Design and construction of a half-bridge using wide-bandgap transistors

A continuously increasing demand of electric power makes energy efficiency imperative in modern technology. The transistor is considered as the fundamental element of modern electronic products

Multiple Output Power Supply using Toroidal Transformers for Medium Voltage Active Gate Drivers

When operating in high power applications, power devices dissipate tens or hundreds of watts of power in the form of heat. The ability of the power devices to withstand power and dissipation of heat across the power devices becomes a prominent requirement in designing the power converter. This challenge demands a power converter design to be more effective and consistent which factors in size, cost, weight, power density and reliability. This study aims to propose a gate driver isolated power supply design that can be used in medium voltage applications (e.g., up to 10 kV) while respecting the principle of scalability. A versatile design that facilitates addition of another power switch to the converter if needed, without having to alter too many power supply components while retaining the main structure, thus reducing system complexity and size. The proposed topology is a full-bridge converter with a single-turn primary side transformer, realized using a high voltage insulated hook-up wire as primary winding, while the secondary winding is wound around a toroidal core. This structure can supply several gate drivers simultaneously without replicating the primary side converter, but by simply adding a toroidal core with the secondary side converter which effectively reduces the size of the power supply. To satisfy magnetic and electric constraints, the proposed toroidal transformer needs to exhibit a very low primary to secondary coupling capacitance to avoid high common mode current, which leads to control signal distortion. For this, a multi-objective optimization design has been performed for the magnetic components of the topology. In this paper, a single input and three output power supply design is proposed for a 10 kV active gate driver

Multiple Output Power Supply using Toroidal Transformers for Medium Voltage Active Gate Drivers

When operating in high power applications, power devices dissipate tens or hundreds of watts of power in the form of heat. The ability of the power devices to withstand power and dissipation of heat across the power devices becomes a prominent requirement in designing the power converter. This challenge demands a power converter design to be more effective and consistent which factors in size, cost, weight, power density and reliability. This study aims to propose a gate driver isolated power supply design that can be used in medium voltage applications (e.g., up to 10 kV) while respecting the principle of scalability. A versatile design that facilitates addition of another power switch to the converter if needed, without having to alter too many power supply components while retaining the main structure, thus reducing system complexity and size. The proposed topology is a full-bridge converter with a single-turn primary side transformer, realized using a high voltage insulated hook-up wire as primary winding, while the secondary winding is wound around a toroidal core. This structure can supply several gate drivers simultaneously without replicating the primary side converter, but by simply adding a toroidal core with the secondary side converter which effectively reduces the size of the power supply. To satisfy magnetic and electric constraints, the proposed toroidal transformer needs to exhibit a very low primary to secondary coupling capacitance to avoid high common mode current, which leads to control signal distortion. For this, a multi-objective optimization design has been performed for the magnetic components of the topology. In this paper, a single input and three output power supply design is proposed for a 10 kV active gate driver

A novel active gate driver for improving SiC MOSFET switching trajectory

The trend in power electronic applications is to reach higher power density and higher efficiency. Currently, the wide band-gap devices such as silicon carbide MOSFET (SiC MOSFET) are of great interest because they can work at higher switching frequency with low losses. The increase of the switching speed in power devices leads to high power density systems. However, this can generate problems such as overshoots, oscillations, additional losses, and electromagnetic interference (EMI). In this paper, a novel active gate driver (AGD) for improving the SiC MOSFET switching trajectory with high performance is presented. The AGD is an open-loop control system and its principle is based on gate energy decrease with a gate resistance increment during the Miller plateau effect on gate-source voltage. The proposed AGD has been designed and validated through experimental tests for high-frequency operation. Moreover, an EMI discussion and a performance analysis were realized for the AGD. The results show that the AGD can reduce the overshoots, oscillations, and losses without compromising the EMI. In addition, the AGD can control the turn-on and turn-off transitions separately, and it is suitable for working with asymmetrical supplies required by SiC MOSFETs.Postprint (author's final draft

Design and Switching Performance Evaluation of a 10 kV SiC MOSFET Based Phase Leg for Medium Voltage Applications

