In this paper, a fully integrated silicon carbide (SiC)-based six-pack power module is designed and developed. With 1200-V, 100-A module rating, each switching element is composed of four paralleled SiC junction gate field-effect transistors (JFETs) with two antiparallel SiC Schottky barrier diodes. The stability of the module assembly processes is confirmed with 1000 cycles of -40°C to +200°C thermal shock tests with 1.3°C/s temperature change. The static characteristics of the module are evaluated and the results show 55 mΩ on-state resistance of the phase leg at 200°C junction temperature. For switching performances, the experiments demonstrate that while utilizing a 650-V voltage and 60-A current, the module switching loss decreases as the junction temperature increases up to 150°C. The test setup over a large temperature range is also described. Meanwhile, the shoot-through influenced by the SiC JFET internal capacitance as well as package parasitic inductances are discussed. Additionally, a liquid cooled three-phase inverter with 22.9 cm × 22.4 cm × 7.1 cm volume and 3.53-kg weight, based on this power module, is designed and developed for electric vehicle and hybrid electric vehicle applications. A conversion efficiency of 98.5% is achieved at 10 kHz switching frequency at 5 kW output power. The inverter is evaluated with coolant temperature up to 95°C successfully.

Development of a SiC JFET-Based Six-Pack Power Module for a Fully Integrated Inverter

Silicon carbide (SiC) power transistors have started gaining significant importance in various application areas of power electronics. During the last decade, SiC power transistors were counted not only as a potential, but also more importantly as an alternative to silicon counterparts in applications where high efficiency, high switching frequencies, and operation at elevated temperatures are targeted. Various SiC device designs have been proposed and excessive investigations in terms of simulation and experimental studies have shown their advantageous performance compared to silicon technology. On a system-level, however, the design of gate and base drivers for SiC power transistors is very challenging. In particular, a sophisticated driver design is not only associated with properly switching the transistor and decreasing the switching power losses, but also it must incorporate protection features, as well as comply with the electromagnetic compatibility. This paper shows an overview of the gate and base drivers for SiC power transistors which have been proposed by several highly qualified scientists. In particular, the basic operating principle of each driver along with their applicability and drawbacks are presented. For this overview, the three most successful SiC power transistors are considered: junction-field-effect transistors, bipolar-junction transistors, and metal-oxide-semiconductor field-effect transistors. Last but not least, future challenges on gate and base drivers design are also presented.

Gate and Base Drivers for Silicon Carbide Power Transistors: An Overview

Efficiency is a key design parameter when designing the power converters for domestic induction heating applications, since it determines not only the environmental impact of the power converter but also its final performance and reliability. In this paper, the design of high-efficiency converters for induction heating applications is discussed, focusing on the advantages of using wide bandgap devices. As a conclusion, a multiple-output boost resonant ac-ac converter is proposed, significantly improving current state-of-the-art efficiency and achieving a reduced component-count solution for multiple-load systems. The proposed converter has been tested through a dual-output boost resonant inverter for domestic induction heating applications. The design procedure is detailed, including the design of an optimized gate drive circuit for this application. Experimental results show significant improvements in efficiency in the whole operating range, and an accurate output power control, proving the benefits and feasibility of the proposed SiC-based converter.

Design and Implementation of a High-Efficiency Multiple-Output Resonant Converter for Induction Heating Applications Featuring Wide Bandgap Devices

An isolated active-clamp flyback power supply with a new resonant operation mode is designed and experimentally tested. A full soft-switching design based on dead-time optimization new approach is implemented. Each topology phase is detailed. An experimental board is presented for high ambient temperature (200 °C) operation. The power supply is dedicated to provide the driver power of wide bandgap power components in a phase-leg configuration. The constraint for galvanic isolation is high and guides the design of the transformer. The power-supply capabilities are 15 V input voltage, 6 V output voltage, 2 W output power, 75% peak efficiency, 11 cm2 footprint, and nominal operation at 200 °C ambient temperature.

