A Novel Magnetically Isolated High side DC Drive for 70V Thruster and its Application as Isolated Analog TM in High Voltage Spacecrafts

摘要

The Telecommand and Telemetry function provides the essential capability of remote control and monitoring of Satellite's subsystems once in orbit. The Telecommand signals should be isolated on board inside the subsystems. A non-isolated interface e.g. Relay driver involving a low level CMOS signal (5V) and Raw Bus (28-42V) may result in spurious operation of the indented function due to extraneous ground currents. Similarly Telemetry signal must be transferred across the isolation boundary to remove any ground loop induced noise. Historically isolation device use the optical or magnetic techniques. Opto-coupler is an effective and low cost isolation solution however they perform poor for analog signal isolation due to variation in its Current Transfer Ratio (CTR) under various operating conditions of voltage, temperature, etc. Also there is an expression of doubt about their life more than 15 years such as GEOSAT mission. On the other hand, magnetic isolation by the usage of transformer is a good solution for analog signal isolation, but their size increases for low frequency signal and their use becomes impossible for DC signal isolation such as analog telemetry monitoring. This paper presents a novel magnetic isolation technique for both telecommand and telemetry signal which makes transformer size independent of signal frequency and even transfer the DC signal such as analog telemetry across the isolation boundary with high accuracy and reliability. The method has been implemented and tested successfully. Test plots endorsing its accuracy and good signal linearity are also presented.