Malik E. Elbuluk

University of Akron, Akron, Ohio

Ahmad Hammoud

QSS Group, Inc., Cleveland, Ohio

Scott S. Gerber

ZIN Technologies, Inc., Brook Park, Ohio

Richard Patterson

Glenn Research Center, Cleveland, Ohio

Cryogenic Evaluation of an Advanced DC/DC

Converter Module for Deep Space Applications

NASA/TM—2003-212085

January 2003
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Malik E. Elbuluk

University of Akron, Akron, Ohio

Ahmad Hammoud

QSS Group, Inc., Cleveland, Ohio

Scott S. Gerber

ZIN Technologies, Inc., Brook Park, Ohio

Richard Patterson

Glenn Research Center, Cleveland, Ohio

Cryogenic Evaluation of an Advanced DC/DC

Converter Module for Deep Space Applications

NASA/TM—2003-212085

January 2003

National Aeronautics and

Space Administration

Glenn Research Center

Prepared for the

37th Industry Application Society Annual Meeting

cosponsored by the Institute of Electrical and Electronics Engineers

and the Instrument Society of America

Pittsburgh, Pennsylvania, October 13–17, 2002
Acknowledgments

This work is supported by the NASA Glenn Research Center, GESS Contract number NAS3–00145.

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Available electronically at http://gltrs.grc.nasa.gov
NASA/TMó2003-212085 1 

Cryogenic Evaluation of an Advanced DC/DC Converter Module 

for Deep Space Applications 

Malik E. Elbuluk 

University of Akron 

Akron, Ohio 44325 

Phone: 330ñ972ñ6531 

E-mail: melbuluk@uakron.edu

 Scott S. Gerber 

ZIN Technologies 

Brook Park, Ohio 44142 

Phone: 216ñ433ñ5226 

E-mail: scott.s.gerber@grc.nasa.gov

Ahmad Hammoud 

QSS Group, Inc. 

Cleveland, Ohio 44135 

Phone: 216ñ433ñ8511 

E-mail: Ahmad.hammoud@grc.nasa.gov

Richard Patterson 

NASA Glenn Research Center 

Cleveland, Ohio 44135 

Phone: 216ñ433ñ8166 

E-mail: richard.patterson@grc.nasa.gov

Abstract- 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 to ñ140 °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. 

I. INTRODUCTION

In many future space missions, such as outer 

planetary exploration and deep space probes, electrical 

and electronic power components and systems must 

operate reliably and efficiently in very low 

temperature environments. For example, an interplanetary probe launched to explore the rings of 

Saturn would experience an average temperature of 

about ñ183 °C. Presently, spacecraft operating in the 

cold environment of deep space carry on-board a large 

number of radioisotope heating units to maintain an 

operating temperature for the electronics of 

approximately 20 °C. This is not an ideal solution 

because the radioisotope units are always producing 

heat, even when the spacecraft is already too hot, thus 

requiring an active thermal control system for the 

spacecraft. Electronics capable of operation at 

cryogenic temperatures will not only tolerate the 

hostile environment of deep space but also reduce 

system size and weight by eliminating the heating 

radioisotope units and associated structures thereby; 

reducing system development and launch costs, 

improving reliability and lifetime, and increasing 

energy densities. 

The Low Temperature Electronics Program at the 

NASA Glenn Research Center (GRC) focuses on research 

and development of electrical components and systems 

suitable for applications in deep space missions. Research 

is being conducted on components and systems for use 

down to cryogenic temperature (ñ196 °C). These include 

commercially available semiconductor switching devices, 

resistors, magnetic components, capacitors, integrated 

circuits and DC/DC converter modules. Also, a number of 

DC/DC converters have been built and characterized inhouse at low temperatures. The converters were designed 

or modified to operate from room temperature to 

ñ196 °C using commercially available components. These 

systems had output power range from 5 W to 1 kW with 

switching frequencies of 50 to 200 kHz. [1ñ14]. 

