SBIR-STTR Award

Optiswitch Technology Corporation (OTC) proposes to investigate and demonstrate a cost effective approach for optically controlled Fly-By-Light (FBL) power switches for severe environments. Silicon carbide (SiC) devices are expected to show superior performance over Silicon and Gallium Arsenide (GaAs) devices for FBL applications which fall in the 600-1000Volt, 10-100Amp range due to superior electrical and thermal properties. Direct optical activation requires UV light for exciting electrons from the valence to conduction band in 4H-SiC (3.26eV bandgap). High power UV light is currently expensive to generate and difficult to transport. OTC is proposing the use of light activated high temperature Silicon-on-Insulator (SOI) or GaAs switches to both turn-on and turn-off a SiC thyristor, GTO, BJT, MOSFET, or VJFET. Since both Silicon and GaAs have a lower bandgap than SiC, the forward voltage drop is less, making devices based on these materials very effective for shorting one or both of the emitting junctions to turn off the SiC GTO or as simple control gates for other SiC devices. With the lower bandgap, low cost laser diodes and delivery optics are available.. Commercially available SOI and GaAs devices operate at up to 300degC. OTC will be designing switches that can extend this range from 350degC to 400degC all activated by a low cost laser diode

OptiSwitch Technology Corporation is proposing to develop a high temperature (200-250 degC) all-optical gate drive for SiC power semiconductor devices. The optical control makes it less susceptible to EMI and allows isolation between the control and power circuits. The system will be composed two fiber coupled laser diodes driven by two compact (1.5”x 0.35”) laser diode drivers. Each optical fiber is then coupled to a pair of silicon-on-insulator (SOI) based photodetectors which act as current sources for on and off gate control. Since silicon is the material being activated, the system uses standard low cost laser diodes. The system is compact and efficient lending itself to fly-by-light applications which require high PRFs (20 kHz). In fact this gate driver topology is very universal and can be used to drive most (if not all) power semiconductor devices, making this driver a commercially viable product.

Keywords:
Fly-By-Light, Soi, Light Activated Switches, Laser Diodes, Gate Drive, Fbl, Sic