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Cryogenic Evaluation of an Advanced DC/DC
Converter Module for Deep Space Applications
DC/DC converters are widely used in power management, conditioning, and
control of space power systems. Deep space applications require
electronics that withstand cryogenic temperature and meet a stringent
radiation tolerance. In this work, the performance of an advanced,
radiation-hardened (rad-hard) commercial DC/DC converter module was
investigated at cryogenic temperatures. The converter was investigated
in terms of its steady state and dynamic operations.
The output voltage regulation, efficiency, terminal current ripple
characteristics,
and output voltage response to load changes were determined in the
temperature
range of 20°C to -140°C. These parameters were obtained at various load
levels
and at different input voltages. The experimental procedures along with
the
results obtained on the investigated converter are presented and
discussed.
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Performance of High-Frequency High-Flux
Magnetic Cores at Cryogenic Temperatures
Three magnetic powder cores and one ferrite core, which are commonly
used in inductor and transformer design for switch mode power supplies,
were
selected for investigation at cryogenic temperatures. The powder cores
are
Molypermalloy Core (MPC), High Flux Core (HFC), and Kool Mu Core (KMC).
The performance of four inductors utilizing these cores has been
evaluated
as a function of temperature from 20°C to –180°C. All cores were wound
with
the same wire type and gauge to obtain equal values of inductance at
room
temperature. Each inductor was evaluated in terms of its inductance,
quality
(Q) factor, resistance, and dynamic hysteresis characteristics (B-H
loop)
as a function of temperature and frequency. Both sinusoidal and square
wave
excitations were used in these investigations. Measured data obtained
on
the inductance showed that both the MPC and the HFC cores maintain a
constant
inductance value, whereas with the KMC and ferrite core hold a steady
value
in inductance with frequency but decrease as temperature is decreased.
All
cores exhibited dependency, with varying degrees, in their quality
factor
and resistance on test frequency and temperature. Except for the
ferrite,
all cores exhibited good stability in the investigated properties with
temperature
as well as frequency. Details of the experimental procedures and test
results
are presented and discussed in the paper.
Electronics for Cryogenic Deep Space
Applications
Deep space probes and planetary exploration missions require electrical
power management and control systems that are capable of efficient and
reliable operation in very cold temperature environments. Typically, in
deep space probes, heating elements are used to keep the spacecraft
electronics near room temperature. The utilization of power electronics
designed for and
operated at low temperature will contribute to increasing efficiency
and
improving reliability of space power systems. At NASA Glenn Research
Center,
commercial-off-the-shelf devices as well as developed components are
being
investigated for potential use at low temperatures. These devices
include
semiconductor switching devices, magnetics, and capacitors. Integrated
circuits
such as digital-to-analog and analog-to-digital converters, DC/DC
converters,
operational amplifiers, and oscillators are also being evaluated. In
this
paper, results will be presented for selected analog-to-digital
converters,
oscillators, DC/DC converters, and pulse width modulation (PWM)
controllers.
Ge-Based Semiconductor Devices for
Cryogenic
Power Electronics
NASA’s plans to explore remote bodies in the Solar System will subject
spacecraft and surface craft to environmental temperature extremes. For
example, calculations indicate about 120 K (–150°C) at the orbit of
Jupiter and about 44 K (–230°C) at the orbit of Pluto. Even the moon,
Mars, and asteroids can subject surface craft to temperatures well
below the conventional limit for electronic parts of –55/–65°C.
Incorporating thermal control into spacecraft and surface
craft
to maintain electronic systems within the conventional temperature
range
of –55°C to +125°C will become increasingly less desirable and less
practical. Elimination of thermal control would provide important
benefits including decreased mass, size, complexity and power
requirements. This would also
result in reduced development time-and-effort and launch costs, as well
as
extended mission operations for longer observation or exploration time.
Thus
there are strong reasons to allow the electronics and other systems to
assume
a temperature near that of the environment, in other words to operate
“cold.”
