Richard L. Patterson

Performance of a spacecraft DC-DC converter breadboard modified for low temperature operation

A 10 W 30 V/5.0 V push-pull DC-DC power converter breadboard, designed by the Jet Propulsion Laboratory (JPL) with a +50/spl deg/C to +5/spl deg/C operating range for the Cassini space probe, was characterized for lower operating temperatures. The breadboard power converter which failed to operate for temperatures below -125/spl deg/C was then modified to operate at temperatures approaching that of liquid nitrogen (LN2). Associated with this low operating temperature range (>-196/spl deg/C) was a variety of performance problems such as a significant change in output voltage, power converter switching instability and failure to restart at temperatures below -154/spl deg/C. An investigation into these problems yielded additional modifications to the power converter which improved low temperature performance even further.

77 K operation of a multi-resonant power converter

The liquid-nitrogen temperature (77 K) operation of a 55 W, 200 kHz, 48/28 V zero-voltage switching multi-resonant DC/DC converter designed with commercially available components is reported. Upon dipping the complete converter (power and control circuits) into liquid-nitrogen, the converter performance improved as compared to the room-temperature operation. The switching frequency, resonant frequency, and the characteristic impedance did not change significantly. Accordingly, the zero-voltage switching was maintained from no-load to full-load for the specified line variations. Cryo-electronics can provide high density power converters, especially for high power applications.<<ETX>>

Low temperature performance of a full-bridge DC-DC converter

The low temperature (25/spl deg/C to -175/spl deg/C) performance of a 120 W, 100 kHz, 42/12 V phase-shifted zero-voltage-switched full-bridge DC-DC power converter designed with commercially available components is reported. Its efficiency increased from 80.8% at 25/spl deg/C to 81.8% at -175/spl deg/C. The power MOSFET and filter inductor loss decreased whereas the diode rectifier loss increased with decreasing temperatures. Low temperature operation of the open-loop control circuit based on CMOS and BiCMOS ICs is also discussed. The switching frequency of the converter increased with decreasing temperatures with maximum deviation of less than 4% compared to the room temperature operation. The converter successfully restarted at low temperatures without any visible degradation.

Wide temperature operation of a PWM DC-DC convertor

Wide temperature electronics is of great interest for space exploration programs. In this study, the wide temperature (-185/spl deg/C to 200/spl deg/C) operation of a 150 W, 50 kHz, 24/48 V pulse-width modulated (PWM) boost DC-DC power converter is reported. The power MOSFET, the power rectifier and the input inductor were placed inside a temperature chamber, whereas the rest of the power and control circuitry as well as all measuring instruments were at room temperature. The power converter efficiency varied between 92.2% and 89.4% in the entire temperature range. The power MOSFET loss decreased with decreasing temperatures. For the diode rectifier, loss increased with decreasing as well as increasing temperatures compared to room temperature operation. The inductor loss also increased due to increasing as well as decreasing temperatures compared to room temperature operation. Overall, the power converter operated successfully in a wide temperature range designed with commercially available components. Wide temperature operation of power capacitors and control circuitry, and the relevant reliability issues for passive and active components are to be addressed for design and operation of wide temperature electronic systems.

Electronic components and systems for cryogenic space applications

Electronic components and systems capable of operation at cryogenic temperatures are anticipated in many future NASA space missions such as deep space probes and planetary surface exploration. For example, an unheated interplanetary probe launched to explore the rings of Saturn would reach an average temperature near Saturn of about −183u200a°C. In addition to surviving the deep space harsh environment, electronics capable of low temperature operation would contribute to improving circuit performance, increasing system efficiency, and reducing payload development and launch costs. Terrestrial applications where components and systems must operate in low temperature environments include cryogenic instrumentation, superconducting magnetic energy storage, magnetic levitation transportation systems, and arctic exploration. An on-going R&D program at the NASA Glenn Research Center focuses on the development of reliable electronic devices and efficient power systems capable of surviving and operating in low tempera...

