Scott Leslie

10 kV, 120 A SiC half H-bridge power MOSFET modules suitable for high frequency, medium voltage applications

The majority carrier domain of power semiconductor devices has been extended to 10 kV with the advent of SiC MOSFETs and Schottky diodes. The devices exhibit excellent static and dynamic properties with encouraging preliminary reliability. Twenty-four MOSFETs and twelve Schottky diodes have been assembled in a 10 kV half H-bridge power module to increase the current handling capability to 120 A per switch without compromising the die-level characteristics. For the first time, a custom designed system (13.8 kV to 465/√3 V solid state power substation) has been successfully demonstrated with these state of the art SiC modules up to 855 kVA operation and 97% efficiency. Soft-switching at 20 kHz, the SiC enabled SSPS represents a 70% reduction in weight and 50% reduction in size when compared to a 60 Hz conventional, analog transformer.

Characterization of 15 kV SiC n-IGBT and its application considerations for high power converters

The 4H-SiC n-IGBT is a promising power semiconductor device for medium voltage power conversion. Currently, Cree has successfully built 15 kV n-IGBTs. These IGBTs are pivotal for the smart grid power conversion systems and medium voltage drives. The need for complex multi-level topologies or series connected devices can be eliminated, while achieving reduced power loss, by using the SiC IGBT. In this paper, characteristics of the 15 kV n-IGBT have been reported for the first time. The turn-on and turn-off transitions of the 15 kV, 20 A IGBT have been experimentally evaluated up to 11 kV. This is highest switching characterization voltage ever reported on a single power semiconductor device. The paper includes static characteristics up to 25 A (forward) and 12 kV (blocking). The dependency of the power loss with voltage, current and temperature are provided. In addition, the basic converter design considerations using this ultrahigh voltage IGBT for high power conversion applications are presented. Also, a comparative evaluation is reported with an IGBT with thicker field-stop buffer layer as a means to show flexibility in choosing the IGBT design parameters based on the power converter frequency and power rating specification. Finally, power loss comparison of the IGBTs and MOSFET is provided to consummate the results for a complete reference.

10 kV/120 A SiC DMOSFET half H-bridge power modules for 1 MVA solid state power substation

In this paper, the extension of SiC power technology to higher voltage 10 kV/10 A SiC DMOSFETs and SiC JBS diodes is discussed. A new 10 kV/120 A SiC power module using these 10 kV SiC devices is also described which enables a compact 13.8 kV to 465/√3 solid state power substation (SSPS) rated at 1 MVA.

Roadmap for megawatt class power switch modules utilizing large area silicon carbide MOSFETs and JBS diodes

Recent dramatic advances in the development of large area Silicon Carbide (SiC) MOSFETs along with their companion JBS diode technology make it possible to design and fabricate high power SiC switch modules. An effort underway by the Air Force Research Laboratory has lead to the development of a 1.2kV/100A SiC dual switch power module capable of operating at a junction temperature of 200°C. Two additional efforts are set on achieving the megawatt goal. An effort by the Army Research Laboratory is focused on 1.2kV modules to be used for traction and power conversion applications. The highest power 1200V all-SiC dual switch power modules produced is capable of 880 amps. A DARPA effort to develop a solid state power substation has produced a 10kV/50A SiC dual switch power module. Higher current modules in both voltage ratings have been designed. These SiC MOSFET modules represent the next level of integration for SiC power devices. This is a critical technical milestone in the progression toward highly reliable, high efficiency, power systems. This technology is relevant in the current energy-conscious environment and will translate to significant energy savings for hybrid and electric vehicles, solar power and alternative energy system inverters, and industrial motor drives.

Comparison study of 12kV n-type SiC IGBT with 10kV SiC MOSFET and 6.5kV Si IGBT based on 3L-NPC VSC applications

Silicon Carbide (SiC) devices and modules have been developed with high blocking voltages for Medium Voltage power electronics applications. Silicon devices do not exhibit higher blocking voltage capability due to its relatively low band gap energy compared to SiC counterparts. For the first time, 12kV SiC IGBTs have been fabricated. These devices exhibit excellent switching and static characteristics. A Three-level Neutral Point Clamped Voltage Source Converter (3L-NPC VSC) has been simulated with newly developed SiC IGBTs. This 3L-NPC Converter is used as a 7.2kV grid interface for the solid state transformer and STATCOM operation. Also a comparative study is carried out with 3L-NPC VSC simulated with 10kV SiC MOSFET and 6.5kV Silicon IGBT device data.