To address the need for “cold” electronics, we have been
investigating and developing semiconductor devices (diodes and
transistors) specifically for use in cryogenic power conversion and
conditioning circuitry as well
as for driver circuitry (for motors or actuators).
Because of the particular requirements of the NASA
applications, we are using germanium (Ge) in the development of these
semiconductor devices. Our investigations confirm that Ge devices,
including diodes, junction field-effect transistors, and bipolar
transistors, can operate over the entire cryogenic temperature range of
interest (down to about 20-30 K). We are also proposing to develop
cryogenic devices based on the silicon-germanium (SiGe) semiconductor
materials system because of its compatibility with existing Si device
fabrication and its greater design flexibility afforded by band-gap
engineering.
Evaluation of Power Electronic Components
and Systems at Cryogenic Temperatures
Power electronic circuits and systems designed for deep space
applications and outer planetary exploration are required to operate
reliably and efficiently under extreme temperature conditions. This
requirement is dictated by the fact that the operational environments
associated with some of the space
missions would encompass temperatures as low as –183°C. The development
and utilization of electronics capable of low temperature operation
would not
only fulfill the advanced technology requirements, but also would
contribute
to improving circuit performance, increasing system efficiency, and
reducing development and launch costs. These benefits are generally
achieved by the improved intrinsic properties of some of the electronic
materials at low
temperature, reduced device losses, and the elimination of heating
elements
used in conventional systems at low temperatures. Power electronic
circuits
are widely used in space power systems in the areas of power
management,
conditioning, and control. In this work, the performance of certain
power
electronic components and systems was investigated under low
temperature. These include inductors, capacitors,
pulse-width-modulation (PWM) controllers,
and advanced commercial DC/DC converter modules. Different properties
were
determined as a function of temperature in the range of 20°C to -
140°C,
at various current and voltages levels. The experimental procedures
along
with the experimental data obtained are presented and discussed in this
paper.
Low Temperature Reliability of Electronic
Packages/Assemblies for Space Missions
A NASA-wide team, funded under the NASA Electronic Parts and Packaging
Program (NEPP), was formed to collaborate and to establish reliability
of various electronic parts/packaging and assemblies for operation
under extreme cold temperatures. One of the primary objectives of the
NEPP is to expedite the infusion of cutting edge technologies into the
present and future NASA missions. Commercial-off-the-shelf (COTS)
emerging electronic parts/packages due to their lower weight, increased
functionality, and lower cost are excellent candidates for space
missions if they are characterized to show that they will meet the
stringent reliability and quality requirements. Characterizations,
especially for the extreme cold temperatures, are required since very
limited data are available by manufacturers or users. For severe
military environments, the temperature conditions to –65°C are the
lowest temperature for which these parts/packages and assemblies are
qualified. New data beyond this relatively benign cold temperature are
required for numerous NASA missions. Several
parts/packages, based on the project recommendation for their immediate
and
future needs, were selected for detailed characterization to cold
temperature
regimes down to liquid nitrogen (-196°C), covering both Mars cold
temperature
(-125°C) and asteroid (-180°C) lander environmental requirements.
Numerous parts/packages and assemblies were characterized
during extreme temperature environmental tests. Several electrical
parameters were characterized at discrete temperatures to –185°C to
determine if they remain within their specification ranges. Both
packages and circuit boards were subjected to nondestructive testing
including optical, X-ray, and acoustic microcopy to document their
integrity prior to environment exposure. Package/board assemblies were
also subjected to X-ray to characterize solder joint integrity
including void levels. Both parts and assemblies were subjected to
thermal cycling with a large temperature swing enveloping numerous NASA
missions. Details of the performed tests and the results obtained are
presented.
Performance of High Speed Pulse Width
Modulation Control Chips 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 space hostile
environment, 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
NASA Glenn Low Temperature Electronics Program, several commercial
high-speed Pulse Width Modulation (PWM) chips have been characterized
in terms of their performance as a function of temperature in
the range of 25 to -196°C (liquid nitrogen). These chips ranged in
their electrical
characteristics, modes of control, packaging options, and applications.
