SiC MOSFET Module Research Articles

The Influence to Uniform Current Distribution of SiC MOSFET Modules Based on the 3rd Quadrant Characteristics

This paper concentrated on the 3rd quadrant characteristics of 1200V/300A full SiC MOSFET modules produced by four SiC mainstream manufacturers; and compared the diode forward voltage (VSD) performances of “SiC MOSFET only” and SiC MOSFETs modules with SiC Schottky barrier parallel diode. The characteristics of the diode forward voltage showed that module A exhibits the same trend with the PiN diode, whereas modules B, C and D exhibit the characteristics of SBD. Through the failure analysis, it was verified that there is no parallel SBD in module A, meanwhile, it was assumed that modules B, C and D integrate a positive temperature characteristic SBD by wire bonding. The existence of SBD can prevent the modules from burning out due to excessive heating caused by non-uniform current distribution. From the analysis, it illustrated that the body diode can be used as the parallel SiC SBD, but further research on the uniform current distribution of the the body diode is needed.

Parasitic-Based Active Gate Driver Improving the Turn-On Process of 1.7 kV SiC Power MOSFET

This article discusses an active gate driver for a 1.7 kV/325 A SiC MOSFET module. The main purpose of the driver is to adjust the gate voltage in specified moments to speed up the turn-on cycle and reduce the amount of dissipated energy. Moreover, an adequate manipulation of the gate voltage is necessary as the gate current should be reduced during the rise of the drain current to avoid overshoots and oscillations. The gate voltage is switched at the right moments on the basis of the feedback signal provided from a measurement of the voltage across the parasitic source inductance of the module. This approach simplifies the circuit and provides no additional power losses in the measuring circuit. The paper contains the theoretical background and detailed description of the active gate driver design. The model of the parasitic-based active gate driver was verified using the double-pulse procedure both in Saber simulations and laboratory experiments. The active gate driver decreases the turn-on energy of a 1.7 kV/325 A SiC MOSFET by 7% comparing to a conventional gate driver (VDS = 900 V, ID = 270 A, RG = 20 Ω). Furthermore, the proposed active gate driver lowered the turn-on cycle time from 478 to 390 ns without any serious oscillations in the main circuit.

Aging Diagnosis of Bond Wire Using On-State Drain-Source Voltage Separation for SiC MOSFET

Bond wire aging is a universal failure form of silicon carbide metal-oxide-semiconductor field-effect transistor (SiC MOSFET) module. Real-time condition monitoring of bond wire is an important guarantee for the stable operation of power electronics system. In this article, a method of monitoring the aging state of bond wire in SiC MOSFET module using on-state drain-source voltage (OSDSV) separation technique is proposed. Firstly, the temperature dependence of the conduction circuit resistance from drain terminal to source terminal in SiC MOSFET module is analyzed to obtain the temperature characteristics of the OSDSV. Secondly, the resistance of the package structure in SiC MOSFET module is extracted, and the OSDSV is divided into two parts: the package structure voltage and the chip OSDSV, and the analytical model for estimating the junction temperature of SiC MOSFET module in the healthy state is acquired. Finally, the package structure voltage is employed to monitor the aging degree of bond wire in SiC MOSFET module, and the flow chart of aging diagnosis of bond wire is established. The proposed method can accurately identify the failure state of bond wire lift-off. Theoretical and experimental results prove that the method is feasible.

Wideband Modeling of Power SiC MOSFET Module and Conducted EMI Prediction of MVDC Railway Electrification System

Wideband Modeling of Power SiC MOSFET Module and Conducted EMI Prediction of MVDC Railway Electrification System

Active Gate Driver for Improving Current Sharing Performance of Paralleled High-Power SiC MOSFET Modules

