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

A 1OW 3OV/5.OV 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 (greater than -196 C) was a variety of performance problems such as 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 to the converter which improved low temperature performance even further.