The
experiment procedures along with the experimental data obtained on the
investigated
chips are presented and discussed.
Performance of Power Converters at
Cryogenic
Temperatures
Power converters capable of operation at cryogenic temperatures are
anticipated to play an important role in the power system architecture
of future NASA deep space missions. Design of such converters to
survive cryogenic temperatures will improve the power system
performance, and reduce development and launch costs.
Aerospace power systems are mainly a DC distribution network.
Therefore, DC/DC and DC/AC converters provide the outputs needed to
different loads
at various power levels. Recently, research efforts have been performed
at
the NASA Glenn Research Center (GRC) to design and evaluate DC/DC
converters
that are capable of operating at cryogenic temperatures.
This paper presents a summary of the research performed to
evaluate the low temperature performance of five DC/DC converters.
Various parameters were investigated as a function of temperature in
the range of 20°C to –196°C. Data pertaining to the output voltage
regulation and efficiency of the
converters is presented and discussed.
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 -183°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 instrumentations, superconducting magnetic energy storage,
magnetic levitation transportation system, 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 in
low
temperature environments. An overview of the program will be presented
in
the paper. A description of the low temperature test facilities along
wit
selected data obtained from in-house component testing will also be
discussed.
Ongoing research activities that are being performed in collaboration
with
various organizations will also be presented.
Low Temperature Testing of a Radiation
Hardened CMOS 8-Bit Flash Analog-to-Digital (A/D) Converter
Power processing electronic systems, data acquiring probes, and signal
conditioning circuits are required to operate reliably under harsh
environments in many of NASA’s missions. The environment of the space
mission as well as
the operational requirements of some of the electronic systems, such as
infrared-based
satellite of telescopic observation stations where cryogenics are
involved,
dictate the utilization of electronics that can operate efficiently and
reliably
at low temperatures. In this work, radiation-hard CMOS 8-bit flash A/D
converters
were characterized in terms of voltage conversion and offset in the
temperature
range of +25 to –190°C. Static and dynamic supply currents, ladder
resistance,
and gain and offset errors were also obtained in the temperature range
of
+125 to –190°C. The effect of thermal cycling on these properties for a
total
of ten cycles between +80 and -150°C was also determined. The
experimental
procedure along with the data obtained are reported and discussed in
the
paper.
Low Temperature Performance of High Power
Density DC/DC Converter Modules
In this paper, two second-generation high power density DC/DC converter
modules have been evaluated at low operating temperatures. The power
rating of one converter (Module 1) was specified at 150 W with an input
voltage
range of 36-75 V and output voltage of 12 V. The other converter
(Module
2) was specified at 100 W with the same input voltage range and an
output
voltage of 3.3 V. The converter modules were evaluated in terms of
their
performance as a function of operating temperature in the range of 25°C
to
-140°C. The experimental procedures along with the experimental data
obtained
are presented and discussed in this paper.
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 space hostile
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°C to
-180°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.
Efficiency and Regulation of Low Power
DC/DC
Converter Modules of Cryogenic Temperatures
DC/DC converters that are capable of operating at cryogenic
temperatures are anticipated to play an important role in the power
systems of future
NASA deep space missions. Design of these converters to survive
cryogenic temperatures will improve the power system performance, and
reduce development and launch costs.
At the NASA Glenn Research Center Low Temperature Electronics
Laboratory, several commercial off-the-shelf DC/DC converter modules
were evaluated for their low temperature performance. Various
parameters were investigated as
a function of temperature, in the range of 20°C to –180°C. Data
pertaining to the efficiency and voltage regulation of the tested
converters is presented and discussed.