Featuring higher switching speed and lower losses, the silicon carbide MOSFETs (SiC MOSFETs) are widely used in higher power density and higher efficiency power electronic applications as a new solution. Due to the limited current capability of a single module, more modules parallel-connected are necessary for higher power application. However, current sharing is the key obstacle. In this article, an active gate driver (AGD) for high-power SiC MOSFETs is presented to balance the currents of parallel-connected SiC MOSFET modules. The principle of the AGD is based on dynamic gate drive voltage adjustment to synchronize current edges and current slopes among parallel-connected SiC MOSFET modules automatically. Each AGD measures and controls the current of its SiC MOSFET module individually. No extra supervising control circuit is needed. In addition, the hardware and software configurations are independent of the system design and no restrictions on the number of SiC MOSFET modules connected in parallel exist. Finally, the switching performance of the AGD was experimentally verified on two parallel-connected SiC MOSFET modules in a multipulse test under constant and variable load currents. In addition, the effectiveness of AGD under different control topologies has been studied with simulation and verified using three parallel-connected SiC MOSFET modules.

Wideband Modeling of Power SiC mosfet Module and Conducted EMI Prediction of MVDC Railway Electrification System

The SiC mosfet in the medium-voltage direct-current (MVdc) transportation electrification system features faster switching performance, while simultaneously binging more significant electromagnetic interference (EMI) issues within the rolling stocks, substations, and radiated disturbance into space along the catenaries and tracks. Due to the necessity to involve both the transient characteristics of power semiconductor devices and the stray parameters of all the equipment in the analysis of EMI, it is considerably challenging to perform wideband device-level simulation on traditional commercial software for such a complex system with numerous trains and stations. A computationally efficient method for wideband modeling and simulation of the MVdc high-speed railway system for the assessment of conducted EMI during the project design stage is proposed in this article. Physical characteristics of the semiconductor devices, parasitic parameters of the mosfet package, and converter topology are all taken into consideration to provide not only accurate system-level performance of the system but also an insight into high-frequency characteristics under different operation conditions. The calculation burden is alleviated by a hierarchical circuit partitioning architecture based on the frequency-dependent time-domain transmission line model and the Norton equivalent parameter extraction of each mosfet module to split the whole system into several smaller subcircuits in terms of matrix size, and a fully parallel implementation of the MVdc system is carried out on the graphics processor. The developed program is used to study the case of Jing–Zhang high-speed railway system topology, which is compatible to be modified to the MVdc project. Simulation results show that it is essential to estimate the EMI level comprehensively considering the alternative of speed and dc voltage.

High-Density Current-Transformer-Based Gate-Drive Power Supply With Reinforced Isolation for 10-kV SiC MOSFET Modules

With features such as faster switching frequency and higher breakdown voltage, wide bandgap power devices are key enablers to address the increasing demand for higher power density and higher efficiency in future medium-voltage converters. The 10-kV SiC MOSFET is one of such devices; yet, to fully utilize its benefits, a gate-drive power supply capable of meeting the necessary insulation (voltage) and isolation ( dv/dt voltage slew rate) requirements is needed. To this end, this article presents the complete design and optimization of such a power supply meeting four critical objectives: 1) high power density with high-voltage (HV) insulation; 2) minimum input–output capacitance; 3) fault ride-through capability; and 4) good voltage regulation. To this end, a GaN-based inductor-capacitor-capacitor-inductor (LCCL)- LC resonant converter switching at 1 MHz was used to produce a resonant current source and to supply multiple isolated loads (gate-drivers) through the single-turn primary winding loop. Experimental results are shown demonstrating the attained power density (6.3 W/in3), input–output capacitance (1.67 pF), peak efficiency (86.0%), short- and open-circuit fault withstanding capacity, and insulation rating (partial discharge inception voltage of 12 kV).