In this work, an advanced commercial-off-theshelf modular DC/DC converter has been investigated 

for low temperature operation. The converter has a 

high power density (30 W/in3

) and has been spacequalified in terms of radiation tolerance. It is a singleended forward converter with a constant switching 

frequency of 550 kHz. It has a wide input voltage 

range of 16 to 40 V, an output voltage of 3.3 V and a 

power rating of 10 W. Its operating temperature range 

is specified between ñ55 °C to 125 °C. The module 

was investigated in terms of its steady state output 

voltage regulation, efficiency, terminal current ripple 

characteristics, and dynamic response of the output 

voltage to a step change in load. These properties, 

which were determined in the temperature range of 

20 to ñ140 °C, were obtained at various load levels 

and at different input voltages. The experimental 

procedures along with the experimental data obtained 

on the investigated converter are presented and 

discussed. 
NASA/TMó2003-212085 2 

II. EXPERIMENTAL SETUP AND PROCEDURES

 The tests on the converter were performed using 

an environmental chamber utilizing liquid nitrogen as 

the coolant. A temperature rate of change of 

10 °C/min was used throughout this work. The 

module was investigated in the temperature range of 

20 to ñ140 °C at a decrement of 20 °C. At a given 

temperature, these properties were obtained at various 

input voltages and at different load levels from 

no-load to full-load conditions. At every test 

temperature, the test article was allowed to soak at that 

temperature for a period of 30 minutes before any 

measurements were made. After the last measurement 

was taken at the lowest temperature, the converter was 

allowed to stabilize to room temperature, and then the 

measurements were repeated at room temperature to 

determine the effect of thermal cycling on the 

converterís performance. 

III. RESULTS AND DISCUSSIONS

The converter was evaluated under steady state and 

dynamic conditions. In the steady state, the converter 

output voltage regulation, efficiency, and input and 

output current distortions were investigated. At a 

given temperature, these properties were obtained at 

various input voltages and at different load levels, 

from no-load to full-load conditions. 

The dynamic characteristics of the converter were 

obtained by monitoring the transient response of the 

output voltage due to a step change in the load. Two 

responses were recorded, one from no load to full load 

and the other from full load to no load. 

A. Steady State Performance

The output voltage and efficiency of the converter 

at various input voltage and load levels as a function 

of temperature are shown in Figures 1 through 4. 

These parameters are obtained utilizing input voltages 

of 16, 24, 32, and 42 V for loads of 0.5, 1.0, 1.5, 2.0, 

and 2.5 A. The converter exhibited good voltage 

regulation with temperature down to ñ100 °C. This 

trend is maintained regardless of the load level to 

which the converter is subjected. Below ñ100 °C, 

however, the converter started to display inconsistent 

behavior in its voltage regulation, particularly with an 

applied input voltage of 16 V. At this voltage level, 

the efficiency of the converter tends to slightly 

decrease with a decrease in test temperature down to 

ñ100 °C, as shown in Figure 1. This decrease becomes 

more significant at temperatures below ñ100 °C. At 

any given test temperature, the efficiency increased as 

the load was increased. At temperatures below 

ñ100 °C, the efficiency is at minimum as the converter 

exhibits some loss in output regulation. 

At input voltage higher than 16 V, the converter 

displayed better stability in its voltage regulation 

throughout the entire test temperature range from 

20 to ñ140 °C, as shown in Figures 2 to 4. Such is the 

case at any load level investigated between 0.5 and 

2.5 A. The efficiency of the converter, displayed 

similar behavior to that observed under 16 V input 

between 20 and ñ100 °C. Once again, the efficiency, 

at a given test temperature, has the highest value when 

the maximum loading level was applied to the 

converter. 

Waveforms of the converter output voltage ripple, 

the output current ripple, and the input current ripple 

at room temperature (25 °C) and at a low temperature 

(ñ100 °C) are shown in Figures 5 and 6 for light load 

and heavy load, respectively. Theses waveforms were 

obtained using an input voltage of 16 V. No effect of 

temperature can be observed as no significant 

variations occur in these waveforms. 

Figures 7 and 8 show the same waveforms both at 

room temperature (25 °C) and at the low temperature 

(ñ100 °C) for high input voltage of 40 V. Once again, 

these properties do not undergo much change in their 

waveforms due to the temperature variation from 20 to 

ñ100 °C, regardless of the applied load. The level of 

the applied input, however, seems to influence these 

properties as evident from the increase in the 

frequency as well as the amplitude of the ripples as 

higher voltages are applied. 

B. Dynamic Performance 

The dynamic response for the converter, 

represented by output voltage response to a step 

change in the load current, is shown in Figures 9 and 

10. The step change from full load to no load 

exhibited different dynamic response compared to that 

of a step change from no load to full load. The 

different responses are a clear indication of the 

nonlinear behavior of the module and may also reflect 

the effect of low temperature on the components and 

devices in the converter. 

IV. CONCLUSIONS

An advanced radiation-hardened DC/DC converter 

was characterized in terms of its performance as a 

function of temperature in the range of 20 to ñ140 °C. 