Understanding dv/dt of 15 kV SiC N-IGBT and its control using active gate driver

The ultrahigh voltage (> 12 kV) SiC IGBTs are promising power semiconductor devices for medium voltage power conversion due to feasibility of simple two-level topologies, reduced component count and extremely high efficiency. However, the current devices generate high dv/dt during switching transitions because of the deep punch-through design. This paper investigates the behavior of dv/dt during the two-slope (different slopes before and after punch-through) turn-on and turn-off voltage transitions of these devices, by varying the device current, temperature and field-stop buffer layer design. It is shown that the dv/dt can be minimized by increasing the gate resistance, by taking the turn-on transition as reference. However, it is found that the increase in gate resistance has very weak impact on dv/dt above the punch-through voltage, and also resulting in significantly increased switching energy loss. It is shown that this problem can be addressed by using a two-stage active gate driver, where the gate current is appropriately controlled to limit the dv/dt over punch-through voltage and to minimize the switching energy loss under the punch-through voltage. Experimental results on 15 kV SiC N-IGBTs with field-stop buffer layer thickness of 2 μm and 5 μm are presented up to 11 kV with a detailed discussion of the results.

A Hybrid-Switch-Based Soft-Switching Inverter for Ultrahigh-Efficiency Traction Motor Drives

This paper presents a hybrid switch that parallels a power MOSFET and an IGBT as the main switch of a zero-voltage switching inverter. The combination features the MOSFET conducting in the low current region and the IGBT conducting in the high current region, and the soft switching avoids the reverse recovery problem during the device turn-on. A custom hybrid switch module has been developed for a variable-timing controlled coupled-magnetic type ZVS inverter with a nominal input voltage of 325 V and the continuous output power of 30-kW for a traction motor drive. Experimental results of the hybrid-switch based inverter with the total loss projected by temperature indicate that the inverter achieves 99% efficiency at the nominal condition and demonstrate ultrahigh efficiency operation over a wide load range. At 375-V input, the maximum measured efficiency through temperature projection and loss separation analysis is 99.3%.

Experimental switching frequency limits of 15 kV SiC N-IGBT module

This paper presents extensive experimental switching characteristics of a state-of-the-art 15 kV SiC N-IGBT (0.32 cm2 active area) up to 10 kV, 10 A and 175°C. The influence of the thermal resistance of the module package, cooling mechanism, and the increased energy loss with temperature are investigated for determining the switching frequency limits of the IGBT. Detailed FEM analysis is conducted for extracting the thermal resistance of each layer in the 15 kV module from the IGBT junction to the base plate, and then down to the ambient. Using this thermal information and the experimental switching data, the inductive switching frequency limits are analytically evaluated for liquid and air cooling cases with 660 W/cm2 and 550 W/cm2 power dissipation densities respectively, considering 150°C as maximum junction temperature. The air cooling power dissipation density of the 15 kV IGBT is experimentally validated using a dc-dc boost converter at 10 kV, 6.4 kW output and 550 W/cm2 under steady state operating conditions. The gate resistances used for the entire experiments are RG(ON) = 20 Ω and RG(OFF) = 10 Ω.

Medium voltage power converter design and demonstration using 15 kV SiC N-IGBTs

This paper summarizes the different steps that have been undertaken to design medium voltage power converters using the state-of-the-art 15 kV SiC N-IGBTs. The 11 kV switching characterization results, 11 kV high dv/dt gate driver validation, and the heat-run test results of the SiC IGBT at 10 kV, 550 W/cm2 (active area) have been recently reported as individual topics. In this paper, it is attempted to link all these individual topics and present them as a complete subject from the double pulse tests to the converter design, for evaluating these novel high voltage power semiconductor devices. In addition, the demonstration results of two-level H-Bridge and three-level NPC converters, both at 10 kV dc input, are being presented for the first-time. Lastly, the performance of two-chip IGBT modules for increased current capability and demonstration of three-level poles, built using these modules, at 10 kV dc input with sine-PWM and square-PWM modulation for rectifier and dc-dc stages of a three-phase solid state transformer are presented.

Efficiency evaluation of a 55kW soft-switching module based inverter for high temperature hybrid electric vehicle drives application

This paper presents a 55kW three-phase softswitching inverter for hybrid electric vehicle drives at high temperature conditions. Highly integrated softswitching modules have been employed to achieve switching loss as well as conduction loss reduction. Detailed experimental evaluations of inverter efficiency have been conducted through both inductive load and motor-dynamometer load at coolant temperatures ranging from 25°C to 90°C. Efficiency measurement using power meter showed that the peak efficiency is around 99%, and it drops slightly at lower speed and higher temperature conditions. To ensure measurement fidelity, a double chamber differential calorimeter system was designed and calibrated for the inverter testing. Through long-hour testing, the measured efficiencies consistently showed 99% and higher. The soft-switching inverter has been operated reliably and demonstrated high efficiency at different temperature and test conditions.