A Novel Active Gate Driver for Improving Switching Performance of High-Power SiC MOSFET Modules

Featuring higher switching speed and lower losses, the silicon carbide mosfet s (SiC mosfet s) are widely used in higher power density and higher efficiency power electronic applications as a new solution. However, the increase of the switching speed induces oscillations, overshoots, electromagnetic interference (EMI), and even additional losses. In this paper, a novel active gate driver (AGD) for high-power SiC mosfet s is presented to fully utilize its potential of high-speed characteristic under different operation temperatures and load currents. The principle of the AGD is based on drive voltage decrement during the voltage and current slopes since high dV/dt and dI/dt are the source of the overshoots, oscillations, and EMI problems. In addition, the optimal drive voltage switching delay time has been analyzed and calculated considering a tradeoff between switching losses and switching stresses. Compared to conventional gate driver with fixed drive voltage, the proposed AGD has the capability of suppressing the overshoots, oscillations, and reducing losses without compromising the EMI. Finally, the switching performance of the AGD was experimentally verified on 1.2 kV/300 A and 1.7 kV/300 A SiC mosfet s in double pulse test under different operation temperatures and load currents. In addition, an EMI discussion and cost analysis were realized for AGD.

Design, Analysis, and Discussion of Short Circuit and Overload Gate-Driver Dual-Protection Scheme for 1.2-kV, 400-A SiC MOSFET Modules

This paper proposes short circuit and overload gate-driver dual-protection scheme based on the parasitic inductance between the Kelvin- and power-source terminals of high-current SiC mosfet modules. The paper presents a comprehensive analysis of the two schemes in question, including worst-case analysis used to assess their parametric dependence due to manufacturing tolerances and temperature variations, as well as the in-depth design procedure that can be generally applied to any power module containing a Kelvin-source. For verification, a compact 1.2-kV, 400-A half-bridge module integrating the two protection circuits was developed. The results obtained demonstrate a response time within tens of nanoseconds, and effectively validate their functionality under short circuit and overload scenarios. Finally, a 100-kW, 400-V dc three-phase voltage-source inverter was used to demonstrate the gate-driver with integrated protection functions under 105°C ambient temperature conditions.

A Novel Non-Intrusive Technique for BTI Characterization in SiC mosfets

Threshold voltage ( V TH) shift due to bias temperature instability (BTI) is a well-known problem in SiC mosfet s that occurs due to oxide traps in the SiC/SiO2 gate interface. The reduced band offsets and increased interface/fixed oxide traps in SiC mosfet s makes this a more critical problem compared to silicon. Before qualification, power devices are subjected to gate bias stress tests after which V TH shift is monitored. However, some recovery occurs between the end of the stress and V TH characterization, thereby potentially underestimating the extent of the problem. In applications where the SiC mosfet module is turned off with a negative bias at high temperature, if the V TH shift is severe enough, there may be electrothermal failure due to current crowding since parallel devices lose synchronization during turn- on . In this paper, a novel method that uses the forward voltage of the body diode during reverse conduction of a small sensing current is introduced as a technique for monitoring V TH shift and recovery due to BTI. This non-invasive method exploits the increased body effect that is peculiar to SiC mosfet s due to the higher body diode forward voltage. With the proposed method, it is possible to non-invasively assess V TH shift dynamically during BTI characterization tests.

Optimised design consideration of suspension choppers in Maglev train using SiC MOSFET modules

Electromagnetic suspension (EMS) Maglev trains attracted to suspend above a track is a green type of track transportation. The suspension control box adopting a closed-loop feedback controller outputs a levitation current that flows into the electromagnets producing a desired magnetic force to levitate the train. Without contact frictions, such a promising type of transportation saves considerable electricity for propulsion. Minimising the volume and weight of Maglev trains attracts great research interests and continuous engineering effort as that is closely correlated with levitation power consumption and, more importantly, the construction cost. This paper mainly discusses volume and weight optimisation of suspension control box that contains a suspension chopper in EMS Maglev trains using the state-of-the-art SiC MOSFET modules. By analysing the mission profile of a typical suspension chopper, SiC MOSFET is found to be perfectly suitable for suspension chopper optimisation because of its low power losses. An optimised heatsink design of suspension chopper is given, whose volume is only 21% of the previous design. By utilising a RC snubber, the new SiC MOSFET suspension chopper prototype is built without showing serious voltage ringing. This provides a promising prospect for further optimisation of suspension control systems.