The converter was evaluated with respect to its steady 

state output voltage regulation, efficiency, output 

voltage ripple; input current ripple and output current 

ripple at various input voltage levels and loads. In 

general, this converter displayed good performance in 

regulation, efficiency and dynamic characteristics with 
NASA/TMó2003-212085 3 

temperature down to ñ100 °C. Some instability is 

observed as the temperature is decreased further. More 

testing under long-term thermal exposure is needed to 

fully characterize this converter for potential 

application in low temperature environments. 

V. REFERENCES

1. Ray, B., Gerber, S.S., Patterson, R. and Myers, I., 

ìPower Control Electronics for Cryogenic 

Instrumentation,î Advances in Inst. and Control, Vol. 

50, Part 1, Int. Soc. for Measurement and Control, 

1995, pp. 131-139. 

2. Patterson, R.L., Dickman, J.E., Hammoud, A. and 

Gerber S.S., ìLow Temperature Power Electronics 

Program,î NASA EEE Links, Electronic Packaging 

and Space Parts News, Vol. 4, No. 1, January 1998. 

3. Patterson, R.L., Hammoud, A. and Gerber, S.S., 

ìEvaluation of Capacitors at Cryogenic Temperatures 

for Space Applications,î IEEE International 

Conference on Electrical Insulation, Washington DC, 

June 7-10, 1998. 

4. Ray, B., Gerber, S., Patterson, R. and Myers, I., ì77K 

Operation of a Multi-Resonant Power Converter,î 

IEEE PESC, Record, Vol. 1, 1995, pp. 55-60. 

5. Ray, B., Gerber, S.S., Patterson, R.L. and Myers, I.T., 

ìLiquid Nitrogen Temperature Operation of a 

Switching Power Converter,î Symp. on Low Temp. 

Electronics & High Temperature Superconductivity, 

Electrochemical Society, Vol. 9, 1995, pp. 345-352. 

6. Ray, B., Gerber, S.S., Patterson, R.L. and Dickman, J., 

ìLow Temperature Performance of a Boost Converter 

with MPP and HTS Inductor,î IEEE APEC 96 

Conference, Vol. 2, 1996, pp. 883-888. 

7. Gerber, S.S., Patterson, R.L., Ray, B. and Stell, C., 

ìPerformance of a Spacecraft DC-DC Converter 

Breadboard Modified for Low Temperature Operation,î 

IECEC 96, Vol. 1, 1996, pp. 592-598. 

8. Ray, B., Gerber, S.S. and Patterson, R.L., ìLow 

Temperature Performance of a Full-Bridge DC-DC 

Converter,î IECEC ë96, Vol. 1, 1996, pp. 553-559. 

9. Gerber, S.S. Miller, T., Patterson, R.L. and Hammoud, 

A., ìPerformance of a Closed-Loop Controlled High 

Voltage DC/DC Converter at Cryogenic Temperature,î 

IECEC ë98, Vol. 1, 1998. 

10. M. Elbuluk, S. Gerber, A. Hammoud and R. Patterson, 

ìEvaluation of Low Power DC/DC Converter Modules at 

Low Temperatures,î Proceedings of IEEE PESCí00, 

Galway, Ireland. 

11. Elbuluk, S. Gerber, A. Hammoud and R. Patterson, 

ìEfficiency and Regulation of Low Power DC/DC 

Converter Modules at Cryogenic Temperatures,î 

Proceedings of IEEE IECECí00, Las Vegas. 

12. M. Elbuluk, S. Gerber, A. Hammoud and R. Patterson, 

ìCharacterization of Low Power DC/DC Converter 

Modules at Low Temperatures,î Proceedings of IEEE 

IASí00, Rome, Italy. 

13. S. Gerber, A. Hammoud, M. Elbuluk, R. Patterson, R. 

Ghaffarian, R. Ramesham and S. Agarwal, ìLow 

Temperature Testing of a Radiation Hardened CMOS 8-

Bit Flash Analog-to-Digital (A/D) Converter,î 36th

Intersociety Energy Conversion Engineering Conference 

(IECEC), Savannah, Georgia, July 29-Aug 2, 2001. 

14. M. Elbuluk, S. Gerber, A. Hammoud, and R. Patterson, 

ìPerformance of High-Speed PWM Control Chips at 

Cryogenic Temperatures,î Proceedings of IEEE IASí01, 

Chicago, October 2001. 

-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (°C)

0.8

0.9

1.0

1.1

Normalized Output Voltage

-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (°C)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Normalized Efficiency

IOUT

0.5A

1.0A

1.5A

2.0A

2.5A

Figure 1. Output voltage and efficiency versus temperature at various loads and input voltage of 16 V. 
NASA/TMó2003-212085 4 

-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (°C)

0.8

0.9

1.0

1.1

Normalized Output Voltage

-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (°C)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Normalized Efficiency

IOUT

0.5A

1.0A

1.5A

2.0A

2.5A

Figure 2. Output voltage and efficiency versus temperature at various loads and input voltage of 24 V. 