10 kV SiC MOSFETs are promising to substantially boost the performance of future medium voltage (MV) converters, ranging from MV motor drives to fast charging stations for electric vehicles (EVs). Numerous factors influence the switching performance of 10 kV SiC MOSFETs with much faster switching speed than their Si counterparts. Thorough evaluation of their switching performance is necessary before applying them in MV converters. Particularly, the impact of parasitic capacitors in the MV converter and the freewheeling diode is investigated to understand the switching performance more comprehensively and guide the converter design based on 10 kV SiC MOSFETs.A 6.5 kV half bridge phase leg based on discrete 10 kV/20 A SiC MOSFETs is designed and fully validated to operate continuously at rated voltage with dv/dt up to 80 V/ns. Based on the phase leg, the impact of parasitic capacitors brought by the load inductor and the heatsink on the switching transients and performance of 10 kV SiC MOSFETs is investigated. Larger parasitic capacitors result in more oscillations, longer switching transients, as well as higher switching energy loss especially at low load current. As for the freewheeling diode, the body diode of 10 kV SiC MOSFETs is suitable to serve as the freewheeling diode, with negligible reverse recovery charge at various temperatures. The switching performance with and without the anti-parallel SiC junction barrier Schottky (JBS) diode is compared quantitatively. It is not recommended to add an anti-parallel diode for the 10 kV SiC MOSFET in the converter because it increases the switching loss

Switching Performance Evaluation, Design, and Test of a Robust 10 kV SiC MOSFET Based Phase Leg for Modular Medium Voltage Converters

10 kV SiC MOSFETs are one of the most promising power semiconductor devices for next-generation high-performance modular medium voltage (MV) converters. With extraordinary device characteristics, 10 kV SiC MOSFETs also bring a variety of challenges in the design and test of MV converters. To tackle these inherent challenges, this dissertation focuses on a robust half bridge (HB) phase leg based on 10 kV SiC MOSFETs for modular MV converters. A baseline design and test of the phase leg is established first as the foundation of the research in this dissertation. Thorough evaluation of 10 kV SiC MOSFETs’ switching performance in a phase leg is necessary before applying them in MV converters. The impact of parasitic capacitors and the freewheeling diode is investigated to understand the switching performance more extensively and guide the converter design. One non-negligible challenge is the flashover fault resulting from the premature insulation breakdown, a short circuit fault with extremely fast transients. A device model is established to analyze the behavior of 10 kV SiC MOSFETs when the fault occurs in a phase leg thoroughly. Subsequently, the gate driver and protection design considerations are summarized to achieve lower short circuit current and overvoltage and ensure the survival of the MOSFET that in ON state when the fault happens. Furthermore, it is challenging to design the overcurrent/short circuit protection with fast response and strong noise immunity under fast switching transients for 10 kV SiC MOSFETs. The noise immunity of the desaturation (desat) protection is studied quantitatively to provide design guidelines for noise immunity enhancement. Then, the protection scheme based on desat protection is developed and validated withimmunity, the strong noise immunity of the developed protection is also successfully validated. In addition, a simple test scheme is proposed and validated experimentally, in order to qualify the HB phase leg based on the 10 kV SiC MOSFET comprehensively for the modular MV converter applications. The test scheme includes the ac-dc continuous test with two phase legs in series to create the testing condition similar to what is generated in a modular MV converter, especially the high dv/dt. The test scheme can fully test the capability of the phase leg to withstand high dv/dt and its resulting noise

Switching Trajectory Control for High Voltage Silicon Carbide Power Devices with Novel Active Gate Drivers

The penetration of silicon carbide (SiC) semiconductor devices is increasing in the power industry due to their lower parasitics, higher blocking voltage, and higher thermal conductivity over their silicon (Si) counterparts. Applications of high voltage SiC power devices, generally 10 kV or higher, can significantly reduce the amount of the cascaded levels of converters in the distributed system, simplify the system by reducing the number of the semiconductor devices, and increase the system reliability. However, the gate drivers for high voltage SiC devices are not available on the market. Also, the characteristics of the third generation 10 kV SiC MOSFETs with XHV-6 package which are developed by CREE are approaching those of an ideal switch with high dv/dt and di/dt. The fast switching speed of SiC devices introduces challenges for the application since electromagnetic interference (EMI) noise and overshoot voltage can be serious. Also, the insulation should be carefully designed to prevent partial discharge. To address the aforementioned issues, this work investigates the switching behaviors of SiC power MOSFETs with mathematic models and the formation of EMI noise in a power converter. Based on the theoretical analysis, a model-based switching trajectory optimizing three-level active gate driver (AGD) is proposed. The proposed AGD has five operation modes, i.e., faster/normal/slower for the turn-on process and slower/normal for the turn-off process. The availability of multiple operation modes offers an extra degree of freedom to improve the switching performance for a particular application and enables it to be more versatile. The proposed AGD can provide higher switching speed adjustment resolution than the other AGDs, and this feature will allow the proposed AGD to fine tune the switching speed of SiC power devices. In addition, a novel model-based trajectory optimization strategy is proposed to determine the optimal gate driver output voltage by trading the EMI noise against the switching energy losses. For the 10 kV SiC power MOSFET, the detailed design considerations of the proposed AGD are demonstrated in this dissertation. The functionalities of the 3-L AGD are validated through the double pulse tests results with 1.2 kV and 10 kV SiC power MOSFETs