High-Temperature GaN Active-Clamp Flyback Converter With Resonant Operation Mode

The very low on-state resistance, the voltage-controlled gate, and the relative simplicity of fabrication of the normally ON silicon carbide junction field-effect transistor (JFET) make this device the most important player among all state-of-the-art silicon carbide transistors. However, the normally ON nature counts as the main factor which keeps this device far from being considered as an alternative to the silicon insulated-gate bipolar transistor. A self-powered gate driver without external power supply for normally ON silicon carbide JFETs is presented in this paper. The proposed circuit is able to handle the short-circuit currents when the devices are subjected to the dc-link voltage by utilizing the energy associated with this current. On the other hand, it supplies the necessary negative gate-source voltage during the steady-state operation. A detailed description of the operating states in conjunction with a theoretical analysis of the proposed self-powered gate driver is presented. The first part of the experimental investigation has been performed when the proposed circuit is connected to a device which is directly subjected to the dc-link voltage. The second set of measurements were recorded when the self-powered gate-driver was employed as the driver of normally ON components in a half-bridge converter. From the experimental results, it is shown that the short-circuit current is cleared within approximately 20 μs after the dc-link voltage is applied, while the power consumption when all devices are kept in the OFF state equals 0.37 W. Moreover, it is experimentally shown that the proposed gate driver can properly switch when it is employed in a half-bridge converter. Finally, limitations regarding the range of the applications where the self-powered gate drive can efficiently operate are also discussed.

Self-Powered Gate Driver for Normally ON Silicon Carbide Junction Field-Effect Transistors Without External Power Supply

In this paper, the authors propose a solution to provide self protection in a normally-On JFET voltage fed inverter. The solution is a plug-in to an existing Gate driver. An overview of JFET Gate driving serves as an introduction to the problem of self protection of inverters using Normally-On devices.

Normally-On SiC JFETs in power converters: Gate driver and safe operation

This paper reports the design, fabrication and experimental performance of a 2kW, 20kHz, High Temperature, three-phase, all-SiC JFET Voltage Source Inverter (VSI). The inverter includes a specific JFET driver and a DC-link capacitor. All these elements have been validated over a wide temperature range, between 25°C and 200°C. The power device used, a 1200V, 15A, JFET from SiCED has been characterized up to 200°C. An innovative reliable protection circuit for normally-on devices is also presented and validated.

High Temperature Inverter for Airborne Application

Silicon Carbide (SiC) components are accepted devices for high temperature and high efficiency applications. Normally-on SiC JFETs are now commercialized and will be used in future power converters. However, such devices are conducting when not driven with a sufficient negative voltage, which can lead to safety issues during start-up or abnormal operation of the gate driver. Therefore, it is needed to generate an auxiliary negative voltage to turn-off the JFET in order to protect the system. Moreover, insulation is necessary to cover all failure modes. Prior papers presented solution to protect such devices but no high temperature isolated solution were demonstrated. In this paper, a solution to protect JFETs used in a high temperature (200°C) voltage source inverter is proposed. The protection circuit, components selection and characterizations for high temperature application are detailed. Experimental results are provided and validate the design of the isolated normally-on protection circuit up to 200°C.

A high temperature ultrafast isolated converter to turn-off normally-on SiC JFETs

Normally-On Silicon Carbide (SiC) JFETs are good candidates for power switches in high temperature applications, in Three-Phase Voltage-Fed Inverters used to drive Electro-Mechanical Actuators (EMA) for the more electrical aircraft where the ambient varies from -55 °C to 200 °C. The power of the EMA is in the 1 to 5 kW range, the DC bus voltage is 540 V. It is also necessary to implement passive subsystems such as Electro-Magnetic-Interference (EMI) flters, power inductors, transformers, packaging and interconnection solution that withstand the wide temperature range. The gate driver for normally-On devices must include a safe solution against short-circuit in the event of a power supply failure. The experimental converter is built using engineering samples such as SiC JFETs, SOI drivers and laboratory made components such as inductive wire wound, nano-crystalline core components, SOI integrated driver, assembled with a high temperature package and technology. Finally, the Smart EMA test bench is presented.

Sonia Dhokkar

Papers

Normally-On SiC JFETs in power converters: Gate driver and safe operation

High Temperature Inverter for Airborne Application

A high temperature ultrafast isolated converter to turn-off normally-on SiC JFETs

An Airborne High Temperature SiC Power Converter for Medium Power Smart Electro Mechanical Actuators

SIC inverter optimization for high temperature applications