-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (°C)

0.8

0.9

1.0

1.1

Normalized Output Voltage

-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (°C)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Normalized Efficiency

IOUT

0.5A

1.0A

1.5A

2.0A

2.5A

Figure 3. Output voltage and efficiency versus temperature at various loads and input voltage of 32 V. 

-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (°C)

0.8

0.9

1.0

1.1

Normalized Output Voltage

-200 -180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40

Temperature (°C)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Normalized Efficiency

IOUT

0.5A

1.0A

1.5A

2.0A

2.5A

Figure 4. Output voltage and efficiency versus temperature at various loads and input voltage of 40 V. 
NASA/TMó2003-212085 5 

Time (2 μs/div)

(b) -100 °C

V OUT

(1 V/div)

I OUT Ripple

(20 mA/div)

I IN Ripple

(20 mA/div)

Time (2 μs/div)

(a) 25 °C

V OUT

(1 V/div)

I OUT Ripple

(20 mA/div)

I IN Ripple

(20 mA/div)

Figure 5. The converter ripple characteristics at low input voltage (16 V) and under light load (1.0 A). 

Time (2 μs/div)

(b) -100 °C

V OUT

(1 V/div)

I OUT Ripple

(20 mA/div)

I IN Ripple

(20 mA/div)

Time (2 μs/div)

(a) 25 °C

V OUT

(1 V/div)

I OUT Ripple

(20 mA/div)

I IN Ripple

(20 mA/div)

Figure 6. The converter ripple characteristics at low input voltage (16 V) and under heavy load (2.5 A). 
NASA/TMó2003-212085 6 

Time (2 μs/div)

(b) -100 °C

V OUT

(1 V/div)

I OUT Ripple

(20 mA/div)

I IN Ripple

(20 mA/div)

Time (2 μs/div)

(a) 25 °C

V OUT

(1 V/div)

I OUT Ripple

(20 mA/div)

I IN Ripple

(20 mA/div)

Figure 7. The converter ripple characteristics at high input voltage (40 V) and under light load (1.0 A). 

Time (2 μs/div)

(b) -100 °C

V OUT

(1 V/div)

I OUT Ripple

(20 mA/div)

I IN Ripple

(20 mA/div)

Time (2 μs/div)

(a) 25 °C

V OUT

(1 V/div)

I OUT Ripple

(20 mA/div)

I IN Ripple

(20 mA/div)

Figure 8. The converter ripple characteristics at high input voltage (40 V) and under heavy load (2.5 A). 
NASA/TMó2003-212085 7 

Time (250 μs/div)

(b) -100 °C

V OUT

(1 V/div)

I OUT

(0.5 A/div)

Time (250 μs/div)

(a) 25 °C

V OUT

(1 V/div)

I OUT

(0.5 A/div)

Figure 9. The converter dynamic response to a step change from no-load to full-load at an input voltage of 16 V. 

Time (250 μs/div)

(b) -100 °C

V OUT

(1 V/div)

I OUT

(0.5 A/div)

Time (250 μs/div)

(a) 25 °C

V OUT

(1 V/div)

I OUT

(0.5 A/div)

Figure 10. The converter dynamic response to a step change from full-load to no-load at an input voltage of 16 V. 
This publication is available from the NASA Center for AeroSpace Information, 301–621–0390.

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NASA TM—2003-212085

E–13738

WBS–22–297–60–05

13

Cryogenic Evaluation of an Advanced DC/DC Converter Module for Deep

Space Applications

Malik E. Elbuluk, Ahmad Hammoud, Scott S. Gerber, and Richard Patterson

DC/DC converter; Cryogenics; Power supplies; Deep space

Unclassified -Unlimited

Subject Category: 33 Distribution: Nonstandard

Prepared for the 37th Industry Application Society Annual Meeting cosponsored by the Institute of Electrical and

Electronics Engineers and the Instrument Society of America, Pittsburgh, Pennsylvania, October 13–17, 2002. Malik E.

Elbuluk, University of Akron, Akron, Ohio 44325; Ahmad Hammoud, QSS Group, Inc., Cleveland, Ohio 44135;

Scott S. Gerber, ZIN Technologies, Inc., Brook Park, Ohio 44142; Richard Patterson, NASA Glenn Research Center.

Responsible person, Malik E. Elbuluk, organization code 5480, 216–433–8189.

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 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.