Evaluation of Losses in HID Electronic Ballast Using Silicon Carbide MOSFETs

HID lamps are used in applications where high luminous intensity is desired. They are used in a wide range of applications from gymnasiums to movie theatres, from parking lots to indoor aquaria, from vehicle headlights to indoor gardening. They require ballasts during start-up and also during operation to regulate the voltage and current levels. Electronic ballasts have advantages of less weight, smooth operation, and less noisy over electromagnetic ballasts. A number of topologies are available for the electronic ballast where control of power electronic devices is exploited to achieve the performance of a ballast for lighting. A typical electronic ballast consists of a rectifier, power factor control unit, and the resonant converter unit. Power factor correction (PFC) was achieved using a boost converter topology and average current mode control for gate control of the boost MOSFET operating at a frequency of 70 kHz. The PFC was tested with Si and SiC MOSFET at 250 W resistive load for varying input from 90 V to 264 V. An efficiency as high as 97.4% was achieved by Si MOSFET based PFC unit. However, for SiC MOSFET, the efficiency decreased and was lower than expected. A maximum efficiency of 97.2% was achieved with the SiC based PFC. A simulation model was developed for both Si and SiC MOSFET based ballasts. The efficiency plots are presented. A faster gate drive for SiC MOSFET could improve the efficiency of the SiC based systems

Converter- and Module-level Packaging for High Power Density and High Efficiency Power Conversion

Advancements in the converter- and module-level packaging will be the key for the development of the emerging high-power, high power-density, high-eciency power conversion applications, such as traction, shipboards, more-electric-aircraft, and locomotive. Wide bandgap (WBG) devices such as silicon carbide (SiC) MOSFET attract much attention in these applications for their fast switching speeds, resulting in low loss and a consequent possibility for high switching frequency to increase the power density. However, for high-current, high power implementations, WBG devices are still available in small die sizes. Multiple SiC devices need to be connected in parallel to replace a large IGBT die. It is challenging to realize high-switching-frequency and low loss with a lot of parallel devices due to the inherent parameter dierences, which lead to unbalanced dynamic current sharing resulting in unequal temperature distribution and overstress. Apart from the technical challenges, the price of SiC modules is another roadblock for its widespread application. The paralleling of a large number of SiC chips in the module to handle high current increases the module cost. Hence, this work proposes a Si-IGBT and SiC-MOSFET-based hybrid switch solution. For a converter-level packaging, the device technology, available device package, and orientation of the pins are the essential governing factors. This work addresses the converter-level packaging, which is referred to as a power electronics building block, of the proposed hybrid switch, combining discrete packages and frame-based modules for the devices and a singlephase three-level T-type topology. The primary optimization objective for converter-level packaging includes low inductance busbar design, high eciency, and high specic and volumetric power density. Overall implementation is not trivial; however, this work achieves an optimum design compared to the state-of-the-art. The module-level packaging challenges are dependent on the type of device technology and topology. Reducing the parasitic inductances, capacitances, and the junction to case thermal resistance are the optimization objectives in module packaging. Given the intended application of the module, achieving a high-reliability module is also essential. This work includes a hybrid switch-based power module addressing the challenges of WBG module-level packaging and challenges specic to the hybrid switch. The availability of engineering samples of SiC MOSFETs with voltage ratings above 10 kV and commercialization in the future drive the module-level packaging of high voltage devices. High voltage power modules will support the development of future solid-state circuit breakers, transformers, and power conversion applications in shipboards and rolling stocks. The availability of these modules can eliminate the necessity of multilevel topologies. This work investigates and demonstrates the module-level packaging of HV (10-15 kV) SiC MOSFETs