Development of Electronics for Low
Temperature Space Missions
Electronic systems that are capable of operating at cryogenic
temperatures will be needed for many future NASA space missions,
including deep space
probes and spacecraft for planetary surface exploration. In addition to
being
able to survive the harsh deep space environment, low-temperature
electronics
would help improve circuit performance, increase system efficiency, and
reduce
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 ongoing research and
development project for the design, fabrication, and characterization
of
low-temperature electronics and supporting technologies at NASA Glenn
Research
Center focuses on efficient power systems capable of surviving in and
exploiting
the advantages of low-temperature environments. Supporting technologies
include
dielectric and insulating materials, semiconductor devices, passive
power
components, optoelectronic devices, and packaging and integration of
the
developed components into prototype flight hardware. An overview of the
project
is presented, including a description of the test facilities, a
discussion
of selected data from component testing and a presentation of ongoing
research
activities being performed in collaboration with various organizations.
Performance Evaluation 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 space hostile
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°C to -
180°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.
Characterization of Semiconductor Devices
at Cryogenic Temperatures
Many deep space probes and some terrestrial systems would benefit from
the operation of the electronics at cryogenic temperatures, however, at
the present time, the electronics have been constrained to operate at
or near room temperature. If the electronics were able to operate at
cryogenic temperatures, it would significantly reduce thermal and
system constraints. Highly efficient hybrid electronics could be built
using optimized semiconductor devices and
superconductors providing the electronics were constrained to operate
at
cryogenic temperatures only. Previous studies have shown that
commercial silicon bipolar and MOSFET devices continue to operate down
to near liquid nitrogen temperatures but suffer significant performance
degradation. GaAs devices operated at even lower temperatures. However,
due to the low voltage and current capability of commercial GaAs
devices, these devices are predominately used at frequencies where
silicon devices cannot operate. Commercial Ge, Si, and GaAs devices
were characterized at low temperatures. In addition, selected power
devices were subjected to repeat quenches from room temperature to
liquid nitrogen until failure. Selected data from the device testing
will
be discussed. Ongoing semiconductor device research activities that are
being
performed in collaboration with various organizations will also be
presented.
DC-DC Converters at Cryogenic Temperatures
At the NASA Glenn Research Center on-going research is being conducted
in the area of low temperature electronics. This work is being
performed primarily for application to future NASA deep space missions.
As an example, an unheated interplanetary probe launched to explore the
rings of Saturn would experience an average temperature near Saturn of
about -183ºC. Typically, in deep space
probes, RHUs (Radioisotope Heating Units) are needed to keep the
spacecraft
electronics at room temperature. However, there are advantages to
operating
the electronics at the cryogenic temperatures of deep space. They
include
reducing or eliminating thermal system requirements such as thermal
shutters
and the need for RHUs, which can create overheating at launch time. Low
temperature
electronics has other applications including high power generators,
converters
and motor drives, cryogenic instrumentation, medical diagnostics, and
super-conducting
magnetic energy storage. As part of the NASA Glenn Low Temperature
Electronics
Program a variety of dc-dc converter circuits have been designed and
evaluated
for low temperature operation. Topologies included are a buck, boost,
multi-resonant,
push-pull, and full-bridge configurations. These converter ranged in
electrical
output power from 10W to 175W and with voltages ranging from 5V to 48V.
In
some cases open-loop control was utilized and in others closed-loop
control was investigated. The push-pull circuit was a JPL breadboard
dc-dc converter designed for +5ºC to +50ºC operation for the Cassini
Interplanetary Probe.
The circuit was evaluated at NASA Glenn to determine its lowest
operating
temperature. The circuit was then modified to extend its operate range
down
to -196ºC. A high voltage (80V/500V), high power (1000W), full-bridge
dc-dc
converter was also designed and tested. This work was based on a
converter
topology designed for NASA Solar Electric Propulsion Technology
Application
Readiness (NSTAR) Program. A synopsis of the various topologies
investigated
and their test results are presented and discussed in this paper.
Passive Component Characterization at Low
Temperature
Many space and some terrestrial applications would benefit from
availability of low temperature electronics. Exploration missions to
the outer planets, earth-orbiting and deep-space probes, and
communications satellites are
examples of space applications where low temperature is encountered.
