Silicon has traditionally been the preferred technology for power electronics designers in various traction applications, primarily utilizing IGBTs due to their superior qualities of performance, cost, and reliability in motor drive power electronics. These advanced devices allow for the potential use of more compact packages, faster switching speeds, inherently lower losses, and increased tolerance for high temperatures compared to conventional Silicon-based technology.

The swift evolution within the wide band gap power semiconductor field has sparked a surge in the potential applications of WBG devices across various sectors. These applications comprise automotive, aerospace, traction, grid-related activities, and charging systems. There is a promising prospect of WBG devices bringing about revolutionary changes in performance and efficiency, surpassing the capabilities of currently employed Silicon devices. Nevertheless, amid these thrilling advancements, numerous challenges persist, demanding efforts from both researchers and industries to address them.

For example, electric vehicles are the future of transportation which demands high-temperature operation with high power density which cannot be fulfilled by traditional Silicon as it has reached its plateau of growth. Although this issue is resolved by integrating wide bandgap devices like Galium Nitride and Silicon Carbide which are able to tolerate high currents and voltage, better fabrication processes and research is required.

On the other hand, the aircraft industry has constantly focused its attention towards the More Electric Aircraft that specializes in the advancement of manufacture and design of electric systems with a drive to replace hydraulic and mechanical parts. This has revolutionised the aircraft industry to expand its power networks up to higher power requirements like electric pumps, wing ice prevention systems, fans fuel and water pumps, electric actuators and a ton of other sensors and safety systems. An overview of the state of the art More Electric Aircraft Power Network is shown in Figure 1 which encompasses the main aircraft engine providing the electric generator to an AC bus.

Figure 1: Highly Simplified More Electric Aircraft Power System with Various Loads and Sensors

Aircraft Power Electronic Subsystems and the Advantages of Wide Bandgap Power Devices

In a typical commercial aircraft, electric power units are required in almost all systems, as shown in Figure 1, where both DC and AC power distribution networks are present with power electronic converters transforming energy from the aircraft generator to both HVDC and DC. With the increasing demand for power in aircraft electric systems, there is an everlasting need for more efficient variable frequency generators as the traditional method of connecting prime movers to induction motors has its efficiency peaked at 80 percent. An in-depth analysis shows that Silicon Carbide when integrated into the aircraft power system in the form of starter-generators, the AC/DC rectification was achieved with increased efficiency and frequency. On the other hand, Rectifier units and Transformer Rectifier Units are essential in an aircraft electronic system as they increase reliability, and efficiency and lower harmonic effects at higher frequencies. The traditional approach of combining a simple rectifier and autotransformer to attain AC/DC rectification with acceptable current and ripple harmonics is outdated and inefficient as they extensively use filter components. In order to overcome this issue, a merger of SiC diodes and GaN switching devices has proved to be useful as these devices offer faster switching with higher efficiency even with the use of slower SiC diodes.

Although the aircraft power system has been stepped down to a lower voltage network, a comprehensive DC/DC conversion is needed for lower voltage rating equipment which can be diverse throughout the aircraft and may individually contribute to inrush and harmonic current.

Transitioning from More Electric Aircraft to All Electric Aircraft requires an increase in demand for dynamically controlling fuel cells or batteries. Advanced and highly reliable DC/DC converters, especially those utilizing wide-bandgap devices, will play a crucial role in this transition.

An in-depth understanding of the switching behavior becomes a criterion not only for maximizing converter efficiency but also for predicting dynamic switching waveforms and anticipating the electromagnetic compatibility effects associated with higher switching frequencies. Due to the minimal commutation time in wide band gap devices, there is a need for accurate methods to measure and compare these characteristics which can ultimately decide the overall efficiency and reliability of the electric system. Additionally, the ability of Silicon Carbide devices to withstand high-temperature operation is a critical factor, particularly valuable in aircraft applications.

Influence of Wide Bandgap Devices

Wide bandgap devices are gaining popularity in power electronics applications due to their outstanding thermal and electrical characteristics, making them suited for aircraft power electrical systems. However, it is crucial to design these devices appropriately, comparing and integrating them with their specific characteristics, moreover, a simple substitution of Silicon devices with their SiC or GaN counterparts is insufficient and requires careful consideration. SiC shares a structural resemblance with Si devices, facilitating a smoother transition in fabrication. One of the major issues in these devices is the production of wafers which is currently underdeveloped and inefficient.

Despite these challenges, SiC MOSFETs and Diodes are in production, providing power electronics designers with viable options for switching frequencies. While SiC wafers are relatively more expensive, their costs are justified over Silicon due to their excellent thermal conductivity which facilitates effective heat dissipation, making it an excellent choice for the development of next-generation power electronic modules and systems. Among wide band gap materials, SiC devices can handle higher voltages routinely of up to 1200V, surpassing GaN, which lags in the high voltage sector.

Nevertheless, GaN holds significant potential in highly efficient, high-speed converters, especially for lower-voltage consumer applications. This is particularly evident in LED lighting, where the limiting factors for cost and reliability often arise from the power converter, which may become excessively hot, inefficient, bulky, and exhibit poor thermal performance, rather than the LED itself. In essence, the future of Wide bandgap devices in aircraft electronic and power systems is bright as industries look forward towards better packaging methods and keeping harmonics and parasites within the circuit in check.