Coaxial Beam Rotating Antenna (COBRA) Development and Technology Demonstrations

Virginia Power Technologies (VPT) purposes a high-efficiency, low voltage, spacecraft power converter using Gallium Arsenide (GaAs) synchronous rectifiers. High efficiency at low output voltages cannot be achieved with Schottky rectifiers because of their fixed voltage drop. Use of synchronous rectifiers can improve the efficiency. However, there is a limited availability of radiation-hardened synchronous rectifiers. Because these are all based on a silicon MOSFET structure they have poor high temperature performance, radiation degradation, high input capacitance, and reverse recovery losses due to their internal body diode. Under worst case, end-of-life conditions, their performance is a little better than Schottky diodes. A new GaAs synchronous rectifier has inherent radiation and temperature advantages over MOS devices. Also because it has a JFET structure, there is no internal body diode with its associated losses. VPT proposes to incorporate GaAs synchronous rectifiers into a radiation tolerant, active clamp, PWM soft-switching converter. It is shown to have significant advantages over a conventional current-fed push pull (CFPP) converter, widely used in spacecraft applications because of its radiation tolerance. The soft-switching circuit, coupled with GaAs devices, is capable of high efficiency at high frequency operation and is ideally suited in space applications. Benefits: The technology is of direct interest to both government and commercial satellites.