Terrestrial
applications where components and systems must operate in low
temperature
environments include cryogenic instrumentation, super-conducting
magnetic
energy storage, and arctic fields. Most modern electronic components
are
limited to low operating temperature of -40ºC to -55ºC. The Low
Temperature
Electronics Program at NASA Glenn Research Center focuses on the
development
and characterization of low temperature components and integration of
the
developed devices into demonstrable low temperature power systems such
as
DC/DC converters. NASA Glenn researchers are now performing extensive
evaluations
of commercially available as well as custom-made devices. These include
various types of energy storage and signal capacitors, power switching
devices,
magnetic and super-conducting materials, and primary lithium batteries
to
name a few. The components are subjected to screening and then to
comprehensive
characterization as a function of parameters such as frequency, applied
bias,
temperature, and multi-stress conditions. A description of some of the
devices
investigated and the results obtained will be presented and discussed
in
this paper.
The Low Temperature Electronics Program at
NASA Lewis (now Glenn) Research Center
In many future NASA missions, such as deep space planetary exploration
and Next Generation Space Telescope, electrical components and systems
must operate reliably and efficiently in very low temperature
environments. If radioisotope heating units are eliminated, new low
temperature electronics not only will tolerate hostile environments but
also will reduce system size,
weight, complexity, and launch cost, while improving reliability and
lifetime
and increasing energy density and efficiency. Low temperature
electronic components
will be beneficial for terrestrial applications such as medical
instrumentation, magnetic levitation transport systems, electrical
power loading leveling,
and arctic and antarctic exploration and science. The Low Temperature
Electronics Program at NASA Lewis Research Center focuses on the
design, fabrication,
and characterization of low temperature electrical systems and the
development
of supporting technologies for low temperature operations. These
efforts
include research and development of semiconductor and passive devices,
components, dielectric materials, and energy generation storage. An
overview of the
program will be presented in this paper, including a description of
test
facilities. Selected data from component testing will be discussed.
Ongoing
research activities that are being performed in collaboration with
various
organizations will also be presented.
Performance of a Closed-Loop-Controlled
High Voltage DC-DC Converter at Cryogenic Temperatures
A 1 kW, 80-110V/500V closed-loop-controlled full-bridge dc-dc converter
was designed to operate from room temperature to -190ºC using
commercially available components. The converter design was based on
that of a beam supply for a space electric propulsion system, with the
added capability of being able to operate over a very wide low
temperature range. In order to design a circuit to operate at cryogenic
temperatures, specific attention was paid to the selection of the
components used. In particular, most bipolar-type devices were avoided
and were replaced with CMOS-type devices which have been shown to work
well at low temperatures. Finally, only certain types of
resistors, capacitors, and magnetics (which were known to have
desirable characteristics
at low temperature) were selected. The closed-loop-controlled
full-bridge
dc-dc converter was tested and operated successfully from room
temperature
to -190ºC. The performance of the closed-loop control was verified by
measuring
the efficiency, output regulation and switching behavior over changing
load,
and input voltage at various operating temperature conditions.
Performance of Surface-Mount Ceramic and
Solid Tantalum Capacitors for Cryogenic Applications
Low temperature electronics are of great interest for space exploration
programs. These include missions to the outer planets, earth-orbiting
and deep-space probes, remote-sensing and communication satellites.
Terrestrial applications would also benefit from the availability of
low temperature
electronics. Power components capable of low temperature operation
would,
thus, enhance the technologies needed for the development of advanced
power
systems suitable for use in harsh environments. In this work, ceramic
and
solid tantalum capacitors were evaluated in terms of their dielectric
properties
as a function of temperature and at various frequencies. The
surface-mount
devices were characterized in terms of their capacitance stability and
dissipation factor in the frequency range of 50 Hz to 100 kHz at
temperatures ranging from room temperature (20ºC) to about liquid
nitrogen temperature (-190ºC).
The results are discussed and conclusions made concerning the
suitability
of the capacitors investigated for low temperature applications.
