available gate drivers. A clean (i.e., almost oscillation and overshoot free) turn on and turn off transient behavior is obtained with negligible reverse recovery losses. The measured turn-on and turn-off losses at 800 V, 340 A, were 117 mJ and 40 mJ, respectively. With fixed supply voltage and load current, the energy-loss increases linearly with the gate resistance when varied from 2.5 to 20 mΩ. The energy losses remain insensitive with variation of temperature for a fixed supply voltage and current when tested up to the prescribed junction temperature of 150 °C.

Dynamic characterization of parallel-connected high-power IGBT modules

In high power converter design, IGBT modules are often operated in parallel to reach high output currents. Evaluating the electrical and thermal behaviour of the paralleling IGBTs is crucial for the design and reliable operation of converter systems. This paper investigates the static and dynamic characterization of paralleling IGBTs and the influence of the electrical parameters on the IGBT behaviour. Si based IGBT power modules with voltage rating of 4.5kV and current rating of 1 kA are used for the experimental evaluation of module parallel connections. Parallel connected modules have been driven by several commercial IGBT gate units at various DC-link voltages and current levels and with different temperatures. The tested IGBT gate units show good current sharing performance between the two parallel modules. Other important influencing factors such as busbar design layout, stray inductance variation and gate driving are also investigated for parallel connections of IGBT modules. Finally, the switching energy of the paralleling modules is extracted for IGBTs and diodes under different conditions.

On the Assessment of Temperature Dependence of 10 - 20 kV 4H-SiC IGBTs Using TCAD

This paper addresses and evaluates the temperature dependence performance of silicon carbide (4H-SiC) based insulated gate bipolar transistors (IGBTs) using two dimensional numerical computer aided design tool (i.e., Atlas TCAD from Silvaco). Using identical set of device physical parameters (doping, thicknesses), simulated structure was first caliberated with the experimental data. A minority carrier life time in the drift layer of 1.0 – 1.6 µs and contact resistivity of 0.5 - 1.0 x 10-4 Ω-cm2 produces a close match with the experimental device. A set of n type IGBT structures were then numerically simulated to extract the conduction losses for various blocking voltage classes. An on-resistance first decays with temperature (i.e., increased in ionization level, and increase in minority carrier life time), stays nearly constant with further increase in the temperature (may be all carriers are now fully ionized and increase in carrier life time is compensated with decrease in the carrier mobility) and finally increases linearly with temperature (>450 oC) due to decrease in the carrier mobility. Compared with Si based IGBTs, numerical simulation predicts lower VCEON and RON values for 4H-SiC based IGBTs for higher voltage classes and hence potential for achieving smaller conduction losses for SiC based IGBTs.