Design of a Main-Bus Switching Regulator with Low RF Interference for the Radio Astronomy Explorer Satellite

This paper describes a variable ratio dc transformer regulator used in a voltage boost configuration to process the main vehicle power from a solar array battery power system in the Radio Astronomy Explorer (RAE) spacecraft. The selection of the design approach for the switching regulator is presented, together with an analysis of its operation and definition of its characteristics, functional performance, and test results. The regulator transforms a variable voltage input to a constant average voltage by constant-frequency pulse width modulation. Two major advantages are high efficiency and essentially constant thermal dissipation over a wide range of input power. The boost configuration employs a power transformer and transistor switches to handle only boost power. This method significantly reduces the RF interference generated in switching as compared to other series-switching regulation techniques, for voltage step-up, or step-down. The RF interference (RFI) inherent in the use of a switching regulator presented a major problem. The circuit elements, mode of regulation, and packaging arrangement were all developed to minimize RFI with the least sacrifice of performance.