Evaluation of Capacitors at Cryogenic
Temperatures for Space Applications
Advanced electronic systems designed for use in planetary exploration
missions must operate efficiently in the extreme low temperatures of
deep
space environment. In addition, spacecraft power electronics capable of
low temperature operation will greatly simplify the thermal management
system
by eliminating the need for heating units and associated equipment and
thereby
reduce the size and weight of the overall system. In this study, film,
mica,
solid tantalum and electric double layer capacitors were evaluated as a
function of temperature in terms of their dielectric loss in the
frequency
range of 50 Hz to 100 kHz. DC leakage current measurements were also
performed
on the capacitors. The results obtained are discussed and conclusions
are
made concerning the suitability of the capacitors investigated for low
temperature
applications.
Low Temperature Power Electronics Program
Many space and some terrestrial applications would benefit from the
availability of low temperature electronics. Exploration missions to
the outer planets, Earth-orbiting and deep-space probes, and
communications satellites are examples
of space applications which operate in low-temperature environments.
Space
probes deployed near Pluto must operate in temperatures as low as
-229ºC. Figure 1 depicts the average temperature of a space probe
warmed by the
sun for various locations throughout the solar system. Terrestrial
applications where components and systems must operate in low
temperature environments include cryogenic instrumentation, super
conducting magnetic energy storage, magnetic levitation transport
system, and arctic exploration. The development of electrical power
systems capable of extremely low-temperature operation represents a key
element of some advances space power systems. The Low Temperature Power
Electronics Program at NASA Glenn Research Center focuses on the
design, fabrication, and characterization of low-temperature power
systems and the development of supporting technologies for
low-temperature operations such as dielectric and insulating materials,
power components, optoelectronic
components, and packaging and integration of devices, components, and
systems.
Evaluation of Wiring Constructions for
Space Applications
A NASA Office of Safety and Mission Assurance (OS&MA) program to
develop lightweight, reliable, and safe wiring insulations for
aerospace applications is being performed by the NASA Glenn Research
Center (GRC). As part of this effort, a new wiring construction
utilizing high strength PTFE (Poly Tetrafluoroethylene) as the
insulation has been tested and compared with the existing military
standard polyimide-based MIL-W-81381 wire construction. Electrical
properties which were investigated included ac corona inception and
extinction voltages (sea level and 60,000 feet), time/current to smoke,
and wire fusing time. The two constructions were also characterized in
terms of their mechanical properties of flexural strength, abrasion
resistance (23ºC and 150ºC), and dynamic cut-through (23ºC and 200ºC).
The results obtained in this testing effort are presented and discussed
in this paper.
Investigation of Rechargeable Battery
Management Systems under Low Temperatures
The operation of space power electronics at low temperatures simplifies
the thermal management system by eliminating the need for the heating
units currently used and is expected to result in more efficient
systems. Such
improvements are a result of better electronic, electrical and thermal
properties
at low temperature. The Low Temperature Electronics Program at NASA
Glenn
Research Center has undertaken an effort to design and develop
lightweight,
reliable wide temperature power systems for space-based applications. A
number
of power semiconductor devices, power electronic converters, and
different types of capacitors, magnetic cores and batteries have been
tested to evaluate their capabilities/limitations at very low
temperatures (down to -196ºC). Such tests will allow constructing a
road map to assist in formulating requirements, developing low
temperature components and systems for space-based product development.
This paper presents the research performed on the low temperature
performance of rechargeable battery management technologies. Due to the
increased use of battery-powered equipment such as portable computers,
cellular
phones, and other electronic equipment, the market for batteries and
battery
chargers has increased considerably. The management of portable power
has
become equally important in operation, performance, and ultimately the
success
of a portable product. A typical battery management system monitors a
number
of battery variables such as voltage and its rate of change, state of
charge
and speed of recharge, absolute temperature and its rise above ambient,
remaining operation time and other safety issues that will optimize the
battery life and performance. Three battery chemistries are considered
in
the research. These are the nickel-cadmium (NiCd), nickel-metal hydride
(NiMH) and lithium-ion (Li-ion). The market for battery management
system
for these batteries has been searched and the study has focused on two
battery
management integrated circuit manufactures. These are Dallas
Semiconductor
and MAXIM Integrated Products. In particular, the DS2434, DS2435, and
DS2437
IC-chips from Dallas Superconductor and the MAX712, MAX846A, and
MAX2003A
IC-chips form MAXIM Integrated Products have been evaluated at
low-temperature.
