[Milsurplus] Dynaverters

[gl4d21a at juno.com]

As a survivor of that wonderful era in equipment design, maybe I can factually address some of the aspects of those early switching power converters.  Germanium devices had both positive and negative attributes which entered into the design.  Since they were slow switchers, they were relatively clean at RF, and often improved system performance when they replaced vibrator supplies in receivers.  Also, the on voltage drop was about half of what silicon exhibited (before the current crop of FETs), producing a more efficient design for 6 or 12 volts.  At 28 volts, the difference was less noticable.

On the other side of the coin, was the thermal management problem, and germaniun's tendency to run away, and develop leakage problems.  The operating frequency was a trade-off among several variables, some of which I have forgotten.  Transformer core design was a major factor, as was switching time of the devices.  The later tape wound transformers tended to be pretty quiet acoustically, even at 200 watt power levels, and unless the screws were loose, the wiring and transistors didn't produce nmuch acoustic energy.  Some unfortunates made some of the hardware mechanically resonant at the switching frequency, and that was always difficult to clean up.  Modern designs using ultrasonic frequencies, fast IGFETs and Shottkey rectifiers are quiet, efficient and require special toroids for the transformers.

73,
George
W5VPQ

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