Merits of SiC MOSFETs for high-frequency soft-switched converters, measurement verifications by both electrical and calorimetric methods

ABSTRACTThis paper quantifies the soft switching loss of a 1.2 kV SiC MOSFET module via a calorimetric method in a 78 kW full-bridge resonant inverter switched at approximately 200 kHz. By switching the SiC MOSFET just before the zero crossing of the current during turn-off and at perfect zero voltage during turn-on, this converter yielded an efficiency of roughly 99 %. Then, a simplified laboratory setup, including only a half-bridge series resonant inverter topology with split DC-link capacitors and an LC load, was built such that a real inverter operation was emulated, and thereby, turn-off loss was measured via an electrical method. A discrepancy of approximately 10 % is found between the two loss measurement methods, and the possible source for this difference is discussed. Furthermore, a standard double pulse test was also performed in an inductive clamped buck converter for measuring the hard switching loss. Finally, a comparison of losses obtained from the hard versus resonant topologies at the same load current was accomplished, which verifies the substantial benefits of the latter over the former. Thus, the merits of SiC MOSFETs for high frequency soft switched converters are demonstrated, which is the main contribution of this paper.

Thermal Performance Evaluation of a 1.7-kV, 450-A SiC-MOSFET Based Modular Three-Phase Power Block With Wide Fundamental Frequency Operations

To accelerate wide industry adoption of Silicon Carbide (SiC) based technology, a three-phase two-level inverter based power block is designed with the latest generation high performance 1.7 kV/450 A SiC-Mosfet module from General Electric. The designed power block is expected to replace the currently standardized 1.7 kV/450 A Silicon (Si) insulated gate bipolar transistor (IGBT) based three-phase power block. Power converters face thermal challenges when subjected to very low fundamental frequency operations (below 10 Hz). This is particularly relevant in the wind power applications. At low operating fundamental frequencies, the junction temperature of the power device experiences high peak-to-peak ripple, which degrades the reliability of the power modules significantly. This paper presents the thermal performance of the designed power block and draws comparisons with a similar rated Si-IGBT module based power blocks, especially at low output fundamental frequency operations. Key performance indices, including power rating curves at different switching frequencies and power factors; temperature ripple at different fundamental frequencies, are examined. Simulation and experimental results are provided to validate the claims. The results indicate that the SiC-Mosfet module based power block can be a promising replacement for the Si-IGBT based power block especially in applications where wide range of fundamental frequency operations are needed.

Development of high power SiC devices for rail traction power systems

Si-based power devices have been widely used in electric locomotive and EMU, however, there are urgent requirements from the industry to have power converters with smaller size and higher performance. To meet such demands, wide band-gap (WBG) devices such as SiC power chips and modules are developed for the traction systems, and a 1.7 kV hybrid SiC power module has been used in Metro system and all SiC 3.3 kV power module has been developed. In this paper, the development of hybrid SiC and all SiC power modules are introduced from the perspectives of devices, modules and applications. SiC SBD and MOSFET chips and modules are manufactured and tested, both static and dynamic testing results are evaluated and showed that SiC devices present better performance and higher efficiency than the traditional Si IGBT modules, especially in the conditions of high temperature and high operation frequency. Based on the developed SiC modules, the urgent demand of traction converters with smaller size and lighter weight can be achieved while present advantages such as higher efficiency, power density, operation temperatures and frequency. The current challenges of SiC devices and future applications are discussed for the next generation of rail transportation.

On-line solder layer degradation measurement for SiC-MOSFET modules under accelerated power cycling condition

In order to distinguish die-attach solder layer and bond wire degradation during power cycling tests, a simultaneous on-line measurement method is proposed in this paper. To measure accurately solder layer voltage drop, the intrinsic diode is used as heating source in place of the MOSFET switch. In this way, the measurement method becomes intrinsically insensitive to possible threshold voltage shifts, typical of accelerated test of SiC power MOSFETs. Finally, the experimental results are presented to verify the feasibility of the proposed test method. It is revealed that the solder layer resistance increases linearly with the number of cycles in good approximation.