The six chips were characterized in a chamber whose temperature is
changed
and regulated using liquid nitrogen. The temperature of the chamber has
been
varied from 20ºC to -180ºC. At each temperature the battery voltage,
current,
state of charge, temperature, and other auxiliary variables as
monitored by
each chip have been recorded. The result of this study reveals that the
existing
battery management technologies are probably capable of low temperature
operation.
Low Temperature Performance Evaluation of
Battery Management Technologies
This paper presents the results of research efforts performed to
evaluate the performance of rechargeable battery management
technologies at low temperatures. Three battery chemistries are
considered in this work. These are the Nickel-Cadmium (NiCd),
Nickel-Metal Hydride (NiMH), and Lithium-ion (Li-ion). Battery
management evaluation kits from two battery manufacturers were acquired
and tested.
These are the DS2434k, DS2435k, and DS2437k form Dallas Semiconductor
and
the MAX712, MAX846A, and MAX2003A from MAXIUM Integrated Products. The
kits
were characterized in a chamber whose temperature was changed and
regulated
using liquid nitrogen. The temperature of the chamber was varied from
20° C to -180° C. At each temperature, the battery voltage, current,
state of
charge, temperature, and other auxiliary variables as monitored by each
chip
were recorded. The results of this preliminary study show that the
existing battery management technologies, with minor design
modifications, could
be potentially used at low temperatures.
Performance of a Closed-Loop-Controlled
High Voltage DC-DC Converter at Cryogenic Temperatures
A 1 kW, 80-110V/500V closed-loop-controlled full-bridge dc-dc converter
was designed to operate from room temperature to -190° C using
commercially available components. The converter design was based on
that of a beam supply for a space electric propulsion system, with the
added capability of being able to operate over a very wide low
temperature range. In order to design a circuit to operate at cryogenic
temperatures, specific attention was paid to the selection of the
components used. In particular, most bipolar-type devices were avoided
and were replaced with CMOS-type devices which have
been shown to work well at cryogenic temperatures. In addition, MOSFET
switches were used because of their capability to operate quite well at
low temperatures. Finally, only certain types of resistors, capacitors
and magnetics (which were known to have desirable characteristics at
low temperature) were selected.
Performance of a Spacecraft DC-DC
Converter
at Cryogenic Temperatures
A 10W 30V/5.0V push-pull dc-dc converter breadboard, designed by the
Jet Propulsion Laboratory (JPL) with a +50° C to +5° C operating range
for the Cassini space probe, was characterized for lower operating
temperatures.
The breadboard converter which failed to operate for temperatures below
-125° C was then modified to operate at temperatures approaching that
of liquid nitrogen (LN2). Associated with this low operating
temperature range (-196° C) was a variety of performance problems such
as a significant change in output voltage, converter switching
instability and failure to restart at temperatures below -154° C. An
investigation into these problems yielded additional
modifications of the converter which improved low temperature
performance
even further.
Improved L-C Resonant Decay Technique for
Q
Measurement of Quasilinear Power Inductors: New Results for MPP and
Ferrite
Powdered Cores
The L-C resonant decay technique for measuring circuit Q or losses is
improved by eliminating the switch from he inductor-capacitor loop. A
MOSFET
switch is used instead to momentarily connect the resonant circuit to
an
exciting voltage source, which itself is gated off during the decay
transient.
Very reproducible, low duty cycle data could be taken this way over a
dynamic voltage range of at least 10:1. Circuit Q is computed from a
polynomial fit to the sequence of the decaying voltage maxima. This
method was applied to measure the losses at 60 kHz in inductors having
loose powder cores of moly permalloy (MPP) and a Mn-Zn power ferrite.
