Application of SiC Devices in Aviation Secondary Power Supply
Introduction
During flight and ground operations, aircraft are exposed to rapidly changing environmental conditions, which make the working environment for aviation electrical equipment significantly more complex than that of ground-based industrial systems. As a result, the requirements for the aircraft power system are extremely high, demanding exceptional performance, reliability, and efficiency.
The secondary power supply is a crucial component in the aircraft power system, encompassing devices such as static converters, transformer rectifiers, DC-DC converters, and motor drivers. These components must operate under harsh conditions, with strict demands on performance, reliability, size, weight, and energy consumption. Traditionally, silicon (Si)-based power electronic devices have been used in these applications. However, after decades of development, Si devices are approaching their theoretical performance limits, making further improvements increasingly difficult. This has become a major obstacle in advancing aviation secondary power systems.
In recent years, wide bandgap semiconductor materials like silicon carbide (SiC) have shown great potential. SiC power devices offer superior thermal stability, radiation resistance, high breakdown voltage, and high-frequency operation, making them ideal for extreme environments. Compared to traditional Si devices, SiC devices can significantly reduce power losses, allowing for smaller, lighter, and more reliable power electronics. Their advantages make them highly promising for future aviation power systems.
2. Advantages and Development of SiC Devices
As one of the most promising third-generation semiconductors, SiC has gained widespread attention due to its excellent properties. Table 1 compares key electrical characteristics of SiC and Si materials, highlighting the significant advantages of SiC in various aspects.
From Table 1, it is clear that SiC offers several key benefits:
1. Wide Bandgap: SiC has a much larger bandgap than Si, enabling higher operating temperatures. This makes SiC suitable for high-temperature applications such as aerospace, nuclear, and geothermal systems.
2. High Breakdown Electric Field: The breakdown electric field of SiC is about ten times higher than that of Si, allowing for higher voltage ratings and improved performance in power conversion systems.
3. Low On-Resistance: Due to its high breakdown field, SiC devices have much lower specific on-resistance, leading to reduced conduction losses and increased system efficiency.
4. High Thermal Conductivity: SiC conducts heat three times better than Si, reducing the need for cooling systems and improving overall system integration and reliability.
5. High Electron Saturation Velocity: SiC supports faster switching speeds and higher current densities, making it ideal for high-frequency and high-power applications.
Currently, countries such as the US, Europe, and Japan are leading in SiC crystal production, with companies like Cree, Infineon, and others actively developing SiC technology. Despite challenges in cost and reliability, the market for SiC power devices is growing rapidly, with expectations of reaching $8 billion by 2019.
In China, research on SiC power devices is still in its early stages, with several universities and institutions conducting studies. Companies like Tianke Heda are also playing a role in reducing the cost of SiC substrates, promoting broader adoption of the technology.
3. Application Analysis of SiC Devices in Aviation Secondary Power Supply
Based on the unique advantages of SiC devices, they are being increasingly applied in various aviation power systems. Below are some key applications:
3.1 Application in Aeronautical Static Inverters
Aeronautical static inverters (ASIs) convert DC power into AC power for aircraft systems. Traditional Si devices face limitations in efficiency and size, but SiC devices offer significant improvements. For example, using SiC MOSFETs can reduce conduction losses and improve efficiency at higher switching frequencies.
3.2 Application in Transformer Rectifiers
Transformer rectifiers are essential for converting AC to DC in aircraft power systems. SiC Schottky diodes are particularly beneficial here, as they eliminate reverse recovery losses and improve system efficiency, especially in high-temperature environments.
3.3 Application in DC-DC Converters
DC-DC converters are widely used in aircraft power supplies. SiC devices enable higher efficiency and smaller form factors, making them ideal for applications requiring both high and low voltage outputs.
3.4 Application in Motor Drivers
Motor drivers in aviation systems require high reliability and efficiency. SiC devices help reduce power dissipation and improve system performance, especially in high-current and high-temperature conditions.
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