Preliminary evaluation of polyarylate dielectric films for cryogenic applications

Polymeric materials are used extensively on spacecraft and satellites in electrical power and distribution systems, as thermal blankets and optical surface coatings, as well as mechanical support structures. The reliability of these systems when exposed to the harsh environment of space is very critical to the success of the mission and the safety of the crew in manned-flight ventures. In this work, polyarylate films were evaluated for potential use as capacitor dielectrics and wiring insulation for cryogenic applications. Two grades of the film were characterized in terms of their electrical and mechanical properties before and after exposure to liquid nitrogen (−196 °C). The electrical characterization consisted of capacitance and dielectric loss measurements in the frequency range of 50 Hz to 100 kHz, and volume and surface resistivities. The mechanical measurements performed included changes in tensile Z(Youngs modulus, elongation-at-break, and tensile strength) and structural properties (dimensional change, weight, and surface morphology). The preliminary results, which indicate good stability of the polymer after exposure to liquid nitrogen, are presented and discussed.

Characterization of low power DC/DC converter modules at cryogenic temperatures

The operation of power electronic systems at cryogenic temperatures is anticipated in many NASA space missions such as planetary exploration and deep space probes. In addition to surviving the hostile space environments, electronics capable of low temperature operation would contribute to improving circuit performance, increasing system efficiency, and reducing development and launch costs. As part of the on-going Low Temperature Electronics Program at NASA Glenn Research Center (GRC), several commercial-off-the-shelf (COTS) DC/DC converters have been characterized in terms of their performance as a function of temperature in the range of 20/spl deg/C to -180/spl deg/C. These converters ranged in electrical power from 8 W to 13 W, input voltage from 9 V to 75 V and an output voltage of 3.3 V. The experimental set-up and procedures along with the results obtained on the converters steady-state and dynamic characteristics are presented and discussed.

Silicon-on-insulator (SOI) devices and mixed-signal circuits for extreme temperature applications

Electronic systems in planetary exploration missions and in aerospace applications are expected to encounter extreme temperatures and wide thermal swings in their operational environments. Electronics designed for such applications must, therefore, be able to withstand exposure to extreme temperatures and to perform properly for the duration of the missions. Electronic parts based on silicon-on-insulator (SOI) technology are known, based on device structure, to provide faster switching, consume less power, and offer better radiation-tolerance compared to their silicon counterparts. They also exhibit reduced current leakage and are often tailored for high temperature operation. However, little is known about their performance at low temperature. The performance of several SOI devices and mixed-signal circuits was determined under extreme temperatures, cold-restart, and thermal cycling. The investigations were carried out to establish a baseline on the functionality and to determine suitability of these devices for use in space exploration missions under extreme temperatures. The experimental results obtained on selected SOI devices are presented and discussed in this paper.

Wide Range Temperature Sensors for Harsh Environments

Silicon-on-insulator (SOI) parts are designed for high temperature applications and the potential exists about their performance at cryogenic temperature conditions. In this paper, the performance of SOI devices and circuits were evaluated under extreme temperatures and thermal cycling. Two oscillator circuits were constructed using a new SOI 555 timer chip and used as temperature sensors in harsh environments encompassing jet engines and space mission applications. The circuits, were evaluated between -190degC and +200degC. The output of each circuit produced a stream of square pulses whose frequency was a function of the sensed temperature. The results indicate that both circuits performed relatively well over the entire test temperature range. In addition, the performance of either circuit did not undergo any change after subjecting the circuits to limited thermal cycling over the temperature regime of -190degC and +200degC, and the circuits were able to cold start at -195degC.

Performance of Silicon Germanium Power Devices at Extreme Temperatures

In deep space missions, surface- and spacecraft are exposed to extreme low temperatures. For example, calculations indicate that temperatures of about 120 K (- 153degC) at the orbit of Jupiter and about 44 K (-229degC) at the orbit of Pluto. Even the moon, Mars, and asteroids can subject spacecraft to temperatures well below the conventional limit for electronic parts of -55degC. The utilization of electronics designed for and operated at low temperature is expected to increase efficiency and simplify thermal management of electronic systems. In this paper, the performance of engineering samples of silicon germanium (SiGe) power devices consisting of diodes and hetero-j unction bipolar transistors (HBT) were evaluated under low temperature and thermal cycling. The investigations were carried out to establish a baseline on the functionality and to determine suitability of such devices for use in space exploration missions under cryogenic temperatures. The power devices were evaluated in terms of their switching characteristics and DC current gain in the temperature range between -195degC and +85degC. The effects of thermal cycling and cold-restart capability were also investigated. All of the devices were able to maintain good operation between -195degC and +85degC. In addition, the limited thermal cycling had no effect on their switching performance or on their packaging, and they were able to cold start at -195degC.