After the copper and capacitor losses are separated out, the resulting
specific core is shown to be roughly as expected for the MMP powder,
but anomalously high for the ferrite powder. Possible causes are
mentioned.
Low Temperature Performance of a
Full-Bridge DC-DC Converter
The low temperature (25° C to -175° C) performance of a 120 W, 100kHz,
42/12 V phase-shifted full-bridge dc-dc power converter designed with
commercially available components is reported. Its efficiency increased
from 80.8% at
25° C to 81.8% at -175° C. The power MOSFET and filter inductor loss
decreased whereas the diode rectifier loss increased with decreasing
temperatures.
Low temperature operation of the closed-loop control circuit based on
CMOS
and BiCMOS ICs is also discussed. The switching frequency of the
converter
increased with decreasing temperatures with a maximum deviation of less
than
4% compared to the room temperature operation. The converter
successfully
restarted at low temperatures without any visible degradation.
Low Temperature Characterization of
Ceramic
and Film Power Capacitors
Among the key requirements for advanced electronic systems is the
ability to withstand harsh environments while maintaining reliable and
efficient
operation. Exposures to low temperature as well as high temperature
constitute
such stressed. Applications where low temperatures are encountered
include
deep space missions, medical imaging equipment, and cryogenic
instrumentation. Efforts were taken to design and develop power
capacitors capable of wide temperature operation. In this work, ceramic
and film power capacitors were developed and characterized as a
function of temperature from 20° C to -185° C in term of their
dielectric properties. These properties included capacitance stability
and dielectric loss in thee frequency range of 50 Hz to 100 kHz. DC
leakage current measurements were also performed on the capacitors. The
manuscript presents the results that indicate good operational
characteristic behavior and stability of the components tested at low
temperatures.
Power Control Electronics for Cryogenic
Instrumentation
In order to achieve a high-efficiency high-density cryogenic
instrumentation system, the power processing electronics should be
placed in the cold environment along with the sensors and
signal-processing electronics. The typical instrumentation system
requires low voltage dc usually obtained from processing line frequency
ac power. Switch-mode power conservation topologies such as forward,
flyback, push-pull, and half-bridge are used for high-efficiency power
processing using pulse-width modulation (PWM) or resonant control. This
paper presents several PWM and multi-resonant power control circuits,
implemented using commercially
available CMOS and BiCMOS integrated circuits, and their performance at
liquid-nitrogen
temperature (77° K) as compared to their room temperature (300° K)
performance.
The operation of integrated circuits at cryogenic temperatures results
in
an improved performance in terms of increased speed, reduced latch-up
susceptibility,
reduced leakage current, and reduced thermal noise. However, the
switching
noise increased at 77° K compared to 300° K. The power control circuits
tested
in the laboratory did successfully restart at 77° K.
Operation of a High Voltage DC-DC
Converter
at Cryogenic Temperatures
A 1 kW 80V/550V phase-shifted full-bridge dc-dc converter, based on a
beam supply for the power processing unit of a space electric
propulsion
system, was successfully operated at cryogenic temperatures. The
converters
were designed to operate from room temperature to -184° C using
commercially
available components. However, specific attention must be made in the
selection
of the components used for operation at cryogenic temperatures. In
particular,
most bipolar devices must be avoided and CMOS type devices used. MOSFET
switches
work quite well at low temperature, but their reverse breakdown voltage
must
be derated. Also, only certain types of capacitors, resistors, and
magnetics have characteristics that are desirable at low temperature.
The phase-shifted full-bridge dc-dc converter was tested under three
load conditions: 550V
output at » 1000 watts, 550V output at » 525 watts, and 275V output at
»
250 watts. The overall efficiency of the converter increased as the
temperature decreased, and little change occurred in the behavior of
the main switching waveforms. In addition, several key components were
characterized at room temperature and liquid nitrogen (LN2) temperature
(-196° C).
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 impendence 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.
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