A Damping Scheme for Switching Ringing of Full SiC MOSFET by Air Core PCB Circuit

In this paper, a resonant damping circuit to suppress the switching ringing of full SiC mosfet is proposed. It reveals that the ringing phenomenon caused by parasitic impedances of switching circuit can be damped out using air core PCB transformer which has a properly designed secondary side circuit. The design method for PCB transformer and the secondary circuit are developed considering the physical dimension applied to the PCB transformer inserted between full SiC mosfet module and snubber capacitor. Experimental results using 1200 V–180 A full SiC mosfet module validate the design method and the performance of the proposed air core PCB circuit. Thanks to the damping circuit, the resonant component due to the switching ringing has been reduced to a half compared to that of system without damping circuit.

Accurate Transient Calorimetric Measurement of Soft-Switching Losses of 10-kV SiC mosfets and Diodes

The characterization of soft-switching losses (SSL) of modern high-voltage SiC mosfet s is a difficult but necessary task in order to provide a sound basis for the accurate modeling of converter systems, such as medium-voltage-connected solid-state transformers, where soft-switching techniques are employed to achieve an improved converter efficiency. Switching losses (SL), in general, are typically measured with the well-known double pulse method. In the case of SSL measurements, however, this method is very sensitive to the limited accuracy of the measurement of the current and voltage transients, and thus is unsuitable for the characterization of fast-switching high-voltage mosfet s. This paper presents an accurate and reliable calorimetric method for the determination of SSL using the example of 10-kV SiC mosfet modules. Measured SSL curves are presented for different dc-link voltages and switched currents. Furthermore, a deeper analysis concerning the origin of SSL is performed. With the proposed measurement method, it can be experimentally proven that the largest share of the SSL arises from charging and discharging the output capacitance of the mosfet module and especially of the antiparallel junction barrier Schottky diode.

A hybrid Si IGBT and SiC MOSFET module development

A compact wirebond packaged phase-leg SiC/Si hybrid module was designed, developed, and tested. Details of the layout and gate drive designs are described. The IC chip for gate drive is carefully selected and compared. Dual pulse test confirmed that, the switching loss of hybrid module is close to pure SiC MOSFET module, and it is much less than pure Si IGBT device. The cost of hybrid module is closer to Si IGBT.

Loss Model and Efficiency Analysis of Tram Auxiliary Converter Based on a SiC Device

Currently, the auxiliary converter in the auxiliary power supply system of a modern tram adopts Si IGBT as its switching device and with the 1700 V/225 A SiC MOSFET module commercially available from Cree, an auxiliary converter using all SiC devices is now possible. A SiC auxiliary converter prototype is developed during this study. The author(s) derive the loss calculation formula of the SiC auxiliary converter according to the system topology and principle and each part loss in this system can be calculated based on the device datasheet. Then, the static and dynamic characteristics of the SiC MOSFET module used in the system are tested, which aids in fully understanding the performance of the SiC devices and provides data support for the establishment of the PLECS loss simulation model. Additionally, according to the actual circuit parameters, the PLECS loss simulation model is set up. This simulation model can simulate the actual operating conditions of the auxiliary converter system and calculate the loss of each switching device. Finally, the loss of the SiC auxiliary converter prototype is measured and through comparison it is found that the loss calculation theory and PLECS loss simulation model is valuable. Furthermore, the thermal images of the system can prove the conclusion about loss distribution to some extent. Moreover, these two methods have the advantages of less variables and fast calculation for high power applications. The loss models may aid in optimizing the switching frequency and improving the efficiency of the system.

Comparison of the electro-thermal constraints on SiC MOSFET and Si IGBT power modules in photovoltaic DC/AC inverters

This article presents a comparative study between SiC MOSFETs and Si IGBTs regarding changes in their junction temperature in a PV inverter application. The estimation of these variations is made by introducing the current mission profiles extracted from a photovoltaic plant over one year into a calculation tool. The latter is based on a losses model and a thermal model including a coupling between them. The calculation of the losses in SiC MOSFETs in the 3rd quadrant is detailed. The results are the mission profiles of the junction temperature of semiconductors, which allow for determining and comparing the thermal constraints in SiC MOSFET and Si IGBT power modules.