Power conditioning requirements for ion thruster systems

A diverse set of specifications and requirements must be met by the power conditioning unit for an electric propulsion system. To meet these requirements, a typical unit contains power conversion, internal control loops, command subsystem for ground control, and telemetry. Power conversion circuitry must supply appropriate power to approximately 10 separate loads; there will be several feedback loops which monitor system operation and control the power conversion circuitry as required. The command subsystem for a typical first generation flight system provides for 12 ground command channels, while the telemetry subsystem provides monitoring and signal conditioning for 12 telemetry channels. To provide the required functions approximately 1200 discrete components would be required. Since a large fraction are devoted to logic and low level analog signal processing, the application of integrated circuits can be highly advantageous, and in fact, a trend toward their use can be identified. Early electric propulsion systems used discrete components exclusively, while the next generation (ca 1967) made extensive use of integrated circuit operational amplifiers and transistor logic building blocks. Requirements for special purpose integrated circuits for use in future systems will be discussed.