Design and simulation of a smart optically controlled high-power switch based on a Si/SiC hybrid device structure

ABSTRACT In avionic systems, data integrity and high data rates are necessary for stable flight control. Unfortunately, conventional electronic control systems are susceptible to electromagnetic interference (EMI) that can reduce the clarity of flight control signals. Fly-by-Light systems that use optical signals to actuate the flight control surfaces of an aircraft have been suggested as a solution to the EMI problem in avionic systems. Fly-by-Light in avionic systems reduces electromagnetic interference hence improving the clarity of the control signals. A hybrid approach combining a silicon photoreceiver module with a SiC power transistor is proposed. The resulting device uses a 5mW optical control signal to produce a 150A current suitable for driving an electric motor . Keywords: Optically Controlled Switch, Silicon Carbide Devices, High Power Switching 1. INTRODUCTION Fiber optic component technology has been under development by the government and industry laboratories for over 20 years. The ever-increasing performance and economy of operation requirements placed on commercial and military transport aircraft are resulting in very complex systems. The often-cited benefits are high data throughput, immunity to EMI, reduced certification and maintenance costs and reduced weight features. These all motivate their application to flight control systems. Current Fly-by-Light systems are limited by the lack of optically activated high power switching devices. Due to there high breakdown voltages and ability to withstand high operating temperatures Silicon Carbide transistors have been suggested as ideal switching devices for high power applications. Unfortunately, SiC is not optically active at the near IR wavelengths where communications grade light sources are readily available. Thus, a hybrid approach is proposed that combines a silicon photoreceiver module with a SiC power transistor. The Silicon Chip consists of a photodetector, a receiver circuit and diagnostic circuits for real time evaluation of the control system operation. An analysis of the silicon chip design indicates that less than 5mW of optical signal is required to activate the silicon chip. When illuminated with the 5mW optical control signal the silicon chip produces a 15mA current that is used to drive a SiC Darlington pair. With a 15mA input current, the SiC chip will produce a 150 A current suitable for driving an electric motor with sufficient horsepower to actuate the control surfaces on an aircraft. In this paper we will report on our recent efforts towards demonstration of this hybrid Si-SiC module.