In the past, the NASA Lewis Research Center developed numerous types of direct-current to direct-current (dc/dc) converters with modest outputs (up to 100 watts (W) at 50 volts (V)) for operation over a wide range of temperatures from room temperature to -196 °C (the temperature of liquid nitrogen). For spacecraft that will operate in the cold temperatures of deep space, converters that can operate at low temperatures will require little or no heating (or the associated heating equipment). Consequently, they enable greater design versatility and lower cost. In addition, dc/dc converters can be operated more efficiently at low temperatures than at room temperature.
Recently, Lewis developed and demonstrated a high-voltage, 1-kW dc/dc converter that operates from room temperature to -184 °C. A power supply designed for use in a NASA ion beam propulsion system was utilized as a starting point for the design of a low- (wide-) temperature dc/dc converter. For safety, we decided to halve the output voltage and power level, so the converter was designed for an 80-Vdc input and a 550-Vdc output at 1 kW.
The components used in the circuit design were selected from component classes that had been screened and tested for low-temperature operation. Certain N-channel MOSFET's were chosen as switches because they function well at low temperatures and, when they are turned on at -196 °C, have only one-third to one-fourth of their room temperature losses. This graph for the new dc/dc converter shows (for three different operating conditions) that system efficiency increases gradually as temperature decreases from room temperature to -184 °C.
The Low Temperature Electronics Program is an ongoing program at Lewis in support of missions and development programs at NASA's Jet Propulsion Laboratory and Goddard Space Flight Center, in aerospace industry, and in medical electronics.
Lewis contact: Richard L. Patterson, (216) 433-8166,
Richard.L.Patterson@grc.nasa.gov
Author: Richard L. Patterson
Headquarters program office: OSS
Programs/Projects: ATMS, X2000 (JPL), Next Generation Space
Telescope (Goddard), Low Temperature Electronics
Previous articleLast updated April 15, 1998, by Nancy.L.Obryan@nasa.gov
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