In the race to reduce emissions in aerospace systems, designers are increasingly moving towards more efficient electronics in control systems, including those that replace pneumatics and hydraulics–everything from onboard alternators to actuators and auxiliary power units.
Microchip Technology, working with European Commission consortium member Clean Sky, has developed a family of SiC-based power modules for aerospace applications intended to enable more efficient and compact power conversion and engine drive systems. The modules–designated BL1, BL2, and BL3–use a mix of 1200V silicon carbide (SiC) MOSFETs and 1600V diodes on a modified substrate designed for harsh aviation applications. The power modules are also available with Trench4Fast silicon IGBTs.
Mike Innab, Microchip’s senior manager for integrated power solutions, noted that size, weight, and cost are the key drivers in aerospace power converters. “Smaller size and lighter weight translate to long-term cost savings for aviation through more efficient flight. These along with the initial cost are critical in the very competitive aviation industry. The long-term reliability and robustness of the products are also critical,” Innab said in an interview.
The aviation sector seeks to replace the large, heavy and high-maintenance pneumatic and hydraulic systems with smaller, lower maintenance systems. “The electromechanical systems [have] a much lower overall operating cost than the pneumatic or hydraulic systems,” said Innab. Modern “aircraft now have a greater amount of power electronics on board, making the need for smaller, lighter and higher efficiency power systems even more of a necessity. SiC semiconductors enable that.”
To meet the emission limits set by European regulators for climate-neutral aviation by 2050, Microchip’s family aims to offer greater efficiency in AC-to-DC and DC-to-AC power conversion and generation through the integration of its silicon carbide power semiconductor technology.
SiC promises lighter weight components for lower energy consumption and reduced emissions. SiC also offers higher power density for a given voltage and current rating in a smaller, lighter device.
SiC chips exhibit higher switching speeds than conventional silicon, translating into greater power efficiency in a smaller package. That also translates into lower losses and less heat generated. Those physical characteristics are suited to power electronics applications in a smaller form factor, a key aviation requirement.
“The higher switching frequency and lower heat loss allow for much smaller and lighter power conversion systems by reducing the size of passives and reducing cooling needs,” Innab said. “The energy storage [capacitors] and magnetic components [transformers and inductors] used in power conversion systems are reduced in size and weight [at a scale] nearly proportional to the increase in switching frequency, so the higher achievable switching frequencies as a result of using SiC yield smaller lighter power conversion systems.”
Higher SiC switching speeds also reduce power dissipation by minimizing the cycle when current and voltage are transitioning between their extremes. The less time in this lossy state, the less overall power loss. That factor also helps reduce system cooling requirements.
“SiC is still new to the aviation industry, where ruggedness and the ability to predict long-term reliability is critical,” Innab added. “The aviation industry is typically slow to adopt new technologies as confidence in any particular new technology takes time to fully develop.”
Microchip claims its improved substrate that eliminates the need for a metal baseplate translates into a 40-percent reduction in weight over existing power electronics operating in the 100W to 10 kW range.
The BL1, BL2 and BL3 devices comply with mechanical and environmental guidelines set by the U.S. Federal Aviation Administration. The family incorporates silicon carbide MOSFETs and Schottky Barrier Diodes (SBDs), as well as IGBTs. They are available in low-profile, low-inductance form factors with connectors directly on PCBs to reduce development time and increase overall system reliability. The layout permits connections in parallel or in a three-phase bridge for more advanced power converters and inverters.
“SBDs are used to isolate high voltages, and SiC SBDs are more robust at the higher voltages than [silicon] because they are wide bandgap devices,” Innab noted.
The modules are available as 75A and 145A silicon carbide MOSFETs, 50A as IGBTs and 90A as rectifier diode outputs. The BL1, BL2, and BL3 modules come with several topology options, including phase leg, full bridge, asymmetric bridge, boost, buck and dual common source.
While the power electronics market still relies on standard silicon, new SiC designs are emerging as power demands grow. Silicon carbide offers dielectric strength as much as 10 times that of silicon, enabling devices operating at higher voltages and other requirements for target markets ranging from charging infrastructure, smart grids and, most recently, aviation.